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Tsuji Y, Ogata T, Mochizuki K, Tamura S, Morishita Y, Takamatsu T, Matoba S, Tanaka H. Myofibroblasts impair myocardial impulse propagation by heterocellular connexin43 gap-junctional coupling through micropores. Front Physiol 2024; 15:1352911. [PMID: 38465264 PMCID: PMC10920281 DOI: 10.3389/fphys.2024.1352911] [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: 12/09/2023] [Accepted: 02/07/2024] [Indexed: 03/12/2024] Open
Abstract
Aim: Composite population of myofibroblasts (MFs) within myocardial tissue is known to alter impulse propagation, leading to arrhythmias. However, it remains unclear whether and how MFs alter their propagation patterns when contacting cardiomyocytes (CMs) without complex structural insertions in the myocardium. We attempted to unveil the effects of the one-sided, heterocellular CM-MF connection on the impulse propagation of CM monolayers without the spatial insertion of MFs as an electrical or mechanical obstacle. Methods and results: We evaluated fluo8-based spatiotemporal patterns in impulse propagation of neonatal rat CM monolayers cultured on the microporous membrane having 8-μm diameter pores with co-culture of MFs or CMs on the reverse membrane side (CM-MF model or CM-CM model, respectively). During consecutive pacing at 1 or 2 Hz, the CM monolayers exhibited forward impulse propagation from the pacing site with a slower conduction velocity (θ) and a larger coefficient of directional θ variation in the CM-MF model than that in the CM-CM model in a frequency-dependent manner (2 Hz >1 Hz). The localized placement of an MF cluster on the reverse side resulted in an abrupt segmental depression of the impulse propagation of the upper CM layer, causing a spatiotemporally non-uniform pattern. Dye transfer of the calcein loaded in the upper CM layer to the lower MF layer was attenuated by the gap-junction inhibitor heptanol. Immunocytochemistry identified definitive connexin 43 (Cx43) between the CMs and MFs in the membrane pores. MF-selective Cx43 knockdown in the MF layer improved both the velocity and uniformity of propagation in the CM monolayer. Conclusion: Heterocellular Cx43 gap junction coupling of CMs with MFs alters the spatiotemporal patterns of myocardial impulse propagation, even in the absence of spatially interjacent and mechanosensitive modulations by MFs. Moreover, MFs can promote pro-arrhythmogenic impulse propagation when in face-to-face contact with the myocardium that arises in the healing infarct border zone.
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Affiliation(s)
- Yumika Tsuji
- Department of Pathology and Cell Regulation and, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
- Department of Cardiovascular Medicine, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Takehiro Ogata
- Department of Pathology and Cell Regulation and, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Kentaro Mochizuki
- Department of Pathology and Cell Regulation and, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Shoko Tamura
- Department of Pathology and Cell Regulation and, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Yuma Morishita
- Department of Pathology and Cell Regulation and, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Tetsuro Takamatsu
- Department of Pathology and Cell Regulation and, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
- Department of Medical Photonics, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Satoaki Matoba
- Department of Cardiovascular Medicine, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Hideo Tanaka
- Department of Pathology and Cell Regulation and, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
- Faculty of Health and Medical Sciences, Kyoto University of Advanced Science, Kyoto, Japan
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2
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Iwamiya S, Ihara K, Furukawa T, Sasano T. Sacubitril/valsartan attenuates atrial conduction disturbance and electrophysiological heterogeneity with ameliorating fibrosis in mice. Front Cardiovasc Med 2024; 11:1341601. [PMID: 38312235 PMCID: PMC10834649 DOI: 10.3389/fcvm.2024.1341601] [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: 11/20/2023] [Accepted: 01/02/2024] [Indexed: 02/06/2024] Open
Abstract
Background Sacubitril/valsartan (SacVal) has been shown to improve the prognosis of heart failure; however, whether SacVal reduces the occurrence of atrial fibrillation (AF) in heart failure has not yet been elucidated. In this study, we aimed to determine whether SacVal is effective in reducing the occurrence of AF in heart failure and identify the underlying mechanism of its electrophysiological effect in mice. Methods Adult male mice underwent transverse aortic constriction, followed by SacVal, valsartan, or vehicle treatment for two weeks. Electrophysiological study (EPS) and optical mapping were performed to assess the susceptibility to AF and the atrial conduction properties, and fibrosis was investigated using heart tissue and isolated cardiac fibroblasts (CFs). Results EPS analysis revealed that AF was significantly less inducible in SacVal-treated mice than in vehicle-treated mice. Optical mapping of the atrium showed that SacVal-treated and valsartan-treated mice restored the prolonged action potential duration (APD); however, only SacVal-treated mice showed the restoration of decreased conduction velocity (CV) compared to vehicle-treated mice. In addition, the electrophysiological distribution analysis demonstrated that heterogeneous electrophysiological properties were rate-dependent and increased heterogeneity was closely related to the susceptibility to AF. SacVal attenuated the increased heterogeneity of CV at short pacing cycle length in atria, whereas Val could not. Histological and molecular evaluation showed that SacVal exerted the anti-fibrotic effect on the atria. An in vitro study of CFs treated with natriuretic peptides and LBQ657, the metabolite and active form of sacubitril, revealed that C-type natriuretic peptide (CNP) combined with LBQ657 had an additional anti-fibrotic effect on CFs. Conclusions Our results demonstrated that SacVal can improve the conduction disturbance and heterogeneity through the attenuation of fibrosis in murine atria and reduce the susceptibility of AF in heart failure with pressure overload, which might be attributed to the enhanced function of CNP.
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Affiliation(s)
- Satoshi Iwamiya
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University, Tokyo, Japan
| | - Kensuke Ihara
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University, Tokyo, Japan
| | - Tetsushi Furukawa
- Department of Bio-Informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Tetsuo Sasano
- Department of Cardiovascular Medicine, Tokyo Medical and Dental University, Tokyo, Japan
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3
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Jin Q, Lee KY, Selimi Z, Shimura D, Wang E, Zimmerman JF, Shaw RM, Kucera JP, Parker KK, Saffitz JE, Kleber AG. Determinants of electrical propagation and propagation block in Arrhythmogenic Cardiomyopathy. J Mol Cell Cardiol 2024; 186:71-80. [PMID: 37956903 PMCID: PMC10872523 DOI: 10.1016/j.yjmcc.2023.11.003] [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: 06/06/2023] [Revised: 10/27/2023] [Accepted: 11/06/2023] [Indexed: 11/21/2023]
Abstract
Gap junction and ion channel remodeling occur early in Arrhythmogenic Cardiomyopathy (ACM), but their pathogenic consequences have not been elucidated. Here, we identified the arrhythmogenic substrate, consisting of propagation slowing and conduction block, in ACM models expressing two different desmosomal gene variants. Neonatal rat ventricular myocytes were transduced to express variants in genes encoding desmosomal proteins plakoglobin or plakophilin-2. Studies were performed in engineered cells and anisotropic tissues to quantify changes in conduction velocity, formation of unidirectional propagation, cell-cell electrical coupling, and ion currents. Conduction velocity decreased by 71% and 63% in the two ACM models. SB216763, an inhibitor of glycogen synthase kinase-3 beta, restored conduction velocity to near normal levels. Compared to control, both ACM models showed greater propensity for unidirectional conduction block, which increased further at greater stimulation frequencies. Cell-cell electrical conductance measured in cell pairs was reduced by 86% and 87% in the two ACM models. Computer modeling showed close correspondence between simulated and experimentally determined changes in conduction velocity. The simulation identified that reduced cell-cell electrical coupling was the dominant factor leading to slow conduction, while the combination of reduced cell-cell electrical coupling, reduced sodium current and inward rectifier potassium current explained the development of unidirectional block. Expression of two different ACM variants markedly reduced cell-cell electrical coupling and conduction velocity, and greatly increased the likelihood of developing unidirectional block - both key features of arrhythmogenesis. This study provides the first quantitative analysis of cellular electrophysiological changes leading to the substrate of reentrant arrhythmias in early stage ACM.
