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Dowrick JM, Taberner AJ, Han JC, Tran K. Methods for assessing cardiac myofilament calcium sensitivity. Front Physiol 2023; 14:1323768. [PMID: 38116581 PMCID: PMC10728676 DOI: 10.3389/fphys.2023.1323768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 11/23/2023] [Indexed: 12/21/2023] Open
Abstract
Myofilament calcium (Ca2+) sensitivity is one of several mechanisms by which force production of cardiac muscle is modulated to meet the ever-changing demands placed on the heart. Compromised Ca2+ sensitivity is associated with pathologies, which makes it a parameter of interest for researchers. Ca2+ Sensitivity is the ratio of the association and dissociation rates between troponin C (TnC) and Ca2+. As it is not currently possible to measure these rates in tissue preparations directly, methods have been developed to infer myofilament sensitivity, typically using some combination of force and Ca2+ measurements. The current gold-standard approach constructs a steady-state force-Ca2+ relation by exposing permeabilised muscle samples to a range of Ca2+ concentrations and uses the half-maximal concentration as a proxy for sensitivity. While a valuable method for steady-state investigations, the permeabilisation process makes the method unsuitable when examining dynamic, i.e., twitch-to-twitch, changes in myofilament sensitivity. The ability of the heart to transiently adapt to changes in load is an important consideration when evaluating the impact of disease states. Alternative methods have been proffered, including force-Ca2+ phase loops, potassium contracture, hybrid experimental-modelling and conformation-based fluorophore approaches. This review provides an overview of the mechanisms underlying myofilament Ca2+ sensitivity, summarises existing methods, and explores, with modelling, whether any of them are suited to investigating dynamic changes in sensitivity. We conclude that a method that equips researchers to investigate the transient change of myofilament Ca2+ sensitivity is still needed. We propose that such a method will involve simultaneous measurements of cytosolic Ca2+ and TnC activation in actively twitching muscle and a biophysical model to interpret these data.
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Affiliation(s)
- Jarrah M. Dowrick
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Andrew J. Taberner
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Department of Engineering Science and Biomedical Engineering, University of Auckland, Auckland, New Zealand
| | - June-Chiew Han
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Kenneth Tran
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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Duchatsch F, Tardelli LP, Herrera NA, Ruiz TFR, Vicentini CA, Okoshi K, Santos CF, Amaral SL. Dexamethasone and Training-Induced Cardiac Remodeling Improve Cardiac Function and Arterial Pressure in Spontaneously Hypertensive Rats. J Cardiovasc Pharmacol Ther 2020; 26:189-199. [PMID: 32856477 DOI: 10.1177/1074248420953271] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
INTRODUCTION Dexamethasone (DEX)-induced hypertension and cardiac remodeling are still unclear, especially in spontaneously hypertensive rats (SHR). On the other side, exercise training is a good strategy to control hypertension. Therefore, this study investigated the effects of DEX treatment and physical training on arterial pressure and cardiac remodeling in SHR. MATERIAL AND METHODS SHR underwent treadmill training (5 days/week, 1h/session, at 50-60% of maximal capacity, 0% degree, 75 days) and received low-dose of DEX (50µg/kg, s.c.) during the last 15 days. Sedentary Wistar rats (W) were used as control. Echocardiography and artery catheterization were performed for cardiac remodeling and function, arterial pressure and autonomic nervous system analyses. In addition, left ventricle (LV) capillary density, myocyte diameter and collagen deposition area were analyzed using specific histological staining. RESULTS Low-dose of DEX treatment did not exacerbate arterial pressure of SHR and trained groups had lower values, regardless of DEX. DEX and training decreased relative left ventricle wall thickness (RWT) and determined LV angiogenesis (+19%) and lower collagen deposition area (-22%). In addition, it determined increased left ventricular diastolic diameter. These changes were followed by improvements on systolic and diastolic function, since it was observed increased posterior wall shortening velocity (PWSV) and reduced isovolumetric relaxation time (IVRT). CONCLUSION In conclusion, this study is unique to indicate that low-dose of DEX treatment does not exacerbate arterial pressure in SHR and, when associated with training, it improves LV systolic and diastolic function, which may be due to LV angiogenesis and reduction of wall collagen deposition area.
