1
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Schuftan D, Kooh YKG, Guo J, Sun Y, Aryan L, Stottlemire B, Berkland C, Genin GM, Huebsch N. Dynamic control of contractile resistance to iPSC-derived micro-heart muscle arrays. J Biomed Mater Res A 2024; 112:534-548. [PMID: 37952251 PMCID: PMC10922390 DOI: 10.1002/jbm.a.37642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 09/25/2023] [Accepted: 10/24/2023] [Indexed: 11/14/2023]
Abstract
Many types of cardiovascular disease are linked to the mechanical forces placed on the heart. However, our understanding of how mechanical forces exactly affect the cellular biology of the heart remains incomplete. In vitro models based on cardiomyocytes derived from human induced pluripotent stem cells (iPSC-CM) enable researchers to develop medium to high-throughput systems to study cardiac mechanobiology at the cellular level. Previous models have been developed to enable the study of mechanical forces, such as cardiac afterload. However, most of these models require exogenous extracellular matrix (ECM) to form cardiac tissues. Recently, a system was developed to simulate changes in afterload by grafting ECM-free micro-heart muscle arrays to elastomeric substrates of discrete stiffnesses. In the present study, we extended this system by combining the elastomer-grafted tissue arrays with a magnetorheological elastomeric substrate. This system allows iPSC-CM based micro-heart muscle arrays to experience dynamic changes in contractile resistance to mimic dynamically altered afterload. Acute changes in substrate stiffness led to acute changes in the calcium dynamics and contractile forces, illustrating the system's ability to dynamically elicit changes in tissue mechanics by dynamically changing contractile resistance.
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Affiliation(s)
- David Schuftan
- Department of Biomedical Engineering, McKelvey School of Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Yasaman Kargar Gaz Kooh
- Institute of Materials Science & Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Jingxuan Guo
- Department of Mechanical Engineering & Materials Science, McKelvey School of Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Yuwen Sun
- Institute of Materials Science & Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Lavanya Aryan
- Department of Biomedical Engineering, McKelvey School of Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Bryce Stottlemire
- Department of Chemical and Petroleum Engineering, Bioengineering Graduate Program, University of Kansas, Lawrence, Kansas, USA
| | - Cory Berkland
- Department of Chemical and Petroleum Engineering, Bioengineering Graduate Program, University of Kansas, Lawrence, Kansas, USA
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas, USA
| | - Guy M. Genin
- Department of Mechanical Engineering & Materials Science, McKelvey School of Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
- NSF Center for Engineering Mechanobiology, St. Louis, Missouri, USA
| | - Nathaniel Huebsch
- Department of Biomedical Engineering, McKelvey School of Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
- NSF Center for Engineering Mechanobiology, St. Louis, Missouri, USA
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2
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Hanft LM, Fitzsimons DP, Hacker TA, Moss RL, McDonald KS. Cardiac MyBP-C phosphorylation regulates the Frank-Starling relationship in murine hearts. J Gen Physiol 2021; 153:e202012770. [PMID: 33646280 PMCID: PMC7927661 DOI: 10.1085/jgp.202012770] [Citation(s) in RCA: 4] [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: 09/25/2020] [Revised: 01/04/2021] [Accepted: 01/26/2021] [Indexed: 01/08/2023] Open
Abstract
The Frank-Starling relationship establishes that elevated end-diastolic volume progressively increases ventricular pressure and stroke volume in healthy hearts. The relationship is modulated by a number of physiological inputs and is often depressed in human heart failure. Emerging evidence suggests that cardiac myosin-binding protein-C (cMyBP-C) contributes to the Frank-Starling relationship. We measured contractile properties at multiple levels of structural organization to determine the role of cMyBP-C and its phosphorylation in regulating (1) the sarcomere length dependence of power in cardiac myofilaments and (2) the Frank-Starling relationship in vivo. We compared transgenic mice expressing wild-type cMyBP-C on the null background, which have ∼50% phosphorylated cMyBP-C (Controls), to transgenic mice lacking cMyBP-C (KO) and to mice expressing cMyBP-C that have serine-273, -282, and -302 mutated to aspartate (cMyBP-C t3SD) or alanine (cMyBP-C t3SA) on the null background to mimic either constitutive PKA phosphorylation or nonphosphorylated cMyBP-C, respectively. We observed a continuum of length dependence of power output in myocyte preparations. Sarcomere length dependence of power progressively increased with a rank ordering of cMyBP-C KO = cMyBP-C t3SA < Control < cMyBP-C t3SD. Length dependence of myofilament power translated, at least in part, to hearts, whereby Frank-Starling relationships were steepest in cMyBP-C t3SD mice. The results support the hypothesis that cMyBP-C and its phosphorylation state tune sarcomere length dependence of myofibrillar power, and these regulatory processes translate across spatial levels of myocardial organization to control beat-to-beat ventricular performance.
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Affiliation(s)
- Laurin M. Hanft
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO
| | - Daniel P. Fitzsimons
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI
| | - Timothy A. Hacker
- Department of Medicine, University of Wisconsin-Madison, Madison, WI
| | - Richard L. Moss
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI
| | - Kerry S. McDonald
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO
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3
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Guo J, Simmons DW, Ramahdita G, Munsell MK, Oguntuyo K, Kandalaft B, Rios B, Pear M, Schuftan D, Jiang H, Lake SP, Genin GM, Huebsch N. Elastomer-Grafted iPSC-Derived Micro Heart Muscles to Investigate Effects of Mechanical Loading on Physiology. ACS Biomater Sci Eng 2020; 7:2973-2989. [PMID: 34275296 DOI: 10.1021/acsbiomaterials.0c00318] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Mechanical loading plays a critical role in cardiac pathophysiology. Engineered heart tissues derived from human induced pluripotent stem cells (iPSCs) allow rigorous investigations of the molecular and pathophysiological consequences of mechanical cues. However, many engineered heart muscle models have complex fabrication processes and require large cell numbers, making it difficult to use them together with iPSC-derived cardiomyocytes to study the influence of mechanical loading on pharmacology and genotype-phenotype relationships. To address this challenge, simple and scalable iPSC-derived micro-heart-muscle arrays (μHM) have been developed. "Dog-bone-shaped" molds define the boundary conditions for tissue formation. Here, we extend the μHM model by forming these tissues on elastomeric substrates with stiffnesses spanning from 5 to 30 kPa. Tissue assembly was achieved by covalently grafting fibronectin to the substrate. Compared to μHM formed on plastic, elastomer-grafted μHM exhibited a similar gross morphology, sarcomere assembly, and tissue alignment. When these tissues were formed on substrates with different elasticity, we observed marked shifts in contractility. Increased contractility was correlated with increases in calcium flux and a slight increase in cell size. This afterload-enhanced μHM system enables mechanical control of μHM and real-time tissue traction force microscopy for cardiac physiology measurements, providing a dynamic tool for studying pathophysiology and pharmacology.
