1
|
Birla RK. State of the art in Purkinje bioengineering. Tissue Cell 2024; 90:102467. [PMID: 39053130 DOI: 10.1016/j.tice.2024.102467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 06/09/2024] [Accepted: 07/08/2024] [Indexed: 07/27/2024]
Abstract
This review article will cover the recent developments in the new evolving field of Purkinje bioengineering and the development of human Purkinje networks. Recent work has progressed to the point of a methodological and systematic process to bioengineer Purkinje networks. This involves the development of 3D models based on human anatomy, followed by the development of tunable biomaterials, and strategies to reprogram stem cells to Purkinje cells. Subsequently, the reprogrammed cells and the biomaterials are coupled to bioengineer Purkinje networks, which are then tested using a small animal injury model. In this article, we discuss this process as a whole and then each step separately. We then describe potential applications of bioengineered Purkinje networks and challenges in the field that need to be overcome to move this field forward. Although the field of Purkinje bioengineering is new and in a state of infancy, it holds tremendous potential, both for therapeutic applications and to develop tools that can be used for disease modeling.
Collapse
Affiliation(s)
- Ravi K Birla
- Laboratory for Regenerative Tissue Repair, Texas Children's Hospital, Houston, TX, USA; Center for Congenital Cardiac Research, Texas Children's Hospital, Houston, TX, USA; Division of Congenital Heart Surgery, Texas Children's Hospital, Houston, TX, USA; Department of Surgery, Baylor College of Medicine, Houston, TX, USA; Division of Pediatric Surgery, Department of Surgery, Texas Children's Hospital, Houston, TX, USA.
| |
Collapse
|
2
|
Dries E, Gilbert G, Roderick HL, Sipido KR. The ryanodine receptor microdomain in cardiomyocytes. Cell Calcium 2023; 114:102769. [PMID: 37390591 DOI: 10.1016/j.ceca.2023.102769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 06/11/2023] [Accepted: 06/12/2023] [Indexed: 07/02/2023]
Abstract
The ryanodine receptor type 2 (RyR) is a key player in Ca2+ handling during excitation-contraction coupling. During each heartbeat, RyR channels are responsible for linking the action potential with the contractile machinery of the cardiomyocyte by releasing Ca2+ from the sarcoplasmic reticulum. RyR function is fine-tuned by associated signalling molecules, arrangement in clusters and subcellular localization. These parameters together define RyR function within microdomains and are subject to disease remodelling. This review describes the latest findings on RyR microdomain organization, the alterations with disease which result in increased subcellular heterogeneity and emergence of microdomains with enhanced arrhythmogenic potential, and presents novel technologies that guide future research to study and target RyR channels within specific microdomains.
Collapse
Affiliation(s)
- Eef Dries
- Lab of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium.
| | - Guillaume Gilbert
- Lab of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium; Laboratoire ORPHY EA 4324, Université de Brest, Brest, France
| | - H Llewelyn Roderick
- Lab of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Karin R Sipido
- Lab of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| |
Collapse
|
3
|
Disse P, Aymanns I, Mücher L, Sandmann S, Varghese J, Ritter N, Strutz-Seebohm N, Seebohm G, Peischard S. Knockout of the Cardiac Transcription Factor NKX2-5 Results in Stem Cell-Derived Cardiac Cells with Typical Purkinje Cell-like Signal Transduction and Extracellular Matrix Formation. Int J Mol Sci 2023; 24:13366. [PMID: 37686171 PMCID: PMC10487652 DOI: 10.3390/ijms241713366] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 08/16/2023] [Accepted: 08/27/2023] [Indexed: 09/10/2023] Open
Abstract
The human heart controls blood flow, and therewith enables the adequate supply of oxygen and nutrients to the body. The correct function of the heart is coordinated by the interplay of different cardiac cell types. Thereby, one can distinguish between cells of the working myocardium, the pace-making cells in the sinoatrial node (SAN) and the conduction system cells in the AV-node, the His-bundle or the Purkinje fibres. Tissue-engineering approaches aim to generate hiPSC-derived cardiac tissues for disease modelling and therapeutic usage with a significant improvement in the differentiation quality of myocardium and pace-making cells. The differentiation of cells with cardiac conduction system properties is still challenging, and the produced cell mass and quality is poor. Here, we describe the generation of cardiac cells with properties of the cardiac conduction system, called conduction system-like cells (CSLC). As a primary approach, we introduced a CrispR-Cas9-directed knockout of the NKX2-5 gene in hiPSC. NKX2-5-deficient hiPSC showed altered connexin expression patterns characteristic for the cardiac conduction system with strong connexin 40 and connexin 43 expression and suppressed connexin 45 expression. Application of differentiation protocols for ventricular- or SAN-like cells could not reverse this connexin expression pattern, indicating a stable regulation by NKX2-5 on connexin expression. The contraction behaviour of the hiPSC-derived CSLCs was compared to hiPSC-derived ventricular- and SAN-like cells. We found that the contraction speed of CSLCs resembled the expected contraction rate of human conduction system cells. Overall contraction was reduced in differentiated cells derived from NKX2-5 knockout hiPSC. Comparative transcriptomic data suggest a specification of the cardiac subtype of CSLC that is distinctly different from ventricular or pacemaker-like cells with reduced myocardial gene expression and enhanced extracellular matrix formation for improved electrical insulation. In summary, knockout of NKX2-5 in hiPSC leads to enhanced differentiation of cells with cardiac conduction system features, including connexin expression and contraction behaviour.
Collapse
Affiliation(s)
- Paul Disse
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, D-48149 Münster, Germany
| | - Isabel Aymanns
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, D-48149 Münster, Germany
| | - Lena Mücher
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, D-48149 Münster, Germany
| | - Sarah Sandmann
- Institute of Medical Informatics, University of Münster, D-48149 Münster, Germany
| | - Julian Varghese
- Institute of Medical Informatics, University of Münster, D-48149 Münster, Germany
| | - Nadine Ritter
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, D-48149 Münster, Germany
| | - Nathalie Strutz-Seebohm
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, D-48149 Münster, Germany
| | - Guiscard Seebohm
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, D-48149 Münster, Germany
| | - Stefan Peischard
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, D-48149 Münster, Germany
| |
Collapse
|
4
|
Iop L, Iliceto S, Civieri G, Tona F. Inherited and Acquired Rhythm Disturbances in Sick Sinus Syndrome, Brugada Syndrome, and Atrial Fibrillation: Lessons from Preclinical Modeling. Cells 2021; 10:3175. [PMID: 34831398 PMCID: PMC8623957 DOI: 10.3390/cells10113175] [Citation(s) in RCA: 3] [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: 09/20/2021] [Revised: 11/03/2021] [Accepted: 11/09/2021] [Indexed: 12/12/2022] Open
Abstract
Rhythm disturbances are life-threatening cardiovascular diseases, accounting for many deaths annually worldwide. Abnormal electrical activity might arise in a structurally normal heart in response to specific triggers or as a consequence of cardiac tissue alterations, in both cases with catastrophic consequences on heart global functioning. Preclinical modeling by recapitulating human pathophysiology of rhythm disturbances is fundamental to increase the comprehension of these diseases and propose effective strategies for their prevention, diagnosis, and clinical management. In silico, in vivo, and in vitro models found variable application to dissect many congenital and acquired rhythm disturbances. In the copious list of rhythm disturbances, diseases of the conduction system, as sick sinus syndrome, Brugada syndrome, and atrial fibrillation, have found extensive preclinical modeling. In addition, the electrical remodeling as a result of other cardiovascular diseases has also been investigated in models of hypertrophic cardiomyopathy, cardiac fibrosis, as well as arrhythmias induced by other non-cardiac pathologies, stress, and drug cardiotoxicity. This review aims to offer a critical overview on the effective ability of in silico bioinformatic tools, in vivo animal studies, in vitro models to provide insights on human heart rhythm pathophysiology in case of sick sinus syndrome, Brugada syndrome, and atrial fibrillation and advance their safe and successful translation into the cardiology arena.