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Affiliation(s)
- Francine Duchatsch
- Joint Graduate Program in Physiological Sciences, PIPGCF UFSCar/UNESP, São Carlos/SP, Brazil
| | - Lidieli P Tardelli
- Joint Graduate Program in Physiological Sciences, PIPGCF UFSCar/UNESP, São Carlos/SP, Brazil
| | - Naiara A Herrera
- Joint Graduate Program in Physiological Sciences, PIPGCF UFSCar/UNESP, São Carlos/SP, Brazil
| | - Thalles F R Ruiz
- Department of Biological Sciences, School of Sciences, 28108São Paulo State University (Unesp), Bauru/SP, Brazil
| | - Carlos A Vicentini
- Department of Biological Sciences, School of Sciences, 28108São Paulo State University (Unesp), Bauru/SP, Brazil
| | - Katashi Okoshi
- Department of Internal Medicine, Botucatu Medical School, 28108São Paulo State University (Unesp), Botucatu/SP, Brazil
| | - Carlos F Santos
- Department of Biological Sciences, Bauru School of Dentistry, 28133University of São Paulo (Usp), Bauru/SP, Brazil
| | - Sandra L Amaral
- Joint Graduate Program in Physiological Sciences, PIPGCF UFSCar/UNESP, São Carlos/SP, Brazil.,Department of Physical Education, School of Sciences, 28108São Paulo State University (Unesp), Bauru/SP, Brazil
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Li Z, Singh S, Suryavanshi SV, Ding W, Shen X, Wijaya CS, Gao WD, McConnell BK. Force development and intracellular Ca 2+ in intact cardiac muscles from gravin mutant mice. Eur J Pharmacol 2017; 807:117-126. [PMID: 28428008 DOI: 10.1016/j.ejphar.2017.04.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 04/13/2017] [Accepted: 04/13/2017] [Indexed: 02/08/2023]
Abstract
Gravin (AKAP12) is an A-kinase-anchoring-protein that scaffolds protein kinase A (PKA), β2-adrenergic receptor (β2-AR), protein phosphatase 2B and protein kinase C. Gravin facilitates β2-AR-dependent signal transduction through PKA to modulate cardiac excitation-contraction coupling and its removal positively affects cardiac contraction. Trabeculae from the right ventricles of gravin mutant (gravin-t/t) mice were employed for force determination. Simultaneously, corresponding intracellular Ca2+ transient ([Ca2+]i) were measured. Twitch force (Tf)-interval relationship, [Ca2+]i-interval relationship, and the rate of decay of post-extrasysolic potentiation (Rf) were also obtained. Western blot analysis were performed to correlate sarcomeric protein expression with alterations in calcium cycling between the WT and gravin-t/t hearts. Gravin-t/t muscles had similar developed force compared to WT muscles despite having lower [Ca2+]i at any given external Ca2+ concentration ([Ca2+]o). The time to peak force and peak [Ca2+]i were slower and the time to 75% relaxation was significantly prolonged in gravin-t/t muscles. Both Tf-interval and [Ca2+]i-interval relations were depressed in gravin-t/t muscles. Rf, however, did not change. Furthermore, Western blot analysis revealed decreased ryanodine receptor (RyR2) phosphorylation in gravin-t/t hearts. Gravin-t/t cardiac muscle exhibits increased force development in responsiveness to Ca2+. The Ca2+ cycling across the SR appears to be unaltered in gravin-t/t muscle. Our study suggests that gravin is an important component of cardiac contraction regulation via increasing myofilament sensitivity to calcium. Further elucidation of the mechanism can provide insights to role of gravin if any in the pathophysiology of impaired contractility.
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Affiliation(s)
- Zhitao Li
- Department of Pathophysiology, Harbin Medical University, Heilongjiang, China
| | - Sonal Singh
- Department of Pharmacotherapy and Translational Research, College of Pharmacy, University of Florida, Gainesville, FL, USA
| | - Santosh V Suryavanshi
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Texas Medical Center, Houston, TX, USA
| | - Wengang Ding
- Department of Anesthesiology of 2nd Affiliated Hospital, Harbin Medical University, Heilongjiang, China
| | - Xiaoxu Shen
- Cardiology Department, Dongzhimen Hospital Affiliated to Beijing University of Chinese Medicine, Beijing, China
| | - Cori S Wijaya
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Texas Medical Center, Houston, TX, USA
| | - Wei Dong Gao
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, 1800 Orleans Street, Zaye Tower 6208, Baltimore, MD 21287, USA.
| | - Bradley K McConnell
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Texas Medical Center, Houston, TX, USA.