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Affiliation(s)
- Jingxuan Guo
- Department of Mechanical Engineering and Materials Science, Washington University in Saint Louis, University City, St. Louis, Missouri 63130, United States
| | - Daniel W Simmons
- Department of Biomedical Engineering, Washington University in Saint Louis, University City, St. Louis, Missouri 63130, United States.,NSF Science and Technology Center for Engineering Mechanobiology, McKelvey School of Engineering, 1 Brookings Dr., St. Louis, Missouri 63130, United States
| | - Ghiska Ramahdita
- Department of Mechanical Engineering and Materials Science, Washington University in Saint Louis, University City, St. Louis, Missouri 63130, United States.,NSF Science and Technology Center for Engineering Mechanobiology, McKelvey School of Engineering, 1 Brookings Dr., St. Louis, Missouri 63130, United States
| | - Mary K Munsell
- Department of Biomedical Engineering, Washington University in Saint Louis, University City, St. Louis, Missouri 63130, United States
| | - Kasoorelope Oguntuyo
- Department of Biomedical Engineering, Washington University in Saint Louis, University City, St. Louis, Missouri 63130, United States
| | - Brennan Kandalaft
- Department of Biomedical Engineering, Washington University in Saint Louis, University City, St. Louis, Missouri 63130, United States
| | - Brandon Rios
- Department of Biomedical Engineering, Washington University in Saint Louis, University City, St. Louis, Missouri 63130, United States
| | - Missy Pear
- Department of Biomedical Engineering, Washington University in Saint Louis, University City, St. Louis, Missouri 63130, United States
| | - David Schuftan
- Department of Biomedical Engineering, Washington University in Saint Louis, University City, St. Louis, Missouri 63130, United States
| | - Huanzhu Jiang
- Department of Biomedical Engineering, Washington University in Saint Louis, University City, St. Louis, Missouri 63130, United States
| | - Spencer P Lake
- Department of Mechanical Engineering and Materials Science, Washington University in Saint Louis, University City, St. Louis, Missouri 63130, United States
| | - Guy M Genin
- Department of Mechanical Engineering and Materials Science, Washington University in Saint Louis, University City, St. Louis, Missouri 63130, United States.,NSF Science and Technology Center for Engineering Mechanobiology, McKelvey School of Engineering, 1 Brookings Dr., St. Louis, Missouri 63130, United States
| | - Nathaniel Huebsch
- Department of Biomedical Engineering, Washington University in Saint Louis, University City, St. Louis, Missouri 63130, United States.,NSF Science and Technology Center for Engineering Mechanobiology, McKelvey School of Engineering, 1 Brookings Dr., St. Louis, Missouri 63130, United States.,Center for Cardiovascular Research, Center for Regenerative Medicine, Center for Investigation of Membrane Excitability Diseases, Washington University in Saint Louis, University City, St. Louis, Missouri 63130, United States
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4
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Long F, Wang Q, Yang D, Zhu M, Wang J, Zhu Y, Liu X. Targeting JMJD3 histone demethylase mediates cardiac fibrosis and cardiac function following myocardial infarction. Biochem Biophys Res Commun 2020; 528:671-677. [PMID: 32513540 DOI: 10.1016/j.bbrc.2020.05.115] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 05/17/2020] [Indexed: 01/19/2023]
Abstract
Myocardial fibrosis is the pathological consequence of injury-induced fibroblastto-myofibroblast transition, resulting in increased stiffness and diminished cardiac function. Histone modification has been shown to play an important role in the pathogenesis of cardiac fibrosis. Here, we identified H3K27me3 demethylase JMJD3/KDM6B promotes cardiac fibrosis via regulation of fibrogenic pathways. Using neonatal rat cardiac fibroblasts (NRCF), we show that the expression of endogenous JMJD3 is induced by angiotensin II (Ang II), while the principle extracellular matrix (ECM) such as fibronectin, CTGF, collagen I and III are increased. We find that JMJD3 inhibition markedly enhances the suppressive mark (H3K27me3) at the beta (β)-catenin promoter in activated cardiac fibroblasts, and then substantially decreases expression of fibrogenic gene. Both inhibition of β-catenin-mediated transcription with ICG-001 and genetic loss of β-catenin can prevent Ang II-induced ECM deposition. Most importantly, in vivo inhibition of JMJD3 rescues myocardial ischemia-induced cardiac fibrosis and cardiac dysfunction. Collectively, our findings are the first to report a novel role of histone demethylase JMJD3 in the pro-fibrotic cardiac fibroblast phenotype, pharmacological targeting of JMJD3 might represent a promising therapeutic approach for the treatment of human cardiac fibrosis and other fibrotic diseases.
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Affiliation(s)
- Fen Long
- Department of Pharmacology, School of Pharmacy, Human Phenome Institute, Fudan University, Shanghai, 201203, PR China
| | - Qing Wang
- Department of Pharmacology, School of Pharmacy, Human Phenome Institute, Fudan University, Shanghai, 201203, PR China
| | - Di Yang
- Department of Pharmacology, School of Pharmacy, Human Phenome Institute, Fudan University, Shanghai, 201203, PR China
| | - Menglin Zhu
- Department of Pharmacology, School of Pharmacy, Human Phenome Institute, Fudan University, Shanghai, 201203, PR China
| | - Jinghuan Wang
- Department of Pharmacology, School of Pharmacy, Human Phenome Institute, Fudan University, Shanghai, 201203, PR China
| | - YiZhun Zhu
- Department of Pharmacology, School of Pharmacy, Human Phenome Institute, Fudan University, Shanghai, 201203, PR China; State Key Laboratory of Quality Research in Chinese Medicine and School of Pharmacy, Macau University of Science and Technology, Macau, PR China
| | - Xinhua Liu
- Department of Pharmacology, School of Pharmacy, Human Phenome Institute, Fudan University, Shanghai, 201203, PR China.
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5
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Helms AS, Tang VT, O'Leary TS, Friedline S, Wauchope M, Arora A, Wasserman AH, Smith ED, Lee LM, Wen XW, Shavit JA, Liu AP, Previs MJ, Day SM. Effects of MYBPC3 loss-of-function mutations preceding hypertrophic cardiomyopathy. JCI Insight 2020; 5:133782. [PMID: 31877118 DOI: 10.1172/jci.insight.133782] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 12/10/2019] [Indexed: 12/21/2022] Open
Abstract
Mutations in cardiac myosin binding protein C (MyBP-C, encoded by MYBPC3) are the most common cause of hypertrophic cardiomyopathy (HCM). Most MYBPC3 mutations result in premature termination codons (PTCs) that cause RNA degradation and a reduction of MyBP-C in HCM patient hearts. However, a reduction in MyBP-C has not been consistently observed in MYBPC3-mutant induced pluripotent stem cell cardiomyocytes (iPSCMs). To determine early MYBPC3 mutation effects, we used patient and genome-engineered iPSCMs. iPSCMs with frameshift mutations were compared with iPSCMs with MYBPC3 promoter and translational start site deletions, revealing that allelic loss of function is the primary inciting consequence of mutations causing PTCs. Despite a reduction in wild-type mRNA in all heterozygous iPSCMs, no reduction in MyBP-C protein was observed, indicating protein-level compensation through what we believe is a previously uncharacterized mechanism. Although homozygous mutant iPSCMs exhibited contractile dysregulation, heterozygous mutant iPSCMs had normal contractile function in the context of compensated MyBP-C levels. Agnostic RNA-Seq analysis revealed differential expression in genes involved in protein folding as the only dysregulated gene set. To determine how MYBPC3-mutant iPSCMs achieve compensated MyBP-C levels, sarcomeric protein synthesis and degradation were measured with stable isotope labeling. Heterozygous mutant iPSCMs showed reduced MyBP-C synthesis rates but a slower rate of MyBP-C degradation. These findings indicate that cardiomyocytes have an innate capacity to attain normal MyBP-C stoichiometry despite MYBPC3 allelic loss of function due to truncating mutations. Modulating MyBP-C degradation to maintain MyBP-C protein levels may be a novel treatment approach upstream of contractile dysfunction for HCM.
