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Weidner S, Tomalka A, Rode C, Siebert T. Impact of lengthening velocity on the generation of eccentric force by slow-twitch muscle fibers in long stretches. Pflugers Arch 2024:10.1007/s00424-024-02991-4. [PMID: 39043889 DOI: 10.1007/s00424-024-02991-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 07/01/2024] [Accepted: 07/15/2024] [Indexed: 07/25/2024]
Abstract
After an initial increase, isovelocity elongation of a muscle fiber can lead to diminishing (referred to as Give in the literature) and subsequently increasing force. How the stretch velocity affects this behavior in slow-twitch fibers remains largely unexplored. Here, we stretched fully activated individual rat soleus muscle fibers from 0.85 to 1.3 optimal fiber length at stretch velocities of 0.01, 0.1, and 1 maximum shortening velocity, vmax, and compared the results with those of rat EDL fast-twitch fibers obtained in similar experimental conditions. In soleus muscle fibers, Give was 7%, 18%, and 44% of maximum isometric force for 0.01, 0.1, and 1 vmax, respectively. As in EDL fibers, the force increased nearly linearly in the second half of the stretch, although the number of crossbridges decreased, and its slope increased with stretch velocity. Our findings are consistent with the concept of a forceful detachment and subsequent crossbridge reattachment in the stretch's first phase and a strong viscoelastic titin contribution to fiber force in the second phase of the stretch. Interestingly, we found interaction effects of stretch velocity and fiber type on force parameters in both stretch phases, hinting at fiber type-specific differences in crossbridge and titin contributions to eccentric force. Whether fiber type-specific combined XB and non-XB models can explain these effects or if they hint at some not fully understood properties of muscle contraction remains to be shown. These results may stimulate new optimization perspectives in sports training and provide a better understanding of structure-function relations of muscle proteins.
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Affiliation(s)
- Sven Weidner
- Department of Motion and Exercise Science, University of Stuttgart, Allmandring 28, 70569, Stuttgart, Germany.
| | - André Tomalka
- Department of Motion and Exercise Science, University of Stuttgart, Allmandring 28, 70569, Stuttgart, Germany
| | - Christian Rode
- Institute of Sport Science, Department of Biomechanics, University of Rostock, Rostock, Germany
| | - Tobias Siebert
- Department of Motion and Exercise Science, University of Stuttgart, Allmandring 28, 70569, Stuttgart, Germany
- Stuttgart Center of Simulation Science, University of Stuttgart, Stuttgart, Germany
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2
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Janssens JV, Raaijmakers AJA, Weeks KL, Bell JR, Mellor KM, Curl CL, Delbridge LMD. The cardiomyocyte origins of diastolic dysfunction: cellular components of myocardial "stiffness". Am J Physiol Heart Circ Physiol 2024; 326:H584-H598. [PMID: 38180448 DOI: 10.1152/ajpheart.00334.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Revised: 12/07/2023] [Accepted: 12/21/2023] [Indexed: 01/06/2024]
Abstract
The impaired ability of the heart to relax and stretch to accommodate venous return is generally understood to represent a state of "diastolic dysfunction" and often described using the all-purpose noun "stiffness." Despite the now common qualitative usage of this term in fields of cardiac patho/physiology, the specific quantitative concept of stiffness as a molecular and biophysical entity with real practical interpretation in healthy and diseased hearts is sometimes obscure. The focus of this review is to characterize the concept of cardiomyocyte stiffness and to develop interpretation of "stiffness" attributes at the cellular and molecular levels. Here, we consider "stiffness"-related terminology interpretation and make links between cardiomyocyte stiffness and aspects of functional and structural cardiac performance. We discuss cross bridge-derived stiffness sources, considering the contributions of diastolic myofilament activation and impaired relaxation. This includes commentary relating to the role of cardiomyocyte Ca2+ flux and Ca2+ levels in diastole, the troponin-tropomyosin complex role as a Ca2+ effector in diastole, the myosin ADP dissociation rate as a modulator of cross bridge attachment and regulation of cross-bridge attachment by myosin binding protein C. We also discuss non-cross bridge-derived stiffness sources, including the titin sarcomeric spring protein, microtubule and intermediate filaments, and cytoskeletal extracellular matrix interactions. As the prevalence of conditions involving diastolic heart failure has escalated, a more sophisticated understanding of the molecular, cellular, and tissue determinants of cardiomyocyte stiffness offers potential to develop imaging and molecular intervention tools.
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Affiliation(s)
- Johannes V Janssens
- Department of Anatomy and Physiology, University of Melbourne, Melbourne, Victoria, Australia
| | - Antonia J A Raaijmakers
- Department of Anatomy and Physiology, University of Melbourne, Melbourne, Victoria, Australia
| | - Kate L Weeks
- Department of Anatomy and Physiology, University of Melbourne, Melbourne, Victoria, Australia
- Baker Department of Cardiometabolic Health, University of Melbourne, Melbourne, Victoria, Australia
- Department of Diabetes, Monash University, Parkville, Victoria, Australia
| | - James R Bell
- Department of Anatomy and Physiology, University of Melbourne, Melbourne, Victoria, Australia
- Department of Microbiology, Anatomy, Physiology and Pharmacology, La Trobe University, Melbourne, Victoria, Australia
| | - Kimberley M Mellor
- Department of Anatomy and Physiology, University of Melbourne, Melbourne, Victoria, Australia
- Department of Physiology, University of Auckland, Auckland, New Zealand
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Claire L Curl
- Department of Anatomy and Physiology, University of Melbourne, Melbourne, Victoria, Australia
| | - Lea M D Delbridge
- Department of Anatomy and Physiology, University of Melbourne, Melbourne, Victoria, Australia
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3
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Vermersch E, Neuvendel S, Jouve C, Ruiz-Velasco A, Pereira C, Seguret M, Cattin-Messaoudi ME, Lotfi S, Dorval T, Berson P, Hulot JS. hsa-miR-548v controls the viscoelastic properties of human cardiomyocytes and improves their relaxation rates. JCI Insight 2024; 9:e161356. [PMID: 38165745 PMCID: PMC11143964 DOI: 10.1172/jci.insight.161356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 12/19/2023] [Indexed: 01/04/2024] Open
Abstract
The impairment of left ventricular (LV) diastolic function with an inadequate increase in myocardial relaxation velocity directly results in lower LV compliance, increased LV filling pressures, and heart failure symptoms. The development of agents facilitating the relaxation of human cardiomyocytes requires a better understanding of the underlying regulatory mechanisms. We performed a high-content microscopy-based screening in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) using a library of 2,565 human miRNA mimics and measured relaxation kinetics via high-computing analyses of motion movies. We identified hsa-miR-548v, a primate-specific miRNA, as the miRNA producing the largest increase in relaxation velocities. This positive lusitropic effect was reproduced in engineered cardiac tissues generated with healthy and BRAF T599R mutant hiPSC-CMs and was independent of changes in calcium transients. Consistent with improvements in viscoelastic responses to mechanical stretch, RNA-Seq showed that hsa-miR-548v downregulated multiple targets, especially components of the mechanosensing machinery. The exogenous administration of hsa-miR-548v in hiPSC-CMs notably resulted in a significant reduction of ANKRD1/CARP1 expression and localization at the sarcomeric I-band. This study suggests that the sarcomere I-band is a critical control center regulating the ability of cardiomyocytes to relax and is a target for improving relaxation and diastolic dysfunction.
