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Chen YC, Shih CL, Wu CL, Fang YH, So EC, Wu SN. Exploring the Impact of BK Ca Channel Function in Cellular Membranes on Cardiac Electrical Activity. Int J Mol Sci 2024; 25:1537. [PMID: 38338830 PMCID: PMC10855144 DOI: 10.3390/ijms25031537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 01/14/2024] [Accepted: 01/19/2024] [Indexed: 02/12/2024] Open
Abstract
This review paper delves into the current body of evidence, offering a thorough analysis of the impact of large-conductance Ca2+-activated K+ (BKCa or BK) channels on the electrical dynamics of the heart. Alterations in the activity of BKCa channels, responsible for the generation of the overall magnitude of Ca2+-activated K+ current at the whole-cell level, occur through allosteric mechanisms. The collaborative interplay between membrane depolarization and heightened intracellular Ca2+ ion concentrations collectively contribute to the activation of BKCa channels. Although fully developed mammalian cardiac cells do not exhibit functional expression of these ion channels, evidence suggests their presence in cardiac fibroblasts that surround and potentially establish close connections with neighboring cardiac cells. When cardiac cells form close associations with fibroblasts, the high single-ion conductance of these channels, approximately ranging from 150 to 250 pS, can result in the random depolarization of the adjacent cardiac cell membranes. While cardiac fibroblasts are typically electrically non-excitable, their prevalence within heart tissue increases, particularly in the context of aging myocardial infarction or atrial fibrillation. This augmented presence of BKCa channels' conductance holds the potential to amplify the excitability of cardiac cell membranes through effective electrical coupling between fibroblasts and cardiomyocytes. In this scenario, this heightened excitability may contribute to the onset of cardiac arrhythmias. Moreover, it is worth noting that the substances influencing the activity of these BKCa channels might influence cardiac electrical activity as well. Taken together, the BKCa channel activity residing in cardiac fibroblasts may contribute to cardiac electrical function occurring in vivo.
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Affiliation(s)
- Yin-Chia Chen
- Division of Cardiovascular Surgery, Department of Surgery, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi City 60002, Taiwan
| | - Chia-Lung Shih
- Clinical Research Center, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi City 60056, Taiwan
| | - Chao-Liang Wu
- Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi City 60002, Taiwan
| | - Yi-Hsien Fang
- Institute of Clinical Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan 70403, Taiwan
| | - Edmund Cheung So
- Department of Anesthesia, An Nan Hospital, China Medical University, Tainan 70965, Taiwan
| | - Sheng-Nan Wu
- Department of Research and Education, An Nan Hospital, China Medical University, Tainan 70965, Taiwan
- School of Medicine, College of Medicine, National Sun Yat-sen University, Kaohsiung 80421, Taiwan
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2
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Simon-Chica A, Wülfers EM, Kohl P. Nonmyocytes as electrophysiological contributors to cardiac excitation and conduction. Am J Physiol Heart Circ Physiol 2023; 325:H475-H491. [PMID: 37417876 PMCID: PMC10538996 DOI: 10.1152/ajpheart.00184.2023] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 06/22/2023] [Accepted: 06/29/2023] [Indexed: 07/08/2023]
Abstract
Although cardiac action potential (AP) generation and propagation have traditionally been attributed exclusively to cardiomyocytes (CM), other cell types in the heart are also capable of forming electrically conducting junctions. Interactions between CM and nonmyocytes (NM) enable and modulate each other's activity. This review provides an overview of the current understanding of heterocellular electrical communication in the heart. Although cardiac fibroblasts were initially thought to be electrical insulators, recent studies have demonstrated that they form functional electrical connections with CM in situ. Other NM, such as macrophages, have also been recognized as contributing to cardiac electrophysiology and arrhythmogenesis. Novel experimental tools have enabled the investigation of cell-specific activity patterns in native cardiac tissue, which is expected to yield exciting new insights into the development of novel or improved diagnostic and therapeutic strategies.
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Affiliation(s)
- Ana Simon-Chica
- Novel Arrhythmogenic Mechanisms Program, Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain
| | - Eike M Wülfers
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Department of Physics and Astronomy, Faculty of Sciences, Ghent University, Gent, Belgium
| | - Peter Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Faculty of Medicine, University of Freiburg, Freiburg, Germany
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3
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Zheng H, Peri L, Ward GK, Sanders KM, Ward SM. Cardiac PDGFRα + interstitial cells generate spontaneous inward currents that contribute to excitability in the heart. FASEB J 2023; 37:e22929. [PMID: 37086093 PMCID: PMC10402933 DOI: 10.1096/fj.202201712r] [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: 10/20/2022] [Revised: 03/06/2023] [Accepted: 04/05/2023] [Indexed: 04/23/2023]
Abstract
The cell types and conductance that contribute to normal cardiac functions remain under investigation. We used mice that express an enhanced green fluorescent protein (eGFP)-histone 2B fusion protein driven off the cell-specific endogenous promoter for Pdgfra to investigate the distribution and functional role of PDGFRα+ cells in the heart. Cardiac PDGFRα+ cells were widely distributed within the endomysium of atria, ventricle, and sino-atrial node (SAN) tissues. PDGFRα+ cells formed a discrete network of cells, lying in close apposition to neighboring cardiac myocytes in mouse and Cynomolgus monkey (Macaca fascicularis) hearts. Expression of eGFP in nuclei allowed unequivocal identification of these cells following enzymatic dispersion of muscle tissues. FACS purification of PDGFRα+ cells from the SAN and analysis of gene transcripts by qPCR revealed that they were a distinct population of cells that expressed gap junction transcripts, Gja1 and Gjc1. Cardiac PDGFRα+ cells generated spontaneous transient inward currents (STICs) and spontaneous transient depolarizations (STDs) that reversed at 0 mV. Reversal potential was maintained when ECl = -40 mV. [Na+ ]o replacement and FTY720 abolished STICs, suggesting they were due to a non-selective cation conductance (NSCC) carried by TRPM7. PDGFRα+ cells also express β2 -adrenoceptor gene transcripts, Adrb2. Zinterol, a selective β2 -receptor agonist, increased the amplitude and frequency of STICs, suggesting these cells could contribute to adrenergic regulation of cardiac excitability. PDGFRα+ cells in cardiac muscles generate inward currents via an NSCC. STICs generated by these cells may contribute to the integrated membrane potentials of cardiac muscles, possibly affecting the frequency of pacemaker activity.
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Affiliation(s)
- Haifeng Zheng
- Department of Physiology & Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, 89557, USA
| | - Lauren Peri
- Department of Physiology & Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, 89557, USA
| | - Grace K. Ward
- Department of Physiology & Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, 89557, USA
| | - Kenton M. Sanders
- Department of Physiology & Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, 89557, USA
| | - Sean M. Ward
- Department of Physiology & Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, 89557, USA
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4
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Xing C, Bao L, Li W, Fan H. Progress on role of ion channels of cardiac fibroblasts in fibrosis. Front Physiol 2023; 14:1138306. [PMID: 36969589 PMCID: PMC10033868 DOI: 10.3389/fphys.2023.1138306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 02/27/2023] [Indexed: 03/29/2023] Open
Abstract
Cardiac fibrosis is defined as excessive deposition of extracellular matrix (ECM) in pathological conditions. Cardiac fibroblasts (CFs) activated by injury or inflammation differentiate into myofibroblasts (MFs) with secretory and contractile functions. In the fibrotic heart, MFs produce ECM which is composed mainly of collagen and is initially involved in maintaining tissue integrity. However, persistent fibrosis disrupts the coordination of excitatory contractile coupling, leading to systolic and diastolic dysfunction, and ultimately heart failure. Numerous studies have demonstrated that both voltage- and non-voltage-gated ion channels alter intracellular ion levels and cellular activity, contributing to myofibroblast proliferation, contraction, and secretory function. However, an effective treatment strategy for myocardial fibrosis has not been established. Therefore, this review describes the progress made in research related to transient receptor potential (TRP) channels, Piezo1, Ca2+ release-activated Ca2+ (CRAC) channels, voltage-gated Ca2+ channels (VGCCs), sodium channels, and potassium channels in myocardial fibroblasts with the aim of providing new ideas for treating myocardial fibrosis.
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5
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Liu F, Wu H, Yang X, Dong Y, Huang G, Genin GM, Lu TJ, Xu F. A new model of myofibroblast-cardiomyocyte interactions and their differences across species. Biophys J 2021; 120:3764-3775. [PMID: 34280368 DOI: 10.1016/j.bpj.2021.06.040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 06/02/2021] [Accepted: 06/28/2021] [Indexed: 11/18/2022] Open
Abstract
Although coupling between cardiomyocytes and myofibroblasts is well known to affect the physiology and pathophysiology of cardiac tissues across species, relating these observations to humans is challenging because the effect of this coupling varies across species and because the sources of these effects are not known. To identify the sources of cross-species variation, we built upon previous mathematical models of myofibroblast electrophysiology and developed a mechanoelectrical model of cardiomyocyte-myofibroblast interactions as mediated by electrotonic coupling and transforming growth factor-β1. The model, as verified by experimental data from the literature, predicted that both electrotonic coupling and transforming growth factor-β1 interaction between myocytes and myofibroblast prolonged action potential in rat myocytes but shortened action potential in human myocytes. This variance could be explained by differences in the transient outward K+ current associated with differential Kv4.2 gene expression across species. Results are useful for efforts to extrapolate the results of animal models to the predicted effects in humans and point to potential therapeutic targets for fibrotic cardiomyopathy.
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Affiliation(s)
- Fusheng Liu
- State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi'an, P.R. China; Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an, P.R. China; Bioinspired Engineering and Biomechanics Center, Xi'an Jiaotong University, Xi'an, P.R. China
| | - Hou Wu
- State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi'an, P.R. China; Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an, P.R. China
| | - Xiaoyu Yang
- State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi'an, P.R. China; Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an, P.R. China
| | - Yuqin Dong
- Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an, P.R. China; Bioinspired Engineering and Biomechanics Center, Xi'an Jiaotong University, Xi'an, P.R. China
| | - Guoyou Huang
- Department of Engineering Mechanics, School of Civil Engineering, Wuhan University, Wuhan, P.R. China
| | - Guy M Genin
- Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an, P.R. China; Bioinspired Engineering and Biomechanics Center, Xi'an Jiaotong University, Xi'an, P.R. China; Department of Mechanical Engineering & Materials Science, St. Louis, Missouri; NSF Science and Technology Center for Engineering Mechanobiology, Washington University in St. Louis, St. Louis, Missouri
| | - Tian Jian Lu
- State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing, P.R. China.
| | - Feng Xu
- Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an, P.R. China; Bioinspired Engineering and Biomechanics Center, Xi'an Jiaotong University, Xi'an, P.R. China.
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Jakob D, Klesen A, Darkow E, Kari FA, Beyersdorf F, Kohl P, Ravens U, Peyronnet R. Heterogeneity and Remodeling of Ion Currents in Cultured Right Atrial Fibroblasts From Patients With Sinus Rhythm or Atrial Fibrillation. Front Physiol 2021; 12:673891. [PMID: 34149453 PMCID: PMC8209389 DOI: 10.3389/fphys.2021.673891] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 04/19/2021] [Indexed: 11/23/2022] Open
Abstract
Cardiac fibroblasts express multiple voltage-dependent ion channels. Even though fibroblasts do not generate action potentials, they may influence cardiac electrophysiology by electrical coupling via gap junctions with cardiomyocytes, and through fibrosis. Here, we investigate the electrophysiological phenotype of cultured fibroblasts from right atrial appendage tissue of patients with sinus rhythm (SR) or atrial fibrillation (AF). Using the patch-clamp technique in whole-cell mode, we observed steady-state outward currents exhibiting either no rectification or inward and/or outward rectification. The distributions of current patterns between fibroblasts from SR and AF patients were not significantly different. In response to depolarizing voltage pulses, we measured transient outward currents with fast and slow activation kinetics, an outward background current, and an inward current with a potential-dependence resembling that of L-type Ca2+ channels. In cell-attached patch-clamp mode, large amplitude, paxilline-sensitive single channel openings were found in ≈65% of SR and ∼38% of AF fibroblasts, suggesting the presence of “big conductance Ca2+-activated K+ (BKCa)” channels. The open probability of BKCa was significantly lower in AF than in SR fibroblasts. When cultured in the presence of paxilline, the shape of fibroblasts became wider and less spindle-like. Our data confirm previous findings on cardiac fibroblast electrophysiology and extend them by illustrating differential channel expression in human atrial fibroblasts from SR and AF tissue.