Collapse
Affiliation(s)
- Laura Iop
- Department of Cardiac Thoracic Vascular Sciences and Public Health, University of Padua, Via Giustiniani, 2, I-35124 Padua, Italy; (S.I.); (G.C.)
| | | | | | - Francesco Tona
- Department of Cardiac Thoracic Vascular Sciences and Public Health, University of Padua, Via Giustiniani, 2, I-35124 Padua, Italy; (S.I.); (G.C.)
| |
Collapse
|
5
|
Greene D, Shiferaw Y. Mechanistic link between CaM-RyR2 interactions and the genesis of cardiac arrhythmia. Biophys J 2021; 120:1469-1482. [PMID: 33617831 DOI: 10.1016/j.bpj.2021.02.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 01/13/2021] [Accepted: 02/08/2021] [Indexed: 12/01/2022] Open
Abstract
In this study, we develop a computational model of the interaction between ryanodine receptor type 2 (RyR2) and calmodulin (CaM) to explore the mechanistic link between CaM-RyR2 interactions and cardiac arrhythmia. Our starting point is a biophysically based computational model of CaM binding to a single RyR2 subunit, which reproduces single-channel RyR2 measurements in lipid bilayers. We then integrate this CaM-RyR2 model into a spatially distributed whole-cell model of Ca cycling, which is used to investigate the relationship between CaM and Ca cycling homeostasis. We show that a reduction in CaM concentration leads to a substantial increase in the rate of spontaneous Ca sparks, and this induces a marked reduction in sarcoplasmic reticulum Ca load during steady-state pacing. Also, we show that a reduction in CaM modifies the RyR2 open probability, which makes the cell more prone to Ca wave propagation. These results indicate that aberrant Ca cycling activity during pacing is determined by the interplay between sarcoplasmic reticulum load reduction and the threshold for Ca wave propagation. Based on these results, we show that when CaM is reduced, Ca waves can occur in a cell and induce action potential perturbations that are arrhythmogenic. Thus, this study outlines a novel, to our knowledge, mechanistic link between CaM-RyR2 binding kinetics and the induction of arrhythmias in the heart.
Collapse
Affiliation(s)
- D'Artagnan Greene
- Department of Physics, California State University Northridge, Los Angeles, California
| | - Yohannes Shiferaw
- Department of Physics, California State University Northridge, Los Angeles, California.
| |
Collapse
|
6
|
Shah C, Jiwani S, Limbu B, Weinberg S, Deo M. Delayed afterdepolarization-induced triggered activity in cardiac purkinje cells mediated through cytosolic calcium diffusion waves. Physiol Rep 2020; 7:e14296. [PMID: 31872561 PMCID: PMC6928245 DOI: 10.14814/phy2.14296] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Cardiac Purkinje cells (PCs) are more susceptible to action potential abnormalities as compared to ventricular myocytes (VMs), which could be associated with their distinct intracellular calcium handling. We developed a detailed biophysical model of a mouse cardiac PC, which importantly reproduces the experimentally observed biphasic cytosolic calcium waves. The model includes a stochastic gating formulation for the opening and closing of ryanodine receptor (RyR) channels, simulated with a Monte Carlo method, to accurately reproduce cytosolic calcium wave propagation and the effects of spontaneous calcium release events. Simulations predict that during an action potential, smaller cytosolic calcium wavelets propagated from the sarcolemma towards the center of the cell and initiated larger magnitude cell‐wide calcium waves via a calcium‐induced‐calcium release mechanism. In the presence of RyR mutations, frequent spontaneous calcium leaks from sarcoplasmic reticulum (SR) initiated calcium waves, which upon reaching the cell periphery produced delayed afterdepolarizations (DADs) via sodium‐calcium exchanger (NCX) and T‐type calcium (ICaT) channel activation. In the presence of isoproterenol‐mediated effects, DADs induced triggered activity by reactivation of fast sodium channels. Based on our model, we found that the activation of either L‐type calcium channels (ICaL), ICaT, sodium‐potassium exchanger (INaK) or NCX is sufficient for occurrence of triggered activity; however, a partial blockade of ICaT or INaK is essential for its successful termination. Our modeling study highlights valuable insights into the mechanisms of DAD‐induced triggered activity mediated via cytosolic calcium waves in cardiac PCs and may elucidate the increased arrhythmogeneity in PCs.
Collapse
Affiliation(s)
- Chirag Shah
- School of Medicine, Eastern Virginia Medical School, Norfolk, Virginia
| | - Sohel Jiwani
- Department of Engineering, Norfolk State University, Norfolk, Virginia
| | - Bijay Limbu
- Department of Engineering, Norfolk State University, Norfolk, Virginia
| | - Seth Weinberg
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, Virginia.,Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio
| | - Makarand Deo
- Department of Engineering, Norfolk State University, Norfolk, Virginia
| |
Collapse
|
7
|
Trovato C, Passini E, Nagy N, Varró A, Abi-Gerges N, Severi S, Rodriguez B. Human Purkinje in silico model enables mechanistic investigations into automaticity and pro-arrhythmic abnormalities. J Mol Cell Cardiol 2020; 142:24-38. [PMID: 32251669 PMCID: PMC7294239 DOI: 10.1016/j.yjmcc.2020.04.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 03/30/2020] [Accepted: 04/01/2020] [Indexed: 02/06/2023]
Abstract
Cardiac Purkinje cells (PCs) are implicated in lethal arrhythmias caused by cardiac diseases, mutations, and drug action. However, the pro-arrhythmic mechanisms in PCs are not entirely understood, particularly in humans, as most investigations are conducted in animals. The aims of this study are to present a novel human PCs electrophysiology biophysically-detailed computational model, and to disentangle ionic mechanisms of human Purkinje-related electrophysiology, pacemaker activity and arrhythmogenicity. The new Trovato2020 model incorporates detailed Purkinje-specific ionic currents and Ca2+ handling, and was developed, calibrated and validated using human experimental data acquired at multiple frequencies, both in control conditions and following drug application. Multiscale investigations were performed in a Purkinje cell, in fibre and using an experimentally-calibrated population of PCs to evaluate biological variability. Simulations demonstrate the human Purkinje Trovato2020 model is the first one to yield: (i) all key AP features consistent with human Purkinje recordings; (ii) Automaticity with funny current up-regulation (iii) EADs at slow pacing and with 85% hERG block; (iv) DADs following fast pacing; (v) conduction velocity of 160 cm/s in a Purkinje fibre, as reported in human. The human in silico PCs population highlights that: (1) EADs are caused by ICaL reactivation in PCs with large inward currents; (2) DADs and triggered APs occur in PCs experiencing Ca2+ accumulation, at fast pacing, caused by large L-type calcium current and small Na+/Ca2+ exchanger. The novel human Purkinje model unlocks further investigations into the role of cardiac Purkinje in ventricular arrhythmias through computer modeling and multiscale simulations.