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Affiliation(s)
- Adam S Helms
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Vi T Tang
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Thomas S O'Leary
- Department of Molecular Physiology & Biophysics, University of Vermont, Burlington, Vermont, USA
| | - Sabrina Friedline
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Mick Wauchope
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Akul Arora
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | | | - Eric D Smith
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | | | | | | | - Allen P Liu
- Mechanical Engineering.,Biophysics, University of Michigan, Ann Arbor, Michigan, USA
| | - Michael J Previs
- Department of Molecular Physiology & Biophysics, University of Vermont, Burlington, Vermont, USA
| | - Sharlene M Day
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan, USA.,Departments of Molecular and Integrative Physiology
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6
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Li S, Li S, Hao X, Zhang Y, Deng W. Perindopril and a Galectin-3 Inhibitor Improve Ischemic Heart Failure in Rabbits by Reducing Gal-3 Expression and Myocardial Fibrosis. Front Physiol 2019; 10:267. [PMID: 30967790 PMCID: PMC6438875 DOI: 10.3389/fphys.2019.00267] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2018] [Accepted: 02/28/2019] [Indexed: 11/13/2022] Open
Abstract
Objective: Ventricular remodeling is considered the basis of heart failure and is involved in myocardial fibrosis. This study aimed to assess perindopril and a galectin-3 inhibitor (modified citrus pectin, MCP) for their effects on ventricular remodeling and myocardial fibrosis in rabbits with ischemic heart failure. Methods: Rabbits were divided into sham, heart failure (model), MCP, and perindopril groups, respectively. A rabbit model of ischemic heart failure was established by ligating the anterior descending coronary artery. Then, the rabbits were orally administered MCP, perindopril, or saline (all at 2 ml/kg/d) for 4 weeks. Sham animals only underwent open heart surgery without further treatment. After 4 weeks, cardiac function was examined by ultrasound, and myocardial Gal-3, collagen type I, and collagen type III expression was assessed, at the gene and protein levels, by real-time PCR and Western-Blot, respectively; serum Gal-3 was detected by ELISA, and fibrosis in the infarct zone was evaluated by H&E and Masson staining. Results: In model animals, myocardial Gal-3, collagen type I, and collagen type III gene and protein expression levels were increased compared with control values, as well as serum Gal-3 amounts. Treatment with perindopril and MCP significantly alleviated the above effects, with no significant differences between the treatment groups. Pathological analyses showed that compared with model animals, treatment with MCP or perindopril resulted in relatively neatly arranged myocardial cells in the infarct zone, with significantly decreased fibrosis. Conclusion: Perindopril and the galectin-3 inhibitor MCP comparably improve ischemic heart failure in rabbits, by downregulating Gal-3 and reducing myocardial fibrosis.
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Affiliation(s)
- Sha Li
- Department of Examination Center, Hebei General Hospital, Shijiazhuang, China
| | - Shuren Li
- Department of Cardiovascular Division 1, Hebei General Hospital, Shijiazhuang, China
| | - Xiao Hao
- Department of Cardiovascular Division 1, Hebei General Hospital, Shijiazhuang, China
| | - Yuehua Zhang
- Department of Cardiovascular Division 1, Hebei General Hospital, Shijiazhuang, China
| | - Wenhao Deng
- Department of Cardiovascular Division 1, Hebei General Hospital, Shijiazhuang, China
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7
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Alvarado FJ, Bos JM, Yuchi Z, Valdivia CR, Hernández JJ, Zhao YT, Henderlong DS, Chen Y, Booher TR, Marcou CA, Van Petegem F, Ackerman MJ, Valdivia HH. Cardiac hypertrophy and arrhythmia in mice induced by a mutation in ryanodine receptor 2. JCI Insight 2019; 5:126544. [PMID: 30835254 DOI: 10.1172/jci.insight.126544] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Hypertrophic cardiomyopathy (HCM) is triggered mainly by mutations in genes encoding sarcomeric proteins, but a significant proportion of patients lack a genetic diagnosis. We identified a novel mutation in the ryanodine receptor 2, RyR2-P1124L, in a patient from a genotype-negative HCM cohort. The aim of this study was to determine whether RyR2-P1124L triggers functional and structural alterations in isolated RyR2 channels and whole hearts. We found that P1124L induces significant conformational changes in the SPRY2 domain of RyR2. Recombinant RyR2-P1124L channels displayed a cytosolic loss-of-function phenotype, which contrasted with a higher sensitivity to luminal [Ca2+], indicating a luminal gain-of-function. Homozygous mice for RyR2-P1124L showed mild cardiac hypertrophy, similar to the human patient. This phenotype, evident at 1 yr of age, was accompanied by an increase in the expression of calmodulin (CaM). P1124L mice also showed higher susceptibility to arrhythmia at 8 mo of age, before the onset of hypertrophy. RyR2-P1124L has a distinct cytosolic loss-of-function and a luminal gain-of-function phenotype. This bifunctionally-divergent behavior triggers arrhythmias and structural cardiac remodeling, and involves overexpression of calmodulin as a potential hypertrophic mediator. This study is relevant to continue elucidating the possible causes of genotype-negative HCM and the role of RyR2 in cardiac hypertrophy.
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Affiliation(s)
- Francisco J Alvarado
- Department of Medicine, Division of Cardiovascular Medicine, and Cardiovascular Research Center, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
| | - J Martijn Bos
- Department of Pediatric and Adolescent Medicine, Division of Pediatric Cardiology, and.,Department of Molecular Pharmacology and Experimental Therapeutics, Windland Smith Rice Sudden Death Genomic Laboratory, Mayo Clinic, Rochester, Minnesota, USA
| | - Zhiguang Yuchi
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, Collaborative Innovation Center of Chemical Science and Engineering, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin, China
| | - Carmen R Valdivia
- Department of Medicine, Division of Cardiovascular Medicine, and Cardiovascular Research Center, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Jonathan J Hernández
- Department of Pediatrics, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
| | | | - Dawn S Henderlong
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Yan Chen
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Talia R Booher
- Department of Medicine, Division of Cardiovascular Medicine, and Cardiovascular Research Center, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Cherisse A Marcou
- Department of Molecular Pharmacology and Experimental Therapeutics, Windland Smith Rice Sudden Death Genomic Laboratory, Mayo Clinic, Rochester, Minnesota, USA
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Michael J Ackerman
- Department of Pediatric and Adolescent Medicine, Division of Pediatric Cardiology, and.,Department of Molecular Pharmacology and Experimental Therapeutics, Windland Smith Rice Sudden Death Genomic Laboratory, Mayo Clinic, Rochester, Minnesota, USA.,Department of Cardiovascular Medicine, Division of Heart Rhythm Services, Mayo Clinic, Rochester, Minnesota, USA
| | - Héctor H Valdivia
- Department of Medicine, Division of Cardiovascular Medicine, and Cardiovascular Research Center, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
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8
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Giles J, Patel JR, Miller A, Iverson E, Fitzsimons D, Moss RL. Recovery of left ventricular function following in vivo reexpression of cardiac myosin binding protein C. J Gen Physiol 2019; 151:77-89. [PMID: 30573635 PMCID: PMC6314388 DOI: 10.1085/jgp.201812238] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 11/27/2018] [Indexed: 01/26/2023] Open
Abstract
The loss of cardiac myosin binding protein C (cMyBP-C) results in left ventricular dilation, cardiac hypertrophy, and impaired ventricular function in both constitutive and conditional cMyBP-C knockout (MYBPC3 null) mice. It remains unclear whether the structural and functional phenotypes expressed in the MYBPC3 null mouse are reversible, which is an important question, since reduced expression of cMyBP-C is an important cause of hypertrophic cardiomyopathy in humans. To investigate this question, we generated a cardiac-specific transgenic mouse model using a Tet-Off inducible system to permit the controlled expression of WT cMyBP-C on the MYBPC3 null background. Functional Tet-Off mice expressing WT cMyBP-C (FT-WT) were generated by crossing tetracycline transactivator mice with responder mice carrying the WT cMyBP-C transgene. Prior to dietary doxycycline administration, cMyBP-C was expressed at normal levels in FT-WT myocardium, which exhibited similar levels of steady-state force and in vivo left ventricular function as WT mice. Introduction of dietary doxycycline for four weeks resulted in a partial knockdown of cMyBP-C expression and commensurate impairment of systolic and diastolic function to levels approaching those observed in MYBPC 3 null mice. Subsequent withdrawal of doxycycline from the diet resulted in the reexpression of cMyBP-C to levels comparable to those observed in WT mice, along with near-complete recovery of in vivo ventricular function. These results show that the cardiac phenotypes associated with MYBPC3 null mice are reversible. Our work also validates the use of the Tet-Off inducible system as a means to study the mechanisms underlying hypertrophic cardiomyopathy.