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Affiliation(s)
- Eva Vermersch
- Université Paris Cité, Inserm, PARCC, F-75015 Paris, France
- Institut de recherches Servier, In vitro Pharmacology unit, and
| | | | - Charlène Jouve
- Université Paris Cité, Inserm, PARCC, F-75015 Paris, France
| | | | - Céline Pereira
- Université Paris Cité, Inserm, PARCC, F-75015 Paris, France
| | - Magali Seguret
- Université Paris Cité, Inserm, PARCC, F-75015 Paris, France
| | | | - Sofia Lotfi
- Institut de recherches Servier, In vitro Pharmacology unit, and
| | - Thierry Dorval
- Institut de recherches Servier, In vitro Pharmacology unit, and
| | - Pascal Berson
- Institut de recherches Servier, Cardiovascular and Metabolism Therapeutic Area, Croissy-sur-seine, France
| | - Jean-Sébastien Hulot
- Université Paris Cité, Inserm, PARCC, F-75015 Paris, France
- CIC1418 and DMU CARTE, AP-HP, Hôpital Européen Georges-Pompidou, F-75015, Paris, France
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4
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Tamargo M, Martínez-Legazpi P, Espinosa MÁ, Lyon A, Méndez I, Gutiérrez-Ibañes E, Fernández AI, Prieto-Arévalo R, González-Mansilla A, Arts T, Delhaas T, Mombiela T, Sanz-Ruiz R, Elízaga J, Yotti R, Tschöpe C, Fernández-Avilés F, Lumens J, Bermejo J. Increased Chamber Resting Tone Is a Key Determinant of Left Ventricular Diastolic Dysfunction. Circ Heart Fail 2023; 16:e010673. [PMID: 38113298 PMCID: PMC10729900 DOI: 10.1161/circheartfailure.123.010673] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 09/22/2023] [Indexed: 12/21/2023]
Abstract
BACKGROUND Twitch-independent tension has been demonstrated in cardiomyocytes, but its role in heart failure (HF) is unclear. We aimed to address twitch-independent tension as a source of diastolic dysfunction by isolating the effects of chamber resting tone (RT) from impaired relaxation and stiffness. METHODS We invasively monitored pressure-volume data during cardiopulmonary exercise in 20 patients with hypertrophic cardiomyopathy, 17 control subjects, and 35 patients with HF with preserved ejection fraction. To measure RT, we developed a new method to fit continuous pressure-volume measurements, and first validated it in a computational model of loss of cMyBP-C (myosin binding protein-C). RESULTS In hypertrophic cardiomyopathy, RT (estimated marginal mean [95% CI]) was 3.4 (0.4-6.4) mm Hg, increasing to 18.5 (15.5-21.5) mm Hg with exercise (P<0.001). At peak exercise, RT was responsible for 64% (53%-76%) of end-diastolic pressure, whereas incomplete relaxation and stiffness accounted for the rest. RT correlated with the levels of NT-proBNP (N-terminal pro-B-type natriuretic peptide; R=0.57; P=0.02) and with pulmonary wedge pressure but following different slopes at rest and during exercise (R2=0.49; P<0.001). In controls, RT was 0.0 mm Hg and 1.2 (0.3-2.8) mm Hg in HF with preserved ejection fraction patients and was also exacerbated by exercise. In silico, RT increased in parallel to the loss of cMyBP-C function and correlated with twitch-independent myofilament tension (R=0.997). CONCLUSIONS Augmented RT is the major cause of LV diastolic chamber dysfunction in hypertrophic cardiomyopathy and HF with preserved ejection fraction. RT transients determine diastolic pressures, pulmonary pressures, and functional capacity to a greater extent than relaxation and stiffness abnormalities. These findings support antimyosin agents for treating HF.
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Affiliation(s)
- María Tamargo
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, and CIBERCV, Spain (M.T., P.M.-L., M.A.E., I.M., E.G.-I., A.I.F., R.P.-A., A.G.-M., T.M., R.S.-R., J.E., R.Y., F.F.-A., J.B.)
| | - Pablo Martínez-Legazpi
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, and CIBERCV, Spain (M.T., P.M.-L., M.A.E., I.M., E.G.-I., A.I.F., R.P.-A., A.G.-M., T.M., R.S.-R., J.E., R.Y., F.F.-A., J.B.)
- Department of Mathematical Physics and Fluids, Facultad de Ciencias, Universidad Nacional de Educación a Distancia, UNED, Spain (P.M.-L.)
| | - M. Ángeles Espinosa
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, and CIBERCV, Spain (M.T., P.M.-L., M.A.E., I.M., E.G.-I., A.I.F., R.P.-A., A.G.-M., T.M., R.S.-R., J.E., R.Y., F.F.-A., J.B.)
| | - Aurore Lyon
- Department of Biomedical Engineering, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, the Netherlands (A.L., T.A., T.D., J.L.)
| | - Irene Méndez
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, and CIBERCV, Spain (M.T., P.M.-L., M.A.E., I.M., E.G.-I., A.I.F., R.P.-A., A.G.-M., T.M., R.S.-R., J.E., R.Y., F.F.-A., J.B.)
| | - Enrique Gutiérrez-Ibañes
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, and CIBERCV, Spain (M.T., P.M.-L., M.A.E., I.M., E.G.-I., A.I.F., R.P.-A., A.G.-M., T.M., R.S.-R., J.E., R.Y., F.F.-A., J.B.)
| | - Ana I. Fernández
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, and CIBERCV, Spain (M.T., P.M.-L., M.A.E., I.M., E.G.-I., A.I.F., R.P.-A., A.G.-M., T.M., R.S.-R., J.E., R.Y., F.F.-A., J.B.)
| | - Raquel Prieto-Arévalo
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, and CIBERCV, Spain (M.T., P.M.-L., M.A.E., I.M., E.G.-I., A.I.F., R.P.-A., A.G.-M., T.M., R.S.-R., J.E., R.Y., F.F.-A., J.B.)
| | - Ana González-Mansilla
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, and CIBERCV, Spain (M.T., P.M.-L., M.A.E., I.M., E.G.-I., A.I.F., R.P.-A., A.G.-M., T.M., R.S.-R., J.E., R.Y., F.F.-A., J.B.)
| | - Theo Arts
- Department of Biomedical Engineering, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, the Netherlands (A.L., T.A., T.D., J.L.)
| | - Tammo Delhaas
- Department of Biomedical Engineering, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, the Netherlands (A.L., T.A., T.D., J.L.)
| | - Teresa Mombiela
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, and CIBERCV, Spain (M.T., P.M.-L., M.A.E., I.M., E.G.-I., A.I.F., R.P.-A., A.G.-M., T.M., R.S.-R., J.E., R.Y., F.F.-A., J.B.)
| | - Ricardo Sanz-Ruiz
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, and CIBERCV, Spain (M.T., P.M.-L., M.A.E., I.M., E.G.-I., A.I.F., R.P.-A., A.G.-M., T.M., R.S.-R., J.E., R.Y., F.F.-A., J.B.)
| | - Jaime Elízaga
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, and CIBERCV, Spain (M.T., P.M.-L., M.A.E., I.M., E.G.-I., A.I.F., R.P.-A., A.G.-M., T.M., R.S.-R., J.E., R.Y., F.F.-A., J.B.)
| | - Raquel Yotti
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, and CIBERCV, Spain (M.T., P.M.-L., M.A.E., I.M., E.G.-I., A.I.F., R.P.-A., A.G.-M., T.M., R.S.-R., J.E., R.Y., F.F.-A., J.B.)
| | - Carsten Tschöpe
- Berlin Institute of Health/Center for Regenerative Therapy (BCRT) at Charite, and Department of Cardiology, Campus Virchow (CVK), Charité Universitätsmedizin, and DZHK (German Center for Cardiovascular Research), partner site Berlin, Germany (C.T.)
| | - Francisco Fernández-Avilés
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, and CIBERCV, Spain (M.T., P.M.-L., M.A.E., I.M., E.G.-I., A.I.F., R.P.-A., A.G.-M., T.M., R.S.-R., J.E., R.Y., F.F.-A., J.B.)
| | - Joost Lumens
- Department of Biomedical Engineering, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, the Netherlands (A.L., T.A., T.D., J.L.)
| | - Javier Bermejo
- Department of Cardiology, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, and CIBERCV, Spain (M.T., P.M.-L., M.A.E., I.M., E.G.-I., A.I.F., R.P.-A., A.G.-M., T.M., R.S.-R., J.E., R.Y., F.F.-A., J.B.)
