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Chin CG, Chen YC, Lin FJ, Lin YK, Lu YY, Cheng TY, Chen SA, Chen YJ. Targeting NLRP3 signaling reduces myocarditis-induced arrhythmogenesis and cardiac remodeling. J Biomed Sci 2024; 31:42. [PMID: 38650023 PMCID: PMC11034044 DOI: 10.1186/s12929-024-01032-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Accepted: 04/14/2024] [Indexed: 04/25/2024] Open
Abstract
BACKGROUND Myocarditis substantially increases the risk of ventricular arrhythmia. Approximately 30% of all ventricular arrhythmia cases in patients with myocarditis originate from the right ventricular outflow tract (RVOT). However, the role of NLRP3 signaling in RVOT arrhythmogenesis remains unclear. METHODS Rats with myosin peptide-induced myocarditis (experimental group) were treated with an NLRP3 inhibitor (MCC950; 10 mg/kg, daily for 14 days) or left untreated. Then, they were subjected to electrocardiography and echocardiography. Ventricular tissue samples were collected from each rat's RVOT, right ventricular apex (RVA), and left ventricle (LV) and examined through conventional microelectrode and histopathologic analyses. In addition, whole-cell patch-clamp recording, confocal fluorescence microscopy, and Western blotting were performed to evaluate ionic currents, intracellular Ca2+ transients, and Ca2+-modulated protein expression in individual myocytes isolated from the RVOTs. RESULTS The LV ejection fraction was lower and premature ventricular contraction frequency was higher in the experimental group than in the control group (rats not exposed to myosin peptide). Myocarditis increased the infiltration of inflammatory cells into cardiac tissue and upregulated the expression of NLRP3; these observations were more prominent in the RVOT and RVA than in the LV. Furthermore, experimental rats treated with MCC950 (treatment group) improved their LV ejection fraction and reduced the frequency of premature ventricular contraction. Histopathological analysis revealed higher incidence of abnormal automaticity and pacing-induced ventricular tachycardia in the RVOTs of the experimental group than in those of the control and treatment groups. However, the incidences of these conditions in the RVA and LV were similar across the groups. The RVOT myocytes of the experimental group exhibited lower Ca2+ levels in the sarcoplasmic reticulum, smaller intracellular Ca2+ transients, lower L-type Ca2+ currents, larger late Na+ currents, larger Na+-Ca2+ exchanger currents, higher reactive oxygen species levels, and higher Ca2+/calmodulin-dependent protein kinase II levels than did those of the control and treatment groups. CONCLUSION Myocarditis may increase the rate of RVOT arrhythmogenesis, possibly through electrical and structural remodeling. These changes may be mitigated by inhibiting NLRP3 signaling.
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Affiliation(s)
- Chye-Gen Chin
- Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, 250 Wu-Hsing Street, Taipei, 11031, Taiwan
- Division of Cardiovascular Medicine, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
| | - Yao-Chang Chen
- Department of Biomedical Engineering, National Defense Medical Center, Taipei, Taiwan
| | - Fong-Jhih Lin
- Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, 250 Wu-Hsing Street, Taipei, 11031, Taiwan
- Department of Biomedical Engineering, National Defense Medical Center, Taipei, Taiwan
| | - Yung-Kuo Lin
- Division of Cardiovascular Medicine, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
- Division of Cardiology, Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Yen-Yu Lu
- Division of Cardiology, Department of Internal Medicine, Sijhih Cathay General Hospital, New Taipei City, Taiwan
| | - Tzu-Yu Cheng
- Division of Cardiology, Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
- Division of Cardiovascular Surgery, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
| | - Shih-Ann Chen
- Heart Rhythm Center and Division of Cardiology, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
- Division of Cardiology, Taichung Veterans General Hospital, Taichung, Taiwan
| | - Yi-Jen Chen
- Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, 250 Wu-Hsing Street, Taipei, 11031, Taiwan.
- Division of Cardiovascular Medicine, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
- Cardiovascular Research Center, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
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Blair GA, Wu X, Bain C, Warren M, Hoeker GS, Poelzing S. Mannitol and hyponatremia regulate cardiac ventricular conduction in the context of sodium channel loss of function. Am J Physiol Heart Circ Physiol 2024; 326:H724-H734. [PMID: 38214908 PMCID: PMC11221810 DOI: 10.1152/ajpheart.00211.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 01/04/2024] [Accepted: 01/09/2024] [Indexed: 01/13/2024]
Abstract
Scn5a heterozygous null (Scn5a+/-) mice have historically been used to investigate arrhythmogenic mechanisms of diseases such as Brugada syndrome (BrS) and Lev's disease. Previously, we demonstrated that reducing ephaptic coupling (EpC) in ex vivo hearts exacerbates pharmacological voltage-gated sodium channel (Nav)1.5 loss of function (LOF). Whether this effect is consistent in a genetic Nav1.5 LOF model is yet to be determined. We hypothesized that loss of EpC would result in greater reduction in conduction velocity (CV) for the Scn5a+/- mouse relative to wild type (WT). In vivo ECGs and ex vivo optical maps were recorded from Langendorff-perfused Scn5a+/- and WT mouse hearts. EpC was reduced with perfusion of a hyponatremic solution, the clinically relevant osmotic agent mannitol, or a combination of the two. Neither in vivo QRS duration nor ex vivo CV during normonatremia was significantly different between the two genotypes. In agreement with our hypothesis, we found that hyponatremia severely slowed CV and disrupted conduction for 4/5 Scn5a+/- mice, but 0/6 WT mice. In addition, treatment with mannitol slowed CV to a greater extent in Scn5a+/- relative to WT hearts. Unexpectedly, treatment with mannitol during hyponatremia did not further slow CV in either genotype, but resolved the disrupted conduction observed in Scn5a+/- hearts. Similar results in guinea pig hearts suggest the effects of mannitol and hyponatremia are not species specific. In conclusion, loss of EpC through either hyponatremia or mannitol alone results in slowed or disrupted conduction in a genetic model of Nav1.5 LOF. However, the combination of these interventions attenuates conduction slowing.NEW & NOTEWORTHY Cardiac sodium channel loss of function (LOF) diseases such as Brugada syndrome (BrS) are often concealed. We optically mapped mouse hearts with reduced sodium channel expression (Scn5a+/-) to evaluate whether reduced ephaptic coupling (EpC) can unmask conduction deficits. Data suggest that conduction deficits in the Scn5a+/- mouse may be unmasked by treatment with hyponatremia and perinexal widening via mannitol. These data support further investigation of hyponatremia and mannitol as novel diagnostics for sodium channel loss of function diseases.
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Affiliation(s)
- Grace A Blair
- Graduate Program in Translational Biology, Medicine, and Health, Virginia Polytechnic Institute and State University, Roanoke, Virginia, United States
- Center for Vascular and Heart Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
| | - Xiaobo Wu
- Center for Vascular and Heart Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
| | - Chandra Bain
- Center for Vascular and Heart Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
| | - Mark Warren
- Center for Vascular and Heart Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
| | - Gregory S Hoeker
- Center for Vascular and Heart Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
| | - Steven Poelzing
- Graduate Program in Translational Biology, Medicine, and Health, Virginia Polytechnic Institute and State University, Roanoke, Virginia, United States
- Center for Vascular and Heart Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia, United States
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, United States
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3
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Jin G, Li S, Wang Y, Pu J. Case report: Cardiac arrest after radiofrequency ablation in a 76-year-old male. Medicine (Baltimore) 2024; 103:e37191. [PMID: 38394505 DOI: 10.1097/md.0000000000037191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/25/2024] Open
Abstract
RATIONALE Previous studies have found that the main treatment of sinus arrest is pacemaker treatment. It is rare to have 12 s of sinus arrest after radiofrequency ablation, and whether a permanent pacemaker is implanted immediately in this case is not described in the guidelines. PATIENT CONCERNS A 76-year-old male patient with persistent atrial fibrillation (AF) developed sinus arrest lasting 12 s in the early morning of the fourth day after using radiofrequency ablation for pulmonary vein isolation. DIAGNOSIS The patient was diagnosed with AF and sinus arrest. INTERVENTIONS The patient received cardiopulmonary resuscitation, intravenous injection of atropine 1 mg, and intravenous infusion of isoproterenol 1mg and immediately recovered consciousness thereafter. Approximately, 1.5 h later, the patient underwent surgery to install a temporary pacemaker in the right femoral vein. OUTCOMES The patient had repeated episodes of sinus arrest after the implantation of a temporary pacemaker. After 3 weeks, the patient stabilized and was discharged. The patient was followed up for 1 year and did not experience any recurrence of sinus arrest or AF. LESSONS We consider the potential for postoperative myocardial edema, injury to the sinoatrial node during the procedure, propafenone poisoning, and autonomic dysfunction as contributors to the occurrence of sinus arrest after radiofrequency ablation. When sinus arrest occurs after radiofrequency ablation, we can choose the appropriate treatment according to the patient's condition.
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Affiliation(s)
- Geya Jin
- North China University of Science and Technology, Tangshan, China
| | - Shuyu Li
- Tangshan Workers' Hospital, Tangshan, China
| | - Yafeng Wang
- North China University of Science and Technology, Tangshan, China
| | - Jianyi Pu
- Affiliated Hospital of North China University of Science and Technology, Tangshan, China
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Kiseleva DG, Kirichenko TV, Markina YV, Cherednichenko VR, Gugueva EA, Markin AM. Mechanisms of Myocardial Edema Development in CVD Pathophysiology. Biomedicines 2024; 12:465. [PMID: 38398066 PMCID: PMC10887157 DOI: 10.3390/biomedicines12020465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 02/16/2024] [Accepted: 02/18/2024] [Indexed: 02/25/2024] Open
Abstract
Myocardial edema is the excess accumulation of fluid in the myocardial interstitium or cardiac cells that develops due to changes in capillary permeability, loss of glycocalyx charge, imbalance in lymphatic drainage, or a combination of these factors. Today it is believed that this condition is not only a complication of cardiovascular diseases, but in itself causes aggravation of the disease and increases the risks of adverse outcomes. The study of molecular, genetic, and mechanical changes in the myocardium during edema may contribute to the development of new approaches to the diagnosis and treatment of this condition. This review was conducted to describe the main mechanisms of myocardial edema development at the molecular and cellular levels and to identify promising targets for the regulation of this condition based on articles cited in Pubmed up to January 2024.
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Affiliation(s)
- Diana G. Kiseleva
- Department of Biophysics, Faculty of Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
- Laboratory of Cellular and Molecular Pathology of Cardiovascular System, Petrovsky National Research Centre of Surgery, 119991 Moscow, Russia (V.R.C.)
| | - Tatiana V. Kirichenko
- Laboratory of Cellular and Molecular Pathology of Cardiovascular System, Petrovsky National Research Centre of Surgery, 119991 Moscow, Russia (V.R.C.)
- Chazov National Medical Research Center of Cardiology, Ac. Chazov Str. 15A, 121552 Moscow, Russia
| | - Yuliya V. Markina
- Laboratory of Cellular and Molecular Pathology of Cardiovascular System, Petrovsky National Research Centre of Surgery, 119991 Moscow, Russia (V.R.C.)
| | - Vadim R. Cherednichenko
- Laboratory of Cellular and Molecular Pathology of Cardiovascular System, Petrovsky National Research Centre of Surgery, 119991 Moscow, Russia (V.R.C.)
| | - Ekaterina A. Gugueva
- N.V. Sklifosovsky Institute of Clinical Medicine, I.M. Sechenov First Moscow State Medical University, 119435 Moscow, Russia;
| | - Alexander M. Markin
- Laboratory of Cellular and Molecular Pathology of Cardiovascular System, Petrovsky National Research Centre of Surgery, 119991 Moscow, Russia (V.R.C.)
- Medical Institute, Peoples’ Friendship University of Russia Named after Patrice Lumumba (RUDN University), 117198 Moscow, Russia
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Struckman HL, Moise N, King DR, Soltisz A, Buxton A, Dunlap I, Chen Z, Radwański PB, Weinberg SH, Veeraraghavan R. Unraveling Impacts of Chamber-Specific Differences in Intercalated Disc Ultrastructure and Molecular Organization on Cardiac Conduction. JACC Clin Electrophysiol 2023; 9:2425-2443. [PMID: 37498248 PMCID: PMC11102000 DOI: 10.1016/j.jacep.2023.05.042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 05/26/2023] [Accepted: 05/30/2023] [Indexed: 07/28/2023]
Abstract
BACKGROUND Propagation of action potentials through the heart coordinates the heartbeat. Thus, intercalated discs, specialized cell-cell contact sites that provide electrical and mechanical coupling between cardiomyocytes, are an important target for study. Impaired propagation leads to arrhythmias in many pathologies, where intercalated disc remodeling is a common finding, hence the importance and urgency of understanding propagation dependence on intercalated disc structure. Conventional modeling approaches cannot predict changes in propagation elicited by perturbations that alter intercalated disc ultrastructure or molecular organization, because of lack of quantitative structural data at subcellular through nano scales. OBJECTIVES This study sought to quantify intercalated disc structure at these spatial scales in the healthy adult mouse heart and relate them to chamber-specific properties of propagation as a precursor to understanding the effects of pathological intercalated disc remodeling. METHODS Using super-resolution light microscopy, electron microscopy, and computational image analysis, we provide here the first ever systematic, multiscale quantification of intercalated disc ultrastructure and molecular organization. RESULTS By incorporating these data into a rule-based model of cardiac tissue with realistic intercalated disc structure, and comparing model predictions of electrical propagation with experimental measures of conduction velocity, we reveal that atrial intercalated discs can support faster conduction than their ventricular counterparts, which is normally masked by interchamber differences in myocyte geometry. Further, we identify key ultrastructural and molecular organization features underpinning the ability of atrial intercalated discs to support faster conduction. CONCLUSIONS These data provide the first stepping stone to elucidating chamber-specific effects of pathological intercalated disc remodeling, as occurs in many arrhythmic diseases.
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Affiliation(s)
- Heather L Struckman
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, Ohio, USA; The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Nicolae Moise
- The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - D Ryan King
- The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Andrew Soltisz
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, Ohio, USA; The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Andrew Buxton
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, Ohio, USA
| | - Izabella Dunlap
- The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Zhenhui Chen
- Krannert Cardiovascular Research Center, Department of Medicine, Indiana University, Indianapolis, Indiana, USA
| | - Przemysław B Radwański
- The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA; Division of Outcomes and Translational Sciences, College of Pharmacy, The Ohio State University, Columbus, Ohio, USA
| | - Seth H Weinberg
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, Ohio, USA; The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Rengasayee Veeraraghavan
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, Ohio, USA; The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA.
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Mezache L, Soltisz AM, Johnstone SR, Isakson BE, Veeraraghavan R. Vascular Endothelial Barrier Protection Prevents Atrial Fibrillation by Preserving Cardiac Nanostructure. JACC Clin Electrophysiol 2023; 9:2444-2458. [PMID: 38032579 PMCID: PMC11134328 DOI: 10.1016/j.jacep.2023.10.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 10/20/2023] [Accepted: 10/21/2023] [Indexed: 12/01/2023]
Abstract
BACKGROUND Atrial fibrillation (AF), the most common cardiac arrhythmia, is widely associated with inflammation, vascular dysfunction, and elevated levels of the vascular leak-inducing cytokine, vascular endothelial growth factor (VEGF). Mechanisms underlying AF are poorly understood and current treatments only manage this progressive disease, rather than arresting the underlying pathology. The authors previously identified edema-induced disruption of sodium channel (NaV1.5)-rich intercalated disk nanodomains as a novel mechanism for AF initiation secondary to acute inflammation. Therefore, we hypothesized that protecting the vascular barrier can prevent vascular leak-induced atrial arrhythmias. OBJECTIVES In this study the authors tested the hypothesis that protecting the vascular barrier can prevent vascular leak-induced atrial arrhythmias. They identified 2 molecular targets for vascular barrier protection, connexin43 (Cx43) hemichannels and pannexin-1 (Panx1) channels, which have been implicated in cytokine-induced vascular leak. METHODS The authors undertook in vivo electrocardiography, electron microscopy, and super-resolution light microscopy studies in mice acutely treated with a clinically relevant level of VEGF. RESULTS AF incidence was increased in untreated mice exposed to VEGF relative to vehicle control subjects. VEGF also increased the average number of AF episodes. VEGF shifted NaV1.5 signal to longer distances from Cx43 gap junctions, measured by a distance transformation-based spatial analysis of 3-dimensional confocal images of intercalated disks. Similar effects were observed with NaV1.5 localized near mechanical junctions composed of neural cadherin. Blocking connexin43 hemichannels (αCT11 peptide) or Panx1 channels (PxIL2P peptide) significantly reduced the duration of AF episodes compared with VEGF alone with no treatment. Concurrently, both peptide therapies preserved NaV1.5 distance from gap junctions to control levels and reduced mechanical junction-adjacent intermembrane distance in these hearts. Notably, similar antiarrhythmic efficacy was also achieved with clinically-relevant small-molecule inhibitors of Cx43 and Panx1. CONCLUSIONS These results highlight vascular barrier protection as an antiarrhythmic strategy following inflammation-induced vascular leak.