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Affiliation(s)
- Jasmine Giles
- Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI
| | - Jitandrakumar R Patel
- Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI
- University of Wisconsin Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI
| | - Adam Miller
- Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI
| | - Elizabeth Iverson
- Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI
| | - Daniel Fitzsimons
- Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI
- University of Wisconsin Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI
| | - Richard L Moss
- Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI
- University of Wisconsin Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI
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9
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Allelic imbalance and haploinsufficiency in MYBPC3-linked hypertrophic cardiomyopathy. Pflugers Arch 2018; 471:781-793. [PMID: 30456444 DOI: 10.1007/s00424-018-2226-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 10/04/2018] [Accepted: 10/17/2018] [Indexed: 01/04/2023]
Abstract
Mutations in cardiac myosin binding protein C (MYBPC3) represent the most frequent cause of familial hypertrophic cardiomyopathy (HCM), making up approximately 50% of identified HCM mutations. MYBPC3 is distinct among other sarcomere genes associated with HCM in that truncating mutations make up the vast majority, whereas nontruncating mutations predominant in other sarcomere genes. Several studies using myocardial tissue from HCM patients have found reduced abundance of wild-type MYBPC3 compared to control hearts, suggesting haploinsufficiency of full-length MYBPC3. Further, decreased mutant versus wild-type mRNA and lack of truncated mutant MYBPC3 protein has been demonstrated, highlighting the presence of allelic imbalance. In this review, we will begin by introducing allelic imbalance and haploinsufficiency, highlighting the broad role each plays within the spectrum of human disease. We will subsequently focus on the roles allelic imbalance and haploinsufficiency play within MYBPC3-linked HCM. Finally, we will explore the implications of these findings on future directions of HCM research. An improved understanding of allelic imbalance and haploinsufficiency may help us better understand genotype-phenotype relationships in HCM and develop novel targeted therapies, providing exciting future research opportunities.
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10
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Li J, Gresham KS, Mamidi R, Doh CY, Wan X, Deschenes I, Stelzer JE. Sarcomere-based genetic enhancement of systolic cardiac function in a murine model of dilated cardiomyopathy. Int J Cardiol 2018; 273:168-176. [PMID: 30279005 DOI: 10.1016/j.ijcard.2018.09.073] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 08/27/2018] [Accepted: 09/20/2018] [Indexed: 01/28/2023]
Abstract
Diminished cardiac contractile function is a characteristic feature of dilated cardiomyopathy (DCM) and many other heart failure (HF) causing etiologies. We tested the hypothesis that targeting the sarcomere to increase cardiac contractility can effectively prevent the DCM phenotype in muscle-LIM protein knockout (MLP-/-) mice. The ablation of cardiac myosin binding protein C (MYBPC3-/-) protected the MLP-/- mice from developing the DCM phenotype. We examined the in vivo cardiac function and morphology of the resultant mouse model lacking both MLP and MYBPC3 (DKO) by echocardiography and pressure-volume catheterization and found a significant reduction in hypertrophy, as evidenced by normalized wall thickness and chamber dimensions, and improved systolic function, as evidenced by enhanced ejection fraction (~26% increase compared MLP-/- mice) and rate of pressure development (DKO 7851.0 ± 504.8 vs. MLP-/- 4496.4 ± 196.8 mmHg/s). To investigate the molecular basis for the improved DKO phenotype we performed mechanical experiments in skinned myocardium isolated from WT and the individual KO mice. Skinned myocardium isolated from DKO mice displayed increased Ca2+ sensitivity of force generation, and significantly accelerated rate of cross-bridge detachment (+63% compared to MLP-/-) and rate of XB recruitment (+58% compared to MLP-/-) at submaximal Ca2+ activations. The in vivo and in vitro functional enhancement of DKO mice demonstrates that enhancing the sarcomeric contractility can be cardioprotective in HF characterized by reduced cardiac output, such as in cases of DCM.
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Affiliation(s)
- Jiayang Li
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, United States of America
| | - Kenneth S Gresham
- Center for Translational Medicine, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, United States of America
| | - Ranganath Mamidi
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, United States of America
| | - Chang Yoon Doh
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, United States of America
| | - Xiaoping Wan
- The Heart and Vascular Research Center, Metro Health, Cleveland, OH, United States of America
| | - Isabelle Deschenes
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, United States of America; The Heart and Vascular Research Center, Metro Health, Cleveland, OH, United States of America
| | - Julian E Stelzer
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, United States of America.
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11
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Contractile deficits in engineered cardiac microtissues as a result of MYBPC3 deficiency and mechanical overload. Nat Biomed Eng 2018; 2:955-967. [PMID: 31015724 PMCID: PMC6482859 DOI: 10.1038/s41551-018-0280-4] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 07/20/2018] [Indexed: 12/26/2022]
Abstract
The integration of in vitro cardiac tissue models, human induced pluripotent stem cells (hiPSCs) and genome-editing tools allows for the enhanced interrogation of physiological phenotypes and the recapitulation of disease pathologies. Here, in a cardiac tissue model consisting of filamentous 3D matrices populated with cardiomyocytes (CMs) derived from healthy wild-type hiPSCs (WT hiPSC-CMs) or from isogenic hiPSCs deficient in the sarcomere protein cardiac myosin binding protein C (MYBPC3−/− hiPSC-CMs), we show that the WT microtissues adapted to the mechanical environment with increased contraction force commensurate to matrix stiffness, whereas the MYBPC3−/− microtissues exhibited impaired force-development kinetics regardless of matrix stiffness and deficient contraction force only when grown on matrices with high fiber stiffness. Under mechanical overload, the MYBPC3−/− microtissues had a higher degree of calcium transient abnormalities, and exhibited an accelerated decay of calcium dynamics as well as calcium desensitization, which accelerated when contracting against stiffer fibers. Our findings suggest that MYBPC3 deficiency and the presence of environmental stresses synergistically lead to contractile deficits in the cardiac tissues.
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12
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Farrell ET, Grimes AC, de Lange WJ, Armstrong AE, Ralphe JC. Increased Postnatal Cardiac Hyperplasia Precedes Cardiomyocyte Hypertrophy in a Model of Hypertrophic Cardiomyopathy. Front Physiol 2017; 8:414. [PMID: 28659827 PMCID: PMC5470088 DOI: 10.3389/fphys.2017.00414] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 05/30/2017] [Indexed: 01/17/2023] Open
Abstract
Rationale: Hypertrophic cardiomyopathy (HCM) occurs in ~0.5% of the population and is a leading cause of sudden cardiac death (SCD) in young adults. Cardiomyocyte hypertrophy has been the accepted mechanism for cardiac enlargement in HCM, but the early signaling responsible for initiating hypertrophy is poorly understood. Mutations in cardiac myosin binding protein C (MYBPC3) are among the most common HCM-causing mutations. Ablation of Mybpc3 in an HCM mouse model (cMyBP-C−/−) rapidly leads to cardiomegaly by postnatal day (PND) 9, though hearts are indistinguishable from wild-type (WT) at birth. This model provides a unique opportunity to explore early processes involved in the dramatic postnatal transition to hypertrophy. Methods and Results: We performed microarray analysis, echocardiography, qPCR, immunohistochemistry (IHC), and isolated cardiomyocyte measurements to characterize the perinatal cMyBP-C−/− phenotype before and after overt hypertrophy. cMyBP-C−/− hearts showed elevated cell cycling at PND1 that transitioned to hypertrophy by PND9. An expanded time course revealed that increased cardiomyocyte cycling was associated with elevated heart weight to body weight ratios prior to cellular hypertrophy, suggesting that cell cycling resulted in cardiomyocyte proliferation. Animals heterozygous for the cMyBP-C deletion trended in the direction of the homozygous null, yet did not show increased heart size by PND9. Conclusions: Results indicate that altered regulation of the cell cycling pathway and elevated proliferation precedes hypertrophy in the cMyBP-C−/− HCM model, and suggests that increased cardiomyocyte number contributes to increased heart size in cMyBP-C−/− mice. This pre-hypertrophic period may reflect a unique time during which the commitment to HCM is determined and disease severity is influenced.