Collapse
Affiliation(s)
- Cristian Trovato
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford OX13QD, United Kingdom.
| | - Elisa Passini
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford OX13QD, United Kingdom
| | - Norbert Nagy
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged H-6720, Hungary; Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged H-6720, Hungary; Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - Najah Abi-Gerges
- AnaBios Corporation, San Diego Science Center, San Diego, CA 92109, USA
| | - Stefano Severi
- Department of Electrical, Electronic and Information Engineering, University of Bologna, Cesena 47521, Italy
| | - Blanca Rodriguez
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford OX13QD, United Kingdom.
| |
Collapse
|
8
|
Reply to Entcheva: The impact of T-tubules on action potential propagation in cardiac tissue. Proc Natl Acad Sci U S A 2018; 115:E562-E563. [PMID: 29305385 DOI: 10.1073/pnas.1720253115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
|
9
|
Song Z, Liu MB, Qu Z. Transverse tubular network structures in the genesis of intracellular calcium alternans and triggered activity in cardiac cells. J Mol Cell Cardiol 2018; 114:288-299. [PMID: 29217432 PMCID: PMC5801147 DOI: 10.1016/j.yjmcc.2017.12.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 10/31/2017] [Accepted: 12/04/2017] [Indexed: 12/20/2022]
Abstract
RATIONALE The major role of a transverse-tubular (TT) network in a cardiac cell is to facilitate effective excitation-contraction coupling and signaling. The TT network structures are heterogeneous within a single cell, and vary between different types of cells and species. They are also remodeled in cardiac diseases. However, how different TT network structures predispose cardiac cells to arrhythmogenesis remains to be revealed. OBJECTIVE To systematically investigate the roles of TT network structure and the underlying mechanisms in the genesis of intracellular calcium (Ca2+) alternans and triggered activity (TA). METHODS AND RESULTS Based on recent experimental observations, different TT network structures, including uniformly and non-uniformly random TT distributions, were modeled in a cardiac cell model consisting of a three-dimensional network of Ca2+ release units (CRUs). Our simulations showed that both Ca2+ alternans and Ca2+ wave-mediated TA were promoted when the fraction of orphaned CRUs was in an intermediate range, but suppressed in cells exhibiting either well-organized TT networks or low TT densities. Ca2+ alternans and TA could be promoted by low TT densities when the cells were small or the CRU coupling was strong. Both alternans and TA occurred more easily in uniformly random TT networks than in non-uniformly random TT networks. Subcellular spatially discordant Ca2+ alternans was promoted by non-uniformly random TT networks but suppressed by increasing CRU coupling strength. These mechanistic insights provide a holistic understanding of the effects of TT network structure on the susceptibility to arrhythmogenesis. CONCLUSIONS The TT network plays important roles in promoting Ca2+ alternans and TA, and different TT network structures may predispose cardiac cells differently to arrhythmogenesis.
Collapse
Affiliation(s)
- Zhen Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
| | - Michael B Liu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA; Department of Biomathematics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
| |
Collapse
|
10
|
Matsuyama TA, Tanaka H, Ishibashi-Ueda H, Takamatsu T. Spatiotemporally Non-Uniform Ca 2+ Dynamics of Cardiac Purkinje Fibers in Mouse Myocardial Infarct. J Histochem Cytochem 2017; 65:655-667. [PMID: 28903013 DOI: 10.1369/0022155417730280] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Surviving Purkinje fibers in myocardial infarct are regarded as an important substrate in arrhythmogenesis. However, poorly understood are functional properties of Purkinje fibers in the infarcted heart. We sought to visualize intracellular Ca2+ ([Ca2+]i) dynamics of Purkinje fiber networks in the mouse myocardial infarct. Using 3- to 4-day-old or 7- to 9-day-old infarcted hearts after the left coronary-artery ligation corresponding, respectively, to acute or healing phase, we conducted rapid fluo4-fluorescence imaging on the endocardial surface of the left ventricular septum by macro-zoom fluorescence microscopy and rapid-scanning confocal microscopy. In contrast with the intact heart, where uniform Ca2+ transients propagated rapidly, the infarcted heart exhibited slow, non-uniform impulse propagations. On confocal microscopy, Purkinje fibers in the peri-infarct zone exhibited non-uniform [Ca2+]i dynamics: beat-to-beat alternans of the Ca2+ transient amplitude in and among the individual fibers, whereas the intact fibers exhibited uniform Ca2+ transients. Such non-uniform [Ca2+]i dynamics were more conspicuous in the acute infarcted hearts than in the healing ones. In accordance with [Ca2+]i dynamics, fixed fluo4-loaded heart preparations exhibited definitive connexin-40 plaques in the peri-infarct Purkinje fibers, whereas the subjacent myocardium presented coagulative necrosis and granulation tissues, respectively. The surviving Purkinje fibers in the peri-infarct zone exhibited non-uniform [Ca2+]i dynamics, which may lead to arrhythmogenesis.
Collapse
Affiliation(s)
- Taka-Aki Matsuyama
- Department of Pathology and Cell Regulation, Kyoto Prefectural University of Medicine Graduate School of Medical Science, Kyoto, Japan
| | - Hideo Tanaka
- Department of Pathology and Cell Regulation, Kyoto Prefectural University of Medicine Graduate School of Medical Science, Kyoto, Japan
| | - Hatsue Ishibashi-Ueda
- Department of Pathology, National Cerebral and Cardiovascular Center, Suita, Osaka, Japan
| | - Tetsuro Takamatsu
- Department of Medical Photonics, Kyoto Prefectural University of Medicine, Kyoto, Japan
| |
Collapse
|
11
|
Abstract
Unique to striated muscle cells, transverse tubules (t-tubules) are membrane organelles that consist of sarcolemma penetrating into the myocyte interior, forming a highly branched and interconnected network. Mature t-tubule networks are found in mammalian ventricular cardiomyocytes, with the transverse components of t-tubules occurring near sarcomeric z-discs. Cardiac t-tubules contain membrane microdomains enriched with ion channels and signaling molecules. The microdomains serve as key signaling hubs in regulation of cardiomyocyte function. Dyad microdomains formed at the junctional contact between t-tubule membrane and neighboring sarcoplasmic reticulum are critical in calcium signaling and excitation-contraction coupling necessary for beat-to-beat heart contraction. In this review, we provide an overview of the current knowledge in gross morphology and structure, membrane and protein composition, and function of the cardiac t-tubule network. We also review in detail current knowledge on the formation of functional membrane subdomains within t-tubules, with a particular focus on the cardiac dyad microdomain. Lastly, we discuss the dynamic nature of t-tubules including membrane turnover, trafficking of transmembrane proteins, and the life cycles of membrane subdomains such as the cardiac BIN1-microdomain, as well as t-tubule remodeling and alteration in diseased hearts. Understanding cardiac t-tubule biology in normal and failing hearts is providing novel diagnostic and therapeutic opportunities to better treat patients with failing hearts.
Collapse
Affiliation(s)
- TingTing Hong
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California; and Department of Medicine, University of California Los Angeles, Los Angeles, California
| | - Robin M Shaw
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California; and Department of Medicine, University of California Los Angeles, Los Angeles, California
| |
Collapse
|
12
|
Limbu B, Shah K, Weinberg SH, Deo M. Role of Cytosolic Calcium Diffusion in Murine Cardiac Purkinje Cells. CLINICAL MEDICINE INSIGHTS-CARDIOLOGY 2016; 10:17-26. [PMID: 27478391 PMCID: PMC4955978 DOI: 10.4137/cmc.s39705] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 06/12/2016] [Accepted: 06/25/2016] [Indexed: 11/24/2022]
Abstract
Cardiac Purkinje cells (PCs) are morphologically and electrophysiologically different from ventricular myocytes and, importantly, exhibit distinct calcium (Ca2+) homeostasis. Recent studies suggest that PCs are more susceptible to action potential (AP) abnormalities than ventricular myocytes; however, the exact mechanisms are poorly understood. In this study, we utilized a detailed biophysical mathematical model of a murine PC to systematically examine the role of cytosolic Ca2+ diffusion in shaping the AP in PCs. A biphasic spatiotemporal Ca2+ diffusion process, as recorded experimentally, was implemented in the model. In this study, we investigated the role of cytosolic Ca2+ dynamics on AP and ionic current properties by varying the effective Ca2+ diffusion rate. It was observed that AP morphology, specifically the plateau, was affected due to changes in the intracellular Ca2+ dynamics. Elevated Ca2+ concentration in the sarcolemmal region activated inward sodium–Ca2+ exchanger (NCX) current, resulting in a prolongation of the AP plateau at faster diffusion rates. Artificially clamping the NCX current to control values completely reversed the alterations in the AP plateau, thus confirming the role of NCX in modifying the AP morphology. Our results demonstrate that cytosolic Ca2+ diffusion waves play a significant role in shaping APs of PCs and could provide mechanistic insights in the increased arrhythmogeneity of PCs.
