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Ruud M, Frisk M, Melleby AO, Norseng PA, Mohamed BA, Li J, Aronsen JM, Setterberg IE, Jakubiczka J, van Hout I, Coffey S, Shen X, Nygård S, Lunde IG, Tønnessen T, Jones PP, Sjaastad I, Gullestad L, Toischer K, Dahl CP, Christensen G, Louch WE. Regulation of cardiomyocyte t-tubule structure by preload and afterload: Roles in cardiac compensation and decompensation. J Physiol 2024. [PMID: 38686538 DOI: 10.1113/jp284566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Accepted: 04/02/2024] [Indexed: 05/02/2024] Open
Abstract
Mechanical load is a potent regulator of cardiac structure and function. Although high workload during heart failure is associated with disruption of cardiomyocyte t-tubules and Ca2+ homeostasis, it remains unclear whether changes in preload and afterload may promote adaptive t-tubule remodelling. We examined this issue by first investigating isolated effects of stepwise increases in load in cultured rat papillary muscles. Both preload and afterload increases produced a biphasic response, with the highest t-tubule densities observed at moderate loads, whereas excessively low and high loads resulted in low t-tubule levels. To determine the baseline position of the heart on this bell-shaped curve, mice were subjected to mildly elevated preload or afterload (1 week of aortic shunt or banding). Both interventions resulted in compensated cardiac function linked to increased t-tubule density, consistent with ascension up the rising limb of the curve. Similar t-tubule proliferation was observed in human patients with moderately increased preload or afterload (mitral valve regurgitation, aortic stenosis). T-tubule growth was associated with larger Ca2+ transients, linked to upregulation of L-type Ca2+ channels, Na+-Ca2+ exchanger, mechanosensors and regulators of t-tubule structure. By contrast, marked elevation of cardiac load in rodents and patients advanced the heart down the declining limb of the t-tubule-load relationship. This bell-shaped relationship was lost in the absence of electrical stimulation, indicating a key role of systolic stress in controlling t-tubule plasticity. In conclusion, modest augmentation of workload promotes compensatory increases in t-tubule density and Ca2+ cycling, whereas this adaptation is reversed in overloaded hearts during heart failure progression. KEY POINTS: Excised papillary muscle experiments demonstrated a bell-shaped relationship between cardiomyocyte t-tubule density and workload (preload or afterload), which was only present when muscles were electrically stimulated. The in vivo heart at baseline is positioned on the rising phase of this curve because moderate increases in preload (mice with brief aortic shunt surgery, patients with mitral valve regurgitation) resulted in t-tubule growth. Moderate increases in afterload (mice and patients with mild aortic banding/stenosis) similarly increased t-tubule density. T-tubule proliferation was associated with larger Ca2+ transients, with upregulation of the L-type Ca2+ channel, Na+-Ca2+ exchanger, mechanosensors and regulators of t-tubule structure. By contrast, marked elevation of cardiac load in rodents and patients placed the heart on the declining phase of the t-tubule-load relationship, promoting heart failure progression. The dependence of t-tubule structure on preload and afterload thus enables both compensatory and maladaptive remodelling, in rodents and humans.