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Affiliation(s)
- Emily T Farrell
- Department of Pediatrics, University of Wisconsin School of Medicine and Public HealthMadison, WI, United States
| | - Adrian C Grimes
- Department of Medicine, University of Wisconsin School of Medicine and Public HealthMadison, WI, United States
| | - Willem J de Lange
- Department of Pediatrics, University of Wisconsin School of Medicine and Public HealthMadison, WI, United States
| | - Annie E Armstrong
- Department of Pediatrics, University of Wisconsin School of Medicine and Public HealthMadison, WI, United States
| | - J Carter Ralphe
- Department of Pediatrics, University of Wisconsin School of Medicine and Public HealthMadison, WI, United States
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13
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Nixon BR, Williams AF, Glennon MS, de Feria AE, Sebag SC, Baldwin HS, Becker JR. Alterations in sarcomere function modify the hyperplastic to hypertrophic transition phase of mammalian cardiomyocyte development. JCI Insight 2017; 2:e90656. [PMID: 28239655 DOI: 10.1172/jci.insight.90656] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
It remains unclear how perturbations in cardiomyocyte sarcomere function alter postnatal heart development. We utilized murine models that allowed manipulation of cardiac myosin-binding protein C (MYBPC3) expression at critical stages of cardiac ontogeny to study the response of the postnatal heart to disrupted sarcomere function. We discovered that the hyperplastic to hypertrophic transition phase of mammalian heart development was altered in mice lacking MYBPC3 and this was the critical period for subsequent development of cardiomyopathy. Specifically, MYBPC3-null hearts developed evidence of increased cardiomyocyte endoreplication, which was accompanied by enhanced expression of cell cycle stimulatory cyclins and increased phosphorylation of retinoblastoma protein. Interestingly, this response was self-limited at later developmental time points by an upregulation of the cyclin-dependent kinase inhibitor p21. These results provide valuable insights into how alterations in sarcomere protein function modify postnatal heart development and highlight the potential for targeting cell cycle regulatory pathways to counteract cardiomyopathic stimuli.
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Affiliation(s)
| | | | | | | | - Sara C Sebag
- Department of Medicine, Division of Cardiovascular Medicine
| | - H Scott Baldwin
- Department of Pediatrics, Division of Pediatric Cardiology.,Department of Cellular and Developmental Biology
| | - Jason R Becker
- Department of Medicine, Division of Cardiovascular Medicine.,Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
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14
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Mohamed IA, Krishnamoorthy NT, Nasrallah GK, Da'as SI. The Role of Cardiac Myosin Binding Protein C3 in Hypertrophic Cardiomyopathy-Progress and Novel Therapeutic Opportunities. J Cell Physiol 2017; 232:1650-1659. [PMID: 27731493 DOI: 10.1002/jcp.25639] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 10/07/2016] [Indexed: 11/11/2022]
Abstract
Hypertrophic cardiomyopathy (HCM) is a common autosomal dominant genetic cardiovascular disorder marked by genetic and phenotypic heterogeneity. Mutations in the gene encodes the cardiac myosin-binding protein C, cMYBPC3 is amongst the various sarcomeric genes that are associated with HCM. These mutations produce mutated mRNAs and truncated cMyBP-C proteins. In this review, we will discuss the implications and molecular mechanisms involved in MYBPC3 different mutations. Further, we will highlight the novel targets that can be developed into potential therapeutics for the treatment of HMC. J. Cell. Physiol. 232: 1650-1659, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Iman A Mohamed
- Department of Biomedical Science, Zewail City of Science and Technology, Giza, Egypt
| | - Navaneethakrishnan T Krishnamoorthy
- Division of Experimental Genetics, Sidra Medical and Research Center, Doha, Qatar.,Heart Science Centre, National Heart and Lung Institute, Imperial College London, London, UK
| | - Gheyath K Nasrallah
- Department of Biomedical Science, College of Health Science, Qatar University, Doha, Qatar.,Biomedical Research Center, Qatar University, Doha, Qatar
| | - Sahar I Da'as
- Division of Experimental Genetics, Sidra Medical and Research Center, Doha, Qatar.,Department of Biomedical and Biological Sciences, Hamad Bin Khalifa University, Doha, Qatar
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15
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Zhu S, Guleria RS, Thomas CM, Roth A, Gerilechaogetu F, Kumar R, Dostal DE, Baker KM, Pan J. Loss of myocardial retinoic acid receptor α induces diastolic dysfunction by promoting intracellular oxidative stress and calcium mishandling in adult mice. J Mol Cell Cardiol 2016; 99:100-112. [PMID: 27539860 DOI: 10.1016/j.yjmcc.2016.08.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 08/10/2016] [Accepted: 08/12/2016] [Indexed: 01/09/2023]
Abstract
Retinoic acid receptor (RAR) has been implicated in pathological stimuli-induced cardiac remodeling. To determine whether the impairment of RARα signaling directly contributes to the development of heart dysfunction and the involved mechanisms, tamoxifen-induced myocardial specific RARα deletion (RARαKO) mice were utilized. Echocardiographic and cardiac catheterization studies showed significant diastolic dysfunction after 16wks of gene deletion. However, no significant differences were observed in left ventricular ejection fraction (LVEF), between RARαKO and wild type (WT) control mice. DHE staining showed increased intracellular reactive oxygen species (ROS) generation in the hearts of RARαKO mice. Significantly increased NOX2 (NADPH oxidase 2) and NOX4 levels and decreased SOD1 and SOD2 levels were observed in RARαKO mouse hearts, which were rescued by overexpression of RARα in cardiomyocytes. Decreased SERCA2a expression and phosphorylation of phospholamban (PLB), along with decreased phosphorylation of Akt and Ca2+/calmodulin-dependent protein kinase II δ (CaMKII δ) was observed in RARαKO mouse hearts. Ca2+ reuptake and cardiomyocyte relaxation were delayed by RARα deletion. Overexpression of RARα or inhibition of ROS generation or NOX activation prevented RARα deletion-induced decrease in SERCA2a expression/activation and delayed Ca2+ reuptake. Moreover, the gene and protein expression of RARα was significantly decreased in aged or metabolic stressed mouse hearts. RARα deletion accelerated the development of diastolic dysfunction in streptozotocin (STZ)-induced type 1 diabetic mice or in high fat diet fed mice. In conclusion, myocardial RARα deletion promoted diastolic dysfunction, with a relative preserved LVEF. Increased oxidative stress have an important role in the decreased expression/activation of SERCA2a and Ca2+ mishandling in RARαKO mice, which are major contributing factors in the development of diastolic dysfunction. These data suggest that impairment of cardiac RARα signaling may be a novel mechanism that is directly linked to pathological stimuli-induced diastolic dysfunction.
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Affiliation(s)
- Sen Zhu
- Department of Medicine, College of Medicine, Texas A&M University Health Science Center, Central Texas Veterans Health Care System, Baylor Scott & White Health, Temple, TX, United States
| | - Rakeshwar S Guleria
- Department of Medicine, College of Medicine, Texas A&M University Health Science Center, Central Texas Veterans Health Care System, Baylor Scott & White Health, Temple, TX, United States; Department of Medical Physiology, College of Medicine, Texas A&M University Health Science Center, Central Texas Veterans Health Care System, Baylor Scott & White Health, Temple, TX, United States.
| | - Candice M Thomas
- Department of Medicine, College of Medicine, Texas A&M University Health Science Center, Central Texas Veterans Health Care System, Baylor Scott & White Health, Temple, TX, United States
| | - Amanda Roth
- Department of Medicine, College of Medicine, Texas A&M University Health Science Center, Central Texas Veterans Health Care System, Baylor Scott & White Health, Temple, TX, United States
| | - Fnu Gerilechaogetu
- Department of Medicine, College of Medicine, Texas A&M University Health Science Center, Central Texas Veterans Health Care System, Baylor Scott & White Health, Temple, TX, United States
| | - Rajesh Kumar
- Department of Medicine, College of Medicine, Texas A&M University Health Science Center, Central Texas Veterans Health Care System, Baylor Scott & White Health, Temple, TX, United States; Department of Medical Physiology, College of Medicine, Texas A&M University Health Science Center, Central Texas Veterans Health Care System, Baylor Scott & White Health, Temple, TX, United States
| | - David E Dostal
- Department of Medicine, College of Medicine, Texas A&M University Health Science Center, Central Texas Veterans Health Care System, Baylor Scott & White Health, Temple, TX, United States; Department of Medical Physiology, College of Medicine, Texas A&M University Health Science Center, Central Texas Veterans Health Care System, Baylor Scott & White Health, Temple, TX, United States
| | - Kenneth M Baker
- Department of Medicine, College of Medicine, Texas A&M University Health Science Center, Central Texas Veterans Health Care System, Baylor Scott & White Health, Temple, TX, United States
| | - Jing Pan
- Department of Medicine, College of Medicine, Texas A&M University Health Science Center, Central Texas Veterans Health Care System, Baylor Scott & White Health, Temple, TX, United States; Department of Medical Physiology, College of Medicine, Texas A&M University Health Science Center, Central Texas Veterans Health Care System, Baylor Scott & White Health, Temple, TX, United States.