Collapse
Affiliation(s)
- Bijay Limbu
- Department of Engineering, Norfolk State University, Norfolk, VA, USA
| | - Kushal Shah
- Department of Engineering, Norfolk State University, Norfolk, VA, USA
| | - Seth H Weinberg
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, USA
| | - Makarand Deo
- Department of Engineering, Norfolk State University, Norfolk, VA, USA
| |
Collapse
|
13
|
Willis BC, Pandit SV, Ponce-Balbuena D, Zarzoso M, Guerrero-Serna G, Limbu B, Deo M, Camors E, Ramirez RJ, Mironov S, Herron TJ, Valdivia HH, Jalife J. Constitutive Intracellular Na+ Excess in Purkinje Cells Promotes Arrhythmogenesis at Lower Levels of Stress Than Ventricular Myocytes From Mice With Catecholaminergic Polymorphic Ventricular Tachycardia. Circulation 2016; 133:2348-59. [PMID: 27169737 PMCID: PMC4902321 DOI: 10.1161/circulationaha.116.021936] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2016] [Accepted: 05/03/2016] [Indexed: 11/18/2022]
Abstract
Supplemental Digital Content is available in the text. Background— In catecholaminergic polymorphic ventricular tachycardia (CPVT), cardiac Purkinje cells (PCs) appear more susceptible to Ca2+ dysfunction than ventricular myocytes (VMs). The underlying mechanisms remain unknown. Using a CPVT mouse (RyR2R4496C+/Cx40eGFP), we tested whether PC intracellular Ca2+ ([Ca2+]i) dysregulation results from a constitutive [Na+]i surplus relative to VMs. Methods and Results— Simultaneous optical mapping of voltage and [Ca2+]i in CPVT hearts showed that spontaneous Ca2+ release preceded pacing-induced triggered activity at subendocardial PCs. On simultaneous current-clamp and Ca2+ imaging, early and delayed afterdepolarizations trailed spontaneous Ca2+ release and were more frequent in CPVT PCs than CPVT VMs. As a result of increased activity of mutant ryanodine receptor type 2 channels, sarcoplasmic reticulum Ca2+ load, measured by caffeine-induced Ca2+ transients, was lower in CPVT VMs and PCs than respective controls, and sarcoplasmic reticulum fractional release was greater in both CPVT PCs and VMs than respective controls. [Na+]i was higher in both control and CPVT PCs than VMs, whereas the density of the Na+/Ca2+ exchanger current was not different between PCs and VMs. Computer simulations using a PC model predicted that the elevated [Na+]i of PCs promoted delayed afterdepolarizations, which were always preceded by spontaneous Ca2+ release events from hyperactive ryanodine receptor type 2 channels. Increasing [Na+]i monotonically increased delayed afterdepolarization frequency. Confocal imaging experiments showed that postpacing Ca2+ spark frequency was highest in intact CPVT PCs, but such differences were reversed on saponin-induced membrane permeabilization, indicating that differences in [Na+]i played a central role. Conclusions— In CPVT mice, the constitutive [Na+]i excess of PCs promotes triggered activity and arrhythmogenesis at lower levels of stress than VMs.
Collapse
Affiliation(s)
- B Cicero Willis
- From University of Michigan, Ann Arbor (B.C.W., S.V.P., D.P.-B., M.Z., G.G.-S., R.J.R., S.M., T.J.H., H.H.V., J.J.); Norfolk State University, VA (B.L., M.D.); University of Tennessee Health Science Center, Memphis (E.C.); and Fundación Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain (J.J.)
| | - Sandeep V Pandit
- From University of Michigan, Ann Arbor (B.C.W., S.V.P., D.P.-B., M.Z., G.G.-S., R.J.R., S.M., T.J.H., H.H.V., J.J.); Norfolk State University, VA (B.L., M.D.); University of Tennessee Health Science Center, Memphis (E.C.); and Fundación Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain (J.J.)
| | - Daniela Ponce-Balbuena
- From University of Michigan, Ann Arbor (B.C.W., S.V.P., D.P.-B., M.Z., G.G.-S., R.J.R., S.M., T.J.H., H.H.V., J.J.); Norfolk State University, VA (B.L., M.D.); University of Tennessee Health Science Center, Memphis (E.C.); and Fundación Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain (J.J.)
| | - Manuel Zarzoso
- From University of Michigan, Ann Arbor (B.C.W., S.V.P., D.P.-B., M.Z., G.G.-S., R.J.R., S.M., T.J.H., H.H.V., J.J.); Norfolk State University, VA (B.L., M.D.); University of Tennessee Health Science Center, Memphis (E.C.); and Fundación Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain (J.J.)
| | - Guadalupe Guerrero-Serna
- From University of Michigan, Ann Arbor (B.C.W., S.V.P., D.P.-B., M.Z., G.G.-S., R.J.R., S.M., T.J.H., H.H.V., J.J.); Norfolk State University, VA (B.L., M.D.); University of Tennessee Health Science Center, Memphis (E.C.); and Fundación Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain (J.J.)
| | - Bijay Limbu
- From University of Michigan, Ann Arbor (B.C.W., S.V.P., D.P.-B., M.Z., G.G.-S., R.J.R., S.M., T.J.H., H.H.V., J.J.); Norfolk State University, VA (B.L., M.D.); University of Tennessee Health Science Center, Memphis (E.C.); and Fundación Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain (J.J.)
| | - Makarand Deo
- From University of Michigan, Ann Arbor (B.C.W., S.V.P., D.P.-B., M.Z., G.G.-S., R.J.R., S.M., T.J.H., H.H.V., J.J.); Norfolk State University, VA (B.L., M.D.); University of Tennessee Health Science Center, Memphis (E.C.); and Fundación Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain (J.J.)
| | - Emmanuel Camors
- From University of Michigan, Ann Arbor (B.C.W., S.V.P., D.P.-B., M.Z., G.G.-S., R.J.R., S.M., T.J.H., H.H.V., J.J.); Norfolk State University, VA (B.L., M.D.); University of Tennessee Health Science Center, Memphis (E.C.); and Fundación Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain (J.J.)
| | - Rafael J Ramirez
- From University of Michigan, Ann Arbor (B.C.W., S.V.P., D.P.-B., M.Z., G.G.-S., R.J.R., S.M., T.J.H., H.H.V., J.J.); Norfolk State University, VA (B.L., M.D.); University of Tennessee Health Science Center, Memphis (E.C.); and Fundación Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain (J.J.)
| | - Sergey Mironov
- From University of Michigan, Ann Arbor (B.C.W., S.V.P., D.P.-B., M.Z., G.G.-S., R.J.R., S.M., T.J.H., H.H.V., J.J.); Norfolk State University, VA (B.L., M.D.); University of Tennessee Health Science Center, Memphis (E.C.); and Fundación Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain (J.J.)