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Affiliation(s)
- Marianne Ruud
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K.G. 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
- K.G. Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway
| | - Arne Olav Melleby
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K.G. Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway
| | - Per Andreas Norseng
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K.G. Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway
| | - Belal A Mohamed
- Department of Cardiology and Pneumology, Georg-August-University, Göttingen, Germany
| | - Jia Li
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K.G. Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway
| | - Jan Magnus Aronsen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Ingunn E Setterberg
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K.G. Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway
| | - Joanna Jakubiczka
- Department of Cardiology and Pneumology, Georg-August-University, Göttingen, Germany
| | - Isabelle van Hout
- Department of Physiology, School of Biomedical Sciences and HeartOtago, University of Otago, Dunedin, New Zealand
| | - Sean Coffey
- Department of Medicine and HeartOtago, Dunedin School of Medicine, Dunedin Hospital, Dunedin, New Zealand
| | - Xin Shen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K.G. Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway
| | - Ståle Nygård
- Department of Informatics, University of Oslo, Oslo, Norway
| | - Ida G Lunde
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K.G. Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway
| | - Theis Tønnessen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K.G. Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway
- Department of Cardiothoracic Surgery, Oslo University Hospital, Oslo, Norway
| | - Peter P Jones
- Department of Physiology, School of Biomedical Sciences and HeartOtago, University of Otago, Dunedin, New Zealand
| | - Ivar Sjaastad
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K.G. Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway
| | - Lars Gullestad
- Department of Cardiology, Oslo University Hospital, Oslo, Norway
| | - Karl Toischer
- Department of Cardiology and Pneumology, Georg-August-University, Göttingen, Germany
| | - Cristen P Dahl
- Department of Cardiology, Oslo University Hospital, Oslo, Norway
| | - Geir Christensen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K.G. 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
- K.G. Jebsen Centre for Cardiac Research, University of Oslo, Oslo, Norway
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Janssens JV, Raaijmakers AJA, Koutsifeli P, Weeks KL, Bell JR, Van Eyk JE, Curl CL, Mellor KM, Delbridge LMD. Mechanical loading reveals an intrinsic cardiomyocyte stiffness contribution to diastolic dysfunction in murine cardiometabolic disease. bioRxiv 2024:2024.02.21.581448. [PMID: 38659933 PMCID: PMC11042179 DOI: 10.1101/2024.02.21.581448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Cardiometabolic syndromes including diabetes and obesity are associated with occurrence of heart failure with diastolic dysfunction. There are no specific treatments for diastolic dysfunction and therapies to manage symptoms have limited efficacy. Understanding of the cardiomyocyte origins of diastolic dysfunction is an important priority to identify new therapeutics. The investigative goal was to experimentally define in vitro stiffness (stress/strain) properties of isolated cardiomyocytes derived from rodent hearts exhibiting diastolic dysfunction in vivo in response to dietary induction of cardiometabolic disease. Mice fed a High Fat/Sugar Diet (HFSD vs control) for at least 25 weeks exhibited glucose intolerance, obesity and diastolic dysfunction (echo E/e'). Intact paced cardiomyocytes were functionally investigated in three conditions: non-loaded, loaded and stretched. Mean stiffness of HFSD cardiomyocytes was 70% higher than control. The E/e' doppler ratio for the origin hearts was elevated by 35%. A significant relationship was identified between in vitro cardiomyocyte stiffness and in vivo dysfunction severity. With conversion from non-loaded to loaded condition, the decrement in maximal sarcomere lengthening rate was more accentuated in HFSD cardiomyocytes (vs control). With stretch, the Ca 2+ transient decay time course was prolonged. With transition from 2-4Hz pacing, HFSD cardiomyocyte stiffness was further increased, yet diastolic Ca 2+ rise was 50% less than control. Collectively, these findings demonstrate that a component of cardiac diastolic dysfunction in cardiometabolic disease is derived from intrinsic cardiomyocyte mechanical abnormality. Differential responses to load, stretch and pacing suggest that a previously undescribed alteration in myofilament-Ca 2+ interaction contributes to cardiomyocyte stiffness in cardiometabolic disease. KEY POINTS Understanding cardiomyocyte stiffness components is an important priority for identifying new therapeutics for diastolic dysfunction, a key feature of cardiometabolic disease. In this study cardiac function was measured in vivo (echocardiography) for mice fed a high-fat/sugar diet (HFSD, ≥25weeks) and performance of intact isolated cardiomyocytes derived from the same hearts was measured during pacing under non-loaded, loaded and stretched conditions in vitro . Using a calibrated cardiomyocyte stretch protocol, stiffness (stress/strain) was elevated in HFSD cardiomyocytes in vitro and correlated with diastolic dysfunction (E/e') in vivo . The HFSD cardiomyocyte Ca 2+ transient decay was prolonged in response to stretch, and stiffness was accentuated in response to pacing increase while the rise in diastolic Ca 2+ was attenuated. These findings suggest that stretch-dependent augmentation of the myofilament-Ca 2+ response during diastole partially underlies elevated cardiomyocyte stiffness and diastolic dysfunction of hearts of animals with cardiometabolic disease.