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16
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Brody MJ, Feng L, Grimes AC, Hacker TA, Olson TM, Kamp TJ, Balijepalli RC, Lee Y. LRRC10 is required to maintain cardiac function in response to pressure overload. Am J Physiol Heart Circ Physiol 2015; 310:H269-78. [PMID: 26608339 DOI: 10.1152/ajpheart.00717.2014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 11/18/2015] [Indexed: 01/08/2023]
Abstract
We previously reported that the cardiomyocyte-specific leucine-rich repeat containing protein (LRRC)10 has critical functions in the mammalian heart. In the present study, we tested the role of LRRC10 in the response of the heart to biomechanical stress by performing transverse aortic constriction on Lrrc10-null (Lrrc10(-/-)) mice. Mild pressure overload induced severe cardiac dysfunction and ventricular dilation in Lrrc10(-/-) mice compared with control mice. In addition to dilation and cardiomyopathy, Lrrc10(-/-) mice showed a pronounced increase in heart weight with pressure overload stimulation and a more dramatic loss of cardiac ventricular performance, collectively suggesting that the absence of LRRC10 renders the heart more disease prone with greater hypertrophy and structural remodeling, although rates of cardiac fibrosis and myocyte dropout were not different from control mice. Lrrc10(-/-) cardiomyocytes also exhibited reduced contractility in response to β-adrenergic stimulation, consistent with loss of cardiac ventricular performance after pressure overload. We have previously shown that LRRC10 interacts with actin in the heart. Here, we show that His(150) of LRRC10 was required for an interaction with actin, and this interaction was reduced after pressure overload, suggesting an integral role for LRRC10 in the response of the heart to mechanical stress. Importantly, these experiments demonstrated that LRRC10 is required to maintain cardiac performance in response to pressure overload and suggest that dysregulated expression or mutation of LRRC10 may greatly sensitize human patients to more severe cardiac disease in conditions such as chronic hypertension or aortic stenosis.
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Affiliation(s)
- Matthew J Brody
- Department of Cell and Regenerative Biology, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin; Molecular and Environmental Toxicology Center, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin
| | - Li Feng
- Department of Medicine, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin; and
| | - Adrian C Grimes
- Department of Medicine, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin; and
| | - Timothy A Hacker
- Department of Medicine, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin; and
| | - Timothy M Olson
- Cardiovascular Genetics Research Laboratory and Division of Pediatric Cardiology, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota
| | - Timothy J Kamp
- Department of Cell and Regenerative Biology, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin; Department of Medicine, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin; and
| | - Ravi C Balijepalli
- Department of Medicine, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin; and
| | - Youngsook Lee
- Department of Cell and Regenerative Biology, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin; Molecular and Environmental Toxicology Center, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin;
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17
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Thoonen R, Giovanni S, Govindan S, Lee DI, Wang GR, Calamaras TD, Takimoto E, Kass DA, Sadayappan S, Blanton RM. Molecular Screen Identifies Cardiac Myosin-Binding Protein-C as a Protein Kinase G-Iα Substrate. Circ Heart Fail 2015; 8:1115-22. [PMID: 26477830 DOI: 10.1161/circheartfailure.115.002308] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 10/08/2015] [Indexed: 12/11/2022]
Abstract
BACKGROUND Pharmacological activation of cGMP-dependent protein kinase G I (PKGI) has emerged as a therapeutic strategy for humans with heart failure. However, PKG-activating drugs have been limited by hypotension arising from PKG-induced vasodilation. PKGIα antiremodeling substrates specific to the myocardium might provide targets to circumvent this limitation, but currently remain poorly understood. METHODS AND RESULTS We performed a screen for myocardial proteins interacting with the PKGIα leucine zipper (LZ)-binding domain to identify myocardial-specific PKGI antiremodeling substrates. Our screen identified cardiac myosin-binding protein-C (cMyBP-C), a cardiac myocyte-specific protein, which has been demonstrated to inhibit cardiac remodeling in the phosphorylated state, and when mutated leads to hypertrophic cardiomyopathy in humans. GST pulldowns and precipitations with cGMP-conjugated beads confirmed the PKGIα-cMyBP-C interaction in myocardial lysates. In vitro studies demonstrated that purified PKGIα phosphorylates the cMyBP-C M-domain at Ser-273, Ser-282, and Ser-302. cGMP induced cMyBP-C phosphorylation at these residues in COS cells transfected with PKGIα, but not in cells transfected with LZ mutant PKGIα, containing mutations to disrupt LZ substrate binding. In mice subjected to left ventricular pressure overload, PKGI activation with sildenafil increased cMyBP-C phosphorylation at Ser-273 compared with untreated mice. cGMP also induced cMyBP-C phosphorylation in isolated cardiac myocytes. CONCLUSIONS Taken together, these data support that PKGIα and cMyBP-C interact in the heart and that cMyBP-C is an anti remodeling PKGIα kinase substrate. This study provides the first identification of a myocardial-specific PKGIα LZ-dependent antiremodeling substrate and supports further exploration of PKGIα myocardial LZ substrates as potential therapeutic targets for heart failure.
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Affiliation(s)
- Robrecht Thoonen
- From the Molecular Cardiology Research Institute (R.T., G.-R.W., T.D.C., R.M.B.) and Division of Cardiology (R.M.B.), Tufts Medical Center, Boston, MA; Tufts University School of Medicine, Boston, MA (S. Giovanni); Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, IL (S. Govindan, S.S.); Johns Hopkins Medical Institutions, Baltimore, MD (D.I.L., E.T., D.A.K.); and Department of Cardiovascular Medicine, The University of Tokyo, Tokyo, Japan (E.T.)
| | - Shewit Giovanni
- From the Molecular Cardiology Research Institute (R.T., G.-R.W., T.D.C., R.M.B.) and Division of Cardiology (R.M.B.), Tufts Medical Center, Boston, MA; Tufts University School of Medicine, Boston, MA (S. Giovanni); Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, IL (S. Govindan, S.S.); Johns Hopkins Medical Institutions, Baltimore, MD (D.I.L., E.T., D.A.K.); and Department of Cardiovascular Medicine, The University of Tokyo, Tokyo, Japan (E.T.)
| | - Suresh Govindan
- From the Molecular Cardiology Research Institute (R.T., G.-R.W., T.D.C., R.M.B.) and Division of Cardiology (R.M.B.), Tufts Medical Center, Boston, MA; Tufts University School of Medicine, Boston, MA (S. Giovanni); Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, IL (S. Govindan, S.S.); Johns Hopkins Medical Institutions, Baltimore, MD (D.I.L., E.T., D.A.K.); and Department of Cardiovascular Medicine, The University of Tokyo, Tokyo, Japan (E.T.)
| | - Dong I Lee
- From the Molecular Cardiology Research Institute (R.T., G.-R.W., T.D.C., R.M.B.) and Division of Cardiology (R.M.B.), Tufts Medical Center, Boston, MA; Tufts University School of Medicine, Boston, MA (S. Giovanni); Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, IL (S. Govindan, S.S.); Johns Hopkins Medical Institutions, Baltimore, MD (D.I.L., E.T., D.A.K.); and Department of Cardiovascular Medicine, The University of Tokyo, Tokyo, Japan (E.T.)
| | - Guang-Rong Wang
- From the Molecular Cardiology Research Institute (R.T., G.-R.W., T.D.C., R.M.B.) and Division of Cardiology (R.M.B.), Tufts Medical Center, Boston, MA; Tufts University School of Medicine, Boston, MA (S. Giovanni); Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, IL (S. Govindan, S.S.); Johns Hopkins Medical Institutions, Baltimore, MD (D.I.L., E.T., D.A.K.); and Department of Cardiovascular Medicine, The University of Tokyo, Tokyo, Japan (E.T.)