| | - Todd J Herron
- From University of Michigan, Ann Arbor (B.C.W., S.V.P., D.P.-B., M.Z., G.G.-S., R.J.R., S.M., T.J.H., H.H.V., J.J.); Norfolk State University, VA (B.L., M.D.); University of Tennessee Health Science Center, Memphis (E.C.); and Fundación Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain (J.J.)
| | - Héctor H Valdivia
- From University of Michigan, Ann Arbor (B.C.W., S.V.P., D.P.-B., M.Z., G.G.-S., R.J.R., S.M., T.J.H., H.H.V., J.J.); Norfolk State University, VA (B.L., M.D.); University of Tennessee Health Science Center, Memphis (E.C.); and Fundación Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain (J.J.)
| | - José Jalife
- From University of Michigan, Ann Arbor (B.C.W., S.V.P., D.P.-B., M.Z., G.G.-S., R.J.R., S.M., T.J.H., H.H.V., J.J.); Norfolk State University, VA (B.L., M.D.); University of Tennessee Health Science Center, Memphis (E.C.); and Fundación Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain (J.J.).
| |
Collapse
|
14
|
Maass K, Shekhar A, Lu J, Kang G, See F, Kim EE, Delgado C, Shen S, Cohen L, Fishman GI. Isolation and characterization of embryonic stem cell-derived cardiac Purkinje cells. Stem Cells 2016; 33:1102-12. [PMID: 25524238 DOI: 10.1002/stem.1921] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Revised: 11/18/2014] [Accepted: 11/18/2014] [Indexed: 12/16/2022]
Abstract
The cardiac Purkinje fiber network is composed of highly specialized cardiomyocytes responsible for the synchronous excitation and contraction of the ventricles. Computational modeling, experimental animal studies, and intracardiac electrical recordings from patients with heritable and acquired forms of heart disease suggest that Purkinje cells (PCs) may also serve as critical triggers of life-threatening arrhythmias. Nonetheless, owing to the difficulty in isolating and studying this rare population of cells, the precise role of PC in arrhythmogenesis and the underlying molecular mechanisms responsible for their proarrhythmic behavior are not fully characterized. Conceptually, a stem cell-based model system might facilitate studies of PC-dependent arrhythmia mechanisms and serve as a platform to test novel therapeutics. Here, we describe the generation of murine embryonic stem cells (ESC) harboring pan-cardiomyocyte and PC-specific reporter genes. We demonstrate that the dual reporter gene strategy may be used to identify and isolate the rare ESC-derived PC (ESC-PC) from a mixed population of cardiogenic cells. ESC-PC display transcriptional signatures and functional properties, including action potentials, intracellular calcium cycling, and chronotropic behavior comparable to endogenous PC. Our results suggest that stem-cell derived PC are a feasible new platform for studies of developmental biology, disease pathogenesis, and screening for novel antiarrhythmic therapies.
Collapse
Affiliation(s)
- Karen Maass
- Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, New York, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Vigmond EJ, Stuyvers BD. Modeling our understanding of the His-Purkinje system. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2015; 120:179-88. [PMID: 26740015 DOI: 10.1016/j.pbiomolbio.2015.12.013] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 12/18/2015] [Accepted: 12/22/2015] [Indexed: 01/25/2023]
Abstract
The His-Purkinje System (HPS) is responsible for the rapid electric conduction in the ventricles. It relays electrical impulses from the atrioventricular node to the muscle cells and, thus, coordinates the contraction of ventricles in order to ensure proper cardiac pump function. The HPS has been implicated in the genesis of ventricular tachycardia and fibrillation as a source of ectopic beats, as well as forming distinct portions of reentry circuitry. Despite its importance, it remains much less well characterized, structurally and functionally, than the myocardium. Notably, important differences exist with regard to cell structure and electrophysiology, including ion channels, intracellular calcium handling, and gap junctions. Very few computational models address the HPS, and the majority of organ level modeling studies omit it. This review will provide an overview of our current knowledge of structure and function (including electrophysiology) of the HPS. We will review the most recent advances in modeling of the system from the single cell to the organ level, with considerations for relevant interspecies distinctions.
Collapse
Affiliation(s)
- Edward J Vigmond
- LIRYC, Institute of Electrophysiology and Cardiac Modeling, Hôpital Xavier Arnozan, avenue Haut-Lévèque, 33600 Pessac, France; Institut de Mathématiques de Bordeaux, Université de Bordeaux, 351, cours de la Libération, F 33 405 Talence, France; Department of Electrical and Computer Engineering, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada.
| | - Bruno D Stuyvers
- LIRYC, Institute of Electrophysiology and Cardiac Modeling, Hôpital Xavier Arnozan, avenue Haut-Lévèque, 33600 Pessac, France; Université de Bordeaux, 351, cours de la Libération, F 33 405 Talence, France; Faculty of Medicine, Memorial University of Newfoundland, 300 Prince Phillip Drive, St. John's, NL A1B 3V6, Canada.
| |
Collapse
|
16
|
Chen B, Zhang C, Guo A, Song LS. In situ single photon confocal imaging of cardiomyocyte T-tubule system from Langendorff-perfused hearts. Front Physiol 2015; 6:134. [PMID: 25999861 PMCID: PMC4422017 DOI: 10.3389/fphys.2015.00134] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 04/15/2015] [Indexed: 12/24/2022] Open
Abstract
Transverse tubules (T-tubules) are orderly invaginations of the sarcolemma in mammalian cardiomyocytes. The integrity of T-tubule architecture is critical for cardiac excitation–contraction coupling function. T-tubule remodeling is recognized as a key player in cardiac dysfunction. Early studies on T-tubule structure were based on electron microscopy, which uncovered important information about the T-tubule architecture. The advent of fluorescent membrane probes allowed the application of confocal microscopy to investigations of T-tubule structure. Studies have now been extended beyond single cardiomyocytes to examine the T-tubule network in intact hearts through in situ confocal imaging of Langendorff-perfused hearts. This technique has allowed visualization of T-tubule organization in their natural habitat, avoiding the damage induced by isolation of cardiomyocytes. Additionally, it is possible to obtain T-tubule images in different subepicardial regions in a single intact heart. We review how this state-of-the-art imaging technique has provided important mechanistic insights into maturation of T-tubules in developing hearts and defined the role of T-tubule remodeling in development and progression of heart failure.
Collapse
Affiliation(s)
- Biyi Chen
- Division of Cardiovascular Medicine, Department of Internal Medicine, Francois M. Abboud Cardiovascular Research Center, Carver College of Medicine, University of Iowa Iowa City, IA, USA
| | - Caimei Zhang
- Division of Cardiovascular Medicine, Department of Internal Medicine, Francois M. Abboud Cardiovascular Research Center, Carver College of Medicine, University of Iowa Iowa City, IA, USA
| | - Ang Guo
- Division of Cardiovascular Medicine, Department of Internal Medicine, Francois M. Abboud Cardiovascular Research Center, Carver College of Medicine, University of Iowa Iowa City, IA, USA
| | - Long-Sheng Song
- Division of Cardiovascular Medicine, Department of Internal Medicine, Francois M. Abboud Cardiovascular Research Center, Carver College of Medicine, University of Iowa Iowa City, IA, USA
| |
Collapse
|
17
|
Kim EE, Shekhar A, Lu J, Lin X, Liu FY, Zhang J, Delmar M, Fishman GI. PCP4 regulates Purkinje cell excitability and cardiac rhythmicity. J Clin Invest 2014; 124:5027-36. [PMID: 25295538 DOI: 10.1172/jci77495] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 09/04/2014] [Indexed: 11/17/2022] Open
Abstract
Cardiac Purkinje cells are important triggers of ventricular arrhythmias associated with heritable and acquired syndromes; however, the mechanisms responsible for this proarrhythmic behavior are incompletely understood. Here, through transcriptional profiling of genetically labeled cardiomyocytes, we identified expression of Purkinje cell protein-4 (Pcp4), a putative regulator of calmodulin and Ca2+/calmodulin-dependent kinase II (CaMKII) signaling, exclusively within the His-Purkinje network. Using Pcp4-null mice and acquired cardiomyopathy models, we determined that reduced expression of PCP4 is associated with CaMKII activation, abnormal electrophysiology, dysregulated intracellular calcium handling, and proarrhythmic behavior in isolated Purkinje cells. Pcp4-null mice also displayed profound autonomic dysregulation and arrhythmic behavior in vivo. Together, these results demonstrate that PCP4 regulates cardiac excitability through both Purkinje cell-autonomous and central mechanisms and identify this modulator of CaMKII signaling as a potential arrhythmia-susceptibility candidate.