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Affiliation(s)
- Qianru Jin
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA
| | - Keel Yong Lee
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA
| | - Zoja Selimi
- Department of Physiology, University of Bern, Bern, Switzerland
| | - Daisuke Shimura
- Nora Eccles Harrison Cardiovascular Research and Training Institute, Salt Lake City, UT, USA; Department of Surgery, School of Medicine, University of Utah, Salt Lake City, UT, USA
| | - Ethan Wang
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA
| | - John F Zimmerman
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA
| | - Robin M Shaw
- Nora Eccles Harrison Cardiovascular Research and Training Institute, Salt Lake City, UT, USA
| | - Jan P Kucera
- Department of Physiology, University of Bern, Bern, Switzerland
| | - Kevin Kit Parker
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA
| | - Jeffrey E Saffitz
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Andre G Kleber
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, USA; Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
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4
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Billur D, Olgar Y, Durak A, Yozgat AH, Unay S, Tuncay E, Turan B. An increase in intercellular crosstalk and electrotonic coupling between cardiomyocytes and nonmyocytes reshapes the electrical conduction in the metabolic heart characterized by short QT intervals in ECGs. Cell Biochem Funct 2023; 41:1526-1542. [PMID: 38014767 DOI: 10.1002/cbf.3893] [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: 10/04/2023] [Revised: 11/07/2023] [Accepted: 11/17/2023] [Indexed: 11/29/2023]
Abstract
Cardiac conduction abnormalities are disorders in metabolic syndrome (MetS), however, their mechanisms are unknown. Although ventricular arrhythmia reflects the changes in QT-interval of electrocardiograms associated with the changes in cardiomyocyte action potential durations (APDs), recent studies emphasize role of intercellular crosstalk between cardiomyocytes and nonmyocytes via passive (electrotonic)-conduction. Therefore, considering the possible increase in intercellular interactions of nonmyocytes with cardiomyocytes, we hypothesized an early-cardiac-remodeling characterized by short QT-interval via contributions and modulations of changes by nonmyocytes to the ventricular APs in an early-stage MetS hearts. Following the feeding of 8-week-old rats with a high-sucrose diet (32%; MetS rats) and validation of insulin resistance, there was a significant increase in heart rate and changes in the electrical characteristics of the hearts, especially a shortening in action potential (AP) duration of the papillary muscles. The patch-clamp analysis of ventricular cardiomyocytes showed an increase in the Na+ -channel currents while there were decreases in l-type Ca2+ -channel (LTCC) currents with unchanged K+ -channel currents. There was an increase in the phosphorylated form of connexin 43 (pCx43), mostly with lateral localization on sarcolemma, while its unphosphorylated form (Cx43) exhibited a high degree of localization within intercalated discs. A high-level positively-stained α-SMA and CD68 cells were prominently localized and distributed in interfibrillar spaces of the heart, implying the possible contributions of myofibroblasts and macrophages to both shortened APDs and abnormal electrical conduction in MetS hearts. Our data propose a previously unrecognized pathway for SQT induction in the heart. This pathway includes not only the contribution of short ventricular-APDs via ionic mechanisms but also increasing contributions of the electrotonic-cardiomyocyte depolarization, spontaneous electrical activity-associated fast heterogeneous impulse conduction in the heart via increased interactions and relocations between cardiomyocytes and nonmyocytes, which may be an explanation for the development of an SQT in early-cardiac-remodeling.
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Affiliation(s)
- Deniz Billur
- Departments of Histology-Embryology, Faculty of Medicine, Ankara University, Ankara, Türkiye
| | - Yusuf Olgar
- Departments of Biophysics, Faculty of Medicine, Ankara University, Ankara, Türkiye
| | - Aysegul Durak
- Departments of Biophysics, Faculty of Medicine, Ankara University, Ankara, Türkiye
| | - Ayse Hande Yozgat
- Departments of Histology-Embryology, Faculty of Medicine, Ankara University, Ankara, Türkiye
| | - Simge Unay
- Departments of Biophysics, Lokman Hekim University Faculty of Medicine, Ankara, Türkiye
| | - Erkan Tuncay
- Departments of Biophysics, Faculty of Medicine, Ankara University, Ankara, Türkiye
| | - Belma Turan
- Departments of Biophysics, Lokman Hekim University Faculty of Medicine, Ankara, Türkiye
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Remme CA. SCN5A channelopathy: arrhythmia, cardiomyopathy, epilepsy and beyond. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220164. [PMID: 37122208 PMCID: PMC10150216 DOI: 10.1098/rstb.2022.0164] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Accepted: 12/31/2022] [Indexed: 05/02/2023] Open
Abstract
Influx of sodium ions through voltage-gated sodium channels in cardiomyocytes is essential for proper electrical conduction within the heart. Both acquired conditions associated with sodium channel dysfunction (myocardial ischaemia, heart failure) as well as inherited disorders secondary to mutations in the gene SCN5A encoding for the cardiac sodium channel Nav1.5 are associated with life-threatening arrhythmias. Research in the last decade has uncovered the complex nature of Nav1.5 distribution, function, in particular within distinct subcellular subdomains of cardiomyocytes. Nav1.5-based channels furthermore display previously unrecognized non-electrogenic actions and may impact on cardiac structural integrity, leading to cardiomyopathy. Moreover, SCN5A and Nav1.5 are expressed in cell types other than cardiomyocytes as well as various extracardiac tissues, where their functional role in, e.g. epilepsy, gastrointestinal motility, cancer and the innate immune response is increasingly investigated and recognized. This review provides an overview of these novel insights and how they deepen our mechanistic knowledge on SCN5A channelopathies and Nav1.5 (dys)function. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
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Affiliation(s)
- Carol Ann Remme
- Department of Experimental Cardiology, Heart Centre, Amsterdam Cardiovascular Sciences, Heart Failure & Arrhythmias, Amsterdam UMC location AMC, University of Amsterdam, Amsterdam, The Netherlands
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6
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Mitrofanova L, Popov S. Editorial: Interplay between the heart and the immune system: Focus on heart rhythm regulation. Front Physiol 2022; 13:981499. [PMID: 36035479 PMCID: PMC9399915 DOI: 10.3389/fphys.2022.981499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 07/15/2022] [Indexed: 12/03/2022] Open
Affiliation(s)
- Lubov Mitrofanova
- Almazov National Medical Research Centre, Saint Petersburg, Russia
- *Correspondence: Lubov Mitrofanova,
| | - Sergey Popov
- Cardiology Research Institute, Tomsk National Research Medical Center, Russian Academy of Sciences, Tomsk, Russia
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Nayir S, Lacour SP, Kucera JP. Active force generation contributes to the complexity of spontaneous activity and to the response to stretch of murine cardiomyocyte cultures. J Physiol 2022; 600:3287-3312. [PMID: 35679256 PMCID: PMC9541716 DOI: 10.1113/jp283083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 06/01/2022] [Indexed: 11/17/2022] Open
Abstract
Abstract Cardiomyocyte cultures exhibit spontaneous electrical and contractile activity, as in a natural cardiac pacemaker. In such preparations, beat rate variability exhibits features similar to those of heart rate variability in vivo. Mechanical deformations and forces feed back on the electrical properties of cardiomyocytes, but it is not fully elucidated how this mechano‐electrical interplay affects beating variability in such preparations. Using stretchable microelectrode arrays, we assessed the effects of the myosin inhibitor blebbistatin and the non‐selective stretch‐activated channel blocker streptomycin on beating variability and on the response of neonatal or fetal murine ventricular cell cultures against deformation. Spontaneous electrical activity was recorded without stretch and upon predefined deformation protocols (5% uniaxial and 2% equibiaxial strain, applied repeatedly for 1 min every 3 min). Without stretch, spontaneous activity originated from the edge of the preparations, and its site of origin switched frequently in a complex manner across the cultures. Blebbistatin did not change mean beat rate, but it decreased the spatial complexity of spontaneous activity. In contrast, streptomycin did not exert any manifest effects. During the deformation protocols, beat rate increased transiently upon stretch but, paradoxically, also upon release. Blebbistatin attenuated the response to stretch, whereas this response was not affected by streptomycin. Therefore, our data support the notion that in a spontaneously firing network of cardiomyocytes, active force generation, rather than stretch‐activated channels, is involved mechanistically in the complexity of the spatiotemporal patterns of spontaneous activity and in the stretch‐induced acceleration of beating.