| | - Timothy D Calamaras
- From the Molecular Cardiology Research Institute (R.T., G.-R.W., T.D.C., R.M.B.) and Division of Cardiology (R.M.B.), Tufts Medical Center, Boston, MA; Tufts University School of Medicine, Boston, MA (S. Giovanni); Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, IL (S. Govindan, S.S.); Johns Hopkins Medical Institutions, Baltimore, MD (D.I.L., E.T., D.A.K.); and Department of Cardiovascular Medicine, The University of Tokyo, Tokyo, Japan (E.T.)
| | - Eiki Takimoto
- From the Molecular Cardiology Research Institute (R.T., G.-R.W., T.D.C., R.M.B.) and Division of Cardiology (R.M.B.), Tufts Medical Center, Boston, MA; Tufts University School of Medicine, Boston, MA (S. Giovanni); Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, IL (S. Govindan, S.S.); Johns Hopkins Medical Institutions, Baltimore, MD (D.I.L., E.T., D.A.K.); and Department of Cardiovascular Medicine, The University of Tokyo, Tokyo, Japan (E.T.)
| | - David A Kass
- From the Molecular Cardiology Research Institute (R.T., G.-R.W., T.D.C., R.M.B.) and Division of Cardiology (R.M.B.), Tufts Medical Center, Boston, MA; Tufts University School of Medicine, Boston, MA (S. Giovanni); Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, IL (S. Govindan, S.S.); Johns Hopkins Medical Institutions, Baltimore, MD (D.I.L., E.T., D.A.K.); and Department of Cardiovascular Medicine, The University of Tokyo, Tokyo, Japan (E.T.)
| | - Sakthivel Sadayappan
- From the Molecular Cardiology Research Institute (R.T., G.-R.W., T.D.C., R.M.B.) and Division of Cardiology (R.M.B.), Tufts Medical Center, Boston, MA; Tufts University School of Medicine, Boston, MA (S. Giovanni); Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, IL (S. Govindan, S.S.); Johns Hopkins Medical Institutions, Baltimore, MD (D.I.L., E.T., D.A.K.); and Department of Cardiovascular Medicine, The University of Tokyo, Tokyo, Japan (E.T.)
| | - Robert M Blanton
- From the Molecular Cardiology Research Institute (R.T., G.-R.W., T.D.C., R.M.B.) and Division of Cardiology (R.M.B.), Tufts Medical Center, Boston, MA; Tufts University School of Medicine, Boston, MA (S. Giovanni); Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, IL (S. Govindan, S.S.); Johns Hopkins Medical Institutions, Baltimore, MD (D.I.L., E.T., D.A.K.); and Department of Cardiovascular Medicine, The University of Tokyo, Tokyo, Japan (E.T.).
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18
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Barefield D, Kumar M, Gorham J, Seidman JG, Seidman CE, de Tombe PP, Sadayappan S. Haploinsufficiency of MYBPC3 exacerbates the development of hypertrophic cardiomyopathy in heterozygous mice. J Mol Cell Cardiol 2015; 79:234-43. [PMID: 25463273 PMCID: PMC4642280 DOI: 10.1016/j.yjmcc.2014.11.018] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 11/10/2014] [Accepted: 11/17/2014] [Indexed: 01/01/2023]
Abstract
Mutations in MYBPC3, the gene encoding cardiac myosin binding protein-C (cMyBP-C), account for ~40% of hypertrophic cardiomyopathy (HCM) cases. Most pathological MYBPC3 mutations encode truncated protein products not found in tissue. Reduced protein levels occur in symptomatic heterozygous human HCM carriers, suggesting haploinsufficiency as an underlying mechanism of disease. However, we do not know if reduced cMyBP-C content results from, or initiates the development of HCM. In previous studies, heterozygous (HET) mice with a MYBPC3 C'-terminal truncation mutation and normal cMyBP-C levels show altered contractile function prior to any overt hypertrophy. Therefore, this study aimed to test whether haploinsufficiency occurs, with decreased cMyBP-C content, following cardiac stress and whether the functional impairment in HET MYBPC3 hearts leads to worsened disease progression. To address these questions, transverse aortic constriction (TAC) was performed on three-month-old wild-type (WT) and HET MYBPC3-truncation mutant mice and then characterized at 4 and 12weeks post-surgery. HET-TAC mice showed increased hypertrophy and reduced ejection fraction compared to WT-TAC mice. At 4weeks post-surgery, HET myofilaments showed significantly reduced cMyBP-C content. Functionally, HET-TAC cardiomyocytes showed impaired force generation, higher Ca(2+) sensitivity, and blunted length-dependent increase in force generation. RNA sequencing revealed several differentially regulated genes between HET and WT groups, including regulators of remodeling and hypertrophic response. Collectively, these results demonstrate that haploinsufficiency occurs in HET MYBPC3 mutant carriers following stress, causing, in turn, reduced cMyBP-C content and exacerbating the development of dysfunction at myofilament and whole-heart levels.
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Affiliation(s)
- David Barefield
- Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, IL, USA
| | - Mohit Kumar
- Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, IL, USA
| | - Joshua Gorham
- Department of Genetics, Harvard Medical School, Boston, MA, USA
| | | | | | - Pieter P de Tombe
- Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, IL, USA
| | - Sakthivel Sadayappan
- Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, IL, USA.
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Bal UA, Atar İ, Öktem M, Zeyneloğlu HB, Yıldırır A, Kuşcu E, Müderrisoğlu H. The effect of raloxifene on left ventricular hypertrophy in postmenopausal women: A prospective, randomized, and controlled study. Anatol J Cardiol 2014; 15:480-4. [PMID: 25430415 PMCID: PMC5779141 DOI: 10.5152/akd.2014.5473] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
OBJECTIVE In healthy women, there is a progressive age-related increase in myocardial mass that is not seen in their male counterparts and occurs primarily in postmenopausal women. Raloxifene is a selective estrogen receptor modulator that has estrogenic actions on bone and the cardiovascular system. The aim of this study was to investigate the effect of raloxifene on myocardial hypertrophy in postmenopausal patients. METHODS A total of 22 postmenopausal osteoporotic women were included in this open-label, randomized, prospective, controlled study. Patients were randomized into two groups: 11 of the patients (group 1) were treated with raloxifene 60 mg/day, and the other 11 patients
(group 2) were defined as the control group. Quantitative 2-dimensional and M-mode echocardiographic examination was performed in all patients at the beginning and repeated at the end of the 6-month follow-up period. Left ventricle mass (LVM) and left ventricle mass index (LVMI) were calculated for all patients. RESULTS The mean age of the patients was 57.2±3.9 years, and baseline clinical characteristics and echocardiographic parameters were similar between the two groups. After 6 months of raloxifene treatment, there was no difference in echocardiographic parameters of LVM and LVMI compared with the control group (201.2±25.9 gr vs. 169.7±46.2 gr, p=0.14 and 120.4±25.9 gr/m2 vs. 105.5±26.3 gr/m2, p=0.195, respectively). There was also no significant difference in LVM and LVMI in the within-group analysis of both groups. CONCLUSION Raloxifene therapy does not affect myocardial hypertrophy in postmenopausal women after 6 months of treatment.
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Affiliation(s)
- Uğur Abbas Bal
- Department of Cardiology, Faculty of Medicine, Başkent University; Ankara-Turkey.
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Wilson K, Lucchesi PA. Myofilament dysfunction as an emerging mechanism of volume overload heart failure. Pflugers Arch 2014; 466:1065-77. [PMID: 24488008 DOI: 10.1007/s00424-014-1455-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Revised: 01/17/2014] [Accepted: 01/19/2014] [Indexed: 11/28/2022]
Abstract
Two main hemodynamic overload mechanisms [i.e., volume and pressure overload (VO and PO, respectively] result in heart failure (HF), and these two mechanisms have divergent pathologic alterations and different pathophysiological mechanisms. Extensive evidence from animal models and human studies of PO demonstrate a clear association with alterations in Ca(2+) homeostasis. By contrast, emerging evidence from animal models and patients with regurgitant valve disease and dilated cardiomyopathy point toward a more prominent role of myofilament dysfunction. With respect to VO HF, key features of excitation-contraction coupling defects, myofilament dysfunction, and extracellular matrix composition will be discussed.