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Affiliation(s)
- Louisa Mezache
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, Ohio, USA
| | - Andrew M Soltisz
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, Ohio, USA
| | - Scott R Johnstone
- Fralin Biomedical Research Institute at VTC, Centre for Vascular and Heart Research, Virginia Tech, Roanoke, Virginia, USA; Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA; Virginia Tech Carilion School of Medicine, Department of Surgery, Roanoke, Virginia, USA
| | - Brant E Isakson
- Department of Molecular Physiology and Biological Physics, School of Medicine, University of Virginia, Charlottesville, Virginia, USA; Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia, USA
| | - Rengasayee Veeraraghavan
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, Ohio, USA; The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA; Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, Ohio, USA.
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Zhang Y, Wu X, Vadlamani RA, Lim Y, Kim J, David K, Gilbert E, Li Y, Wang R, Jiang S, Wang A, Sontheimer H, English DF, Emori S, Davalos RV, Poelzing S, Jia X. Submillimeter Multifunctional Ferromagnetic Fiber Robots for Navigation, Sensing, and Modulation. Adv Healthc Mater 2023; 12:e2300964. [PMID: 37473719 PMCID: PMC10799194 DOI: 10.1002/adhm.202300964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Revised: 06/21/2023] [Accepted: 06/26/2023] [Indexed: 07/22/2023]
Abstract
Small-scale robots capable of remote active steering and navigation offer great potential for biomedical applications. However, the current design and manufacturing procedure impede their miniaturization and integration of various diagnostic and therapeutic functionalities. Herein, submillimeter fiber robots that can integrate navigation, sensing, and modulation functions are presented. These fiber robots are fabricated through a scalable thermal drawing process at a speed of 4 meters per minute, which enables the integration of ferromagnetic, electrical, optical, and microfluidic composite with an overall diameter of as small as 250 µm and a length of as long as 150 m. The fiber tip deflection angle can reach up to 54o under a uniform magnetic field of 45 mT. These fiber robots can navigate through complex and constrained environments, such as artificial vessels and brain phantoms. Moreover, Langendorff mouse hearts model, glioblastoma micro platforms, and in vivo mouse models are utilized to demonstrate the capabilities of sensing electrophysiology signals and performing a localized treatment. Additionally, it is demonstrated that the fiber robots can serve as endoscopes with embedded waveguides. These fiber robots provide a versatile platform for targeted multimodal detection and treatment at hard-to-reach locations in a minimally invasive and remotely controllable manner.
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Affiliation(s)
- Yujing Zhang
- Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Xiaobo Wu
- Translational Biology, Medicine, and Health Graduate Program, Virginia Tech, Roanoke, VA, 24016, USA
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, 24016, USA
| | - Ram Anand Vadlamani
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Youngmin Lim
- Department of Physics, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Jongwoon Kim
- Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Kailee David
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Earl Gilbert
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA, 24061, USA
- School of Neuroscience, Virginia Tech, Blacksburg, VA, 24061, USA
| | - You Li
- Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Ruixuan Wang
- Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Shan Jiang
- Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Anbo Wang
- Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Harald Sontheimer
- Department of Neuroscience, University of Virginia, Charlottesville, VA, 22903, USA
| | | | - Satoru Emori
- Department of Physics, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Rafael V Davalos
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Steven Poelzing
- Translational Biology, Medicine, and Health Graduate Program, Virginia Tech, Roanoke, VA, 24016, USA
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, 24016, USA
| | - Xiaoting Jia
- Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA, 24061, USA
- School of Neuroscience, Virginia Tech, Blacksburg, VA, 24061, USA
- Department of Materials Science and Engineering, Virginia Tech, Blacksburg, VA, 24061, USA
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8
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Adams WP, Raisch TB, Zhao Y, Davalos R, Barrett S, King DR, Bain CB, Colucci-Chang K, Blair GA, Hanlon A, Lozano A, Veeraraghavan R, Wan X, Deschenes I, Smyth JW, Hoeker GS, Gourdie RG, Poelzing S. Extracellular Perinexal Separation Is a Principal Determinant of Cardiac Conduction. Circ Res 2023; 133:658-673. [PMID: 37681314 PMCID: PMC10561697 DOI: 10.1161/circresaha.123.322567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 08/29/2023] [Indexed: 09/09/2023]
Abstract
BACKGROUND Cardiac conduction is understood to occur through gap junctions. Recent evidence supports ephaptic coupling as another mechanism of electrical communication in the heart. Conduction via gap junctions predicts a direct relationship between conduction velocity (CV) and bulk extracellular resistance. By contrast, ephaptic theory is premised on the existence of a biphasic relationship between CV and the volume of specialized extracellular clefts within intercalated discs such as the perinexus. Our objective was to determine the relationship between ventricular CV and structural changes to micro- and nanoscale extracellular spaces. METHODS Conduction and Cx43 (connexin43) protein expression were quantified from optically mapped guinea pig whole-heart preparations perfused with the osmotic agents albumin, mannitol, dextran 70 kDa, or dextran 2 MDa. Peak sodium current was quantified in isolated guinea pig ventricular myocytes. Extracellular resistance was quantified by impedance spectroscopy. Intercellular communication was assessed in a heterologous expression system with fluorescence recovery after photobleaching. Perinexal width was quantified from transmission electron micrographs. RESULTS CV primarily in the transverse direction of propagation was significantly reduced by mannitol and increased by albumin and both dextrans. The combination of albumin and dextran 70 kDa decreased CV relative to albumin alone. Extracellular resistance was reduced by mannitol, unchanged by albumin, and increased by both dextrans. Cx43 expression and conductance and peak sodium currents were not significantly altered by the osmotic agents. In response to osmotic agents, perinexal width, in order of narrowest to widest, was albumin with dextran 70 kDa; albumin or dextran 2 MDa; dextran 70 kDa or no osmotic agent, and mannitol. When compared in the same order, CV was biphasically related to perinexal width. CONCLUSIONS Cardiac conduction does not correlate with extracellular resistance but is biphasically related to perinexal separation, providing evidence that the relationship between CV and extracellular volume is determined by ephaptic mechanisms under conditions of normal gap junctional coupling.
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Affiliation(s)
- William P. Adams
- Center for Vascular and Heart Research at Fralin Biomedical Research Institute at VTC
- Translational Biology, Medicine and Health Program at Virginia Tech
| | - Tristan B. Raisch
- Center for Vascular and Heart Research at Fralin Biomedical Research Institute at VTC
- Translational Biology, Medicine and Health Program at Virginia Tech
| | - Yajun Zhao
- School of Biomedical Engineering and Sciences, Virginia Tech
| | - Rafael Davalos
- School of Biomedical Engineering and Sciences, Virginia Tech
| | | | - D. Ryan King
- Center for Vascular and Heart Research at Fralin Biomedical Research Institute at VTC
- Translational Biology, Medicine and Health Program at Virginia Tech
| | - Chandra B. Bain
- Center for Vascular and Heart Research at Fralin Biomedical Research Institute at VTC
| | - Katrina Colucci-Chang
- Center for Vascular and Heart Research at Fralin Biomedical Research Institute at VTC
- School of Biomedical Engineering and Sciences, Virginia Tech
| | - Grace A. Blair
- Center for Vascular and Heart Research at Fralin Biomedical Research Institute at VTC
- Translational Biology, Medicine and Health Program at Virginia Tech
| | - Alexandra Hanlon
- Virginia Tech Center for Biostatistics and Health Data Science, Roanoke, Virginia
| | - Alicia Lozano
- Virginia Tech Center for Biostatistics and Health Data Science, Roanoke, Virginia
| | - Rengasayee Veeraraghavan
- Department of Biomedical Engineering, College of Engineering, The Ohio State University
- The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center
| | - Xiaoping Wan
- The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center
| | - Isabelle Deschenes
- The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center
| | - James W. Smyth
- Center for Vascular and Heart Research at Fralin Biomedical Research Institute at VTC
- Department of Biological Sciences, College of Science, Virginia Tech
- Department of Basic Science Education, Virginia Tech Carilion School of Medicine, Roanoke, Virginia
| | - Gregory S. Hoeker
- Center for Vascular and Heart Research at Fralin Biomedical Research Institute at VTC
| | - Robert G. Gourdie
- Center for Vascular and Heart Research at Fralin Biomedical Research Institute at VTC
- School of Biomedical Engineering and Sciences, Virginia Tech
- Department of Basic Science Education, Virginia Tech Carilion School of Medicine, Roanoke, Virginia
| | - Steven Poelzing
- Center for Vascular and Heart Research at Fralin Biomedical Research Institute at VTC
- Translational Biology, Medicine and Health Program at Virginia Tech
- School of Biomedical Engineering and Sciences, Virginia Tech
- Department of Basic Science Education, Virginia Tech Carilion School of Medicine, Roanoke, Virginia
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9
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Nielsen MS, van Opbergen CJM, van Veen TAB, Delmar M. The intercalated disc: a unique organelle for electromechanical synchrony in cardiomyocytes. Physiol Rev 2023; 103:2271-2319. [PMID: 36731030 PMCID: PMC10191137 DOI: 10.1152/physrev.00021.2022] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 01/24/2023] [Accepted: 01/30/2023] [Indexed: 02/04/2023] Open
Abstract
The intercalated disc (ID) is a highly specialized structure that connects cardiomyocytes via mechanical and electrical junctions. Although described in some detail by light microscopy in the 19th century, it was in 1966 that electron microscopy images showed that the ID represented apposing cell borders and provided detailed insight into the complex ID nanostructure. Since then, much has been learned about the ID and its molecular composition, and it has become evident that a large number of proteins, not all of them involved in direct cell-to-cell coupling via mechanical or gap junctions, reside at the ID. Furthermore, an increasing number of functional interactions between ID components are emerging, leading to the concept that the ID is not the sum of isolated molecular silos but an interacting molecular complex, an "organelle" where components work in concert to bring about electrical and mechanical synchrony. The aim of the present review is to give a short historical account of the ID's discovery and an updated overview of its composition and organization, followed by a discussion of the physiological implications of the ID architecture and the local intermolecular interactions. The latter will focus on both the importance of normal conduction of cardiac action potentials as well as the impact on the pathophysiology of arrhythmias.
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Affiliation(s)
- Morten S Nielsen
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Chantal J M van Opbergen
- The Leon Charney Division of Cardiology, New York University Grossmann School of Medicine, New York, New York, United States
| | - Toon A B van Veen
- Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Mario Delmar
- The Leon Charney Division of Cardiology, New York University Grossmann School of Medicine, New York, New York, United States
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10
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Struckman HL, Moise N, King DR, Soltisz A, Buxton A, Dunlap I, Chen Z, Radwański PB, Weinberg SH, Veeraraghavan R. Unraveling Chamber-specific Differences in Intercalated Disc Ultrastructure and Molecular Organization and Their Impact on Cardiac Conduction. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.13.528369. [PMID: 36824727 PMCID: PMC9949041 DOI: 10.1101/2023.02.13.528369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
During each heartbeat, the propagation of action potentials through the heart coordinates the contraction of billions of individual cardiomyocytes and is thus, a critical life process. Unsurprisingly, intercalated discs, which are cell-cell contact sites specialized to provide electrical and mechanical coupling between adjacent cardiomyocytes, have been the focus of much investigation. Slowed or disrupted propagation leads to potentially life-threatening arrhythmias in a wide range of pathologies, where intercalated disc remodeling is a common finding. Hence, the importance and urgency of understanding intercalated disc structure and its influence on action potential propagation. Surprisingly, however, conventional modeling approaches cannot predict changes in propagation elicited by perturbations that alter intercalated disc ultrastructure or molecular organization, owing to lack of quantitative structural data at subcellular through nano scales. In order to address this critical gap in knowledge, we sought to quantify intercalated disc structure at these finer spatial scales in the healthy adult mouse heart and relate them to function in a chamber-specific manner as a precursor to understanding the impacts of pathological intercalated disc remodeling. Using super-resolution light microscopy, electron microscopy, and computational image analysis, we provide here the first ever systematic, multiscale quantification of intercalated disc ultrastructure and molecular organization. By incorporating these data into a rule-based model of cardiac tissue with realistic intercalated disc structure, and comparing model predictions of electrical propagation with experimental measures of conduction velocity, we reveal that atrial intercalated discs can support faster conduction than their ventricular counterparts, which is normally masked by inter-chamber differences in myocyte geometry. Further, we identify key ultrastructural and molecular organization features underpinning the ability of atrial intercalated discs to support faster conduction. These data provide the first stepping stone to elucidating chamber-specific impacts of pathological intercalated disc remodeling, as occurs in many arrhythmic diseases.
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11
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Zhang Y, Wu X, Vadlamani RA, Lim Y, Kim J, David K, Gilbert E, Li Y, Wang R, Jiang S, Wang A, Sontheimer H, English D, Emori S, Davalos RV, Poelzing S, Jia X. Multifunctional ferromagnetic fiber robots for navigation, sensing, and treatment in minimally invasive surgery. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.27.525973. [PMID: 36778450 PMCID: PMC9915472 DOI: 10.1101/2023.01.27.525973] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Small-scale robots capable of remote active steering and navigation offer great potential for biomedical applications. However, the current design and manufacturing procedure impede their miniaturization and integration of various diagnostic and therapeutic functionalities. Here, we present a robotic fiber platform for integrating navigation, sensing, and therapeutic functions at a submillimeter scale. These fiber robots consist of ferromagnetic, electrical, optical, and microfluidic components, fabricated with a thermal drawing process. Under magnetic actuation, they can navigate through complex and constrained environments, such as artificial vessels and brain phantoms. Moreover, we utilize Langendorff mouse hearts model, glioblastoma microplatforms, and in vivo mouse models to demonstrate the capabilities of sensing electrophysiology signals and performing localized treatment. Additionally, we demonstrate that the fiber robots can serve as endoscopes with embedded waveguides. These fiber robots provide a versatile platform for targeted multimodal detection and treatment at hard-to-reach locations in a minimally invasive and remotely controllable manner.