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5
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Liu W, Labus KM, Ahern M, LeBar K, Avazmohammadi R, Puttlitz CM, Wang Z. Strain-Dependent Stress Relaxation Behavior of Healthy Right Ventricular Free Wall. Acta Biomater 2022; 152:290-299. [PMID: 36030049 DOI: 10.1016/j.actbio.2022.08.043] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Revised: 07/31/2022] [Accepted: 08/17/2022] [Indexed: 11/01/2022]
Abstract
The increasing evidence of stress-strain hysteresis in large animal or human myocardium calls for extensive characterizations of the passive viscoelastic behavior of the myocardium. Several recent studies have investigated and modeled the viscoelasticity of the left ventricle while the right ventricle (RV) viscoelasticity remains poorly understood. Our goal was to characterize the biaxial viscoelastic behavior of RV free wall (RVFW) using two modeling approaches. We applied both quasi-linear viscoelastic (QLV) and nonlinear viscoelastic (NLV) theories to experimental stress relaxation data from healthy adult ovine. A three-term Prony series relaxation function combined with an Ogden strain energy density function were used in the QLV modeling, while a power-law formulation was adopted in the NLV approach. The ovine RVFW exhibited an anisotropic and strain-dependent viscoelastic behavior relative to anatomical coordinates, and the NLV model showed a higher capacity in predicting strain-dependent stress relaxation than the QLV model. From the QLV fitting, the relaxation term associated with the largest time constant played the dominant role in the overall relaxation behavior at all strains from early to late diastole, whereas the term associated with the smallest time constant was pronounced only at low strains at early diastole. From the NLV fitting, the parameters showed a nonlinear dependence on the strain. Overall, our study characterized the anisotropic, nonlinear viscoelasticity to capture the elastic and viscous resistances of the RVFW during diastole. These findings deepen our understanding of RV myocardium dynamic mechanical properties. STATEMENT OF SIGNIFICANCE: Although significant progress has been made to understand the passive elastic behavior of the right ventricle free wall (RVFW), its viscoelastic behavior remains poorly understood. In this study, we originally applied both quasi-linear viscoelastic (QLV) and nonlinear viscoelastic (NLV) models to published experimental data from healthy ovine RVFW. Our results revealed an anisotropic and strain-dependent viscoelastic behavior of the RVFW. The parameters from the NLV fitting showed nonlinear relationships with the strain, and the NLV model showed a higher capacity in predicting strain-dependent stress relaxation than the QLV model. These findings characterize the anisotropic, nonlinear viscoelasticity of RVFW to fully capture the total (elastic and viscous) resistance that is critical to diastolic function.
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Affiliation(s)
- Wenqiang Liu
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO, 80523, USA
| | - Kevin M Labus
- Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, 80523, USA
| | - Matt Ahern
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO, 80523, USA; Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, 80523, USA
| | - Kristen LeBar
- Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, 80523, USA
| | - Reza Avazmohammadi
- Department of Biomedical Engineering, Texas A&M University, College Station, TX, 77843, USA; J. Mike Walker '66 Department of Mechanical Engineering, Texas A&M University, College Station, TX, 77843, USA; Department of Cardiovascular Sciences, Houston Methodist Academic Institute, Houston, TX, 77030, USA
| | - Christian M Puttlitz
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO, 80523, USA; Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, 80523, USA
| | - Zhijie Wang
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO, 80523, USA; Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, 80523, USA.
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6
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Weidner S, Tomalka A, Rode C, Siebert T. How velocity impacts eccentric force generation of fully activated skinned skeletal muscle fibers in long stretches. J Appl Physiol (1985) 2022; 133:223-233. [PMID: 35652830 DOI: 10.1152/japplphysiol.00735.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Eccentric muscle contractions are fundamental to everyday life. They occur markedly in jumping, running, and accidents. Following an initial force rise, stretching of a fully activated muscle can result in a phase of decreasing force ('Give') followed by force redevelopment. However, how the stretch velocity affects 'Give' and force redevelopment remains largely unknown. We investigated the force produced by fully activated single skinned fibers of rat extensor digitorum longus muscles during long stretches. Fibers were pulled from length .85 to 1.3 optimal fiber length at a rate of 1, 10 and 100% of the estimated maximum shortening velocity. 'Give' was absent in slow stretches. Medium and fast stretches yielded a clear 'Give'. After the initial force peak, forces decreased by 11.2% and 27.8% relative to the initial peak force before rising again. During the last half of the stretch (from 1.07 to 1.3 optimal fiber length, which is within the range of the expected descending limb of the force-length relationship), the linear force slope tripled from slow to medium stretch and increased further by 60% from medium to fast stretch. These results are compatible with forcible cross-bridge detachment and re-development of a cross-bridge distribution, and a viscoelastic titin contribution to fiber force. Accounting for these results can improve muscle models and predictions of multi-body simulations.
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Affiliation(s)
- Sven Weidner
- nstitute of Sport and Movement Science, Department of Motion and Exercise Science, University of Stuttgart, Stuttgart, Germany
| | - André Tomalka
- nstitute of Sport and Movement Science, Department of Motion and Exercise Science, University of Stuttgart, Stuttgart, Germany
| | - Christian Rode
- nstitute of Sport Science, Department of Biomechanics, University of Rostock, Rostock, Germany
| | - Tobias Siebert
- nstitute of Sport and Movement Science, Department of Motion and Exercise Science, University of Stuttgart, Stuttgart, Germany.,Stuttgart Center of Simulation Science, University of Stuttgart, Stuttgart, Germany
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7
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Olsen NT, Göransson C, Vejlstrup N, Carlsen J. Myocardial adaptation and exercise performance in patients with pulmonary arterial hypertension assessed with patient-specific computer simulations. Am J Physiol Heart Circ Physiol 2021; 321:H865-H880. [PMID: 34448636 DOI: 10.1152/ajpheart.00442.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Myocardial function and exercise reserve are important determinants of outcome in pulmonary arterial hypertension (PAH) but are incompletely understood. For this study, we performed subject-specific computer simulations, based on invasive measurements and cardiac magnetic resonance imaging (CMR), to investigate whole circulation properties in PAH at rest and exercise and determinants of exercise reserve. CMR and right heart catheterization were performed in nine patients with idiopathic PAH, and CMR in 10 healthy controls. CMR during exercise was performed in seven patients with PAH. A full-circulation computer model was developed, and model parameters were optimized at the individual level. Patient-specific simulations were used to analyze the effect of right ventricular (RV) inotropic reserve on exercise performance. Simulations achieved a high consistency with observed data. RV contractile force was increased in patients with PAH (127.1 ± 28.7 kPa vs. 70.5 ± 14.5 kPa, P < 0.001), whereas left ventricular contractile force was reduced (107.5 ± 17.5 kPa vs. 133.9 ± 10.3 kPa, P = 0.002). During exercise, RV contractile force increased by 1.56 ± 0.17, P = 0.001. In silico experiments confirmed RV inotropic reserve as the important limiting factor for cardiac output. Subject-specific computer simulation of myocardial mechanics in PAH is feasible and can be used to evaluate myocardial performance. With this method, we demonstrate marked functional myocardial adaptation to PAH in the resting state, primarily composed of increased contractile force development by RV myofibers, and we show the negative impact of reduced RV inotropic reserve on cardiac output during exercise.NEW & NOTEWORTHY Computer simulations of the myocardial mechanics and hemodynamics of rest and exercise were performed in nine patients with pulmonary arterial hypertension and 10 control subjects, with the use of data from invasive catheterization and from cardiac magnetic resonance. This approach allowed a detailed analysis of myocardial adaptation to pulmonary arterial hypertension and showed how reduction in right ventricular inotropic reserve is the important limiting factor for an increase in cardiac output during exercise.
