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Kohl P, Greiner J, Rog-Zielinska EA. Electron microscopy of cardiac 3D nanodynamics: form, function, future. Nat Rev Cardiol 2022; 19:607-619. [PMID: 35396547 DOI: 10.1038/s41569-022-00677-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/04/2022] [Indexed: 11/09/2022]
Abstract
The 3D nanostructure of the heart, its dynamic deformation during cycles of contraction and relaxation, and the effects of this deformation on cell function remain largely uncharted territory. Over the past decade, the first inroads have been made towards 3D reconstruction of heart cells, with a native resolution of around 1 nm3, and of individual molecules relevant to heart function at a near-atomic scale. These advances have provided access to a new generation of data and have driven the development of increasingly smart, artificial intelligence-based, deep-learning image-analysis algorithms. By high-pressure freezing of cardiomyocytes with millisecond accuracy after initiation of an action potential, pseudodynamic snapshots of contraction-induced deformation of intracellular organelles can now be captured. In combination with functional studies, such as fluorescence imaging, exciting insights into cardiac autoregulatory processes at nano-to-micro scales are starting to emerge. In this Review, we discuss the progress in this fascinating new field to highlight the fundamental scientific insight that has emerged, based on technological breakthroughs in biological sample preparation, 3D imaging and data analysis; to illustrate the potential clinical relevance of understanding 3D cardiac nanodynamics; and to predict further progress that we can reasonably expect to see over the next 10 years.
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Affiliation(s)
- Peter Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany.,Faculty of Engineering, University of Freiburg, Freiburg, Germany.,Centre for Integrative Biological Signalling Studies (CIBSS), University of Freiburg, Freiburg, Germany
| | - Joachim Greiner
- Institute for Experimental Cardiovascular Medicine, University Heart Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Eva A Rog-Zielinska
- Institute for Experimental Cardiovascular Medicine, University Heart Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany.
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2
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Ma J, Gao X, Li Y, DeCoursey TE, Shull GE, Wang HS. The HVCN1 voltage-gated proton channel contributes to pH regulation in canine ventricular myocytes. J Physiol 2022; 600:2089-2103. [PMID: 35244217 PMCID: PMC9058222 DOI: 10.1113/jp282126] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 02/24/2022] [Indexed: 11/09/2022] Open
Abstract
KEY POINTS Intracellular pH (pHi ) regulation is crucial for cardiac function, as acidification depresses contractility and causes arrhythmias. H+ ions are generated in cardiomyocytes from metabolic processes and particularly from CO2 hydration, which has been shown to facilitate CO2 -venting from mitochondria. Currently, the NHE1 Na+ /H+ exchanger is viewed as the dominant H+ -extrusion mechanism in cardiac muscle. We show that the HVCN1 voltage-gated proton channel is present and functional in canine ventricular myocytes, and that HVCN1 and NHE1 both contribute to pHi regulation. HVCN1 provides an energetically-efficient mechanism of H+ -extrusion that would not cause Na+ -loading, which can cause pathology, and that could contribute to transport-mediated CO2 disposal. These results provide a major advance in our understanding of pHi regulation in cardiac muscle. ABSTRACT Regulation of intracellular pH (pHi ) in cardiomyocytes is crucial for cardiac function; however, currently known mechanisms for direct or indirect extrusion of acid from cardiomyocytes seem insufficient for energetically-efficient extrusion of the massive H+ loads generated under in vivo conditions. In cardiomyocytes, voltage-sensitive H+ channel activity mediated by the HVCN1 proton channel would be a highly efficient means of disposing of H+ , while avoiding Na+ -loading, as occurs during direct acid extrusion via Na+ /H+ exchange or indirect acid extrusion via Na+ -HCO3 - cotransport. PCR and immunoblotting demonstrated expression of HVCN1 mRNA and protein in canine heart. Patch clamp analysis of canine ventricular myocytes revealed a voltage-gated H+ current that was highly H+ -selective. The current was blocked by external Zn2+ and the HVCN1 blocker 5-chloro-2-guanidinobenzimidazole (ClGBI). Both the gating and Zn2+ blockade of the current were strongly influenced by the pH gradient across the membrane. All characteristics of the observed current were consistent with the known hallmarks of HVCN1-mediated H+ current. Inhibition of HVCN1 and the NHE1 Na+ /H+ exchanger, singly and in combination, showed that either mechanism is largely sufficient to maintain pHi in beating cardiomyocytes, but that inhibition of both activities causes rapid acidification. These results show that HVCN1 is expressed in canine ventricular myocytes and provides a major H+ -extrusion activity, with a capacity similar to that of NHE1. In the beating heart in vivo, this activity would allow Na+ -independent extrusion of H+ during each action potential and, when functionally coupled with anion transport mechanisms, could facilitate transport-mediated CO2 disposal. Abstract figure legend The HVCN1 proton channel is expressed in canine ventricular myocytes and contributes to H+ extrusion. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Jianyong Ma
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, 45267, USA
| | - Xiaoqian Gao
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, 45267, USA
| | - Yutian Li
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, 45267, USA
| | - Thomas E DeCoursey
- Department of Physiology & Biophysics, Rush University, Chicago, Illinois, 60612, USA
| | - Gary E Shull
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, 45267, USA
| | - Hong-Sheng Wang
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, 45267, USA
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3
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Cass JA, Williams CD, Irving TC, Lauga E, Malingen S, Daniel TL, Sponberg SN. A mechanism for sarcomere breathing: volume change and advective flow within the myofilament lattice. Biophys J 2021; 120:4079-4090. [PMID: 34384761 DOI: 10.1016/j.bpj.2021.08.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 06/19/2021] [Accepted: 08/04/2021] [Indexed: 11/28/2022] Open
Abstract
During muscle contraction, myosin motors anchored to thick filaments bind to and slide actin thin filaments. These motors rely on energy derived from ATP, supplied, in part, by diffusion from the sarcoplasm to the interior of the lattice of actin and myosin filaments. The radial spacing of filaments in this lattice may change or remain constant during contraction. If the lattice is isovolumetric, it must expand when the muscle shortens. If, however, the spacing is constant or has a different pattern of axial and radial motion, then the lattice changes volume during contraction, driving fluid motion and assisting in the transport of molecules between the contractile lattice and the surrounding intracellular space. We first create an advective-diffusive-reaction flow model and show that the flow into and out of the sarcomere lattice would be significant in the absence of lattice expansion. Advective transport coupled to diffusion has the potential to substantially enhance metabolite exchange within the crowded sarcomere. Using time-resolved x-ray diffraction of contracting muscle, we next show that the contractile lattice is neither isovolumetric nor constant in spacing. Instead, lattice spacing is time varying, depends on activation, and can manifest as an effective time-varying Poisson ratio. The resulting fluid flow in the sarcomere lattice of synchronous insect flight muscles is even greater than expected for constant lattice spacing conditions. Lattice spacing depends on a variety of factors that produce radial force, including cross-bridges, titin-like molecules, and other structural proteins. Volume change and advective transport varies with the phase of muscle stimulation during periodic contraction but remains significant at all conditions. Although varying in magnitude, advective transport will occur in all cases in which the sarcomere is not isovolumetric. Akin to "breathing," advective-diffusive transport in sarcomeres is sufficient to promote metabolite exchange and may play a role in the regulation of contraction itself.
