1
|
Wang M, Mo D, Zhang N, Yu H. Ferroptosis in diabetic cardiomyopathy: Advances in cardiac fibroblast-cardiomyocyte interactions. Heliyon 2024; 10:e35219. [PMID: 39165946 PMCID: PMC11334834 DOI: 10.1016/j.heliyon.2024.e35219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 06/19/2024] [Accepted: 07/24/2024] [Indexed: 08/22/2024] Open
Abstract
Diabetic cardiomyopathy (DCM) is a common complication of diabetes, and its pathogenesis remains elusive. Ferroptosis, a process dependent on iron-mediated cell death, plays a crucial role in DCM via disrupted iron metabolism, lipid peroxidation, and weakened antioxidant defenses. Hyperglycemia, oxidative stress, and inflammation may exacerbate ferroptosis in diabetes. This review emphasizes the interaction between cardiac fibroblasts and cardiomyocytes in DCM, influencing ferroptosis occurrence. By exploring ferroptosis modulation for potential therapeutic targets, this article offers a fresh perspective on DCM treatment. The study systematically covers the interplay, mechanisms, and targeted drugs linked to ferroptosis in DCM development.
Collapse
Affiliation(s)
| | | | - Ning Zhang
- Department of Cardiology, The Affiliated Hospital of Qingdao University, Qingdao, 266000, Shandong, China
| | - Haichu Yu
- Department of Cardiology, The Affiliated Hospital of Qingdao University, Qingdao, 266000, Shandong, China
| |
Collapse
|
2
|
Han Y, Xiong C, Zhang LZ, Wang YD, Yang G, Guo Z. Antagonism of N/OFQ attenuates externalization of β1-adrenergic receptor and ventricular arrhythmias in acute myocardial ischemia rat model. Eur J Pharmacol 2022; 929:175139. [PMID: 35809655 DOI: 10.1016/j.ejphar.2022.175139] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 07/02/2022] [Accepted: 07/02/2022] [Indexed: 11/18/2022]
Abstract
Nociceptin/orphanin FQ (N/OFQ) and adrenergic activations play roles in promoting cardiac arrhythmia in acute myocardial ischemia but whether N/OFQ and β1-adrenergic activities interact and how they interact in the arrhythmogenesis are still unknown. We designed this study to investigate the potential interaction of N/OFQ and β1-adrenergic activities and the underlying mechanism in arrhythmogenesis in acute myocardial ischemia. Ventricular arrhythmia was evaluated in anaesthetized rats following permanent coronary artery occlusion (CAO), in presence and absence of UFP-101 (a selective antagonist of N/OFQ receptor). The changes of β1-adrenergic receptor (β1-AR) in plasma membrane of cardiomyocytes were quantitatively evaluated and the relations with the alterations of phosphorylated Raf kinase inhibitor protein (p-RKIP) and phosphorylated connexin 43 (p-Cx43) were investigated. The ventricular arrhythmia was 59% less in the animals pre-treated with UFP-101 than the placebo-treated control (difference of means = -2.41; 95% confidence interval (CI) -2.84 to -1.99; P < 0.001). Meanwhile, p-RKIP and membrane β1-AR in the myocardium were downregulated by 59% and 24%, respectively (p-RKIP: difference of means = -6.91; 95% CI -8.38 to -5.45; P < 0.001; membrane β1-AR difference of means = -27.06; 95% CI -29.89 to -24.23; P < 0.001). Artificial upregulation of RKIP by didymin significant increased β1-AR in plasma membrane of the cardiomyocytes in the animals prone to ventricular arrhythmia. The findings may suggest that activation of N/OFQ receptor in acute myocardial ischemia induces upregulation of p-RKIP, externalization of β1-adrenergic receptor and downregulation of p-Cx43 in the cardiomyocytes, which promotes ventricular arrhythmia.
Collapse
Affiliation(s)
- Yi Han
- College of Anaesthesia, Shanxi Medical University, 86 Xinjiannan Road, Taiyuan, 030001, Shanxi, China; Department of Anaesthesia, Second Hospital of Shanxi Medical University, 382 Wuyi Road, Taiyuan, 030001, Shanxi, China
| | - Chang Xiong
- College of Anaesthesia, Shanxi Medical University, 86 Xinjiannan Road, Taiyuan, 030001, Shanxi, China
| | - Lin-Zhong Zhang
- College of Anaesthesia, Shanxi Medical University, 86 Xinjiannan Road, Taiyuan, 030001, Shanxi, China; Department of Anaesthesia, Second Hospital of Shanxi Medical University, 382 Wuyi Road, Taiyuan, 030001, Shanxi, China
| | - Yi-Di Wang
- College of Anaesthesia, Shanxi Medical University, 86 Xinjiannan Road, Taiyuan, 030001, Shanxi, China
| | - Guang Yang
- College of Anaesthesia, Shanxi Medical University, 86 Xinjiannan Road, Taiyuan, 030001, Shanxi, China
| | - Zheng Guo
- College of Anaesthesia, Shanxi Medical University, 86 Xinjiannan Road, Taiyuan, 030001, Shanxi, China; Department of Anaesthesia, Second Hospital of Shanxi Medical University, 382 Wuyi Road, Taiyuan, 030001, Shanxi, China; Key Laboratory of Cellular Physiology (Shanxi Medical University), National Education Commission, Shanxi Medical University, 86 Xinjiannan Road, Taiyuan, 030001, Shanxi, China.
| |
Collapse
|
3
|
Nayir S, Lacour SP, Kucera JP. Active force generation contributes to the complexity of spontaneous activity and to the response to stretch of murine cardiomyocyte cultures. J Physiol 2022; 600:3287-3312. [PMID: 35679256 PMCID: PMC9541716 DOI: 10.1113/jp283083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 06/01/2022] [Indexed: 11/17/2022] Open
Abstract
Abstract Cardiomyocyte cultures exhibit spontaneous electrical and contractile activity, as in a natural cardiac pacemaker. In such preparations, beat rate variability exhibits features similar to those of heart rate variability in vivo. Mechanical deformations and forces feed back on the electrical properties of cardiomyocytes, but it is not fully elucidated how this mechano‐electrical interplay affects beating variability in such preparations. Using stretchable microelectrode arrays, we assessed the effects of the myosin inhibitor blebbistatin and the non‐selective stretch‐activated channel blocker streptomycin on beating variability and on the response of neonatal or fetal murine ventricular cell cultures against deformation. Spontaneous electrical activity was recorded without stretch and upon predefined deformation protocols (5% uniaxial and 2% equibiaxial strain, applied repeatedly for 1 min every 3 min). Without stretch, spontaneous activity originated from the edge of the preparations, and its site of origin switched frequently in a complex manner across the cultures. Blebbistatin did not change mean beat rate, but it decreased the spatial complexity of spontaneous activity. In contrast, streptomycin did not exert any manifest effects. During the deformation protocols, beat rate increased transiently upon stretch but, paradoxically, also upon release. Blebbistatin attenuated the response to stretch, whereas this response was not affected by streptomycin. Therefore, our data support the notion that in a spontaneously firing network of cardiomyocytes, active force generation, rather than stretch‐activated channels, is involved mechanistically in the complexity of the spatiotemporal patterns of spontaneous activity and in the stretch‐induced acceleration of beating.
![]() Key points Monolayer cultures of cardiac cells exhibit spontaneous electrical and contractile activity, as in a natural cardiac pacemaker. Beating variability in these preparations recapitulates the power‐law behaviour of heart rate variability in vivo. However, the effects of mechano‐electrical feedback on beating variability are not yet fully understood. Using stretchable microelectrode arrays, we examined the effects of the contraction uncoupler blebbistatin and the non‐specific stretch‐activated channel blocker streptomycin on beating variability and on stretch‐induced changes of beat rate. Without stretch, blebbistatin decreased the spatial complexity of beating variability, whereas streptomycin had no effects. Both stretch and release increased beat rate transiently; blebbistatin attenuated the increase of beat rate upon stretch, whereas streptomycin had no effects. Active force generation contributes to the complexity of spatiotemporal patterns of beating variability and to the increase of beat rate upon mechanical deformation. Our study contributes to the understanding of how mechano‐electrical feedback influences heart rate variability.
Collapse
Affiliation(s)
- Seyma Nayir
- Department of Physiology, University of Bern, Bern, Switzerland
| | | | - Jan P Kucera
- Department of Physiology, University of Bern, Bern, Switzerland
| |
Collapse
|
4
|
Kléber AG, Jin Q. Coupling between cardiac cells-An important determinant of electrical impulse propagation and arrhythmogenesis. ACTA ACUST UNITED AC 2021; 2:031301. [PMID: 34296210 DOI: 10.1063/5.0050192] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 06/09/2021] [Indexed: 01/30/2023]
Abstract
Cardiac arrhythmias are an important cause of sudden cardiac death-a devastating manifestation of many underlying causes, such as heart failure and ischemic heart disease leading to ventricular tachyarrhythmias and ventricular fibrillation, and atrial fibrillation causing cerebral embolism. Cardiac electrical propagation is a main factor in the initiation and maintenance of cardiac arrhythmias. In the heart, gap junctions are the basic unit at the cellular level that host intercellular low-resistance channels for the diffusion of ions and small regulatory molecules. The dual voltage clamp technique enabled the direct measurement of electrical conductance between cells and recording of single gap junction channel openings. The rapid turnover of gap junction channels at the intercalated disk implicates a highly dynamic process of trafficking and internalization of gap junction connexons. Recently, non-canonical roles of gap junction proteins have been discovered in mitochondria function, cytoskeletal organization, trafficking, and cardiac rescue. At the tissue level, we explain the concepts of linear propagation and safety factor based on the model of linear cellular structure. Working myocardium is adequately represented as a discontinuous cellular network characterized by cellular anisotropy and connective tissue heterogeneity. Electrical propagation in discontinuous cellular networks reflects an interplay of three main factors: cell-to-cell electrical coupling, flow of electrical charge through the ion channels, and the microscopic tissue structure. This review provides a state-of-the-art update of the cardiac gap junction channels and their role in cardiac electrical impulse propagation and highlights a combined approach of genetics, cell biology, and physics in modern cardiac electrophysiology.
Collapse
Affiliation(s)
- André G Kléber
- Department of Pathology, Harvard Medical School, Boston, Massachusetts 02215, USA
| | - Qianru Jin
- Disease Biophysics Group, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, Massachusetts 02134, USA
| |
Collapse
|
5
|
Valiunas V, Cohen IS, Brink PR, Clausen C. A study of the outward background current conductance g K1, the pacemaker current conductance g f, and the gap junction conductance g j as determinants of biological pacing in single cells and in a two-cell syncytium using the dynamic clamp. Pflugers Arch 2020; 472:561-570. [PMID: 32415460 DOI: 10.1007/s00424-020-02378-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 03/31/2020] [Accepted: 04/02/2020] [Indexed: 12/21/2022]
Abstract
We previously demonstrated that a two-cell syncytium, composed of a ventricular myocyte and an mHCN2 expressing cell, recapitulated most properties of in vivo biological pacing induced by mHCN2-transfected hMSCs in the canine ventricle. Here, we use the two-cell syncytium, employing dynamic clamp, to study the roles of gf (pacemaker conductance), gK1 (background K+ conductance), and gj (intercellular coupling conductance) in biological pacing. We studied gf and gK1 in single HEK293 cells expressing cardiac sodium current channel Nav1.5 (SCN5A). At fixed gf, increasing gK1 hyperpolarized the cell and initiated pacing. As gK1 increased, rate increased, then decreased, finally ceasing at membrane potentials near EK. At fixed gK1, increasing gf depolarized the cell and initiated pacing. With increasing gf, rate increased reaching a plateau, then decreased, ceasing at a depolarized membrane potential. We studied gj via virtual coupling with two non-adjacent cells, a driver (HEK293 cell) in which gK1 and gf were injected without SCN5A and a follower (HEK293 cell), expressing SCN5A. At the chosen values of gK1 and gf oscillations initiated in the driver, when gj was increased synchronized pacing began, which then decreased by about 35% as gj approached 20 nS. Virtual uncoupling yielded similar insights into gj. We also studied subthreshold oscillations in physically and virtually coupled cells. When coupling was insufficient to induce pacing, passive spread of the oscillations occurred in the follower. These results show a non-monotonic relationship between gK1, gf, gj, and pacing. Further, oscillations can be generated by gK1 and gf in the absence of SCN5A.