Collapse
|
18
|
Haq KT, Daniels RE, Miller LS, Miura M, ter Keurs HEDJ, Bungay SD, Stuyvers BD. Evoked centripetal Ca(2+) mobilization in cardiac Purkinje cells: insight from a model of three Ca(2+) release regions. J Physiol 2013; 591:4301-19. [PMID: 23897231 DOI: 10.1113/jphysiol.2013.253583] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Despite strong suspicion that abnormal Ca(2+) handling in Purkinje cells (P-cells) is implicated in life-threatening forms of ventricular tachycardias, the mechanism underlying the Ca(2+) cycling of these cells under normal conditions is still unclear. There is mounting evidence that P-cells have a unique Ca(2+) handling system. Notably complex spontaneous Ca(2+) activity was previously recorded in canine P-cells and was explained by a mechanistic hypothesis involving a triple layered system of Ca(2+) release channels. Here we examined the validity of this hypothesis for the electrically evoked Ca(2+) transient which was shown, in the dog and rabbit, to occur progressively from the periphery to the interior of the cell. To do so, the hypothesis was incorporated in a model of intracellular Ca(2+) dynamics which was then used to reproduce numerically the Ca(2+) activity of P-cells under stimulated conditions. The modelling was thus performed through a 2D computational array that encompassed three distinct Ca(2+) release nodes arranged, respectively, into three consecutive adjacent regions. A system of partial differential equations (PDEs) expressed numerically the principal cellular functions that modulate the local cytosolic Ca(2+) concentration (Cai). The apparent node-to-node progression of elevated Cai was obtained by combining Ca(2+) diffusion and 'Ca(2+)-induced Ca(2+) release'. To provide the modelling with a reliable experimental reference, we first re-examined the Ca(2+) mobilization in swine stimulated P-cells by 2D confocal microscopy. As reported earlier for the dog and rabbit, a centripetal Ca(2+) transient was readily visible in 22 stimulated P-cells from six adult Yucatan swine hearts (pacing rate: 0.1 Hz; pulse duration: 25 ms, pulse amplitude: 10% above threshold; 1 mm Ca(2+); 35°C; pH 7.3). An accurate replication of the observed centripetal Ca(2+) propagation was generated by the model for four representative cell examples and confirmed by statistical comparisons of simulations against cell data. Selective inactivation of Ca(2+) release regions of the computational array showed that an intermediate layer of Ca(2+) release nodes with an ~30-40% lower Ca(2+) activation threshold was required to reproduce the phenomenon. Our computational analysis was therefore fully consistent with the activation of a triple layered system of Ca(2+) release channels as a mechanism of centripetal Ca(2+) signalling in P-cells. Moreover, the model clearly indicated that the intermediate Ca(2+) release layer with increased sensitivity for Ca(2+) plays an important role in the specific intracellular Ca(2+) mobilization of Purkinje fibres and could therefore be a relevant determinant of cardiac conduction.
Collapse
Affiliation(s)
- Kazi T Haq
- B. D. Stuyvers: Memorial University, Faculty of Medicine, Division of BioMedical Sciences, 300 Prince Phillip Bd, St John's, NL, A1B 3V6, Canada.
| | | | | | | | | | | | | |
Collapse
|
19
|
Long DY, Dong JZ, Sang CH, Jiang CX, Tang RB, Yan Q, Yu RH, Li SN, Yao Y, Ning M, Lin T, Salim M, Du X, Ma CS. Isolated Conduction Within the Left His-Purkenje System During Sinus Rhythm and Idiopathic Left Ventricle Tachycardia. Circ Arrhythm Electrophysiol 2013; 6:522-7. [PMID: 23673906 DOI: 10.1161/circep.113.000293] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- De-Yong Long
- From the Cardiology Department, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| | - Jian-Zeng Dong
- From the Cardiology Department, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| | - Cai-Hua Sang
- From the Cardiology Department, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| | - Chen-Xi Jiang
- From the Cardiology Department, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| | - Ri-Bo Tang
- From the Cardiology Department, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| | - Qian Yan
- From the Cardiology Department, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| | - Rong-Hui Yu
- From the Cardiology Department, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| | - Song-Nan Li
- From the Cardiology Department, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| | - Yan Yao
- From the Cardiology Department, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| | - Man Ning
- From the Cardiology Department, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| | - Tao Lin
- From the Cardiology Department, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| | - Mohamed Salim
- From the Cardiology Department, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| | - Xin Du
- From the Cardiology Department, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| | - Chang-Sheng Ma
- From the Cardiology Department, Beijing An Zhen Hospital, Capital Medical University, Beijing, China
| |
Collapse
|
20
|
Abstract
Ca(2+) waves were probably first observed in the early 1940s. Since then Ca(2+) waves have captured the attention of an eclectic mixture of mathematicians, neuroscientists, muscle physiologists, developmental biologists, and clinical cardiologists. This review discusses the current state of mathematical models of Ca(2+) waves, the normal physiological functions Ca(2+) waves might serve in cardiac cells, as well as how the spatial arrangement of Ca(2+) release channels shape Ca(2+) waves, and we introduce the idea of Ca(2+) phase waves that might provide a useful framework for understanding triggered arrhythmias.
Collapse
Affiliation(s)
- Leighton T Izu
- Department of Pharmacology, University of California, Davis, USA.
| | | | | | | | | |
Collapse
|
21
|
Guo A, Zhang C, Wei S, Chen B, Song LS. Emerging mechanisms of T-tubule remodelling in heart failure. Cardiovasc Res 2013; 98:204-15. [PMID: 23393229 DOI: 10.1093/cvr/cvt020] [Citation(s) in RCA: 125] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Cardiac excitation-contraction coupling occurs primarily at the sites of transverse (T)-tubule/sarcoplasmic reticulum junctions. The orderly T-tubule network guarantees the instantaneous excitation and synchronous activation of nearly all Ca(2+) release sites throughout the large ventricular myocyte. Because of the critical roles played by T-tubules and the array of channels and transporters localized to the T-tubule membrane network, T-tubule architecture has recently become an area of considerable research interest in the cardiovascular field. This review will focus on the current knowledge regarding normal T-tubule structure and function in the heart, T-tubule remodelling in the transition from compensated hypertrophy to heart failure, and the impact of T-tubule remodelling on myocyte Ca(2+) handling function. In the last section, we discuss the molecular mechanisms underlying T-tubule remodelling in heart disease.