![]() Key points Monolayer cultures of cardiac cells exhibit spontaneous electrical and contractile activity, as in a natural cardiac pacemaker. Beating variability in these preparations recapitulates the power‐law behaviour of heart rate variability in vivo. However, the effects of mechano‐electrical feedback on beating variability are not yet fully understood. Using stretchable microelectrode arrays, we examined the effects of the contraction uncoupler blebbistatin and the non‐specific stretch‐activated channel blocker streptomycin on beating variability and on stretch‐induced changes of beat rate. Without stretch, blebbistatin decreased the spatial complexity of beating variability, whereas streptomycin had no effects. Both stretch and release increased beat rate transiently; blebbistatin attenuated the increase of beat rate upon stretch, whereas streptomycin had no effects. Active force generation contributes to the complexity of spatiotemporal patterns of beating variability and to the increase of beat rate upon mechanical deformation. Our study contributes to the understanding of how mechano‐electrical feedback influences heart rate variability.
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Affiliation(s)
- Seyma Nayir
- Department of Physiology, University of Bern, Bern, Switzerland
| | | | - Jan P Kucera
- Department of Physiology, University of Bern, Bern, Switzerland
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8
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Saliani A, Biswas S, Jacquemet V. Simulation of atrial fibrillation in a non-ohmic propagation model with dynamic gap junctions. CHAOS (WOODBURY, N.Y.) 2022; 32:043113. [PMID: 35489863 DOI: 10.1063/5.0082763] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 03/24/2022] [Indexed: 06/14/2023]
Abstract
Gap junctions exhibit nonlinear electrical properties that have been hypothesized to be relevant to arrhythmogenicity in a structurally remodeled tissue. Large-scale implementation of gap junction dynamics in 3D propagation models remains challenging. We aim to quantify the impact of nonlinear diffusion during episodes of arrhythmias simulated in a left atrial model. Homogenization of conduction properties in the presence of nonlinear gap junctions was performed by generalizing a previously developed mathematical framework. A monodomain model was solved in which conductivities were time-varying and depended on transjunctional potentials. Gap junction conductances were derived from a simplified Vogel-Weingart model with first-order gating and adjustable time constant. A bilayer interconnected cable model of the left atrium with 100 μm resolution was used. The diffusion matrix was recomputed at each time step according to the state of the gap junctions. Sinus rhythm and atrial fibrillation episodes were simulated in remodeled tissue substrates. Slow conduction was induced by reduced coupling and by diffuse or stringy fibrosis. Simulations starting from the same initial conditions were repeated with linear and nonlinear gap junctions. The discrepancy in activation times between the linear and nonlinear diffusion models was quantified. The results largely validated the linear approximation for conduction velocities >20 cm/s. In very slow conduction substrates, the discrepancy accumulated over time during atrial fibrillation, eventually leading to qualitative differences in propagation patterns, while keeping the descriptive statistics, such as cycle lengths, unchanged. The discrepancy growth rate was increased by impaired conduction, fibrosis, conduction heterogeneity, lateral uncoupling, fast gap junction time constant, and steeper action potential duration restitution.
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Affiliation(s)
- Ariane Saliani
- Institute of Biomedical Engineering, Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, C.P. 6128, succ. Centre-ville, Montreal, Quebec H3C 3J7, Canada
| | - Subhamoy Biswas
- Institute of Biomedical Engineering, Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, C.P. 6128, succ. Centre-ville, Montreal, Quebec H3C 3J7, Canada
| | - Vincent Jacquemet
- Institute of Biomedical Engineering, Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, C.P. 6128, succ. Centre-ville, Montreal, Quebec H3C 3J7, Canada
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Palacio LC, Ugarte JP, Saiz J, Tobón C. The Effects of Fibrotic Cell Type and Its Density on Atrial Fibrillation Dynamics: An In Silico Study. Cells 2021; 10:cells10102769. [PMID: 34685750 PMCID: PMC8534881 DOI: 10.3390/cells10102769] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/03/2021] [Accepted: 10/12/2021] [Indexed: 12/12/2022] Open
Abstract
Remodeling in atrial fibrillation (AF) underlines the electrical and structural changes in the atria, where fibrosis is a hallmark of arrhythmogenic structural alterations. Fibrosis is an important feature of the AF substrate and can lead to abnormal conduction and, consequently, mechanical dysfunction. The fibrotic process comprises the presence of fibrotic cells, including fibroblasts, myofibroblasts and fibrocytes, which play an important role during fibrillatory dynamics. This work assesses the effect of the diffuse fibrosis density and the intermingled presence of the three types of fibrotic cells on the dynamics of persistent AF. For this purpose, the three fibrotic cells were electrically coupled to cardiomyocytes in a 3D realistic model of human atria. Low (6.25%) and high (25%) fibrosis densities were implemented in the left atrium according to a diffuse fibrosis representation. We analyze the action potential duration, conduction velocity and fibrillatory conduction patterns. Additionally, frequency analysis was performed in 50 virtual electrograms. The tested fibrosis configurations generated a significant conduction velocity reduction, where the larger effect was observed at high fibrosis density (up to 82% reduction in the fibrocytes configuration). Increasing the fibrosis density intensifies the vulnerability to multiple re-entries, zigzag propagation, and chaotic activity in the fibrillatory conduction. The most complex propagation patterns were observed at high fibrosis densities and the fibrocytes are the cells with the largest proarrhythmic effect. Left-to-right dominant frequency gradients can be observed for all fibrosis configurations, where the fibrocytes configuration at high density generates the most significant gradients (up to 4.5 Hz). These results suggest the important role of different fibrotic cell types and their density in diffuse fibrosis on the chaotic propagation patterns during persistent AF.