Collapse
Affiliation(s)
- Virginijus Valiunas
- Department of Physiology and Biophysics and the Institute for Molecular Cardiology, Stony Brook University, Stony Brook, NY, 11794-8661, USA.
| | - Ira S Cohen
- Department of Physiology and Biophysics and the Institute for Molecular Cardiology, Stony Brook University, Stony Brook, NY, 11794-8661, USA
| | - Peter R Brink
- Department of Physiology and Biophysics and the Institute for Molecular Cardiology, Stony Brook University, Stony Brook, NY, 11794-8661, USA
| | - Chris Clausen
- Department of Physiology and Biophysics and the Institute for Molecular Cardiology, Stony Brook University, Stony Brook, NY, 11794-8661, USA
| |
Collapse
|
6
|
Li J, Zhang L, Yu L, Minami I, Miyagawa S, Hörning M, Dong J, Qiao J, Qu X, Hua Y, Fujimoto N, Shiba Y, Zhao Y, Tang F, Chen Y, Sawa Y, Tang C, Liu L. Circulating re-entrant waves promote maturation of hiPSC-derived cardiomyocytes in self-organized tissue ring. Commun Biol 2020; 3:122. [PMID: 32170165 PMCID: PMC7070090 DOI: 10.1038/s42003-020-0853-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 02/19/2020] [Indexed: 02/07/2023] Open
Abstract
Directed differentiation methods allow acquisition of high-purity cardiomyocytes differentiated from human induced pluripotent stem cells (hiPSCs); however, their immaturity characteristic limits their application for drug screening and regenerative therapy. The rapid electrical pacing of cardiomyocytes has been used for efficiently promoting the maturation of cardiomyocytes, here we describe a simple device in modified culture plate on which hiPSC-derived cardiomyocytes can form three-dimensional self-organized tissue rings (SOTRs). Using calcium imaging, we show that within the ring, reentrant waves (ReWs) of action potential spontaneously originated and ran robustly at a frequency up to 4 Hz. After 2 weeks, SOTRs with ReWs show higher maturation including structural organization, increased cardiac-specific gene expression, enhanced Ca2+-handling properties, an increased oxygen-consumption rate, and enhanced contractile force. We subsequently use a mathematical model to interpret the origination, propagation, and long-term behavior of the ReWs within the SOTRs.
Collapse
Affiliation(s)
- Junjun Li
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Lu Zhang
- Center for Quantitative Biology and Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, 100871, Beijing, China
| | - Leqian Yu
- Institutes for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Ushinomiya-cho, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Itsunari Minami
- Department of Cell Design for Tissue Construction Faculty of Medicine, Osaka University, Osaka, 565-0871, Japan
| | - Shigeru Miyagawa
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Marcel Hörning
- Institutes for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Ushinomiya-cho, Sakyo-ku, Kyoto, 606-8501, Japan
- Institute of Biomaterials and Biomolecular Systems, University of Stuttgart, 70569, Stuttgart, Germany
| | - Ji Dong
- Biomedical Pioneering Innovation Center, College of Life Sciences, Peking University, 100871, Beijing, China
| | - Jing Qiao
- Institutes for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Ushinomiya-cho, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Xiang Qu
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Ying Hua
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Nanae Fujimoto
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Yuji Shiba
- Department of Regenerative Science and Medicine, Institute for Biomedical Sciences, Shinshu University, 3-1-1 Asahi, Matsumoto, Nagano, 390-0821, Japan
| | - Yang Zhao
- State Key Laboratory of Natural and Biomimetic Drugs, The MOE Key Laboratory of Cell Proliferation and Differentiation, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Peking University, 100871, Beijing, China
| | - Fuchou Tang
- Biomedical Pioneering Innovation Center, College of Life Sciences, Peking University, 100871, Beijing, China
| | - Yong Chen
- Institutes for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Ushinomiya-cho, Sakyo-ku, Kyoto, 606-8501, Japan
- PASTEUR, Département de chimie, école normale supérieure, PSL Research University, Sorbonne Universités, UPMC Université Paris 06, CNRS, Paris, 75005, France
| | - Yoshiki Sawa
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan.
| | - Chao Tang
- Center for Quantitative Biology and Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, 100871, Beijing, China.
| | - Li Liu
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan.
- Department of Drug Discovery Cardiovascular Regeneration, Osaka University Graduate School of Medicine, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
| |
Collapse
|
7
|
Wei N, Tolkacheva EG. Interplay between ephaptic coupling and complex geometry of border zone during acute myocardial ischemia: Effect on arrhythmogeneity. CHAOS (WOODBURY, N.Y.) 2020; 30:033111. [PMID: 32237767 DOI: 10.1063/1.5134447] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 02/12/2020] [Indexed: 06/11/2023]
Abstract
Acute myocardial ischemia is an imbalance between myocardial blood supply and demand, which is caused by the cessation of blood flow within the heart resulting from an obstruction in one of the major coronary arteries. A severe blockage may result in a region of nonperfused tissue known as ischemic core (IC). As a result, a border zone (BZ) between perfused and nonperfused regions is created due to differences in blood and oxygen supplies. Recent experimental findings reveal a complex "finger-like" geometry in BZ; however, its effect on arrhythmogenicity is not clear. Ephaptic coupling, which relies on the intercalated disk between cell ends, has been suggested to play an active role in mediating intercellular electrical communication when gap junctions are impaired. In this paper, we explored the interplay between ephaptic coupling and the geometry of BZ on action potential propagation across the ischemic region. Our study shows that ephaptic coupling can greatly suppress the occurrence of a conduction block, which points to its beneficial effect. The beneficial effect of ephaptic coupling is more evident in BZ with the "finger-like" geometry. In addition, the complex geometry of BZ, i.e., more frequent, deeper, and wider "fingers," promotes the conduction through the ischemic region. In contrast, the larger size of IC impedes the cardiac conduction across the ischemic region. Our results also show that ephaptic coupling promotes the impact of the complex geometry of BZ on signal propagation; however, it inhibits the impact of IC size.
Collapse
Affiliation(s)
- Ning Wei
- Department of Mathematics, Purdue University, West Lafayette, Indiana 47907, USA
| | - Elena G Tolkacheva
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
| |
Collapse
|
8
|
Zhang L, Li J, Liu L, Tang C. Analysis of Circulating Waves in Tissue Rings derived from Human Induced Pluripotent Stem Cells. Sci Rep 2020; 10:2984. [PMID: 32076031 PMCID: PMC7031392 DOI: 10.1038/s41598-020-59803-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2019] [Accepted: 12/16/2019] [Indexed: 12/26/2022] Open
Abstract
Developing more mature cardiomyocytes derived from human induced pluripotent stem cells is essential for cell transplantation and drug screening. In a previous study, we described a platform on which cardiomyocytes derived from human induced pluripotent stem cells (hiPSC-CMs) formed three-dimensional self-organized tissue rings. Within these rings, traveling waves of action potentials spontaneously originate and propagate for a long time. In order to understand the dynamic behavior of these waves, we developed a mathematical model for the circulation of the electrical signal in such rings. By using the restitution curves of the action potential and the conduction velocity we demonstrated the mechanisms underlying the steady circulation and the features dependent on velocity. The analytic result agreed well with the experimental data in the origination, propagation, and long-term behavior of traveling waves within self-organized tissue rings. The theoretical analysis of traveling waves may also provide a reference to the analysis of reentrant rhythms in hearts.
Collapse
Affiliation(s)
- Lu Zhang
- Center for Quantitative Biology, Peking University, Beijing, 100871, China
| | - Junjun Li
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Li Liu
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan.
| | - Chao Tang
- Center for Quantitative Biology, Peking University, Beijing, 100871, China.
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China.
- School of Physics, Peking University, Beijing, 100871, China.
| |
Collapse
|
9
|
Jæger KH, Edwards AG, McCulloch A, Tveito A. Properties of cardiac conduction in a cell-based computational model. PLoS Comput Biol 2019; 15:e1007042. [PMID: 31150383 PMCID: PMC6561587 DOI: 10.1371/journal.pcbi.1007042] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2018] [Revised: 06/12/2019] [Accepted: 04/23/2019] [Indexed: 11/18/2022] Open
Abstract
The conduction of electrical signals through cardiac tissue is essential for maintaining the function of the heart, and conduction abnormalities are known to potentially lead to life-threatening arrhythmias. The properties of cardiac conduction have therefore been the topic of intense study for decades, but a number of questions related to the mechanisms of conduction still remain unresolved. In this paper, we demonstrate how the so-called EMI model may be used to study some of these open questions. In the EMI model, the extracellular space, the cell membrane, the intracellular space and the cell connections are all represented as separate parts of the computational domain, and the model therefore allows for study of local properties that are hard to represent in the classical homogenized bidomain or monodomain models commonly used to study cardiac conduction. We conclude that a non-uniform sodium channel distribution increases the conduction velocity and decreases the time delays over gap junctions of reduced coupling in the EMI model simulations. We also present a theoretical optimal cell length with respect to conduction velocity and consider the possibility of ephaptic coupling (i.e. cell-to-cell coupling through the extracellular potential) acting as an alternative or supporting mechanism to gap junction coupling. We conclude that for a non-uniform distribution of sodium channels and a sufficiently small intercellular distance, ephaptic coupling can influence the dynamics of the sodium channels and potentially provide cell-to-cell coupling when the gap junction connection is absent. The electrochemical wave traversing the heart during every beat is essential for cardiac pumping function and supply of blood to the body. Understanding the stability of this wave is crucial to understanding how lethal arrhythmias are generated. Despite this importance, our knowledge of the physical determinants of wave propagation are still evolving. One particular challenge has been the lack of accurate mathematical models of conduction at the cellular level. Because cardiac muscle is an electrical syncytium, in which direct charge transfer between cells drives wave propagation, classical bidomain and monodomain tissue models employ a homogenized approximation of this process. This approximation is not valid at the length scale of single cells, and prevents any analysis of how cellular structures impact cardiac conduction. Instead, so-called microdomain models must be used for these questions. Here we utilize a recently developed modelling framework that is well suited to represent small collections of cells. By applying this framework, we show that concentration of sodium channels at the longitudinal borders of myocytes accelerates cardiac conduction. We also demonstrate that when juxtaposed cells are sufficiently close, this non-uniform distribution induces large ephaptic currents, which contribute to intercellular coupling.
Collapse
Affiliation(s)
| | | | - Andrew McCulloch
- Department of Bioengineering, University of California, San Diego, California, United States of America
| | - Aslak Tveito
- Simula Research Laboratory, Oslo, Norway
- * E-mail:
| |
Collapse
|
10
|
Savoji H, Mohammadi MH, Rafatian N, Toroghi MK, Wang EY, Zhao Y, Korolj A, Ahadian S, Radisic M. Cardiovascular disease models: A game changing paradigm in drug discovery and screening. Biomaterials 2019; 198:3-26. [PMID: 30343824 PMCID: PMC6397087 DOI: 10.1016/j.biomaterials.2018.09.036] [Citation(s) in RCA: 121] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 09/11/2018] [Accepted: 09/22/2018] [Indexed: 02/06/2023]
Abstract
Cardiovascular disease is the leading cause of death worldwide. Although investment in drug discovery and development has been sky-rocketing, the number of approved drugs has been declining. Cardiovascular toxicity due to therapeutic drug use claims the highest incidence and severity of adverse drug reactions in late-stage clinical development. Therefore, to address this issue, new, additional, replacement and combinatorial approaches are needed to fill the gap in effective drug discovery and screening. The motivation for developing accurate, predictive models is twofold: first, to study and discover new treatments for cardiac pathologies which are leading in worldwide morbidity and mortality rates; and second, to screen for adverse drug reactions on the heart, a primary risk in drug development. In addition to in vivo animal models, in vitro and in silico models have been recently proposed to mimic the physiological conditions of heart and vasculature. Here, we describe current in vitro, in vivo, and in silico platforms for modelling healthy and pathological cardiac tissues and their advantages and disadvantages for drug screening and discovery applications. We review the pathophysiology and the underlying pathways of different cardiac diseases, as well as the new tools being developed to facilitate their study. We finally suggest a roadmap for employing these non-animal platforms in assessing drug cardiotoxicity and safety.