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Affiliation(s)
- Julie A Cass
- Allen Institute for Cell Science, Seattle, Washington; Department of Biology, University of Washington, Seattle, Washington
| | - C David Williams
- Department of Biology, University of Washington, Seattle, Washington; Applied ML Group, Microsoft CSE, Redmond, Washington
| | - Thomas C Irving
- BioCAT and CSRRI, Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois
| | - Eric Lauga
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
| | - Sage Malingen
- Department of Biology, University of Washington, Seattle, Washington
| | - Thomas L Daniel
- Department of Biology, University of Washington, Seattle, Washington.
| | - Simon N Sponberg
- School of Physics & School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia.
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4
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Balderas-Villalobos J, Steele TWE, Eltit JM. Physiological and Pathological Relevance of Selective and Nonselective Ca 2+ Channels in Skeletal and Cardiac Muscle. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1349:225-247. [PMID: 35138617 PMCID: PMC10683374 DOI: 10.1007/978-981-16-4254-8_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Contraction of the striated muscle is fundamental for human existence. The action of voluntary skeletal muscle enables activities such as breathing, establishing body posture, and diverse body movements. Additionally, highly precise motion empowers communication, artistic expression, and other activities that define everyday human life. The involuntary contraction of striated muscle is the core function of the heart and is essential for blood flow. Several ion channels are important in the transduction of action potentials to cytosolic Ca2+ signals that enable muscle contraction; however, other ion channels are involved in the progression of muscle pathologies that can impair normal life or threaten it. This chapter describes types of selective and nonselective Ca2+ permeable ion channels expressed in the striated muscle, their participation in different aspects of muscle excitation and contraction, and their relevance to the progression of some pathological states.
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Affiliation(s)
- Jaime Balderas-Villalobos
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA
| | - Tyler W E Steele
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA
| | - Jose M Eltit
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA.
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Rog-Zielinska EA, Scardigli M, Peyronnet R, Zgierski-Johnston CM, Greiner J, Madl J, O'Toole ET, Morphew M, Hoenger A, Sacconi L, Kohl P. Beat-by-Beat Cardiomyocyte T-Tubule Deformation Drives Tubular Content Exchange. Circ Res 2020; 128:203-215. [PMID: 33228470 PMCID: PMC7834912 DOI: 10.1161/circresaha.120.317266] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Supplemental Digital Content is available in the text. The sarcolemma of cardiomyocytes contains many proteins that are essential for electromechanical function in general, and excitation-contraction coupling in particular. The distribution of these proteins is nonuniform between the bulk sarcolemmal surface and membrane invaginations known as transverse tubules (TT). TT form an intricate network of fluid-filled conduits that support electromechanical synchronicity within cardiomyocytes. Although continuous with the extracellular space, the narrow lumen and the tortuous structure of TT can form domains of restricted diffusion. As a result of unequal ion fluxes across cell surface and TT membranes, limited diffusion may generate ion gradients within TT, especially deep within the TT network and at high pacing rates.
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Affiliation(s)
- Eva A Rog-Zielinska
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, and Faculty of Medicine, University of Freiburg, Germany (E.A.R.-Z., R.P., C.M.Z.-J., J.G., J.M., L.S., P.K.)
| | - Marina Scardigli
- European Laboratory for Non-Linear Spectroscopy, National Institute of Optics, National Research Council, Sesto Fiorentino (Florence), Italy (M.S., L.S.)
| | - Remi Peyronnet
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, and Faculty of Medicine, University of Freiburg, Germany (E.A.R.-Z., R.P., C.M.Z.-J., J.G., J.M., L.S., P.K.)
| | - Callum M Zgierski-Johnston
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, and Faculty of Medicine, University of Freiburg, Germany (E.A.R.-Z., R.P., C.M.Z.-J., J.G., J.M., L.S., P.K.)
| | - Joachim Greiner
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, and Faculty of Medicine, University of Freiburg, Germany (E.A.R.-Z., R.P., C.M.Z.-J., J.G., J.M., L.S., P.K.)
| | - Josef Madl
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, and Faculty of Medicine, University of Freiburg, Germany (E.A.R.-Z., R.P., C.M.Z.-J., J.G., J.M., L.S., P.K.)
| | - Eileen T O'Toole
- Department of Molecular, Cellular and Developmental Biology, University of Colorado at Boulder (E.T.O., M.M., A.H.)
| | - Mary Morphew
- Department of Molecular, Cellular and Developmental Biology, University of Colorado at Boulder (E.T.O., M.M., A.H.)
| | - Andreas Hoenger
- Department of Molecular, Cellular and Developmental Biology, University of Colorado at Boulder (E.T.O., M.M., A.H.)
| | - Leonardo Sacconi
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, and Faculty of Medicine, University of Freiburg, Germany (E.A.R.-Z., R.P., C.M.Z.-J., J.G., J.M., L.S., P.K.).,European Laboratory for Non-Linear Spectroscopy, National Institute of Optics, National Research Council, Sesto Fiorentino (Florence), Italy (M.S., L.S.)
| | - Peter Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, and Faculty of Medicine, University of Freiburg, Germany (E.A.R.-Z., R.P., C.M.Z.-J., J.G., J.M., L.S., P.K.).,CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, Germany (P.K.)