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Affiliation(s)
- Yujing Zhang
- The Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA
| | - Xiaobo Wu
- Translational Biology, Medicine, and Health Graduate Program, Virginia Tech, Roanoke, VA
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA
| | - Ram Anand Vadlamani
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA
| | - Youngmin Lim
- Department of Physics, Virginia Tech, Blacksburg, VA
| | - Jongwoon Kim
- The Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA
| | - Kailee David
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA
| | - Earl Gilbert
- School of Neuroscience, Virginia Tech, Blacksburg, VA
| | - You Li
- The Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA
| | - Ruixuan Wang
- The Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA
| | - Shan Jiang
- The Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA
| | - Anbo Wang
- The Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA
| | - Harald Sontheimer
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA
| | | | - Satoru Emori
- Department of Physics, Virginia Tech, Blacksburg, VA
| | - Rafael V Davalos
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA
| | - Steven Poelzing
- Translational Biology, Medicine, and Health Graduate Program, Virginia Tech, Roanoke, VA
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA
| | - Xiaoting Jia
- The Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA
- School of Neuroscience, Virginia Tech, Blacksburg, VA
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12
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Binder MS, Wu Y, Baker JW, Rowe JF, Wyatt DA, Choate C, Poelzing S, Joseph M. A retrospective comparison of albumin versus mannitol priming fluid with relation to postoperative atrial fibrillation. J Card Surg 2022; 37:3485-3491. [PMID: 36116062 PMCID: PMC9826347 DOI: 10.1111/jocs.16960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 08/10/2022] [Accepted: 08/27/2022] [Indexed: 01/11/2023]
Abstract
BACKGROUND AND AIM OF THE STUDY Postoperative atrial fibrillation (POAF) is a common complication following cardiac surgery which can result in increased mortality and increased healthcare costs. During Hurricane Maria (2017), a nationwide shortage of mannitol occurred, and our institution switched to the utilization of albumin as a priming fluid solution. We observed decreased rates of POAF during that time and began alternating albumin and mannitol priming fluid solutions. We hypothesized this observation may be from altered perinexal conduction from albumin utilization. METHODS A retrospective chart review of all patients from January 2020 through December 2020 who underwent cardiac surgery was performed, to determine if albumin was associated with reduced POAF rates. Two hundred and thirteen patients were identified and 4 were excluded. Two hundred and nine patients (110 albumin priming fluid and 99 mannitol priming fluid) were included in our final analysis. RESULTS Analysis was performed for all patients with POAF and in patients with new-onset AF (without a history of prior AF) after surgery. POAF rates showed no statistically significant difference between cohorts. For all patients, POAF occurred in 43% of the albumin subgroup and 47% of the mannitol subgroup (p = .53) and for patients with new-onset AF, POAF occurred in 35% of the albumin subgroup versus 42% of the mannitol subgroup (p = .36). Logistic regression revealed that age, ejection fraction and cardiopulmonary bypass time was associated with POAF, in our cohort. CONCLUSIONS The use of albumin compared to mannitol as priming fluid solutions was not associated with statistically significant reductions in POAF rate, in our population.
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Affiliation(s)
- M. Scott Binder
- Departments of Cardiology, Cardiothoracic SurgeryVirginia Tech CarilionRoanokeVirginiaUSA
| | - YingXing Wu
- Department of Health AnalyticsVirginia Tech CarilionRoanokeVirginiaUSA
| | - Joseph W. Baker
- Departments of Cardiology, Cardiothoracic SurgeryVirginia Tech CarilionRoanokeVirginiaUSA
| | - Joseph F. Rowe
- Departments of Cardiology, Cardiothoracic SurgeryVirginia Tech CarilionRoanokeVirginiaUSA
| | - David A. Wyatt
- Departments of Cardiology, Cardiothoracic SurgeryVirginia Tech CarilionRoanokeVirginiaUSA
| | - Cynthia Choate
- Departments of Cardiology, Cardiothoracic SurgeryVirginia Tech CarilionRoanokeVirginiaUSA
| | - Steven Poelzing
- Department of Biomedical Engineering and MechanicsVirginia Tech Fralin Biomedical Research InstituteRoanokeVirginiaUSA
| | - Mark Joseph
- Departments of Cardiology, Cardiothoracic SurgeryVirginia Tech CarilionRoanokeVirginiaUSA
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13
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Lin J, Abraham A, George SA, Greer-Short A, Blair GA, Moreno A, Alber BR, Kay MW, Poelzing S. Ephaptic Coupling Is a Mechanism of Conduction Reserve During Reduced Gap Junction Coupling. Front Physiol 2022; 13:848019. [PMID: 35600295 PMCID: PMC9117633 DOI: 10.3389/fphys.2022.848019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Accepted: 04/01/2022] [Indexed: 11/13/2022] Open
Abstract
Many cardiac pathologies are associated with reduced gap junction (GJ) coupling, an important modulator of cardiac conduction velocity (CV). However, the relationship between phenotype and functional expression of the connexin GJ family of proteins is controversial. For example, a 50% reduction of GJ coupling has been shown to have little impact on myocardial CV due to a concept known as conduction reserve. This can be explained by the ephaptic coupling (EpC) theory whereby conduction is maintained by a combination of low GJ coupling and increased electrical fields generated in the sodium channel rich clefts between neighboring myocytes. At the same time, low GJ coupling may also increase intracellular charge accumulation within myocytes, resulting in a faster transmembrane potential rate of change during depolarization (dV/dt_max) that maintains macroscopic conduction. To provide insight into the prevalence of these two phenomena during pathological conditions, we investigated the relationship between EpC and charge accumulation within the setting of GJ remodeling using multicellular simulations and companion perfused mouse heart experiments. Conduction along a fiber of myocardial cells was simulated for a range of GJ conditions. The model incorporated intercellular variations, including GJ coupling conductance and distribution, cell-to-cell separation in the intercalated disc (perinexal width—WP), and variations in sodium channel distribution. Perfused heart studies having conditions analogous to those of the simulations were performed using wild type mice and mice heterozygous null for the connexin gene Gja1. With insight from simulations, the relative contributions of EpC and charge accumulation on action potential parameters and conduction velocities were analyzed. Both simulation and experimental results support a common conclusion that low GJ coupling decreases and narrowing WP increases the rate of the AP upstroke when sodium channels are densely expressed at the ends of myocytes, indicating that conduction reserve is more dependent on EpC than charge accumulation during GJ uncoupling.
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Affiliation(s)
- Joyce Lin
- Department of Mathematics, California Polytechnic State University, San Luis Obispo, CA, United States
- *Correspondence: Joyce Lin, ; Steven Poelzing,
| | - Anand Abraham
- Virginia Tech Carilion School of Medicine, Roanoke, VA, United States
- Fralin Biomedical Research Institute at Virginia Tech Carilion School of Medicine, Roanoke, VA, United States
| | - Sharon A. George
- Fralin Biomedical Research Institute at Virginia Tech Carilion School of Medicine, Roanoke, VA, United States
- Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA, United States
| | - Amara Greer-Short
- Fralin Biomedical Research Institute at Virginia Tech Carilion School of Medicine, Roanoke, VA, United States
- Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA, United States
| | - Grace A. Blair
- Fralin Biomedical Research Institute at Virginia Tech Carilion School of Medicine, Roanoke, VA, United States
- Translational Biology, Medicine and Health, Virginia Tech, Roanoke, VA, United States
| | - Angel Moreno
- Department of Biomedical Engineering, The George Washington University, Washington, DC, United States
| | - Bridget R. Alber
- Department of Biomedical Engineering, The George Washington University, Washington, DC, United States
| | - Matthew W. Kay
- Department of Biomedical Engineering, The George Washington University, Washington, DC, United States
| | - Steven Poelzing
- Virginia Tech Carilion School of Medicine, Roanoke, VA, United States
- Fralin Biomedical Research Institute at Virginia Tech Carilion School of Medicine, Roanoke, VA, United States
- Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA, United States
- Translational Biology, Medicine and Health, Virginia Tech, Roanoke, VA, United States
- *Correspondence: Joyce Lin, ; Steven Poelzing,
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14
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Karbassi E, Murry CE. Flexing Their Muscles: Maturation of Stem Cell-Derived Cardiomyocytes on Elastomeric Substrates to Enhance Cardiac Repair. Circulation 2022; 145:1427-1430. [PMID: 35500046 PMCID: PMC9069846 DOI: 10.1161/circulationaha.122.059079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Elaheh Karbassi
- Institute for Stem Cell and Regenerative Medicine, Center for Cardiovascular Biology, and Department of Laboratory Medicine & Pathology (E.K., C.E.M.), University of Washington, Seattle
| | - Charles E Murry
- Institute for Stem Cell and Regenerative Medicine, Center for Cardiovascular Biology, and Department of Laboratory Medicine & Pathology (E.K., C.E.M.), University of Washington, Seattle.,Division of Cardiology, Department of Medicine (C.E.M.), University of Washington, Seattle.,Department of Bioengineering (C.E.M.), University of Washington, Seattle.,Sana Biotechnology, Seattle, WA (C.E.M.)
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15
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Krahn PRP, Biswas L, Ferguson S, Ramanan V, Barry J, Singh SM, Pop M, Wright GA. MRI-Guided Cardiac RF Ablation for Comparing MRI Characteristics of Acute Lesions and Associated Electrophysiologic Voltage Reductions. IEEE Trans Biomed Eng 2022; 69:2657-2666. [PMID: 35171765 DOI: 10.1109/tbme.2022.3152145] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Objective: Radiofrequency (RF) energy delivered to cardiac tissue produces a core ablation lesion with surrounding edema, the latter of which has been implicated in acute procedural failure of Ventricular Tachycardia (VT) ablation and late arrhythmia recurrence. This study sought to investigate the electrophysiological characteristics of acute RF lesions in the left ventricle (LV) visualized with native-contrast Magnetic Resonance Imaging (MRI). Methods: An MR-guided electrophysiology system was used to deliver RF ablation in the LV of 8 swine (9 RF lesions in total), then perform MRI and electroanatomic mapping. The permanent RF lesions and transient edema were delineated via native-contrast MRI segmentation of T1-weighted images and T2 maps respectively. Bipolar voltage measurements were matched with image characteristics of pixels adjacent to the catheter tip. Native-contrast MR visualization was verified with 3D late gadolinium enhanced MRI and histology. Results: The T2-derived edema was significantly larger than the T1-derived RF lesion (2.11.5 mL compared to 0.580.34 mL; p=0.01). Bipolar voltage was significantly reduced in the presence of RF lesion core (p<0.05) and edema (p<0.05), with similar trends suggesting that both the permanent lesion and transient edema contributed to the region of reduced voltage. While bipolar voltage was significantly decreased where RF lesions are present (p<0.05), voltage did not change significantly with lesion transmurality (p>0.05). Conclusion: Permanent RF lesions and transient edema are distinct in native-contrast MR images, but not differentiable using bipolar voltage. Significance: Intraprocedural native-contrast MRI may provide valuable lesion assessment in MR-guided ablation, whose clinical application is now feasible.
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16
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Wu X, Hoeker GS, Blair GA, King DR, Gourdie RG, Weinberg SH, Poelzing S. Hypernatremia and intercalated disc edema synergistically exacerbate long-QT syndrome type 3 phenotype. Am J Physiol Heart Circ Physiol 2021; 321:H1042-H1055. [PMID: 34623182 DOI: 10.1152/ajpheart.00366.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Cardiac voltage-gated sodium channel gain-of-function prolongs repolarization in the long-QT syndrome type 3 (LQT3). Previous studies suggest that narrowing the perinexus within the intercalated disc, leading to rapid sodium depletion, attenuates LQT3-associated action potential duration (APD) prolongation. However, it remains unknown whether extracellular sodium concentration modulates APD prolongation during sodium channel gain-of-function. We hypothesized that elevated extracellular sodium concentration and widened perinexus synergistically prolong APD in LQT3. LQT3 was induced with sea anemone toxin (ATXII) in Langendorff-perfused guinea pig hearts (n = 34). Sodium concentration was increased from 145 to 160 mM. Perinexal expansion was induced with mannitol or the sodium channel β1-subunit adhesion domain antagonist (βadp1). Epicardial ventricular action potentials were optically mapped. Individual and combined effects of varying clefts and sodium concentrations were simulated in a computational model. With ATXII, both mannitol and βadp1 significantly widened the perinexus and prolonged APD, respectively. The elevated sodium concentration alone significantly prolonged APD as well. Importantly, the combination of elevated sodium concentration and perinexal widening synergistically prolonged APD. Computational modeling results were consistent with animal experiments. Concurrently elevating extracellular sodium and increasing intercalated disc edema prolongs repolarization more than the individual interventions alone in LQT3. This synergistic effect suggests an important clinical implication that hypernatremia in the presence of cardiac edema can markedly increase LQT3-associated APD prolongation. Therefore, to our knowledge, this is the first study to provide evidence of a tractable and effective strategy to mitigate LQT3 phenotype by means of managing sodium levels and preventing cardiac edema in patients.NEW & NOTEWORTHY This is the first study to demonstrate that the long-QT syndrome type 3 (LQT3) phenotype can be exacerbated or concealed by regulating extracellular sodium concentrations and/or the intercalated disc separation. The animal experiments and computational modeling in the current study reveal a critically important clinical implication: sodium dysregulation in the presence of edema within the intercalated disc can markedly increase the risk of arrhythmia in LQT3. These findings strongly suggest that maintaining extracellular sodium within normal physiological limits may be an effective and inexpensive therapeutic option for patients with congenital or acquired sodium channel gain-of-function diseases.
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Affiliation(s)
- Xiaobo Wu
- Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Roanoke, Virginia.,Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia
| | - Gregory S Hoeker
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia
| | - Grace A Blair
- Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Roanoke, Virginia.,Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia
| | - D Ryan King
- Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Roanoke, Virginia.,Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia
| | - Robert G Gourdie
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - Seth H Weinberg
- Department of Biomedical Engineering, Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio
| | - Steven Poelzing
- Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Roanoke, Virginia.,Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
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17
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Gottlieb LA, Dekker LRC, Coronel R. The Blinding Period Following Ablation Therapy for Atrial Fibrillation: Proarrhythmic and Antiarrhythmic Pathophysiological Mechanisms. JACC Clin Electrophysiol 2021; 7:416-430. [PMID: 33736761 DOI: 10.1016/j.jacep.2021.01.011] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 01/14/2021] [Accepted: 01/17/2021] [Indexed: 02/01/2023]
Abstract
Atrial fibrillation (AF) causes heart failure, ischemic strokes, and poor quality of life. The number of patients with AF is estimated to increase to 18 million in Europe in 2050. Pharmacological therapy does not cure AF in all patients. Ablative pulmonary vein isolation is recommended for patients with drug-resistant symptomatic paroxysmal AF but is successful in only about 60%. In patients in whom ablative therapy is successful on the long term, recurrence of AF may occur in the first weeks to months after pulmonary vein ablation. The early recurrence (or delayed cure) of AF is not understood but forms the basis for the generally accepted 3-month blinding (or blanking) period after ablation therapy, which is not included in the evaluation of the eventual success rate of the procedures. The underlying pathophysiological processes responsible for early recurrence and the delayed cure are unknown. The implicit assumption of the blinding period is that the AF mechanism in this period is different from the ablation-targeted AF mechanism (ectopy from the pulmonary veins). In this review, we evaluate the temporary and long-lasting pro- and antiarrhythmic effects of each of the pathophysiological processes and interventions (necrosis, ischemia, oxidative stress, edema, inflammation, autonomic nervous activity, tissue repair, mechanical remodeling, and use of antiarrhythmic drugs) occurring in the blinding period that can modulate AF mechanisms. We propose that stretch-reducing ablation scar is a permanent antiarrhythmic mechanism that develops during the blinding period and is the reason for delayed cure.
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Affiliation(s)
- Lisa A Gottlieb
- Electrophysiology and Heart Modelling Institute, University of Bordeaux, Pessac, France; Department of Experimental Cardiology, Amsterdam University Medical Centre, Academic Medical Centre, Amsterdam, the Netherlands
| | - Lukas R C Dekker
- Department of Electrical Engineering, University of Technology, Eindhoven, the Netherlands; Cardiology Department, Catharina Hospital, Eindhoven, the Netherlands.
| | - Ruben Coronel
- Electrophysiology and Heart Modelling Institute, University of Bordeaux, Pessac, France; Department of Experimental Cardiology, Amsterdam University Medical Centre, Academic Medical Centre, Amsterdam, the Netherlands
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18
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Moise N, Struckman HL, Dagher C, Veeraraghavan R, Weinberg SH. Intercalated disk nanoscale structure regulates cardiac conduction. J Gen Physiol 2021; 153:212474. [PMID: 34264306 PMCID: PMC8287520 DOI: 10.1085/jgp.202112897] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 04/13/2021] [Accepted: 06/07/2021] [Indexed: 12/31/2022] Open
Abstract
The intercalated disk (ID) is a specialized subcellular region that provides electrical and mechanical connections between myocytes in the heart. The ID has a clearly defined passive role in cardiac tissue, transmitting mechanical forces and electrical currents between cells. Recent studies have shown that Na+ channels, the primary current responsible for cardiac excitation, are preferentially localized at the ID, particularly within nanodomains such as the gap junction-adjacent perinexus and mechanical junction-associated adhesion-excitability nodes, and that perturbations of ID structure alter cardiac conduction. This suggests that the ID may play an important, active role in regulating conduction. However, the structures of the ID and intercellular cleft are not well characterized and, to date, no models have incorporated the influence of ID structure on conduction in cardiac tissue. In this study, we developed an approach to generate realistic finite element model (FEM) meshes replicating nanoscale of the ID structure, based on experimental measurements from transmission electron microscopy images. We then integrated measurements of the intercellular cleft electrical conductivity, derived from the FEM meshes, into a novel cardiac tissue model formulation. FEM-based calculations predict that the distribution of cleft conductances is sensitive to regional changes in ID structure, specifically the intermembrane separation and gap junction distribution. Tissue-scale simulations predict that ID structural heterogeneity leads to significant spatial variation in electrical polarization within the intercellular cleft. Importantly, we found that this heterogeneous cleft polarization regulates conduction by desynchronizing the activation of postjunctional Na+ currents. Additionally, these heterogeneities lead to a weaker dependence of conduction velocity on gap junctional coupling, compared with prior modeling formulations that neglect or simplify ID structure. Further, we found that disruption of local ID nanodomains can either slow or enhance conduction, depending on gap junctional coupling strength. Our study therefore suggests that ID nanoscale structure can play a significant role in regulating cardiac conduction.
