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Regional Differences in Ca 2+ Signaling and Transverse-Tubules across Left Atrium from Adult Sheep. Int J Mol Sci 2023; 24:ijms24032347. [PMID: 36768669 PMCID: PMC9916916 DOI: 10.3390/ijms24032347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 01/18/2023] [Accepted: 01/19/2023] [Indexed: 01/27/2023] Open
Abstract
Cardiac excitation-contraction coupling can be different between regions of the heart. Little is known at the atria level, specifically in different regions of the left atrium. This is important given the role of cardiac myocytes from the pulmonary vein sleeves, which are responsible for ectopic activity during atrial fibrillation. In this study, we present a new method to isolate atrial cardiac myocytes from four different regions of the left atrium of a large animal model, sheep, highly relevant to humans. Using collagenase/protease we obtained calcium-tolerant atrial cardiac myocytes from the epicardium, endocardium, free wall and pulmonary vein regions. Calcium transients were slower (time to peak and time to decay) in free wall and pulmonary vein myocytes compared to the epicardium and endocardium. This is associated with lower t-tubule density. Overall, these results suggest regional differences in calcium transient and t-tubule density across left atria, which may play a major role in the genesis of atrial fibrillation.
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2
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Jin X, Amoni M, Gilbert G, Dries E, Doñate Puertas R, Tomar A, Nagaraju CK, Pradhan A, Yule DI, Martens T, Menten R, Vanden Berghe P, Rega F, Sipido K, Roderick HL. InsP 3R-RyR Ca 2+ channel crosstalk facilitates arrhythmias in the failing human ventricle. Basic Res Cardiol 2022; 117:60. [PMID: 36378362 DOI: 10.1007/s00395-022-00967-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 10/13/2022] [Accepted: 10/31/2022] [Indexed: 11/16/2022]
Abstract
Dysregulated intracellular Ca2+ handling involving altered Ca2+ release from intracellular stores via RyR channels underlies both arrhythmias and reduced function in heart failure (HF). Mechanisms linking RyR dysregulation and disease are not fully established. Studies in animals support a role for InsP3 receptor Ca2+ channels (InsP3R) in pathological alterations in cardiomyocyte Ca2+ handling but whether these findings translate to the divergent physiology of human cardiomyocytes during heart failure is not determined. Using electrophysiological and Ca2+ recordings in human ventricular cardiomyocytes, we uncovered that Ca2+ release via InsP3Rs facilitated Ca2+ release from RyR and induced arrhythmogenic delayed after depolarisations and action potentials. InsP3R-RyR crosstalk was particularly increased in HF at RyR clusters isolated from the T-tubular network. Reduced SERCA activity in HF further facilitated the action of InsP3. Nanoscale imaging revealed co-localisation of InsP3Rs with RyRs in the dyad, which was increased in HF, providing a mechanism for augmented Ca2+ channel crosstalk. Notably, arrhythmogenic activity dependent on InsP3Rs was increased in tissue wedges from failing hearts perfused with AngII to promote InsP3 generation. These data indicate a central role for InsP3R-RyR Ca2+ signalling crosstalk in the pro-arrhythmic action of GPCR agonists elevated in HF and the potential for their therapeutic targeting.
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Affiliation(s)
- Xin Jin
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium.,Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Matthew Amoni
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - Guillaume Gilbert
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - Eef Dries
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - Rosa Doñate Puertas
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - Ashutosh Tomar
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - Chandan K Nagaraju
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - Ankit Pradhan
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - David I Yule
- Department of Pharmacology and Physiology, Medical Center School of Medicine and Dentistry, University of Rochester, 601 Elmwood Avenue, Box 711, Rochester, NY, 14642, USA
| | - Tobie Martens
- Laboratory for Enteric NeuroScience (LENS), Translational Research Center for Gastrointestinal Disorders (TARGID), KU Leuven, 3000, Leuven, Belgium.,Cell and Tissue Imaging Cluster (CIC), KU Leuven, 3000, Leuven, Belgium
| | - Roxane Menten
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - Pieter Vanden Berghe
- Laboratory for Enteric NeuroScience (LENS), Translational Research Center for Gastrointestinal Disorders (TARGID), KU Leuven, 3000, Leuven, Belgium.,Cell and Tissue Imaging Cluster (CIC), KU Leuven, 3000, Leuven, Belgium
| | - Filip Rega
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium.,Department of Cardiology and Department of Cardiac Surgery, University Hospitals Leuven, Leuven, Belgium
| | - Karin Sipido
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium
| | - H Llewelyn Roderick
- Department of Cardiovascular Sciences, Laboratory of Experimental Cardiology, KU Leuven, 3000, Leuven, Belgium.