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Affiliation(s)
- Dorothee Jakob
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg - Bad Krozingen, Freiburg, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Alexander Klesen
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg - Bad Krozingen, Freiburg, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Elisa Darkow
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg - Bad Krozingen, Freiburg, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany.,Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, Freiburg, Germany.,Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Fabian A Kari
- Medical Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany.,Department of Cardiovascular Surgery, University Heart Center Freiburg - Bad Krozingen, Freiburg, Germany
| | - Friedhelm Beyersdorf
- Medical Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany.,Department of Cardiovascular Surgery, University Heart Center Freiburg - Bad Krozingen, Freiburg, Germany
| | - Peter Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg - Bad Krozingen, Freiburg, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany.,CIBSS Centre for Integrative Biological Signaling Studies, University of Freiburg, Freiburg, Germany
| | - Ursula Ravens
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg - Bad Krozingen, Freiburg, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Rémi Peyronnet
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg - Bad Krozingen, Freiburg, Germany.,Medical Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany
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7
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Lu T, Mar JC. Investigating transcriptome-wide sex dimorphism by multi-level analysis of single-cell RNA sequencing data in ten mouse cell types. Biol Sex Differ 2020; 11:61. [PMID: 33153500 PMCID: PMC7643324 DOI: 10.1186/s13293-020-00335-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Accepted: 10/11/2020] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND It is a long established fact that sex is an important factor that influences the transcriptional regulatory processes of an organism. However, understanding sex-based differences in gene expression has been limited because existing studies typically sequence and analyze bulk tissue from female or male individuals. Such analyses average cell-specific gene expression levels where cell-to-cell variation can easily be concealed. We therefore sought to utilize data generated by the rapidly developing single cell RNA sequencing (scRNA-seq) technology to explore sex dimorphism and its functional consequences at the single cell level. METHODS Our study included scRNA-seq data of ten well-defined cell types from the brain and heart of female and male young adult mice in the publicly available tissue atlas dataset, Tabula Muris. We combined standard differential expression analysis with the identification of differential distributions in single cell transcriptomes to test for sex-based gene expression differences in each cell type. The marker genes that had sex-specific inter-cellular changes in gene expression formed the basis for further characterization of the cellular functions that were differentially regulated between the female and male cells. We also inferred activities of transcription factor-driven gene regulatory networks by leveraging knowledge of multidimensional protein-to-genome and protein-to-protein interactions and analyzed pathways that were potential modulators of sex differentiation and dimorphism. RESULTS For each cell type in this study, we identified marker genes with significantly different mean expression levels or inter-cellular distribution characteristics between female and male cells. These marker genes were enriched in pathways that were closely related to the biological functions of each cell type. We also identified sub-cell types that possibly carry out distinct biological functions that displayed discrepancies between female and male cells. Additionally, we found that while genes under differential transcriptional regulation exhibited strong cell type specificity, six core transcription factor families responsible for most sex-dimorphic transcriptional regulation activities were conserved across the cell types, including ASCL2, EGR, GABPA, KLF/SP, RXRα, and ZF. CONCLUSIONS We explored novel gene expression-based biomarkers, functional cell group compositions, and transcriptional regulatory networks associated with sex dimorphism with a novel computational pipeline. Our findings indicated that sex dimorphism might be widespread across the transcriptomes of cell types, cell type-specific, and impactful for regulating cellular activities.
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Affiliation(s)
- Tianyuan Lu
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD, 4072, Australia.,Quantitative Life Sciences Program, McGill University, Montreal, QC, H3A 0G4, Canada
| | - Jessica C Mar
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD, 4072, Australia.
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8
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Roach KM, Bradding P. Ca 2+ signalling in fibroblasts and the therapeutic potential of K Ca3.1 channel blockers in fibrotic diseases. Br J Pharmacol 2020; 177:1003-1024. [PMID: 31758702 DOI: 10.1111/bph.14939] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 10/23/2019] [Accepted: 11/13/2019] [Indexed: 12/13/2022] Open
Abstract
The role of Ca2+ signalling in fibroblasts is of great interest in fibrosis-related diseases. Intracellular free Ca2+ ([Ca2+ ]i ) is a ubiquitous secondary messenger, regulating a number of cellular functions such as secretion, metabolism, differentiation, proliferation and contraction. The intermediate conductance Ca2+ -activated K+ channel KCa 3.1 is pivotal in Ca2+ signalling and plays a central role in fibroblast processes including cell activation, migration and proliferation through the regulation of cell membrane potential. Evidence from a number of approaches demonstrates that KCa 3.1 plays an important role in the development of many fibrotic diseases, including idiopathic pulmonary, renal tubulointerstitial fibrosis and cardiovascular disease. The KCa 3.1 selective blocker senicapoc was well tolerated in clinical trials for sickle cell disease, raising the possibility of rapid translation to the clinic for people suffering from pathological fibrosis. This review after analysing all the data, concludes that targeting KCa 3.1 should be a high priority for human fibrotic disease.
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Affiliation(s)
- Katy M Roach
- Institute for Lung Health, Department of Respiratory Sciences, University of Leicester, Leicester, UK
| | - Peter Bradding
- Institute for Lung Health, Department of Respiratory Sciences, University of Leicester, Leicester, UK
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9
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Zhan H, Zhang J, Jiao A, Wang Q. Stretch-activated current in human atrial myocytes and Na + current and mechano-gated channels' current in myofibroblasts alter myocyte mechanical behavior: a computational study. Biomed Eng Online 2019; 18:104. [PMID: 31653259 PMCID: PMC6814973 DOI: 10.1186/s12938-019-0723-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 10/16/2019] [Indexed: 12/19/2022] Open
Abstract
Background The activation of stretch-activated channels (SACs) in cardiac myocytes, which changes the phases of action potential repolarization, is proven to be highly efficient for the conversion of atrial fibrillation. The expression of Na+ current in myofibroblasts (Mfbs) regenerates myocytes’ action potentials, suggesting that Mfbs play an active role in triggering cardiac rhythm disturbances. Moreover, the excitation of mechano-gated channels (MGCs) in Mfbs depolarizes their membrane potential and contributes to the increased risk of post-infarct arrhythmia. Although these electrophysiological mechanisms have been largely known, the roles of these currents in cardiac mechanics are still debated. In this study, we aimed to investigate the mechanical influence of these currents via mathematical modeling. A novel mathematical model was developed by integrating models of human atrial myocyte (including the stretch-activated current, Ca2+–force relation, and mechanical behavior of a single segment) and Mfb (including our formulation of Na+ current and mechano-gated channels’ current). The effects of the changes in basic cycle length, number of coupled Mfbs and intercellular coupling conductance on myocyte mechanical properties were compared. Results Our results indicated that these three currents significantly regulated myocyte mechanical parameters. In isosarcometric contraction, these currents increased segment force by 13.8–36.6% and dropped element length by 12.1–31.5%. In isotonic contraction, there are 2.7–5.9% growth and 0.9–24% reduction. Effects of these currents on the extremum of myocyte mechanical parameters become more significant with the increase of basic cycle length, number of coupled Mfbs and intercellular coupling conductance. Conclusions The results demonstrated that stretch-activated current in myocytes and Na+ current and mechano-gated channels’ current in Mfbs significantly influenced myocyte mechanical behavior and should be considered in future cardiac mechanical mathematical modeling.
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Affiliation(s)
- Heqing Zhan
- College of Medical Information, Hainan Medical University, Haikou, 571199, China.
| | - Jingtao Zhang
- Cardiac Arrhythmia Center, Fuwai Hospital, National Center for Cardiovascular Diseases, Beijing, 100037, China
| | - Anquan Jiao
- College of Medical Information, Hainan Medical University, Haikou, 571199, China
| | - Qin Wang
- College of Medical Information, Hainan Medical University, Haikou, 571199, China
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10
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Feng J, Armillei MK, Yu AS, Liang BT, Runnels LW, Yue L. Ca 2+ Signaling in Cardiac Fibroblasts and Fibrosis-Associated Heart Diseases. J Cardiovasc Dev Dis 2019; 6:E34. [PMID: 31547577 PMCID: PMC6956282 DOI: 10.3390/jcdd6040034] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2019] [Revised: 09/16/2019] [Accepted: 09/18/2019] [Indexed: 12/13/2022] Open
Abstract
Cardiac fibrosis is the excessive deposition of extracellular matrix proteins by cardiac fibroblasts and myofibroblasts, and is a hallmark feature of most heart diseases, including arrhythmia, hypertrophy, and heart failure. This maladaptive process occurs in response to a variety of stimuli, including myocardial injury, inflammation, and mechanical overload. There are multiple signaling pathways and various cell types that influence the fibrogenesis cascade. Fibroblasts and myofibroblasts are central effectors. Although it is clear that Ca2+ signaling plays a vital role in this pathological process, what contributes to Ca2+ signaling in fibroblasts and myofibroblasts is still not wholly understood, chiefly because of the large and diverse number of receptors, transporters, and ion channels that influence intracellular Ca2+ signaling. Intracellular Ca2+ signals are generated by Ca2+ release from intracellular Ca2+ stores and by Ca2+ entry through a multitude of Ca2+-permeable ion channels in the plasma membrane. Over the past decade, the transient receptor potential (TRP) channels have emerged as one of the most important families of ion channels mediating Ca2+ signaling in cardiac fibroblasts. TRP channels are a superfamily of non-voltage-gated, Ca2+-permeable non-selective cation channels. Their ability to respond to various stimulating cues makes TRP channels effective sensors of the many different pathophysiological events that stimulate cardiac fibrogenesis. This review focuses on the mechanisms of Ca2+ signaling in fibroblast differentiation and fibrosis-associated heart diseases and will highlight recent advances in the understanding of the roles that TRP and other Ca2+-permeable channels play in cardiac fibrosis.
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Affiliation(s)
- Jianlin Feng
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06030, USA.
| | - Maria K Armillei
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06030, USA.
| | - Albert S Yu
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06030, USA.
| | - Bruce T Liang
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06030, USA.
| | - Loren W Runnels
- Department of Pharmacology, Rutgers, Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
| | - Lixia Yue
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06030, USA.
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11
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Rubart M, Tao W, Lu XL, Conway SJ, Reuter SP, Lin SF, Soonpaa MH. Electrical coupling between ventricular myocytes and myofibroblasts in the infarcted mouse heart. Cardiovasc Res 2019; 114:389-400. [PMID: 29016731 DOI: 10.1093/cvr/cvx163] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 08/10/2017] [Indexed: 12/20/2022] Open
Abstract
Aims Recent studies have demonstrated electrotonic coupling between scar tissue and the surrounding myocardium in cryoinjured hearts. However, the electrical dynamics occurring at the myocyte-nonmyocyte interface in the fibrotic heart remain undefined. Here, we sought to develop an assay to interrogate the nonmyocyte cell type contributing to heterocellular coupling and to characterize, on a cellular scale, its voltage response in the infarct border zone of living hearts. Methods and results We used two-photon laser scanning microscopy in conjunction with a voltage-sensitive dye to record transmembrane voltage changes simultaneously from cardiomyocytes and adjoined nonmyocytes in Langendorff-perfused mouse hearts with healing myocardial infarction. Transgenic mice with cardiomyocyte-restricted expression of a green fluorescent reporter protein underwent permanent coronary artery ligation and their hearts were subjected to voltage imaging 7-10 days later. Reporter-negative cells, i.e. nonmyocytes, in the infarct border zone exhibited depolarizing transients at a 1:1 coupling ratio with action potentials recorded simultaneously from adjacent, reporter-positive ventricular myocytes. The electrotonic responses in the nonmyocytes exhibited slower rates of de- and repolarization compared to the action potential waveform of juxtaposed myocytes. Voltage imaging in infarcted hearts expressing a fluorescent reporter specifically in myofibroblasts revealed that the latter were electrically coupled to border zone myocytes. Their voltage transient properties were indistinguishable from those of nonmyocytes in hearts with cardiomyocyte-restricted reporter expression. The density of connexin43 expression at myofibroblast-cardiomyocyte junctions was ∼5% of that in the intercalated disc regions of paired ventricular myocytes in the remote, uninjured myocardium, whereas the ratio of connexin45 to connexin43 expression levels at heterocellular contacts was ∼1%. Conclusion Myofibroblasts contribute to the population of electrically coupled nonmyocytes in the infarct border zone. The slower kinetics of myofibroblast voltage responses may reflect low electrical conductivity across heterocellular junctions, in accordance with the paucity of connexin expression at myofibroblast-cardiomyocyte contacts.