Collapse
Affiliation(s)
- Houman Savoji
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 170 College St, Toronto, Ontario, M5S 3G9, Canada; Toronto General Research Institute, University Health Network, University of Toronto, 200 Elizabeth St, Toronto, Ontario, M5G 2C4, Canada
| | - Mohammad Hossein Mohammadi
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 170 College St, Toronto, Ontario, M5S 3G9, Canada; Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College St, Toronto, Ontario, M5S 3E5, Canada; Toronto General Research Institute, University Health Network, University of Toronto, 200 Elizabeth St, Toronto, Ontario, M5G 2C4, Canada
| | - Naimeh Rafatian
- Toronto General Research Institute, University Health Network, University of Toronto, 200 Elizabeth St, Toronto, Ontario, M5G 2C4, Canada
| | - Masood Khaksar Toroghi
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College St, Toronto, Ontario, M5S 3E5, Canada
| | - Erika Yan Wang
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 170 College St, Toronto, Ontario, M5S 3G9, Canada
| | - Yimu Zhao
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 170 College St, Toronto, Ontario, M5S 3G9, Canada; Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College St, Toronto, Ontario, M5S 3E5, Canada
| | - Anastasia Korolj
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 170 College St, Toronto, Ontario, M5S 3G9, Canada; Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College St, Toronto, Ontario, M5S 3E5, Canada
| | - Samad Ahadian
- Toronto General Research Institute, University Health Network, University of Toronto, 200 Elizabeth St, Toronto, Ontario, M5G 2C4, Canada
| | - Milica Radisic
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 170 College St, Toronto, Ontario, M5S 3G9, Canada; Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College St, Toronto, Ontario, M5S 3E5, Canada; Toronto General Research Institute, University Health Network, University of Toronto, 200 Elizabeth St, Toronto, Ontario, M5G 2C4, Canada.
| |
Collapse
|
11
|
Carmeliet E. Conduction in cardiac tissue. Historical reflections. Physiol Rep 2019; 7:e13860. [PMID: 30604919 PMCID: PMC6316167 DOI: 10.14814/phy2.13860] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 08/22/2018] [Indexed: 11/24/2022] Open
Abstract
Two hypotheses have been proposed to explain propagation of the action potential in heart. According to the gap junction hypothesis local short-circuit currents pass from the proximal depolarized cell to the distal inactive cell via gap junctions and are responsible for the depolarization of the distal cell. In the ephapse hypothesis the depolarization of the proximal cell generates an electrical field in the narrow cleft between cells resulting in depolarization beyond threshold of the distal cell. Measurements of length constant, free diffusion of 42 K, local currents between cells, existence of high-conductance gap junctions led to the conclusion that heart muscle is a functional syncytium. Propagation of the action potential, however, is not uniform but anisotropic and discontinuous; it can be also unidirectional. These findings are strong arguments in favor of the gap junction thesis. They do not exclude, as predicted by theoretical calculations, that in conditions of an abnormal fall in gap junction conductance ephaptic conduction takes over. In this last case, definitive experimental confirmation is still required. See also: https://doi.org/10.14814/phy2.13861 & https://doi.org/10.14814/phy2.13862.
Collapse
|
12
|
Radwański PB, Johnson CN, Györke S, Veeraraghavan R. Cardiac Arrhythmias as Manifestations of Nanopathies: An Emerging View. Front Physiol 2018; 9:1228. [PMID: 30233404 PMCID: PMC6131669 DOI: 10.3389/fphys.2018.01228] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 08/14/2018] [Indexed: 12/21/2022] Open
Abstract
A nanodomain is a collection of proteins localized within a specialized, nanoscale structural environment, which can serve as the functional unit of macroscopic physiologic processes. We are beginning to recognize the key roles of cardiomyocyte nanodomains in essential processes of cardiac physiology such as electrical impulse propagation and excitation–contraction coupling (ECC). There is growing appreciation of nanodomain dysfunction, i.e., nanopathy, as a mechanistic driver of life-threatening arrhythmias in a variety of pathologies. Here, we offer an overview of current research on the role of nanodomains in cardiac physiology with particular emphasis on: (1) sodium channel-rich nanodomains within the intercalated disk that participate in cell-to-cell electrical coupling and (2) dyadic nanodomains located along transverse tubules that participate in ECC. The beat to beat function of cardiomyocytes involves three phases: the action potential, the calcium transient, and mechanical contraction/relaxation. In all these phases, cell-wide function results from the aggregation of the stochastic function of individual proteins. While it has long been known that proteins that exist in close proximity influence each other’s function, it is increasingly appreciated that there exist nanoscale structures that act as functional units of cardiac biophysical phenomena. Termed nanodomains, these structures are collections of proteins, localized within specialized nanoscale structural environments. The nano-environments enable the generation of localized electrical and/or chemical gradients, thereby conferring unique functional properties to these units. Thus, the function of a nanodomain is determined by its protein constituents as well as their local structural environment, adding an additional layer of complexity to cardiac biology and biophysics. However, with the emergence of experimental techniques that allow direct investigation of structure and function at the nanoscale, our understanding of cardiac physiology and pathophysiology at these scales is rapidly advancing. Here, we will discuss the structure and functions of multiple cardiomyocyte nanodomains, and novel strategies that target them for the treatment of cardiac arrhythmias.
Collapse
Affiliation(s)
- Przemysław B Radwański
- Bob and Corinne Frick Center for Heart Failure and Arrhythmia, The Ohio State University Wexner Medical Center, Columbus, OH, United States.,Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, United States.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, United States.,Division of Pharmacy Practice and Science, College of Pharmacy, The Ohio State University, Columbus, OH, United States
| | - Christopher N Johnson
- Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, United States.,Vanderbilt Center for Arrhythmia Research and Therapeutics, Nashville, TN, United States
| | - Sándor Györke
- Bob and Corinne Frick Center for Heart Failure and Arrhythmia, The Ohio State University Wexner Medical Center, Columbus, OH, United States.,Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, United States.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Rengasayee Veeraraghavan
- Bob and Corinne Frick Center for Heart Failure and Arrhythmia, The Ohio State University Wexner Medical Center, Columbus, OH, United States.,Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH, United States.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, United States.,Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States
| |
Collapse
|
13
|
Buccarello A, Azzarito M, Michoud F, Lacour SP, Kucera JP. Uniaxial strain of cultured mouse and rat cardiomyocyte strands slows conduction more when its axis is parallel to impulse propagation than when it is perpendicular. Acta Physiol (Oxf) 2018; 223:e13026. [PMID: 29282897 DOI: 10.1111/apha.13026] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 12/14/2017] [Accepted: 12/21/2017] [Indexed: 11/28/2022]
Abstract
AIM Cardiac tissue deformation can modify tissue resistance, membrane capacitance and ion currents and hence cause arrhythmogenic slow conduction. Our aim was to investigate whether uniaxial strain causes different changes in conduction velocity (θ) when the principal strain axis is parallel vs perpendicular to impulse propagation. METHODS Cardiomyocyte strands were cultured on stretchable custom microelectrode arrays, and θ was determined during steady-state pacing. Uniaxial strain (5%) with principal axis parallel (orthodromic) or perpendicular (paradromic) to propagation was applied for 1 minute and controlled by imaging a grid of markers. The results were analysed in terms of cable theory. RESULTS Both types of strain induced immediate changes of θ upon application and release. In material coordinates, orthodromic strain decreased θ significantly more (P < .001) than paradromic strain (2.2 ± 0.5% vs 1.0 ± 0.2% in n = 8 mouse cardiomyocyte cultures, 2.3 ± 0.4% vs 0.9 ± 0.5% in n = 4 rat cardiomyocyte cultures, respectively). The larger effect of orthodromic strain can be explained by the increase in axial myoplasmic resistance, which is not altered by paradromic strain. Thus, changes in tissue resistance substantially contributed to the changes of θ during strain, in addition to other influences (eg stretch-activated channels). Besides these immediate effects, the application of strain also consistently initiated a slow progressive decrease in θ and a slow recovery of θ upon release. CONCLUSION Changes in cardiac conduction velocity caused by acute stretch do not only depend on the magnitude of strain but also on its orientation relative to impulse propagation. This dependence is due to different effects on tissue resistance.
Collapse
Affiliation(s)
- A. Buccarello
- Department of Physiology; University of Bern; Bern Switzerland
| | - M. Azzarito
- Department of Physiology; University of Bern; Bern Switzerland
| | - F. Michoud
- Bertarelli Foundation Chair in Neuroprosthetic Technology; Laboratory for Soft Bioelectronic Interfaces; Institute of Microengineering; Institute of Bioengineering; Centre for Neuroprosthetics; École Polytechnique Fédérale de Lausanne (EPFL); Geneva Switzerland
| | - S. P. Lacour
- Bertarelli Foundation Chair in Neuroprosthetic Technology; Laboratory for Soft Bioelectronic Interfaces; Institute of Microengineering; Institute of Bioengineering; Centre for Neuroprosthetics; École Polytechnique Fédérale de Lausanne (EPFL); Geneva Switzerland
| | - J. P. Kucera
- Department of Physiology; University of Bern; Bern Switzerland
| |
Collapse
|
14
|
Hichri E, Abriel H, Kucera JP. Distribution of cardiac sodium channels in clusters potentiates ephaptic interactions in the intercalated disc. J Physiol 2018; 596:563-589. [PMID: 29210458 DOI: 10.1113/jp275351] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 11/20/2017] [Indexed: 01/18/2023] Open
Abstract
KEY POINTS It has been proposed that ephaptic conduction, relying on interactions between the sodium (Na+ ) current and the extracellular potential in intercalated discs, might contribute to cardiac conduction when gap junctional coupling is reduced, but this mechanism is still controversial. In intercalated discs, Na+ channels form clusters near gap junction plaques, but the functional significance of these clusters has never been evaluated. In HEK cells expressing cardiac Na+ channels, we show that restricting the extracellular space modulates the Na+ current, as predicted by corresponding simulations accounting for ephaptic effects. In a high-resolution model of the intercalated disc, clusters of Na+ channels that face each other across the intercellular cleft facilitate ephaptic impulse transmission when gap junctional coupling is reduced. Thus, our simulations reveal a functional role for the clustering of Na+ channels in intercalated discs, and suggest that rearrangement of these clusters in disease may influence cardiac conduction. ABSTRACT It has been proposed that ephaptic interactions in intercalated discs, mediated by extracellular potentials, contribute to cardiac impulse propagation when gap junctional coupling is reduced. However, experiments demonstrating ephaptic effects on the cardiac Na+ current (INa ) are scarce. Furthermore, Na+ channels form clusters around gap junction plaques, but the electrophysiological significance of these clusters has never been investigated. In patch clamp experiments with HEK cells stably expressing human Nav 1.5 channels, we examined how restricting the extracellular space modulates INa elicited by an activation protocol. In parallel, we developed a high-resolution computer model of the intercalated disc to investigate how the distribution of Na+ channels influences ephaptic interactions. Approaching the HEK cells to a non-conducting obstacle always increased peak INa at step potentials near the threshold of INa activation and decreased peak INa at step potentials far above threshold (7 cells, P = 0.0156, Wilcoxon signed rank test). These effects were consistent with corresponding control simulations with a uniform Na+ channel distribution. In the intercalated disc computer model, redistributing the Na+ channels into a central cluster of the disc potentiated ephaptic effects. Moreover, ephaptic impulse transmission from one cell to another was facilitated by clusters of Na+ channels facing each other across the intercellular cleft when gap junctional coupling was reduced. In conclusion, our proof-of-principle experiments demonstrate that confining the extracellular space modulates cardiac INa , and our simulations reveal the functional role of the aggregation of Na+ channels in the perinexus. These findings highlight novel concepts in the physiology of cardiac excitation.
Collapse
Affiliation(s)
- Echrak Hichri
- Department of Physiology, University of Bern, Bern, Switzerland
| | - Hugues Abriel
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Jan P Kucera
- Department of Physiology, University of Bern, Bern, Switzerland
| |
Collapse
|
15
|
Kucera JP, Rohr S, Kleber AG. Microstructure, Cell-to-Cell Coupling, and Ion Currents as Determinants of Electrical Propagation and Arrhythmogenesis. Circ Arrhythm Electrophysiol 2017; 10:CIRCEP.117.004665. [DOI: 10.1161/circep.117.004665] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 07/17/2017] [Indexed: 11/16/2022]
Affiliation(s)
- Jan P. Kucera
- From the Department of Physiology, University of Bern, Switzerland (J.P.K., S.R.); and the Department of Pathology, Harvard Medical School, Boston, MA (A.G.K.)
| | - Stephan Rohr
- From the Department of Physiology, University of Bern, Switzerland (J.P.K., S.R.); and the Department of Pathology, Harvard Medical School, Boston, MA (A.G.K.)
| | - Andre G. Kleber
- From the Department of Physiology, University of Bern, Switzerland (J.P.K., S.R.); and the Department of Pathology, Harvard Medical School, Boston, MA (A.G.K.)
| |
Collapse
|
16
|
Weinberg SH. Ephaptic coupling rescues conduction failure in weakly coupled cardiac tissue with voltage-gated gap junctions. CHAOS (WOODBURY, N.Y.) 2017; 27:093908. [PMID: 28964133 DOI: 10.1063/1.4999602] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Electrical conduction in cardiac tissue is usually considered to be primarily facilitated by gap junctions, providing a pathway between the intracellular spaces of neighboring cells. However, recent studies have highlighted the role of coupling via extracellular electric fields, also known as ephaptic coupling, particularly in the setting of reduced gap junction expression. Further, in the setting of reduced gap junctional coupling, voltage-dependent gating of gap junctions, an oft-neglected biophysical property in computational studies, produces a positive feedback that promotes conduction failure. We hypothesized that ephaptic coupling can break the positive feedback loop and rescue conduction failure in weakly coupled cardiac tissue. In a computational tissue model incorporating voltage-gated gap junctions and ephaptic coupling, we demonstrate that ephaptic coupling can rescue conduction failure in weakly coupled tissue. Further, ephaptic coupling increased conduction velocity in weakly coupled tissue, and importantly, reduced the minimum gap junctional coupling necessary for conduction, most prominently at fast pacing rates. Finally, we find that, although neglecting gap junction voltage-gating results in negligible differences in well coupled tissue, more significant differences occur in weakly coupled tissue, greatly underestimating the minimal gap junctional coupling that can maintain conduction. Our study suggests that ephaptic coupling plays a conduction-preserving role, particularly at rapid heart rates.