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3
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Shen X, van den Brink J, Bergan-Dahl A, Kolstad TR, Norden ES, Hou Y, Laasmaa M, Aguilar-Sanchez Y, Quick AP, Espe EKS, Sjaastad I, Wehrens XHT, Edwards AG, Soeller C, Louch WE. Prolonged β-adrenergic stimulation disperses ryanodine receptor clusters in cardiomyocytes. eLife 2022; 11:77725. [PMID: 35913125 PMCID: PMC9410709 DOI: 10.7554/elife.77725] [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: 02/15/2022] [Accepted: 07/31/2022] [Indexed: 11/17/2022] Open
Abstract
Ryanodine receptors (RyRs) exhibit dynamic arrangements in cardiomyocytes, and we previously showed that ‘dispersion’ of RyR clusters disrupts Ca2+ homeostasis during heart failure (HF) (Kolstad et al., eLife, 2018). Here, we investigated whether prolonged β-adrenergic stimulation, a hallmark of HF, promotes RyR cluster dispersion and examined the underlying mechanisms. We observed that treatment of healthy rat cardiomyocytes with isoproterenol for 1 hr triggered progressive fragmentation of RyR clusters. Pharmacological inhibition of Ca2+/calmodulin-dependent protein kinase II (CaMKII) reversed these effects, while cluster dispersion was reproduced by specific activation of CaMKII, and in mice with constitutively active Ser2814-RyR. A similar role of protein kinase A (PKA) in promoting RyR cluster fragmentation was established by employing PKA activation or inhibition. Progressive cluster dispersion was linked to declining Ca2+ spark fidelity and magnitude, and slowed release kinetics from Ca2+ propagation between more numerous RyR clusters. In healthy cells, this served to dampen the stimulatory actions of β-adrenergic stimulation over the longer term and protect against pro-arrhythmic Ca2+ waves. However, during HF, RyR dispersion was linked to impaired Ca2+ release. Thus, RyR localization and function are intimately linked via channel phosphorylation by both CaMKII and PKA, which, while finely tuned in healthy cardiomyocytes, underlies impaired cardiac function during pathology.
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Affiliation(s)
- Xin Shen
- Institute for Experimental Medical Research, Oslo University Hospital, Oslo, Norway
| | | | - Anna Bergan-Dahl
- Institute for Experimental Medical Research, Oslo University Hospital, Oslo, Norway
| | - Terje R Kolstad
- Insitute for Experimental Medical Research, Oslo University Hospital, Oslo, Norway
| | | | - Yufeng Hou
- KG Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway
| | - Martin Laasmaa
- Institute for Experimental Medical Research, Oslo University Hospital, Oslo, Norway
| | - Yuriana Aguilar-Sanchez
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, United States
| | - Ann Pepper Quick
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, United States
| | | | - Ivar Sjaastad
- Institute for Experimental Medical Research, Oslo University Hospital, Oslo, Norway
| | - Xander H T Wehrens
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, United States
| | | | | | - William Edward Louch
- Institute for Experimental Medical Research, Oslo University Hospital, Oslo, Norway
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4
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Setterberg IE, Le C, Frisk M, Li J, Louch WE. The Physiology and Pathophysiology of T-Tubules in the Heart. Front Physiol 2021; 12:718404. [PMID: 34566684 PMCID: PMC8458775 DOI: 10.3389/fphys.2021.718404] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 07/07/2021] [Indexed: 12/18/2022] Open
Abstract
In cardiomyocytes, invaginations of the sarcolemmal membrane called t-tubules are critically important for triggering contraction by excitation-contraction (EC) coupling. These structures form functional junctions with the sarcoplasmic reticulum (SR), and thereby enable close contact between L-type Ca2+ channels (LTCCs) and Ryanodine Receptors (RyRs). This arrangement in turn ensures efficient triggering of Ca2+ release, and contraction. While new data indicate that t-tubules are capable of exhibiting compensatory remodeling, they are also widely reported to be structurally and functionally compromised during disease, resulting in disrupted Ca2+ homeostasis, impaired systolic and/or diastolic function, and arrhythmogenesis. This review summarizes these findings, while highlighting an emerging appreciation of the distinct roles of t-tubules in the pathophysiology of heart failure with reduced and preserved ejection fraction (HFrEF and HFpEF). In this context, we review current understanding of the processes underlying t-tubule growth, maintenance, and degradation, underscoring the involvement of a variety of regulatory proteins, including junctophilin-2 (JPH2), amphiphysin-2 (BIN1), caveolin-3 (Cav3), and newer candidate proteins. Upstream regulation of t-tubule structure/function by cardiac workload and specifically ventricular wall stress is also discussed, alongside perspectives for novel strategies which may therapeutically target these mechanisms.