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Affiliation(s)
| | | | | | - Rengasayee Veeraraghavan
- The Ohio State University, Columbus, OH.,Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH
| | - Seth H Weinberg
- The Ohio State University, Columbus, OH.,Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH
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19
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King DR, Entz M, Blair GA, Crandell I, Hanlon AL, Lin J, Hoeker GS, Poelzing S. The conduction velocity-potassium relationship in the heart is modulated by sodium and calcium. Pflugers Arch 2021; 473:557-571. [PMID: 33660028 PMCID: PMC7940307 DOI: 10.1007/s00424-021-02537-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 01/28/2021] [Accepted: 02/04/2021] [Indexed: 01/27/2023]
Abstract
The relationship between cardiac conduction velocity (CV) and extracellular potassium (K+) is biphasic, with modest hyperkalemia increasing CV and severe hyperkalemia slowing CV. Recent studies from our group suggest that elevating extracellular sodium (Na+) and calcium (Ca2+) can enhance CV by an extracellular pathway parallel to gap junctional coupling (GJC) called ephaptic coupling that can occur in the gap junction adjacent perinexus. However, it remains unknown whether these same interventions modulate CV as a function of K+. We hypothesize that Na+, Ca2+, and GJC can attenuate conduction slowing consequent to severe hyperkalemia. Elevating Ca2+ from 1.25 to 2.00 mM significantly narrowed perinexal width measured by transmission electron microscopy. Optically mapped, Langendorff-perfused guinea pig hearts perfused with increasing K+ revealed the expected biphasic CV-K+ relationship during perfusion with different Na+ and Ca2+ concentrations. Neither elevating Na+ nor Ca2+ alone consistently modulated the positive slope of CV-K+ or conduction slowing at 10-mM K+; however, combined Na+ and Ca2+ elevation significantly mitigated conduction slowing at 10-mM K+. Pharmacologic GJC inhibition with 30-μM carbenoxolone slowed CV without changing the shape of CV-K+ curves. A computational model of CV predicted that elevating Na+ and narrowing clefts between myocytes, as occur with perinexal narrowing, reduces the positive and negative slopes of the CV-K+ relationship but do not support a primary role of GJC or sodium channel conductance. These data demonstrate that combinatorial effects of Na+ and Ca2+ differentially modulate conduction during hyperkalemia, and enhancing determinants of ephaptic coupling may attenuate conduction changes in a variety of physiologic conditions.
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Affiliation(s)
- D Ryan King
- Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, USA
| | - Michael Entz
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, USA
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
| | - Grace A Blair
- Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, USA
| | - Ian Crandell
- Center for Biostatistics and Health Data Science, Virginia Polytechnic Institute and State University, Roanoke, VA, USA
| | - Alexandra L Hanlon
- Center for Biostatistics and Health Data Science, Virginia Polytechnic Institute and State University, Roanoke, VA, USA
| | - Joyce Lin
- Department of Mathematics, California Polytechnic State University, San Luis Obispo, CA, USA
| | - Gregory S Hoeker
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, USA
| | - Steven Poelzing
- Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA.
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, USA.
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA.
- School of Medicine, Virginia Tech Carilion, Roanoke, VA, USA.
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20
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Kotadia I, Whitaker J, Roney C, Niederer S, O’Neill M, Bishop M, Wright M. Anisotropic Cardiac Conduction. Arrhythm Electrophysiol Rev 2020; 9:202-210. [PMID: 33437488 PMCID: PMC7788398 DOI: 10.15420/aer.2020.04] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Accepted: 10/09/2020] [Indexed: 01/06/2023] Open
Abstract
Anisotropy is the property of directional dependence. In cardiac tissue, conduction velocity is anisotropic and its orientation is determined by myocyte direction. Cell shape and size, excitability, myocardial fibrosis, gap junction distribution and function are all considered to contribute to anisotropic conduction. In disease states, anisotropic conduction may be enhanced, and is implicated, in the genesis of pathological arrhythmias. The principal mechanism responsible for enhanced anisotropy in disease remains uncertain. Possible contributors include changes in cellular excitability, changes in gap junction distribution or function and cellular uncoupling through interstitial fibrosis. It has recently been demonstrated that myocyte orientation may be identified using diffusion tensor magnetic resonance imaging in explanted hearts, and multisite pacing protocols have been proposed to estimate myocyte orientation and anisotropic conduction in vivo. These tools have the potential to contribute to the understanding of the role of myocyte disarray and anisotropic conduction in arrhythmic states.
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Affiliation(s)
- Irum Kotadia
- School of Biomedical Engineering and Imaging Sciences, King’s College, London, UK
- Guy’s and St Thomas’ NHS Foundation Trust, London, UK
| | - John Whitaker
- School of Biomedical Engineering and Imaging Sciences, King’s College, London, UK
- Guy’s and St Thomas’ NHS Foundation Trust, London, UK
| | - Caroline Roney
- School of Biomedical Engineering and Imaging Sciences, King’s College, London, UK
| | - Steven Niederer
- School of Biomedical Engineering and Imaging Sciences, King’s College, London, UK
| | - Mark O’Neill
- School of Biomedical Engineering and Imaging Sciences, King’s College, London, UK
- Guy’s and St Thomas’ NHS Foundation Trust, London, UK
| | - Martin Bishop
- School of Biomedical Engineering and Imaging Sciences, King’s College, London, UK
| | - Matthew Wright
- School of Biomedical Engineering and Imaging Sciences, King’s College, London, UK
- Guy’s and St Thomas’ NHS Foundation Trust, London, UK
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21
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Mezache L, Struckman HL, Greer-Short A, Baine S, Györke S, Radwański PB, Hund TJ, Veeraraghavan R. Vascular endothelial growth factor promotes atrial arrhythmias by inducing acute intercalated disk remodeling. Sci Rep 2020; 10:20463. [PMID: 33235263 PMCID: PMC7687901 DOI: 10.1038/s41598-020-77562-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 11/09/2020] [Indexed: 12/30/2022] Open
Abstract
Atrial fibrillation (AF) is the most common arrhythmia and is associated with inflammation. AF patients have elevated levels of inflammatory cytokines known to promote vascular leak, such as vascular endothelial growth factor A (VEGF). However, the contribution of vascular leak and consequent cardiac edema to the genesis of atrial arrhythmias remains unknown. Previous work suggests that interstitial edema in the heart can acutely promote ventricular arrhythmias by disrupting ventricular myocyte intercalated disk (ID) nanodomains rich in cardiac sodium channels (NaV1.5) and slowing cardiac conduction. Interestingly, similar disruption of ID nanodomains has been identified in atrial samples from AF patients. Therefore, we tested the hypothesis that VEGF-induced vascular leak can acutely increase atrial arrhythmia susceptibility by disrupting ID nanodomains and slowing atrial conduction. Treatment of murine hearts with VEGF (30–60 min, at clinically relevant levels) prolonged the electrocardiographic P wave and increased susceptibility to burst pacing-induced atrial arrhythmias. Optical voltage mapping revealed slower atrial conduction following VEGF treatment (10 ± 0.4 cm/s vs. 21 ± 1 cm/s at baseline, p < 0.05). Transmission electron microscopy revealed increased intermembrane spacing at ID sites adjacent to gap junctions (GJs; 64 ± 9 nm versus 17 ± 1 nm in controls, p < 0.05), as well as sites next to mechanical junctions (MJs; 63 ± 4 nm versus 27 ± 2 nm in controls, p < 0.05) in VEGF–treated hearts relative to controls. Importantly, super-resolution microscopy and quantitative image analysis revealed reorganization of NaV1.5 away from dense clusters localized near GJs and MJs to a more diffuse distribution throughout the ID. Taken together, these data suggest that VEGF can acutely predispose otherwise normal hearts to atrial arrhythmias by dynamically disrupting NaV1.5-rich ID nanodomains and slowing atrial conduction. These data highlight inflammation-induced vascular leak as a potential factor in the development and progression of AF.
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Affiliation(s)
- Louisa Mezache
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, 460 Medical Center Dr., Rm 415A, IBMR, Columbus, OH, 43210, USA
| | - Heather L Struckman
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, 460 Medical Center Dr., Rm 415A, IBMR, Columbus, OH, 43210, USA
| | - Amara Greer-Short
- The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Stephen Baine
- The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, USA.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Sándor Györke
- The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, USA.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Przemysław B Radwański
- The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, USA.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA.,Division of Pharmacy Practice and Sciences, College of Pharmacy, The Ohio State University, Columbus, OH, USA
| | - Thomas J Hund
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, 460 Medical Center Dr., Rm 415A, IBMR, Columbus, OH, 43210, USA.,The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Rengasayee Veeraraghavan
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, 460 Medical Center Dr., Rm 415A, IBMR, Columbus, OH, 43210, USA. .,The Frick Center for Heart Failure and Arrhythmia, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, USA. .,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA.
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22
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Filice D, Dhahri W, Solan JL, Lampe PD, Steele E, Milani N, Van Biber B, Zhu WZ, Valdman TS, Romagnuolo R, Otero-Cruz JD, Hauch KD, Kay MW, Sarvazyan N, Laflamme MA. Optical mapping of human embryonic stem cell-derived cardiomyocyte graft electrical activity in injured hearts. Stem Cell Res Ther 2020; 11:417. [PMID: 32988411 PMCID: PMC7523067 DOI: 10.1186/s13287-020-01919-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 08/13/2020] [Accepted: 09/01/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) show tremendous promise for cardiac regeneration, but the successful development of hESC-CM-based therapies requires improved tools to investigate their electrical behavior in recipient hearts. While optical voltage mapping is a powerful technique for studying myocardial electrical activity ex vivo, we have previously shown that intra-cardiac hESC-CM grafts are not labeled by conventional voltage-sensitive fluorescent dyes. We hypothesized that the water-soluble voltage-sensitive dye di-2-ANEPEQ would label engrafted hESC-CMs and thereby facilitate characterization of graft electrical function and integration. METHODS We developed and validated a novel optical voltage mapping strategy based on the simultaneous imaging of the calcium-sensitive fluorescent protein GCaMP3, a graft-autonomous reporter of graft activation, and optical action potentials (oAPs) derived from di-2-ANEPEQ, which labels both graft and host myocardium. Cardiomyocytes from three different GCaMP3+ hESC lines (H7, RUES2, or ESI-17) were transplanted into guinea pig models of subacute and chronic infarction, followed by optical mapping at 2 weeks post-transplantation. RESULTS Use of a water-soluble voltage-sensitive dye revealed pro-arrhythmic properties of GCaMP3+ hESC-CM grafts from all three lines including slow conduction velocity, incomplete host-graft coupling, and spatially heterogeneous patterns of activation that varied beat-to-beat. GCaMP3+ hESC-CMs from the RUES2 and ESI-17 lines both showed prolonged oAP durations both in vitro and in vivo. Although hESC-CMs partially remuscularize the injured hearts, histological evaluation revealed immature graft structure and impaired gap junction expression at this early timepoint. CONCLUSION Simultaneous imaging of GCaMP3 and di-2-ANEPEQ allowed us to acquire the first unambiguously graft-derived oAPs from hESC-CM-engrafted hearts and yielded critical insights into their arrhythmogenic potential and line-to-line variation.
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Affiliation(s)
- Dominic Filice
- Department of Bioengineering, University of Washington, Seattle, WA, 98195, USA
- Institute for Stem Cell & Regenerative Medicine, University of Washington, Seattle, WA, 98195, USA
| | - Wahiba Dhahri
- McEwen Stem Cell Institute, University Health Network, 101 College Street, Rm 3-908, Toronto, ON, M5G 1L7, Canada
- Peter Munk Cardiac Centre, University Health Network, Toronto, ON, M5G 2N2, Canada
| | - Joell L Solan
- Fred Hutchinson Cancer Research Center, Seattle, WA, 98109, USA
| | - Paul D Lampe
- Fred Hutchinson Cancer Research Center, Seattle, WA, 98109, USA
| | - Erin Steele
- Institute for Stem Cell & Regenerative Medicine, University of Washington, Seattle, WA, 98195, USA
- Department of Biology, University of Washington, Seattle, WA, 98195, USA
| | - Nikita Milani
- Department of Bioengineering, University of Washington, Seattle, WA, 98195, USA
- Institute for Stem Cell & Regenerative Medicine, University of Washington, Seattle, WA, 98195, USA
| | - Benjamin Van Biber
- Institute for Stem Cell & Regenerative Medicine, University of Washington, Seattle, WA, 98195, USA
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Wei-Zhong Zhu
- Institute for Stem Cell & Regenerative Medicine, University of Washington, Seattle, WA, 98195, USA
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Tamilla Sadikov Valdman
- McEwen Stem Cell Institute, University Health Network, 101 College Street, Rm 3-908, Toronto, ON, M5G 1L7, Canada
- Peter Munk Cardiac Centre, University Health Network, Toronto, ON, M5G 2N2, Canada
| | - Rocco Romagnuolo
- McEwen Stem Cell Institute, University Health Network, 101 College Street, Rm 3-908, Toronto, ON, M5G 1L7, Canada
- Peter Munk Cardiac Centre, University Health Network, Toronto, ON, M5G 2N2, Canada
| | - José David Otero-Cruz
- Institute for Stem Cell & Regenerative Medicine, University of Washington, Seattle, WA, 98195, USA
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Kip D Hauch
- Department of Bioengineering, University of Washington, Seattle, WA, 98195, USA
| | - Matthew W Kay
- Department of Biomedical Engineering, G. Washington University, Washington, DC, 20052, USA
| | - Narine Sarvazyan
- Department of Pharmacology & Physiology, G. Washington University, Washington, DC, 20052, USA
| | - Michael A Laflamme
- McEwen Stem Cell Institute, University Health Network, 101 College Street, Rm 3-908, Toronto, ON, M5G 1L7, Canada.
- Peter Munk Cardiac Centre, University Health Network, Toronto, ON, M5G 2N2, Canada.
- Department of Laboratory Medicine & Pathobiology, University of Toronto, Toronto, ON, M5G 1L7, Canada.