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Affiliation(s)
- Michael Rubart
- Wells Centre for Pediatric Research, Indiana University School of Medicine, 1044 West Walnut Street, Indianapolis, IN 46202, USA
| | - Wen Tao
- Wells Centre for Pediatric Research, Indiana University School of Medicine, 1044 West Walnut Street, Indianapolis, IN 46202, USA
| | - Xiao-Long Lu
- Wells Centre for Pediatric Research, Indiana University School of Medicine, 1044 West Walnut Street, Indianapolis, IN 46202, USA
| | - Simon J Conway
- Wells Centre for Pediatric Research, Indiana University School of Medicine, 1044 West Walnut Street, Indianapolis, IN 46202, USA
| | - Sean P Reuter
- Wells Centre for Pediatric Research, Indiana University School of Medicine, 1044 West Walnut Street, Indianapolis, IN 46202, USA
| | - Shien-Fong Lin
- Institute of Biomedical Engineering, National Chiao Tung University, Hsinchu, Taiwan
| | - Mark H Soonpaa
- Wells Centre for Pediatric Research, Indiana University School of Medicine, 1044 West Walnut Street, Indianapolis, IN 46202, USA.,Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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12
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Ischemia Reperfusion Injury Produces, and Ischemic Preconditioning Prevents, Rat Cardiac Fibroblast Differentiation: Role of K ATP Channels. J Cardiovasc Dev Dis 2019; 6:jcdd6020022. [PMID: 31167469 PMCID: PMC6617075 DOI: 10.3390/jcdd6020022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 05/30/2019] [Accepted: 05/31/2019] [Indexed: 02/04/2023] Open
Abstract
Ischemic preconditioning (IPC) and activation of ATP-sensitive potassium channels (KATP) protect cardiac myocytes from ischemia reperfusion (IR) injury. We investigated the influence of IR injury, IPC and KATP in isolated rat cardiac fibroblasts. Hearts were removed under isoflurane anesthesia. IR was simulated in vitro by application and removal of paraffin oil over pelleted cells. Ischemia (30, 60 and 120 min) followed by 60 min reperfusion resulted in significant differentiation of fibroblasts into myofibroblasts in culture (mean % fibroblasts ± SEM in IR vs. time control: 12 ± 1% vs. 63 ± 2%, 30 min ischemia; 15 ± 3% vs. 71 ± 4%, 60 min ischemia; 8 ± 1% vs. 55 ± 2%, 120 min ischemia). IPC (15 min ischemia, 30 min reperfusion) significantly attenuated IR-induced fibroblast differentiation (52 ± 3%) compared to 60 min IR. IPC was mimicked by opening KATP with pinacidil (50 μM; 43 ± 6%) and by selectively opening mitochondrial KATP (mKATP) with diazoxide (100 μM; 53 ± 3%). Furthermore, IPC was attenuated by inhibiting KATP with glibenclamide (10 μM; 23 ± 5%) and by selectively blocking mKATP with 5-hydroxydecanoate (100 μM; 22 ± 9%). These results suggest that (a) IR injury evoked cardiac fibroblast to myofibroblast differentiation, (b) IPC attenuated IR-induced fibroblast differentiation, (c) KATP were involved in IPC and (d) this protection involved selective activation of mKATP.
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Bragard J, Sankarankutty AC, Sachse FB. Extended Bidomain Modeling of Defibrillation: Quantifying Virtual Electrode Strengths in Fibrotic Myocardium. Front Physiol 2019; 10:337. [PMID: 31001135 PMCID: PMC6456788 DOI: 10.3389/fphys.2019.00337] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 03/13/2019] [Indexed: 11/17/2022] Open
Abstract
Defibrillation is a well-established therapy for atrial and ventricular arrhythmia. Here, we shed light on defibrillation in the fibrotic heart. Using the extended bidomain model of electrical conduction in cardiac tissue, we assessed the influence of fibrosis on the strength of virtual electrodes caused by extracellular electrical current. We created one-dimensional models of rabbit ventricular tissue with a central patch of fibrosis. The fibrosis was incorporated by altering volume fractions for extracellular, myocyte and fibroblast domains. In our prior work, we calculated these volume fractions from microscopic images at the infarct border zone of rabbit hearts. An average and a large degree of fibrosis were modeled. We simulated defibrillation by application of an extracellular current for a short duration (5 ms). We explored the effects of myocyte-fibroblast coupling, intra-fibroblast conductivity and patch length on the strength of the virtual electrodes present at the borders of the normal and fibrotic tissue. We discriminated between effects on myocyte and fibroblast membranes at both borders of the patch. Similarly, we studied defibrillation in two-dimensional models of fibrotic tissue. Square and disk-like patches of fibrotic tissue were embedded in control tissue. We quantified the influence of the geometry and fibrosis composition on virtual electrode strength. We compared the results obtained with a square and disk shape of the fibrotic patch with results from the one-dimensional simulations. Both, one- and two-dimensional simulations indicate that extracellular current application causes virtual electrodes at boundaries of fibrotic patches. A higher degree of fibrosis and larger patch size were associated with an increased strength of the virtual electrodes. Also, patch geometry affected the strength of the virtual electrodes. Our simulations suggest that increased fibroblast-myocyte coupling and intra-fibroblast conductivity reduce virtual electrode strength. However, experimental data to constrain these modeling parameters are limited and thus pinpointing the magnitude of the reduction will require further understanding of electrical coupling of fibroblasts in native cardiac tissues. We propose that the findings from our computational studies are important for development of patient-specific protocols for internal defibrillators.
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Affiliation(s)
- Jean Bragard
- Department of Physics and Applied Mathematics, University of Navarra, Pamplona, Spain
| | - Aparna C. Sankarankutty
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, United States
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, United States
| | - Frank B. Sachse
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, United States
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, United States
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Lee H, Kim KC, Hong YM. Change of voltage-gated potassium channel 1.7 expressions in monocrotaline-induced pulmonary arterial hypertension rat model. KOREAN JOURNAL OF PEDIATRICS 2018; 61:271-278. [PMID: 30274504 PMCID: PMC6172520 DOI: 10.3345/kjp.2018.06457] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 06/01/2018] [Indexed: 11/27/2022]
Abstract
Purpose Abnormal potassium channels expression affects vessel function, including vascular tone and proliferation rate. Diverse potassium channels, including voltage-gated potassium (Kv) channels, are involved in pathological changes of pulmonary arterial hypertension (PAH). Since the role of the Kv1.7 channel in PAH has not been previously studied, we investigated whether Kv1.7 channel expression changes in the lung tissue of a monocrotaline (MCT)-induced PAH rat model and whether this change is influenced by the endothelin (ET)-1 and reactive oxygen species (ROS) pathways. Methods Rats were separated into 2 groups: the control (C) group and the MCT (M) group (60 mg/kg MCT). A hemodynamic study was performed by catheterization into the external jugular vein to estimate the right ventricular pressure (RVP), and pathological changes in the lung tissue were investigated. Changes in protein and mRNA levels were confirmed by western blot and polymerase chain reaction analysis, respectively. Results MCT caused increased RVP, medial wall thickening of the pulmonary arterioles, and increased expression level of ET-1, ET receptor A, and NADPH oxidase (NOX) 4 proteins. Decreased Kv1.7 channel expression was detected in the lung tissue. Inward-rectifier channel 6.1 expression in the lung tissue also increased. We confirmed that ET-1 increased NOX4 level and decreased glutathione peroxidase-1 level in pulmonary artery smooth muscle cells (PASMCs). ET-1 increased ROS level in PASMCs. Conclusion Decreased Kv1.7 channel expression might be caused by the ET-1 and ROS pathways and contributes to MCT-induced PAH.
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Affiliation(s)
- Hyeryon Lee
- Department of Pediatrics, Ewha Womans University School of Medicine, Seoul, Korea
| | - Kwan Chang Kim
- Department of Thoracic and Cardiovascular Surgery, Ewha Womans University School of Medicine, Seoul, Korea
| | - Young Mi Hong
- Department of Pediatrics, Ewha Womans University School of Medicine, Seoul, Korea
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15
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Hatano N, Ohya S, Imaizumi Y, Clark RB, Belke D, Giles WR. ATP increases [Ca 2+ ] i and activates a Ca 2+ -dependent Cl - current in rat ventricular fibroblasts. Exp Physiol 2018; 103:666-682. [PMID: 29493027 DOI: 10.1113/ep086822] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 02/22/2018] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Although electrophysiological and biophysical characteristics of heart fibroblasts have been studied in detail, their responses to prominent paracrine agents in the myocardium have not been addressed adequately. Our experiments characterize changes in cellular electrophysiology and intracellular calcium in response to ATP. What is the main finding and its importance? In rat ventricular fibroblasts maintained in cell culture, we find that ATP activates a specific subset of Ca2+ -activated Cl- channels as a consequence of binding to P2Y purinoceptors and then activating phospholipase C. This response is not dependent on [Ca2+ ]o but requires an increase in [Ca2+ ]i and is modulated by the type of nucleotide that is the purinergic agonist. ABSTRACT Effects of ATP on enzymatically isolated rat ventricular fibroblasts maintained in short-term (36-72 h) cell culture were examined. Immunocytochemical staining of these cells revealed that a fibroblast, as opposed to a myofibroblast, phenotype was predominant. ATP, ADP or uridine 5'-triphosphate (UTP) all produced large increases in [Ca2+ ]i . Voltage-clamp studies (amphotericin-perforated patch) showed that ATP (1-100 μm) activated an outwardly rectifying current, with a reversal potential very close to the Nernst potential for Cl- . In contrast, ADP was much less effective, and UTP produced no detectable current. The non-selective Cl- channel blockers niflumic acid, DIDS and NPPB (each at 100 μm), blocked the responses to 100 μm ATP. An agonist for P2Y purinoceptors, 2-MTATP, activated a very similar outwardly rectifying C1- current. The P2Y receptor antagonists, suramin and PPADS (100 μm each), significantly inhibited the Cl- current produced by 100 μm ATP. ATP was able to activate this Cl- current when [Ca2+ ]o was removed, but not when [Ca2+ ]i was buffered with BAPTA-AM. In the presence of the phospholipase C inhibitor U73122, this Cl- current could not be activated. PCR analysis revealed strong signals for a number of P2Y purinoceptors and for the Ca2+ -activated Cl- channel, TMEM16F (also denoted ANO6). In summary, these results demonstrate that activation of P2Y receptors by ATP causes a phospholipase C-dependent increase in [Ca2+ ]i , followed by activation of a Ca2+ -dependent Cl- current in rat ventricular fibroblasts.
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Affiliation(s)
- Noriyuki Hatano
- Laboratory of Cellular Pharmacology, School of Pharmacy, Aichi-Gakuin University, Nagoya, Japan
| | - Susumu Ohya
- Department of Pharmacology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, 467-8601, Japan
| | - Yuji Imaizumi
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, 467-8603, Japan
| | - Robert B Clark
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Darrell Belke
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Wayne R Giles
- Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
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16
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Institution of localized high-frequency electrical stimulation targeting early myocardial infarction: Effects on left ventricle function and geometry. J Thorac Cardiovasc Surg 2018; 156:568-575. [PMID: 29609885 DOI: 10.1016/j.jtcvs.2018.01.104] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 12/20/2017] [Accepted: 01/13/2018] [Indexed: 11/21/2022]
Abstract
BACKGROUND Although strategies have focused on myocardial salvage/regeneration in the context of an acute coronary syndrome and a myocardial infarction (MI), interventions targeting the formed MI region and altering the course of the post-MI remodeling process have not been as well studied. This study tested the hypothesis that localized high-frequency stimulation instituted within a formed MI region using low-amplitude electrical pulses would favorably change the trajectory of changes in left ventricle geometry and function. METHODS At 7 days following MI induction, pigs were randomized for localized high-frequency stimulation (n = 5, 240 bpm, 0.8 V, and 0.05 ms pulses) or unstimulated (n = 6). Left ventricle geometry and function were measured at baseline (pre-MI) and at 7, 14, 21, and 28 days post-MI using echocardiography. MI size at 28 days post-MI was determined by histochemical staining and planimetry. RESULTS At 7 days post-MI and before randomization to localized high-frequency stimulation, left ventricular ejection fraction and end-diastolic volume was equivalent. However, when compared with 7-day post-MI values, left ventricle end-diastolic volume increased in a time-dependent manner in the MI unstimulated group, but the relative increase in left ventricle end-diastolic volume was reduced in the MI localized high-frequency stimulation group. For example, by 28 days post-MI, left ventricle end-diastolic volume increased by 32% in the MI unstimulated group but only by 12% in the MI localized high-frequency stimulation group (P < .05). Whereas left ventricular ejection fraction appeared unchanged between MI groups, estimates of pulmonary capillary wedge pressure, a marker of adverse left ventricle performance and progression to failure, increased by 62% in the MI unstimulated group and actually decreased by 17% in the MI localized high-frequency stimulation group when compared with 7-day post-MI values (P < .05). MI size was equivalent between the MI groups, indicative of no difference in the extent of absolute myocardial injury. CONCLUSIONS The unique findings from this study are 2-fold. First, targeting the MI region following the resolution of the acute event using a localized stimulation approach is feasible. Second, localized stimulation modified a key parameter of adverse post-MI remodeling (dilation) and progression to heart failure. These findings demonstrate that the MI region itself is a modifiable tissue and responsive to localized electrical stimulation.