Collapse
Affiliation(s)
- S H Weinberg
- Virginia Commonwealth University, 401 West Main Street, Richmond, Virginia 23284, USA
| |
Collapse
|
17
|
Tse G, Liu T, Li G, Keung W, Yeo JM, Fiona Chan YW, Yan BP, Chan YS, Wong SH, Li RA, Zhao J, Wu WKK, Wong WT. Effects of pharmacological gap junction and sodium channel blockade on S1S2 restitution properties in Langendorff-perfused mouse hearts. Oncotarget 2017; 8:85341-85352. [PMID: 29156723 PMCID: PMC5689613 DOI: 10.18632/oncotarget.19675] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 05/23/2017] [Indexed: 12/19/2022] Open
Abstract
Gap junctions and sodium channels are the major molecular determinants of normal and abnormal electrical conduction through the myocardium, however, their exact contributions to arrhythmogenesis are unclear. We examined conduction and recovery properties of regular (S1) and extrasystolic (S2) action potentials (APs), S1S2 restitution and ventricular arrhythmogenicity using the gap junction and sodium channel inhibitor heptanol (2 mM) in Langendorff-perfused mouse hearts (n=10). Monophasic action potential recordings obtained during S1S2 pacing showed that heptanol increased the proportion of hearts showing inducible ventricular tachycardia (0/10 vs. 5/8 hearts (Fisher’s exact test, P < 0.05), prolonged activation latencies of S1 and S2 APs, thereby decreasing S2/S1 activation latency ratio (ANOVA, P < 0.05) despite prolonged ventricular effective refractory period (VERP). It did not alter S1 action potential duration at 90% repolarization (APD90) but prolonged S2 APD90 (P < 0.05), thereby increasing S2/S1 APD90 ratio (P < 0.05). It did not alter maximum conduction velocity (CV) restitution gradient or maximum CV reductions but decreased the restitution time constant (P < 0.05). It increased maximal APD90 restitution gradient (P < 0.05) without altering critical diastolic interval or maximum APD90 reductions. Pro-arrhythmic effects of 2 mM heptanol are explicable by delayed conduction and abnormal electrical restitution. We concluded that gap junctions modulated via heptanol (0.05 mM) increased arrhythmogenicity through a delay in conduction, while sodium channel inhibition by a higher concentration of heptanol (2 mM) increased arrhythmogenicity via additional mechanisms, such as abnormalities in APDs and CV restitution.
Collapse
Affiliation(s)
- Gary Tse
- Department of Medicine and Therapeutics, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China.,Li Ka Shing Institute of Health Sciences, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China
| | - Tong Liu
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin, China
| | - Guangping Li
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin, China
| | - Wendy Keung
- Dr. Li Dak-Sum Research Centre, The University of Hong Kong-Karolinska Institutet Collaboration in Regenerative Medicine, Hong Kong, China
| | - Jie Ming Yeo
- Faculty of Medicine, Imperial College London, London, UK
| | | | - Bryan P Yan
- Department of Medicine and Therapeutics, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China
| | - Yat Sun Chan
- Department of Medicine and Therapeutics, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China
| | - Sunny Hei Wong
- Department of Medicine and Therapeutics, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China.,Li Ka Shing Institute of Health Sciences, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, China
| | - Ronald A Li
- Ming Wai Lau Centre for Reparative Medicine, Karolinska Institutet, Solna, Sweden
| | - Jichao Zhao
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - William K K Wu
- Department of Anaesthesia and Intensive Care, State Key Laboratory of Digestive Disease, LKS Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Wing Tak Wong
- School of Life Sciences, Chinese University of Hong Kong, Hong Kong, China
| |
Collapse
|
18
|
Caddeo S, Boffito M, Sartori S. Tissue Engineering Approaches in the Design of Healthy and Pathological In Vitro Tissue Models. Front Bioeng Biotechnol 2017; 5:40. [PMID: 28798911 PMCID: PMC5526851 DOI: 10.3389/fbioe.2017.00040] [Citation(s) in RCA: 144] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 06/26/2017] [Indexed: 12/16/2022] Open
Abstract
In the tissue engineering (TE) paradigm, engineering and life sciences tools are combined to develop bioartificial substitutes for organs and tissues, which can in turn be applied in regenerative medicine, pharmaceutical, diagnostic, and basic research to elucidate fundamental aspects of cell functions in vivo or to identify mechanisms involved in aging processes and disease onset and progression. The complex three-dimensional (3D) microenvironment in which cells are organized in vivo allows the interaction between different cell types and between cells and the extracellular matrix, the composition of which varies as a function of the tissue, the degree of maturation, and health conditions. In this context, 3D in vitro models can more realistically reproduce a tissue or organ than two-dimensional (2D) models. Moreover, they can overcome the limitations of animal models and reduce the need for in vivo tests, according to the "3Rs" guiding principles for a more ethical research. The design of 3D engineered tissue models is currently in its development stage, showing high potential in overcoming the limitations of already available models. However, many issues are still opened, concerning the identification of the optimal scaffold-forming materials, cell source and biofabrication technology, and the best cell culture conditions (biochemical and physical cues) to finely replicate the native tissue and the surrounding environment. In the near future, 3D tissue-engineered models are expected to become useful tools in the preliminary testing and screening of drugs and therapies and in the investigation of the molecular mechanisms underpinning disease onset and progression. In this review, the application of TE principles to the design of in vitro 3D models will be surveyed, with a focus on the strengths and weaknesses of this emerging approach. In addition, a brief overview on the development of in vitro models of healthy and pathological bone, heart, pancreas, and liver will be presented.
Collapse
Affiliation(s)
- Silvia Caddeo
- Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
- Department of Oral Cell Biology, Academic Center for Dentistry Amsterdam, Amsterdam, Netherlands
| | - Monica Boffito
- Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| | - Susanna Sartori
- Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| |
Collapse
|
19
|
Trease AJ, Capuccino JMV, Contreras J, Harris AL, Sorgen PL. Intramolecular signaling in a cardiac connexin: Role of cytoplasmic domain dimerization. J Mol Cell Cardiol 2017; 111:69-80. [PMID: 28754342 DOI: 10.1016/j.yjmcc.2017.07.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 06/06/2017] [Accepted: 07/24/2017] [Indexed: 10/19/2022]
Abstract
Gap junctions, composed of connexins, mediate electrical coupling and impulse propagation in the working myocardium. In the human heart, the spatio-temporal regulation and distinct functional properties of the three dominant connexins (Cx43, Cx45, and Cx40) suggests non-redundant physiological roles for each isoform. There are substantial differences in gating properties, expression, and trafficking among these isoforms, however, little is known about the determinants of these different phenotypes. To gain insight regarding these determinants, we focused on the carboxyl-terminal (CT) domain because of its importance in channel regulation and large degree of sequence divergence among connexin family members. Using in vitro biophysical experiments, we identified a structural feature unique to Cx45: high affinity (KD~100nM) dimerization between CT domains. In this study, we sought to determine if this dimerization occurs in cells and to identify the biological significance of the dimerization. Using a bimolecular fluorescence complementation assay, we demonstrate that the CT domains dimerize at the plasma membrane. By inhibiting CT dimerization with a mutant construct, we show that CT dimerization is necessary for proper Cx45 membrane localization, turnover, phosphorylation status, and binding to protein partners. Furthermore, CT dimerization is needed for normal intercellular communication and hemichannel activity. Altogether, our results demonstrate that CT dimerization is a structural feature important for correct Cx45 function. This study is significant because discovery of how interactions mediated by the CT domains can be modulated would open the door to strategies to ameliorate the pathological effects of altered connexin regulation in the failing heart.
Collapse
Affiliation(s)
- Andrew J Trease
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Juan M V Capuccino
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, USA
| | - Jorge Contreras
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, USA
| | - Andrew L Harris
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, USA
| | - Paul L Sorgen
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA.
| |
Collapse
|
20
|
Tan Y, Richards D, Coyle RC, Yao J, Xu R, Gou W, Wang H, Menick DR, Tian B, Mei Y. Cell number per spheroid and electrical conductivity of nanowires influence the function of silicon nanowired human cardiac spheroids. Acta Biomater 2017; 51:495-504. [PMID: 28087483 PMCID: PMC5346043 DOI: 10.1016/j.actbio.2017.01.029] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 01/04/2017] [Accepted: 01/09/2017] [Indexed: 12/29/2022]
Abstract
Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) provide an unlimited cell source to treat cardiovascular diseases, the leading cause of death worldwide. However, current hiPSC-CMs retain an immature phenotype that leads to difficulties for integration with adult myocardium after transplantation. To address this, we recently utilized electrically conductive silicon nanowires (e-SiNWs) to facilitate self-assembly of hiPSC-CMs to form nanowired hiPSC cardiac spheroids. Our previous results showed addition of e-SiNWs effectively enhanced the functions of the cardiac spheroids and improved the cellular maturation of hiPSC-CMs. Here, we examined two important factors that can affect functions of the nanowired hiPSC cardiac spheroids: (1) cell number per spheroid (i.e., size of the spheroids), and (2) the electrical conductivity of the e-SiNWs. To examine the first factor, we prepared hiPSC cardiac spheroids with four different sizes by varying cell number per spheroid (∼0.5k, ∼1k, ∼3k, ∼7k cells/spheroid). Spheroids with ∼3k cells/spheroid was found to maximize the beneficial effects of the 3D spheroid microenvironment. This result was explained with a semi-quantitative theory that considers two competing factors: 1) the improved 3D cell-cell adhesion, and 2) the reduced oxygen supply to the center of spheroids with the increase of cell number. Also, the critical role of electrical conductivity of silicon nanowires has been confirmed in improving tissue function of hiPSC cardiac spheroids. These results lay down a solid foundation to develop suitable nanowired hiPSC cardiac spheroids as an innovative cell delivery system to treat cardiovascular diseases. STATEMENT OF SIGNIFICANCE Cardiovascular disease is the leading cause of death and disability worldwide. Due to the limited regenerative capacity of adult human hearts, human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have received significant attention because they provide a patient specific cell source to regenerate damaged hearts. Despite the progress, current human hiPSC-CMs retain an immature phenotype that leads to difficulties for integration with adult myocardium after transplantation. To address this, we recently utilized electrically conductive silicon nanowires (e-SiNWs) to facilitate self-assembly of hiPSC-CMs to form nanowired hiPSC cardiac spheroids. Our previous results showed addition of e-SiNWs effectively enhanced the functions of the cardiac spheroids and improved the cellular maturation of hiPSC-CMs. In this manuscript, we examined the effects of two important factors on the functions of nanowired hiPSC cardiac spheroids: (1) cell number per spheroid (i.e., size of the spheroids), and (2) the electrical conductivity of the e-SiNWs. The results from these studies will allow for the development of suitable nanowired hiPSC cardiac spheroids to effectively deliver hiPSC-CMs for heart repair.
Collapse
Affiliation(s)
- Yu Tan
- Bioengineering Department, Clemson University, Clemson, SC 29634, USA
| | - Dylan Richards
- Bioengineering Department, Clemson University, Clemson, SC 29634, USA
| | - Robert C Coyle
- Bioengineering Department, Clemson University, Clemson, SC 29634, USA
| | - Jenny Yao
- Academic Magnet High School, North Charleston, SC 29405, USA
| | - Ruoyu Xu
- Department of Chemistry, The James Franck Institute and the Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA
| | - Wenyu Gou
- Department of Surgery, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Hongjun Wang
- Department of Surgery, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Donald R Menick
- Division of Cardiology, Department of Medicine, Gazes Cardiac Research Institute, Ralph H. Johnson Veterans Affairs Medical Center, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Bozhi Tian
- Department of Chemistry, The James Franck Institute and the Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA
| | - Ying Mei
- Bioengineering Department, Clemson University, Clemson, SC 29634, USA; Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
| |
Collapse
|
21
|
Desplantez T. Cardiac Cx43, Cx40 and Cx45 co-assembling: involvement of connexins epitopes in formation of hemichannels and Gap junction channels. BMC Cell Biol 2017; 18:3. [PMID: 28124623 PMCID: PMC5267329 DOI: 10.1186/s12860-016-0118-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Background This review comes after the International Gap Junction Conference (IGJC 2015) and describes the current knowledge on the function of the specific motifs of connexins in the regulation of the formation of gap junction channels. Moreover the review is complemented by a summarized description of the distinct contribution of gap junction channels in the electrical coupling. Results Complementary biochemical and functional characterization on cell models and primary cells have improved our understanding on the oligomerization of connexins and the formation and the electrical properties of gap junction channels. Studies mostly focused cardiac connexins Cx43 and Cx40 expressed in myocytes, while Cx45 and Cx30.2 have been less investigated, for which main findings are reviewed to highlight their critical contribution in the formation of gap junction channels for ensuring the orchestrated electrical impulse propagation and coordination of atrial and ventricular contraction and heart function, whereas connexin dysfunction and remodeling are pro-arrhythmic factors. Common and specific motifs of residues identified in different domain of each type of connexin determine the connexin homo- and hetero-oligomerization and the channels formation, which leads to specific electrical properties. Conclusions These motifs and the resulting formation of gap junction channels are keys to ensure the tissue homeostasis and function in each connexin expression pattern in various tissues of multicellular organisms. Altogether, the findings to date have significantly improved our understanding on the function of the different connexin expression patterns in healthy and diseased tissues, and promise further investigations on the contribution in the different types of connexin.