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23
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Hoeker GS, James CC, Tegge AN, Gourdie RG, Smyth JW, Poelzing S. Attenuating loss of cardiac conduction during no-flow ischemia through changes in perfusate sodium and calcium. Am J Physiol Heart Circ Physiol 2020; 319:H396-H409. [PMID: 32678707 DOI: 10.1152/ajpheart.00112.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Myocardial ischemia leads to conduction slowing, cell-to-cell uncoupling, and arrhythmias. We previously demonstrated that varying perfusate sodium (Na+) and calcium (Ca2+) attenuates conduction slowing and arrhythmias during simulated ischemia with continuous perfusion. Cardioprotection was selectively associated with widening of the perinexus, a gap junction adjacent nanodomain important to ephaptic coupling. It is unknown whether perfusate composition affects the perinexus or ischemic conduction during nonsimulated ischemia, when coronary flow is reduced or halted. We hypothesized that altering preischemic perfusate composition could facilitate perinexal expansion and attenuate conduction slowing during global ischemia. To test this hypothesis, ex vivo guinea pig hearts (n = 49) were Langendorff perfused with 145 or 153 mM Na+ and 1.25 or 2.0 mM Ca2+ and optically mapped during 30 min of no-flow ischemia. Altering Na+ and Ca2+ did not substantially affect baseline conduction. Increasing Na+ and decreasing Ca2+ both lowered pacing thresholds, whereas increasing Ca2+ narrowed perinexal width (Wp). A least squares mean estimate revealed that reduced perfusate Na+ and Ca2+ resulted in the most severe conduction slowing during ischemia. Increasing Na+ alone modestly attenuated conduction slowing, yet significantly delayed the median time to conduction block (10 to 16 min). Increasing both Na+ and Ca2+ selectively widened Wp during ischemia (22.7 vs. 15.7 nm) and attenuated conduction slowing to the greatest extent. Neither repolarization nor levels of total or phosphorylated connexin43 correlated with conduction slowing or block. Thus, perfusate-dependent widening of the perinexus preserved ischemic conduction and may be an adaptive response to ischemic stress.NEW & NOTEWORTHY Conduction slowing during acute ischemia creates an arrhythmogenic substrate. We have shown that extracellular ionic concentrations can alter conduction by modulating ephaptic coupling. Here, we demonstrate increased extracellular sodium and calcium significantly attenuate conduction slowing during no-flow ischemia. This effect was associated with selective widening of the perinexus, an intercalated disc nanodomain and putative cardiac ephapse. These findings suggest that acute changes in ephaptic coupling may serve as an adaptive response to ischemic stress.
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Affiliation(s)
- Gregory S Hoeker
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia
| | - Carissa C James
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Roanoke, Virginia
| | - Allison N Tegge
- Virginia Tech Carilion School of Medicine, Roanoke, Virginia.,Department of Statistics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - Robert G Gourdie
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Virginia Tech Carilion School of Medicine, Roanoke, Virginia.,Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - James W Smyth
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Virginia Tech Carilion School of Medicine, Roanoke, Virginia.,Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - Steven Poelzing
- Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, Virginia.,Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Roanoke, Virginia.,Virginia Tech Carilion School of Medicine, Roanoke, Virginia.,Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
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24
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Niewinski P, Walczak T, Królicki T, Kudla T, Jagielski D, Nowak K, Josiak K, Tubek S, Banasiak W, Ponikowski P. Re: Pacing, takotsubo syndrome, and transient rise of pacing threshold: What is the mechanism? Pacing Clin Electrophysiol 2020; 43:772-773. [DOI: 10.1111/pace.13977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 06/07/2020] [Indexed: 11/28/2022]
Affiliation(s)
- Piotr Niewinski
- Department of Heart DiseasesWroclaw Medical University Wroclaw Poland
| | - Tomasz Walczak
- Department of Heart DiseasesWroclaw Medical University Wroclaw Poland
- 4th Military Hospital Wroclaw Poland
| | - Tomasz Królicki
- Department of Heart DiseasesWroclaw Medical University Wroclaw Poland
| | - Tobiasz Kudla
- Department of Heart DiseasesWroclaw Medical University Wroclaw Poland
| | | | - Krzysztof Nowak
- Department of Heart DiseasesWroclaw Medical University Wroclaw Poland
| | - Krystian Josiak
- Department of Heart DiseasesWroclaw Medical University Wroclaw Poland
- 4th Military Hospital Wroclaw Poland
| | - Stanisław Tubek
- Department of Heart DiseasesWroclaw Medical University Wroclaw Poland
| | | | - Piotr Ponikowski
- Department of Heart DiseasesWroclaw Medical University Wroclaw Poland
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25
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Nowak MB, Greer-Short A, Wan X, Wu X, Deschênes I, Weinberg SH, Poelzing S. Intercellular Sodium Regulates Repolarization in Cardiac Tissue with Sodium Channel Gain of Function. Biophys J 2020; 118:2829-2843. [PMID: 32402243 DOI: 10.1016/j.bpj.2020.04.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 03/26/2020] [Accepted: 04/10/2020] [Indexed: 11/30/2022] Open
Abstract
In cardiac myocytes, action potentials are initiated by an influx of sodium (Na+) ions via voltage-gated Na+ channels. Na+ channel gain of function (GOF), arising in both inherited conditions associated with mutation in the gene encoding the Na+ channel and acquired conditions associated with heart failure, ischemia, and atrial fibrillation, enhance Na+ influx, generating a late Na+ current that prolongs action potential duration (APD) and triggering proarrhythmic early afterdepolarizations (EADs). Recent studies have shown that Na+ channels are highly clustered at the myocyte intercalated disk, facilitating formation of Na+ nanodomains in the intercellular cleft between cells. Simulations from our group have recently predicted that narrowing the width of the intercellular cleft can suppress APD prolongation and EADs in the presence of Na+ channel mutations because of increased intercellular cleft Na+ ion depletion. In this study, we investigate the effects of modulating multiple extracellular spaces, specifically the intercellular cleft and bulk interstitial space, in a novel computational model and experimentally via osmotic agents albumin, dextran 70, and mannitol. We perform optical mapping and transmission electron microscopy in a drug-induced (sea anemone toxin, ATXII) Na+ channel GOF isolated heart model and modulate extracellular spaces via osmotic agents. Single-cell patch-clamp experiments confirmed that the osmotic agents individually do not enhance late Na+ current. Both experiments and simulations are consistent with the conclusion that intercellular cleft narrowing or expansion regulates APD prolongation; in contrast, modulating the bulk interstitial space has negligible effects on repolarization. Thus, we predict that intercellular cleft Na+ nanodomain formation and collapse critically regulates cardiac repolarization in the setting of Na+ channel GOF.
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Affiliation(s)
- Madison B Nowak
- Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio; Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia
| | - Amara Greer-Short
- Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio; Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - Xiaoping Wan
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, Ohio; Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio
| | - Xiaobo Wu
- Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; Fralin Biomedical Research Institute at Virginia Tech Carilion, Virginia Polytechnic Institute and State University, Roanoke, Virginia
| | - Isabelle Deschênes
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, Ohio; Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio
| | - Seth H Weinberg
- Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio; Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia.
| | - Steven Poelzing
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Virginia Polytechnic Institute and State University, Roanoke, Virginia; Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia.
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26
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Wei N, Tolkacheva EG. Interplay between ephaptic coupling and complex geometry of border zone during acute myocardial ischemia: Effect on arrhythmogeneity. CHAOS (WOODBURY, N.Y.) 2020; 30:033111. [PMID: 32237767 DOI: 10.1063/1.5134447] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 02/12/2020] [Indexed: 06/11/2023]
Abstract
Acute myocardial ischemia is an imbalance between myocardial blood supply and demand, which is caused by the cessation of blood flow within the heart resulting from an obstruction in one of the major coronary arteries. A severe blockage may result in a region of nonperfused tissue known as ischemic core (IC). As a result, a border zone (BZ) between perfused and nonperfused regions is created due to differences in blood and oxygen supplies. Recent experimental findings reveal a complex "finger-like" geometry in BZ; however, its effect on arrhythmogenicity is not clear. Ephaptic coupling, which relies on the intercalated disk between cell ends, has been suggested to play an active role in mediating intercellular electrical communication when gap junctions are impaired. In this paper, we explored the interplay between ephaptic coupling and the geometry of BZ on action potential propagation across the ischemic region. Our study shows that ephaptic coupling can greatly suppress the occurrence of a conduction block, which points to its beneficial effect. The beneficial effect of ephaptic coupling is more evident in BZ with the "finger-like" geometry. In addition, the complex geometry of BZ, i.e., more frequent, deeper, and wider "fingers," promotes the conduction through the ischemic region. In contrast, the larger size of IC impedes the cardiac conduction across the ischemic region. Our results also show that ephaptic coupling promotes the impact of the complex geometry of BZ on signal propagation; however, it inhibits the impact of IC size.
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Affiliation(s)
- Ning Wei
- Department of Mathematics, Purdue University, West Lafayette, Indiana 47907, USA
| | - Elena G Tolkacheva
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
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27
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Jæger KH, Edwards AG, McCulloch A, Tveito A. Properties of cardiac conduction in a cell-based computational model. PLoS Comput Biol 2019; 15:e1007042. [PMID: 31150383 PMCID: PMC6561587 DOI: 10.1371/journal.pcbi.1007042] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2018] [Revised: 06/12/2019] [Accepted: 04/23/2019] [Indexed: 11/18/2022] Open
Abstract
The conduction of electrical signals through cardiac tissue is essential for maintaining the function of the heart, and conduction abnormalities are known to potentially lead to life-threatening arrhythmias. The properties of cardiac conduction have therefore been the topic of intense study for decades, but a number of questions related to the mechanisms of conduction still remain unresolved. In this paper, we demonstrate how the so-called EMI model may be used to study some of these open questions. In the EMI model, the extracellular space, the cell membrane, the intracellular space and the cell connections are all represented as separate parts of the computational domain, and the model therefore allows for study of local properties that are hard to represent in the classical homogenized bidomain or monodomain models commonly used to study cardiac conduction. We conclude that a non-uniform sodium channel distribution increases the conduction velocity and decreases the time delays over gap junctions of reduced coupling in the EMI model simulations. We also present a theoretical optimal cell length with respect to conduction velocity and consider the possibility of ephaptic coupling (i.e. cell-to-cell coupling through the extracellular potential) acting as an alternative or supporting mechanism to gap junction coupling. We conclude that for a non-uniform distribution of sodium channels and a sufficiently small intercellular distance, ephaptic coupling can influence the dynamics of the sodium channels and potentially provide cell-to-cell coupling when the gap junction connection is absent. The electrochemical wave traversing the heart during every beat is essential for cardiac pumping function and supply of blood to the body. Understanding the stability of this wave is crucial to understanding how lethal arrhythmias are generated. Despite this importance, our knowledge of the physical determinants of wave propagation are still evolving. One particular challenge has been the lack of accurate mathematical models of conduction at the cellular level. Because cardiac muscle is an electrical syncytium, in which direct charge transfer between cells drives wave propagation, classical bidomain and monodomain tissue models employ a homogenized approximation of this process. This approximation is not valid at the length scale of single cells, and prevents any analysis of how cellular structures impact cardiac conduction. Instead, so-called microdomain models must be used for these questions. Here we utilize a recently developed modelling framework that is well suited to represent small collections of cells. By applying this framework, we show that concentration of sodium channels at the longitudinal borders of myocytes accelerates cardiac conduction. We also demonstrate that when juxtaposed cells are sufficiently close, this non-uniform distribution induces large ephaptic currents, which contribute to intercellular coupling.
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Affiliation(s)
| | | | - Andrew McCulloch
- Department of Bioengineering, University of California, San Diego, California, United States of America
| | - Aslak Tveito
- Simula Research Laboratory, Oslo, Norway
- * E-mail:
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Jensen CF, Bartels ED, Braunstein TH, Nielsen LB, Holstein‐Rathlou N, Axelsen LN, Nielsen MS. Acute intramyocardial lipid accumulation in rats does not slow cardiac conduction per se. Physiol Rep 2019; 7:e14049. [PMID: 30968589 PMCID: PMC6456446 DOI: 10.14814/phy2.14049] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 03/12/2019] [Accepted: 03/12/2019] [Indexed: 01/14/2023] Open
Abstract
Diabetic patients suffer from both cardiac lipid accumulation and an increased risk of arrhythmias and sudden cardiac death. This correlation suggests a link between diabetes induced cardiac steatosis and electrical abnormalities, however, the underlying mechanism remains unknown. We previously showed that cardiac conduction velocity slows in Zucker diabetic fatty rats and in fructose-fat fed rats, models that both exhibit prominent cardiac steatosis. The aim of this study was to investigate whether acute cardiac lipid accumulation reduces conduction velocity per se. Cardiac lipid accumulation was induced acutely by perfusing isolated rat hearts with palmitate-glucose buffer, or subacutely by fasting rats overnight. Subsequently, longitudinal cardiac conduction velocity was measured in right ventricular tissue strips, and intramyocardial triglyceride and lipid droplet content was determined by thin layer chromatography and BODIPY staining, respectively. Perfusion with palmitate-glucose buffer significantly increased intramyocardial triglyceride levels compared to perfusion with glucose (2.16 ± 0.17 (n = 10) vs. 0.92 ± 0.33 nmol/mg WW (n = 9), P < 0.01), but the number of lipid droplets was very low in both groups. Fasting of rats, however, resulted in both significantly elevated intramyocardial triglyceride levels compared to fed rats (3.27 ± 0.43 (n = 10) vs. 1.45 ± 0.24 nmol/mg WW (n = 10)), as well as a larger volume of lipid droplets (0.60 ± 0.13 (n = 10) vs. 0.21 ± 0.06% (n = 10), P < 0.05). There was no significant difference in longitudinal conduction velocity between palmitate-glucose perfused and control hearts (0.77 ± 0.025 (n = 10) vs. 0.75 m/sec ± 0.029 (n = 9)), or between fed and fasted rats (0.75 ± 0.042 m/sec (n = 10) vs. 0.79 ± 0.047 (n = 10)). In conclusion, intramyocardial lipid accumulation does not slow cardiac longitudinal conduction velocity per se. This is true for both increased intramyocardial triglyceride content, induced by palmitate-glucose perfusion, and increased intramyocardial triglyceride and lipid droplet content, generated by fasting.
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Affiliation(s)
- Christa F. Jensen
- Department of Biomedical SciencesFaculty of Health SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Emil D. Bartels
- Department of Clinical BiochemistryCopenhagen University Hospital RigshospitaletCopenhagenDenmark
| | - Thomas H. Braunstein
- Department of Biomedical SciencesFaculty of Health SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Lars B. Nielsen
- Department of Clinical BiochemistryCopenhagen University Hospital RigshospitaletCopenhagenDenmark
| | | | - Lene N. Axelsen
- Department of Biomedical SciencesFaculty of Health SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Morten Schak Nielsen
- Department of Biomedical SciencesFaculty of Health SciencesUniversity of CopenhagenCopenhagenDenmark
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29
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Cartoski MJ, Nikolov PP, Prakosa A, Boyle PM, Spevak PJ, Trayanova NA. Computational Identification of Ventricular Arrhythmia Risk in Pediatric Myocarditis. Pediatr Cardiol 2019; 40:857-864. [PMID: 30840104 PMCID: PMC6451890 DOI: 10.1007/s00246-019-02082-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2018] [Accepted: 02/27/2019] [Indexed: 12/11/2022]
Abstract
Children with myocarditis have increased risk of ventricular tachycardia (VT) due to myocardial inflammation and remodeling. There is currently no accepted method for VT risk stratification in this population. We hypothesized that personalized models developed from cardiac late gadolinium enhancement magnetic resonance imaging (LGE-MRI) could determine VT risk in patients with myocarditis using a previously-validated protocol. Personalized three-dimensional computational cardiac models were reconstructed from LGE-MRI scans of 12 patients diagnosed with myocarditis. Four patients with clinical VT and eight patients without VT were included in this retrospective analysis. In each model, we incorporated a personalized spatial distribution of fibrosis and myocardial fiber orientations. Then, VT inducibility was assessed in each model by pacing rapidly from 26 sites distributed throughout both ventricles. Sustained reentrant VT was induced from multiple pacing sites in all patients with clinical VT. In the eight patients without clinical VT, we were unable to induce sustained reentry in our simulations using rapid ventricular pacing. Application of our non-invasive approach in children with myocarditis has the potential to correctly identify those at risk for developing VT.