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Affiliation(s)
- Niels Thue Olsen
- Department of Cardiology, Copenhagen University Hospital-Herlev and Gentofte, Copenhagen, Denmark.,Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Christoffer Göransson
- Department of Cardiology, Copenhagen University Hospital-Rigshospitalet, Copenhagen, Denmark
| | - Niels Vejlstrup
- Department of Cardiology, Copenhagen University Hospital-Rigshospitalet, Copenhagen, Denmark
| | - Jørn Carlsen
- Department of Cardiology, Copenhagen University Hospital-Rigshospitalet, Copenhagen, Denmark.,Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
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8
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Ma W, Henze M, Anderson RL, Gong H, Wong FL, Del Rio CL, Irving T. The Super-Relaxed State and Length Dependent Activation in Porcine Myocardium. Circ Res 2021; 129:617-630. [PMID: 34365814 DOI: 10.1161/circresaha.120.318647] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Weikang Ma
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago (W.M., H.G., T.I.)
| | - Marcus Henze
- MyoKardia Inc, Brisbane, CA (M.H., R.L.A., F.L.W., C.L.d.R.)
| | | | - Henry Gong
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago (W.M., H.G., T.I.)
| | - Fiona L Wong
- MyoKardia Inc, Brisbane, CA (M.H., R.L.A., F.L.W., C.L.d.R.)
| | | | - Thomas Irving
- BioCAT, Department of Biological Sciences, Illinois Institute of Technology, Chicago (W.M., H.G., T.I.)
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9
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Caporizzo MA, Prosser BL. Need for Speed: The Importance of Physiological Strain Rates in Determining Myocardial Stiffness. Front Physiol 2021; 12:696694. [PMID: 34393820 PMCID: PMC8361601 DOI: 10.3389/fphys.2021.696694] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Accepted: 07/06/2021] [Indexed: 01/07/2023] Open
Abstract
The heart is viscoelastic, meaning its compliance is inversely proportional to the speed at which it stretches. During diastolic filling, the left ventricle rapidly expands at rates where viscoelastic forces impact ventricular compliance. In heart disease, myocardial viscoelasticity is often increased and can directly impede diastolic filling to reduce cardiac output. Thus, treatments that reduce myocardial viscoelasticity may provide benefit in heart failure, particularly for patients with diastolic heart failure. Yet, many experimental techniques either cannot or do not characterize myocardial viscoelasticity, and our understanding of the molecular regulators of viscoelasticity and its impact on cardiac performance is lacking. Much of this may stem from a reliance on techniques that either do not interrogate viscoelasticity (i.e., use non-physiological rates of strain) or techniques that compromise elements that contribute to viscoelasticity (i.e., skinned or permeabilized muscle preparations that compromise cytoskeletal integrity). Clinically, cardiac viscoelastic characterization is challenging, requiring the addition of strain-rate modulation during invasive hemodynamics. Despite these challenges, data continues to emerge demonstrating a meaningful contribution of viscoelasticity to cardiac physiology and pathology, and thus innovative approaches to characterize viscoelasticity stand to illuminate fundamental properties of myocardial mechanics and facilitate the development of novel therapeutic strategies.
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Affiliation(s)
- Matthew A Caporizzo
- Department of Physiology, Perelman School of Medicine, The University of Pennsylvania, Philadelphia, PA, United States
| | - Benjamin L Prosser
- Department of Physiology, Perelman School of Medicine, The University of Pennsylvania, Philadelphia, PA, United States
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10
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Tomalka A, Weidner S, Hahn D, Seiberl W, Siebert T. Power Amplification Increases With Contraction Velocity During Stretch-Shortening Cycles of Skinned Muscle Fibers. Front Physiol 2021; 12:644981. [PMID: 33868012 PMCID: PMC8044407 DOI: 10.3389/fphys.2021.644981] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 03/08/2021] [Indexed: 01/25/2023] Open
Abstract
Muscle force, work, and power output during concentric contractions (active muscle shortening) are increased immediately following an eccentric contraction (active muscle lengthening). This increase in performance is known as the stretch-shortening cycle (SSC)-effect. Recent findings demonstrate that the SSC-effect is present in the sarcomere itself. More recently, it has been suggested that cross-bridge (XB) kinetics and non-cross-bridge (non-XB) structures (e.g., titin and nebulin) contribute to the SSC-effect. As XBs and non-XB structures are characterized by a velocity dependence, we investigated the impact of stretch-shortening velocity on the SSC-effect. Accordingly, we performed in vitro isovelocity ramp experiments with varying ramp velocities (30, 60, and 85% of maximum contraction velocity for both stretch and shortening) and constant stretch-shortening magnitudes (17% of the optimum sarcomere length) using single skinned fibers of rat soleus muscles. The different contributions of XB and non-XB structures to force production were identified using the XB-inhibitor Blebbistatin. We show that (i) the SSC-effect is velocity-dependent-since the power output increases with increasing SSC-velocity. (ii) The energy recovery (ratio of elastic energy storage and release in the SSC) is higher in the Blebbistatin condition compared with the control condition. The stored and released energy in the Blebbistatin condition can be explained by the viscoelastic properties of the non-XB structure titin. Consequently, our experimental findings suggest that the energy stored in titin during the eccentric phase contributes to the SSC-effect in a velocity-dependent manner.
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Affiliation(s)
- André Tomalka
- Department of Motion and Exercise Science, University of Stuttgart, Stuttgart, Germany
| | - Sven Weidner
- Department of Motion and Exercise Science, University of Stuttgart, Stuttgart, Germany
| | - Daniel Hahn
- Human Movement Science, Faculty of Sports Science, Ruhr University Bochum, Bochum, Germany
- School of Human Movement and Nutrition Sciences, University of Queensland, Brisbane, QLD, Australia
| | - Wolfgang Seiberl
- Human Movement Science, Bundeswehr University Munich, Neubiberg, Germany
| | - Tobias Siebert
- Department of Motion and Exercise Science, University of Stuttgart, Stuttgart, Germany
- Stuttgart Center for Simulation Science, University of Stuttgart, Stuttgart, Germany
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11
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Khokhlova A, Konovalov P, Iribe G, Solovyova O, Katsnelson L. The Effects of Mechanical Preload on Transmural Differences in Mechano-Calcium-Electric Feedback in Single Cardiomyocytes: Experiments and Mathematical Models. Front Physiol 2020; 11:171. [PMID: 32256377 PMCID: PMC7091561 DOI: 10.3389/fphys.2020.00171] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Accepted: 02/13/2020] [Indexed: 11/13/2022] Open
Abstract
Transmural differences in ventricular myocardium are maintained by electromechanical coupling and mechano-calcium/mechano-electric feedback. In the present study, we experimentally investigated the influence of preload on the force characteristics of subendocardial (Endo) and subepicardial (Epi) single ventricular cardiomyocytes stretched by up to 20% from slack sarcomere length (SL) and analyzed the results with the help of mathematical modeling. Mathematical models of Endo and Epi cells, which accounted for regional heterogeneity in ionic currents, Ca2+ handling, and myofilament contractile mechanisms, showed that a greater slope of the active tension–length relationship observed experimentally in Endo cardiomyocytes could be explained by greater length-dependent Ca2+ activation in Endo cells compared with Epi ones. The models also predicted that greater length dependence of Ca2+ activation in Endo cells compared to Epi ones underlies, via mechano-calcium-electric feedback, the reduction in the transmural gradient in action potential duration (APD) at a higher preload. However, the models were unable to reproduce the experimental data on a decrease of the transmural gradient in the time to peak contraction between Endo and Epi cells at longer end-diastolic SL. We hypothesize that preload-dependent changes in viscosity should be involved alongside the Frank–Starling effects to regulate the transmural gradient in length-dependent changes in the time course of contraction of Endo and Epi cardiomyocytes. Our experimental data and their analysis based on mathematical modeling give reason to believe that mechano-calcium-electric feedback plays a critical role in the modulation of electrophysiological and contractile properties of myocytes across the ventricular wall.