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Chen-Izu Y, Hegyi B, Jian Z, Horvath B, Shaw JA, Banyasz T, Izu LT. INNOVATIVE TECHNIQUES AND NEW INSIGHTS: Studying cardiac ionic currents and action potentials in physiologically relevant conditions. Physiol Mini Rev 2023; 16:22-34. [PMID: 38107545 PMCID: PMC10722976] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Cardiac arrhythmias are associated with various forms of heart diseases. Ventricular arrhythmias present a significant risk for sudden cardiac death. Atrial fibrillations predispose to blood clots leading to stroke and heart attack. Scientists have been developing patch-clamp technology to study ion channels and action potentials (APs) underlying cardiac excitation and arrhythmias. Beyond the traditional patch-clamp techniques, innovative new techniques were developed for studying complex arrhythmia mechanisms. Here we review the recent development of methods including AP-Clamp, Dynamic Clamp, AP-Clamp Sequential Dissection, and Patch-Clamp-in-Gel. These methods provide powerful tools for researchers to decipher how the dynamic systems in excitation-Ca2+ signaling-contraction feedforward and feedback to control cardiac function and how their dysregulations lead to heart diseases.
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Affiliation(s)
- Ye Chen-Izu
- Department of Pharmacology, University of California, Davis, USA
- Department of Biomedical Engineering, University of California, Davis, USA
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, USA
| | - Bence Hegyi
- Department of Pharmacology, University of California, Davis, USA
| | - Zhong Jian
- Department of Pharmacology, University of California, Davis, USA
| | - Balazs Horvath
- Department of Pharmacology, University of California, Davis, USA
- Department of Physiology, University of Debrecen, Hungary
| | - John A. Shaw
- Department of Pharmacology, University of California, Davis, USA
- Department of Aerospace Engineering, University of Michigan, Ann Arbor, USA
| | - Tamas Banyasz
- Department of Pharmacology, University of California, Davis, USA
- Department of Physiology, University of Debrecen, Hungary
| | - Leighton T. Izu
- Department of Pharmacology, University of California, Davis, USA
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Hegyi B, Mira Hernandez J, Ko CY, Hong J, Shen EY, Spencer ER, Smoliarchuk D, Navedo MF, Bers DM, Bossuyt J. Diabetes and Excess Aldosterone Promote Heart Failure With Preserved Ejection Fraction. J Am Heart Assoc 2022; 11:e027164. [PMID: 36416174 PMCID: PMC9851441 DOI: 10.1161/jaha.122.027164] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Background The pathobiology of heart failure with preserved ejection fraction (HFpEF) is still poorly understood, and effective therapies remain limited. Diabetes and mineralocorticoid excess are common and important pathophysiological factors that may synergistically promote HFpEF. The authors aimed to develop a novel animal model of HFpEF that recapitulates key aspects of the complex human phenotype with multiorgan impairments. Methods and Results The authors created a novel HFpEF model combining leptin receptor-deficient db/db mice with a 4-week period of aldosterone infusion. The HFpEF phenotype was assessed using morphometry, echocardiography, Ca2+ handling, and electrophysiology. The sodium-glucose cotransporter-2 inhibitor empagliflozin was then tested for reversing the arrhythmogenic cardiomyocyte phenotype. Continuous aldosterone infusion for 4 weeks in db/db mice induced marked diastolic dysfunction with preserved ejection fraction, cardiac hypertrophy, high levels of B-type natriuretic peptide, and significant extracardiac comorbidities (including severe obesity, diabetes with marked hyperglycemia, pulmonary edema, and vascular dysfunction). Aldosterone or db/db alone induced only a mild diastolic dysfunction without congestion. At the cellular level, cardiomyocyte hypertrophy, prolonged Ca2+ transient decay, and arrhythmogenic action potential remodeling (prolongation, increased short-term variability, delayed afterdepolarizations), and enhanced late Na+ current were observed in aldosterone-treated db/db mice. All of these arrhythmogenic changes were reversed by empagliflozin pretreatment of HFpEF cardiomyocytes. Conclusions The authors conclude that the db/db+aldosterone model may represent a distinct clinical subgroup of HFpEF that has marked hyperglycemia, obesity, and increased arrhythmia risk. This novel HFpEF model can be useful in future therapeutic testing and should provide unique opportunities to better understand disease pathobiology.