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Affiliation(s)
- Laura C. Palacio
- Materiales Nanoestructurados y Biomodelación (MATBIOM), Universidad de Medellín, Medellín 050032, Colombia;
| | - Juan P. Ugarte
- Grupo de Investigación en Modelamiento y Simulación Computacional (GIMSC), Universidad de San Buenaventura, Medellín 050010, Colombia;
| | - Javier Saiz
- Centro de Investigación e Innovación en Bioingeniería (CIB), Universitat Politècnica de València, 46022 Valencia, Spain;
| | - Catalina Tobón
- Materiales Nanoestructurados y Biomodelación (MATBIOM), Universidad de Medellín, Medellín 050032, Colombia;
- Correspondence:
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Irakoze É, Jacquemet V. Multiparameter optimization of nonuniform passive diffusion properties for creating coarse-grained equivalent models of cardiac propagation. Comput Biol Med 2021; 138:104863. [PMID: 34562679 DOI: 10.1016/j.compbiomed.2021.104863] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 09/06/2021] [Accepted: 09/07/2021] [Indexed: 11/30/2022]
Abstract
The arrhythmogenic role of discrete cardiac propagation may be assessed by comparing discrete (fine-grained) and equivalent continuous (coarse-grained) models. We aim to develop an optimization algorithm for estimating the smooth conductivity field that best reproduces the diffusion properties of a given discrete model. Our algorithm iteratively adjusts local conductivity of the coarse-grained continuous model by simulating passive diffusion from white noise initial conditions during 3-10 ms and computing the root mean square error with respect to the discrete model. The coarse-grained conductivity field was interpolated from up to 300 evenly spaced control points. We derived an approximate formula for the gradient of the cost function that required (in two dimensions) only two additional simulations per iteration regardless of the number of estimated parameters. Conjugate gradient solver facilitated simultaneous optimization of multiple conductivity parameters. The method was tested in rectangular anisotropic tissues with uniform and nonuniform conductivity (slow regions with sinusoidal profile) and random diffuse fibrosis, as well as in a monolayer interconnected cable model of the left atrium with spatially-varying fibrosis density. Comparison of activation maps served as validation. The results showed that after convergence the errors in activation time were < 1 ms for rectangular geometries and 1-3 ms in the atrial model. Our approach based on the comparison of passive properties (<10 ms simulation) avoids performing active propagation simulations (>100 ms) at each iteration while reproducing activation maps, with possible applications to investigating the impact of microstructure on arrhythmias.
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Affiliation(s)
- Éric Irakoze
- Pharmacology and Physiology Department, Institute of Biomedical Engineering, Université de Montréal, Montreal, QC, H3T 1J4, Canada; Hôpital Du Sacré-Cœur de Montréal, Research Center, 5400 Boul. Gouin Ouest, Montreal, QC, H4J 1C5, Canada
| | - Vincent Jacquemet
- Pharmacology and Physiology Department, Institute of Biomedical Engineering, Université de Montréal, Montreal, QC, H3T 1J4, Canada; Hôpital Du Sacré-Cœur de Montréal, Research Center, 5400 Boul. Gouin Ouest, Montreal, QC, H4J 1C5, Canada.
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11
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Abstract
Conduction disorders and arrhythmias remain difficult to treat and are increasingly prevalent owing to the increasing age and body mass of the general population, because both are risk factors for arrhythmia. Many of the underlying conditions that give rise to arrhythmia - including atrial fibrillation and ventricular arrhythmia, which frequently occur in patients with acute myocardial ischaemia or heart failure - can have an inflammatory component. In the past, inflammation was viewed mostly as an epiphenomenon associated with arrhythmia; however, the recently discovered inflammatory and non-canonical functions of cardiac immune cells indicate that leukocytes can be arrhythmogenic either by altering tissue composition or by interacting with cardiomyocytes; for example, by changing their phenotype or perhaps even by directly interfering with conduction. In this Review, we discuss the electrophysiological properties of leukocytes and how these cells relate to conduction in the heart. Given the thematic parallels, we also summarize the interactions between immune cells and neural systems that influence information transfer, extrapolating findings from the field of neuroscience to the heart and defining common themes. We aim to bridge the knowledge gap between electrophysiology and immunology, to promote conceptual connections between these two fields and to explore promising opportunities for future research.
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12
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Kostecki GM, Shi Y, Chen CS, Reich DH, Entcheva E, Tung L. Optogenetic current in myofibroblasts acutely alters electrophysiology and conduction of co-cultured cardiomyocytes. Sci Rep 2021; 11:4430. [PMID: 33627695 PMCID: PMC7904933 DOI: 10.1038/s41598-021-83398-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Accepted: 01/27/2021] [Indexed: 01/31/2023] Open
Abstract
Interactions between cardiac myofibroblasts and myocytes may slow conduction and generate spontaneous beating in fibrosis, increasing the chance of life-threatening arrhythmia. While co-culture studies have shown that myofibroblasts can affect cardiomyocyte electrophysiology in vitro, the extent of myofibroblast-myocyte electrical conductance in a syncytium is unknown. In this neonatal rat study, cardiac myofibroblasts were transduced with Channelrhodopsin-2, which allowed acute and selective increase of myofibroblast current, and plated on top of cardiomyocytes. Optical mapping revealed significantly decreased conduction velocity (- 27 ± 6%, p < 10-3), upstroke rate (- 13 ± 4%, p = 0.002), and action potential duration (- 14 ± 7%, p = 0.004) in co-cultures when 0.017 mW/mm2 light was applied, as well as focal spontaneous beating in 6/7 samples and a decreased cycle length (- 36 ± 18%, p = 0.002) at 0.057 mW/mm2 light. In silico modeling of the experiments reproduced the experimental findings and suggested the light levels used in experiments produced excess current similar in magnitude to endogenous myofibroblast current. Fitting the model to experimental data predicted a tissue-level electrical conductance across the 3-D interface between myofibroblasts and cardiomyocytes of ~ 5 nS/cardiomyocyte, and showed how increased myofibroblast-myocyte conductance, increased myofibroblast/myocyte capacitance ratio, and increased myofibroblast current, which occur in fibrosis, can work in tandem to produce pro-arrhythmic increases in conduction and spontaneous beating.
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Affiliation(s)
- Geran M Kostecki
- Department of Biomedical Engineering, Johns Hopkins University, 720 Rutland Ave., Baltimore, MD, 21205, USA
| | - Yu Shi
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Christopher S Chen
- Biological Design Center, Department of Biomedical Engineering, Boston University, Boston, MA, USA
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
| | - Daniel H Reich
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Emilia Entcheva
- Department of Biomedical Engineering, George Washington University, Washington, DC, USA
| | - Leslie Tung
- Department of Biomedical Engineering, Johns Hopkins University, 720 Rutland Ave., Baltimore, MD, 21205, USA.