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Affiliation(s)
- Ingunn E Setterberg
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway
| | - Christopher Le
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway
| | - Michael Frisk
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway
| | - Jia Li
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway
| | - William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway
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5
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Jones PP, MacQuaide N, Louch WE. Dyadic Plasticity in Cardiomyocytes. Front Physiol 2018; 9:1773. [PMID: 30618792 PMCID: PMC6298195 DOI: 10.3389/fphys.2018.01773] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 11/23/2018] [Indexed: 11/13/2022] Open
Abstract
Contraction of cardiomyocytes is dependent on sub-cellular structures called dyads, where invaginations of the surface membrane (t-tubules) form functional junctions with the sarcoplasmic reticulum (SR). Within each dyad, Ca2+ entry through t-tubular L-type Ca2+ channels (LTCCs) elicits Ca2+ release from closely apposed Ryanodine Receptors (RyRs) in the SR membrane. The efficiency of this process is dependent on the density and macroscale arrangement of dyads, but also on the nanoscale organization of LTCCs and RyRs within them. We presently review accumulating data demonstrating the remarkable plasticity of these structures. Dyads are known to form gradually during development, with progressive assembly of both t-tubules and junctional SR terminals, and precise trafficking of LTCCs and RyRs. While dyads can exhibit compensatory remodeling when required, dyadic degradation is believed to promote impaired contractility and arrythmogenesis in cardiac disease. Recent data indicate that this plasticity of dyadic structure/function is dependent on the regulatory proteins junctophilin-2, amphiphysin-2 (BIN1), and caveolin-3, which critically arrange dyadic membranes while stabilizing the position and activity of LTCCs and RyRs. Indeed, emerging evidence indicates that clustering of both channels enables "coupled gating", implying that nanoscale localization and function are intimately linked, and may allow fine-tuning of LTCC-RyR crosstalk. We anticipate that improved understanding of dyadic plasticity will provide greater insight into the processes of cardiac compensation and decompensation, and new opportunities to target the basic mechanisms underlying heart disease.