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6
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Marchena M, Echebarria B. Influence of the tubular network on the characteristics of calcium transients in cardiac myocytes. PLoS One 2020; 15:e0231056. [PMID: 32302318 PMCID: PMC7164608 DOI: 10.1371/journal.pone.0231056] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 03/14/2020] [Indexed: 01/09/2023] Open
Abstract
Transverse and axial tubules (TATS) are an essential ingredient of the excitation-contraction machinery that allow the effective coupling of L-type Calcium Channels (LCC) and ryanodine receptors (RyR2). They form a regular network in ventricular cells, while their presence in atrial myocytes is variable regionally and among animal species We have studied the effect of variations in the TAT network using a bidomain computational model of an atrial myocyte with variable density of tubules. At each z-line the t-tubule length is obtained from an exponential distribution, with a given mean penetration length. This gives rise to a distribution of t-tubules in the cell that is characterized by the fractional area (F.A.) occupied by the t-tubules. To obtain consistent results, we average over different realizations of the same mean penetration length. To this, in some simulations we add the effect of a network of axial tubules. Then we study global properties of calcium signaling, as well as regional heterogeneities and local properties of sparks and RyR2 openings. In agreement with recent experiments in detubulated ventricular and atrial cells, we find that detubulation reduces the calcium transient and synchronization in release. However, it does not affect sarcoplasmic reticulum (SR) load, so the decrease in SR calcium release is due to regional differences in Ca2+ release, that is restricted to the cell periphery in detubulated cells. Despite the decrease in release, the release gain is larger in detubulated cells, due to recruitment of orphaned RyR2s, i.e, those that are not confronting a cluster of LCCs. This probably provides a safeguard mechanism, allowing physiological values to be maintained upon small changes in the t-tubule density. Finally, we do not find any relevant change in spark properties between tubulated and detubulated cells, suggesting that the differences found in experiments could be due to differential properties of the RyR2s in the membrane and in the t-tubules, not incorporated in the present model. This work will help understand the effect of detubulation, that has been shown to occur in disease conditions such as heart failure (HF) in ventricular cells, or atrial fibrillation (AF) in atrial cells.
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Affiliation(s)
- Miquel Marchena
- Departament de Física, Universitat Politècnica de Catalunya, Barcelona, Spain
| | - Blas Echebarria
- Departament de Física, Universitat Politècnica de Catalunya, Barcelona, Spain
- * E-mail:
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7
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Colli DF, Blood SR, Sankarankutty AC, Sachse FB, Frisk M, Louch WE, Kekenes-Huskey PM. A Matched-Filter-Based Algorithm for Subcellular Classification of T-System in Cardiac Tissues. Biophys J 2019; 116:1386-1393. [PMID: 30979553 PMCID: PMC6486484 DOI: 10.1016/j.bpj.2019.03.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 03/04/2019] [Accepted: 03/06/2019] [Indexed: 11/26/2022] Open
Abstract
In mammalian ventricular cardiomyocytes, invaginations of the surface membrane form the transverse tubular system (T-system), which consists of transverse tubules (TTs) that align with sarcomeres and Z-lines as well as longitudinal tubules (LTs) that are present between Z-lines in some species. In many cardiac disease etiologies, the T-system is perturbed, which is believed to promote spatially heterogeneous, dyssynchronous Ca2+ release and inefficient contraction. In general, T-system characterization approaches have been directed primarily at isolated cells and do not detect subcellular T-system heterogeneity. Here, we present MatchedMyo, a matched-filter-based algorithm for subcellular T-system characterization in isolated cardiomyocytes and millimeter-scale myocardial sections. The algorithm utilizes "filters" representative of TTs, LTs, and T-system absence. Application of the algorithm to cardiomyocytes isolated from rat disease models of myocardial infarction (MI), dilated cardiomyopathy induced via aortic banding, and sham surgery confirmed and quantified heterogeneous T-system structure and remodeling. Cardiomyocytes from post-MI hearts exhibited increasing T-system disarray as proximity to the infarct increased. We found significant (p < 0.05, Welch's t-test) increases in LT density within cardiomyocytes proximal to the infarct (12 ± 3%, data reported as mean ± SD, n = 3) versus sham (4 ± 2%, n = 5), but not distal to the infarct (7 ± 1%, n = 3). The algorithm also detected decreases in TTs within 5° of the myocyte minor axis for isolated aortic banding (36 ± 9%, n = 3) and MI cardiomyocytes located intermediate (37 ± 4%, n = 3) and proximal (34 ± 4%, n = 3) to the infarct versus sham (57 ± 12%, n = 5). Application of bootstrapping to rabbit MI tissue revealed distal sections comprised 18.9 ± 1.0% TTs, whereas proximal sections comprised 10.1 ± 0.8% TTs (p < 0.05), a 46.6% decrease. The matched-filter approach therefore provides a robust and scalable technique for T-system characterization from isolated cells through millimeter-scale myocardial sections.
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Affiliation(s)
- Dylan F Colli
- Department of Chemistry, University of Kentucky, Lexington, Kentucky; Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky.
| | - S Ryan Blood
- Department of Chemistry, University of Kentucky, Lexington, Kentucky; Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky
| | - Aparna C Sankarankutty
- Nora Eccles Harrison Cardiovascular Research and Training Institute & Department of Bioengineering, University of Utah, Salt Lake City, Utah
| | - Frank B Sachse
- Nora Eccles Harrison Cardiovascular Research and Training Institute & Department of Bioengineering, University of Utah, Salt Lake City, Utah
| | - Michael Frisk
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; K.G. 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; K.G. Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Peter M Kekenes-Huskey
- Department of Chemistry, University of Kentucky, Lexington, Kentucky; Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky
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8
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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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9
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Rog-Zielinska EA, O'Toole ET, Hoenger A, Kohl P. Mitochondrial Deformation During the Cardiac Mechanical Cycle. Anat Rec (Hoboken) 2018; 302:146-152. [PMID: 30302911 PMCID: PMC6312496 DOI: 10.1002/ar.23917] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 04/22/2018] [Accepted: 05/11/2018] [Indexed: 12/17/2022]
Abstract
Cardiomyocytes both cause and experience continual cyclic deformation. The exact effects of this deformation on the properties of intracellular organelles are not well characterized, although they are likely to be relevant for cardiomyocyte responses to active and passive changes in their mechanical environment. In the present study we provide three‐dimensional ultrastructural evidence for mechanically induced mitochondrial deformation in rabbit ventricular cardiomyocytes over a range of sarcomere lengths representing myocardial tissue stretch, an unloaded “slack” state, and contracture. We also show structural indications for interaction of mitochondria with one another, as well as with other intracellular elements such as microtubules, sarcoplasmic reticulum and T‐tubules. The data presented here help to contextualize recent reports on the mechanosensitivity and cell‐wide connectivity of the mitochondrial network and provide a structural framework that may aide interpretation of mechanically‐regulated molecular signaling in cardiac cells. Anat Rec, 302:146–152, 2019. © 2018 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.