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13
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Hume RD, Chong JJH. The Cardiac Injury Immune Response as a Target for Regenerative and Cellular Therapies. Clin Ther 2020; 42:1923-1943. [PMID: 33010930 DOI: 10.1016/j.clinthera.2020.09.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 08/20/2020] [Accepted: 09/09/2020] [Indexed: 12/11/2022]
Abstract
PURPOSE Despite modern reperfusion and pharmacologic therapies, myocardial infarction (MI) remains a leading cause of morbidity and mortality worldwide. Therefore, the development of further therapeutics affecting post-MI recovery poses significant benefits. This review focuses on the post-MI immune response and immunomodulatory therapeutics that could improve the wound-healing response. METHODS This narrative review used OVID versions of MEDLINE and EMBASE searching for clinical therapeutics targeting the immune system during MI. Preclinical models and clinical trials were included. Additional studies were sourced from the reference lists of relevant articles and other personal files. FINDINGS After MI, cardiomyocytes are starved of oxygen and undergo cell death via coagulative necrosis. This process activates the immune system and a multifaceted wound-healing response, comprising a number of complex and overlapping phases. Overactivation or persistence of one or more of these phases can have potentially lethal implications. This review describes the immune response post-MI and any adverse events that can occur during these different phases. Second, we describe immunomodulatory therapies that attempt to target these immune cell aberrations by mitigating or diminishing their effects on the wound-healing response. Also discussed are adult stem/progenitor cell therapies, exosomes, and regulatory T cells, and their immunomodulatory effects in the post-MI setting. IMPLICATIONS An updated understanding into the importance of various inflammatory cell phenotypes, coupled with new technologies, may hold promise for a new era of immunomodulatory therapeutics. The implications of such therapies could dramatically improve patients' quality of life post-MI and reduce the incidence of progressive heart failure.
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Affiliation(s)
- Robert D Hume
- Centre for Heart Research, Westmead Institute for Medical Research, The University of Sydney, 176 Hawkesbury Rd, Westmead, NSW 2145, Australia
| | - James J H Chong
- Centre for Heart Research, Westmead Institute for Medical Research, The University of Sydney, 176 Hawkesbury Rd, Westmead, NSW 2145, Australia; Department of Cardiology, Westmead Hospital, Hawkesbury Rd, Westmead, NSW 2145, Australia.
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14
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Ushakov A, Ivanchenko V, Gagarina A. Regulation of Myocardial Extracellular Matrix Dynamic Changes in Myocardial Infarction and Postinfarct Remodeling. Curr Cardiol Rev 2020; 16:11-24. [PMID: 31072294 PMCID: PMC7393593 DOI: 10.2174/1573403x15666190509090832] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 04/22/2019] [Accepted: 04/29/2019] [Indexed: 02/07/2023] Open
Abstract
The article represents literature review dedicated to molecular and cellular mechanisms underlying clinical manifestations and outcomes of acute myocardial infarction. Extracellular matrix adaptive changes are described in detail as one of the most important factors contributing to healing of damaged myocardium and post-infarction cardiac remodeling. Extracellular matrix is reviewed as dynamic constantly remodeling structure that plays a pivotal role in myocardial repair. The role of matrix metalloproteinases and their tissue inhibitors in fragmentation and degradation of extracellular matrix as well as in myocardium healing is discussed. This review provides current information about fibroblasts activity, the role of growth factors, particularly transforming growth factor β and cardiotrophin-1, colony-stimulating factors, adipokines and gastrointestinal hormones, various matricellular proteins. In conclusion considering the fact that dynamic transformation of extracellular matrix after myocardial ischemic damage plays a pivotal role in myocardial infarction outcomes and prognosis, we suggest a high importance of further investigation of mechanisms underlying extracellular matrix remodeling and cell-matrix interactions in cardiovascular diseases.
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Affiliation(s)
- Alexey Ushakov
- Department of Internal Medicine #1 with Clinical Pharmacology Course, Medical Academy named after S.I. Georgievsky of V.I. Vernadsky Crimean Federal University, Simferopol, Russian Federation
| | - Vera Ivanchenko
- Department of Internal Medicine #1 with Clinical Pharmacology Course, Medical Academy named after S.I. Georgievsky of V.I. Vernadsky Crimean Federal University, Simferopol, Russian Federation
| | - Alina Gagarina
- Department of Internal Medicine #1 with Clinical Pharmacology Course, Medical Academy named after S.I. Georgievsky of V.I. Vernadsky Crimean Federal University, Simferopol, Russian Federation
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15
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De Simone SA, Moyle S, Buccarello A, Dellenbach C, Kucera JP, Rohr S. The Role of Membrane Capacitance in Cardiac Impulse Conduction: An Optogenetic Study With Non-excitable Cells Coupled to Cardiomyocytes. Front Physiol 2020; 11:194. [PMID: 32273847 PMCID: PMC7113375 DOI: 10.3389/fphys.2020.00194] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 02/20/2020] [Indexed: 12/15/2022] Open
Abstract
Non-excitable cells (NECs) such as cardiac myofibroblasts that are electrotonically coupled to cardiomyocytes affect conduction velocity (θ) by representing a capacitive load (CL: increased membrane to be charged) and a resistive load (RL: partial depolarization of coupled cardiomyocytes). In this study, we untangled the relative contributions of both loading modalities to NEC-dependent arrhythmogenic conduction slowing. Discrimination between CL and RL was achieved by reversibly removing the RL component by light activation of the halorhodopsin-based hyperpolarizing membrane voltage actuator eNpHR3.0-eYFP (enhanced yellow fluorescent protein) expressed in communication-competent fibroblast-like NIH3T3 cells (3T3HR cells) that served as a model of coupled NECs. Experiments were conducted with strands of neonatal rat ventricular cardiomyocytes coated at increasing densities with 3T3HR cells. Impulse conduction along preparations stimulated at 2.5 Hz was assessed with multielectrode arrays. The relative density of 3T3HR cells was determined by dividing the area showing eYFP fluorescence by the area covered with cardiomyocytes [coverage factor (CF)]. Compared to cardiomyocytes, 3T3HR cells exhibited a depolarized membrane potential (−34 mV) that was shifted to −104 mV during activation of halorhodopsin. Without illumination, 3T3HR cells slowed θ along the preparations from ∼330 mm/s (control cardiomyocyte strands) to ∼100 mm/s (CF = ∼0.6). Illumination of the preparation increased the electrogram amplitudes and induced partial recovery of θ at CF > 0.3. Computer simulations demonstrated that the θ deficit observed during illumination was attributable in full to the CL represented by coupled 3T3HR cells with θ showing a power-law relationship to capacitance with an exponent of −0.78 (simulations) and −0.99 (experiments). The relative contribution of CL and RL to conduction slowing changed as a function of CF with CL dominating at CF ≤ ∼0.3, both mechanisms being equally important at CF = ∼0.5, and RL dominating over CL at CF > 0.5. The finding that RL did not affect θ at CFs ≤ 0.3 is explained by the circumstance that, at the respective moderate levels of cardiomyocyte depolarization, supernormal conduction stabilized propagation. The findings provide experimental estimates for the dependence of θ on membrane capacitance in general and suggest that the myocardium can absorb moderate numbers of electrotonically coupled NECs without showing substantial alterations of θ.