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17
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Vasavan T, Ferraro E, Ibrahim E, Dixon P, Gorelik J, Williamson C. Heart and bile acids - Clinical consequences of altered bile acid metabolism. Biochim Biophys Acta Mol Basis Dis 2018; 1864:1345-1355. [PMID: 29317337 DOI: 10.1016/j.bbadis.2017.12.039] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 12/18/2017] [Accepted: 12/22/2017] [Indexed: 12/11/2022]
Abstract
Cardiac dysfunction has an increased prevalence in diseases complicated by liver cirrhosis such as primary biliary cholangitis and primary sclerosing cholangitis. This observation has led to research into the association between abnormalities in bile acid metabolism and cardiac pathology. Approximately 50% of liver cirrhosis cases develop cirrhotic cardiomyopathy. Bile acids are directly implicated in this, causing QT interval prolongation, cardiac hypertrophy, cardiomyocyte apoptosis and abnormal haemodynamics of the heart. Elevated maternal serum bile acids in intrahepatic cholestasis of pregnancy, a disorder which causes an impaired feto-maternal bile acid gradient, have been associated with fatal fetal arrhythmias. The hydrophobicity of individual bile acids in the serum bile acid pool is of relevance, with relatively lipophilic bile acids having a more harmful effect on the heart. Ursodeoxycholic acid can reverse or protect against these detrimental cardiac effects of elevated bile acids.
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Affiliation(s)
- Tharni Vasavan
- Department of Women and Children's Health, King's College London, Guy's Campus, Hodgkin Building, SE1 1UL London, United Kingdom
| | - Elisa Ferraro
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, Du Cane Road, W12 0NN London, United Kingdom
| | - Effendi Ibrahim
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, Du Cane Road, W12 0NN London, United Kingdom; Faculty of Medicine, MARA University of Technology, 40000 Sungai Buloh, Malaysia
| | - Peter Dixon
- Department of Women and Children's Health, King's College London, Guy's Campus, Hodgkin Building, SE1 1UL London, United Kingdom
| | - Julia Gorelik
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, Du Cane Road, W12 0NN London, United Kingdom
| | - Catherine Williamson
- Department of Women and Children's Health, King's College London, Guy's Campus, Hodgkin Building, SE1 1UL London, United Kingdom.
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18
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Bae H, Lim I. Effects of nitric oxide on large-conductance Ca 2+ -activated K + currents in human cardiac fibroblasts through PKA and PKG-related pathways. Clin Exp Pharmacol Physiol 2017; 44:1116-1124. [PMID: 28731589 DOI: 10.1111/1440-1681.12817] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Revised: 06/29/2017] [Accepted: 07/11/2017] [Indexed: 01/22/2023]
Abstract
The human cardiac fibroblast (HCF) is the most abundant cell type in the myocardium, and HCFs play critical roles in maintaining normal cardiac function. However, unlike cardiomyocytes, the electrophysiology of HCFs is not well established. In the cardiovascular system, Ca2+ -activated K+ (KCa) channels have distinct physiological and pathological functions, and nitric oxide (NO) plays a key role. In this study, we investigated the potential effects of NO on KCa channels in HCFs. We recorded strong oscillating, well-maintained outward K+ currents without marked inactivation throughout the test pulse period and detected outward rectification in the I-V curve; these are all characteristics that are typical of KCa currents. These currents were blocked with iberiotoxin (IBTX, a BKCa blocker) but not with TRAM-34 (an IKCa blocker). The amplitudes of the currents were increased with SNAP (an NO donor), and these increases were inhibited with IBTX. The SNAP-stimulating effect on the BKCa currents was blocked by pretreatment with KT5823 (a protein kinase G [PKG] inhibitor) or 1 H-[1,-2, -4] oxadiazolo-[4,-3-a] quinoxalin-1-one (ODQ; a soluble guanylate cyclase inhibitor). Additionally, 8-bromo-cyclic guanosine 3',5'-monophosphate (8-Br-cGMP) stimulated the BKCa currents, and pretreatment with KT5720 (a protein kinase A [PKA] inhibitor) and SQ22536 (an adenylyl cyclase inhibitor) blocked the NO-stimulating effect on the BKCa currents. Furthermore, 8-bromo-cyclic adenosine 3',5'-monophosphate (8-Br-cAMP) activated the BKCa currents. These data suggest that BKCa current is the main subtype of the KCa current in HCFs and that NO enhances these currents through the PKG and PKA pathways.
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Affiliation(s)
- Hyemi Bae
- Department of Physiology, College of Medicine, Chung-Ang University, Seoul, Korea
| | - Inja Lim
- Department of Physiology, College of Medicine, Chung-Ang University, Seoul, Korea
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19
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Kofron CM, Kim TY, King ME, Xie A, Feng F, Park E, Qu Z, Choi BR, Mende U. G q-activated fibroblasts induce cardiomyocyte action potential prolongation and automaticity in a three-dimensional microtissue environment. Am J Physiol Heart Circ Physiol 2017; 313:H810-H827. [PMID: 28710068 DOI: 10.1152/ajpheart.00181.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 06/13/2017] [Accepted: 07/03/2017] [Indexed: 11/22/2022]
Abstract
Cardiac fibroblasts (CFs) are known to regulate cardiomyocyte (CM) function in vivo and in two-dimensional in vitro cultures. This study examined the effect of CF activation on the regulation of CM electrical activity in a three-dimensional (3-D) microtissue environment. Using a scaffold-free 3-D platform with interspersed neonatal rat ventricular CMs and CFs, Gq-mediated signaling was selectively enhanced in CFs by Gαq adenoviral infection before coseeding with CMs in nonadhesive hydrogels. After 3 days, the microtissues were analyzed by signaling assay, histological staining, quantitative PCR, Western blots, optical mapping with voltage- or Ca2+-sensitive dyes, and microelectrode recordings of CF resting membrane potential (RMPCF). Enhanced Gq signaling in CFs increased microtissue size and profibrotic and prohypertrophic markers. Expression of constitutively active Gαq in CFs prolonged CM action potential duration (by 33%) and rise time (by 31%), prolonged Ca2+ transient duration (by 98%) and rise time (by 65%), and caused abnormal electrical activity based on depolarization-induced automaticity. Constitutive Gq activation in CFs also depolarized RMPCF from -33 to -20 mV and increased connexin 43 and connexin 45 expression. Computational modeling confers that elevated RMPCF and increased cell-cell coupling between CMs and CFs in a 3-D environment could lead to automaticity. In conclusion, our data demonstrate that CF activation alone is capable of altering action potential and Ca2+ transient characteristics of CMs, leading to proarrhythmic electrical activity. Our results also emphasize the importance of a 3-D environment where cell-cell interactions are prevalent, underscoring that CF activation in 3-D tissue plays a significant role in modulating CM electrophysiology and arrhythmias.NEW & NOTEWORTHY In a three-dimensional microtissue model, which lowers baseline activation of cardiac fibroblasts but enables cell-cell, paracrine, and cell-extracellular matrix interactions, we demonstrate that selective cardiac fibroblast activation by enhanced Gq signaling, a pathophysiological trigger in the diseased heart, modulates cardiomyocyte electrical activity, leading to proarrhythmogenic automaticity.
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Affiliation(s)
- C M Kofron
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, Rhode Island; and
| | - T Y Kim
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, Rhode Island; and
| | - M E King
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, Rhode Island; and
| | - A Xie
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, Rhode Island; and
| | - F Feng
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, Rhode Island; and
| | - E Park
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, Rhode Island; and
| | - Z Qu
- Department of Medicine, University of California, Los Angeles, California
| | - B-R Choi
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, Rhode Island; and
| | - U Mende
- Cardiovascular Research Center, Cardiovascular Institute, Rhode Island Hospital and Alpert Medical School of Brown University, Providence, Rhode Island; and
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20
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Sridhar S, Vandersickel N, Panfilov AV. Effect of myocyte-fibroblast coupling on the onset of pathological dynamics in a model of ventricular tissue. Sci Rep 2017; 7:40985. [PMID: 28106124 PMCID: PMC5247688 DOI: 10.1038/srep40985] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 12/13/2016] [Indexed: 12/23/2022] Open
Abstract
Managing lethal cardiac arrhythmias is one of the biggest challenges in modern cardiology, and hence it is very important to understand the factors underlying such arrhythmias. While early afterdepolarizations (EAD) of cardiac cells is known to be one such arrhythmogenic factor, the mechanisms underlying the emergence of tissue level arrhythmias from cellular level EADs is not fully understood. Another known arrhythmogenic condition is fibrosis of cardiac tissue that occurs both due to aging and in many types of heart diseases. In this paper we describe the results of a systematic in-silico study, using the TNNP model of human cardiac cells and MacCannell model for (myo)fibroblasts, on the possible effects of diffuse fibrosis on arrhythmias occurring via EADs. We find that depending on the resting potential of fibroblasts (VFR), M-F coupling can either increase or decrease the region of parameters showing EADs. Fibrosis increases the probability of occurrence of arrhythmias after a single focal stimulation and this effect increases with the strength of the M-F coupling. While in our simulations, arrhythmias occur due to fibrosis induced ectopic activity, we do not observe any specific fibrotic pattern that promotes the occurrence of these ectopic sources.
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Affiliation(s)
- S. Sridhar
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
| | - Nele Vandersickel
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
| | - Alexander V. Panfilov
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
- Moscow Institute of Physics and Technology (State University), Dolgoprudny, Moscow Region, Russia
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21
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Effects of Na + Current and Mechanogated Channels in Myofibroblasts on Myocyte Excitability and Repolarization. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2016; 2016:6189374. [PMID: 27980607 PMCID: PMC5131562 DOI: 10.1155/2016/6189374] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 10/09/2016] [Accepted: 10/19/2016] [Indexed: 12/19/2022]
Abstract
Fibrotic remodeling, characterized by fibroblast phenotype switching, is often associated with atrial fibrillation and heart failure. This study aimed to investigate the effects on electrotonic myofibroblast-myocyte (Mfb-M) coupling on cardiac myocytes excitability and repolarization of the voltage-gated sodium channels (VGSCs) and single mechanogated channels (MGCs) in human atrial Mfbs. Mathematical modeling was developed from a combination of (1) models of the human atrial myocyte (including the stretch activated ion channel current, ISAC) and Mfb and (2) our formulation of currents through VGSCs (INa_Mfb) and MGCs (IMGC_Mfb) based upon experimental findings. The effects of changes in the intercellular coupling conductance, the number of coupled Mfbs, and the basic cycle length on the myocyte action potential were simulated. The results demonstrated that the integration of ISAC, INa_Mfb, and IMGC_Mfb reduced the amplitude of the myocyte membrane potential (Vmax) and the action potential duration (APD), increased the depolarization of the resting myocyte membrane potential (Vrest), and made it easy to trigger spontaneous excitement in myocytes. For Mfbs, significant electrotonic depolarizations were exhibited with the addition of INa_Mfb and IMGC_Mfb. Our results indicated that ISAC, INa_Mfb, and IMGC_Mfb significantly influenced myocytes and Mfbs properties and should be considered in future cardiac pathological mathematical modeling.