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Affiliation(s)
- E A Rog-Zielinska
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg, Bad Krozingen, and Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - E T O'Toole
- Department of Molecular, Cellular and Developmental Biology, University of Colorado at Boulder, Boulder, Colorado, USA
| | - A Hoenger
- Department of Molecular, Cellular and Developmental Biology, University of Colorado at Boulder, Boulder, Colorado, USA
| | - P Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg, Bad Krozingen, and Faculty of Medicine, University of Freiburg, Freiburg, Germany
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10
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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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Seidel T, Navankasattusas S, Ahmad A, Diakos NA, Xu WD, Tristani-Firouzi M, Bonios MJ, Taleb I, Li DY, Selzman CH, Drakos SG, Sachse FB. Sheet-Like Remodeling of the Transverse Tubular System in Human Heart Failure Impairs Excitation-Contraction Coupling and Functional Recovery by Mechanical Unloading. Circulation 2017; 135:1632-1645. [PMID: 28073805 PMCID: PMC5404964 DOI: 10.1161/circulationaha.116.024470] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 12/14/2016] [Indexed: 01/02/2023]
Abstract
BACKGROUND Cardiac recovery in response to mechanical unloading by left ventricular assist devices (LVADs) has been demonstrated in subgroups of patients with chronic heart failure (HF). Hallmarks of HF are depletion and disorganization of the transverse tubular system (t-system) in cardiomyocytes. Here, we investigated remodeling of the t-system in human end-stage HF and its role in cardiac recovery. METHODS Left ventricular biopsies were obtained from 5 donors and 26 patients with chronic HF undergoing implantation of LVADs. Three-dimensional confocal microscopy and computational image analysis were applied to assess t-system structure, density, and distance of ryanodine receptor clusters to the sarcolemma, including the t-system. Recovery of cardiac function in response to mechanical unloading was assessed by echocardiography during turndown of the LVAD. RESULTS The majority of HF myocytes showed remarkable t-system remodeling, particularly sheet-like invaginations of the sarcolemma. Circularity of t-system components was decreased in HF versus controls (0.37±0.01 versus 0.46±0.02; P<0.01), and the volume/length ratio was increased in HF (0.36±0.01 versus 0.25±0.02 µm2; P<0.0001). T-system density was reduced in HF, leading to increased ryanodine receptor-sarcolemma distances (0.96±0.05 versus 0.64±0.1 µm; P<0.01). Low ryanodine receptor-sarcolemma distances at the time of LVAD implantation predicted high post-LVAD left ventricular ejection fractions (P<0.01) and ejection fraction increases during unloading (P<0.01). Ejection fraction in patients with pre-LVAD ryanodine receptor-sarcolemma distances >1 µm did not improve after mechanical unloading. In addition, calcium transients were recorded in field-stimulated isolated human cardiomyocytes and analyzed with respect to local t-system density. Calcium release in HF myocytes was restricted to regions proximal to the sarcolemma. Local calcium upstroke was delayed (23.9±4.9 versus 10.3±1.7 milliseconds; P<0.05) and more asynchronous (18.1±1.5 versus 8.9±2.2 milliseconds; P<0.01) in HF cells with low t-system density versus cells with high t-system density. CONCLUSIONS The t-system in end-stage human HF presents a characteristic novel phenotype consisting of sheet-like invaginations of the sarcolemma. Our results suggest that the remodeled t-system impairs excitation-contraction coupling and functional recovery during chronic LVAD unloading. An intact t-system at the time of LVAD implantation may constitute a precondition and predictor for functional cardiac recovery after mechanical unloading.
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Affiliation(s)
- Thomas Seidel
- From Nora Eccles Harrison Cardiovascular Research and Training Institute (T.S., A.A., M.T.-F., S.G.D., F.B.S.), Molecular Medicine Program (S.N., N.A.D., D.Y.L., C.H.S.), Department of Bioengineering (A.A., F.B.S.), Division of Cardiovascular Medicine (W.D.X., M.J.B., I.T., D.Y.L., S.G.D.), and Division of Cardiothoracic Surgery (C.H.S.), University of Utah, Salt Lake City. Dr Seidel is currently at the Institute for Cellular and Molecular Physiology, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Germany.
| | - Sutip Navankasattusas
- From Nora Eccles Harrison Cardiovascular Research and Training Institute (T.S., A.A., M.T.-F., S.G.D., F.B.S.), Molecular Medicine Program (S.N., N.A.D., D.Y.L., C.H.S.), Department of Bioengineering (A.A., F.B.S.), Division of Cardiovascular Medicine (W.D.X., M.J.B., I.T., D.Y.L., S.G.D.), and Division of Cardiothoracic Surgery (C.H.S.), University of Utah, Salt Lake City. Dr Seidel is currently at the Institute for Cellular and Molecular Physiology, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Germany
| | - Azmi Ahmad
- From Nora Eccles Harrison Cardiovascular Research and Training Institute (T.S., A.A., M.T.-F., S.G.D., F.B.S.), Molecular Medicine Program (S.N., N.A.D., D.Y.L., C.H.S.), Department of Bioengineering (A.A., F.B.S.), Division of Cardiovascular Medicine (W.D.X., M.J.B., I.T., D.Y.L., S.G.D.), and Division of Cardiothoracic Surgery (C.H.S.), University of Utah, Salt Lake City. Dr Seidel is currently at the Institute for Cellular and Molecular Physiology, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Germany
| | - Nikolaos A Diakos
- From Nora Eccles Harrison Cardiovascular Research and Training Institute (T.S., A.A., M.T.-F., S.G.D., F.B.S.), Molecular Medicine Program (S.N., N.A.D., D.Y.L., C.H.S.), Department of Bioengineering (A.A., F.B.S.), Division of Cardiovascular Medicine (W.D.X., M.J.B., I.T., D.Y.L., S.G.D.), and Division of Cardiothoracic Surgery (C.H.S.), University of Utah, Salt Lake City. Dr Seidel is currently at the Institute for Cellular and Molecular Physiology, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Germany
| | - Weining David Xu