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Affiliation(s)
- Stefano Andrea De Simone
- Laboratory of Cellular Optics II, Department of Physiology, University of Bern, Bern, Switzerland
| | - Sarah Moyle
- Laboratory of Cellular Optics II, Department of Physiology, University of Bern, Bern, Switzerland
| | - Andrea Buccarello
- Integrative Cardiac Bioelectricity Group, Department of Physiology, University of Bern, Bern, Switzerland
| | - Christian Dellenbach
- Laboratory of Cellular Optics II, Department of Physiology, University of Bern, Bern, Switzerland
| | - Jan Pavel Kucera
- Integrative Cardiac Bioelectricity Group, Department of Physiology, University of Bern, Bern, Switzerland
| | - Stephan Rohr
- Laboratory of Cellular Optics II, Department of Physiology, University of Bern, Bern, Switzerland
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16
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Cunningham KS, Spears DA, Care M. Evaluation of cardiac hypertrophy in the setting of sudden cardiac death. Forensic Sci Res 2019; 4:223-240. [PMID: 31489388 PMCID: PMC6713129 DOI: 10.1080/20961790.2019.1633761] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 06/17/2019] [Accepted: 06/17/2019] [Indexed: 01/06/2023] Open
Abstract
Ventricular hypertrophy is a common pathological finding at autopsy that can act as a substrate for arrhythmogenesis. Pathologists grapple with the significance of ventricular hypertrophy when assessing the sudden and unexpected deaths of young people and what it could mean for surviving family members. The pathological spectrum of left ventricular hypertrophy (LVH) is reviewed herein. This article is oriented to the practicing autopsy pathologist to help make sense of various patterns of increased heart muscle, particularly those that are not clearly cardiomyopathic, yet present in the setting of sudden cardiac death. The article also reviews factors influencing arrhythmogenesis as well as genetic mutations most commonly associated with ventricular hypertrophy, especially those associated with hypertrophic cardiomyopathy (HCM).
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Affiliation(s)
- Kristopher S Cunningham
- Department of Laboratory Medicine and Pathobiology, Ontario Forensic Pathology Service, University of Toronto, Toronto, Canada
| | - Danna A Spears
- University Health Network, Division of Cardiology - Electrophysiology, University of Toronto, Toronto, Canada
| | - Melanie Care
- Fred A. Litwin Family Centre in Genetic Medicine and Inherited Arrhythmia Clinic, University Health Network & Mount Sinai Hospital, University of Toronto, Toronto, Canada
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17
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Wang E, Rafatian N, Zhao Y, Lee A, Lai BFL, Lu RX, Jekic D, Davenport Huyer L, Knee-Walden EJ, Bhattacharya S, Backx PH, Radisic M. Biowire Model of Interstitial and Focal Cardiac Fibrosis. ACS CENTRAL SCIENCE 2019; 5:1146-1158. [PMID: 31403068 PMCID: PMC6661857 DOI: 10.1021/acscentsci.9b00052] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Indexed: 05/07/2023]
Abstract
Myocardial fibrosis is a severe global health problem due to its prevalence in all forms of cardiac diseases and direct role in causing heart failure. The discovery of efficient antifibrotic compounds has been hampered due to the lack of a physiologically relevant disease model. Herein, we present a disease model of human myocardial fibrosis and use it to establish a compound screening system. In the Biowire II platform, cardiac tissues are suspended between a pair of poly(octamethylene maleate (anhydride) citrate) (POMaC) wires. Noninvasive functional readouts are realized on the basis of the deflection of the intrinsically fluorescent polymer. The disease model is constructed to recapitulate contractile, biomechanical, and electrophysiological complexities of fibrotic myocardium. Additionally, we constructed a heteropolar integrated model with fibrotic and healthy cardiac tissues coupled together. The integrated model captures the regional heterogeneity of scar lesion, border zone, and adjacent healthy myocardium. Finally, we demonstrate the utility of the system for the evaluation of antifibrotic compounds. The high-fidelity in vitro model system combined with convenient functional readouts could potentially facilitate the development of precision medicine strategies for cardiac fibrosis modeling and establish a pipeline for preclinical compound screening.
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Affiliation(s)
- Erika
Yan Wang
- Institute
of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3G9, Canada
| | - Naimeh Rafatian
- Department
of Physiology, Faculty of Medicine, University
of Toronto, Toronto, Ontario M5S 1A8, Canada
- Toronto
General Research Institute, Toronto, Ontario M5G 2C4, Canada
| | - Yimu Zhao
- Department
of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario M5S 3E5, Canada
| | - Angela Lee
- RDM
Division of Cardiovascular Medicine and Wellcome Trust Centre for
Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
| | - Benjamin Fook Lun Lai
- Institute
of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3G9, Canada
| | - Rick Xingze Lu
- Institute
of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3G9, Canada
| | - Danica Jekic
- McGill University, Montreal, Quebec H3A 2K6, Canada
| | - Locke Davenport Huyer
- Institute
of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3G9, Canada
- Department
of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario M5S 3E5, Canada
| | - Ericka J. Knee-Walden
- Institute
of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3G9, Canada
| | - Shoumo Bhattacharya
- RDM
Division of Cardiovascular Medicine and Wellcome Trust Centre for
Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
| | - Peter H. Backx
- Department
of Physiology, Faculty of Medicine, University
of Toronto, Toronto, Ontario M5S 1A8, Canada
- Toronto
General Research Institute, Toronto, Ontario M5G 2C4, Canada
- Department
of Biology, York University, Toronto, Ontario M3J 1P3, Canada
| | - Milica Radisic
- Institute
of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3G9, Canada
- Toronto
General Research Institute, Toronto, Ontario M5G 2C4, Canada
- Department
of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario M5S 3E5, Canada
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18
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Sánchez J, Gomez JF, Martinez-Mateu L, Romero L, Saiz J, Trenor B. Heterogeneous Effects of Fibroblast-Myocyte Coupling in Different Regions of the Human Atria Under Conditions of Atrial Fibrillation. Front Physiol 2019; 10:847. [PMID: 31333496 PMCID: PMC6620707 DOI: 10.3389/fphys.2019.00847] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2018] [Accepted: 06/19/2019] [Indexed: 12/19/2022] Open
Abstract
Background: Atrial fibrillation (AF), the most common cardiac arrhythmia, is characterized by alteration of the action potential (AP) propagation. Under persistent AF, myocytes undergo electrophysiological and structural remodeling, which involves fibroblast proliferation and differentiation, modifying the substrate for AP propagation. The aim of this study was to analyze the effects on the AP of fibroblast-myocyte coupling during AF and its propagation in different regions of the atria. Methods: Isolated myocytes were coupled to different numbers of fibroblasts using the established AP models and tissue simulations were performed by randomly distributing fibroblasts. Fibroblast formulations were updated to match recent experimental data. Major ion current conductances of the myocyte model were modified to simulate AP heterogeneity in four different atrial regions (right atrium posterior wall, crista terminalis, left atrium posterior wall, and pulmonary vein) according to experimental and computational studies. Results: The results of the coupled myocyte-fibroblast simulations suggest that a more depolarized membrane potential and higher fibroblast membrane capacitance have a greater impact on AP duration and myocyte maximum depolarization velocity. The number of coupled fibroblasts and the stimulation frequency are determining factors in altering myocyte AP. Strand simulations show that conduction velocity tends to homogenize in all regions, while the left atrium is more likely to be affected by fibroblast and AP propagation block is more likely to occur. The pulmonary vein is the most affected region, even at low fibroblast densities. In 2D sheets with randomly placed fibroblasts, wavebreaks are observed in the low density (10%) central fibrotic zone and when fibroblast density increases (40%) propagation in the fibrotic region is practically blocked. At densities of 10 and 20% the width of the vulnerable window increases with respect to control but is decreased at 40%. Conclusion: Myocyte-fibroblast coupling characteristics heterogeneously affect AP propagation and features in the different atrial zones, and myocytes from the left atria are more sensitive to fibroblast coupling.