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Affiliation(s)
- Anastasia Khokhlova
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, Russia.,Institute of Natural Sciences and Mathematics, Ural Federal University, Yekaterinburg, Russia
| | - Pavel Konovalov
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, Russia
| | - Gentaro Iribe
- Department of Physiology, Asahikawa Medical University, Hokkaido, Japan.,Department of Cardiovascular Physiology, Okayama University, Okayama, Japan
| | - Olga Solovyova
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, Russia.,Institute of Natural Sciences and Mathematics, Ural Federal University, Yekaterinburg, Russia
| | - Leonid Katsnelson
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, Russia.,Institute of Natural Sciences and Mathematics, Ural Federal University, Yekaterinburg, Russia
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12
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Hayabuchi Y. Right ventricular myocardial stiffness and relaxation components by kinematic model-based analysis. THE JOURNAL OF MEDICAL INVESTIGATION 2020; 67:11-20. [DOI: 10.2152/jmi.67.11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Affiliation(s)
- Yasunobu Hayabuchi
- Department of Pediatrics, Department of Pediatrics and community medicine, Tokushima University, Tokushima, Japan
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13
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Powers JD, Bianco P, Pertici I, Reconditi M, Lombardi V, Piazzesi G. Contracting striated muscle has a dynamic I-band spring with an undamped stiffness 100 times larger than the passive stiffness. J Physiol 2020; 598:331-345. [PMID: 31786814 DOI: 10.1113/jp278713] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Accepted: 11/21/2019] [Indexed: 12/20/2022] Open
Abstract
KEY POINTS Fast sarcomere-level mechanics in contracting intact fibres from frog skeletal muscle reveal an I-band spring with an undamped stiffness 100 times larger than the known static stiffness. This undamped stiffness remains constant in the range of sarcomere length 2.7-3.1 µm, showing the ability of the I-band spring to adapt its length to the width of the I-band. The stiffness and tunability of the I-band spring implicate titin as a force contributor that, during contraction, allows weaker half-sarcomeres to equilibrate with in-series stronger half-sarcomeres, preventing the development of sarcomere length inhomogeneity. This work opens new possibilities for the detailed in situ description of the structural-functional basis of muscle dysfunctions related to mutations or site-directed mutagenesis in titin that alter the I-band stiffness. ABSTRACT Force and shortening in the muscle sarcomere are due to myosin motors from thick filaments pulling nearby actin filaments toward the sarcomere centre. Thousands of serially linked sarcomeres in muscle make the shortening (and the shortening speed) macroscopic, while the intrinsic instability of in-series force generators is likely prevented by the cytoskeletal protein titin that connects the thick filament with the sarcomere end, working as an I-band spring that accounts for the rise of passive force with sarcomere length (SL). However, current estimates of titin stiffness, deduced from the passive force-SL relation and single molecule mechanics, are much smaller than what is required to avoid the development of large inhomogeneities among sarcomeres. In this work, using 4 kHz stiffness measurements on a population of sarcomeres selected along an intact fibre isolated from frog skeletal muscle contracting at different SLs (temperature 4°C), we measure the undamped stiffness of an I-band spring that at SL > 2.7 µm attains a maximum constant value of ∼6 pN nm-1 per half-thick filament, two orders of magnitude larger than expected from titin-related passive force. We conclude that a titin-like dynamic spring in the I-band, made by an undamped elastic element in-series with damped elastic elements, adapts its length to the SL with kinetics that provide force balancing among serially linked sarcomeres during contraction. In this way, the I-band spring plays a fundamental role in preventing the development of SL inhomogeneity.
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Affiliation(s)
- Joseph D Powers
- PhysioLab, University of Florence, Via G. Sansone, 1, 50019 Sesto Fiorentino, Florence, Italy
- Bioengineering, University of Washington, 3720 15th Ave NE, Seattle, WA, 98105, USA
| | - Pasquale Bianco
- PhysioLab, University of Florence, Via G. Sansone, 1, 50019 Sesto Fiorentino, Florence, Italy
| | - Irene Pertici
- PhysioLab, University of Florence, Via G. Sansone, 1, 50019 Sesto Fiorentino, Florence, Italy
| | - Massimo Reconditi
- PhysioLab, University of Florence, Via G. Sansone, 1, 50019 Sesto Fiorentino, Florence, Italy
| | - Vincenzo Lombardi
- PhysioLab, University of Florence, Via G. Sansone, 1, 50019 Sesto Fiorentino, Florence, Italy
| | - Gabriella Piazzesi
- PhysioLab, University of Florence, Via G. Sansone, 1, 50019 Sesto Fiorentino, Florence, Italy
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14
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Hayabuchi Y, Homma Y, Kagami S. Right Ventricular Myocardial Stiffness and Relaxation Components by Kinematic Model-Based Transtricuspid Flow Analysis in Children and Adolescents with Pulmonary Arterial Hypertension. ULTRASOUND IN MEDICINE & BIOLOGY 2019; 45:1999-2009. [PMID: 31122811 DOI: 10.1016/j.ultrasmedbio.2019.04.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 04/14/2019] [Accepted: 04/24/2019] [Indexed: 06/09/2023]
Abstract
We hypothesized that the kinematic model-based parameters obtained from the transtricuspid E-wave would be useful for evaluating the right ventricular diastolic property in pediatric pulmonary arterial hypertension (PAH) patients. The model was parametrized by stiffness/elastic recoil k, relaxation/damping c and load x. These parameters were determined as the solution of m⋅d2x/dt2 + c⋅dx/dt + kx = 0, which is based on the theory that the E-wave contour is determined by the interplay of stiffness/restoring force, damping/relaxation force and load. The PAH group had a significantly higher k and c compared with the control group (182.5 ± 72.4 g/s vs. 135.7 ± 49.5 g/s2, p = 0.0232, and 21.9 ± 6.5 g/s vs. 10.6 ± 5.2 g/s, p <0.0001, respectively). These results indicate that in the PAH group, the right ventricle had higher stiffness/elastic recoil and inferior cross-bridge relaxation. The present findings indicate the feasibility and utility of using kinematic model parameters to assess right ventricular diastolic function.