- From Nora Eccles Harrison Cardiovascular Research and Training Institute (T.S., A.A., M.T.-F., S.G.D., F.B.S.), Molecular Medicine Program (S.N., N.A.D., D.Y.L., C.H.S.), Department of Bioengineering (A.A., F.B.S.), Division of Cardiovascular Medicine (W.D.X., M.J.B., I.T., D.Y.L., S.G.D.), and Division of Cardiothoracic Surgery (C.H.S.), University of Utah, Salt Lake City. Dr Seidel is currently at the Institute for Cellular and Molecular Physiology, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Germany
| | - Martin Tristani-Firouzi
- From Nora Eccles Harrison Cardiovascular Research and Training Institute (T.S., A.A., M.T.-F., S.G.D., F.B.S.), Molecular Medicine Program (S.N., N.A.D., D.Y.L., C.H.S.), Department of Bioengineering (A.A., F.B.S.), Division of Cardiovascular Medicine (W.D.X., M.J.B., I.T., D.Y.L., S.G.D.), and Division of Cardiothoracic Surgery (C.H.S.), University of Utah, Salt Lake City. Dr Seidel is currently at the Institute for Cellular and Molecular Physiology, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Germany
| | - Michael J Bonios
- From Nora Eccles Harrison Cardiovascular Research and Training Institute (T.S., A.A., M.T.-F., S.G.D., F.B.S.), Molecular Medicine Program (S.N., N.A.D., D.Y.L., C.H.S.), Department of Bioengineering (A.A., F.B.S.), Division of Cardiovascular Medicine (W.D.X., M.J.B., I.T., D.Y.L., S.G.D.), and Division of Cardiothoracic Surgery (C.H.S.), University of Utah, Salt Lake City. Dr Seidel is currently at the Institute for Cellular and Molecular Physiology, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Germany
| | - Iosif Taleb
- From Nora Eccles Harrison Cardiovascular Research and Training Institute (T.S., A.A., M.T.-F., S.G.D., F.B.S.), Molecular Medicine Program (S.N., N.A.D., D.Y.L., C.H.S.), Department of Bioengineering (A.A., F.B.S.), Division of Cardiovascular Medicine (W.D.X., M.J.B., I.T., D.Y.L., S.G.D.), and Division of Cardiothoracic Surgery (C.H.S.), University of Utah, Salt Lake City. Dr Seidel is currently at the Institute for Cellular and Molecular Physiology, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Germany
| | - Dean Y Li
- From Nora Eccles Harrison Cardiovascular Research and Training Institute (T.S., A.A., M.T.-F., S.G.D., F.B.S.), Molecular Medicine Program (S.N., N.A.D., D.Y.L., C.H.S.), Department of Bioengineering (A.A., F.B.S.), Division of Cardiovascular Medicine (W.D.X., M.J.B., I.T., D.Y.L., S.G.D.), and Division of Cardiothoracic Surgery (C.H.S.), University of Utah, Salt Lake City. Dr Seidel is currently at the Institute for Cellular and Molecular Physiology, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Germany
| | - Craig H Selzman
- From Nora Eccles Harrison Cardiovascular Research and Training Institute (T.S., A.A., M.T.-F., S.G.D., F.B.S.), Molecular Medicine Program (S.N., N.A.D., D.Y.L., C.H.S.), Department of Bioengineering (A.A., F.B.S.), Division of Cardiovascular Medicine (W.D.X., M.J.B., I.T., D.Y.L., S.G.D.), and Division of Cardiothoracic Surgery (C.H.S.), University of Utah, Salt Lake City. Dr Seidel is currently at the Institute for Cellular and Molecular Physiology, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Germany
| | - Stavros G Drakos
- From Nora Eccles Harrison Cardiovascular Research and Training Institute (T.S., A.A., M.T.-F., S.G.D., F.B.S.), Molecular Medicine Program (S.N., N.A.D., D.Y.L., C.H.S.), Department of Bioengineering (A.A., F.B.S.), Division of Cardiovascular Medicine (W.D.X., M.J.B., I.T., D.Y.L., S.G.D.), and Division of Cardiothoracic Surgery (C.H.S.), University of Utah, Salt Lake City. Dr Seidel is currently at the Institute for Cellular and Molecular Physiology, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Germany.
| | - Frank B Sachse
- From Nora Eccles Harrison Cardiovascular Research and Training Institute (T.S., A.A., M.T.-F., S.G.D., F.B.S.), Molecular Medicine Program (S.N., N.A.D., D.Y.L., C.H.S.), Department of Bioengineering (A.A., F.B.S.), Division of Cardiovascular Medicine (W.D.X., M.J.B., I.T., D.Y.L., S.G.D.), and Division of Cardiothoracic Surgery (C.H.S.), University of Utah, Salt Lake City. Dr Seidel is currently at the Institute for Cellular and Molecular Physiology, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Germany.
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Lu P, Zhang YQ, Zhang H, Li YF, Wang XY, Xu H, Liu ZW, Li L, Dong HY, Zhang ZM. Pigment Epithelium-Derived Factor (PEDF) Improves Ischemic Cardiac Functional Reserve Through Decreasing Hypoxic Cardiomyocyte Contractility Through PEDF Receptor (PEDF-R). J Am Heart Assoc 2016; 5:e003179. [PMID: 27413044 PMCID: PMC5015364 DOI: 10.1161/jaha.115.003179] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 06/21/2016] [Indexed: 12/22/2022]
Abstract
BACKGROUND Pigment epithelium-derived factor (PEDF), which belongs to the noninhibitory serpin family, has shown the ability to stimulate several physiological processes, such as antiangiogenesis, anti-inflammation, and antioxidation. In the present study, the effects of PEDF on contractility and calcium handling of rat ventricular myocytes were investigated. METHODS AND RESULTS Adult Sprague-Dawley rat models of acute myocardial infarction (AMI) were surgically established. PEDF-lentivirus was delivered into the myocardium along and away from the infarction border to overexpress PEDF. Video edge detection was used to measure myocyte shortening in vitro. Intracellular Ca(2+) was measured in cells loaded with the Ca(2+) sensitive fluorescent indicator, Fura-2-acetoxymethyl ester. PEDF local overexpression enhanced cardiac functional reserve in AMI rats and reduced myocardial contracture bordering the infracted area. Exogenous PEDF treatment (10 nmol/L) caused a significant decrease in amplitudes of isoproterenol-stimulated myocyte shortening, Ca(2+) transients, and caffeine-evoked Ca(2+) transients in vitro. We then tested a potential role for PEDF receptor-mediated effects on upregulation of protein kinase C (PKC) and found evidence of signaling through the diacylglycerol/PKCα pathway. We also confirmed that pretreatment of cardiomyocytes with PEDF exhibited dephosphorylation of phospholamban at Ser(16), which could be attenuated with PKC inhibition. CONCLUSIONS The results suggest that PEDF depresses myocyte contractility by suppressing phosphorylation of phospholamban and Ca(2+) transients in a PKCα-dependent manner through its receptor, PEDF receptor, therefore improving cardiac functional reserve during AMI.