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Affiliation(s)
- Peter P. Jones
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
- HeartOtago, University of Otago, Dunedin, New Zealand
| | - Niall MacQuaide
- Institute of Cardiovascular Sciences, University of Glasgow, Glasgow, United Kingdom
- Clyde Biosciences, Glasgow, United Kingdom
| | - William E. Louch
- Institute for Experimental Medical Research, Oslo University Hospital, University of Oslo, Oslo, Norway
- KG Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
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6
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Scardigli M, Ferrantini C, Crocini C, Pavone FS, Sacconi L. Interplay Between Sub-Cellular Alterations of Calcium Release and T-Tubular Defects in Cardiac Diseases. Front Physiol 2018; 9:1474. [PMID: 30410446 PMCID: PMC6209824 DOI: 10.3389/fphys.2018.01474] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 09/28/2018] [Indexed: 12/19/2022] Open
Abstract
Asynchronous Ca2+ release promotes non-homogeneous myofilament activation, leading to mechanical dysfunction, as well as initiation of propagated calcium waves and arrhythmias. Recent advances in microscopy techniques have allowed for optical recordings of local Ca2+ fluxes and action potentials from multiple sub-cellular domains within cardiac cells with unprecedented spatial and temporal resolution. Since then, sub-cellular local information of the spatio-temporal relationship between Ca2+ release and action potential propagation have been unlocked, providing novel mechanistic insights in cardiac excitation-contraction coupling (ECC). Here, we review the promising perspectives arouse from repeatedly probing Ca2+ release at the same sub-cellular location while simultaneously probing multiple locations at the same time within a single cardiac cell. We also compare the results obtained in three different rodent models of cardiac diseases, highlighting disease-specific mechanisms. Slower local Ca2+ release has been observed in regions with defective action potential conduction in diseased cardiac cells. Moreover, significant increment of Ca2+ variability (both in time and in space) has been found in diseased cardiac cells but does not directly correlate with local electrical defects nor with the degree of structural aberrations of the cellular membrane system, suggesting a role for other players of the ECC machinery. We finally explore exciting opportunities provided by the technology for studying different cardiomyocyte populations, as well as for dissecting the mechanisms responsible for subcellular spatio-temporal variability of Ca2+ release.
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Affiliation(s)
- Marina Scardigli
- National Institute of Optics, National Research Council, Florence, Italy.,European Laboratory for Non-Linear Spectroscopy, Florence, Italy
| | - Cecilia Ferrantini
- European Laboratory for Non-Linear Spectroscopy, Florence, Italy.,Division of Physiology, Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy
| | - Claudia Crocini
- Department of Molecular, Cellular, and Developmental Biology & BioFrontiers Institute, University of Colorado Boulder, Boulder, CO, United States
| | - Francesco S Pavone
- National Institute of Optics, National Research Council, Florence, Italy.,European Laboratory for Non-Linear Spectroscopy, Florence, Italy.,Department of Physics and Astronomy, University of Florence, Florence, Italy
| | - Leonardo Sacconi
- National Institute of Optics, National Research Council, Florence, Italy.,European Laboratory for Non-Linear Spectroscopy, Florence, Italy
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7
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Abstract
PURPOSE OF REVIEW Membrane invaginations called t-tubules play an integral role in triggering cardiomyocyte contraction, and their disruption during diseases such as heart failure critically impairs cardiac performance. In this review, we outline the growing understanding of the malleability of t-tubule structure and function, and highlight emerging t-tubule regulators which may be exploited for novel therapies. RECENT FINDINGS New technologies are revealing the nanometer scale organization of t-tubules, and their functional junctions with the sarcoplasmic reticulum called dyads, which generate Ca2+ sparks. Recent data have indicated that the dyadic anchoring protein junctophilin-2, and the membrane-bending protein BIN1 are key regulators of dyadic formation and maintenance. While the underlying signals which control expression and localization of these proteins remain unclear, accumulating data support an important role of myocardial workload. Although t-tubule alterations are believed to be a key cause of heart failure, the plasticity of these structures also creates an opportunity for therapy. Promising recent data suggest that such therapies may specifically target junctophilin-2, BIN1, and/or mechanotransduction.
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8
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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 2017; 114:288-299. [PMID: 29217432 DOI: 10.1016/j.yjmcc.2017.12.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [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.
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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.