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Affiliation(s)
| | - Yukako Homma
- Department of Pediatrics, Tokushima University, Tokushima, Japan
| | - Shoji Kagami
- Department of Pediatrics, Tokushima University, Tokushima, Japan
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15
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Leite-Moreira AM, Almeida-Coelho J, Neves JS, Pires AL, Ferreira-Martins J, Castro-Ferreira R, Ladeiras-Lopes R, Conceição G, Miranda-Silva D, Rodrigues P, Hamdani N, Herwig M, Falcão-Pires I, Paulus WJ, Linke WA, Lourenço AP, Leite-Moreira AF. Stretch-induced compliance: a novel adaptive biological mechanism following acute cardiac load. Cardiovasc Res 2019; 114:656-667. [PMID: 29401264 DOI: 10.1093/cvr/cvy026] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2017] [Accepted: 01/30/2018] [Indexed: 01/09/2023] Open
Abstract
Aims The heart is constantly challenged with acute bouts of stretching or overload. Systolic adaptations to these challenges are known but adaptations in diastolic stiffness remain unknown. We evaluated adaptations in myocardial stiffness due to acute stretching and characterized the underlying mechanisms. Methods and results Left ventricles (LVs) of intact rat hearts, rabbit papillary muscles and myocardial strips from cardiac surgery patients were stretched. After stretching, there was a sustained >40% decrease in end-diastolic pressure (EDP) or passive tension (PT) for 15 min in all species and experimental preparations. Stretching by volume loading in volunteers and cardiac surgery patients resulted in E/E' and EDP decreases, respectively, after sustained stretching. Stretched samples had increased myocardial cGMP levels, increased phosphorylated vasodilator-stimulated phosphoprotein phosphorylation, as well as, increased titin phosphorylation, which was reduced by prior protein kinase G (PKG) inhibition (PKGi). Skinned cardiomyocytes from stretched and non-stretched myocardia were studied. Skinned cardiomyocytes from stretched hearts showed decreased PT, which was abrogated by protein phosphatase incubation; whereas those from non-stretched hearts decreased PT after PKG incubation. Pharmacological studies assessed the role of nitric oxide (NO) and natriuretic peptides (NPs). PT decay after stretching was significantly reduced by combined NP antagonism, NO synthase inhibition and NO scavenging, or by PKGi. Response to stretching was remarkably reduced in a rat model of LV hypertrophy, which also failed to increase titin phosphorylation. Conclusions We describe and translate to human physiology a novel adaptive mechanism, partly mediated by titin phosphorylation through cGMP-PKG signalling, whereby myocardial compliance increases in response to acute stretching. This mechanism may not function in the hypertrophic heart.
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Affiliation(s)
- André M Leite-Moreira
- Department of Surgery and Physiology and Cardiovascular Research Centre, Faculty of Medicine, University of Porto, Porto, Portugal.,Department of Anaesthesiology, São João Hospital Centre, Porto, Portugal
| | - João Almeida-Coelho
- Department of Surgery and Physiology and Cardiovascular Research Centre, Faculty of Medicine, University of Porto, Porto, Portugal
| | - João S Neves
- Department of Surgery and Physiology and Cardiovascular Research Centre, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Ana L Pires
- Department of Surgery and Physiology and Cardiovascular Research Centre, Faculty of Medicine, University of Porto, Porto, Portugal
| | - João Ferreira-Martins
- Department of Surgery and Physiology and Cardiovascular Research Centre, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Ricardo Castro-Ferreira
- Department of Surgery and Physiology and Cardiovascular Research Centre, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Ricardo Ladeiras-Lopes
- Department of Surgery and Physiology and Cardiovascular Research Centre, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Glória Conceição
- Department of Surgery and Physiology and Cardiovascular Research Centre, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Daniela Miranda-Silva
- Department of Surgery and Physiology and Cardiovascular Research Centre, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Patrícia Rodrigues
- Department of Surgery and Physiology and Cardiovascular Research Centre, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Nazha Hamdani
- Department of Cardiovascular Physiology, Ruhr University Bochum, Germany
| | - Melissa Herwig
- Department of Cardiovascular Physiology, Ruhr University Bochum, Germany
| | - Inês Falcão-Pires
- Department of Surgery and Physiology and Cardiovascular Research Centre, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Walter J Paulus
- Department of Physiology, Institute for Cardiovascular Research, VU University Medical Centre, Amsterdam, The Netherlands
| | | | - André P Lourenço
- Department of Surgery and Physiology and Cardiovascular Research Centre, Faculty of Medicine, University of Porto, Porto, Portugal.,Department of Anaesthesiology, São João Hospital Centre, Porto, Portugal
| | - Adelino F Leite-Moreira
- Department of Surgery and Physiology and Cardiovascular Research Centre, Faculty of Medicine, University of Porto, Porto, Portugal.,Department of Cardiothoracic Surgery, São João Hospital Centre, Porto, Portugal
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16
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Tomalka A, Röhrle O, Han JC, Pham T, Taberner AJ, Siebert T. Extensive eccentric contractions in intact cardiac trabeculae: revealing compelling differences in contractile behaviour compared to skeletal muscles. Proc Biol Sci 2019; 286:20190719. [PMID: 31138072 DOI: 10.1098/rspb.2019.0719] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Force enhancement (FE) is a phenomenon that is present in skeletal muscle. It is characterized by progressive forces upon active stretching-distinguished by a linear rise in force-and enhanced isometric force following stretching (residual FE (RFE)). In skeletal muscle, non-cross-bridge (XB) structures may account for this behaviour. So far, it is unknown whether differences between non-XB structures within the heart and skeletal muscle result in deviating contractile behaviour during and after eccentric contractions. Thus, we investigated the force response of intact cardiac trabeculae during and after isokinetic eccentric muscle contractions (10% of maximum shortening velocity) with extensive magnitudes of stretch (25% of optimum muscle length). The different contributions of XB and non-XB structures to the total muscle force were revealed by using an actomyosin inhibitor. For cardiac trabeculae, we found that the force-length dynamics during long stretch were similar to the total isometric force-length relation. This indicates that no (R)FE is present in cardiac muscle while stretching the muscle from 0.75 to 1.0 optimum muscle length. This finding is in contrast with the results obtained for skeletal muscle, in which (R)FE is present. Our data support the hypothesis that titin stiffness does not increase with activation in cardiac muscle.
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Affiliation(s)
- André Tomalka
- 1 Department of Motion and Exercise Science, University of Stuttgart , Stuttgart , Germany
| | - Oliver Röhrle
- 2 Institute of Applied Mechanics (Civil Engineering), University of Stuttgart , Stuttgart , Germany.,3 Cluster of Excellence for Simulation Technology (SimTech) , Stuttgart , Germany
| | - June-Chiew Han
- 4 Auckland Bioengineering Institute, The University of Auckland , Auckland , New Zealand
| | - Toan Pham
- 5 Department of Physiology, The University of Auckland , Auckland , New Zealand
| | - Andrew J Taberner
- 4 Auckland Bioengineering Institute, The University of Auckland , Auckland , New Zealand.,6 Department of Engineering Science, The University of Auckland , Auckland , New Zealand
| | - Tobias Siebert
- 1 Department of Motion and Exercise Science, University of Stuttgart , Stuttgart , Germany
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17
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Yakupova EI, Vikhlyantsev IM, Lobanov MY, Galzitskaya OV, Bobylev AG. Amyloid Properties of Titin. BIOCHEMISTRY (MOSCOW) 2018. [PMID: 29523065 DOI: 10.1134/s0006297917130077] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
This review considers data on structural and functional features of titin, on the role of this protein in determination of mechanical properties of sarcomeres, and on specific features of regulation of the stiffness and elasticity of its molecules, amyloid aggregation of this protein in vitro, and possibilities of formation of intramolecular amyloid structure in vivo. Molecular mechanisms are described of protection of titin against aggregation in muscle cells. Based on the data analysis, it is supposed that titin and the formed by it elastic filaments have features of amyloid.