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Affiliation(s)
- Bence Hegyi
- Department of PharmacologyUniversity of CaliforniaDavisCA
| | - Juliana Mira Hernandez
- Department of PharmacologyUniversity of CaliforniaDavisCA
- Research Group in Veterinary Medicine (GIVET), School of Veterinary MedicineUniversity Corporation Lasallista (Unilasallista)CaldasAntioquiaColombia
| | | | - Junyoung Hong
- Department of PharmacologyUniversity of CaliforniaDavisCA
| | - Erin Y. Shen
- Department of PharmacologyUniversity of CaliforniaDavisCA
| | | | | | | | - Donald M. Bers
- Department of PharmacologyUniversity of CaliforniaDavisCA
| | - Julie Bossuyt
- Department of PharmacologyUniversity of CaliforniaDavisCA
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Alim CC, Ko CY, Mira Hernandez J, Shen EY, Baidar S, Chen‐Izu Y, Bers DM, Bossuyt J. Nitrosylation of cardiac CaMKII at Cys290 mediates mechanical afterload-induced increases in Ca 2+ transient and Ca 2+ sparks. J Physiol 2022; 600:4865-4879. [PMID: 36227145 PMCID: PMC9827875 DOI: 10.1113/jp283427] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 09/30/2022] [Indexed: 01/12/2023] Open
Abstract
Cardiac mechanical afterload induces an intrinsic autoregulatory increase in myocyte Ca2+ dynamics and contractility to enhance contraction (known as the Anrep effect or slow force response). Our prior work has implicated both nitric oxide (NO) produced by NO synthase 1 (NOS1) and calcium/calmodulin-dependent protein kinase II (CaMKII) activity as required mediators of this form of mechano-chemo-transduction. To test whether a single S-nitrosylation site on CaMKIIδ (Cys290) mediates enhanced sarcoplasmic reticulum Ca2+ leak and afterload-induced increases in sarcoplasmic reticulum (SR) Ca2+ uptake and release, we created a novel CRISPR-based CaMKIIδ knock-in (KI) mouse with a Cys to Ala mutation at C290. These CaMKIIδ-C290A-KI mice exhibited normal cardiac morphometry and function, as well as basal myocyte Ca2+ transients (CaTs) and β-adrenergic responses. However, the NO donor S-nitrosoglutathione caused an acute increased Ca2+ spark frequency in wild-type (WT) myocytes that was absent in the CaMKIIδ-C290A-KI myocytes. Using our cell-in-gel system to exert multiaxial three-dimensional mechanical afterload on myocytes during contraction, we found that WT myocytes exhibited an afterload-induced increase in Ca2+ sparks and Ca2+ transient amplitude and rate of decline. These afterload-induced effects were prevented in both cardiac-specific CaMKIIδ knockout and point mutant CaMKIIδ-C290A-KI myocytes. We conclude that CaMKIIδ activation by S-nitrosylation at the C290 site is essential in mediating the intrinsic afterload-induced enhancement of myocyte SR Ca2+ uptake, release and Ca2+ transient amplitude (the Anrep effect). The data also indicate that NOS1 activation is upstream of S-nitrosylation at C290 of CaMKII, and that this molecular mechano-chemo-transduction pathway is beneficial in allowing the heart to increase contractility to limit the reduction in stroke volume when aortic pressure (afterload) is elevated. KEY POINTS: A novel CRISPR-based CaMKIIδ knock-in mouse was created in which kinase activation by S-nitrosylation at Cys290 (C290A) is prevented. How afterload affects Ca2+ signalling was measured in cardiac myocytes that were embedded in a hydrogel that imposes a three-dimensional afterload. This mechanical afterload induced an increase in Ca2+ transient amplitude and decay in wild-type myocytes, but not in cardiac-specific CaMKIIδ knockout or C290A knock-in myocytes. The CaMKIIδ-C290 S-nitrosylation site is essential for the afterload-induced enhancement of Ca2+ transient amplitude and Ca2+ sparks.