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22
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Morgan R, Colman MA, Chubb H, Seemann G, Aslanidi OV. Slow Conduction in the Border Zones of Patchy Fibrosis Stabilizes the Drivers for Atrial Fibrillation: Insights from Multi-Scale Human Atrial Modeling. Front Physiol 2016; 7:474. [PMID: 27826248 PMCID: PMC5079097 DOI: 10.3389/fphys.2016.00474] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Accepted: 10/03/2016] [Indexed: 01/12/2023] Open
Abstract
Introduction: The genesis of atrial fibrillation (AF) and success of AF ablation therapy have been strongly linked with atrial fibrosis. Increasing evidence suggests that patient-specific distributions of fibrosis may determine the locations of electrical drivers (rotors) sustaining AF, but the underlying mechanisms are incompletely understood. This study aims to elucidate a missing mechanistic link between patient-specific fibrosis distributions and AF drivers. Methods: 3D atrial models integrated human atrial geometry, rule-based fiber orientation, region-specific electrophysiology, and AF-induced ionic remodeling. A novel detailed model for an atrial fibroblast was developed, and effects of myocyte-fibroblast (M-F) coupling were explored at single-cell, 1D tissue and 3D atria levels. Left atrial LGE MRI datasets from 3 chronic AF patients were segmented to provide the patient-specific distributions of fibrosis. The data was non-linearly registered and mapped to the 3D atria model. Six distinctive fibrosis levels (0-healthy tissue, 5-dense fibrosis) were identified based on LGE MRI intensity and modeled as progressively increasing M-F coupling and decreasing atrial tissue coupling. Uniform 3D atrial model with diffuse (level 2) fibrosis was considered for comparison. Results: In single cells and tissue, the largest effect of atrial M-F coupling was on the myocyte resting membrane potential, leading to partial inactivation of sodium current and reduction of conduction velocity (CV). In the 3D atria, further to the M-F coupling, effects of fibrosis on tissue coupling greatly reduce atrial CV. AF was initiated by fast pacing in each 3D model with either uniform or patient-specific fibrosis. High variation in fibrosis distributions between the models resulted in varying complexity of AF, with several drivers emerging. In the diffuse fibrosis models, waves randomly meandered through the atria, whereas in each the patient-specific models, rotors stabilized in fibrotic regions. The rotors propagated slowly around the border zones of patchy fibrosis (levels 3-4), failing to spread into inner areas of dense fibrosis. Conclusion: Rotors stabilize in the border zones of patchy fibrosis in 3D atria, where slow conduction enable the development of circuits within relatively small regions. Our results can provide a mechanistic explanation for the clinical efficacy of ablation around fibrotic regions.
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Affiliation(s)
- Ross Morgan
- Division of Imaging Sciences and Biomedical Engineering, Department of Biomedical Engineering, King's College LondonLondon, UK
| | | | - Henry Chubb
- Division of Imaging Sciences and Biomedical Engineering, Department of Biomedical Engineering, King's College LondonLondon, UK
| | - Gunnar Seemann
- Institute for Experimental Cardiovascular Medicine, University Heart Center - Bad Krozingen, Medical Center - University of FreiburgFreiburg, Germany
| | - Oleg V. Aslanidi
- Division of Imaging Sciences and Biomedical Engineering, Department of Biomedical Engineering, King's College LondonLondon, UK
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23
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Chacar S, Farès N, Bois P, Faivre JF. Basic Signaling in Cardiac Fibroblasts. J Cell Physiol 2016; 232:725-730. [DOI: 10.1002/jcp.25624] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 09/28/2016] [Indexed: 12/14/2022]
Affiliation(s)
- Stéphanie Chacar
- Laboratoire Signalisation et Transports Ioniques Membranaires (STIM); Université de Poitiers; CNRS; Poitiers France
- Laboratoire de recherche en Physiologie et Physiopathologie (LRPP); pôle technologie santé; Faculté de Médecine; Université Saint Joseph; Beyrouth Liban
| | - Nassim Farès
- Laboratoire de recherche en Physiologie et Physiopathologie (LRPP); pôle technologie santé; Faculté de Médecine; Université Saint Joseph; Beyrouth Liban
| | - Patrick Bois
- Laboratoire Signalisation et Transports Ioniques Membranaires (STIM); Université de Poitiers; CNRS; Poitiers France
| | - Jean-François Faivre
- Laboratoire Signalisation et Transports Ioniques Membranaires (STIM); Université de Poitiers; CNRS; Poitiers France
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Zeigler AC, Richardson WJ, Holmes JW, Saucerman JJ. Computational modeling of cardiac fibroblasts and fibrosis. J Mol Cell Cardiol 2016; 93:73-83. [PMID: 26608708 PMCID: PMC4846515 DOI: 10.1016/j.yjmcc.2015.11.020] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 11/18/2015] [Accepted: 11/18/2015] [Indexed: 12/31/2022]
Abstract
Altered fibroblast behavior can lead to pathologic changes in the heart such as arrhythmia, diastolic dysfunction, and systolic dysfunction. Computational models are increasingly used as a tool to identify potential mechanisms driving a phenotype or potential therapeutic targets against an unwanted phenotype. Here we review how computational models incorporating cardiac fibroblasts have clarified the role for these cells in electrical conduction and tissue remodeling in the heart. Models of fibroblast signaling networks have primarily focused on fibroblast cell lines or fibroblasts from other tissues rather than cardiac fibroblasts, specifically, but they are useful for understanding how fundamental signaling pathways control fibroblast phenotype. In the future, modeling cardiac fibroblast signaling, incorporating -omics and drug-interaction data into signaling network models, and utilizing multi-scale models will improve the ability of in silico studies to predict potential therapeutic targets against adverse cardiac fibroblast activity.
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Affiliation(s)
- Angela C Zeigler
- University of Virginia, Biomedical Engineering Department, 415 Lane Road, Charlottesville, VA 22903, USA.
| | - William J Richardson
- University of Virginia, Biomedical Engineering Department, 415 Lane Road, Charlottesville, VA 22903, USA.
| | - Jeffrey W Holmes
- University of Virginia, Biomedical Engineering Department, 415 Lane Road, Charlottesville, VA 22903, USA.
| | - Jeffrey J Saucerman
- University of Virginia, Biomedical Engineering Department, 415 Lane Road, Charlottesville, VA 22903, USA.
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25
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Ongstad E, Kohl P. Fibroblast-myocyte coupling in the heart: Potential relevance for therapeutic interventions. J Mol Cell Cardiol 2016; 91:238-46. [PMID: 26774702 DOI: 10.1016/j.yjmcc.2016.01.010] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 01/09/2016] [Accepted: 01/11/2016] [Indexed: 01/03/2023]
Abstract
Cardiac myocyte-fibroblast electrotonic coupling is a well-established fact in vitro. Indirect evidence of its presence in vivo exists, but few functional studies have been published. This review describes the current knowledge of fibroblast-myocyte electrical signaling in the heart. Further research is needed to understand the frequency and extent of heterocellular interactions in vivo in order to gain a better understanding of their relevance in healthy and diseased myocardium. It is hoped that associated insight into myocyte-fibroblast coupling in the heart may lead to the discovery of novel therapeutic targets and the development of agents for improving outcomes of myocardial scarring and fibrosis.
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Affiliation(s)
- Emily Ongstad
- Clemson University, Department of Bioengineering, Clemson, SC, USA; Virginia Tech Carilion Research Institute, Roanoke, VA, USA.
| | - Peter Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Centre Freiburg - Bad Krozingen, Faculty of Medicine, University Freiburg, Germany; Cardiac Biophysics and Systems Biology, National Heart and Lung Institute, Imperial College London, UK
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26
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Schultz F, Hasan A, Alvarez-Laviada A, Miragoli M, Bhogal N, Wells S, Poulet C, Chambers J, Williamson C, Gorelik J. The protective effect of ursodeoxycholic acid in an in vitro model of the human fetal heart occurs via targeting cardiac fibroblasts. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 120:149-63. [PMID: 26777584 DOI: 10.1016/j.pbiomolbio.2016.01.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 01/05/2016] [Accepted: 01/06/2016] [Indexed: 12/27/2022]
Abstract
Bile acids are elevated in the blood of women with intrahepatic cholestasis of pregnancy (ICP) and this may lead to fetal arrhythmia, fetal hypoxia and potentially fetal death in utero. The bile acid taurocholic acid (TC) causes abnormal calcium dynamics and contraction in neonatal rat cardiomyocytes. Ursodeoxycholic acid (UDCA), a drug clinically used to treat ICP, prevents adverse effects of TC. During development, the fetus is in a state of relative hypoxia. Although this is essential for the development of the heart and vasculature, resident fibroblasts can transiently differentiate into myofibroblasts and form gap junctions with cardiomyocytes in vitro, resulting in cardiomyocyte depolarization. We expanded on previously published work using an in vitro hypoxia model to investigate the differentiation of human fetal fibroblasts into myofibroblasts. Recent evidence shows that potassium channels are involved in maintaining the membrane potential of ventricular fibroblasts and that ATP-dependent potassium (KATP) channel subunits are expressed in cultured fibroblasts. KATP channels are a valuable target as they are thought to have a cardioprotective role during ischaemic and hypoxic conditions. We investigated whether UDCA could modulate fibroblast membrane potential. We established the isolation and culture of human fetal cardiomyocytes and fibroblasts to investigate the effect of hypoxia, TC and UDCA on human fetal cardiac cells. UDCA hyperpolarized myofibroblasts and prevented TC-induced depolarisation, possibly through the activation of KATP channels that are expressed in cultured fibroblasts. Also, similar to the rat model, UDCA can counteract TC-induced calcium abnormalities in human fetal cultures of cardiomyocytes and myofibroblasts. Under normoxic conditions, we found a higher number of myofibroblasts in cultures derived from human fetal hearts compared to cells isolated from neonatal rat hearts, indicating a possible increased number of myofibroblasts in human fetal hearts. Hypoxia further increased the number of human fetal and rat neonatal myofibroblasts. However, chronically administered UDCA reduced the number of myofibroblasts and prevented hypoxia-induced depolarisation. In conclusion, our results show that the protective effect of UDCA involves both the reduction of fibroblast differentiation into myofibroblasts, and hyperpolarisation of myofibroblasts, most likely through the stimulation of potassium channels, i.e. KATP channels. This could be important in validating UDCA as an antifibrotic and antiarrhythmic drug for treatment of failing hearts and fetal arrhythmia.
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Affiliation(s)
- Francisca Schultz
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, UK; Institute of Reproductive and Developmental Biology, Imperial College London, London, UK
| | - Alveera Hasan
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, UK
| | - Anita Alvarez-Laviada
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, UK
| | - Michele Miragoli
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, UK; Humanitas Clinical and Research Institute, Rozzano, Italy
| | - Navneet Bhogal
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, UK
| | - Sarah Wells
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, UK
| | - Claire Poulet
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, UK
| | - Jenny Chambers
- Institute of Reproductive and Developmental Biology, Imperial College London, London, UK; Women's Health Academic Centre, King's College London, London, United Kingdom
| | - Catherine Williamson
- Institute of Reproductive and Developmental Biology, Imperial College London, London, UK; Women's Health Academic Centre, King's College London, London, United Kingdom
| | - Julia Gorelik
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, UK.
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Moghtadaei M, Polina I, Rose RA. Electrophysiological effects of natriuretic peptides in the heart are mediated by multiple receptor subtypes. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 120:37-49. [DOI: 10.1016/j.pbiomolbio.2015.12.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 11/25/2015] [Accepted: 12/02/2015] [Indexed: 12/13/2022]
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Mahoney VM, Mezzano V, Morley GE. A review of the literature on cardiac electrical activity between fibroblasts and myocytes. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2015; 120:128-33. [PMID: 26713556 DOI: 10.1016/j.pbiomolbio.2015.12.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 11/12/2015] [Accepted: 12/16/2015] [Indexed: 12/13/2022]
Abstract
Myocardial injuries often lead to fibrotic deposition. This review presents evidence supporting the concept that fibroblasts in the heart electrically couple to myocytes.