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Affiliation(s)
- E I Yakupova
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
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18
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Lourenço AP, Leite-Moreira AF, Balligand JL, Bauersachs J, Dawson D, de Boer RA, de Windt LJ, Falcão-Pires I, Fontes-Carvalho R, Franz S, Giacca M, Hilfiker-Kleiner D, Hirsch E, Maack C, Mayr M, Pieske B, Thum T, Tocchetti CG, Brutsaert DL, Heymans S. An integrative translational approach to study heart failure with preserved ejection fraction: a position paper from the Working Group on Myocardial Function of the European Society of Cardiology. Eur J Heart Fail 2017; 20:216-227. [DOI: 10.1002/ejhf.1059] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Revised: 09/08/2017] [Accepted: 10/01/2017] [Indexed: 12/28/2022] Open
Affiliation(s)
- Andre P. Lourenço
- Department of Surgery and Physiology & Cardiovascular Research Centre, Faculty of Medicine; University of Porto; Portugal
| | - Adelino F. Leite-Moreira
- Department of Surgery and Physiology & Cardiovascular Research Centre, Faculty of Medicine; University of Porto; Portugal
| | - Jean-Luc Balligand
- Pole of Pharmacology and Therapeutics, Institut de Recherche Experimentale et Clinique (IREC), and Clinique Universitaire Saint-Luc; Université catholique de Louvain; Brussels Belgium
| | - Johann Bauersachs
- Klinik fuer Kardiologie und Angiologie Medizinische Hochschule; Hannover Germany
| | - Dana Dawson
- Reader in Cardiovascular Medicine and Honorary Consultant Cardiologist, University of Aberdeen; UK
| | | | - Leon J. de Windt
- Department of Cardiology, CARIM School for Cardiovascular Diseases Faculty of Health, Medicine and Life Sciences; Maastricht University; The Netherlands
| | - Inês Falcão-Pires
- Department of Surgery and Physiology & Cardiovascular Research Centre, Faculty of Medicine; University of Porto; Portugal
| | - Ricardo Fontes-Carvalho
- Department of Surgery and Physiology & Cardiovascular Research Centre, Faculty of Medicine; University of Porto; Portugal
| | - Stefan Franz
- University Hospital Halle; Department of Internal Medicine III; Halle, Saale Germany
| | - Mauro Giacca
- Molecular Medicine Laboratory, International Centre for Genetic Engineering and Biotechnology (ICGEB) & Department of Medical, Surgical and Health Sciences; University of Trieste; Trieste Italy
| | | | - Emilio Hirsch
- Department of Molecular Biotechnology and Health Sciences; University of Turin; Torino Italy
| | - Christoph Maack
- Klinik für Innere Medizin III; Universitätsklinikum des Saarlandes; Homburg Germany
| | - Manuel Mayr
- The James Black Centre and King's British Heart Foundation Centre, King's College; University of London; London UK
| | - Burkert Pieske
- Department of Cardiology, Charité, Campus Virchow & German Centre for Cardiovascular Research (DZHK), Charite & Berlin Institute of Health, Berlin; Germany & Department of Cardiology, University of Graz; Graz Austria
| | - Thomas Thum
- Institute of Molecular and Translational Therapeutic Strategies (IMTTS), IFB-Tx, & REBIRTH Excellence Cluster, Hannover Medical School, Hannover, Germany, and National Heart and Lung Institute; Imperial College London; UK
| | - Carlo G. Tocchetti
- Department of Translational Medical Sciences, Division of Internal Medicine; Federico II University; Naples Italy
| | | | - Stephane Heymans
- Department of Cardiology, Maastricht University Medical Center & CARIM; Maastricht University; Maastricht The Netherlands
- Cardiovascular Sciences; University of Leuven; Belgium
- Netherlands Heart Institute; Utrecht The Netherlands
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19
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Lalande S, Mueller PJ, Chung CS. The link between exercise and titin passive stiffness. Exp Physiol 2017; 102:1055-1066. [PMID: 28762234 DOI: 10.1113/ep086275] [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: 05/15/2017] [Accepted: 07/11/2017] [Indexed: 12/27/2022]
Abstract
NEW FINDINGS What is the topic of this review? This review focuses on how in vivo and molecular measurements of cardiac passive stiffness can predict exercise tolerance and how exercise training can reduce cardiac passive stiffness. What advances does it highlight? This review highlights advances in understanding the relationship between molecular (titin-based) and in vivo (left ventricular) passive stiffness, how passive stiffness modifies exercise tolerance, and how exercise training may be therapeutic for cardiac diseases with increased passive stiffness. Exercise can help alleviate the negative effects of cardiovascular disease and cardiovascular co-morbidities associated with sedentary behaviour; this may be especially true in diseases that are associated with increased left ventricular passive stiffness. In this review, we discuss the inverse relationship between exercise tolerance and cardiac passive stiffness. Passive stiffness is the physical property of cardiac muscle to produce a resistive force when stretched, which, in vivo, is measured using the left ventricular end diastolic pressure-volume relationship or is estimated using echocardiography. The giant elastic protein titin is the major contributor to passive stiffness at physiological muscle (sarcomere) lengths. Passive stiffness can be modified by altering titin isoform size or by post-translational modifications. In both human and animal models, increased left ventricular passive stiffness is associated with reduced exercise tolerance due to impaired diastolic filling, suggesting that increased passive stiffness predicts reduced exercise tolerance. At the same time, exercise training itself may induce both short- and long-term changes in titin-based passive stiffness, suggesting that exercise may be a treatment for diseases associated with increased passive stiffness. Direct modification of passive stiffness to improve exercise tolerance is a potential therapeutic approach. Titin passive stiffness itself may be a treatment target based on the recent discovery of RNA binding motif 20, which modifies titin isoform size and passive stiffness. Translating these discoveries that link exercise and left ventricular passive stiffness may provide new methods to enhance exercise tolerance and treat patients with cardiovascular disease.
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Affiliation(s)
- Sophie Lalande
- Department of Kinesiology & Health Education, The University of Texas at Austin, Austin, TX, USA
| | | | - Charles S Chung
- Department of Physiology, Wayne State University, Detroit, MI, USA
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20
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Slater RE, Strom JG, Granzier H. Effect of exercise on passive myocardial stiffness in mice with diastolic dysfunction. J Mol Cell Cardiol 2017; 108:24-33. [PMID: 28476659 DOI: 10.1016/j.yjmcc.2017.04.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 04/24/2017] [Accepted: 04/27/2017] [Indexed: 12/20/2022]
Abstract
Heart failure with preserved ejection fraction (HFpEF) is a complex syndrome, characterized by increased diastolic stiffness and a preserved ejection fraction, with no effective treatment options. Here we studied the therapeutic potential of exercise for improving diastolic function in a mouse model with HFpEF-like symptoms, the TtnΔIAjxn mouse model. TtnΔIAjxn mice have increased diastolic stiffness and reduced exercise tolerance, mimicking aspects of HFpEF observed in patients. We investigated the effect of free-wheel running exercise on diastolic function. Mechanical studies on cardiac muscle strips from the LV free wall revealed that both TtnΔIAjxn and wildtype (WT) exercised mice had a reduction in passive stiffness, relative to sedentary controls. In both genotypes, this reduction is due to an increase in the compliance of titin whereas ECM-based stiffness was unaffected. Phosphorylation of titin's PEVK and N2B spring elements were assayed with phospho-site specific antibodies. Exercised mice had decreased PEVK phosphorylation and increased N2B phosphorylation both of which are predicted to contribute to the increased compliance of titin. Since exercise lowers the heart rate we examined whether reduction in heart rate per se can improve passive stiffness by administering the heart-rate-lowering drug ivabradine. Ivabradine lowered heart rate in our study but it did not affect passive tension, in neither WT nor TtnΔIAjxn mice. We conclude that exercise is beneficial for decreasing passive stiffness and that it involves beneficial alterations in titin phosphorylation.