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9
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Seidel T, Sankarankutty AC, Sachse FB. Remodeling of the transverse tubular system after myocardial infarction in rabbit correlates with local fibrosis: A potential role of biomechanics. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017; 130:302-314. [PMID: 28709857 DOI: 10.1016/j.pbiomolbio.2017.07.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 07/07/2017] [Accepted: 07/10/2017] [Indexed: 02/03/2023]
Abstract
The transverse tubular system (t-system) of ventricular cardiomyocytes is essential for efficient excitation-contraction coupling. In cardiac diseases, such as heart failure, remodeling of the t-system contributes to reduced cardiac contractility. However, mechanisms of t-system remodeling are incompletely understood. Prior studies suggested an association with altered cardiac biomechanics and gene expression in disease. Since fibrosis may alter tissue biomechanics, we investigated the local microscopic association of t-system remodeling with fibrosis in a rabbit model of myocardial infarction (MI). Biopsies were taken from the MI border zone of 6 infarcted hearts and from 6 control hearts. Using confocal microscopy and automated image analysis, we quantified t-system integrity (ITT) and the local fraction of extracellular matrix (fECM). In control, fECM was 18 ± 0.3%. ITT was high and homogeneous (0.07 ± 0.006), and did not correlate with fECM (R2 = 0.05 ± 0.02). The MI border zone exhibited increased fECM within 3 mm from the infarct scar (30 ± 3.5%, p < 0.01 vs control), indicating fibrosis. Myocytes in the MI border zone exhibited significant t-system remodeling, with dilated, sheet-like components, resulting in low ITT (0.03 ± 0.008, p < 0.001 vs control). While both fECM and t-system remodeling decreased with infarct distance, ITT correlated better with decreasing fECM (R2 = 0.44) than with infarct distance (R2 = 0.24, p < 0.05). Our results show that t-system remodeling in the rabbit MI border zone resembles a phenotype previously described in human heart failure. T-system remodeling correlated with the amount of local fibrosis, which is known to stiffen cardiac tissue, but was not found in regions without fibrosis. Thus, locally altered tissue mechanics may contribute to t-system remodeling.
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Affiliation(s)
- T Seidel
- Institute for Cellular and Molecular Physiology, University of Erlangen-Nuremberg, Erlangen, Germany; Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, USA.
| | - A C Sankarankutty
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, USA; Department of Bioengineering, University of Utah, Salt Lake City, USA
| | - F B Sachse
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, USA; Department of Bioengineering, University of Utah, Salt Lake City, USA.
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10
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Gadeberg HC, Bond RC, Kong CHT, Chanoit GP, Ascione R, Cannell MB, James AF. Heterogeneity of T-Tubules in Pig Hearts. PLoS One 2016; 11:e0156862. [PMID: 27281038 PMCID: PMC4900646 DOI: 10.1371/journal.pone.0156862] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2014] [Accepted: 04/30/2016] [Indexed: 12/15/2022] Open
Abstract
Background T-tubules are invaginations of the sarcolemma that play a key role in excitation-contraction coupling in mammalian cardiac myocytes. Although t-tubules were generally considered to be effectively absent in atrial myocytes, recent studies on atrial cells from larger mammals suggest that t-tubules may be more numerous than previously supposed. However, the degree of heterogeneity between cardiomyocytes in the extent of the t-tubule network remains unclear. The aim of the present study was to investigate the t-tubule network of pig atrial myocytes in comparison with ventricular tissue. Methods Cardiac tissue was obtained from young female Landrace White pigs (45–75 kg, 5–6 months old). Cardiomyocytes were isolated by arterial perfusion with a collagenase-containing solution. Ca2+ transients were examined in field-stimulated isolated cells loaded with fluo-4-AM. Membranes of isolated cells were visualized using di-8-ANEPPS. T-tubules were visualized in fixed-frozen tissue sections stained with Alexa-Fluor 488-conjugated WGA. Binary images were obtained by application of a threshold and t-tubule density (TTD) calculated. A distance mapping approach was used to calculate half-distance to nearest t-tubule (HDTT). Results & Conclusion The spatio-temporal properties of the Ca2+ transient appeared to be consistent with the absence of functional t-tubules in isolated atrial myocytes. However, t-tubules could be identified in a sub-population of atrial cells in frozen sections. While all ventricular myocytes had TTD >3% (mean TTD = 6.94±0.395%, n = 24), this was true of just 5/22 atrial cells. Mean atrial TTD (2.35±0.457%, n = 22) was lower than ventricular TTD (P<0.0001). TTD correlated with cell-width (r = 0.7756, n = 46, P<0.0001). HDTT was significantly greater in the atrial cells with TTD ≤3% (2.29±0.16 μm, n = 17) than in either ventricular cells (1.33±0.05 μm, n = 24, P<0.0001) or in atrial cells with TTD >3% (1.65±0.06 μm, n = 5, P<0.05). These data demonstrate considerable heterogeneity between pig cardiomyocytes in the extent of t-tubule network, which correlated with cell size.