Collapse
Affiliation(s)
- Thomas Desplantez
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, Campus X. Arnozan, Avenue Haut Leveque, 33600, Pessac- Bordeaux, France. .,Univ. Bordeaux, Centre de recherche Cardio-Thoracique de Bordeaux, U1045, F-33000, Bordeaux, France. .,INSERM, Centre de recherche Cardio-Thoracique de Bordeaux, U1045, F-33000, Bordeaux, France.
| |
Collapse
|
22
|
Abstract
Cardiac arrhythmias can follow disruption of the normal cellular electrophysiological processes underlying excitable activity and their tissue propagation as coherent wavefronts from the primary sinoatrial node pacemaker, through the atria, conducting structures and ventricular myocardium. These physiological events are driven by interacting, voltage-dependent, processes of activation, inactivation, and recovery in the ion channels present in cardiomyocyte membranes. Generation and conduction of these events are further modulated by intracellular Ca2+ homeostasis, and metabolic and structural change. This review describes experimental studies on murine models for known clinical arrhythmic conditions in which these mechanisms were modified by genetic, physiological, or pharmacological manipulation. These exemplars yielded molecular, physiological, and structural phenotypes often directly translatable to their corresponding clinical conditions, which could be investigated at the molecular, cellular, tissue, organ, and whole animal levels. Arrhythmogenesis could be explored during normal pacing activity, regular stimulation, following imposed extra-stimuli, or during progressively incremented steady pacing frequencies. Arrhythmic substrate was identified with temporal and spatial functional heterogeneities predisposing to reentrant excitation phenomena. These could arise from abnormalities in cardiac pacing function, tissue electrical connectivity, and cellular excitation and recovery. Triggering events during or following recovery from action potential excitation could thereby lead to sustained arrhythmia. These surface membrane processes were modified by alterations in cellular Ca2+ homeostasis and energetics, as well as cellular and tissue structural change. Study of murine systems thus offers major insights into both our understanding of normal cardiac activity and its propagation, and their relationship to mechanisms generating clinical arrhythmias.
Collapse
Affiliation(s)
- Christopher L-H Huang
- Physiological Laboratory and the Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| |
Collapse
|
23
|
Tse G, Yeo JM, Tse V, Kwan J, Sun B. Gap junction inhibition by heptanol increases ventricular arrhythmogenicity by reducing conduction velocity without affecting repolarization properties or myocardial refractoriness in Langendorff-perfused mouse hearts. Mol Med Rep 2016; 14:4069-4074. [PMID: 27633494 PMCID: PMC5101880 DOI: 10.3892/mmr.2016.5738] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 07/18/2016] [Indexed: 12/31/2022] Open
Abstract
In the current study, arrhythmogenic effects of the gap junction inhibitor heptanol (0.05 mM) were examined in Langendorff-perfused mouse hearts. Monophasic action potential recordings were obtained from the left ventricular epicardium during right ventricular pacing. Regular activity was observed both prior and subsequent to application of heptanol in all of the 12 hearts studied during 8 Hz pacing. By contrast, induced ventricular tachycardia (VT) was observed after heptanol treatment in 6/12 hearts using a S1S2 protocol (Fisher's exact test; P<0.05). The arrhythmogenic effects of heptanol were associated with increased activation latencies from 13.2±0.6 to 19.4±1.3 msec (analysis of variance; P<0.001) and reduced conduction velocities (CVs) from 0.23±0.01 to 0.16±0.01 msec (analysis of variance; P<0.001) in an absence of alterations in action potential durations (ADPs) at x=90% (38.0±1.0 vs. 38.3±1.8 msec), 70% (16.8±1.0 vs. 19.5±0.9 msec), 50% (9.2±0.8 vs. 10.1±0.6 msec) or 30% (4.8±0.5 vs. 6.3±0.6 msec) repolarization (APDx) or in effective refractory period (ERPs) (39.6±1.9 vs. 40.6±3.0 msec) (all P>0.05). Consequently, excitation wavelengths (λ; CV x ERP) were reduced from 9.1±0.6 to 6.5±0.6 mm (P<0.01), however critical intervals for re‑excitation (APD90 ‑ ERP) were unaltered (‑1.1±2.4 vs. ‑2.3±1.8 msec; P>0.05). Together, these observations demonstrate for the first time, to the best of our knowledge, that inhibition of gap junctions alone using a low heptanol concentration (0.05 mM) was able to reduce CV, which alone was sufficient to permit the induction of VT using premature stimulation by reducing λ, which therefore appears central in the determination of arrhythmic tendency.
Collapse
Affiliation(s)
- Gary Tse
- Department of Medicine and Therapeutics, Chinese University of Hong Kong, Hong Kong, P.R. China
| | - Jie Ming Yeo
- Faculty of Medicine, Imperial College London, London SW7 2AZ, UK
| | - Vivian Tse
- Department of Physiology, McGill University, Montreal, QC H3G 1Y6, Canada
| | - Joseph Kwan
- Department of Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
| | - Bing Sun
- Department of Cardiology, Tongji University Affiliated Tongji Hospital, Shanghai 200065, P.R. China
| |
Collapse
|
24
|
Nishii K, Seki A, Kumai M, Morimoto S, Miwa T, Hagiwara N, Shibata Y, Kobayashi Y. Connexin45 contributes to global cardiovascular development by establishing myocardial impulse propagation. Mech Dev 2016; 140:41-52. [DOI: 10.1016/j.mod.2016.02.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 02/19/2016] [Accepted: 02/20/2016] [Indexed: 11/15/2022]
|
25
|
Wei N, Mori Y, Tolkacheva EG. The dual effect of ephaptic coupling on cardiac conduction with heterogeneous expression of connexin 43. J Theor Biol 2016; 397:103-14. [PMID: 26968493 DOI: 10.1016/j.jtbi.2016.02.029] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 01/25/2016] [Accepted: 02/19/2016] [Indexed: 11/30/2022]
Abstract
Decreased and heterogeneous expression of connexin 43 (Cx43) are common features in animal heart failure models. Ephpatic coupling, which relies on the presence of junctional cleft space between the ends of adjacent cells, has been suggested to play a more active role in mediating intercellular electrical communication when gap junctions are reduced. To better understand the interplay of Cx43 expression and ephaptic coupling on cardiac conduction during heart failure, we performed numerical simulations on our model when Cx43 expression is reduced and heterogeneous. Under severely reduced Cx43 expression, we identified three new phenomena in the presence of ephaptic coupling: alternating conduction, in which ephaptic and gap junction-mediated mechanisms alternate; instability of planar fronts; and small amplitude action potential (SAP), which has a smaller potential amplitude than the normal action potential. In the presence of heterogeneous Cx43 expression, ephaptic coupling can either prevent or promote conduction block (CB) depending on the Cx43 knockout (Cx43KO) content. When Cx43KO content is relatively high, ephaptic coupling reduces the probabilities of CB. However, ephaptic coupling promotes CB when Cx43KO and wild type cells are mixed in roughly equal proportion, which can be attributed to an increase in current-to-load mismatch.
Collapse
Affiliation(s)
- Ning Wei
- School of Mathematics, University of Minnesota, 206 Church St. SE, Minneapolis, MN 55455, United States
| | - Yoichiro Mori
- School of Mathematics, University of Minnesota, 206 Church St. SE, Minneapolis, MN 55455, United States
| | - Elena G Tolkacheva
- Department of Biomedical Engineering, University of Minnesota, 312 Church St. SE, 6-128 Nils Hasselmo Hall, Minneapolis, MN 55455, United States.
| |
Collapse
|
26
|
Tse G, Yeo JM. Conduction abnormalities and ventricular arrhythmogenesis: The roles of sodium channels and gap junctions. IJC HEART & VASCULATURE 2015; 9:75-82. [PMID: 26839915 PMCID: PMC4695916 DOI: 10.1016/j.ijcha.2015.10.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 10/19/2015] [Indexed: 01/12/2023]
Abstract
Ventricular arrhythmias arise from disruptions in the normal orderly sequence of electrical activation and recovery of the heart. They can be categorized into disorders affecting predominantly cellular depolarization or repolarization, or those involving action potential (AP) conduction. This article briefly discusses the factors causing conduction abnormalities in the form of unidirectional conduction block and reduced conduction velocity (CV). It then examines the roles that sodium channels and gap junctions play in AP conduction. Finally, it synthesizes experimental results to illustrate molecular mechanisms of how abnormalities in these proteins contribute to such conduction abnormalities and hence ventricular arrhythmogenesis, in acquired pathologies such as acute ischaemia and heart failure, as well as inherited arrhythmic syndromes.
Collapse
Affiliation(s)
- Gary Tse
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
| | - Jie Ming Yeo
- School of Medicine, Imperial College London, SW7 2AZ, UK
| |
Collapse
|
27
|
Relating specific connexin co-expression ratio to connexon composition and gap junction function. J Mol Cell Cardiol 2015; 89:195-202. [PMID: 26550940 DOI: 10.1016/j.yjmcc.2015.11.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 10/05/2015] [Accepted: 11/04/2015] [Indexed: 12/15/2022]
Abstract
Cardiac connexin 43 (Cx43), Cx40 and Cx45 are co-expressed at distinct ratios in myocytes. This pattern is considered a key factor in regulating the gap junction channels composition, properties and function and remains poorly understood. This work aims to correlate gap junction function with the connexin composition of the channels at accurate ratios Cx43:Cx40 and Cx43:Cx45. Rat liver epithelial cells that endogenously express Cx43 were stably transfected to induce expression of accurate levels of Cx40 or Cx45 that may be present in various areas of the heart (e.g. atria and ventricular conduction system). Induction of Cx40 does not increase the amounts of junctional connexins (Cx43 and Cx40), whereas induction of Cx45 increases the amounts of junctional connexins (Cx43 and Cx45). Interestingly, the non-junctional fraction of Cx43 remains unaffected upon induction of Cx40 and Cx45. Co-immunoprecipitation studies show low level of Cx40/Cx43 heteromerisation and undetectable Cx45/Cx43 heteromerisation. Functional characterisation shows that induction of Cx40 and Cx45 decreases Lucifer Yellow transfer. Electrical coupling is decreased by Cx45 induction, whereas it is decreased at low induction of Cx40 and increased at high induction. These data indicate a fine regulation of the gap junction channel make-up in function of the type and the ratio of co-expressed Cxs that specifically regulates chemical and electrical coupling. This reflects specific gap junction function in regulating impulse propagation in the healthy heart, and a pro-arrhythmic potential of connexin remodelling in the diseased heart.
Collapse
|
28
|
Kucera JP, Prudat Y, Marcu IC, Azzarito M, Ullrich ND. Slow conduction in mixed cultured strands of primary ventricular cells and stem cell-derived cardiomyocytes. Front Cell Dev Biol 2015; 3:58. [PMID: 26442264 PMCID: PMC4585316 DOI: 10.3389/fcell.2015.00058] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 09/09/2015] [Indexed: 11/30/2022] Open
Abstract
Modern concepts for the treatment of myocardial diseases focus on novel cell therapeutic strategies involving stem cell-derived cardiomyocytes (SCMs). However, functional integration of SCMs requires similar electrophysiological properties as primary cardiomyocytes (PCMs) and the ability to establish intercellular connections with host myocytes in order to contribute to the electrical and mechanical activity of the heart. The aim of this project was to investigate the properties of cardiac conduction in a co-culture approach using SCMs and PCMs in cultured cell strands. Murine embryonic SCMs were pooled with fetal ventricular cells and seeded in predefined proportions on microelectrode arrays to form patterned strands of mixed cells. Conduction velocity (CV) was measured during steady state pacing. SCM excitability was estimated from action potentials measured in single cells using the patch clamp technique. Experiments were complemented with computer simulations of conduction using a detailed model of cellular architecture in mixed cell strands. CV was significantly lower in strands composed purely of SCMs (5.5 ± 1.5 cm/s, n = 11) as compared to PCMs (34.9 ± 2.9 cm/s, n = 21) at similar refractoriness (100% SCMs: 122 ± 25 ms, n = 9; 100% PCMs: 139 ± 67 ms, n = 14). In mixed strands combining both cell types, CV was higher than in pure SCMs strands, but always lower than in 100% PCM strands. Computer simulations demonstrated that both intercellular coupling and electrical excitability limit CV. These data provide evidence that in cultures of murine ventricular cardiomyocytes, SCMs cannot restore CV to control levels resulting in slow conduction, which may lead to reentry circuits and arrhythmias.