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Affiliation(s)
- Chidera C. Alim
- Department of PharmacologyUniversity of CaliforniaDavisCAUSA
| | | | - Juliana Mira Hernandez
- Department of PharmacologyUniversity of CaliforniaDavisCAUSA,Research Group in Veterinary MedicineSchool of Veterinary MedicineUniversity Corporation LasallistaCaldasAntioquiaColombia
| | - Erin Y. Shen
- Department of PharmacologyUniversity of CaliforniaDavisCAUSA
| | - Sonya Baidar
- Department of PharmacologyUniversity of CaliforniaDavisCAUSA
| | - Ye Chen‐Izu
- Department of PharmacologyUniversity of CaliforniaDavisCAUSA,Department of Biomedical EngineeringUniversity of CaliforniaDavisCAUSA,Department of Internal Medicine/CardiologyUniversity of CaliforniaDavisCAUSA
| | - Donald M. Bers
- Department of PharmacologyUniversity of CaliforniaDavisCAUSA
| | - Julie Bossuyt
- Department of PharmacologyUniversity of CaliforniaDavisCAUSA
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Kazemi-Lari MA, Shimkunas R, Jian Z, Hegyi B, Izu L, Shaw JA, Wineman AS, Chen-Izu Y. Modeling Cardiomyocyte Mechanics and Autoregulation of Contractility by Mechano-Chemo-Transduction Feedback. iScience 2022; 25:104667. [PMID: 35860762 PMCID: PMC9289640 DOI: 10.1016/j.isci.2022.104667] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2022] [Revised: 05/22/2022] [Accepted: 06/20/2022] [Indexed: 11/30/2022] Open
Abstract
The heart pumps blood into circulation against vascular resistance and actively regulates the contractile force to compensate for mechanical load changes. Our experimental data show that cardiomyocytes have a mechano-chemo-transduction (MCT) mechanism that increases intracellular Ca2+ transient to enhance contractility in response to increased mechanical load. This study advances the cardiac excitation- Ca2+ signaling-contraction (E-C) coupling model on conceptual and technical fronts. First, we developed analytical and computational models to perform 3-dimensional mechanical analysis of cardiomyocytes contracting in a viscoelastic medium under mechanical load. Next, we proposed an MCT feedback loop in the E-C coupling dynamic system to shift the feedforward paradigm of cardiac E-C coupling to an autoregulation model. Our combined modeling and experimental studies reveal that MCT enables autoregulation of E-C coupling and contractility in single cardiomyocytes, which underlies the heart’s intrinsic autoregulation in compensatory response to load changes in order to maintain the stroke volume and cardiac output. Excitation-contraction (E-C) coupling has mechano-chemo-transduction (MCT) feedback MCT feedback enables autoregulation of E-C coupling when contracting under load Models for 3D mechanical analyses of cardiomyocytes contraction Shifts the paradigm of cardiac E-C coupling from feedforward to autoregulation model
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7
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Khokhlova A, Solovyova O, Kohl P, Peyronnet R. Single cardiomyocytes from papillary muscles show lower preload-dependent activation of force compared to cardiomyocytes from the left ventricular free wall. J Mol Cell Cardiol 2022. [DOI: 10.1016/j.yjmcc.2022.02.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 02/05/2022] [Accepted: 02/22/2022] [Indexed: 01/21/2023]
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Abstract
The sarcomere is the fundamental structural and functional unit of striated muscle and is directly responsible for most of its mechanical properties. The sarcomere generates active or contractile forces and determines the passive or elastic properties of striated muscle. In the heart, mutations in sarcomeric proteins are responsible for the majority of genetically inherited cardiomyopathies. Here, we review the major determinants of cardiac sarcomere mechanics including the key structural components that contribute to active and passive tension. We dissect the molecular and structural basis of active force generation, including sarcomere composition, structure, activation, and relaxation. We then explore the giant sarcomere-resident protein titin, the major contributor to cardiac passive tension. We discuss sarcomere dynamics exemplified by the regulation of titin-based stiffness and the titin life cycle. Finally, we provide an overview of therapeutic strategies that target the sarcomere to improve cardiac contraction and filling.