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Silveira CFSMP, Campos DHS, Freire PP, Deus AF, Okoshi K, Padovani CR, Cicogna AC. Importance of SERCA2a on early isolated diastolic dysfunction induced by supravalvular aortic stenosis in rats. ACTA ACUST UNITED AC 2017; 50:e5742. [PMID: 28423119 PMCID: PMC5441282 DOI: 10.1590/1414-431x20175742] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 02/10/2017] [Indexed: 01/19/2023]
Abstract
Cardiac remodeling is defined as changes in shape and function of the heart in response to aggression (pressure overload). The sarcoplasmic reticulum calcium ATPase cardiac isoform 2a (SERCA2a) is a known factor that influences function. A wide spectrum of studies report a decrease in SERCA2a in heart failure, but none evaluate it's the role in early isolated diastolic dysfunction in supravalvular aortic stenosis (AoS). Our hypothesis was that SERCA2a participates in such dysfunction. Thirty-day-old male Wistar rats (60-80 g) were divided into AoS and Sham groups, which were submitted to surgery with or without aorta clipping, respectively. After 6 weeks, the animals were submitted to echocardiogram and functional analysis by isolated papillary muscle (IPM) in basal condition, hypoxia, and SERCA2a blockage with cyclopiazonic acid at calcium concentrations of 0.5, 1.5, and 2.5 mM. Western-blot analyses were used for SERCA2a and phospholamban detection. Data analysis was carried out with Student's t-test and ANOVA. AoS enhanced left atrium and E and A wave ratio, with preserved ejection fraction. Basal condition in IPM showed similar increases in developed tension (DT) and resting tension (RT) in AoS, and hypoxia was similar between groups. After cyclopiazonic acid blockage, final DT was equally decreased and RT was similar between groups, but the speed of relaxation was decreased in the AoS group. Western-blot was uniform in all evaluations. The hypothesis was confirmed, since functional parameters regarding SERCA2a were changed in the AoS group.
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Affiliation(s)
- C F S M P Silveira
- Departamento de Clínica Médica, Faculdade de Medicina de Botucatu, Universidade Estadual Paulista, Botucatu, SP, Brasil
| | - D H S Campos
- Departamento de Clínica Médica, Faculdade de Medicina de Botucatu, Universidade Estadual Paulista, Botucatu, SP, Brasil
| | - P P Freire
- Departamento de Clínica Médica, Faculdade de Medicina de Botucatu, Universidade Estadual Paulista, Botucatu, SP, Brasil
| | - A F Deus
- Departamento de Clínica Médica, Faculdade de Medicina de Botucatu, Universidade Estadual Paulista, Botucatu, SP, Brasil
| | - K Okoshi
- Departamento de Clínica Médica, Faculdade de Medicina de Botucatu, Universidade Estadual Paulista, Botucatu, SP, Brasil
| | - C R Padovani
- Departamento de Bioestatística, Instituto de Biociências, Universidade Estadual Paulista, Botucatu, SP, Brasil
| | - A C Cicogna
- Departamento de Clínica Médica, Faculdade de Medicina de Botucatu, Universidade Estadual Paulista, Botucatu, SP, Brasil
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Han JC, Barrett CJ, Taberner AJ, Loiselle DS. Does reduced myocardial efficiency in systemic hypertensive-hypertrophy correlate with increased left-ventricular wall thickness? Hypertens Res 2015; 38:530-8. [PMID: 25787044 DOI: 10.1038/hr.2015.37] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 02/02/2015] [Accepted: 02/14/2015] [Indexed: 12/19/2022]
Abstract
Elevated systemic blood pressure, and the attendant development of pathologic left ventricular (LV) hypertrophy, ultimately culminates in heart failure and death. In clinical studies, a reduction of myocardial efficiency has been implicated in systemic hypertensive-hypertrophy. However, it is uncertain whether reduced efficiency correlates with LV wall thickness. Hence, we performed experiments on isolated working hearts of spontaneously hypertensive rats (SHRs)-a widely-used experimental model of human hypertensive-hypertrophy. We contrasted their mechanoenergetic performance with that of Wistar controls at two ages: Adult (9 months) and Aged (post-18 months). The use of animal hearts allowed us to perform experiments over a wide range of afterloads. We found that mechanoenergetic performance (coronary and aortic flows, work output and oxygen consumption) declined with age. The peak efficiency of the Adult SHR was essentially similar to that of Control, but that for the Aged SHR was lower, compared with that of age-matched Wistar rats. All variables, including peak efficiency, obtained from the failing Aged SHR hearts (which also developed right ventricular hypertrophy), were greatly reduced. Our data reveal that peak efficiency of the Aged SHR, upon transitioning from compensated hypertrophy to failure, diminishes sharply, arising from compromised flows-both aortic and coronary. We further show that the reduction of myocardial efficiency in hypertensive-hypertrophy does not correlate with LV wall thickness, but instead is inversely correlated with whole-heart mass. The latter relation may serve as a prognostic and diagnostic tool in the clinical setting.