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Affiliation(s)
- Peng Lu
- Department of Thoracic Cardiovascular Surgery, Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Yi-Qian Zhang
- Department of Thoracic Cardiovascular Surgery, Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Hao Zhang
- Department of Thoracic Cardiovascular Surgery, Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Yu-Feng Li
- Department of Thoracic Cardiovascular Surgery, Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Xiao-Yu Wang
- Department of Thoracic Cardiovascular Surgery, Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Hao Xu
- Research Center for Biochemistry and Molecular Biology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Zhi-Wei Liu
- Research Center for Morphology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Lei Li
- Department of Thoracic Cardiovascular Surgery, Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Hong-Yan Dong
- Research Center for Morphology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Zhong-Ming Zhang
- Department of Thoracic Cardiovascular Surgery, Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China
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13
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Quinn TA, Kohl P. Rabbit models of cardiac mechano-electric and mechano-mechanical coupling. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 121:110-22. [PMID: 27208698 PMCID: PMC5067302 DOI: 10.1016/j.pbiomolbio.2016.05.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 05/01/2016] [Indexed: 12/11/2022]
Abstract
Cardiac auto-regulation involves integrated regulatory loops linking electrics and mechanics in the heart. Whereas mechanical activity is usually seen as 'the endpoint' of cardiac auto-regulation, it is important to appreciate that the heart would not function without feed-back from the mechanical environment to cardiac electrical (mechano-electric coupling, MEC) and mechanical (mechano-mechanical coupling, MMC) activity. MEC and MMC contribute to beat-by-beat adaption of cardiac output to physiological demand, and they are involved in various pathological settings, potentially aggravating cardiac dysfunction. Experimental and computational studies using rabbit as a model species have been integral to the development of our current understanding of MEC and MMC. In this paper we review this work, focusing on physiological and pathological implications for cardiac function.
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Affiliation(s)
- T Alexander Quinn
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Canada.
| | - Peter Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Centre Freiburg - Bad Krozingen, Faculty of Medicine, University of Freiburg, Freiburg, Germany; National Heart and Lung Institute, Imperial College London, London, UK
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14
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Abstract
Mechanical forces will have been omnipresent since the origin of life, and living organisms have evolved mechanisms to sense, interpret, and respond to mechanical stimuli. The cardiovascular system in general, and the heart in particular, is exposed to constantly changing mechanical signals, including stretch, compression, bending, and shear. The heart adjusts its performance to the mechanical environment, modifying electrical, mechanical, metabolic, and structural properties over a range of time scales. Many of the underlying regulatory processes are encoded intracardially and are, thus, maintained even in heart transplant recipients. Although mechanosensitivity of heart rhythm has been described in the medical literature for over a century, its molecular mechanisms are incompletely understood. Thanks to modern biophysical and molecular technologies, the roles of mechanical forces in cardiac biology are being explored in more detail, and detailed mechanisms of mechanotransduction have started to emerge. Mechano-gated ion channels are cardiac mechanoreceptors. They give rise to mechano-electric feedback, thought to contribute to normal function, disease development, and, potentially, therapeutic interventions. In this review, we focus on acute mechanical effects on cardiac electrophysiology, explore molecular candidates underlying observed responses, and discuss their pharmaceutical regulation. From this, we identify open research questions and highlight emerging technologies that may help in addressing them.
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Affiliation(s)
- Rémi Peyronnet
- From the National Heart and Lung Institute, Imperial College London, United Kingdom (R.P., P.K.); Departments of Developmental Biology and Internal Medicine, Center for Cardiovascular Research, Washington University School of Medicine, St. Louis, MO (J.M.N.); Institute for Experimental Cardiovascular Medicine, University Heart Centre Freiburg/Bad Krozingen, Freiburg, Germany (R.P., P.K.)
| | - Jeanne M Nerbonne
- From the National Heart and Lung Institute, Imperial College London, United Kingdom (R.P., P.K.); Departments of Developmental Biology and Internal Medicine, Center for Cardiovascular Research, Washington University School of Medicine, St. Louis, MO (J.M.N.); Institute for Experimental Cardiovascular Medicine, University Heart Centre Freiburg/Bad Krozingen, Freiburg, Germany (R.P., P.K.)
| | - Peter Kohl
- From the National Heart and Lung Institute, Imperial College London, United Kingdom (R.P., P.K.); Departments of Developmental Biology and Internal Medicine, Center for Cardiovascular Research, Washington University School of Medicine, St. Louis, MO (J.M.N.); Institute for Experimental Cardiovascular Medicine, University Heart Centre Freiburg/Bad Krozingen, Freiburg, Germany (R.P., P.K.).
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15
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Electron tomography of rabbit cardiomyocyte three-dimensional ultrastructure. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 121:77-84. [PMID: 27210305 PMCID: PMC4959512 DOI: 10.1016/j.pbiomolbio.2016.05.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 05/01/2016] [Indexed: 12/22/2022]
Abstract
The field of cardiovascular research has benefitted from rapid developments in imaging technology over the last few decades. Accordingly, an ever growing number of large, multidimensional data sets have begun to appear, often challenging existing pre-conceptions about structure and function of biological systems. For tissue and cell structure imaging, the move from 2D section-based microscopy to true 3D data collection has been a major driver of new insight. In the sub-cellular domain, electron tomography is a powerful technique for exploration of cellular structures in 3D with unparalleled fidelity at nanometer resolution. Electron tomography is particularly advantageous for studying highly compartmentalised cells such as cardiomyocytes, where elaborate sub-cellular structures play crucial roles in electrophysiology and mechanics. Although the anatomy of specific ultra-structures, such as dyadic couplons, has been extensively explored using 2D electron microscopy of thin sections, we still lack accurate, quantitative knowledge of true individual shape, volume and surface area of sub-cellular domains, as well as their 3D spatial interrelations; let alone of how these are reshaped during the cycle of contraction and relaxation. Here we discuss and illustrate the utility of ET for identification, visualisation, and analysis of 3D cardiomyocyte ultrastructures such as the T-tubular system, sarcoplasmic reticulum, mitochondria and microtubules.
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16
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Hatano A, Okada JI, Washio T, Hisada T, Sugiura S. An integrated finite element simulation of cardiomyocyte function based on triphasic theory. Front Physiol 2015; 6:287. [PMID: 26539124 PMCID: PMC4611143 DOI: 10.3389/fphys.2015.00287] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 09/28/2015] [Indexed: 11/13/2022] Open
Abstract
In numerical simulations of cardiac excitation-contraction coupling, the intracellular potential distribution and mobility of cytosol and ions have been mostly ignored. Although the intracellular potential gradient is small, during depolarization it can be a significant driving force for ion movement, and is comparable to diffusion in terms of net flux. Furthermore, fluid in the t-tubules is thought to advect ions to facilitate their exchange with the extracellular space. We extend our previous finite element model that was based on triphasic theory to examine the significance of these factors in cardiac physiology. Triphasic theory allows us to study the behavior of solids (proteins), fluids (cytosol) and ions governed by mechanics and electrochemistry in detailed subcellular structures, including myofibrils, mitochondria, the sarcoplasmic reticulum, membranes, and t-tubules. Our simulation results predicted an electrical potential gradient inside the t-tubules at the onset of depolarization, which corresponded to the Na(+) channel distribution therein. Ejection and suction of fluid between the t-tubules and the extracellular compartment during isometric contraction were observed. We also examined the influence of t-tubule morphology and mitochondrial location on the electrophysiology and mechanics of the cardiomyocyte. Our results confirm that the t-tubule structure is important for synchrony of Ca(2+) release, and suggest that mitochondria in the sub-sarcolemmal region might serve to cancel Ca(2+) inflow through surface sarcolemma, thereby maintaining the intracellular Ca(2+) environment in equilibrium.