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Hegyi B, Shimkunas R, Jian Z, Izu LT, Bers DM, Chen-Izu Y. Mechanoelectric coupling and arrhythmogenesis in cardiomyocytes contracting under mechanical afterload in a 3D viscoelastic hydrogel. Proc Natl Acad Sci U S A 2021; 118:e2108484118. [PMID: 34326268 PMCID: PMC8346795 DOI: 10.1073/pnas.2108484118] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The heart pumps blood against the mechanical afterload from arterial resistance, and increased afterload may alter cardiac electrophysiology and contribute to life-threatening arrhythmias. However, the cellular and molecular mechanisms underlying mechanoelectric coupling in cardiomyocytes remain unclear. We developed an innovative patch-clamp-in-gel technology to embed cardiomyocytes in a three-dimensional (3D) viscoelastic hydrogel that imposes an afterload during regular myocyte contraction. Here, we investigated how afterload affects action potentials, ionic currents, intracellular Ca2+ transients, and cell contraction of adult rabbit ventricular cardiomyocytes. We found that afterload prolonged action potential duration (APD), increased transient outward K+ current, decreased inward rectifier K+ current, and increased L-type Ca2+ current. Increased Ca2+ entry caused enhanced Ca2+ transients and contractility. Moreover, elevated afterload led to discordant alternans in APD and Ca2+ transient. Ca2+ alternans persisted under action potential clamp, indicating that the alternans was Ca2+ dependent. Furthermore, all these afterload effects were significantly attenuated by inhibiting nitric oxide synthase 1 (NOS1). Taken together, our data reveal a mechano-chemo-electrotransduction (MCET) mechanism that acutely transduces afterload through NOS1-nitric oxide signaling to modulate the action potential, Ca2+ transient, and contractility. The MCET pathway provides a feedback loop in excitation-Ca2+ signaling-contraction coupling, enabling autoregulation of contractility in cardiomyocytes in response to afterload. This MCET mechanism is integral to the individual cardiomyocyte (and thus the heart) to intrinsically enhance its contractility in response to the load against which it has to do work. While this MCET is largely compensatory for physiological load changes, it may also increase susceptibility to arrhythmias under excessive pathological loading.
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Affiliation(s)
- Bence Hegyi
- Department of Pharmacology, University of California, Davis, CA 95616
| | - Rafael Shimkunas
- Department of Pharmacology, University of California, Davis, CA 95616
- Department of Biomedical Engineering, University of California, Davis, CA 95616
| | - Zhong Jian
- Department of Pharmacology, University of California, Davis, CA 95616
| | - Leighton T Izu
- Department of Pharmacology, University of California, Davis, CA 95616
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, CA 95616
| | - Ye Chen-Izu
- Department of Pharmacology, University of California, Davis, CA 95616;
- Department of Biomedical Engineering, University of California, Davis, CA 95616
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, CA 95616
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10
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Kazemi-Lari MA, Shaw JA, Wineman AS, Shimkunas R, Jian Z, Hegyi B, Izu L, Chen-Izu Y. A viscoelastic Eshelby inclusion model and analysis of the Cell-in-Gel system. Int J Eng Sci 2021; 165:103489. [PMID: 34629507 PMCID: PMC8500226 DOI: 10.1016/j.ijengsci.2021.103489] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We develop a viscoelastic generalization of the elastic Eshelby inclusion solution, where the inclusion and surrounding matrix are two different viscoelastic solids and the inclusion's eigenstrain is a time-periodic oscillatory input. The solution exploits the Correspondence Principle of Linear Viscoelasticity and a Discrete Fourier Transform to efficiently capture the steady-state oscillatory behavior of the 3-D mechanical fields. The approach is illustrated here in the context of the recently-developed in vitro Cell-in-Gel system, where an isolated live cardiomyocyte (the inclusion) is paced to contract periodically within a soft hydrogel (the matrix), for the purpose of studying the effect of mechanical load on biochemical signals that regulate contractility. The addition of viscoelasticity improves the fidelity of our previous elastic Eshelby inclusion analysis of the Cell-in-Gel system by accounting for the time-varying fields and the resulting hysteresis and dissipated mechanical energy. This mathematical model is used to study the parametric sensitivities of the relative stiffness of the inclusion, the inclusion's aspect ratio (slenderness), and the cross-link density of the hydrogel matrix.