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Affiliation(s)
- June-Chiew Han
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Carolyn J Barrett
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Andrew J Taberner
- 1] Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand [2] Department of Engineering Science, The University of Auckland, Auckland, New Zealand
| | - Denis S Loiselle
- 1] Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand [2] Department of Physiology, The University of Auckland, Auckland, New Zealand
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Pardo AC, Rinaldi GJ, Mosca SM. Mitochondrial calcium handling in normotensive and spontaneously hypertensive rats: correlation with systolic blood pressure levels. Mitochondrion 2014; 20:75-81. [PMID: 25530492 DOI: 10.1016/j.mito.2014.12.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 12/04/2014] [Accepted: 12/11/2014] [Indexed: 01/10/2023]
Abstract
The aim was to study the mitochondrial Ca(2+) handling of mitochondria isolated from normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) hearts and to establish a possible correlation with systolic blood pressure (SBP). Mitochondrial swelling after Ca(2+) addition, Ca(2+)-retention capacity (CRC) by calcium green method, and membrane potential (ΔΨm) were assessed. SBP was 124±1 (WKY) and 235±6mmHg (SHR). CRC, Ca(2+) response and ΔΨm were lower in SHR than WKY mitochondria. The conclusion is: the more depolarized state of SHR than WKY mitochondria results in an abnormal Ca(2+) handling and this event is closely associated with the SBP.
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Affiliation(s)
- Alejandro Ciocci Pardo
- Centro de Investigaciones Cardiovasculares, CCT-CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina
| | - Gustavo J Rinaldi
- Centro de Investigaciones Cardiovasculares, CCT-CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina
| | - Susana M Mosca
- Centro de Investigaciones Cardiovasculares, CCT-CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina.
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Han JC, Tran K, Johnston CM, Nielsen PMF, Barrett CJ, Taberner AJ, Loiselle DS. Reduced mechanical efficiency in left-ventricular trabeculae of the spontaneously hypertensive rat. Physiol Rep 2014; 2:2/11/e12211. [PMID: 25413328 PMCID: PMC4255817 DOI: 10.14814/phy2.12211] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Long‐term systemic arterial hypertension, and its associated compensatory response of left‐ventricular hypertrophy, is fatal. This disease leads to cardiac failure and culminates in death. The spontaneously hypertensive rat (SHR) is an excellent animal model for studying this pathology, suffering from ventricular failure beginning at about 18 months of age. In this study, we isolated left‐ventricular trabeculae from SHR‐F hearts and contrasted their mechanoenergetic performance with those from nonfailing SHR (SHR‐NF) and normotensive Wistar rats. Our results show that, whereas the performance of the SHR‐F differed little from that of the SHR‐NF, both SHR groups performed less stress‐length work than that of Wistar trabeculae. Their lower work output arose from reduced ability to produce sufficient force and shortening. Neither their heat production nor their enthalpy output (the sum of work and heat), particularly the energy cost of Ca2+ cycling, differed from that of the Wistar controls. Consequently, mechanical efficiency (the ratio of work to change of enthalpy) of both SHR groups was lower than that of the Wistar trabeculae. Our data suggest that in hypertension‐induced left‐ventricular hypertrophy, the mechanical performance of the tissue is compromised such that myocardial efficiency is reduced. Our study provides the first comprehensive examination of cardiac mechanoenergetics in the spontaneously hypertensive rat (SHR – a widely utilized model of human hypertensive cardiomyopathy). Simultaneous measurement of force development, muscle shortening and heat production allows us to calculate force‐length work output, change in enthalpy and, ultimately, mechanical efficiency. In comparison to their age‐matched normotensive Wistar controls, trabeculae from SHR animals, whether “nonfailing” or “failing”, show reduced ability to perform work, despite only modest reduction in heat production. In consequence, their efficiency deteriorates.