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Affiliation(s)
- Asuka Hatano
- Department of Mechanical Engineering, School of Engineering, The University of Tokyo Tokyo, Japan
| | - Jun-Ichi Okada
- Department of Human and Engineered Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo Chiba, Japan
| | - Takumi Washio
- Department of Human and Engineered Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo Chiba, Japan
| | - Toshiaki Hisada
- Department of Human and Engineered Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo Chiba, Japan
| | - Seiryo Sugiura
- Department of Human and Engineered Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo Chiba, Japan
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Roe AT, Frisk M, Louch WE. Targeting cardiomyocyte Ca2+ homeostasis in heart failure. Curr Pharm Des 2015; 21:431-48. [PMID: 25483944 PMCID: PMC4475738 DOI: 10.2174/138161282104141204124129] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2014] [Accepted: 08/06/2014] [Indexed: 12/19/2022]
Abstract
Improved treatments for heart failure patients will require the development of novel therapeutic strategies that target basal disease
mechanisms. Disrupted cardiomyocyte Ca2+ homeostasis is recognized as a major contributor to the heart failure phenotype, as it
plays a key role in systolic and diastolic dysfunction, arrhythmogenesis, and hypertrophy and apoptosis signaling. In this review, we outline
existing knowledge of the involvement of Ca2+ homeostasis in these deficits, and identify four promising targets for therapeutic intervention:
the sarcoplasmic reticulum Ca2+ ATPase, the Na+-Ca2+ exchanger, the ryanodine receptor, and t-tubule structure. We discuss
experimental data indicating the applicability of these targets that has led to recent and ongoing clinical trials, and suggest future therapeutic
approaches.
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Affiliation(s)
| | | | - William E Louch
- Institute for Experimental Medical Research, Kirkeveien 166, 4.etg. Bygg 7, Oslo University Hospital Ullevål, 0407 Oslo, Norway.
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18
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Li H, Lichter JG, Seidel T, Tomaselli GF, Bridge JHB, Sachse FB. Cardiac Resynchronization Therapy Reduces Subcellular Heterogeneity of Ryanodine Receptors, T-Tubules, and Ca2+ Sparks Produced by Dyssynchronous Heart Failure. Circ Heart Fail 2015; 8:1105-14. [PMID: 26294422 DOI: 10.1161/circheartfailure.115.002352] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 08/17/2015] [Indexed: 11/16/2022]
Abstract
BACKGROUND Cardiac resynchronization therapy (CRT) is a major advance for treatment of patients with dyssynchronous heart failure (DHF). However, our understanding of DHF-associated remodeling of subcellular structure and function and their restoration after CRT remains incomplete. METHODS AND RESULTS We investigated subcellular heterogeneity of remodeling of structures and proteins associated with excitation-contraction coupling in cardiomyocytes in DHF and after CRT. Three-dimensional confocal microscopy revealed subcellular heterogeneity of ryanodine receptor (RyR) density and the transverse tubular system (t-system) in a canine model of DHF. RyR density at the ends of lateral left ventricular cardiomyocytes was higher than that in cell centers, whereas the t-system was depleted at cell ends. In anterior left ventricular cardiomyocytes, however, we found a similar degree of heterogeneous RyR remodeling, despite preserved t-system. Synchronous heart failure was associated with marginal heterogeneity of RyR density. We used rapid scanning confocal microscopy to investigate effects of heterogeneous structural remodeling on calcium signaling. In DHF, diastolic Ca(2+) spark density was smaller at cell ends versus centers. After CRT, subcellular heterogeneity of structures and function was reduced. CONCLUSIONS RyR density exhibits remarkable subcellular heterogeneity in DHF. RyR remodeling occurred in lateral and anterior cardiomyocytes, but remodeling of t-system was confined to lateral myocytes. These findings indicate that different mechanisms underlie remodeling of RyRs and t-system. Furthermore, we suggest that ventricular dyssynchrony exacerbates subcellular remodeling in heart failure. CRT efficiently reduced subcellular heterogeneity. These results will help to explain remodeling of excitation-contraction coupling in disease and restoration after CRT.
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Affiliation(s)
- Hui Li
- From the Nora Eccles Harrison Cardiovascular Research and Training Institute (H.L., J.G.L., T.S., J.H.B., F.B.S.), and Department of Bioengineering (J.G.L., F.B.S.), University of Utah, Salt Lake City; and Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD (G.F.T.)
| | - Justin G Lichter
- From the Nora Eccles Harrison Cardiovascular Research and Training Institute (H.L., J.G.L., T.S., J.H.B., F.B.S.), and Department of Bioengineering (J.G.L., F.B.S.), University of Utah, Salt Lake City; and Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD (G.F.T.)
| | - Thomas Seidel
- From the Nora Eccles Harrison Cardiovascular Research and Training Institute (H.L., J.G.L., T.S., J.H.B., F.B.S.), and Department of Bioengineering (J.G.L., F.B.S.), University of Utah, Salt Lake City; and Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD (G.F.T.)
| | - Gordon F Tomaselli
- From the Nora Eccles Harrison Cardiovascular Research and Training Institute (H.L., J.G.L., T.S., J.H.B., F.B.S.), and Department of Bioengineering (J.G.L., F.B.S.), University of Utah, Salt Lake City; and Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD (G.F.T.)
| | - John H B Bridge
- From the Nora Eccles Harrison Cardiovascular Research and Training Institute (H.L., J.G.L., T.S., J.H.B., F.B.S.), and Department of Bioengineering (J.G.L., F.B.S.), University of Utah, Salt Lake City; and Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD (G.F.T.)
| | - Frank B Sachse
- From the Nora Eccles Harrison Cardiovascular Research and Training Institute (H.L., J.G.L., T.S., J.H.B., F.B.S.), and Department of Bioengineering (J.G.L., F.B.S.), University of Utah, Salt Lake City; and Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD (G.F.T.).