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Affiliation(s)
- Mark J Cartoski
- Divison of Pediatric Cardiology, Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - Plamen P Nikolov
- Institute for Computational Medicine and Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Adityo Prakosa
- Institute for Computational Medicine and Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Patrick M Boyle
- Institute for Computational Medicine and Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Philip J Spevak
- Divison of Pediatric Cardiology, Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Natalia A Trayanova
- Institute for Computational Medicine and Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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30
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The efficiency of heart protection with HTK or HTK-N depending on the type of ischemia. Bioelectrochemistry 2019; 125:58-69. [DOI: 10.1016/j.bioelechem.2018.09.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 08/23/2018] [Accepted: 09/17/2018] [Indexed: 11/19/2022]
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31
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George SA, Hoeker G, Calhoun PJ, Entz M, Raisch TB, King DR, Khan M, Baker C, Gourdie RG, Smyth JW, Nielsen MS, Poelzing S. Modulating cardiac conduction during metabolic ischemia with perfusate sodium and calcium in guinea pig hearts. Am J Physiol Heart Circ Physiol 2019; 316:H849-H861. [PMID: 30707595 DOI: 10.1152/ajpheart.00083.2018] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We previously demonstrated that altering extracellular sodium (Nao) and calcium (Cao) can modulate a form of electrical communication between cardiomyocytes termed "ephaptic coupling" (EpC), especially during loss of gap junction coupling. We hypothesized that altering Nao and Cao modulates conduction velocity (CV) and arrhythmic burden during ischemia. Electrophysiology was quantified by optically mapping Langendorff-perfused guinea pig ventricles with modified Nao (147 or 155 mM) and Cao (1.25 or 2.0 mM) during 30 min of simulated metabolic ischemia (pH 6.5, anoxia, aglycemia). Gap junction-adjacent perinexal width ( WP), a candidate cardiac ephapse, and connexin (Cx)43 protein expression and Cx43 phosphorylation at S368 were quantified by transmission electron microscopy and Western immunoblot analysis, respectively. Metabolic ischemia slowed CV in hearts perfused with 147 mM Nao and 2.0 mM Cao; however, theoretically increasing EpC with 155 mM Nao was arrhythmogenic, and CV could not be measured. Reducing Cao to 1.25 mM expanded WP, as expected during ischemia, consistent with reduced EpC, but attenuated CV slowing while delaying arrhythmia onset. These results were further supported by osmotically reducing WP with albumin, which exacerbated CV slowing and increased early arrhythmias during ischemia, whereas mannitol expanded WP, permitted conduction, and delayed the onset of arrhythmias. Cx43 expression patterns during the various interventions insufficiently correlated with observed CV changes and arrhythmic burden. In conclusion, decreasing perfusate calcium during metabolic ischemia enhances perinexal expansion, attenuates conduction slowing, and delays arrhythmias. Thus, perinexal expansion may be cardioprotective during metabolic ischemia. NEW & NOTEWORTHY This study demonstrates, for the first time, that modulating perfusate ion composition can alter cardiac electrophysiology during simulated metabolic ischemia.
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Affiliation(s)
- Sharon A George
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University , Blacksburg, Virginia.,Center for Heart and Reparative Medicine Research, Virginia Tech Carilion Research Institute , Roanoke, Virginia
| | - Gregory Hoeker
- Center for Heart and Reparative Medicine Research, Virginia Tech Carilion Research Institute , Roanoke, Virginia
| | - Patrick J Calhoun
- Center for Heart and Reparative Medicine Research, Virginia Tech Carilion Research Institute , Roanoke, Virginia.,Department of Biological Sciences, Virginia Polytechnic Institute and State University , Blacksburg, Virginia
| | - Michael Entz
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University , Blacksburg, Virginia.,Center for Heart and Reparative Medicine Research, Virginia Tech Carilion Research Institute , Roanoke, Virginia
| | - Tristan B Raisch
- Center for Heart and Reparative Medicine Research, Virginia Tech Carilion Research Institute , Roanoke, Virginia.,Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University , Blacksburg, Virginia
| | - D Ryan King
- Center for Heart and Reparative Medicine Research, Virginia Tech Carilion Research Institute , Roanoke, Virginia.,Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University , Blacksburg, Virginia
| | - Momina Khan
- Department of Human Food Nutrition and Exercise, Virginia Polytechnic Institute and State University , Blacksburg, Virginia
| | - Chandra Baker
- Center for Heart and Reparative Medicine Research, Virginia Tech Carilion Research Institute , Roanoke, Virginia
| | - Robert G Gourdie
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University , Blacksburg, Virginia.,Center for Heart and Reparative Medicine Research, Virginia Tech Carilion Research Institute , Roanoke, Virginia
| | - James W Smyth
- Center for Heart and Reparative Medicine Research, Virginia Tech Carilion Research Institute , Roanoke, Virginia.,Department of Biological Sciences, Virginia Polytechnic Institute and State University , Blacksburg, Virginia
| | - Morten S Nielsen
- Department of Biomedical Sciences, University of Copenhagen , Copenhagen , Denmark
| | - Steven Poelzing
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University , Blacksburg, Virginia.,Center for Heart and Reparative Medicine Research, Virginia Tech Carilion Research Institute , Roanoke, Virginia.,Translational Biology, Medicine, and Health Graduate Program, Virginia Polytechnic Institute and State University , Blacksburg, Virginia
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32
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Gourdie RG. The Cardiac Gap Junction has Discrete Functions in Electrotonic and Ephaptic Coupling. Anat Rec (Hoboken) 2018; 302:93-100. [PMID: 30565418 DOI: 10.1002/ar.24036] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 07/10/2018] [Accepted: 07/17/2018] [Indexed: 12/31/2022]
Abstract
Connexin43-formed gap junctions have long been thought to contribute to cardiac conduction in the mammalian ventricle by providing direct electrotonic connectivity between the cytoplasms of neighboring cardiomyocytes. However, accumulating data from studies of non-mammalian hearts, Connexin 43 (Cx43) knockout mice and human Cx43 mutations have raised questions as to whether gap junctions are the sole means by which electrical coupling between cardiomyocytes is accomplished. Computational and experimental work over the last decade have indicated that intercellular propagation of action potentials in the heart may involve both electrotonic and ephaptic contributions-in what has been dubbed "mixed-mode" conduction. Interestingly, the Cx43 gap junction may provide a common structural platform in mammals that facilitates the operation of these two mechanisms. In addition to gap junction channels functioning in an electrotonic role, the perinexus region at the edge of gap junctions may be provide a niche for voltage-gated sodium channels from neighboring cells to be in sufficiently close proximity to enable ephaptic transmission of action potential. A novel role has recently been identified in this potential ephaptic mechanism for inter-membrane adhesion mediated by the beta subunit (beta1/Scn1b) of the sodium channel. The new perspective of the operational redundancy that is built into cardiac electrical connectivity could provide new understanding of arrhythmia mechanisms and holds the promise for new approach to anti-arrhythmic therapy. Anat Rec, 302:93-100, 2019. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Robert G Gourdie
- Center for Heart and Regenerative Medicine, Virginia Tech Carilion Research Institute, Virginia Tech, Roanoke, Virginia, 24016.,Department of Emergency Medicine, Virginia Tech Carilion School of Medicine, Virginia Tech, Roanoke, Virginia, 24016.,Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, Virginia, 24061
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33
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The role of the gap junction perinexus in cardiac conduction: Potential as a novel anti-arrhythmic drug target. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2018; 144:41-50. [PMID: 30241906 DOI: 10.1016/j.pbiomolbio.2018.08.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 07/09/2018] [Accepted: 08/10/2018] [Indexed: 12/16/2022]
Abstract
Cardiovascular disease remains the single largest cause of natural death in the United States, with a significant cause of mortality associated with cardiac arrhythmias. Presently, options for treating and preventing myocardial electrical dysfunction, including sudden cardiac death, are limited. Recent studies have indicated that conduction of electrical activation in the heart may have an ephaptic component, wherein intercellular coupling occurs via electrochemical signaling across narrow extracellular clefts between cardiomyocytes. The perinexus is a 100-200 nm-wide stretch of closely apposed membrane directly adjacent to connexin 43 gap junctions. Electron and super-resolution microscopy studies, as well as biochemical analyses, have provided evidence that perinexal nanodomains may be candidate structures for facilitating ephaptic coupling. This work has included characterization of the perinexus as a region of close inter-membrane contact between cardiomyocytes (<30 nm) containing dense clusters of voltage-gated sodium channels. Here, we review what is known about perinexal structure and function and the potential that the perinexus may have novel and pivotal roles in disorders of cardiac conduction. Of particular interest is the prospect that cell adhesion mediated by the cardiac sodium channel β subunit (Scn1b) may be a novel anti-arrhythmic target.
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34
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Radwański PB, Johnson CN, Györke S, Veeraraghavan R. Cardiac Arrhythmias as Manifestations of Nanopathies: An Emerging View. Front Physiol 2018; 9:1228. [PMID: 30233404 PMCID: PMC6131669 DOI: 10.3389/fphys.2018.01228] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 08/14/2018] [Indexed: 12/21/2022] Open
Abstract
A nanodomain is a collection of proteins localized within a specialized, nanoscale structural environment, which can serve as the functional unit of macroscopic physiologic processes. We are beginning to recognize the key roles of cardiomyocyte nanodomains in essential processes of cardiac physiology such as electrical impulse propagation and excitation–contraction coupling (ECC). There is growing appreciation of nanodomain dysfunction, i.e., nanopathy, as a mechanistic driver of life-threatening arrhythmias in a variety of pathologies. Here, we offer an overview of current research on the role of nanodomains in cardiac physiology with particular emphasis on: (1) sodium channel-rich nanodomains within the intercalated disk that participate in cell-to-cell electrical coupling and (2) dyadic nanodomains located along transverse tubules that participate in ECC. The beat to beat function of cardiomyocytes involves three phases: the action potential, the calcium transient, and mechanical contraction/relaxation. In all these phases, cell-wide function results from the aggregation of the stochastic function of individual proteins. While it has long been known that proteins that exist in close proximity influence each other’s function, it is increasingly appreciated that there exist nanoscale structures that act as functional units of cardiac biophysical phenomena. Termed nanodomains, these structures are collections of proteins, localized within specialized nanoscale structural environments. The nano-environments enable the generation of localized electrical and/or chemical gradients, thereby conferring unique functional properties to these units. Thus, the function of a nanodomain is determined by its protein constituents as well as their local structural environment, adding an additional layer of complexity to cardiac biology and biophysics. However, with the emergence of experimental techniques that allow direct investigation of structure and function at the nanoscale, our understanding of cardiac physiology and pathophysiology at these scales is rapidly advancing. Here, we will discuss the structure and functions of multiple cardiomyocyte nanodomains, and novel strategies that target them for the treatment of cardiac arrhythmias.
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Affiliation(s)
- Przemysław B Radwański
- Bob and Corinne Frick Center for Heart Failure and Arrhythmia, The Ohio State University Wexner Medical Center, Columbus, OH, United States.,Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, United States.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, United States.,Division of Pharmacy Practice and Science, College of Pharmacy, The Ohio State University, Columbus, OH, United States
| | - Christopher N Johnson
- Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, United States.,Vanderbilt Center for Arrhythmia Research and Therapeutics, Nashville, TN, United States
| | - Sándor Györke
- Bob and Corinne Frick Center for Heart Failure and Arrhythmia, The Ohio State University Wexner Medical Center, Columbus, OH, United States.,Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, United States.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Rengasayee Veeraraghavan
- Bob and Corinne Frick Center for Heart Failure and Arrhythmia, The Ohio State University Wexner Medical Center, Columbus, OH, United States.,Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, United States.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, United States.,Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States
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35
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Delmar M, Laird DW, Naus CC, Nielsen MS, Verselis VK, White TW. Connexins and Disease. Cold Spring Harb Perspect Biol 2018; 10:cshperspect.a029348. [PMID: 28778872 DOI: 10.1101/cshperspect.a029348] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Inherited or acquired alterations in the structure and function of connexin proteins have long been associated with disease. In the present work, we review current knowledge on the role of connexins in diseases associated with the heart, nervous system, cochlea, and skin, as well as cancer and pleiotropic syndromes such as oculodentodigital dysplasia (ODDD). Although incomplete by virtue of space and the extent of the topic, this review emphasizes the fact that connexin function is not only associated with gap junction channel formation. As such, both canonical and noncanonical functions of connexins are fundamental components in the pathophysiology of multiple connexin related disorders, many of them highly debilitating and life threatening. Improved understanding of connexin biology has the potential to advance our understanding of mechanisms, diagnosis, and treatment of disease.
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Affiliation(s)
- Mario Delmar
- The Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, New York 10016
| | - Dale W Laird
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario N6A5C1, Canada
| | - Christian C Naus
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Morten S Nielsen
- Department of Biological Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark
| | - Vytautas K Verselis
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, New York 10461
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York 11790
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36
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Myers CM, Kim JS, Florian JP. Effects of repeated long-duration water immersions on skeletal muscle performance in well-trained male divers. Eur J Appl Physiol 2018; 118:2065-2076. [PMID: 30003382 DOI: 10.1007/s00421-018-3928-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 06/30/2018] [Indexed: 11/26/2022]
Abstract
PURPOSE The objective of this study was to examine the effects of repeated long-duration water immersions (WI)s at 1.35 atmospheres absolute (ATA) on neuromuscular performance in load bearing and non-load bearing muscle groups. METHODS During a dive week (DW), fifteen well-trained male divers completed five consecutive 6-h resting dives with 18-h surface intervals while breathing compressed air at 1.35 ATA. Skeletal muscle performance assessments occurred immediately before and after each WI, and 24 and 72 h after the final WI. Exercise assessments included maximum voluntary isometric contraction (MVIC), maximal isokinetic (IK) contraction, maximum handgrip strength (MHG). Surface electromyography measured neuromuscular activation of the quadriceps, biceps brachii (BB), and brachioradialis. RESULTS MVIC torque of knee extensors and BB decreased by 6% (p = 0.001) and 2% (p = 0.014), respectively, by WI 3. Maximal IK torque of knee extensors increased by 11 and 5% post-WI on WIs 3 and 5 (p < 0.001) with greater neuromuscular activation post-WI than pre-WI (p < 0.001). Maximum IK elbow flexion torque did not change throughout the DW with BB neuromuscular activation greater post-WI than pre-WI (p < 0.001). MHG force output was 4% greater post-WI than pre-WI (p < 0.001) with increased brachioradialis activation through 72-h post-WI (p < 0.001). All muscle performance metrics returned baseline levels by 72-h post-WI. CONCLUSION Our findings indicate that repeated WIs caused noticeable decrements in neuromuscular activation and performance of load bearing muscles on WI 3 while full recovery was observed by 72-h post-WI.
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Affiliation(s)
- Christopher M Myers
- Department of Nutrition, Food and Exercise Sciences, Florida State University, Tallahassee, FL, USA
| | - Jeong-Su Kim
- Department of Nutrition, Food and Exercise Sciences, Florida State University, Tallahassee, FL, USA
| | - John P Florian
- Navy Experimental Diving Unit, 321 Bullfinch Rd., Panama City, FL, 32407, USA.
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37
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Raisch TB, Yanoff MS, Larsen TR, Farooqui MA, King DR, Veeraraghavan R, Gourdie RG, Baker JW, Arnold WS, AlMahameed ST, Poelzing S. Intercalated Disk Extracellular Nanodomain Expansion in Patients With Atrial Fibrillation. Front Physiol 2018; 9:398. [PMID: 29780324 PMCID: PMC5945828 DOI: 10.3389/fphys.2018.00398] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 04/04/2018] [Indexed: 12/29/2022] Open
Abstract
Aims: Atrial fibrillation (AF) is the most common sustained arrhythmia. Previous evidence in animal models suggests that the gap junction (GJ) adjacent nanodomain – perinexus – is a site capable of independent intercellular communication via ephaptic transmission. Perinexal expansion is associated with slowed conduction and increased ventricular arrhythmias in animal models, but has not been studied in human tissue. The purpose of this study was to characterize the perinexus in humans and determine if perinexal expansion associates with AF. Methods: Atrial appendages from 39 patients (pts) undergoing cardiac surgery were fixed for immunofluorescence and transmission electron microscopy (TEM). Intercalated disk distribution of the cardiac sodium channel Nav1.5, its β1 subunit, and connexin43 (C×43) was determined by confocal immunofluorescence. Perinexal width (Wp) from TEM was manually segmented by two blinded observers using ImageJ software. Results: Nav1.5, β1, and C×43 are co-adjacent within intercalated disks of human atria, consistent with perinexal protein distributions in ventricular tissue of other species. TEM revealed that the GJ adjacent intermembrane separation in an individual perinexus does not change at distances greater than 30 nm from the GJ edge. Importantly, Wp is significantly wider in patients with a history of AF than in patients with no history of AF by approximately 3 nm, and Wp correlates with age (R = 0.7, p < 0.05). Conclusion: Human atrial myocytes have voltage-gated sodium channels in a dynamic intercellular cleft adjacent to GJs that is consistent with previous descriptions of the perinexus. Further, perinexal width is greater in patients with AF undergoing cardiac surgery than in those without.