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Affiliation(s)
- Hanne C. Gadeberg
- Cardiovascular Research Laboratories, Bristol Cardiovascular, School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, BS8 1TD, United Kingdom
| | - Richard C. Bond
- Cardiovascular Research Laboratories, Bristol Cardiovascular, School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, BS8 1TD, United Kingdom
| | - Cherrie H. T. Kong
- Cardiovascular Research Laboratories, Bristol Cardiovascular, School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, BS8 1TD, United Kingdom
| | - Guillaume P. Chanoit
- School of Veterinary Sciences, University of Bristol, Langford House, Langford, BS40 5DU, United Kingdom
| | - Raimondo Ascione
- School of Clinical Sciences, University of Bristol, Bristol Royal Infirmary, Upper Maudlin Street, Bristol, BS2 8HW, United Kingdom
| | - Mark B. Cannell
- Cardiovascular Research Laboratories, Bristol Cardiovascular, School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, BS8 1TD, United Kingdom
- * E-mail: (AFJ); (MBC)
| | - Andrew F. James
- Cardiovascular Research Laboratories, Bristol Cardiovascular, School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, BS8 1TD, United Kingdom
- * E-mail: (AFJ); (MBC)
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11
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Sikkel MB, Kumar S, Maioli V, Rowlands C, Gordon F, Harding SE, Lyon AR, MacLeod KT, Dunsby C. High speed sCMOS-based oblique plane microscopy applied to the study of calcium dynamics in cardiac myocytes. JOURNAL OF BIOPHOTONICS 2016; 9:311-23. [PMID: 26488431 PMCID: PMC4874460 DOI: 10.1002/jbio.201500193] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 08/28/2015] [Accepted: 09/16/2015] [Indexed: 05/18/2023]
Abstract
Oblique plane microscopy (OPM) is a form of light sheet microscopy that uses a single high numerical aperture microscope objective for both fluorescence excitation and collection. In this paper, measurements of the relative collection efficiency of OPM are presented. An OPM system incorporating two sCMOS cameras is then introduced that enables single isolated cardiac myocytes to be studied continuously for 22 seconds in two dimensions at 667 frames per second with 960 × 200 pixels and for 30 seconds with 960 × 200 × 20 voxels at 25 volumes per second. In both cases OPM is able to record in two spectral channels, enabling intracellular calcium to be studied via the probe Fluo-4 AM simultaneously with the sarcolemma and transverse tubule network via the membrane dye Cellmask Orange. The OPM system was then applied to determine the spatial origin of spontaneous calcium waves for the first time and to measure the cell transverse tubule structure at their point of origin. Further results are presented to demonstrate that the OPM system can also be used to study calcium spark parameters depending on their relationship to the transverse tubule structure.
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Affiliation(s)
- Markus B Sikkel
- Myocardial Function Section, National Heart and Lung Institute, Imperial College, London, United Kingdom
| | - Sunil Kumar
- Photonics Group, Department of Physics, Imperial College London, London, United Kingdom
| | - Vincent Maioli
- Photonics Group, Department of Physics, Imperial College London, London, United Kingdom.