Collapse
Affiliation(s)
- Ang Guo
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | | | | | | | | |
Collapse
|
22
|
ter Keurs HEDJ. The interaction of Ca2+ with sarcomeric proteins: role in function and dysfunction of the heart. Am J Physiol Heart Circ Physiol 2012; 302:H38-50. [PMID: 22021327 PMCID: PMC3334233 DOI: 10.1152/ajpheart.00219.2011] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Accepted: 10/11/2011] [Indexed: 12/28/2022]
Abstract
The hallmarks of the normal heartbeat are both rapid onset of contraction and rapid relaxation as well as an inotropic response to both increased end-diastolic volume and increased heart rate. At the microscopic level, Ca(2+) plays a crucial role in normal cardiac contraction. This paper reviews the cycle of Ca(2+) fluxes during the normal heartbeat, which underlie the coupling between excitation and contraction and permit a highly synchronized action of cardiac sarcomeres. Length dependence of the response of the regulatory sarcomeric proteins mediates the Frank-Starling Law of the heart. However, Ca(2+) transport may go astray in heart disease such as in congestive heart failure, and both jeopardize systole and diastole and triggering arrhythmias. The interaction between weak and strong segments in nonuniform cardiac muscle allows partial preservation of force of contraction but may further lead to mechanoelectric feedback or reverse excitation-contraction coupling mediating an early diastolic Ca(2+) transient caused by the rapid force decrease during the relaxation phase. These rapid force changes in nonuniform muscle may cause arrhythmogenic Ca(2+) waves to propagate by the activation of neighboring sarcoplasmic reticulum by diffusing Ca(2+) ions.
Collapse
|
23
|
Abstract
Calsequestrin is the most abundant Ca-binding protein of the specialized endoplasmic reticulum found in muscle, the sarcoplasmic reticulum (SR). Calsequestrin binds Ca with high capacity and low affinity and importantly contributes to the mobilization of Ca during each contraction both in skeletal and cardiac muscle. Surprisingly, mutations in the gene encoding the cardiac isoform of calsequestrin (Casq2) have been associated with an inherited form of ventricular arrhythmia triggered by emotional or physical stress termed catecholaminergic polymorphic ventricular tachycardia (CPVT). Despite normal cardiac contractility and normal resting ECG, CPVT patients present with a high risk of sudden death at a young age. Here, we review recent new insights regarding the role of calsequestrin in genetic and acquired arrhythmia disorders. Mouse models of CPVT have shed light on the pathophysiological mechanism underlying CPVT. Casq2 is not only a Ca-storing protein as initially hypothesized, but it has a far more complex function in Ca handling and regulating SR Ca release channels. The functional importance of Casq2 interactions with other SR proteins and the importance of alterations in Casq2 trafficking are also being investigated. Reports of altered Casq2 trafficking in animal models of acquired heart diseases such as heart failure suggest that Casq2 may contribute to arrhythmia risk beyond genetic forms of Casq2 dysfunction.
Collapse
Affiliation(s)
- Michela Faggioni
- Departments of Medicine and Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0575, USA
| | | |
Collapse
|
24
|
Bootman MD, Smyrnias I, Thul R, Coombes S, Roderick HL. Atrial cardiomyocyte calcium signalling. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:922-34. [DOI: 10.1016/j.bbamcr.2011.01.030] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Revised: 01/21/2011] [Accepted: 01/25/2011] [Indexed: 11/25/2022]
|
25
|
Electromechanical coupling in the cardiac myocyte; stretch-arrhythmia feedback. Pflugers Arch 2011; 462:165-75. [PMID: 21373861 DOI: 10.1007/s00424-011-0944-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Revised: 02/16/2011] [Accepted: 02/17/2011] [Indexed: 12/29/2022]
Abstract
The macroscopic hallmarks of the normal heartbeat are rapid onset of contraction and rapid relaxation and an inotropic response to both increased end diastolic volume and increased heart rate. At the microscopic level, the calcium ion (Ca(2+)) plays a crucial role in normal cardiac contraction. This paper reviews the cycle of Ca(2+) fluxes during the normal heartbeat, which underlie the coupling between excitation and contraction (ECC) and permit a highly synchronized action of cardiac sarcomeres. Length dependence of the response of the regulatory sarcomeric proteins mediates the Frank-Starling Law of the heart. However, Ca(2+) transport may go astray in heart disease and both jeopardize the exquisite mechanism of systole and diastole and triggering arrhythmias. The interplay between weakened and strong segments in nonuniform cardiac muscle may further lead to mechanoelectric feedback-or reverse excitation contraction coupling (RECC) mediating an early diastolic Ca(2+) transient caused by the rapid force decrease during the relaxation phase. These rapid force changes in nonuniform muscle may cause arrhythmogenic Ca(2+) waves to propagate by activation of neighbouring SR by diffusing Ca(2+) ions.
Collapse
|
26
|
Lee YS, Dun W, Boyden PA, Sobie EA. Complex and rate-dependent beat-to-beat variations in Ca2+ transients of canine Purkinje cells. J Mol Cell Cardiol 2011; 50:662-9. [PMID: 21232541 DOI: 10.1016/j.yjmcc.2010.12.023] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Revised: 12/09/2010] [Accepted: 12/31/2010] [Indexed: 11/29/2022]
Abstract
Purkinje fibers play an essential role in transmitting electrical impulses through the heart, but they may also serve as triggers for arrhythmias linked to defective intracellular calcium (Ca(2+)) regulation. Although prior studies have extensively characterized spontaneous Ca(2+) release in nondriven Purkinje cells, little attention has been paid to rate-dependent changes in Ca(2+) transients. Therefore we explored the behaviors of Ca(2+) transients at pacing rates ranging from 0.125 to 3 Hz in single canine Purkinje cells loaded with fluo3 and imaged with a confocal microscope. The experiments uncovered the following novel aspects of Ca(2+) regulation in Purkinje cells: 1) the cells exhibit a negative Ca(2+)-frequency relationship (at 2.5 Hz, Ca(2+) transient amplitude was 66 ± 6% smaller than that at 0.125 Hz); 2) sarcoplasmic reticulum (SR) Ca(2+) release occurs as a propagating wave at very low rates but is localized near the cell membrane at higher rates; 3) SR Ca(2+) load declines modestly (10 ± 5%) with an increase in pacing rate from 0.125 Hz to 2.5 Hz; 4) Ca(2+) transients show considerable beat-to-beat variability, with greater variability occurring at higher pacing rates. Analysis of beat-to-beat variability suggests that it can be accounted for by stochastic triggering of local Ca(2+) release events. Consistent with this hypothesis, an increase in triggering probability caused a decrease in the relative variability. These results offer new insight into how Ca(2+) release is normally regulated in Purkinje cells and provide clues regarding how disruptions in this regulation may lead to deleterious consequences such as arrhythmias.