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Affiliation(s)
- Tristan B Raisch
- Virginia Tech Carilion Research Institute, Center for Heart and Regenerative Medicine, Virginia Tech, Blacksburg, VA, United States.,Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, VA, United States
| | - Matthew S Yanoff
- Virginia Tech Carilion Research Institute, Center for Heart and Regenerative Medicine, Virginia Tech, Blacksburg, VA, United States.,Virginia Tech Carilion School of Medicine, Roanoke, VA, United States
| | - Timothy R Larsen
- Department of Medicine, Section of Cardiology, Center for Atrial Fibrillation, Carilion Clinic, Roanoke, VA, United States
| | - Mohammed A Farooqui
- Department of Medicine, Section of Cardiology, Center for Atrial Fibrillation, Carilion Clinic, Roanoke, VA, United States
| | - D Ryan King
- Virginia Tech Carilion Research Institute, Center for Heart and Regenerative Medicine, Virginia Tech, Blacksburg, VA, United States.,Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, VA, United States
| | - Rengasayee Veeraraghavan
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States.,The Bob and Corrine Frick Center for Heart Failure and Arrhythmia, The Ohio State University, Columbus, OH, United States.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Robert G Gourdie
- Virginia Tech Carilion Research Institute, Center for Heart and Regenerative Medicine, Virginia Tech, Blacksburg, VA, United States.,Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA, United States
| | - Joseph W Baker
- Department of Surgery, Carilion Clinic, Roanoke, VA, United States
| | - William S Arnold
- Department of Surgery, Carilion Clinic, Roanoke, VA, United States
| | - Soufian T AlMahameed
- Department of Medicine, Section of Cardiology, Center for Atrial Fibrillation, Carilion Clinic, Roanoke, VA, United States
| | - Steven Poelzing
- Virginia Tech Carilion Research Institute, Center for Heart and Regenerative Medicine, Virginia Tech, Blacksburg, VA, United States.,Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, VA, United States.,Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA, United States
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38
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Entz M, King DR, Poelzing S. Design and validation of a tissue bath 3-D printed with PLA for optically mapping suspended whole heart preparations. Am J Physiol Heart Circ Physiol 2017; 313:H1190-H1198. [PMID: 28939646 DOI: 10.1152/ajpheart.00150.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 09/11/2017] [Accepted: 09/13/2017] [Indexed: 11/22/2022]
Abstract
With the sudden increase in affordable manufacturing technologies, the relationship between experimentalists and the designing process for laboratory equipment is rapidly changing. While experimentalists are still dependent on engineers and manufacturers for precision electrical, mechanical, and optical equipment, it has become a realistic option for in house manufacturing of other laboratory equipment with less precise design requirements. This is possible due to decreasing costs and increasing functionality of desktop three-dimensional (3-D) printers and 3-D design software. With traditional manufacturing methods, iterative design processes are expensive and time consuming, and making more than one copy of a custom piece of equipment is prohibitive. Here, we provide an overview to design a tissue bath and stabilizer for a customizable, suspended, whole heart optical mapping apparatus that can be produced significantly faster and less expensive than conventional manufacturing techniques. This was accomplished through a series of design steps to prevent fluid leakage in the areas where the optical imaging glass was attached to the 3-D printed bath. A combination of an acetone dip along with adhesive was found to create a water tight bath. Optical mapping was used to quantify cardiac conduction velocity and action potential duration to compare 3-D printed baths to a bath that was designed and manufactured in a machine shop. Importantly, the manufacturing method did not significantly affect conduction, action potential duration, or contraction, suggesting that 3-D printed baths are equally effective for optical mapping experiments.NEW & NOTEWORTHY This article details three-dimensional printable equipment for use in suspended whole heart optical mapping experiments. This equipment is less expensive than conventional manufactured equipment as well as easily customizable to the experimentalist. The baths can be waterproofed using only a three-dimensional printer, acetone, a glass microscope slide, c-clamps, and adhesive.
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Affiliation(s)
- Michael Entz
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia.,Virginia Tech Carilion Research Institute and Center for Heart and Regenerative Medicine, Roanoke, Virginia; and
| | - D Ryan King
- Virginia Tech Carilion Research Institute and Center for Heart and Regenerative Medicine, Roanoke, Virginia; and.,Graduate program in Transnational Biology, Medicine and Health, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - Steven Poelzing
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; .,Virginia Tech Carilion Research Institute and Center for Heart and Regenerative Medicine, Roanoke, Virginia; and.,Graduate program in Transnational Biology, Medicine and Health, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
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Weinberg SH. Ephaptic coupling rescues conduction failure in weakly coupled cardiac tissue with voltage-gated gap junctions. CHAOS (WOODBURY, N.Y.) 2017; 27:093908. [PMID: 28964133 DOI: 10.1063/1.4999602] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Electrical conduction in cardiac tissue is usually considered to be primarily facilitated by gap junctions, providing a pathway between the intracellular spaces of neighboring cells. However, recent studies have highlighted the role of coupling via extracellular electric fields, also known as ephaptic coupling, particularly in the setting of reduced gap junction expression. Further, in the setting of reduced gap junctional coupling, voltage-dependent gating of gap junctions, an oft-neglected biophysical property in computational studies, produces a positive feedback that promotes conduction failure. We hypothesized that ephaptic coupling can break the positive feedback loop and rescue conduction failure in weakly coupled cardiac tissue. In a computational tissue model incorporating voltage-gated gap junctions and ephaptic coupling, we demonstrate that ephaptic coupling can rescue conduction failure in weakly coupled tissue. Further, ephaptic coupling increased conduction velocity in weakly coupled tissue, and importantly, reduced the minimum gap junctional coupling necessary for conduction, most prominently at fast pacing rates. Finally, we find that, although neglecting gap junction voltage-gating results in negligible differences in well coupled tissue, more significant differences occur in weakly coupled tissue, greatly underestimating the minimal gap junctional coupling that can maintain conduction. Our study suggests that ephaptic coupling plays a conduction-preserving role, particularly at rapid heart rates.
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Affiliation(s)
- S H Weinberg
- Virginia Commonwealth University, 401 West Main Street, Richmond, Virginia 23284, USA
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40
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Tse G, Liu T, Li G, Keung W, Yeo JM, Fiona Chan YW, Yan BP, Chan YS, Wong SH, Li RA, Zhao J, Wu WKK, Wong WT. Effects of pharmacological gap junction and sodium channel blockade on S1S2 restitution properties in Langendorff-perfused mouse hearts. Oncotarget 2017; 8:85341-85352. [PMID: 29156723 PMCID: PMC5689613 DOI: 10.18632/oncotarget.19675] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 05/23/2017] [Indexed: 12/19/2022] Open
Abstract
Gap junctions and sodium channels are the major molecular determinants of normal and abnormal electrical conduction through the myocardium, however, their exact contributions to arrhythmogenesis are unclear. We examined conduction and recovery properties of regular (S1) and extrasystolic (S2) action potentials (APs), S1S2 restitution and ventricular arrhythmogenicity using the gap junction and sodium channel inhibitor heptanol (2 mM) in Langendorff-perfused mouse hearts (n=10). Monophasic action potential recordings obtained during S1S2 pacing showed that heptanol increased the proportion of hearts showing inducible ventricular tachycardia (0/10 vs. 5/8 hearts (Fisher’s exact test, P < 0.05), prolonged activation latencies of S1 and S2 APs, thereby decreasing S2/S1 activation latency ratio (ANOVA, P < 0.05) despite prolonged ventricular effective refractory period (VERP). It did not alter S1 action potential duration at 90% repolarization (APD90) but prolonged S2 APD90 (P < 0.05), thereby increasing S2/S1 APD90 ratio (P < 0.05). It did not alter maximum conduction velocity (CV) restitution gradient or maximum CV reductions but decreased the restitution time constant (P < 0.05). It increased maximal APD90 restitution gradient (P < 0.05) without altering critical diastolic interval or maximum APD90 reductions. Pro-arrhythmic effects of 2 mM heptanol are explicable by delayed conduction and abnormal electrical restitution. We concluded that gap junctions modulated via heptanol (0.05 mM) increased arrhythmogenicity through a delay in conduction, while sodium channel inhibition by a higher concentration of heptanol (2 mM) increased arrhythmogenicity via additional mechanisms, such as abnormalities in APDs and CV restitution.
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Affiliation(s)
- Gary Tse
- Department of Medicine and Therapeutics, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China.,Li Ka Shing Institute of Health Sciences, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China
| | - Tong Liu
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin, China
| | - Guangping Li
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin, China
| | - Wendy Keung
- Dr. Li Dak-Sum Research Centre, The University of Hong Kong-Karolinska Institutet Collaboration in Regenerative Medicine, Hong Kong, China
| | - Jie Ming Yeo
- Faculty of Medicine, Imperial College London, London, UK
| | | | - Bryan P Yan
- Department of Medicine and Therapeutics, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China
| | - Yat Sun Chan
- Department of Medicine and Therapeutics, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China
| | - Sunny Hei Wong
- Department of Medicine and Therapeutics, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China.,Li Ka Shing Institute of Health Sciences, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China
| | - Ronald A Li
- Ming Wai Lau Centre for Reparative Medicine, Karolinska Institutet, Solna, Sweden
| | - Jichao Zhao
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - William K K Wu
- Department of Anaesthesia and Intensive Care, State Key Laboratory of Digestive Disease, LKS Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Wing Tak Wong
- School of Life Sciences, Chinese University of Hong Kong, Hong Kong, China
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Greer-Short A, George SA, Poelzing S, Weinberg SH. Revealing the Concealed Nature of Long-QT Type 3 Syndrome. Circ Arrhythm Electrophysiol 2017; 10:e004400. [PMID: 28213505 DOI: 10.1161/circep.116.004400] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 12/13/2016] [Indexed: 11/16/2022]
Abstract
BACKGROUND Gain-of-function mutations in the voltage-gated sodium channel (Nav1.5) are associated with the long-QT-3 (LQT3) syndrome. Nav1.5 is densely expressed at the intercalated disk, and narrow intercellular separation can modulate cell-to-cell coupling via extracellular electric fields and depletion of local sodium ion nanodomains. Models predict that significantly decreasing intercellular cleft widths slows conduction because of reduced sodium current driving force, termed "self-attenuation." We tested the novel hypothesis that self-attenuation can "mask" the LQT3 phenotype by reducing the driving force and late sodium current that produces early afterdepolarizations (EADs). METHODS AND RESULTS Acute interstitial edema was used to increase intercellular cleft width in isolated guinea pig heart experiments. In a drug-induced LQT3 model, acute interstitial edema exacerbated action potential duration prolongation and produced EADs, in particular, at slow pacing rates. In a computational cardiac tissue model incorporating extracellular electric field coupling, intercellular cleft sodium nanodomains, and LQT3-associated mutant channels, myocytes produced EADs for wide intercellular clefts, whereas for narrow clefts, EADs were suppressed. For both wide and narrow clefts, mutant channels were incompletely inactivated. However, for narrow clefts, late sodium current was reduced via self-attenuation, a protective negative feedback mechanism, masking EADs. CONCLUSIONS We demonstrated a novel mechanism leading to the concealing and revealing of EADs in LQT3 models. Simulations predict that this mechanism may operate independent of the specific mutation, suggesting that future therapies could target intercellular cleft separation as a compliment or alternative to sodium channels.
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Affiliation(s)
- Amara Greer-Short
- From the Virginia Tech Carilion Research Institute, Virginia Polytechnic Institute and State University, Roanoke (A.G.-S., S.A.G., S.P.); and Department of Biomedical Engineering, Virginia Commonwealth University, Richmond (S.H.W.)
| | - Sharon A George
- From the Virginia Tech Carilion Research Institute, Virginia Polytechnic Institute and State University, Roanoke (A.G.-S., S.A.G., S.P.); and Department of Biomedical Engineering, Virginia Commonwealth University, Richmond (S.H.W.)
| | - Steven Poelzing
- From the Virginia Tech Carilion Research Institute, Virginia Polytechnic Institute and State University, Roanoke (A.G.-S., S.A.G., S.P.); and Department of Biomedical Engineering, Virginia Commonwealth University, Richmond (S.H.W.).
| | - Seth H Weinberg
- From the Virginia Tech Carilion Research Institute, Virginia Polytechnic Institute and State University, Roanoke (A.G.-S., S.A.G., S.P.); and Department of Biomedical Engineering, Virginia Commonwealth University, Richmond (S.H.W.).
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42
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Tse G, Yeo JM, Tse V, Kwan J, Sun B. Gap junction inhibition by heptanol increases ventricular arrhythmogenicity by reducing conduction velocity without affecting repolarization properties or myocardial refractoriness in Langendorff-perfused mouse hearts. Mol Med Rep 2016; 14:4069-4074. [PMID: 27633494 PMCID: PMC5101880 DOI: 10.3892/mmr.2016.5738] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 07/18/2016] [Indexed: 12/31/2022] Open
Abstract
In the current study, arrhythmogenic effects of the gap junction inhibitor heptanol (0.05 mM) were examined in Langendorff-perfused mouse hearts. Monophasic action potential recordings were obtained from the left ventricular epicardium during right ventricular pacing. Regular activity was observed both prior and subsequent to application of heptanol in all of the 12 hearts studied during 8 Hz pacing. By contrast, induced ventricular tachycardia (VT) was observed after heptanol treatment in 6/12 hearts using a S1S2 protocol (Fisher's exact test; P<0.05). The arrhythmogenic effects of heptanol were associated with increased activation latencies from 13.2±0.6 to 19.4±1.3 msec (analysis of variance; P<0.001) and reduced conduction velocities (CVs) from 0.23±0.01 to 0.16±0.01 msec (analysis of variance; P<0.001) in an absence of alterations in action potential durations (ADPs) at x=90% (38.0±1.0 vs. 38.3±1.8 msec), 70% (16.8±1.0 vs. 19.5±0.9 msec), 50% (9.2±0.8 vs. 10.1±0.6 msec) or 30% (4.8±0.5 vs. 6.3±0.6 msec) repolarization (APDx) or in effective refractory period (ERPs) (39.6±1.9 vs. 40.6±3.0 msec) (all P>0.05). Consequently, excitation wavelengths (λ; CV x ERP) were reduced from 9.1±0.6 to 6.5±0.6 mm (P<0.01), however critical intervals for re‑excitation (APD90 ‑ ERP) were unaltered (‑1.1±2.4 vs. ‑2.3±1.8 msec; P>0.05). Together, these observations demonstrate for the first time, to the best of our knowledge, that inhibition of gap junctions alone using a low heptanol concentration (0.05 mM) was able to reduce CV, which alone was sufficient to permit the induction of VT using premature stimulation by reducing λ, which therefore appears central in the determination of arrhythmic tendency.