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Affiliation(s)
- June-Chiew Han
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Kenneth Tran
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Callum M Johnston
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Poul M F Nielsen
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand Department of Engineering Science, The University of Auckland, Auckland, New Zealand
| | - Carolyn J Barrett
- Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Andrew J Taberner
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand Department of Engineering Science, The University of Auckland, Auckland, New Zealand
| | - Denis S Loiselle
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand Department of Physiology, The University of Auckland, Auckland, New Zealand
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Rodriguez JS, Velez Rueda JO, Salas M, Becerra R, Di Carlo MN, Said M, Vittone L, Rinaldi G, Portiansky EL, Mundiña-Weilenmann C, Palomeque J, Mattiazzi A. Increased Na⁺/Ca²⁺ exchanger expression/activity constitutes a point of inflection in the progression to heart failure of hypertensive rats. PLoS One 2014; 9:e96400. [PMID: 24781001 PMCID: PMC4004550 DOI: 10.1371/journal.pone.0096400] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 04/07/2014] [Indexed: 11/19/2022] Open
Abstract
UNLABELLED Spontaneously hypertensive rat (SHR) constitutes a genetic model widely used to study the natural evolution of hypertensive heart disease. Ca²⁺-handling alterations are known to occur in SHR. However, the putative modifications of Ca²⁺-handling proteins during the progression to heart failure (HF) are not well established. Moreover, the role of apoptosis in SHR is controversial. We investigated intracellular Ca²⁺, Ca²⁺-handling proteins and apoptosis in SHR vs. control Wistar rats (W) from 3 to 15 months (mo). Changes associated with the transition to HF (i.e. lung edema and decrease in midwall fractional shortening), occurred at 15 mo in 38% of SHR (SHRF). In SHRF, twitch and caffeine-induced Ca²⁺ transients, significantly decreased relative to 6/9 mo and 15 mo without HF signs. This decrease occurred in association with a decrease in the time constant of caffeine-Ca²⁺ transient decay and an increase in Na⁺/Ca²⁺ exchanger (NCX) abundance (p<0.05) with no changes in SERCA2a expression/activity. An increased Ca²⁺-calmodulin-kinase II activity, associated with an enhancement of apoptosis (TUNEL and Bax/Bcl2) was observed in SHR relative to W from 3 to 15 mo. CONCLUSIONS 1. Apoptosis is an early and persistent event that may contribute to hypertrophic remodeling but would not participate in the contractile impairment of SHRF. 2. The increase in NCX expression/activity, associated with an increase in Ca²⁺ efflux from the cell, constitutes a primary alteration of Ca²⁺-handling proteins in the evolution to HF. 3. No changes in SERCA2a expression/activity are observed when HF signs become evident.