Collapse
Affiliation(s)
- Jan P Kucera
- Department of Physiology, University of Bern Bern, Switzerland
| | - Yann Prudat
- Department of Physiology, University of Bern Bern, Switzerland
| | - Irene C Marcu
- Department of Physiology, University of Bern Bern, Switzerland ; Department of Physiology and Pathophysiology, Heidelberg University Heidelberg, Germany
| | | | - Nina D Ullrich
- Department of Physiology and Pathophysiology, Heidelberg University Heidelberg, Germany
| |
Collapse
|
29
|
Pidoux G, Taskén K. Anchored PKA as a gatekeeper for gap junctions. Commun Integr Biol 2015; 8:e1057361. [PMID: 26478781 PMCID: PMC4594474 DOI: 10.1080/19420889.2015.1057361] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 05/26/2015] [Accepted: 05/27/2015] [Indexed: 12/24/2022] Open
Abstract
Anchored protein kinase A (PKA) bound to A Kinase Anchoring Protein (AKAP) mediates effects of localized increases in cAMP in defined subcellular microdomains and retains the specificity in cAMP-PKA signaling to distinct extracellular stimuli. Gap junctions are pores between adjacent cells constituted by connexin proteins that provide means of communication and transfer of small molecules. While the PKA signaling is known to promote human trophoblast cell fusion, the gap junction communication through connexin 43 (Cx43) is a prerequisite for this process. We recently demonstrated that trophoblast fusion is regulated by ezrin, a known AKAP, which binds to Cx43 and delivers PKA in the vicinity gap junctions. We found that disruption of the ezrin-Cx43 interaction abolished PKA-dependent phosphorylation of Cx43 as well as gap junction communication and subsequently cell fusion. We propose that the PKA-ezrin-Cx43 macromolecular complex regulating gap junction communication constitutes a general mechanism to control opening of Cx43 gap junctions by phosphorylation in response to cAMP signaling in various cell types.
Collapse
Affiliation(s)
- Guillaume Pidoux
- INSERM; UMR-S-1139 ; Paris, France ; Université Paris Descartes ; Paris, France
| | - Kjetil Taskén
- Centre for Molecular Medicine Norway; Nordic EMBL Partnership; University of Oslo and Oslo University Hospital ; Oslo, Norway ; Biotechnology Center; University of Oslo ; Oslo, Norway ; K.G. Jebsen Inflammation Research Center; University of Oslo ; Oslo, Norway ; K.G. Jebsen Center for Cancer Immunotherapy; University of Oslo ; Oslo, Norway ; Department of Infectious Diseases; Oslo University Hospital ; Oslo, Norway
| |
Collapse
|
30
|
Meens MJ, Kwak BR, Duffy HS. Role of connexins and pannexins in cardiovascular physiology. Cell Mol Life Sci 2015; 72:2779-92. [PMID: 26091747 PMCID: PMC11113959 DOI: 10.1007/s00018-015-1959-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 06/11/2015] [Indexed: 12/26/2022]
Abstract
Connexins and pannexins form connexons, pannexons and membrane channels, which are critically involved in many aspects of cardiovascular physiology. For that reason, a vast number of studies have addressed the role of connexins and pannexins in the arterial and venous systems as well as in the heart. Moreover, a role for connexins in lymphatics has recently also been suggested. This review provides an overview of the current knowledge regarding the involvement of connexins and pannexins in cardiovascular physiology.
Collapse
Affiliation(s)
- Merlijn J. Meens
- Department of Pathology and Immunology, University of Geneva, Rue Michel-Servet 1, 1211 Geneva 4, Switzerland
- Department of Medical Specializations-Cardiology, University of Geneva, Geneva, Switzerland
| | - Brenda R. Kwak
- Department of Pathology and Immunology, University of Geneva, Rue Michel-Servet 1, 1211 Geneva 4, Switzerland
- Department of Medical Specializations-Cardiology, University of Geneva, Geneva, Switzerland
| | | |
Collapse
|
31
|
Benam KH, Dauth S, Hassell B, Herland A, Jain A, Jang KJ, Karalis K, Kim HJ, MacQueen L, Mahmoodian R, Musah S, Torisawa YS, van der Meer AD, Villenave R, Yadid M, Parker KK, Ingber DE. Engineered in vitro disease models. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2015; 10:195-262. [PMID: 25621660 DOI: 10.1146/annurev-pathol-012414-040418] [Citation(s) in RCA: 366] [Impact Index Per Article: 40.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The ultimate goal of most biomedical research is to gain greater insight into mechanisms of human disease or to develop new and improved therapies or diagnostics. Although great advances have been made in terms of developing disease models in animals, such as transgenic mice, many of these models fail to faithfully recapitulate the human condition. In addition, it is difficult to identify critical cellular and molecular contributors to disease or to vary them independently in whole-animal models. This challenge has attracted the interest of engineers, who have begun to collaborate with biologists to leverage recent advances in tissue engineering and microfabrication to develop novel in vitro models of disease. As these models are synthetic systems, specific molecular factors and individual cell types, including parenchymal cells, vascular cells, and immune cells, can be varied independently while simultaneously measuring system-level responses in real time. In this article, we provide some examples of these efforts, including engineered models of diseases of the heart, lung, intestine, liver, kidney, cartilage, skin and vascular, endocrine, musculoskeletal, and nervous systems, as well as models of infectious diseases and cancer. We also describe how engineered in vitro models can be combined with human inducible pluripotent stem cells to enable new insights into a broad variety of disease mechanisms, as well as provide a test bed for screening new therapies.
Collapse
Affiliation(s)
- Kambez H Benam
- Wyss Institute for Biologically Inspired Engineering at Harvard University, Boston, Massachusetts 02115;
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Tan Y, Richards D, Xu R, Stewart-Clark S, Mani SK, Borg TK, Menick DR, Tian B, Mei Y. Silicon nanowire-induced maturation of cardiomyocytes derived from human induced pluripotent stem cells. NANO LETTERS 2015; 15:2765-72. [PMID: 25826336 PMCID: PMC4431939 DOI: 10.1021/nl502227a] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The current inability to derive mature cardiomyocytes from human pluripotent stem cells has been the limiting step for transitioning this powerful technology into clinical therapies. To address this, scaffold-based tissue engineering approaches have been utilized to mimic heart development in vitro and promote maturation of cardiomyocytes derived from human pluripotent stem cells. While scaffolds can provide 3D microenvironments, current scaffolds lack the matched physical/chemical/biological properties of native extracellular environments. On the other hand, scaffold-free, 3D cardiac spheroids (i.e., spherical-shaped microtissues) prepared by seeding cardiomyocytes into agarose microwells were shown to improve cardiac functions. However, cardiomyocytes within the spheroids could not assemble in a controlled manner and led to compromised, unsynchronized contractions. Here, we show, for the first time, that incorporation of a trace amount (i.e., ∼0.004% w/v) of electrically conductive silicon nanowires (e-SiNWs) in otherwise scaffold-free cardiac spheroids can form an electrically conductive network, leading to synchronized and significantly enhanced contraction (i.e., >55% increase in average contraction amplitude), resulting in significantly more advanced cellular structural and contractile maturation.
Collapse
Affiliation(s)
- Yu Tan
- Bioengineering Department, Clemson University, Clemson, SC 29634, USA
| | - Dylan Richards
- Bioengineering Department, Clemson University, Clemson, SC 29634, USA
| | - Ruoyu Xu
- Department of Chemistry, the James Franck Institute and the Institute for Biophysical Dynamics, the University of Chicago, Chicago, IL 60637, USA
| | | | - Santhosh Kumar Mani
- Division of Cardiology, Department of Medicine, Gazes Cardiac Research Institute, Medical University of South Carolina, Charleston SC 29425, USA
| | - Thomas Keith Borg
- Bioengineering Department, Clemson University, Clemson, SC 29634, USA
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Donald R. Menick
- Division of Cardiology, Department of Medicine, Gazes Cardiac Research Institute, Medical University of South Carolina, Charleston SC 29425, USA
| | - Bozhi Tian
- Department of Chemistry, the James Franck Institute and the Institute for Biophysical Dynamics, the University of Chicago, Chicago, IL 60637, USA
| | - Ying Mei
- Bioengineering Department, Clemson University, Clemson, SC 29634, USA
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, USA
| |
Collapse
|
33
|
George SA, Sciuto KJ, Lin J, Salama ME, Keener JP, Gourdie RG, Poelzing S. Extracellular sodium and potassium levels modulate cardiac conduction in mice heterozygous null for the Connexin43 gene. Pflugers Arch 2015; 467:2287-97. [PMID: 25771952 DOI: 10.1007/s00424-015-1698-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 02/18/2015] [Accepted: 03/02/2015] [Indexed: 11/27/2022]
Abstract
UNLABELLED Several studies have disagreed on measurements of cardiac conduction velocity (CV) in mice with a heterozygous knockout of the connexin gene Gja1--a mutation that reduces the gap junction (GJ) protein, Connexin43 (Cx43), by 50 %. We noted that perfusate ionic composition varied between studies and hypothesized that extracellular ionic concentration modulates CV dependence on GJs. CV was measured by optically mapping wild-type (WT) and heterozygous null (HZ) hearts serially perfused with solutions previously associated with no change (Solution 1) or CV slowing (Solution 2). In WT hearts, CV was similar for Solutions 1 and 2. However, consistent with the hypothesis, Solution 2 in HZ hearts slowed transverse CV (CVT) relative to Solution 1. Previously, we showed CV slowing in a manner consistent with ephaptic conduction correlated with increased perinexal inter-membrane width (W P) at GJ edges. Thus, W P was measured following perfusion with systematically adjusted [Na(+)]o and [K(+)]o in Solutions 1 and 2. A wider W P was associated with reduced CVT in WT and HZ hearts, with the greatest effect in HZ hearts. Increasing [Na(+)]o increased CVT only in HZ hearts. Increasing [K(+)]o slowed CVT in both WT and HZ hearts with large W P but only in HZ hearts with narrow W P. CONCLUSION When perinexi are wide, decreasing excitability by modulating [Na(+)]o and [K(+)]o increases CV sensitivity to reduced Cx43. By contrast, CV is less sensitive to Cx43 and ion composition when perinexi are narrow. These results are consistent with cardiac conduction dependence on both GJ and non-GJ (ephaptic) mechanisms.
Collapse
Affiliation(s)
- Sharon A George
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
- Center for Heart and Regenerative Medicine, Virginia Tech Carilion Research Institute, 2 Riverside Circle, Roanoke, VA, 24016, USA
| | - Katherine J Sciuto
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, USA
| | - Joyce Lin
- Department of Mathematics, California Polytechnic State University, San Luis Obispo, CA, USA
| | - Mohamed E Salama
- Department of Pathology, University of Utah and ARUP Reference Lab Institute of Research, Salt Lake City, UT, USA
| | - James P Keener
- Department of Mathematics, University of Utah, Salt Lake City, UT, USA
| | - Robert G Gourdie
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
- Center for Heart and Regenerative Medicine, Virginia Tech Carilion Research Institute, 2 Riverside Circle, Roanoke, VA, 24016, USA
| | - Steven Poelzing
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA.
- Center for Heart and Regenerative Medicine, Virginia Tech Carilion Research Institute, 2 Riverside Circle, Roanoke, VA, 24016, USA.
| |
Collapse
|
34
|
Kessler EL, Boulaksil M, van Rijen HVM, Vos MA, van Veen TAB. Passive ventricular remodeling in cardiac disease: focus on heterogeneity. Front Physiol 2014; 5:482. [PMID: 25566084 PMCID: PMC4273631 DOI: 10.3389/fphys.2014.00482] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 11/24/2014] [Indexed: 12/20/2022] Open
Abstract
Passive ventricular remodeling is defined by the process of molecular ventricular adaptation to different forms of cardiac pathophysiology. It includes changes in tissue architecture, such as hypertrophy, fiber disarray, alterations in cell size and fibrosis. Besides that, it also includes molecular remodeling of gap junctions, especially those composed by Connexin43 proteins (Cx43) in the ventricles that affect cell-to-cell propagation of the electrical impulse, and changes in the sodium channels that modify excitability. All those alterations appear mainly in a heterogeneous manner, creating irregular and inhomogeneous electrical and mechanical coupling throughout the heart. This can predispose to reentry arrhythmias and adds to a further deterioration into heart failure. In this review, passive ventricular remodeling is described in Hypertrophic Cardiomyopathy (HCM), Dilated Cardiomyopathy (DCM), Ischemic Cardiomyopathy (ICM), and Arrhythmogenic Cardiomyopathy (ACM), with a main focus on the heterogeneity of those alterations mentioned above.