| | - Christina Rowlands
- Myocardial Function Section, National Heart and Lung Institute, Imperial College, London, United Kingdom
| | - Fabiana Gordon
- Statistics Advisory Service, Imperial College London, London, United Kingdom
| | - Sian E Harding
- Myocardial Function Section, National Heart and Lung Institute, Imperial College, London, United Kingdom
| | - Alexander R Lyon
- Myocardial Function Section, National Heart and Lung Institute, Imperial College, London, United Kingdom
- NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, London, United Kingdom
| | - Kenneth T MacLeod
- Myocardial Function Section, National Heart and Lung Institute, Imperial College, London, United Kingdom
| | - Chris Dunsby
- Photonics Group, Department of Physics, Imperial College London, London, United Kingdom
- Centre for Pathology, Department of Medicine, Imperial College London, United Kingdom
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12
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Gadeberg HC, Bryant SM, James AF, Orchard CH. Altered Na/Ca exchange distribution in ventricular myocytes from failing hearts. Am J Physiol Heart Circ Physiol 2015; 310:H262-8. [PMID: 26566728 PMCID: PMC4796630 DOI: 10.1152/ajpheart.00597.2015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 11/11/2015] [Indexed: 11/22/2022]
Abstract
In mammalian cardiac ventricular myocytes, Ca efflux via Na/Ca exchange (NCX) occurs predominantly at T tubules. Heart failure is associated with disrupted t-tubular structure, but its effect on t-tubular function is less clear. We therefore investigated t-tubular NCX activity in ventricular myocytes isolated from rat hearts ∼18 wk after coronary artery ligation (CAL) or corresponding sham operation (Sham). NCX current (INCX) and l-type Ca current (ICa) were recorded using the whole cell, voltage-clamp technique in intact and detubulated (DT) myocytes; intracellular free Ca concentration ([Ca]i) was monitored simultaneously using fluo-4. INCX was activated and measured during application of caffeine to release Ca from sarcoplasmic reticulum (SR). Whole cell INCX was not significantly different in Sham and CAL myocytes and occurred predominantly in the T tubules in Sham myocytes. CAL was associated with redistribution of INCX and ICa away from the T tubules to the cell surface and an increase in t-tubular INCX/ICa density from 0.12 in Sham to 0.30 in CAL myocytes. The decrease in t-tubular INCX in CAL myocytes was accompanied by an increase in the fraction of Ca sequestered by SR. However, SR Ca content was not significantly different in Sham, Sham DT, and CAL myocytes but was significantly increased by DT of CAL myocytes. In Sham myocytes, there was hysteresis between INCX and [Ca]i, which was absent in DT Sham but present in CAL and DT CAL myocytes. These data suggest altered distribution of NCX in CAL myocytes.
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Affiliation(s)
- Hanne C Gadeberg
- School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Simon M Bryant
- School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Andrew F James
- School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Clive H Orchard
- School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol, United Kingdom
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13
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14
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Nivala M, Song Z, Weiss JN, Qu Z. T-tubule disruption promotes calcium alternans in failing ventricular myocytes: mechanistic insights from computational modeling. J Mol Cell Cardiol 2014; 79:32-41. [PMID: 25450613 DOI: 10.1016/j.yjmcc.2014.10.018] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 10/25/2014] [Accepted: 10/28/2014] [Indexed: 10/24/2022]
Abstract
In heart failure (HF), T-tubule (TT) disruption contributes to dyssynchronous calcium (Ca) release and impaired contraction, but its role in arrhythmogenesis remains unclear. In this study, we investigate the effects of TT disruption and other HF remodeling factors on Ca alternans in ventricular myocytes using computer modeling. A ventricular myocyte model with detailed spatiotemporal Ca cycling modeled by a coupled Ca release unit (CRU) network was used, in which the L-type Ca channels and the ryanodine receptor (RyR) channels were simulated by random Markov transitions. TT disruption, which removes the L-type Ca channels from the associated CRUs, results in "orphaned" RyR clusters and thus provides increased opportunity for spark-induced Ca sparks to occur. This effect combined with other HF remodeling factors promoted alternans by two distinct mechanisms: 1) for normal sarco-endoplasmic reticulum Ca ATPase (SERCA) activity, alternans was caused by both CRU refractoriness and coupling. The increased opportunity for spark-induced sparks by TT disruption combined with the enhanced CRU coupling by Ca elevation in the presence or absence of increased RyR leakiness facilitated spark synchronization on alternate beats to promote Ca alternans; 2) for down-regulated SERCA, alternans was caused by the sarcoplasmic reticulum (SR) Ca load-dependent mechanism, independent of CRU refractoriness. TT disruption and increased RyR leakiness shifted and steepened the SR Ca release-load relationship, which combines with down-regulated SERCA to promote Ca alternans. In conclusion, the mechanisms of Ca alternans for normal and down-regulated SERCA are different, and TT disruption promotes Ca alternans by both mechanisms, which may contribute to alternans at different stages of HF.