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19
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Pfeiffer ER, Tangney JR, Omens JH, McCulloch AD. Biomechanics of cardiac electromechanical coupling and mechanoelectric feedback. J Biomech Eng 2014; 136:021007. [PMID: 24337452 DOI: 10.1115/1.4026221] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 12/12/2013] [Indexed: 11/08/2022]
Abstract
Cardiac mechanical contraction is triggered by electrical activation via an intracellular calcium-dependent process known as excitation-contraction coupling. Dysregulation of cardiac myocyte intracellular calcium handling is a common feature of heart failure. At the organ scale, electrical dyssynchrony leads to mechanical alterations and exacerbates pump dysfunction in heart failure. A reverse coupling between cardiac mechanics and electrophysiology is also well established. It is commonly referred as cardiac mechanoelectric feedback and thought to be an important contributor to the increased risk of arrhythmia during pathological conditions that alter regional cardiac wall mechanics, including heart failure. At the cellular scale, most investigations of myocyte mechanoelectric feedback have focused on the roles of stretch-activated ion channels, though mechanisms that are independent of ionic currents have also been described. Here we review excitation-contraction coupling and mechanoelectric feedback at the cellular and organ scales, and we identify the need for new multicellular tissue-scale model systems and experiments that can help us to obtain a better understanding of how interactions between electrophysiological and mechanical processes at the cell scale affect ventricular electromechanical interactions at the organ scale in the normal and diseased heart.
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Effect of ion concentration changes in the limited extracellular spaces on sarcolemmal ion transport and Ca2+ turnover in a model of human ventricular cardiomyocyte. Int J Mol Sci 2013; 14:24271-92. [PMID: 24351816 PMCID: PMC3876110 DOI: 10.3390/ijms141224271] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Revised: 11/12/2013] [Accepted: 11/19/2013] [Indexed: 11/24/2022] Open
Abstract
We have developed a computer model of human cardiac ventricular myocyte (CVM), including t-tubular and cleft spaces with the aim of evaluating the impact of accumulation-depletion of ions in restricted extracellular spaces on transmembrane ion transport and ionic homeostasis in human CVM. The model was based on available data from human CVMs. Under steady state, the effect of ion concentration changes in extracellular spaces on [Ca2+]i-transient was explored as a function of critical fractions of ion transporters in t-tubular membrane (not documented for human CVM). Depletion of Ca2+ and accumulation of K+ occurring in extracellular spaces slightly affected the transmembrane Ca2+ flux, but not the action potential duration (APD90). The [Ca2+]i-transient was reduced (by 2%–9%), depending on the stimulation frequency, the rate of ion exchange between t-tubules and clefts and fractions of ion-transfer proteins in the t-tubular membrane. Under non-steady state, the responses of the model to changes of stimulation frequency were analyzed. A sudden increase of frequency (1–2.5 Hz) caused a temporal decrease of [Ca2+] in both extracellular spaces, a reduction of [Ca2+]i-transient (by 15%) and APD90 (by 13 ms). The results reveal different effects of activity-related ion concentration changes in human cardiac t-tubules (steady-state effects) and intercellular clefts (transient effects) in the modulation of membrane ion transport and Ca2+ turnover.
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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.
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Affiliation(s)
- Ang Guo
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
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Kohl P, Bollensdorff C, Morad M. Progress in Biophysics and Molecular Biology of the Beating Heart. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2012; 110:151-3. [DOI: 10.1016/j.pbiomolbio.2012.08.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Accepted: 08/09/2012] [Indexed: 12/14/2022]
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The zebrafish as a novel animal model to study the molecular mechanisms of mechano-electrical feedback in the heart. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2012; 110:154-65. [PMID: 22835662 DOI: 10.1016/j.pbiomolbio.2012.07.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 07/16/2012] [Indexed: 02/07/2023]
Abstract
Altered mechanical loading of the heart leads to hypertrophy, decompensated heart failure and fatal arrhythmias. However, the molecular mechanisms that link mechanical and electrical dysfunction remain poorly understood. Growing evidence suggest that ventricular electrical remodeling (VER) is a process that can be induced by altered mechanical stress, creating persistent electrophysiological changes that predispose the heart to life-threatening arrhythmias. While VER is clearly a physiological property of the human heart, as evidenced by "T wave memory", it is also thought to occur in a variety of pathological states associated with altered ventricular activation such as bundle branch block, myocardial infarction, and cardiac pacing. Animal models that are currently being used for investigating stretch-induced VER have significant limitations. The zebrafish has recently emerged as an attractive animal model for studying cardiovascular disease and could overcome some of these limitations. Owing to its extensively sequenced genome, high conservation of gene function, and the comprehensive genetic resources that are available in this model, the zebrafish may provide new insights into the molecular mechanisms that drive detrimental electrical remodeling in response to stretch. Here, we have established a zebrafish model to study mechano-electrical feedback in the heart, which combines efficient genetic manipulation with high-precision stretch and high-resolution electrophysiology. In this model, only 90 min of ventricular stretch caused VER and recapitulated key features of VER found previously in the mammalian heart. Our data suggest that the zebrafish model is a powerful platform for investigating the molecular mechanisms underlying mechano-electrical feedback and VER in the heart.
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Dabiri BE, Lee H, Parker KK. A potential role for integrin signaling in mechanoelectrical feedback. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2012; 110:196-203. [PMID: 22819851 DOI: 10.1016/j.pbiomolbio.2012.07.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 07/11/2012] [Indexed: 01/20/2023]
Abstract
Certain forms of heart disease involve gross morphological changes to the myocardium that alter its hemodynamic loading conditions. These changes can ultimately lead to the increased deposition of extracellular matrix (ECM) proteins, such as collagen and fibronectin, which together work to pathologically alter the myocardium's bulk tissue mechanics. In addition to changing the mechanical properties of the heart, this maladaptive remodeling gives rise to changes in myocardium electrical conductivity and synchrony since the tissue's mechanical properties are intimately tied to its electrical characteristics. This phenomenon, called mechanoelectrical coupling (MEC), can render individuals affected by heart disease arrhythmogenic and susceptible to Sudden Cardiac Death (SCD). The underlying mechanisms of MEC have been attributed to various processes, including the action of stretch activated channels and changes in troponin C-Ca(2+) binding affinity. However, changes in the heart post infarction or due to congenital myopathies are also accompanied by shifts in the expression of various molecular components of cardiomyocytes, including the mechanosensitive family of integrin proteins. As transmembrane proteins, integrins mechanically couple the ECM with the intracellular cytoskeleton and have been implicated in mediating ion homeostasis in various cell types, including neurons and smooth muscle. Given evidence of altered integrin expression in the setting of heart disease coupled with the associated increased risk for arrhythmia, we argue in this review that integrin signaling contributes to MEC. In light of the significant mortality associated with arrhythmia and SCD, close examination of all culpable mechanisms, including integrin-mediated MEC, is necessary.
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Affiliation(s)
- Borna E Dabiri
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard University, 29 Oxford St, Pierce Hall 321, Cambridge, MA 02138, USA
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