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Affiliation(s)
- Vanessa M Mahoney
- Leon H. Charney Division of Cardiology, Department of Medicine, New York University School of Medicine, New York, NY 10016, USA
| | - Valeria Mezzano
- Leon H. Charney Division of Cardiology, Department of Medicine, New York University School of Medicine, New York, NY 10016, USA
| | - Gregory E Morley
- Leon H. Charney Division of Cardiology, Department of Medicine, New York University School of Medicine, New York, NY 10016, USA.
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A Computational Study of the Factors Influencing the PVC-Triggering Ability of a Cluster of Early Afterdepolarization-Capable Myocytes. PLoS One 2015; 10:e0144979. [PMID: 26675670 PMCID: PMC4682961 DOI: 10.1371/journal.pone.0144979] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 11/25/2015] [Indexed: 12/02/2022] Open
Abstract
Premature ventricular complexes (PVCs), which are abnormal impulse propagations in cardiac tissue, can develop because of various reasons including early afterdepolarizations (EADs). We show how a cluster of EAD-generating cells (EAD clump) can lead to PVCs in a model of cardiac tissue, and also investigate the factors that assist such clumps in triggering PVCs. In particular, we study, through computer simulations, the effects of the following factors on the PVC-triggering ability of an EAD clump: (1) the repolarization reserve (RR) of the EAD cells; (2) the size of the EAD clump; (3) the coupling strength between the EAD cells in the clump; and (4) the presence of fibroblasts in the EAD clump. We find that, although a low value of RR is necessary to generate EADs and hence PVCs, a very low value of RR leads to low-amplitude EAD oscillations that decay with time and do not lead to PVCs. We demonstrate that a certain threshold size of the EAD clump, or a reduction in the coupling strength between the EAD cells, in the clump, is required to trigger PVCs. We illustrate how randomly distributed inexcitable obstacles, which we use to model collagen deposits, affect PVC-triggering by an EAD clump. We show that the gap-junctional coupling of fibroblasts with myocytes can either assist or impede the PVC-triggering ability of an EAD clump, depending on the resting membrane potential of the fibroblasts and the coupling strength between the myocyte and fibroblasts. We also find that the triggering of PVCs by an EAD clump depends sensitively on factors like the pacing cycle length and the distribution pattern of the fibroblasts.
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Computational Approaches to Understanding the Role of Fibroblast-Myocyte Interactions in Cardiac Arrhythmogenesis. BIOMED RESEARCH INTERNATIONAL 2015; 2015:465714. [PMID: 26601107 PMCID: PMC4637154 DOI: 10.1155/2015/465714] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Revised: 04/10/2015] [Accepted: 04/29/2015] [Indexed: 11/18/2022]
Abstract
The adult heart is composed of a dense network of cardiomyocytes surrounded by nonmyocytes, the most
abundant of which are cardiac fibroblasts. Several cardiac diseases, such as myocardial infarction or dilated
cardiomyopathy, are associated with an increased density of fibroblasts, that is, fibrosis. Fibroblasts play a
significant role in the development of electrical and mechanical dysfunction of the heart; however the underlying
mechanisms are only partially understood. One widely studied mechanism suggests that fibroblasts produce
excess extracellular matrix, resulting in collagenous septa. These collagenous septa slow propagation, cause
zig-zag conduction paths, and decouple cardiomyocytes resulting in a substrate for arrhythmia. Another
emerging mechanism suggests that fibroblasts promote arrhythmogenesis through direct electrical interactions
with cardiomyocytes via gap junctions. Due to the challenges of investigating fibroblast-myocyte coupling in
native cardiac tissue, computational modeling and in vitro experiments have facilitated the investigation into the
mechanisms underlying fibroblast-mediated changes in cardiomyocyte action potential morphology, conduction
velocity, spontaneous excitability, and vulnerability to reentry. In this paper, we summarize the major findings of
the existing computational studies investigating the implications of fibroblast-myocyte interactions in the normal
and diseased heart. We then present investigations from our group into the potential role of voltage-dependent
gap junctions in fibroblast-myocyte interactions.
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31
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Fibroblast electrical remodeling in heart failure and potential effects on atrial fibrillation. Biophys J 2015; 107:2444-55. [PMID: 25418313 DOI: 10.1016/j.bpj.2014.10.014] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 09/23/2014] [Accepted: 10/08/2014] [Indexed: 11/20/2022] Open
Abstract
Fibroblasts are activated in heart failure (HF) and produce fibrosis, which plays a role in maintaining atrial fibrillation (AF). The effect of HF on fibroblast ion currents and its potential role in AF are unknown. Here, we used a patch-clamp technique to investigate the effects of HF on atrial fibroblast ion currents, and mathematical computation to assess the potential impact of this remodeling on atrial electrophysiology and arrhythmogenesis. Atrial fibroblasts were isolated from control and tachypacing-induced HF dogs. Tetraethylammonium-sensitive voltage-gated fibroblast current (IKv,fb) was significantly downregulated (by ?44%), whereas the Ba(2+)-sensitive inward rectifier current (IKir,fb) was upregulated by 79%, in HF animals versus controls. The fibroblast resting membrane potential was hyperpolarized (?53 ± 2 mV vs. ?42 ± 2 mV in controls) and the capacitance was increased (29.7 ± 2.2 pF vs. 17.8 ± 1.4 pF in controls) in HF. These experimental findings were implemented in a mathematical model that included cardiomyocyte-fibroblast electrical coupling. IKir,fb upregulation had a profibrillatory effect through shortening of the action potential duration and hyperpolarization of the cardiomyocyte resting membrane potential. IKv,fb downregulation had the opposite electrophysiological effects and was antifibrillatory. Simulated pharmacological blockade of IKv,fb successfully terminated reentry under otherwise profibrillatory conditions. We conclude that HF induces fibroblast ion-current remodeling with IKv,fb downregulation and IKir,fb upregulation, and that, assuming cardiomyocyte-fibroblast electrical coupling, this remodeling has a potentially important effect on atrial electrophysiology and arrhythmogenesis, with the overall response depending on the balance of pro- and antifibrillatory contributions. These findings suggest that fibroblast K(+)-current remodeling is a novel component of AF-related remodeling that might contribute to arrhythmia dynamics.
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Tolstokorov AS, Syunyaev RA, Aliev RR. Simulation of the fibroblast effect on electrical activity of sinoatrial node cells. Biophysics (Nagoya-shi) 2015. [DOI: 10.1134/s0006350915020190] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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33
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Dostal D, Glaser S, Baudino TA. Cardiac Fibroblast Physiology and Pathology. Compr Physiol 2015; 5:887-909. [DOI: 10.1002/cphy.c140053] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Zhan HQ, Xia L, Shou GF, Zang YL, Liu F, Crozier S. Fibroblast proliferation alters cardiac excitation conduction and contraction: a computational study. J Zhejiang Univ Sci B 2014; 15:225-42. [PMID: 24599687 DOI: 10.1631/jzus.b1300156] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
In this study, the effects of cardiac fibroblast proliferation on cardiac electric excitation conduction and mechanical contraction were investigated using a proposed integrated myocardial-fibroblastic electromechanical model. At the cellular level, models of the human ventricular myocyte and fibroblast were modified to incorporate a model of cardiac mechanical contraction and cooperativity mechanisms. Cellular electromechanical coupling was realized with a calcium buffer. At the tissue level, electrical excitation conduction was coupled to an elastic mechanics model in which the finite difference method (FDM) was used to solve electrical excitation equations, and the finite element method (FEM) was used to solve mechanics equations. The electromechanical properties of the proposed integrated model were investigated in one or two dimensions under normal and ischemic pathological conditions. Fibroblast proliferation slowed wave propagation, induced a conduction block, decreased strains in the fibroblast proliferous tissue, and increased dispersions in depolarization, repolarization, and action potential duration (APD). It also distorted the wave-front, leading to the initiation and maintenance of re-entry, and resulted in a sustained contraction in the proliferous areas. This study demonstrated the important role that fibroblast proliferation plays in modulating cardiac electromechanical behaviour and which should be considered in planning future heart-modeling studies.
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Affiliation(s)
- He-qing Zhan
- Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, China; School of Information Technology and Electrical Engineering, the University of Queensland, Brisbane QLD 4072, Australia
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Wu CT, Qi XY, Huang H, Naud P, Dawson K, Yeh YH, Harada M, Kuo CT, Nattel S. Disease and region-related cardiac fibroblast potassium current variations and potential functional significance. Cardiovasc Res 2014; 102:487-96. [PMID: 24596399 DOI: 10.1093/cvr/cvu055] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
AIMS Fibroblasts, which play an important role in cardiac function/dysfunction, including arrhythmogenesis, have voltage-dependent (Kv) currents of unknown importance. Here, we assessed the differential expression of Kv currents between atrial and ventricular fibroblasts from control dogs and dogs with an atrial arrhythmogenic substrate caused by congestive heart failure (CHF). METHODS AND RESULTS Left atrial (LA) and ventricular (LV) fibroblasts were freshly isolated from control and CHF dogs (2-week ventricular tachypacing, 240 bpm). Kv currents were measured with whole-cell voltage-clamp, mRNA by quantitative polymerase chain reaction (qPCR) and fibroblast proliferation by (3)H-thymidine incorporation. Robust voltage-dependent tetraethylammonium (TEA)-sensitive K(+) currents (IC50 ∼1 mM) were recorded. The morphologies and TEA responses of LA and LV fibroblast Kv currents were similar. LV fibroblast Kv-current densities were significantly greater than LA, and Kv-current densities were significantly less in CHF than control. The mRNA expression of Kv-channel subunits Kv1.5 and Kv4.3 was less in LA vs. LV fibroblasts and was down-regulated in CHF, consistent with K(+)-current recordings. Ca(2+)-dependent K(+)-channel subunit (KCa1.1) mRNA and currents were less expressed in LV vs. LA fibroblasts. Inhibiting LA fibroblast K(+) current with 1 mmol/L of TEA or KCa1.1 current with paxilline increased proliferation. CONCLUSIONS Fibroblast Kv-current expression is smaller in CHF vs. control, as well as LA vs. LV. KCa1.1 current is greater in LA vs. LV. Suppressing Kv current with TEA enhances fibroblast proliferation, suggesting that Kv current might act to check fibroblast proliferation and that reduced Kv current in CHF may contribute to fibrosis. Fibroblast Kv-current remodelling may play a role in the atrial fibrillation (AF) substrate; modulating fibroblast K(+) channels may present a novel strategy to prevent fibrosis and AF.
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Affiliation(s)
- Chia-Tung Wu
- Research Center, Montreal Heart Institute, Université de Montréal, 5000 Belanger St. E., Montreal, QC, Canada H1T 1C8 Chang-Gung Memorial Hospital and University, Taoyuan, Taiwan, Republic of China
| | - Xiao-Yan Qi
- Research Center, Montreal Heart Institute, Université de Montréal, 5000 Belanger St. E., Montreal, QC, Canada H1T 1C8
| | - Hai Huang
- Research Center, Montreal Heart Institute, Université de Montréal, 5000 Belanger St. E., Montreal, QC, Canada H1T 1C8
| | - Patrice Naud
- Research Center, Montreal Heart Institute, Université de Montréal, 5000 Belanger St. E., Montreal, QC, Canada H1T 1C8
| | - Kristin Dawson
- Research Center, Montreal Heart Institute, Université de Montréal, 5000 Belanger St. E., Montreal, QC, Canada H1T 1C8 Department of Pharmacology and Therapeutics, McGill University, Montreal, QC, Canada
| | - Yung-Hsin Yeh
- Chang-Gung Memorial Hospital and University, Taoyuan, Taiwan, Republic of China
| | - Masahide Harada
- Research Center, Montreal Heart Institute, Université de Montréal, 5000 Belanger St. E., Montreal, QC, Canada H1T 1C8 Department of Cardiology, Hamamatsu Medical Center, Hamamatsu, Japan
| | - Chi-Tai Kuo
- Chang-Gung Memorial Hospital and University, Taoyuan, Taiwan, Republic of China
| | - Stanley Nattel
- Research Center, Montreal Heart Institute, Université de Montréal, 5000 Belanger St. E., Montreal, QC, Canada H1T 1C8 Department of Pharmacology and Therapeutics, McGill University, Montreal, QC, Canada
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ANO1 contributes to Angiotensin-II-activated Ca2+-dependent Cl− current in human atrial fibroblasts. J Mol Cell Cardiol 2014; 68:12-9. [DOI: 10.1016/j.yjmcc.2013.12.027] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Revised: 12/03/2013] [Accepted: 12/31/2013] [Indexed: 01/04/2023]
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Abramochkin DV, Lozinsky IT, Kamkin A. Influence of mechanical stress on fibroblast-myocyte interactions in mammalian heart. J Mol Cell Cardiol 2014; 70:27-36. [PMID: 24389344 DOI: 10.1016/j.yjmcc.2013.12.020] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 12/18/2013] [Accepted: 12/24/2013] [Indexed: 12/18/2022]
Abstract
Cardiac fibroblasts are an essential component of cardiac tissue. These cells not only produce the extracellular matrix, but also are electrically and mechanically coupled with cardiomyocytes. In this way, fibroblasts can influence the electrical activity of cardiomyocytes. Cardiac fibroblasts cannot generate action potentials, but their membrane potential is controlled by mechanical stretch or compression of the surrounding myocardium which in turn affects their interaction with myocytes and the way myocytes respond to mechanical stress. This review discusses the electrical properties of cardiac fibroblasts, the present evidence of fibroblast-myocyte coupling and the way in which these cells respond to mechanical stress. This article is part of a Special Issue entitled "Myocyte-Fibroblast Signalling in Myocardium."