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Affiliation(s)
- Kristin Wilson
- Center for Cardiovascular and Pulmonary Research and The Heart Center, Nationwide Children's Hospital, Columbus, OH, USA
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Cardiac myosin-binding protein-C is a critical mediator of diastolic function. Pflugers Arch 2014; 466:451-7. [PMID: 24442121 PMCID: PMC3928517 DOI: 10.1007/s00424-014-1442-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 12/23/2013] [Accepted: 01/03/2014] [Indexed: 12/25/2022]
Abstract
Diastolic dysfunction prominently contributes to heart failure with preserved ejection fraction (HFpEF). Owing partly to inadequate understanding, HFpEF does not have any effective treatments. Cardiac myosin-binding protein-C (cMyBP-C), a component of the thick filament of heart muscle that can modulate cross-bridge attachment/detachment cycling process by its phosphorylation status, appears to be involved in the diastolic dysfunction associated with HFpEF. In patients, cMyBP-C mutations are associated with diastolic dysfunction even in the absence of hypertrophy. cMyBP-C deletion mouse models recapitulate diastolic dysfunction despite in vitro evidence of uninhibited cross-bridge cycling. Reduced phosphorylation of cMyBP-C is also associated with diastolic dysfunction in patients. Mouse models of reduced cMyBP-C phosphorylation exhibit diastolic dysfunction while cMyBP-C phosphorylation mimetic mouse models show enhanced diastolic function. Thus, cMyBP-C phosphorylation mediates diastolic function. Experimental results of both cMyBP-C deletion and reduced cMyBP-C phosphorylation causing diastolic dysfunction suggest that cMyBP-C phosphorylation level modulates cross-bridge detachment rate in relation to ongoing attachment rate to mediate relaxation. Consequently, alteration in cMyBP-C regulation of cross-bridge detachment is a key mechanism that causes diastolic dysfunction. Regardless of the exact molecular mechanism, ample clinical and experimental data show that cMyBP-C is a critical mediator of diastolic function. Furthermore, targeting cMyBP-C phosphorylation holds potential as a future treatment for diastolic dysfunction.
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Cardiac myosin binding protein-C: a novel sarcomeric target for gene therapy. Pflugers Arch 2013; 466:225-30. [PMID: 24310821 DOI: 10.1007/s00424-013-1412-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Revised: 11/22/2013] [Accepted: 11/26/2013] [Indexed: 01/19/2023]
Abstract
Through its ability to interact with both the thick and thin filament proteins within the sarcomere, cardiac myosin binding protein-C (cMyBP-C) regulates the contractile properties of the myocardium. The central regulatory role of cMyBP-C in heart function is emphasized by the fact that a large proportion of inherited hypertrophic cardiomyopathy cases in humans are caused by mutations in cMyBP-C. The primary dysfunction in cMyBP-C-related cardiomyopathies is likely to be abnormal myofilament contractile function; however, currently, there are no effective therapies for ameliorating these contractile defects. Thus, there is a compelling need to design novel therapies to restore normal contractile function in cMyBP-C-related cardiomyopathies. To this end, concepts gleaned from various structural, functional, and biochemical studies can now be utilized to engineer cMyBP-C proteins that, when incorporated into the sarcomere, can significantly improve contractile function. In this review, we discuss the rationale for cMyBP-C-based gene therapies that can be utilized to treat contractile dysfunction in inherited and acquired cardiomyopathies.
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Chen YH, Pai CW, Huang SW, Chang SN, Lin LY, Chiang FT, Lin JL, Hwang JJ, Tsai CT. Inactivation of Myosin binding protein C homolog in zebrafish as a model for human cardiac hypertrophy and diastolic dysfunction. J Am Heart Assoc 2013; 2:e000231. [PMID: 24047589 PMCID: PMC3835223 DOI: 10.1161/jaha.113.000231] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Background Sudden cardiac death due to malignant ventricular arrhythmia is a devastating manifestation of cardiac hypertrophy. Sarcomere protein myosin binding protein C is functionally related to cardiac diastolic function and hypertrophy. Zebrafish is a better model to study human electrophysiology and arrhythmia than rodents because of the electrophysiological characteristics similar to those of humans. Methods and Results We established a zebrafish model of cardiac hypertrophy and diastolic dysfunction by genetic knockdown of myosin binding protein C gene (mybpc3) and investigated the electrophysiological phenotypes in this model. We found expression of zebrafish mybpc3 restrictively in the heart and slow muscle, and mybpc3 gene was evolutionally conservative with sequence homology between zebrafish and human mybpc3 genes. Zebrafish with genetic knockdown of mybpc3 by morpholino showed ventricular hypertrophy with increased myocardial wall thickness and diastolic heart failure, manifesting as decreased ventricular diastolic relaxation velocity, pericardial effusion, and dilatation of the atrium. In terms of electrophysiological phenotypes, mybpc3 knockdown fish had a longer ventricular action potential duration and slower ventricular diastolic calcium reuptake, both of which are typical electrophysiological features in human cardiac hypertrophy and heart failure. Impaired calcium reuptake resulted in increased susceptibility to calcium transient alternans and action potential duration alternans, which have been proved to be central to the genesis of malignant ventricular fibrillation and a sensitive marker of sudden cardiac death. Conclusions mybpc3 knockdown in zebrafish recapitulated the morphological, mechanical, and electrophysiological phenotypes of human cardiac hypertrophy and diastolic heart failure. Our study also first demonstrated arrhythmogenic cardiac alternans in cardiac hypertrophy.
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Affiliation(s)
- Yau-Hung Chen
- Department of Chemistry, Tamkang University, Taipei, Taiwan
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de Lange WJ, Grimes AC, Hegge LF, Ralphe JC. Ablation of cardiac myosin-binding protein-C accelerates contractile kinetics in engineered cardiac tissue. ACTA ACUST UNITED AC 2013; 141:73-84. [PMID: 23277475 PMCID: PMC3536521 DOI: 10.1085/jgp.201210837] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Hypertrophic cardiomyopathy (HCM) caused by mutations in cardiac myosin–binding protein-C (cMyBP-C) is a heterogenous disease in which the phenotypic presentation is influenced by genetic, environmental, and developmental factors. Though mouse models have been used extensively to study the contractile effects of cMyBP-C ablation, early postnatal hypertrophic and dilatory remodeling may overshadow primary contractile defects. The use of a murine engineered cardiac tissue (mECT) model of cMyBP-C ablation in the present study permits delineation of the primary contractile kinetic abnormalities in an intact tissue model under mechanical loading conditions in the absence of confounding remodeling events. We generated mechanically integrated mECT using isolated postnatal day 1 mouse cardiac cells from both wild-type (WT) and cMyBP-C–null hearts. After culturing for 1 wk to establish coordinated spontaneous contraction, we measured twitch force and Ca2+ transients at 37°C during pacing at 6 and 9 Hz, with and without dobutamine. Compared with WT, the cMyBP-C–null mECT demonstrated faster late contraction kinetics and significantly faster early relaxation kinetics with no difference in Ca2+ transient kinetics. Strikingly, the ability of cMyBP-C–null mECT to increase contractile kinetics in response to adrenergic stimulation and increased pacing frequency were severely impaired. We conclude that cMyBP-C ablation results in constitutively accelerated contractile kinetics with preserved peak force with minimal contractile kinetic reserve. These functional abnormalities precede the development of the hypertrophic phenotype and do not result from alterations in Ca2+ transient kinetics, suggesting that alterations in contractile velocity may serve as the primary functional trigger for the development of hypertrophy in this model of HCM. Our findings strongly support a mechanism in which cMyBP-C functions as a physiological brake on contraction by positioning myosin heads away from the thin filament, a constraint which is removed upon adrenergic stimulation or cMyBP-C ablation.
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Affiliation(s)
- Willem J de Lange
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA
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