Collapse
Affiliation(s)
- Elise L Kessler
- Division of Heart and Lungs, Department of Medical Physiology, University Medical Center Utrecht Utrecht, Netherlands
| | - Mohamed Boulaksil
- Division of Heart and Lungs, Department of Medical Physiology, University Medical Center Utrecht Utrecht, Netherlands ; Department of Cardiology, Radboud University Medical Center Nijmegen, Netherlands
| | - Harold V M van Rijen
- Division of Heart and Lungs, Department of Medical Physiology, University Medical Center Utrecht Utrecht, Netherlands
| | - Marc A Vos
- Division of Heart and Lungs, Department of Medical Physiology, University Medical Center Utrecht Utrecht, Netherlands
| | - Toon A B van Veen
- Division of Heart and Lungs, Department of Medical Physiology, University Medical Center Utrecht Utrecht, Netherlands
| |
Collapse
|
35
|
Seki A, Nishii K, Hagiwara N. Gap junctional regulation of pressure, fluid force, and electrical fields in the epigenetics of cardiac morphogenesis and remodeling. Life Sci 2014; 129:27-34. [PMID: 25447447 DOI: 10.1016/j.lfs.2014.10.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Revised: 10/16/2014] [Accepted: 10/29/2014] [Indexed: 01/25/2023]
Abstract
Epigenetic factors of pressure load, fluid force, and electrical fields that occur during cardiac contraction affect cardiac development, morphology, function, and pathogenesis. These factors are orchestrated by intercellular communication mediated by gap junctions, which synchronize action potentials and second messengers. Misregulation of the gap junction protein connexin (Cx) alters cardiogenesis, and can be a pathogenic factor causing cardiac conduction disturbance, fatal arrhythmia, and cardiac remodeling in disease states such as hypertension and ischemia. Changes in Cx expression can occur even when the DNA sequence of the Cx gene itself is unaltered. Posttranslational modifications might reduce arrhythmogenic substrates, improve cardiac function, and promote remodeling in a diseased heart. In this review, we discuss the epigenetic features of gap junctions that regulate cardiac morphology and remodeling. We further discuss potential clinical applications of current knowledge of the structure and function of gap junctions.
Collapse
Affiliation(s)
- Akiko Seki
- Department of Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan; Support Center for Women Health Care Professionals and Researchers, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan.
| | - Kiyomasa Nishii
- Department of Anatomy and Neurobiology, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan
| | - Nobuhisa Hagiwara
- Department of Cardiology, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan
| |
Collapse
|
36
|
Kleber AG, Saffitz JE. Role of the intercalated disc in cardiac propagation and arrhythmogenesis. Front Physiol 2014; 5:404. [PMID: 25368581 PMCID: PMC4201087 DOI: 10.3389/fphys.2014.00404] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 09/30/2014] [Indexed: 01/28/2023] Open
Abstract
This review article discusses mechanisms underlying impulse propagation in cardiac muscle with specific emphasis on the role of the cardiac cell-to-cell junction, called the “intercalated disc.”The first part of this review deals with the role of gap junction channels, formed by connexin proteins, as a determinant of impulse propagation. It is shown that, depending on the underlying structure of the cellular network, decreasing the conductance of gap junction channels (so-called “electrical uncoupling”) may either only slow, or additionally stabilize propagation and reverse unidirectional propagation block to bidirectional propagation. This is because the safety factor for propagation increases with decreasing intercellular electrical conductance. The role of heterogeneous connexin expression, which may be present in disease states, is also discussed. The hypothesis that so-called ephaptic impulse transmission plays a role in heart and can substitute for electrical coupling has been revived recently. Whereas ephaptic transmission can be demonstrated in theoretical simulations, direct experimental evidence has not yet been presented. The second part of this review deals with the interaction of three protein complexes at the intercalated disc: (1) desmosomal and adherens junction proteins, (2) ion channel proteins, and (3) gap junction channels consisting of connexins. Recent work has revealed multiple interactions between these three protein complexes which occur, at least in part, at the level of protein trafficking. Such interactions are likely to play an important role in the pathogenesis of arrhythmogenic cardiomyopathy, and may reveal new therapeutic concepts and targets.
Collapse
Affiliation(s)
- Andre G Kleber
- Department of Pathology, Beth Israel Medical Center, Harvard Medical School Boston, MA, USA
| | - Jeffrey E Saffitz
- Department of Pathology, Beth Israel Medical Center, Harvard Medical School Boston, MA, USA
| |
Collapse
|
37
|
Prudat Y, Kucera JP. Nonlinear behaviour of conduction and block in cardiac tissue with heterogeneous expression of connexin 43. J Mol Cell Cardiol 2014; 76:46-54. [PMID: 25128085 DOI: 10.1016/j.yjmcc.2014.07.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 07/25/2014] [Accepted: 07/31/2014] [Indexed: 11/18/2022]
Abstract
Altered gap junctional coupling potentiates slow conduction and arrhythmias. To better understand how heterogeneous connexin expression affects conduction at the cellular scale, we investigated conduction in tissue consisting of two cardiomyocyte populations expressing different connexin levels. Conduction was mapped using microelectrode arrays in cultured strands of foetal murine ventricular myocytes with predefined contents of connexin 43 knockout (Cx43KO) cells. Corresponding computer simulations were run in randomly generated two-dimensional tissues mimicking the cellular architecture of the strands. In the cultures, the relationship between conduction velocity (CV) and Cx43KO cell content was nonlinear. CV first decreased significantly when Cx43KO content was increased from 0 to 50%. When the Cx43KO content was ≥60%, CV became comparable to that in 100% Cx43KO strands. Co-culturing Cx43KO and wild-type cells also resulted in significantly more heterogeneous conduction patterns and in frequent conduction blocks. The simulations replicated this behaviour of conduction. For Cx43KO contents of 10-50%, conduction was slowed due to wavefront meandering between Cx43KO cells. For Cx43KO contents ≥60%, clusters of remaining wild-type cells acted as electrical loads that impaired conduction. For Cx43KO contents of 40-60%, conduction exhibited fractal characteristics, was prone to block, and was more sensitive to changes in ion currents compared to homogeneous tissue. In conclusion, conduction velocity and stability behave in a nonlinear manner when cardiomyocytes expressing different connexin amounts are combined. This behaviour results from heterogeneous current-to-load relationships at the cellular level. Such behaviour is likely to be arrhythmogenic in various clinical contexts in which gap junctional coupling is heterogeneous.
Collapse
Affiliation(s)
- Yann Prudat
- Department of Physiology, University of Bern, Bühlplatz 5, CH-3012 Bern, Switzerland.
| | - Jan P Kucera
- Department of Physiology, University of Bern, Bühlplatz 5, CH-3012 Bern, Switzerland.
| |
Collapse
|
38
|
McCain ML, Desplantez T, Kléber AG. Engineering Cardiac Cell JunctionsIn Vitroto Study the Intercalated Disc. ACTA ACUST UNITED AC 2014; 21:181-91. [DOI: 10.3109/15419061.2014.905931] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
|
39
|
Veeraraghavan R, Poelzing S, Gourdie RG. Intercellular electrical communication in the heart: a new, active role for the intercalated disk. ACTA ACUST UNITED AC 2014; 21:161-7. [PMID: 24735129 DOI: 10.3109/15419061.2014.905932] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Cardiac conduction is the propagation of electrical excitation through the heart and is responsible for triggering individual myocytes to contract in synchrony. Canonically, this process has been thought to occur electrotonically, by means of direct flow of ions from cell to cell. The intercalated disk (ID), the site of contact between adjacent myocytes, has been viewed as a structure composed of mechanical junctions that stabilize the apposition of cell membranes and gap junctions which constitute low resistance pathways between cells. However, emerging evidence suggests a more active role for structures within the ID in mediating intercellular electrical communication by means of non-canonical ephaptic mechanisms. This review will discuss the role of the ID in the context of the canonical, electrotonic view of conduction and highlight new, emerging possibilities of its playing a more active role in ephaptic coupling between cardiac myocytes.
Collapse
Affiliation(s)
- Rengasayee Veeraraghavan
- Center for Cardiovascular and Regenerative Biology, Virginia Tech Carilion Research Institute , Roanoke, VA , USA
| | | | | |
Collapse
|
40
|
Veeraraghavan R, Poelzing S, Gourdie RG. Old cogs, new tricks: a scaffolding role for connexin43 and a junctional role for sodium channels? FEBS Lett 2014; 588:1244-8. [PMID: 24486012 DOI: 10.1016/j.febslet.2014.01.026] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2013] [Revised: 01/17/2014] [Accepted: 01/20/2014] [Indexed: 01/09/2023]
Abstract
Cardiac conduction is the process by which electrical excitation is communicated from cell to cell within the heart, triggering synchronous contraction of the myocardium. The role of conduction defects in precipitating life-threatening arrhythmias in various disease states has spurred scientific interest in the phenomenon. While the understanding of conduction has evolved greatly over the last century, the process has largely been thought to occur via movement of charge between cells via gap junctions. However, it has long been hypothesized that electrical coupling between cardiac myocytes could also occur ephaptically, without direct transfer of ions between cells. This review will focus on recent insights into cardiac myocyte intercalated disk ultrastructure and their implications for conduction research, particularly the ephaptic coupling hypothesis.
Collapse
Affiliation(s)
- Rengasayee Veeraraghavan
- Center for Cardiovascular and Regenerative Biology, Virginia Tech Carilion Research Institute, 2 Riverside Circle, Roanoke, VA 24016, USA.
| | - Steven Poelzing
- Center for Cardiovascular and Regenerative Biology, Virginia Tech Carilion Research Institute, 2 Riverside Circle, Roanoke, VA 24016, USA
| | - Robert G Gourdie
- Center for Cardiovascular and Regenerative Biology, Virginia Tech Carilion Research Institute, 2 Riverside Circle, Roanoke, VA 24016, USA
| |
Collapse
|
41
|
A micropatterning approach for imaging dynamic Cx43 trafficking to cell-cell borders. FEBS Lett 2014; 588:1439-45. [PMID: 24444605 DOI: 10.1016/j.febslet.2014.01.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 12/31/2013] [Accepted: 01/04/2014] [Indexed: 11/22/2022]
Abstract
The precise expression and timely delivery of connexin 43 (Cx43) proteins to form gap junctions are essential for electrical coupling of cardiomyocytes. Growing evidence supports a cytoskeletal-based trafficking paradigm for Cx43 delivery directly to adherens junctions at the intercalated disc. A limitation of Cx43 localization assays in cultured cells, in which cell-cell contacts are essential, is the inability to control for cell geometry or reproducibly generate contact points. Here we present a micropatterned cell pairing system well suited for live microscopy to examine how the microtubule and actin cytoskeleton confer specificity to Cx43 trafficking to precisely defined cell-cell junctions. This system can be adapted for other cell types and used to study dynamic intracellular movements of other proteins important for cell-cell communication.
Collapse
|
42
|
Veeraraghavan R, Gourdie RG, Poelzing S. Mechanisms of cardiac conduction: a history of revisions. Am J Physiol Heart Circ Physiol 2014; 306:H619-27. [PMID: 24414064 DOI: 10.1152/ajpheart.00760.2013] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cardiac conduction is the process by which electrical excitation spreads through the heart, triggering individual myocytes to contract in synchrony. Defects in conduction disrupt synchronous activation and are associated with life-threatening arrhythmias in many pathologies. Therefore, it is scarcely surprising that this phenomenon continues to be the subject of active scientific inquiry. Here we provide a brief review of how the conceptual understanding of conduction has evolved over the last century and highlight recent, potentially paradigm-shifting developments.
Collapse
Affiliation(s)
- Rengasayee Veeraraghavan
- Virginia Tech Carilion Research Institute, and Center for Heart and Regenerative Medicine, Virginia Polytechnic University, Roanoke, Virginia; and
| | | | | |
Collapse
|
43
|
Abstract
While it is widely believed that conduction in cardiac tissue is regulated by gap junctions, recent experimental evidence suggests that the extracellular space may play a significant role in action potential propagation. Cardiac tissue with low gap junctional coupling still exhibits conduction, with conflicting degrees of slowing that may be due to variations in the extracellular space. Inhomogeneities in the extracellular space caused by the complex cellular structure in cardiac tissue can lead to ephaptic, or field effect, coupling. Here, we present data from simulations of a cylindrical strand of cells in which we see the dramatic effect highly resistant extracellular spaces have on propagation velocity. We find that ephaptic effects occur in all areas of small extracellular spaces and are not restricted to the junctional cleft between cells. This previously unrecognized type of field coupling, which we call lateral coupling, can allow conduction in the absence of gap junctions. We compare our results with the classically used cable theory, demonstrating the quantitative difference in propagation velocity arising from the cellular geometry. Ephaptic effects are shown to be highly dependent upon parameter values, frequently enhancing, but sometimes decreasing propagation speed. Our mathematical analysis incorporates the inhomogeneities in the extracellular microdomains that cannot be directly measured by experimental techniques and will aid in optimizing cardiac treatments that require manipulation of the cellular geometry and understanding heart functionality.