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Affiliation(s)
| | - John A Shaw
- Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI 48109, USA
| | - Alan S Wineman
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
| | - Rafael Shimkunas
- Pharmacology and Biomedical Engineering Departments, University of California, Davis, CA 95616, USA
| | - Zhong Jian
- Pharmacology and Biomedical Engineering Departments, University of California, Davis, CA 95616, USA
| | - Bence Hegyi
- Pharmacology and Biomedical Engineering Departments, University of California, Davis, CA 95616, USA
| | - Leighton Izu
- Pharmacology and Biomedical Engineering Departments, University of California, Davis, CA 95616, USA
| | - Ye Chen-Izu
- Pharmacology and Biomedical Engineering Departments, University of California, Davis, CA 95616, USA
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Izu L, Shimkunas R, Jian Z, Hegyi B, Kazemi-Lari M, Baker A, Shaw J, Banyasz T, Chen-Izu Y. Emergence of Mechano-Sensitive Contraction Autoregulation in Cardiomyocytes. Life (Basel) 2021; 11:503. [PMID: 34072584 PMCID: PMC8227646 DOI: 10.3390/life11060503] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 05/26/2021] [Accepted: 05/27/2021] [Indexed: 12/24/2022] Open
Abstract
The heart has two intrinsic mechanisms to enhance contractile strength that compensate for increased mechanical load to help maintain cardiac output. When vascular resistance increases the ventricular chamber initially expands causing an immediate length-dependent increase of contraction force via the Frank-Starling mechanism. Additionally, the stress-dependent Anrep effect slowly increases contraction force that results in the recovery of the chamber volume towards its initial state. The Anrep effect poses a paradox: how can the cardiomyocyte maintain higher contractility even after the cell length has recovered its initial length? Here we propose a surface mechanosensor model that enables the cardiomyocyte to sense different mechanical stresses at the same mechanical strain. The cell-surface mechanosensor is coupled to a mechano-chemo-transduction feedback mechanism involving three elements: surface mechanosensor strain, intracellular Ca2+ transient, and cell strain. We show that in this simple yet general system, contractility autoregulation naturally emerges, enabling the cardiomyocyte to maintain contraction amplitude despite changes in a range of afterloads. These nontrivial model predictions have been experimentally confirmed. Hence, this model provides a new conceptual framework for understanding the contractility autoregulation in cardiomyocytes, which contributes to the heart's intrinsic adaptivity to mechanical load changes in health and diseases.
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Affiliation(s)
- Leighton Izu
- Department of Pharmacology, University of California, Davis, CA 95616, USA; (R.S.); (Z.J.); (B.H.); (M.K.-L.); (T.B.); (Y.C.-I.)
| | - Rafael Shimkunas
- Department of Pharmacology, University of California, Davis, CA 95616, USA; (R.S.); (Z.J.); (B.H.); (M.K.-L.); (T.B.); (Y.C.-I.)
| | - Zhong Jian
- Department of Pharmacology, University of California, Davis, CA 95616, USA; (R.S.); (Z.J.); (B.H.); (M.K.-L.); (T.B.); (Y.C.-I.)
| | - Bence Hegyi
- Department of Pharmacology, University of California, Davis, CA 95616, USA; (R.S.); (Z.J.); (B.H.); (M.K.-L.); (T.B.); (Y.C.-I.)
| | - Mohammad Kazemi-Lari
- Department of Pharmacology, University of California, Davis, CA 95616, USA; (R.S.); (Z.J.); (B.H.); (M.K.-L.); (T.B.); (Y.C.-I.)
| | - Anthony Baker
- Department of Medicine, University of California, San Francisco, CA 94121, USA;
| | - John Shaw
- Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI 48109, USA;
| | - Tamas Banyasz
- Department of Pharmacology, University of California, Davis, CA 95616, USA; (R.S.); (Z.J.); (B.H.); (M.K.-L.); (T.B.); (Y.C.-I.)
- Department of Physiology, University of Debrecen, 4032 Debrecen, Hungary
| | - Ye Chen-Izu
- Department of Pharmacology, University of California, Davis, CA 95616, USA; (R.S.); (Z.J.); (B.H.); (M.K.-L.); (T.B.); (Y.C.-I.)
- Department of Biomedical Engineering, University of California, Davis, CA 95616, USA
- Department of Internal Medicine, Division of Cardiology, University of California, Davis, CA 95616, USA
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