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Affiliation(s)
- Denis V Abramochkin
- Department of Fundamental and Applied Physiology, Russian National Research Medical University, Ostrovityanova str., 1, Moscow, Russia; Department of Human and Animal Physiology, Moscow State University, Leninskiye Gory, 1, 12, Moscow, Russia.
| | - Ilya T Lozinsky
- Department of Fundamental and Applied Physiology, Russian National Research Medical University, Ostrovityanova str., 1, Moscow, Russia
| | - Andre Kamkin
- Department of Fundamental and Applied Physiology, Russian National Research Medical University, Ostrovityanova str., 1, Moscow, Russia
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Nayak AR, Shajahan TK, Panfilov AV, Pandit R. Spiral-wave dynamics in a mathematical model of human ventricular tissue with myocytes and fibroblasts. PLoS One 2013; 8:e72950. [PMID: 24023798 PMCID: PMC3762734 DOI: 10.1371/journal.pone.0072950] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Accepted: 07/15/2013] [Indexed: 11/18/2022] Open
Abstract
Cardiac fibroblasts, when coupled functionally with myocytes, can modulate the electrophysiological properties of cardiac tissue. We present systematic numerical studies of such modulation of electrophysiological properties in mathematical models for (a) single myocyte-fibroblast (MF) units and (b) two-dimensional (2D) arrays of such units; our models build on earlier ones and allow for zero-, one-, and two-sided MF couplings. Our studies of MF units elucidate the dependence of the action-potential (AP) morphology on parameters such as , the fibroblast resting-membrane potential, the fibroblast conductance , and the MF gap-junctional coupling . Furthermore, we find that our MF composite can show autorhythmic and oscillatory behaviors in addition to an excitable response. Our 2D studies use (a) both homogeneous and inhomogeneous distributions of fibroblasts, (b) various ranges for parameters such as , and , and (c) intercellular couplings that can be zero-sided, one-sided, and two-sided connections of fibroblasts with myocytes. We show, in particular, that the plane-wave conduction velocity decreases as a function of , for zero-sided and one-sided couplings; however, for two-sided coupling, decreases initially and then increases as a function of , and, eventually, we observe that conduction failure occurs for low values of . In our homogeneous studies, we find that the rotation speed and stability of a spiral wave can be controlled either by controlling or . Our studies with fibroblast inhomogeneities show that a spiral wave can get anchored to a local fibroblast inhomogeneity. We also study the efficacy of a low-amplitude control scheme, which has been suggested for the control of spiral-wave turbulence in mathematical models for cardiac tissue, in our MF model both with and without heterogeneities.
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Affiliation(s)
- Alok Ranjan Nayak
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore, India
| | - T. K. Shajahan
- Centre for Nonlinear Dynamics in Physiology and Medicine, McGill University, Montreal, Canada
| | - A. V. Panfilov
- Department of Physics and Astronomy, Gent University, Gent, Belgium
| | - Rahul Pandit
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore, India
- Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India
- * E-mail:
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Excitation-contraction coupling between human atrial myocytes with fibroblasts and stretch activated channel current: a simulation study. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2013; 2013:238676. [PMID: 24000290 PMCID: PMC3755441 DOI: 10.1155/2013/238676] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 07/13/2013] [Accepted: 07/13/2013] [Indexed: 12/23/2022]
Abstract
Myocytes have been regarded as the main objectives in most cardiac modeling studies and attracted a lot of attention. Connective tissue cells, such as fibroblasts (Fbs), also play crucial role in cardiac function. This study proposed an integrated myocyte-Isac-Fb electromechanical model to investigate the effect of Fbs and stretch activated ion channel current (Isac) on cardiac electrical excitation conduction and mechanical contraction. At the cellular level, an active Fb model was coupled with a human atrial myocyte electrophysiological model (including Isac) and a mechanical model. At the tissue level, electrical excitation conduction was coupled with an elastic mechanical model, in which finite difference method (FDM) was used to solve the electrical excitation equations, while finite element method (FEM) was used for the mechanics equations. The simulation results showed that Fbs and Isac coupling caused diverse effects on action potential morphology during repolarization, depolarized the resting membrane potential of the human atrial myocyte, slowed down wave propagation, and decreased strains in fibrotic tissue. This preliminary simulation study indicates that Fbs and Isac have important implications for modulating cardiac electromechanical behavior and should be considered in future cardiac modeling studies.
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Klapperstück T, Glanz D, Hanitsch S, Klapperstück M, Markwardt F, Wohlrab J. Calibration procedures for the quantitative determination of membrane potential in human cells using anionic dyes. Cytometry A 2013; 83:612-26. [PMID: 23650268 DOI: 10.1002/cyto.a.22300] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 01/18/2013] [Accepted: 04/02/2013] [Indexed: 12/15/2022]
Abstract
Quantitative determinations of the cell membrane potential of lymphocytes (Wilson et al., J Cell Physiol 1985;125:72-81) and thymocytes (Krasznai et al., J Photochem Photobiol B 1995;28:93-99) using the anionic dye DiBAC4 (3) proved that dye depletion in the extracellular medium as a result of cellular uptake can be negligible over a wide range of cell densities. In contrast, most flow cytometric studies have not verified this condition but rather assumed it from the start. Consequently, the initially prepared extracellular dye concentration has usually been used for the calculation of the Nernst potential of the dye. In this study, however, external dye depletion could be observed in both large IGR-1 and small LCL-HO cells under experimental conditions, which have often been applied routinely in spectrofluorimetry and flow cytometry. The maximum cell density at which dye depletion could be virtually avoided was dependent on cell size and membrane potential and definitely needed to be taken into account to ensure reliable results. In addition, accepted calibration procedures based on the partition of sodium and potassium (Goldman-Hodgkin-Katz equation) or potassium alone (Nernst equation) were performed by flow cytometry on cell suspensions with an appropriately low cell density. The observed extensive lack of concordance between the correspondingly calculated membrane potential and the equilibrium potential of DiBAC4 (3) revealed that these methods require the additional measurement of cation parameters (membrane permeability and/or intracellular concentration). In contrast, due to the linear relation between fluorescence and low DiBAC4 (3) concentrations, the Nernst potential of the dye for totally depolarized cells can be reliably used for calibration with an essentially lower effort and expense.
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Affiliation(s)
- Thomas Klapperstück
- Department of Dermatology and Venereology, Martin Luther University of Halle-Wittenberg, Halle (Saale), Germany.
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Benamer N, Vasquez C, Mahoney VM, Steinhardt MJ, Coetzee WA, Morley GE. Fibroblast KATP currents modulate myocyte electrophysiology in infarcted hearts. Am J Physiol Heart Circ Physiol 2013; 304:H1231-9. [PMID: 23436329 DOI: 10.1152/ajpheart.00878.2012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cardiac metabolism remains altered for an extended period of time after myocardial infarction. Studies have shown fibroblasts from normal hearts express KATP channels in culture. It is unknown whether fibroblasts from infarcted hearts express KATP channels and whether these channels contribute to scar and border zone electrophysiology. KATP channel subunit expression levels were determined in fibroblasts isolated from normal hearts (Fb), and scar (sMI-Fb) and remote (rMI-Fb) regions of left anterior descending coronary artery (LAD) ligated rat hearts. Whole cell KATP current density was determined with patch clamp. Action potential duration (APD) was measured with optical mapping in myocyte-only cultures and heterocellular cultures with fibroblasts with and without 100 μmol/l pinacidil. Whole heart optical mapping was used to assess KATP channel activity following LAD ligation. Pinacidil activated a potassium current (35.4 ± 7.5 pA/pF at 50 mV) in sMI-Fb that was inhibited with 10 μmol/l glibenclamide. Kir6.2 and SUR2 transcript levels were elevated in sMI-Fb. Treatment with Kir6.2 short interfering RNA decreased KATP currents (87%) in sMI-Fb. Treatment with pinacidil decreased APD (26%) in co-cultures with sMI-Fb. APD values were prolonged in LAD ligated hearts after perfusion with glibenclamide. KATP channels are present in fibroblasts from the scar and border zones of infarcted hearts. Activation of fibroblast KATP channels could modulate the electrophysiological substrate beyond the acute ischemic event. Targeting fibroblast KATP channels could represent a novel therapeutic approach to modify border zone electrophysiology after cardiac injury.
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Affiliation(s)
- Najate Benamer
- Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, New York 10016, USA
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42
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Chatelier A, Mercier A, Tremblier B, Thériault O, Moubarak M, Benamer N, Corbi P, Bois P, Chahine M, Faivre JF. A distinct de novo expression of Nav1.5 sodium channels in human atrial fibroblasts differentiated into myofibroblasts. J Physiol 2012; 590:4307-19. [PMID: 22802584 DOI: 10.1113/jphysiol.2012.233593] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Fibroblasts play a major role in heart physiology. They are at the origin of the extracellular matrix renewal and production of various paracrine and autocrine factors. In pathological conditions, fibroblasts proliferate, migrate and differentiate into myofibroblasts leading to cardiac fibrosis. This differentiated status is associated with changes in expression profile leading to neo-expression of proteins such as ionic channels. The present study investigates further electrophysiological changes associated with fibroblast differentiation focusing on the activity of voltage-gated sodium channels in human atrial fibroblasts and myofibroblasts. Using the patch clamp technique we show that human atrial myofibroblasts display a fast inward voltage gated sodium current with a density of 13.28 ± 2.88 pA pF(-1) whereas no current was detectable in non-differentiated fibroblasts. Quantitative RT-PCR reveals a large amount of transcripts encoding the Na(v)1.5 α-subunit with a fourfold increased expression level in myofibroblasts when compared to fibroblasts. Accordingly, half of the current was blocked by 1 μm of tetrodotoxin and immunocytochemistry experiments reveal the presence of Na(v)1.5 proteins. Overall, this current exhibits similar biophysical characteristics to sodium currents found in cardiac myocytes except for the window current that is enlarged for potentials between -100 and -20 mV. Since fibrosis is one of the fundamental mechanisms implicated in atrial fibrillation, it is of great interest to investigate how this current could influence myofibroblast properties. Moreover, since several Na(v)1.5 mutations are related to cardiac pathologies, this study offers a new avenue on the fibroblasts involvement of these mutations.
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Affiliation(s)
- Aurélien Chatelier
- Institut de Physiologie et Biologie Cellulaires, FRE 3511, CNRS/Université de Poitiers, Poitiers, France.
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43
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Takahashi K, Sakamoto K, Kimura J. Hypoxic stress induces transient receptor potential melastatin 2 (TRPM2) channel expression in adult rat cardiac fibroblasts. J Pharmacol Sci 2012; 118:186-97. [PMID: 22293297 DOI: 10.1254/jphs.11128fp] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022] Open
Abstract
When cardiac tissue is exposed to hypoxia, myocytes are damaged, while fibroblasts are activated. However, it is unknown what changes are induced by hypoxia in cardiac fibroblasts. In this study, using the whole cell patch-clamp technique, we investigated the effect of hypoxia on membrane currents in fibroblasts primarily cultured from adult rat hearts. Cardiac fibroblasts were incubated for 24 h under normoxic or hypoxic conditions using Anaeropack. Hypoxia increased a current which reversed at around -20 mV in the cardiac fibroblasts. This current was inhibited by clotrimazole, which is an inhibitor of transient receptor potential melastatin 2 (TRPM2) channel and intermediate-conductance Ca(2+)-activated K(+) channel (KCa3.1). ADP ribose in the pipette solution enhanced this current. Quantitative RT-PCR revealed that mRNA of TRPM2, but not that of KCa3.1, was increased by hypoxia. RNA interference of TRPM2 prevented the development of the hypoxia-induced current. H(2)O(2), an activator of TRPM2 channel, induced a higher [Ca(2+)](i) elevation in hypoxia-exposed cardiac fibroblasts than that in normoxia-exposed cells. We conclude that hypoxia induces TRPM2 channel expression in adult rat cardiac fibroblasts.