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Affiliation(s)
- Jorge Sánchez
- Centre for Research and Innovation in Bioengineering, Universitat Politècnica de València, Valencia, Spain
| | - Juan F Gomez
- Centre for Research and Innovation in Bioengineering, Universitat Politècnica de València, Valencia, Spain
| | - Laura Martinez-Mateu
- Centre for Research and Innovation in Bioengineering, Universitat Politècnica de València, Valencia, Spain
| | - Lucia Romero
- Centre for Research and Innovation in Bioengineering, Universitat Politècnica de València, Valencia, Spain
| | - Javier Saiz
- Centre for Research and Innovation in Bioengineering, Universitat Politècnica de València, Valencia, Spain
| | - Beatriz Trenor
- Centre for Research and Innovation in Bioengineering, Universitat Politècnica de València, Valencia, Spain
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19
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Lee TM, Harn HJ, Chiou TW, Chuang MH, Chen CH, Chuang CH, Lin PC, Lin SZ. Preconditioned adipose-derived stem cells ameliorate cardiac fibrosis by regulating macrophage polarization in infarcted rat hearts through the PI3K/STAT3 pathway. J Transl Med 2019; 99:634-647. [PMID: 30683900 DOI: 10.1038/s41374-018-0181-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 11/10/2018] [Accepted: 11/17/2018] [Indexed: 11/09/2022] Open
Abstract
Stem cells can modify macrophage phenotypes; however, the mechanisms remain unclear. We investigated whether n-butylidenephthalide (BP) primed adipose-derived stem cells (ADSCs) attenuated cardiac fibrosis via regulating macrophage phenotype by a PI3K/STAT3-dependent pathway in postinfarcted rats. Male Wistar rats after coronary ligation were allocated to receive either intramyocardial injection of vehicle, ADSCs (1 × 106 cells), BP-preconditioned ADSCs, (BP + lithium)-preconditioned ADSCs, (BP + LY294002)-preconditioned ADSCs, and (BP + S3I-201)-preconditioned ADSCs. ADSCs were primed for 16 h before implantation. BP-pretreated ADSCs increased the cell viability compared with naive ADSCs in the in vitro experiments. Infarct sizes were similar among the infarcted groups at the acute and chronic stages of infarction. At day 3 after infarction, post-infarction was associated with increased M1 macrophage infiltration, which was inhibited by administering naive ADSCs. Compared with naive ADSCs, BP-preconditioned ADSCs provided a significant increase of Akt and STAT3 phosphorylation, STAT3 activity, STAT3 nuclear translocation, myocardial IL-10 levels, and the percentage of M2 macrophage infiltration. The effects of BP on M2 polarization were reversed by LY294002 or S3I-201. Furthermore, the phosphorylation of both Akt and STAT3 was abolished by LY294002, whereas Akt phosphorylation was not affected following the inhibition of STAT3. The addition of lithium did not have additional effects compared with BP alone. After 4 weeks of implantation, ADSCs remained in the myocardium, and reduced fibrosis and improved cardiac function. BP-preconditioned ADSCs provided superior cardioprotection, greater ADSC engraftment, and antifibrotic effects compared with naive ADSCs. These results suggest that BP-pretreated ADSCs polarize macrophages into M2 cells more efficiently than naive ADSCs via the PI3K/STAT3 pathway.
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Affiliation(s)
- Tsung-Ming Lee
- Cardiovascular Institute, An Nan Hospital, China Medical University, Tainan, Taiwan.,Department of Medicine, China Medical University, Taichung, Taiwan
| | - Horng-Jyh Harn
- Bioinnovation Center, Tzu Chi Foundation, Hualien, Taiwan.,Department of Pathology, Buddhist Tzu Chi General Hospital, Tzu Chi University, Hualien, Taiwan
| | - Tzyy-Wen Chiou
- Department of Life Science and Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan
| | - Ming-Hsi Chuang
- Department of Technology Management, Chung Hua University, Hsinchu, Taiwan.,Gwo Xi Stem Cell Applied Technology, Hsinchu, Taiwan
| | | | | | - Po-Cheng Lin
- Gwo Xi Stem Cell Applied Technology, Hsinchu, Taiwan
| | - Shinn-Zong Lin
- Bioinnovation Center, Tzu Chi Foundation, Hualien, Taiwan. .,Department of Neurosurgery, Buddhist Tzu Chi General Hospital, Tzu Chi University, Hualien, Taiwan.
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20
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Kim TY, Kofron CM, King ME, Markes AR, Okundaye AO, Qu Z, Mende U, Choi BR. Directed fusion of cardiac spheroids into larger heterocellular microtissues enables investigation of cardiac action potential propagation via cardiac fibroblasts. PLoS One 2018; 13:e0196714. [PMID: 29715271 PMCID: PMC5929561 DOI: 10.1371/journal.pone.0196714] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 04/18/2018] [Indexed: 12/13/2022] Open
Abstract
Multicellular spheroids generated through cellular self-assembly provide cytoarchitectural complexities of native tissue including three-dimensionality, extensive cell-cell contacts, and appropriate cell-extracellular matrix interactions. They are increasingly suggested as building blocks for larger engineered tissues to achieve shapes, organization, heterogeneity, and other biomimetic complexities. Application of these tissue culture platforms is of particular importance in cardiac research as the myocardium is comprised of distinct but intermingled cell types. Here, we generated scaffold-free 3D cardiac microtissue spheroids comprised of cardiac myocytes (CMs) and/or cardiac fibroblasts (CFs) and used them as building blocks to form larger microtissues with different spatial distributions of CMs and CFs. Characterization of fusing homotypic and heterotypic spheroid pairs revealed an important influence of CFs on fusion kinetics, but most strikingly showed rapid fusion kinetics between heterotypic pairs consisting of one CF and one CM spheroid, indicating that CMs and CFs self-sort in vitro into the intermixed morphology found in the healthy myocardium. We then examined electrophysiological integration of fused homotypic and heterotypic microtissues by mapping action potential propagation. Heterocellular elongated microtissues which recapitulate the disproportionate CF spatial distribution seen in the infarcted myocardium showed that action potentials propagate through CF volumes albeit with significant delay. Complementary computational modeling revealed an important role of CF sodium currents and the spatial distribution of the CM-CF boundary in action potential conduction through CF volumes. Taken together, this study provides useful insights for the development of complex, heterocellular engineered 3D tissue constructs and their engraftment via tissue fusion and has implications for arrhythmogenesis in cardiac disease and repair.