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Affiliation(s)
- Jesica S. Rodriguez
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| | - J. Omar Velez Rueda
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| | - Margarita Salas
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| | - Romina Becerra
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| | - Mariano N. Di Carlo
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| | - Matilde Said
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| | - Leticia Vittone
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| | - Gustavo Rinaldi
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
| | - Enrique L. Portiansky
- Laboratorio de Análisis de Imágenes, Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata, La Plata, Argentina
| | - Cecilia Mundiña-Weilenmann
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
- * E-mail: (CM-W); (JP)
| | - Julieta Palomeque
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
- * E-mail: (CM-W); (JP)
| | - Alicia Mattiazzi
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata, Facultad de Medicina, Universidad Nacional de La Plata, La Plata, Argentina
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Kuo PL, Lee H, Bray MA, Geisse NA, Huang YT, Adams WJ, Sheehy SP, Parker KK. Myocyte shape regulates lateral registry of sarcomeres and contractility. THE AMERICAN JOURNAL OF PATHOLOGY 2013; 181:2030-7. [PMID: 23159216 DOI: 10.1016/j.ajpath.2012.08.045] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 02/12/2012] [Revised: 08/12/2012] [Accepted: 08/30/2012] [Indexed: 11/25/2022]
Abstract
The heart actively remodels architecture in response to various physiological and pathological conditions. Gross structural change of the heart chambers is directly reflected at the cellular level by altering the morphological characteristics of individual cardiomyocytes. However, an understanding of the relationship between cardiomyocyte shape and the contractile function remains unclear. By using in vitro assays to analyze systolic stress of cardiomyocytes with controlled shape, we demonstrated that the characteristic morphological features of cardiomyocytes observed in a variety of pathophysiological conditions are correlated with mechanical performance. We found that cardiomyocyte contractility is optimized at the cell length/width ratio observed in normal hearts, and decreases in cardiomyocytes with morphological characteristics resembling those isolated from failing hearts. Quantitative analysis of sarcomeric architecture revealed that the change of contractility may arise from alteration of myofibrillar structure. Measurements of intracellular calcium in myocytes revealed unique characteristics of calcium metabolism as a function of myocyte shape. Our data suggest that cell shape is critical in determining contractile performance of single cardiomyocytes by regulating the intracellular structure and calcium handling ability.
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Affiliation(s)
- Po-Ling Kuo
- Disease Biophysics Group, Wyss Institute for Biologically-Inspired Engineering, and the Harvard Stem Cell Institute, School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
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Ward ML, Crossman DJ, Cannell MB. Mechanisms of reduced contractility in an animal model of hypertensive heart failure. Clin Exp Pharmacol Physiol 2012; 38:711-6. [PMID: 21711381 DOI: 10.1111/j.1440-1681.2011.05563.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
1. Alterations in intracellular Ca(2+) homeostasis have frequently been implicated as underlying the contractile dysfunction of failing hearts. Contraction in cardiac muscle is due to a balance between sarcolemmal (SL) and sarcoplasmic reticulum (SR) Ca(2+) transport, which has been studied in single cells and small tissue samples. However, many studies have not used physiological temperatures and pacing rates, and this could be problematic given different temperature dependencies and kinetics for transport processes. 2. Spontaneously-hypertensive rats (SHR) and their age-matched Wistar Kyoto controls (WKY) provide an animal model of hypertensive failure with many features in common to heart failure in humans. Steady-state measurements of Ca(2+) and force showed that peak stress was reduced in trabeculae from failing SHR hearts in comparison to WKY, although the Ca(2+) transients were bigger and decayed more slowly. 3. Dynamic Ca(2+) cycling was investigated by determining the recirculation fraction (RF) of activator Ca(2+) through the SR between beats during recovery from experimental protocols that potentiated twitch force. No difference in RF between rat strains was found, although the RF was dependent on the potentiation protocol used. 4. Superfusion with 10 mmol/L caffeine and 0 mmol/L [Ca(2+)](o) was used to measure SL Ca(2+) extrusion. The caffeine-induced [Ca(2+)](i) transient decayed more slowly in SHR trabeculae, suggesting that SL Ca(2+) extrusion was slower in SHR. 5. An ultrastructural immunohistochemical analysis of left ventricular free wall sections using confocal microscopy showed that t-tubule organization was disrupted in myocytes from SHR, with reduced labelling of the SR Ca(2+) -ATPase and Na(+) -Ca(2+) exchanger in comparison to WKY, with the latter possibly related to a lower fraction of t-tubules per unit cell volume. 6. We suggest that although Ca(2+) transport is altered in the progression to heart failure, force development is not limited by the amplitude of the Ca(2+) transient. Despite slower SR Ca(2+) transport, the recirculation fraction and dynamic response to a change of inotropic state minimally altered changes in the SHR model because there was a similar slowing in Ca(2+) extrusion across the surface membrane.
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Affiliation(s)
- Marie-Louise Ward
- Department of Physiology, University of Auckland, Auckland, New Zealand.
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