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Affiliation(s)
- Kenji Takahashi
- Department of Pharmacology, Fukushima Medical University, School of Medicine, Japan.
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44
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McDowell KS, Arevalo HJ, Maleckar MM, Trayanova NA. Susceptibility to arrhythmia in the infarcted heart depends on myofibroblast density. Biophys J 2011; 101:1307-15. [PMID: 21943411 DOI: 10.1016/j.bpj.2011.08.009] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 07/22/2011] [Accepted: 08/03/2011] [Indexed: 10/17/2022] Open
Abstract
Fibroblasts are electrophysiologically quiescent in the healthy heart. Evidence suggests that remodeling following myocardial infarction may include coupling of myofibroblasts (Mfbs) among themselves and with myocytes via gap junctions. We use a magnetic resonance imaging-based, three-dimensional computational model of the chronically infarcted rabbit ventricles to characterize the arrhythmogenic substrate resulting from Mfb infiltration as a function of Mfb density. Mfbs forming gap junctions were incorporated into both infarct regions, the periinfarct zone (PZ) and the scar; six scenarios were modeled: 0%, 10%, and 30% Mfbs in the PZ, with either 80% or 0% Mfbs in the scar. Ionic current remodeling in PZ was also included. All preparations exhibited elevated resting membrane potential within and near the PZ and action potential duration shortening throughout the ventricles. The unique combination of PZ ionic current remodeling and different degrees of Mfb infiltration in the infarcted ventricles determines susceptibility to arrhythmia. At low densities, Mfbs do not alter arrhythmia propensity; the latter arises predominantly from ionic current remodeling in PZ. At intermediate densities, Mfbs cause additional action potential shortening and exacerbate arrhythmia propensity. At high densities, Mfbs protect against arrhythmia by causing resting depolarization and blocking propagation, thus overcoming the arrhythmogenic effects of PZ ionic current remodeling.
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Affiliation(s)
- Kathleen S McDowell
- The Johns Hopkins University, Department of Biomedical Engineering and Institute for Computational Medicine, Baltimore, Maryland, USA
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45
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Abstract
The cytoarchitecture of the working myocardium is characterized by densely packed cardiomyocytes that are embedded in a three-dimensional network of numerous fibroblasts. Although the importance of cardiac fibroblasts in maintaining an orderly structured extracellular matrix is well recognized, less is known about their potential paracrine and electrotonic interactions with cardiomyocytes. This is partly the result of the complex intermingling of both cell types in vivo that tends to preclude a direct investigation of heterocellular crosstalk. It is for that reason that most of our present knowledge regarding stromal-parenchymal cell interactions is based on culture systems that permit direct access to either cell type. An often disregarded feature of such studies is that cardiac fibroblasts in standard two-dimensional cell culture have a pronounced tendency to undergo a phenotype switch to myofibroblasts. This cell type typically appears in injured hearts where it contributes importantly to fibrotic remodeling. The present review focuses on recent insights into electrical and paracrine crosstalk between myofibroblasts and cardiomyocytes while acknowledging that a comprehensive understanding of stromal-parenchymal cell interactions will depend on future methodological developments that permit retaining the fibroblast phenotype in cell culture systems and that will, most importantly, allow direct investigations of heterocellular crosstalk in intact tissue.
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The cardiac fibroblast: functional and electrophysiological considerations in healthy and diseased hearts. J Cardiovasc Pharmacol 2011; 57:380-8. [PMID: 21242811 DOI: 10.1097/fjc.0b013e31820cda19] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Cardiac fibrosis occurs in a number of cardiovascular diseases associated with a high incidence of arrhythmias. A critical event in the development of fibrosis is the transformation of fibroblasts into an active phenotype or myofibroblast. This transformation results in functional changes including increased proliferation and changes in the release of signaling molecules and extracellular matrix deposition. Traditionally, fibroblasts have been considered to affect cardiac electrophysiology indirectly by physically isolating myocytes and creating conduction barriers. There is now increasing evidence that cardiac fibroblasts may play a direct role in modulating the electrophysiological substrate in diseased hearts. The purpose of this review is to summarize the functional changes associated with fibroblast activation, the membrane currents that have been identified in adult cardiac fibroblasts, and describe recent studies of fibroblast-myocyte electrical interactions with emphasis on the changes that occur with cardiac injury. Further analysis of fibroblast membrane electrophysiology and their interactions with myocytes will lead to a more complete understanding of the arrhythmic substrate. These studies have the potential to generate new therapeutic approaches for the prevention of arrhythmias associated with cardiac fibrosis.
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Zlochiver S. Subthreshold parameters of cardiac tissue in a bi-layer computer model of heart failure. ACTA ACUST UNITED AC 2011; 10:190-200. [PMID: 21082251 DOI: 10.1007/s10558-010-9104-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Current density threshold and liminal area are subthreshold parameters of the cardiac tissue that indicate its susceptibility to external and internal stimulations. Extensive experimental and theoretical research has been conducted to quantify these two parameters in normal conditions for both animal and human models. Here we employed a 2D numerical model of human cardiac tissue to assess these subthreshold parameters under the pathological conditions of heart failure and fibrosis. Stimuli were applied over an area ranging from 0.04 to 1 mm² using various pulse durations. The current density threshold decreased with increasing stimulation area or pulse duration. No significant changes were found in both parameters between control conditions and heart failure in the atrial tissue, while in the ventricular tissue, heart failure resulted in significantly reduced excitability with higher stimulation current magnitudes needed for excitation and larger liminal areas. This results from the specific ionic remodeling in ventricular heart failure that affects both subthreshold active currents such as I(K₁) and connexin 43 conductance. In fibrosis, increased fibroblast to myocyte coupling coefficient had a non-linear influence on current density thresholds, with an initial increase of current magnitude followed by a relaxation phase down to the current magnitude threshold for the control condition with no fibrosis. The results show that subthreshold excitation properties of the myocardium are influenced in a complex, non-linear manner by cardiac pathologies. Such observations may contribute to our understanding of impulse capturing properties, relevant, for example, for the generation of ectopic foci-originated arrhythmias and for the efficient design of cardiac stimulating electrodes.
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Affiliation(s)
- Sharon Zlochiver
- Department of Biomedical Engineering, Faculty of Engineering, Tel-Aviv University, 69978 Ramat-Aviv, Tel-Aviv, Israel.
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Yue L, Xie J, Nattel S. Molecular determinants of cardiac fibroblast electrical function and therapeutic implications for atrial fibrillation. Cardiovasc Res 2010; 89:744-53. [PMID: 20962103 DOI: 10.1093/cvr/cvq329] [Citation(s) in RCA: 273] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Cardiac fibroblasts account for about 75% of all cardiac cells, but because of their small size contribute only ∼10-15% of total cardiac cell volume. They play a crucial role in cardiac pathophysiology. For a long time, it has been recognized that fibroblasts and related cell types are the principal sources of extracellular matrix (ECM) proteins, which organize cardiac cellular architecture. In disease states, fibroblast production of increased quantities of ECM proteins leads to tissue fibrosis, which can impair both mechanical and electrical function of the heart, contributing to heart failure and arrhythmogenesis. Atrial fibrosis is known to play a particularly important role in atrial fibrillation (AF). This review article focuses on recent advances in understanding the molecular electrophysiology of cardiac fibroblasts. Cardiac fibroblasts express a variety of ion channels, in particular voltage-gated K(+) channels and non-selective cation channels of the transient receptor potential (TRP) family. Both K(+) and TRP channels are important determinants of fibroblast function, with TRP channels acting as Ca(2+)-entry pathways that stimulate fibroblast differentiation into secretory myofibroblast phenotypes producing ECM proteins. Fibroblasts can couple to cardiomyocytes and substantially affect their cellular electrical properties, including conduction, resting potential, repolarization, and excitability. Co-cultured preparations of cardiomyocytes and fibroblasts generate arrhythmias by a variety of mechanisms, including spontaneous impulse formation and rotor-driven reentry. In addition, the excess ECM proteins produced by fibroblasts can interrupt cardiomyocyte-bundle continuity, leading to local conduction disturbances and reentrant arrhythmias. A better understanding of the electrical properties of fibroblasts should lead to an improved comprehension of AF pathophysiology and a variety of novel targets for antiarrhythmic intervention.
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Affiliation(s)
- Lixia Yue
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, USA
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49
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Maleckar MM, Greenstein JL, Giles WR, Trayanova NA. Electrotonic coupling between human atrial myocytes and fibroblasts alters myocyte excitability and repolarization. Biophys J 2010; 97:2179-90. [PMID: 19843450 DOI: 10.1016/j.bpj.2009.07.054] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2008] [Revised: 07/22/2009] [Accepted: 07/31/2009] [Indexed: 12/31/2022] Open
Abstract
Atrial fibrosis has been implicated in the development and maintenance of atrial arrhythmias, and is characterized by expansion of the extracellular matrix and an increased number of fibroblasts (Fbs). Electrotonic coupling between atrial myocytes and Fbs may contribute to the formation of an arrhythmogenic substrate. However, the role of these cell-cell interactions in the function of both normal and diseased atria remains poorly understood. The goal of this study was to gain mechanistic insight into the role of electrotonic Fb-myocyte coupling on myocyte excitability and repolarization. To represent the system, a human atrial myocyte (hAM) coupled to a variable number of Fbs, we employed a new ionic model of the hAM, and a variety of membrane representations for atrial Fbs. Simulations elucidated the effects of altering the intercellular coupling conductance, electrophysiological Fb properties, and stimulation rate on the myocyte action potential. The results demonstrate that the myocyte resting potential and action potential waveform are modulated strongly by the properties and number of coupled Fbs, the degree of coupling, and the pacing frequency. Our model provides mechanistic insight into the consequences of heterologous cell coupling on hAM electrophysiology, and can be extended to evaluate these implications at both tissue and organ levels.
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Affiliation(s)
- Mary M Maleckar
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, USA
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50
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Abstract
The permanent cellular constituents of the heart include cardiac fibroblasts, myocytes, endothelial cells, and vascular smooth muscle cells. Previous studies have demonstrated that there are undulating changes in cardiac cell populations during embryonic development, through neonatal development and into the adult. Transient cell populations include lymphocytes, mast cells, and macrophages, which can interact with these permanent cell types to affect cardiac function. It has also been observed that there are marked differences in the makeup of the cardiac cell populations depending on the species, which may be important when examining myocardial remodeling. Current dogma states that the fibroblast makes up the largest cell population of the heart; however, this appears to vary for different species, especially mice. Cardiac fibroblasts play a critical role in maintaining normal cardiac function, as well as in cardiac remodeling during pathological conditions such as myocardial infarct and hypertension. These cells have numerous functions, including synthesis and deposition of extracellular matrix, cell-cell communication with myocytes, cell-cell signaling with other fibroblasts, as well as with endothelial cells. These contacts affect the electrophysiological properties, secretion of growth factors and cytokines, as well as potentiating blood vessel formation. Although a plethora of information is known about several of these processes, relatively little is understood about fibroblasts and their role in angiogenesis during development or cardiac remodeling. In this review, we provide insight into the various properties of cardiac fibroblasts that helps illustrate their importance in maintaining proper cardiac function, as well as their critical role in the remodeling heart.
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Affiliation(s)
- Colby A. Souders
- Texas A&M Health Science Center College of Medicine, Division of Molecular Cardiology, Temple, TX 76504
| | - Stephanie L.K. Bowers
- Texas A&M Health Science Center College of Medicine, Division of Molecular Cardiology, Temple, TX 76504
| | - Troy A. Baudino
- Texas A&M Health Science Center College of Medicine, Division of Molecular Cardiology, Temple, TX 76504
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