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Affiliation(s)
- Tae Yun Kim
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, RI, United States of America
| | - Celinda M. Kofron
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, RI, United States of America
- Center for Biomedical Engineering, School of Engineering, Brown University, Providence, RI, United States of America
| | - Michelle E. King
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, RI, United States of America
| | - Alexander R. Markes
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, RI, United States of America
- Division of Biology and Medicine, Brown University, Providence, RI, United States of America
| | - Amenawon O. Okundaye
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, RI, United States of America
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, RI, United States of America
| | - Zhilin Qu
- Division of Cardiology, Department of Medicine, University of California, Los Angeles, CA, United States of America
| | - Ulrike Mende
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, RI, United States of America
| | - Bum-Rak Choi
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, RI, United States of America
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21
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Hichri E, Abriel H, Kucera JP. Distribution of cardiac sodium channels in clusters potentiates ephaptic interactions in the intercalated disc. J Physiol 2018; 596:563-589. [PMID: 29210458 DOI: 10.1113/jp275351] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 11/20/2017] [Indexed: 01/18/2023] Open
Abstract
KEY POINTS It has been proposed that ephaptic conduction, relying on interactions between the sodium (Na+ ) current and the extracellular potential in intercalated discs, might contribute to cardiac conduction when gap junctional coupling is reduced, but this mechanism is still controversial. In intercalated discs, Na+ channels form clusters near gap junction plaques, but the functional significance of these clusters has never been evaluated. In HEK cells expressing cardiac Na+ channels, we show that restricting the extracellular space modulates the Na+ current, as predicted by corresponding simulations accounting for ephaptic effects. In a high-resolution model of the intercalated disc, clusters of Na+ channels that face each other across the intercellular cleft facilitate ephaptic impulse transmission when gap junctional coupling is reduced. Thus, our simulations reveal a functional role for the clustering of Na+ channels in intercalated discs, and suggest that rearrangement of these clusters in disease may influence cardiac conduction. ABSTRACT It has been proposed that ephaptic interactions in intercalated discs, mediated by extracellular potentials, contribute to cardiac impulse propagation when gap junctional coupling is reduced. However, experiments demonstrating ephaptic effects on the cardiac Na+ current (INa ) are scarce. Furthermore, Na+ channels form clusters around gap junction plaques, but the electrophysiological significance of these clusters has never been investigated. In patch clamp experiments with HEK cells stably expressing human Nav 1.5 channels, we examined how restricting the extracellular space modulates INa elicited by an activation protocol. In parallel, we developed a high-resolution computer model of the intercalated disc to investigate how the distribution of Na+ channels influences ephaptic interactions. Approaching the HEK cells to a non-conducting obstacle always increased peak INa at step potentials near the threshold of INa activation and decreased peak INa at step potentials far above threshold (7 cells, P = 0.0156, Wilcoxon signed rank test). These effects were consistent with corresponding control simulations with a uniform Na+ channel distribution. In the intercalated disc computer model, redistributing the Na+ channels into a central cluster of the disc potentiated ephaptic effects. Moreover, ephaptic impulse transmission from one cell to another was facilitated by clusters of Na+ channels facing each other across the intercellular cleft when gap junctional coupling was reduced. In conclusion, our proof-of-principle experiments demonstrate that confining the extracellular space modulates cardiac INa , and our simulations reveal the functional role of the aggregation of Na+ channels in the perinexus. These findings highlight novel concepts in the physiology of cardiac excitation.
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Affiliation(s)
- Echrak Hichri
- Department of Physiology, University of Bern, Bern, Switzerland
| | - Hugues Abriel
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Jan P Kucera
- Department of Physiology, University of Bern, Bern, Switzerland
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22
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Schmidt C, Peyronnet R. Voltage-gated and stretch-activated potassium channels in the human heart : Pathophysiological and clinical significance. Herzschrittmacherther Elektrophysiol 2018; 29:36-42. [PMID: 29305705 DOI: 10.1007/s00399-017-0541-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 11/14/2017] [Indexed: 12/14/2022]
Abstract
Ion channels are essential for electrical signaling and contractility in cardiomyocytes. Detailed knowledge about the molecular function and regulation of cardiac ion channels is crucial for understanding cardiac physiology and pathophysiology especially in the field of arrhythmias. This review aims at providing a general overview on the identity, functional characteristics, and roles of voltage-gated as well as stretch-activated potassium selective channels in the heart. In particular, we will highlight potential therapeutic targets as well as the emerging fields of future investigations.
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Affiliation(s)
- Constanze Schmidt
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Rémi Peyronnet
- Institute for Experimental Cardiovascular Medicine, University Heart Center, Medical Center - University of Freiburg, and Faculty of Medicine, University of Freiburg, Elsässer Straße 2q, 79110, Freiburg, Germany.
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23
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See VY. Organized atrial arrhythmias after cardiac transplantation: The overlooked value of the 12-lead electrocardiogram and cavotricuspid atrial flutter isthmus. J Heart Lung Transplant 2017; 37:S1053-2498(17)32084-3. [PMID: 29129369 DOI: 10.1016/j.healun.2017.10.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 10/18/2017] [Indexed: 11/17/2022] Open
Affiliation(s)
- Vincent Y See
- Cardiovascular Medicine Division, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland.
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Lee TM, Harn HJ, Chiou TW, Chuang MH, Chen CH, Lin PC, Lin SZ. Targeting the pathway of GSK-3β/nerve growth factor to attenuate post-infarction arrhythmias by preconditioned adipose-derived stem cells. J Mol Cell Cardiol 2017; 104:17-30. [PMID: 28130118 DOI: 10.1016/j.yjmcc.2017.01.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 01/01/2017] [Accepted: 01/23/2017] [Indexed: 10/20/2022]
Abstract
Adipose-derived stem cell (ADSC) transplantation is a promising new therapy to improve cardiac function after myocardial infarction. However, its low efficacy of transdifferentiation hampers its usefulness. Glycogen synthase kinase-3β (GSK-3β) signal has been shown to play a role in preconditioning-induced cardioprotection. We assessed whether n-butylidenephthalide (BP) primed ADSCs can attenuate arrhythmias by a GSK-3β-dependent pathway after myocardial infarction. Male Wistar rats after coronary ligation was randomly allocated to receive intramyocardial injection of vehicle, ADSCs, BP-preconditioned ADSCs, (BP+lithium)-preconditioned ADSCs, (BP+SB216763)-preconditioned ADSCs, and (BP+LY294002)-preconditioned ADSCs. ADSCs were primed for 16h before implantation. After 4weeks of implantation, ADSCs were retained in myocardium, reduced fibrosis and improved cardiac function. Sympathetic hyperinnervation was blunted after administering ADSCs, assessed by immunofluorescent analysis, and Western blotting and real-time quantitative RT-PCR of nerve growth factor. Arrhythmic scores during programmed stimulation in the ADSC-treated infarcted rats were significantly lower than vehicle. BP-preconditioned ADSCs had superior cardioprotection, greater ADSC engraftment and transdifferentiation, and antiarrhythmic effects compared with ADSCs alone. Simultaneously, BP increased the levels of phospho-Akt and down-regulated GSK-3β activity. The effects of BP against sympathetic hyperinnervation were blocked by LY294002, a PI3K inhibitor. Addition of either lithium or SB216763 did not have additional effects compared with BP alone. Compared with ADSC alone, BP-primed ADSC implantation improved stem cell engraftment and attenuated sympathetic hyperinnervation and arrhythmias through a PI3K/Akt/GSK-3β-dependent pathway, suggesting that a synergic action was achieved between BP pretreatment and ADSCs.
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Affiliation(s)
- Tsung-Ming Lee
- Department of Medicine, Cardiology Section, China Medical University-An Nan Hospital, Tainan, Taiwan; Department of Medicine, China Medical University, Taichung, Taiwan
| | - Horng-Jyh Harn
- Bioinnovation Center, Tzu Chi Foundation; Department of Pathology, Buddhist Tzu Chi General Hospital, Tzu Chi University
| | - Tzyy-Wen Chiou
- Department of Life Science, Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan
| | - Ming-Hsi Chuang
- Gwo Xi Stem Cell Applied Technology, Hsinchu, Taiwan; Department of Bioinformatics, Chung Hua University, Hsinchu, Taiwan
| | | | - Po-Cheng Lin
- Gwo Xi Stem Cell Applied Technology, Hsinchu, Taiwan
| | - Shinn-Zong Lin
- Bioinnovation Center, Tzu Chi Foundation; Department of Neurosurgery, Buddhist Tzu Chi General Hospital, Tzu Chi University.
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