Collapse
Affiliation(s)
- Joyce Lin
- Department of Mathematics, University of Utah, Salt Lake City, UT 84112, USA.
| | | |
Collapse
|
44
|
Dhillon PS, Gray R, Kojodjojo P, Jabr R, Chowdhury R, Fry CH, Peters NS. Relationship between gap-junctional conductance and conduction velocity in mammalian myocardium. Circ Arrhythm Electrophysiol 2013; 6:1208-14. [PMID: 24134868 DOI: 10.1161/circep.113.000848] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Gap junction resistivity, R(j), has been proposed as a key determinant of conduction velocity (CV). However, studies in connexin-gene knockout mice demonstrated significant CV slowing only with near-complete connexin deletion, and these findings led to the concept of a significant redundancy of myocardial gap junctions. We challenged this prevailing concept and addressed the hypothesis that there is a continuous relationship between R(j) and CV, each independently measured in human and guinea-pig myocardium. METHODS AND RESULTS R(j) and CV were directly measured by oil-gap impedance and microelectrode techniques in human left ventricular myocardium from patients with hypertrophic cardiomyopathy and in guinea-pig atrial and ventricular myocardium before and during pharmacological uncoupling with 20-µmol/L carbenoxolone. There was a continuous relationship between R(j) and CV in human and guinea-pig myocardium, pre- and post-carbenoxolone (r(2)=0.946; P<0.01). In guinea-pig left ventricle, left atrium, and right atrium, carbenoxolone increased R(j) by 28±9%, 26±16%, and 25±14% and slowed CV by 17±3%, 23±8%, and 11±4% respectively (all P<0.05 versus control). As a clinically accessible measure of local microscopic myocardial conduction slowing in vivo in the intact human heart, carbenoxolone prolonged electrogram duration in the right atrium (39.7±4.2 to 42.3±4.3 ms; P=0.01) and right ventricle (48.1±2.5 to 53.3±5.3 ms; P<0.01). CONCLUSIONS There is a continuous relationship between R(j) and CV that is consistent between cardiac chambers and across species, indicating that naturally occurring variations in cellular coupling can account for variations in CV, and that the concept that there is massive redundancy of coupling is not tenable.
Collapse
Affiliation(s)
- Paramdeep S Dhillon
- Imperial Centre for Translational and Experimental Medicine, Myocardial Function Section, Imperial College London and Imperial College NHS Trust, London, United Kingdom
| | | | | | | | | | | | | |
Collapse
|
45
|
Verheule S, Kaese S. Connexin diversity in the heart: insights from transgenic mouse models. Front Pharmacol 2013; 4:81. [PMID: 23818881 PMCID: PMC3694209 DOI: 10.3389/fphar.2013.00081] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Accepted: 06/04/2013] [Indexed: 11/13/2022] Open
Abstract
Cardiac conduction is mediated by gap junction channels that are formed by connexin (Cx) protein subunits. The connexin family of proteins consists of more than 20 members varying in their biophysical properties and ability to combine with other connexins into heteromeric gap junction channels. The mammalian heart shows regional differences both in connexin expression profile and in degree of electrical coupling. The latter reflects functional requirements for conduction velocity which needs to be low in the sinoatrial and atrioventricular nodes and high in the ventricular conduction system. Over the past 20 years knowledge of the biology of gap junction channels and their role in the genesis of cardiac arrhythmias has increased enormously. This review focuses on the insights gained from transgenic mouse models. The mouse heart expresses Cx30, 30.2, 37, 40, 43, 45, and 46. For these connexins a variety of knock-outs, heart-specific knock-outs, conditional knock-outs, double knock-outs, knock-ins and overexpressors has been studied. We discuss the cardiac phenotype in these models and compare Cx expression between mice and men. Mouse models have enhanced our understanding of (patho)-physiological implications of Cx diversity in the heart. In principle connexin-specific modulation of electrical coupling in the heart represents an interesting treatment strategy for cardiac arrhythmias and conduction disorders.
Collapse
Affiliation(s)
- Sander Verheule
- Department of Physiology, Faculty of Medicine, Maastricht University Maastricht, Netherlands
| | | |
Collapse
|
46
|
The perinexus: sign-post on the path to a new model of cardiac conduction? Trends Cardiovasc Med 2013; 23:222-8. [PMID: 23490883 DOI: 10.1016/j.tcm.2012.12.005] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Revised: 12/19/2012] [Accepted: 12/20/2012] [Indexed: 11/23/2022]
Abstract
The perinexus is a recently identified microdomain surrounding the cardiac gap junction that contains elevated levels of connexin43 and the sodium channel protein, Nav1.5. Ongoing work has established a role for the perinexus in regulating gap junction aggregation. However, recent studies have raised the possibility of a perinexal contribution at the gap junction cleft to intercellular propagation of action potential via non-electrotonic mechanisms. The latter possibility could modify the current theoretical understanding of cardiac conduction, help explain paradoxical experimental findings, and open up entirely new avenues for antiarrhythmic therapy. We review recent structural insights into the perinexus and its potential novel functional role in cardiac-excitation spread, highlighting presently unanswered questions, the evidence for ephaptic conduction in the heart and how structural insights may help complete this picture.
Collapse
|
47
|
Baker C, Taylor DG, Osuala K, Natarajan A, Molnar PJ, Hickman J, Alam S, Moscato B, Weinshenker D, Ebert SN. Adrenergic deficiency leads to impaired electrical conduction and increased arrhythmic potential in the embryonic mouse heart. Biochem Biophys Res Commun 2012; 423:536-41. [PMID: 22683331 DOI: 10.1016/j.bbrc.2012.05.163] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Accepted: 05/31/2012] [Indexed: 11/30/2022]
Abstract
To determine if adrenergic hormones play a critical role in the functional development of the cardiac pacemaking and conduction system, we employed a mouse model where adrenergic hormone production was blocked due to targeted disruption of the dopamine β-hydroxylase (Dbh) gene. Immunofluorescent histochemical evaluation of the major gap junction protein, connexin 43, revealed that its expression was substantially decreased in adrenergic-deficient (Dbh-/-) relative to adrenergic-competent (Dbh+/+ and Dbh+/-) mouse hearts at embryonic day 10.5 (E10.5), whereas pacemaker and structural protein staining appeared similar. To evaluate cardiac electrical conduction in these hearts, we cultured them on microelectrode arrays (8×8, 200 μm apart). Our results show a significant slowing of atrioventricular conduction in adrenergic-deficient hearts compared to controls (31.4±6.4 vs. 15.4±1.7 ms, respectively, p<0.05). To determine if the absence of adrenergic hormones affected heart rate and rhythm, mouse hearts from adrenergic-competent and deficient embryos were cultured ex vivo at E10.5, and heart rates were measured before and after challenge with the β-adrenergic receptor agonist, isoproterenol (0.5 μM). On average, all hearts showed increased heart rate responses following isoproterenol challenge, but a significant (p<0.05) 225% increase in the arrhythmic index (AI) was observed only in adrenergic-deficient hearts. These results show that adrenergic hormones may influence heart development by stimulating connexin 43 expression, facilitating atrioventricular conduction, and helping to maintain cardiac rhythm during a critical phase of embryonic development.
Collapse
Affiliation(s)
- Candice Baker
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, 6900 Lake Nona Blvd, Orlando, FL 32827, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
48
|
Controlling the contractile strength of engineered cardiac muscle by hierarchal tissue architecture. Biomaterials 2012; 33:5732-41. [PMID: 22594976 DOI: 10.1016/j.biomaterials.2012.04.043] [Citation(s) in RCA: 173] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 04/17/2012] [Indexed: 11/23/2022]
Abstract
The heart is a muscular organ with a wrapping, laminar structure embedded with neural and vascular networks, collagen fibrils, fibroblasts, and cardiac myocytes that facilitate contraction. We hypothesized that these non-muscle components may have functional benefit, serving as important structural alignment cues in inter- and intra-cellular organization of cardiac myocytes. Previous studies have demonstrated that alignment of engineered myocardium enhances calcium handling, but how this impacts actual force generation remains unclear. Quantitative assays are needed to determine the effect of alignment on contractile function and muscle physiology. To test this, micropatterned surfaces were used to build 2-dimensional myocardium from neonatal rat ventricular myocytes with distinct architectures: confluent isotropic (serving as the unaligned control), confluent anisotropic, and 20 μm spaced, parallel arrays of multicellular myocardial fibers. We combined image analysis of sarcomere orientation with muscular thin film contractile force assays in order to calculate the peak sarcomere-generated stress as a function of tissue architecture. Here we report that increasing peak systolic stress in engineered cardiac tissues corresponds with increasing sarcomere alignment. This change is larger than would be anticipated from enhanced calcium handling and increased uniaxial alignment alone. These results suggest that boundary conditions (heterogeneities) encoded in the extracellular space can regulate muscle tissue function, and that structural organization and cytoskeletal alignment are critically important for maximizing peak force generation.
Collapse
|
49
|
Beauchamp P, Desplantez T, McCain ML, Li W, Asimaki A, Rigoli G, Parker KK, Saffitz JE, Kleber AG. Electrical coupling and propagation in engineered ventricular myocardium with heterogeneous expression of connexin43. Circ Res 2012; 110:1445-53. [PMID: 22518032 DOI: 10.1161/circresaha.111.259705] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Spatial heterogeneity in connexin (Cx) expression has been implicated in arrhythmogenesis. OBJECTIVE This study was performed to quantify the relation between the degree of heterogeneity in Cx43 expression and disturbances in electric propagation. METHODS AND RESULTS Cell pairs and strands composed of mixtures of Cx43(-/-) (Cx43KO) or GFP-expressing Cx43(+/+) (WT(GFP)) murine ventricular myocytes were patterned using microlithographic techniques. At the interface between pairs of WT(GFP) and Cx43KO cells, dual-voltage clamp showed a marked decrease in electric coupling (approximately 5% of WT) and voltage gating suggested the presence of mixed Cx43/Cx45 channels. Cx43 and Cx45 immunofluorescence signals were not detectable at this interface, probably because of markedly reduced gap junction size. Macroscopic propagation velocity, measured by multisite high-resolution optical mapping of transmembrane potential in strands of cells of mixed Cx43 genotype, decreased with an increasing proportion of Cx43KO cells in the strand. A marked decrease in conduction velocity was observed in strands composed of <50% WT cells. Propagation at the microscopic scale showed a high degree of dissociation between WT(GFP) and Cx43KO cells, but consistent excitation without development of propagation block. CONCLUSIONS Heterogeneous ablation of Cx43 leads to a marked decrease in propagation velocity in tissue strands composed of <50% cells with WT Cx43 expression and marked dissociation of excitation at the cellular level. However, the small residual electric conductance between Cx43 and WT(GFP) myocytes assures excitation of Cx43(-/-) cells. This explains the previously reported undisturbed contractility in tissues with spatially heterogeneous downregulation of Cx43 expression.
Collapse
|
50
|
Desplantez T, McCain ML, Beauchamp P, Rigoli G, Rothen-Rutishauser B, Parker KK, Kleber AG. Connexin43 ablation in foetal atrial myocytes decreases electrical coupling, partner connexins, and sodium current. Cardiovasc Res 2012; 94:58-65. [PMID: 22287588 PMCID: PMC3307380 DOI: 10.1093/cvr/cvs025] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 01/10/2012] [Accepted: 01/23/2012] [Indexed: 11/15/2022] Open
Abstract
AIMS Remodelling and regional gradients in expression of connexins (Cx) are thought to contribute to atrial electrical dysfunction and atrial fibrillation. We assessed the effect of interaction between Cx43, Cx40, and Cx45 on atrial cell-to-cell coupling and inward Na current (I(Na)) in engineered pairs of atrial myocytes derived from wild-type mice (Cx43(+/+)) and mice with genetic ablation of Cx43 (Cx43(-/-)). METHODS AND RESULTS Cell pairs were engineered by microcontact printing from atrial Cx43(+/+) and Cx43(-/-) murine myocytes (1 day before birth, 3-5 days in culture). Dual and single voltage clamp were used to measure intercellular electrical conductance, g(j), and its dependence on transjunctional voltage, V(j), single gap junction channel conductances, and I(Na). 3D reconstructions of Cx43, Cx40, and Cx45 immunosignals in gap junctions were made from confocal slices. Full genetic Cx43 ablation produced a decrease in immunosignals of Cx40 to 62 ± 10% (mean ± SE; n= 17) and Cx45 to 66 ± 8% (n= 16). G(j) decreased from 80 ± 9 nS (Cx43(+/+), n= 17) to 24 ± 2 nS (Cx43(-/-), n= 35). Single channel analysis showed a shift in the main peak of the channel histogram from 49 ± 1.7 nS (Cx43(+/+)) to 67 ± 1.8 nS (Cx43(-/-)) with a second minor peak appearing at 27 ± 1.5 pS. The dependence of g(j) on V(j) decreased with Cx43 ablation. Importantly, peak I(Na) decreased from -350 ± 44 pA/pF (Cx43(+/+)) to -154 ± 28 pA/pF (Cx43(-/-)). CONCLUSIONS The dependence of Cx40, Cx45, and I(Na) on Cx43 expression indicates a complex interaction between connexins and I(Na) in the atrial intercalated discs that is likely to be of relevance for arrhythmogenesis.
Collapse
Affiliation(s)
| | - Megan L. McCain
- Disease Biophysics Group, School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | | | | | | | - Kevin Kit Parker
- Disease Biophysics Group, School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Andre G. Kleber
- Department of Physiology, University of Bern, Bern, Switzerland
| |
Collapse
|