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Affiliation(s)
- Gary Tse
- Department of Medicine and Therapeutics, Chinese University of Hong Kong, Hong Kong, P.R. China
| | - Jie Ming Yeo
- Faculty of Medicine, Imperial College London, London SW7 2AZ, UK
| | - Vivian Tse
- Department of Physiology, McGill University, Montreal, QC H3G 1Y6, Canada
| | - Joseph Kwan
- Department of Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
| | - Bing Sun
- Department of Cardiology, Tongji University Affiliated Tongji Hospital, Shanghai 200065, P.R. China
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43
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Fhf2 gene deletion causes temperature-sensitive cardiac conduction failure. Nat Commun 2016; 7:12966. [PMID: 27701382 PMCID: PMC5059448 DOI: 10.1038/ncomms12966] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 08/22/2016] [Indexed: 12/21/2022] Open
Abstract
Fever is a highly conserved systemic response to infection dating back over 600 million years. Although conferring a survival benefit, fever can negatively impact the function of excitable tissues, such as the heart, producing cardiac arrhythmias. Here we show that mice lacking fibroblast growth factor homologous factor 2 (FHF2) have normal cardiac rhythm at baseline, but increasing core body temperature by as little as 3 °C causes coved-type ST elevations and progressive conduction failure that is fully reversible upon return to normothermia. FHF2-deficient cardiomyocytes generate action potentials upon current injection at 25 °C but are unexcitable at 40 °C. The absence of FHF2 accelerates the rate of closed-state and open-state sodium channel inactivation, which synergizes with temperature-dependent enhancement of inactivation rate to severely suppress cardiac sodium currents at elevated temperatures. Our experimental and computational results identify an essential role for FHF2 in dictating myocardial excitability and conduction that safeguards against temperature-sensitive conduction failure.
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44
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Veeraraghavan R, Lin J, Keener JP, Gourdie R, Poelzing S. Potassium channels in the Cx43 gap junction perinexus modulate ephaptic coupling: an experimental and modeling study. Pflugers Arch 2016; 468:1651-61. [PMID: 27510622 DOI: 10.1007/s00424-016-1861-2] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 06/27/2016] [Accepted: 07/25/2016] [Indexed: 12/01/2022]
Abstract
It was recently demonstrated that cardiac sodium channels (Nav1.5) localized at the perinexus, an intercalated disc (ID) nanodomain associated with gap junctions (GJ), may contribute to electrical coupling between cardiac myocytes via an ephaptic mechanism. Impairment of ephaptic coupling by acute interstitial edema (AIE)-induced swelling of the perinexus was associated with arrhythmogenic, anisotropic conduction slowing. Given that Kir2.1 has also recently been reported to localize at intercalated discs, we hypothesized that Kir2.1 channels may reside within the perinexus and that inhibiting them may mitigate arrhythmogenic conduction slowing observed during AIE. Using gated stimulated emission depletion (gSTED) and stochastic optical reconstruction microscopy (STORM) super-resolution microscopy, we indeed find that a significant proportion of Kir2.1 channels resides within the perinexus. Moreover, whereas Nav1.5 inhibition during AIE exacerbated arrhythmogenic conduction slowing, inhibiting Kir2.1 channels during AIE preferentially increased transverse conduction velocity-decreasing anisotropy and ameliorating arrhythmia risk compared to AIE alone. Comparison of our results with a nanodomain computer model identified enrichment of both Nav1.5 and Kir2.1 at intercalated discs as key factors underlying the experimental observations. We demonstrate that Kir2.1 channels are localized within the perinexus alongside Nav1.5 channels. Further, targeting Kir2.1 modulates intercellular coupling between cardiac myocytes, anisotropy of conduction, and arrhythmia propensity in a manner consistent with a role for ephaptic coupling in cardiac conduction. For over half a century, electrical excitation in the heart has been thought to occur exclusively via gap junction-mediated ionic current flow between cells. Further, excitation was thought to depend almost exclusively on sodium channels with potassium channels being involved mainly in returning the cell to rest. Here, we demonstrate that sodium and potassium channels co-reside within nanoscale domains at cell-to-cell contact sites. Experimental and computer modeling results suggest a role for these channels in electrical coupling between cardiac muscle cells via an ephaptic mechanism working in tandem with gap junctions. This new insight into the mechanism of cardiac electrical excitation could pave the way for novel therapies against cardiac rhythm disturbances.
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Affiliation(s)
- Rengasayee Veeraraghavan
- Virginia Tech Carilion Research Institute, and Center for Heart and Regenerative Medicine, Virginia Polytechnic University, 2 Riverside Circle, Roanoke, VA, 24016, USA.
| | - Joyce Lin
- Department of Mathematics, California Polytechnic State University, San Luis Obispo, CA, USA
| | - James P Keener
- Department of Mathematics, University of Utah, 155 South 1400 East, Salt Lake City, UT, 84112, USA
| | - Robert Gourdie
- Virginia Tech Carilion Research Institute, and Center for Heart and Regenerative Medicine, Virginia Polytechnic University, 2 Riverside Circle, Roanoke, VA, 24016, USA.
- School of Biomedical Engineering and Sciences, Virginia Polytechnic University, Blacksburg, VA, USA.
| | - Steven Poelzing
- Virginia Tech Carilion Research Institute, and Center for Heart and Regenerative Medicine, Virginia Polytechnic University, 2 Riverside Circle, Roanoke, VA, 24016, USA.
- School of Biomedical Engineering and Sciences, Virginia Polytechnic University, Blacksburg, VA, USA.
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45
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Tse G, Yeo JM, Chan YW, Lai ETHL, Yan BP. What Is the Arrhythmic Substrate in Viral Myocarditis? Insights from Clinical and Animal Studies. Front Physiol 2016; 7:308. [PMID: 27493633 PMCID: PMC4954848 DOI: 10.3389/fphys.2016.00308] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 07/06/2016] [Indexed: 01/25/2023] Open
Abstract
Sudden cardiac death (SCD) remains an unsolved problem in the twenty-first century. It is often due to rapid onset, ventricular arrhythmias caused by a number of different clinical conditions. A proportion of SCD patients have identifiable diseases such as cardiomyopathies, but for others, the causes are unknown. Viral myocarditis is becoming increasingly recognized as a contributor to unexplained mortality, and is thought to be a major cause of SCD in the first two decades of life. Myocardial inflammation, ion channel dysfunction, electrophysiological, and structural remodeling may play important roles in generating life-threatening arrhythmias. The aim of this review article is to examine the electrophysiology of action potential conduction and repolarization and the mechanisms by which their derangements lead to triggered and reentrant arrhythmogenesis. By synthesizing experimental evidence from pre-clinical and clinical studies, a framework of how host (inflammation), and viral (altered cellular signaling) factors can induce ion electrophysiological and structural remodeling is illustrated. Current pharmacological options are mainly supportive, which may be accompanied by mechanical circulatory support. Heart transplantation is the only curative option in the worst case scenario. Future strategies for the management of viral myocarditis are discussed.
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Affiliation(s)
- Gary Tse
- Li Ka Shing Faculty of Medicine, School of Biomedical Sciences, University of Hong KongHong Kong, China
- Department of Medicine and Therapeutics, The Chinese University of Hong KongHong Kong, China
| | - Jie M. Yeo
- Faculty of Medicine, Imperial College LondonLondon, UK
| | - Yin Wah Chan
- Department of Psychology, School of Biological Sciences, University of CambridgeCambridge, UK
| | - Eric T. H. Lai Lai
- Li Ka Shing Faculty of Medicine, School of Biomedical Sciences, University of Hong KongHong Kong, China
| | - Bryan P. Yan
- Department of Medicine and Therapeutics, The Chinese University of Hong KongHong Kong, China
- Department of Epidemiology and Preventive Medicine, Monash UniversityMelbourne, VIC, Australia
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46
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Johnston BM. Six Conductivity Values to Use in the Bidomain Model of Cardiac Tissue. IEEE Trans Biomed Eng 2016; 63:1525-31. [DOI: 10.1109/tbme.2015.2498144] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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47
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Veeraraghavan R, Gourdie RG. Stochastic optical reconstruction microscopy-based relative localization analysis (STORM-RLA) for quantitative nanoscale assessment of spatial protein organization. Mol Biol Cell 2016; 27:3583-3590. [PMID: 27307586 PMCID: PMC5221590 DOI: 10.1091/mbc.e16-02-0125] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 06/09/2016] [Indexed: 11/20/2022] Open
Abstract
Stochastic optical reconstruction microscopy–based relative localization analysis (STORM-RLA) is a novel method for the high-throughput quantification of spatial protein organization from three-dimensional single-molecule positional data. The spatial association between proteins is crucial to understanding how they function in biological systems. Colocalization analysis of fluorescence microscopy images is widely used to assess this. However, colocalization analysis performed on two-dimensional images with diffraction-limited resolution merely indicates that the proteins are within 200–300 nm of each other in the xy-plane and within 500–700 nm of each other along the z-axis. Here we demonstrate a novel three-dimensional quantitative analysis applicable to single-molecule positional data: stochastic optical reconstruction microscopy–based relative localization analysis (STORM-RLA). This method offers significant advantages: 1) STORM imaging affords 20-nm resolution in the xy-plane and <50 nm along the z-axis; 2) STORM-RLA provides a quantitative assessment of the frequency and degree of overlap between clusters of colabeled proteins; and 3) STORM-RLA also calculates the precise distances between both overlapping and nonoverlapping clusters in three dimensions. Thus STORM-RLA represents a significant advance in the high-throughput quantitative assessment of the spatial organization of proteins.
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Affiliation(s)
- Rengasayee Veeraraghavan
- Center for Heart and Regenerative Medicine Research, Virginia Tech Carilion Research Institute, Roanoke, VA 24016
| | - Robert G Gourdie
- Center for Heart and Regenerative Medicine Research, Virginia Tech Carilion Research Institute, Roanoke, VA 24016 .,School of Biomedical Engineering and Sciences, Virginia Polytechnic University, Blacksburg, VA 24016
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48
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Tse G, Lai ETH, Yeo JM, Yan BP. Electrophysiological Mechanisms of Bayés Syndrome: Insights from Clinical and Mouse Studies. Front Physiol 2016; 7:188. [PMID: 27303306 PMCID: PMC4886053 DOI: 10.3389/fphys.2016.00188] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 05/10/2016] [Indexed: 12/11/2022] Open
Abstract
Bayés syndrome is an under-recognized clinical condition characterized by inter-atrial block (IAB). This is defined electrocardiographically as P-wave duration > 120 ms and can be categorized into first, second and third degree IAB. It can be caused by inflammatory conditions such as systemic sclerosis and rheumatoid arthritis, abnormal protein deposition in cardiac amyloidosis, or neoplastic processes invading the inter-atrial conduction system, such as primary cardiac lymphoma. It may arise transiently during volume overload, autonomic dysfunction or electrolyte disturbances from vomiting. In other patients without an obvious cause, the predisposing factors are diabetes mellitus, hypertensive heart disease, and hypercholesterolemia. IAB has a strong association with atrial arrhythmogenesis, left atrial enlargement (LAE), and electro-mechanical discordance, increasing the risk of cerebrovascular accidents as well as myocardial and mesenteric ischemia. The aim of this review article is to synthesize experimental evidence on the pathogenesis of IAB and its underlying molecular mechanisms. Current medical therapies include anti-fibrotic, anti-arrhythmic and anti-coagulation agents, whereas interventional options include atrial resynchronization therapy by single or multisite pacing. Future studies will be needed to elucidate the significance of the link between IAB and atrial tachyarrhythmias in patients with different underlying etiologies and optimize the management options in these populations.
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Affiliation(s)
- Gary Tse
- Li Ka Shing Faculty of Medicine, School of Biomedical Sciences, University of Hong KongHong Kong, China
| | - Eric Tsz Him Lai
- Li Ka Shing Faculty of Medicine, School of Biomedical Sciences, University of Hong KongHong Kong, China
| | - Jie Ming Yeo
- School of Medicine, Imperial College LondonLondon, UK
| | - Bryan P. Yan
- Department of Medicine and Therapeutics, The Chinese University of Hong KongHong Kong, China
- Department of Epidemiology and Preventive Medicine, Monash UniversityMelbourne, VIC, Australia
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49
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Wei N, Mori Y, Tolkacheva EG. The dual effect of ephaptic coupling on cardiac conduction with heterogeneous expression of connexin 43. J Theor Biol 2016; 397:103-14. [PMID: 26968493 DOI: 10.1016/j.jtbi.2016.02.029] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 01/25/2016] [Accepted: 02/19/2016] [Indexed: 11/30/2022]
Abstract
Decreased and heterogeneous expression of connexin 43 (Cx43) are common features in animal heart failure models. Ephpatic coupling, which relies on the presence of junctional cleft space between the ends of adjacent cells, has been suggested to play a more active role in mediating intercellular electrical communication when gap junctions are reduced. To better understand the interplay of Cx43 expression and ephaptic coupling on cardiac conduction during heart failure, we performed numerical simulations on our model when Cx43 expression is reduced and heterogeneous. Under severely reduced Cx43 expression, we identified three new phenomena in the presence of ephaptic coupling: alternating conduction, in which ephaptic and gap junction-mediated mechanisms alternate; instability of planar fronts; and small amplitude action potential (SAP), which has a smaller potential amplitude than the normal action potential. In the presence of heterogeneous Cx43 expression, ephaptic coupling can either prevent or promote conduction block (CB) depending on the Cx43 knockout (Cx43KO) content. When Cx43KO content is relatively high, ephaptic coupling reduces the probabilities of CB. However, ephaptic coupling promotes CB when Cx43KO and wild type cells are mixed in roughly equal proportion, which can be attributed to an increase in current-to-load mismatch.
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Affiliation(s)
- Ning Wei
- School of Mathematics, University of Minnesota, 206 Church St. SE, Minneapolis, MN 55455, United States
| | - Yoichiro Mori
- School of Mathematics, University of Minnesota, 206 Church St. SE, Minneapolis, MN 55455, United States
| | - Elena G Tolkacheva
- Department of Biomedical Engineering, University of Minnesota, 312 Church St. SE, 6-128 Nils Hasselmo Hall, Minneapolis, MN 55455, United States.
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George SA, Bonakdar M, Zeitz M, Davalos RV, Smyth JW, Poelzing S. Extracellular sodium dependence of the conduction velocity-calcium relationship: evidence of ephaptic self-attenuation. Am J Physiol Heart Circ Physiol 2016; 310:H1129-39. [PMID: 26945081 DOI: 10.1152/ajpheart.00857.2015] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 03/02/2016] [Indexed: 11/22/2022]
Abstract
Our laboratory previously demonstrated that perfusate sodium and potassium concentrations can modulate cardiac conduction velocity (CV) consistent with theoretical predictions of ephaptic coupling (EpC). EpC depends on the ionic currents and intercellular separation in sodium channel rich intercalated disk microdomains like the perinexus. We suggested that perinexal width (WP) correlates with changes in extracellular calcium ([Ca(2+)]o). Here, we test the hypothesis that increasing [Ca(2+)]o reduces WP and increases CV. Mathematical models of EpC also predict that reducing WP can reduce sodium driving force and CV by self-attenuation. Therefore, we further hypothesized that reducing WP and extracellular sodium ([Na(+)]o) will reduce CV consistent with ephaptic self-attenuation. Transmission electron microscopy revealed that increasing [Ca(2+)]o (1 to 3.4 mM) significantly decreased WP Optically mapping wild-type (WT) (100% Cx43) mouse hearts demonstrated that increasing [Ca(2+)]o increases transverse CV during normonatremia (147.3 mM), but slows transverse CV during hyponatremia (120 mM). Additionally, CV in heterozygous (∼50% Cx43) hearts was more sensitive to changes in [Ca(2+)]o relative to WT during normonatremia. During hyponatremia, CV slowed in both WT and heterozygous hearts to the same extent. Importantly, neither [Ca(2+)]o nor [Na(+)]o altered Cx43 expression or phosphorylation determined by Western blotting, or gap junctional resistance determined by electrical impedance spectroscopy. Narrowing WP, by increasing [Ca(2+)]o, increases CV consistent with enhanced EpC between myocytes. Interestingly, during hyponatremia, reducing WP slowed CV, consistent with theoretical predictions of ephaptic self-attenuation. This study suggests that serum ion concentrations may be an important determinant of cardiac disease expression.
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Affiliation(s)
- Sharon A George
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - Mohammad Bonakdar
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; and
| | - Michael Zeitz
- Virginia Tech Carilion Research Institute and Center for Heart and Regenerative Medicine, Roanoke, Virginia
| | - Rafael V Davalos
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; and
| | - James W Smyth
- Virginia Tech Carilion Research Institute and Center for Heart and Regenerative Medicine, Roanoke, Virginia
| | - Steven Poelzing
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; Virginia Tech Carilion Research Institute and Center for Heart and Regenerative Medicine, Roanoke, Virginia
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