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Affiliation(s)
- Michael Nivala
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - Zhen Song
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - James N Weiss
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - Zhilin Qu
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
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15
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Crocini C, Coppini R, Ferrantini C, Pavone FS, Sacconi L. Functional cardiac imaging by random access microscopy. Front Physiol 2014; 5:403. [PMID: 25368580 PMCID: PMC4202699 DOI: 10.3389/fphys.2014.00403] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 09/29/2014] [Indexed: 11/22/2022] Open
Abstract
Advances in the development of voltage sensitive dyes and Ca2+ sensors in combination with innovative microscopy techniques allowed researchers to perform functional measurements with an unprecedented spatial and temporal resolution. At the moment, one of the shortcomings of available technologies is their incapability of imaging multiple fast phenomena while controlling the biological determinants involved. In the near future, ultrafast deflectors can be used to rapidly scan laser beams across the sample, performing optical measurements of action potential and Ca2+ release from multiple sites within cardiac cells and tissues. The same scanning modality could also be used to control local Ca2+ release and membrane electrical activity by activation of caged compounds and light-gated ion channels. With this approach, local Ca2+ or voltage perturbations could be induced, simulating arrhythmogenic events, and their impact on physiological cell activity could be explored. The development of this optical methodology will provide fundamental insights in cardiac disease, boosting new therapeutic strategies, and, more generally, it will represent a new approach for the investigation of the physiology of excitable cells.
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Affiliation(s)
- Claudia Crocini
- European Laboratory for Non-Linear Spectroscopy (LENS) Florence, Italy
| | - Raffaele Coppini
- Division of Pharmacology, Department "NeuroFarBa," University of Florence Florence, Italy
| | - Cecilia Ferrantini
- Division of Physiology, Department of Experimental and Clinical Medicine, University of Florence Florence, Italy
| | - Francesco S Pavone
- European Laboratory for Non-Linear Spectroscopy (LENS) Florence, Italy ; Department of Physics and Astronomy, University of Florence Sesto Fiorentino, Italy ; National Research Council, National Institute of Optics Florence, Italy
| | - Leonardo Sacconi
- European Laboratory for Non-Linear Spectroscopy (LENS) Florence, Italy ; National Research Council, National Institute of Optics Florence, Italy
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16
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Frisk M, Koivumäki JT, Norseng PA, Maleckar MM, Sejersted OM, Louch WE. Variable t-tubule organization and Ca2+ homeostasis across the atria. Am J Physiol Heart Circ Physiol 2014; 307:H609-20. [PMID: 24951751 DOI: 10.1152/ajpheart.00295.2014] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Although t-tubules have traditionally been thought to be absent in atrial cardiomyocytes, recent studies have suggested that t-tubules exist in the atria of large mammals. However, it is unclear whether regional differences in t-tubule organization exist that define cardiomyocyte function across the atria. We sought to investigate regional t-tubule density in pig and rat atria and the consequences for cardiomyocyte Ca(2+) homeostasis. We observed t-tubules in approximately one-third of rat atrial cardiomyocytes, in both tissue cryosections and isolated cardiomyocytes. In a minority (≈10%) of atrial cardiomyocytes, the t-tubular network was well organized, with a transverse structure resembling that of ventricular cardiomyocytes. In both rat and pig atrial tissue, we observed higher t-tubule density in the epicardium than in the endocardium. Consistent with high variability in the distribution of t-tubules and Ca(2+) channels among cells, L-type Ca(2+) current amplitude was also highly variable and steeply dependent on capacitance and t-tubule density. Accordingly, Ca(2+) transients showed great variability in Ca(2+) release synchrony. Simultaneous imaging of the cell membrane and Ca(2+) transients confirmed t-tubule functionality. Results from mathematical modeling indicated that a transmural gradient in t-tubule organization and Ca(2+) release kinetics supports synchronization of contraction across the atrial wall and may underlie transmural differences in the refractory period. In conclusion, our results indicate that t-tubule density is highly variable across the atria. We propose that higher t-tubule density in cells localized in the epicardium may promote synchronization of contraction across the atrial wall.
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Affiliation(s)
- Michael Frisk
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway;
| | - Jussi T Koivumäki
- Center for Biomedical Computing, Simula Research Laboratory, Oslo, Norway; and Center for Cardiological Innovation, Oslo University Hospital, Oslo, Norway
| | - Per A Norseng
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Mary M Maleckar
- Center for Biomedical Computing, Simula Research Laboratory, Oslo, Norway; and Center for Cardiological Innovation, Oslo University Hospital, Oslo, Norway
| | - Ole M Sejersted
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
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