Collapse
Affiliation(s)
- Young-Seon Lee
- Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, NY, USA
| | | | | | | |
Collapse
|
27
|
Kang G, Giovannone SF, Liu N, Liu FY, Zhang J, Priori SG, Fishman GI. Purkinje cells from RyR2 mutant mice are highly arrhythmogenic but responsive to targeted therapy. Circ Res 2010; 107:512-9. [PMID: 20595652 DOI: 10.1161/circresaha.110.221481] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
RATIONALE The Purkinje fiber network has been proposed as the source of arrhythmogenic Ca(2+) release events in catecholaminergic polymorphic ventricular tachycardia (CPVT), yet evidence supporting this mechanism at the cellular level is lacking. OBJECTIVE We sought to determine the frequency and severity of spontaneous Ca(2+) release events and the response to the antiarrhythmic agent flecainide in Purkinje cells and ventricular myocytes from RyR2(R4496C/+) CPVT mutant mice and littermate controls. METHODS AND RESULTS We crossed RyR2(R4496C/+) knock-in mice with the newly described Cntn2-EGFP BAC transgenic mice, which express a fluorescent reporter gene in cells of the cardiac conduction system, including the distal Purkinje fiber network. Isolated ventricular myocytes (EGFP(-)) and Purkinje cells (EGFP(+)) from wild-type hearts and mutant hearts were distinguished by epifluorescence and intracellular Ca(2+) dynamics recorded by microfluorimetry. Both wild-type and RyR2(R4496C/+) mutant Purkinje cells displayed significantly slower kinetics of activation and relaxation compared to ventricular myocytes of the same genotype, and tau(decay) in the mutant Purkinje cells was significantly slower than that observed in wild-type Purkinje cells. Of the 4 groups studied, RyR2(R4496C/+) mutant Purkinje cells were also most likely to develop spontaneous Ca(2+) release events, and the number of events per cell was also significantly greater. Furthermore, with isoproterenol treatment, although all 4 groups showed increases in the frequency of arrhythmogenic Ca(2+(i)) events, the RyR2(R4496C/+) Purkinje cells responded with the most profound abnormalities in intracellular Ca(2+) handling, including a significant increase in the frequency of unstimulated Ca(2+(i)) events and the development of alternans, as well as isolated and sustained runs of triggered beats. Both Purkinje cells and ventricular myocytes from wild-type mice showed suppression of spontaneous Ca(2+) release events with flecainide, whereas in RyR2(R4496C/+) mice, the Purkinje cells were preferentially responsive to drug. In contrast, the RyR2 blocker tetracaine was equally efficacious in mutant Purkinje cells and ventricular myocytes. CONCLUSIONS Purkinje cells display a greater propensity to develop abnormalities in intracellular Ca(2+) handling than ventricular myocytes. This proarrhythmic behavior is enhanced by disease-causing mutations in the RyR2 Ca(2+) release channel and greatly exacerbated by catecholaminergic stimulation, with the development of arrhythmogenic triggered beats. These data support the concept that Purkinje cells are critical contributors to arrhythmic triggers in animal models and humans with CPVT and suggest a broader role for the Purkinje fiber network in the genesis of ventricular arrhythmias.
Collapse
Affiliation(s)
- Guoxin Kang
- The Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, NY 10016, USA
| | | | | | | | | | | | | |
Collapse
|
28
|
There goes the neighborhood: pathological alterations in T-tubule morphology and consequences for cardiomyocyte Ca2+ handling. J Biomed Biotechnol 2010; 2010:503906. [PMID: 20396394 PMCID: PMC2852607 DOI: 10.1155/2010/503906] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2009] [Accepted: 01/15/2010] [Indexed: 12/19/2022] Open
Abstract
T-tubules are invaginations of the cardiomyocyte membrane into the cell interior which form a tortuous network. T-tubules provide proximity between the electrically excitable cell membrane and the sarcoplasmic reticulum, the main intracellular Ca2+ store. Tight coupling between the rapidly spreading action potential and Ca2+ release units in the SR membrane ensures synchronous Ca2+ release throughout the cardiomyocyte. This is a requirement for rapid and powerful contraction. In recent years, it has become clear that T-tubule structure and composition are altered in several pathological states which may importantly contribute to contractile defects in these conditions. In this review, we describe the “neighborhood” of proteins in the dyadic cleft which locally controls cardiomyocyte Ca2+ homeostasis and how alterations in T-tubule structure and composition may alter this neighborhood during heart failure, atrial fibrillation, and diabetic cardiomyopathy. Based on this evidence, we propose that T-tubules have the potential to serve as novel therapeutic targets.
Collapse
|
29
|
Omatsu-Kanbe M, Yamamoto T, Mori Y, Matsuura H. Self-beating atypically shaped cardiomyocytes survive a long-term postnatal development while preserving the expression of fetal cardiac genes in mice. J Histochem Cytochem 2010; 58:543-51. [PMID: 20197490 DOI: 10.1369/jhc.2010.955245] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The present study was designed to examine the postnatal developmental changes of atypically shaped cardiomyocytes (ACMs) prepared from the heart of newborn [postnatal day 1 (day-1)] through aged (12-month-old) mice. ACMs were identified as a novel type of self-beating cardiomyocyte with a peculiar morphology in mouse cardiac ventricles. The cell length of ACMs significantly increased during the first three postnatal months and further increased over the following 9 months. In contrast, the population of ACMs was significantly decreased within the first 5 weeks and reached a plateau in the adult stage. ACMs obtained from newborn and adult mice exhibited similar spontaneous action potentials. The expression of the fetal cardiac gene products atrial natriuretic peptide and voltage-gated T-type Ca(2+) channel Ca(V)3.2 was confirmed by immunostaining in ACMs obtained from both newborn and aged mice. These observations provide evidence that ACMs that exhibit spontaneous beating survive the long-term postnatal development of cardiac ventricles while preserving the expression of fetal cardiac genes. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.
Collapse
Affiliation(s)
- Mariko Omatsu-Kanbe
- Department of Physiology, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan.
| | | | | | | |
Collapse
|
30
|
Abstract
Purkinje cells are specialized for rapid propagation in the heart. Furthermore, Purkinje fibers as the source as well as the perpetuator of arrhythmias is a familiar finding. This is not surprising considering their location in the heart and their unique cell ultrastructure, cell electrophysiology, and mode of excitation-contraction coupling. This review touches on each of these points as we outline what is known today about Purkinje fibers/cells.
Collapse
|
31
|
Gelberg HB. Purkinje fiber dysplasia (histiocytoid cardiomyopathy) with ventricular noncompaction in a savannah kitten. Vet Pathol 2009; 46:693-7. [PMID: 19276060 DOI: 10.1354/vp.08-vp-0291-g-cr] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
In a 2-month-old female savannah kitten that died unexpectedly, the pathologic findings of significance were restricted to the heart and included abnormal Purkinje fibers and biventricular myocardial trabeculation or noncompaction. The Purkinje fibers were large, angular, and tightly packed. They contained few disorganized myofibrils among a rarified cytoplasm. The fibers were distinct from adjacent myocytes and were immunohistochemically positive for desmin, muscle actin, myoglobin, sarcomeric actin, and chromogranin A. These findings are identical to those that occur in children with histiocytoid cardiomyopathy, a fatal genetic mitochondrial disorder of Purkinje fibers. Ventricular noncompaction likely has a multifactoral cause that results from fetal arrest of ventricular organizational development that might occur in conjunction with, or independent of, histiocytoid cardiomyopathy.
Collapse
Affiliation(s)
- H B Gelberg
- Department of Biomedical Sciences and the Veterinary Diagnostic Laboratory, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331, USA.
| |
Collapse
|
32
|
Dun W, Boyden PA. The Purkinje cell; 2008 style. J Mol Cell Cardiol 2008; 45:617-24. [PMID: 18778712 DOI: 10.1016/j.yjmcc.2008.08.001] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2008] [Revised: 07/22/2008] [Accepted: 08/01/2008] [Indexed: 11/26/2022]
Abstract
Cardiac Purkinje fibers, due to their unique anatomical location, cell structure and electrophysiologic characteristics, play an important role in cardiac conduction and arrhythmogenesis. Purkinje cell action potentials are longer than their ventricular counterpart, and display two levels of resting potential. Purkinje cells provide for rapid propagation of the cardiac impulse to ventricular cells and have pacemaker and triggered activity, which differs from ventricular cells. Additionally, a unique intracellular Ca2+ release coordination has been revealed recently for the normal Purkinje cell. However, since the isolation of single Purkinje cells is difficult, particularly in small animals, research using Purkinje cells has been restricted. This review concentrates on comparison of Purkinje and ventricular cells in the morphology of the action potential, ionic channel function and molecular determinants by summarizing our present day knowledge of Purkinje cells.
Collapse
Affiliation(s)
- Wen Dun
- Department of Pharmacology, Center for Molecular Therapeutics, Columbia University, New York, NY, USA
| | | |
Collapse
|