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Affiliation(s)
- Rebecca E Slater
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, United States; Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ 85721, United States
| | - Joshua G Strom
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, United States; Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ 85721, United States
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, United States; Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ 85721, United States.
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21
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Abstract
Striated cardiac and skeletal muscles play very different roles in the body, but they are similar at the molecular level. In particular, contraction, regardless of the type of muscle, is a precise and complex process involving the integral protein myofilaments and their associated regulatory components. The smallest functional unit of muscle contraction is the sarcomere. Within the sarcomere can be found a sophisticated ensemble of proteins associated with the thick filaments (myosin, myosin binding protein-C, titin, and obscurin) and thin myofilaments (actin, troponin, tropomyosin, nebulin, and nebulette). These parallel thick and thin filaments slide across one another, pulling the two ends of the sarcomere together to regulate contraction. More specifically, the regulation of both timing and force of contraction is accomplished through an intricate network of intra- and interfilament interactions belonging to each myofilament. This review introduces the sarcomere proteins involved in striated muscle contraction and places greater emphasis on the more recently identified and less well-characterized myofilaments: cardiac myosin binding protein-C, titin, nebulin, and obscurin. © 2017 American Physiological Society. Compr Physiol 7:675-692, 2017.
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Affiliation(s)
- Brian Leei Lin
- Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois, USA
| | - Taejeong Song
- Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois, USA.,Department of Internal Medicine, Heart, Lung and Vascular Institute, Division of Cardiovascular Health and Sciences, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Sakthivel Sadayappan
- Department of Cell and Molecular Physiology, Health Sciences Division, Loyola University Chicago, Maywood, Illinois, USA.,Department of Internal Medicine, Heart, Lung and Vascular Institute, Division of Cardiovascular Health and Sciences, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
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22
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Chung CS, Afonso L. Heart Rate Is an Important Consideration for Cardiac Imaging of Diastolic Function. JACC Cardiovasc Imaging 2016; 9:756-8. [PMID: 26897673 DOI: 10.1016/j.jcmg.2015.10.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 10/09/2015] [Indexed: 11/26/2022]
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Chung CS, Shmuylovich L, Kovács SJ. What global diastolic function is, what it is not, and how to measure it. Am J Physiol Heart Circ Physiol 2015; 309:H1392-406. [DOI: 10.1152/ajpheart.00436.2015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 08/17/2015] [Indexed: 12/17/2022]
Abstract
Despite Leonardo da Vinci's observation (circa 1511) that “the atria or filling chambers contract together while the pumping chambers or ventricles are relaxing and vice versa,” the dynamics of four-chamber heart function, and of diastolic function (DF) in particular, are not generally appreciated. We view DF from a global perspective, while characterizing it in terms of causality and clinical relevance. Our models derive from the insight that global DF is ultimately a result of forces generated by elastic recoil, modulated by cross-bridge relaxation, and load. The interaction between recoil and relaxation results in physical wall motion that generates pressure gradients that drive fluid flow, while epicardial wall motion is constrained by the pericardial sac. Traditional DF indexes (τ, E/E′, etc.) are not derived from causal mechanisms and are interpreted as approximating either stiffness or relaxation, but not both, thereby limiting the accuracy of DF quantification. Our derived kinematic models of isovolumic relaxation and suction-initiated filling are extensively validated, quantify the balance between stiffness and relaxation, and provide novel mechanistic physiological insight. For example, causality-based modeling provides load-independent indexes of DF and reveals that both stiffness and relaxation modify traditional DF indexes. The method has revealed that the in vivo left ventricular equilibrium volume occurs at diastasis, predicted novel relationships between filling and wall motion, and quantified causal relationships between ventricular and atrial function. In summary, by using governing physiological principles as a guide, we define what global DF is, what it is not, and how to measure it.
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Affiliation(s)
- Charles S. Chung
- Department of Physiology and Center for Muscle Biology, University of Kentucky, Lexington, Kentucky, and Department of Physiology, Wayne State University, Detroit, Michigan; and
| | - Leonid Shmuylovich
- Cardiovascular Biophysics Laboratory, Cardiovascular Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Sándor J. Kovács
- Cardiovascular Biophysics Laboratory, Cardiovascular Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
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24
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Campbell KS, Sorrell VL. Cell- and molecular-level mechanisms contributing to diastolic dysfunction in HFpEF. J Appl Physiol (1985) 2015; 119:1228-32. [PMID: 25911687 DOI: 10.1152/japplphysiol.01168.2014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Accepted: 04/12/2015] [Indexed: 02/08/2023] Open
Abstract
Heart failure with preserved ejection fraction (HFpEF) is the default diagnosis for patients who have symptoms of heart failure, an ejection fraction >0.5, and evidence of diastolic dysfunction. The clinical condition, which was largely unrecognized 30 years ago, is now a major health problem and currently accounts for 50% of all patients with heart failure. Clinical studies show that patients with HFpEF exhibit increased passive stiffness of the ventricles and a slower rate of pressure decline during diastole. This review discusses some of the cell- and molecular-level mechanisms that contribute to these effects and focuses on data obtained using human samples. Collagen cross linking, modulation of protein kinase G-related pathways, Ca(2+) handling, and strain-dependent detachment of cross bridges are highlighted as potential factors that could be modulated to improve ventricular function in patients with HFpEF.
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Affiliation(s)
- Kenneth S Campbell
- Department of Physiology and Center for Muscle Biology, Linda and Jack Gill Heart Institute, University of Kentucky, Lexington, Kentucky; and
| | - Vincent L Sorrell
- Division of Cardiovascular Medicine, Linda and Jack Gill Heart Institute, University of Kentucky, Lexington, Kentucky
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25
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Deleting titin's I-band/A-band junction reveals critical roles for titin in biomechanical sensing and cardiac function. Proc Natl Acad Sci U S A 2014; 111:14589-94. [PMID: 25246556 DOI: 10.1073/pnas.1411493111] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Titin, the largest protein known, forms a giant filament in muscle where it spans the half sarcomere from Z disk to M band. Here we genetically targeted a stretch of 14 immunoglobulin-like and fibronectin type 3 domains that comprises the I-band/A-band (IA) junction and obtained a viable mouse model. Super-resolution optical microscopy (structured illumination microscopy, SIM) and electron microscopy were used to study the thick filament length and titin's molecular elasticity. SIM showed that the IA junction functionally belongs to the relatively stiff A-band region of titin. The stiffness of A-band titin was found to be high, relative to that of I-band titin (∼ 40-fold higher) but low, relative to that of the myosin-based thick filament (∼ 70-fold lower). Sarcomere stretch therefore results in movement of A-band titin with respect to the thick filament backbone, and this might constitute a novel length-sensing mechanism. Findings disproved that titin at the IA junction is crucial for thick filament length control, settling a long-standing hypothesis. SIM also showed that deleting the IA junction moves the attachment point of titin's spring region away from the Z disk, increasing the strain on titin's molecular spring elements. Functional studies from the cellular to ex vivo and in vivo left ventricular chamber levels showed that this causes diastolic dysfunction and other symptoms of heart failure with preserved ejection fraction (HFpEF). Thus, our work supports titin's important roles in diastolic function and disease of the heart.
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26
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Abstract
The giant protein titin forms a unique filament network in cardiomyocytes, which engages in both mechanical and signaling functions of the heart. TTN, which encodes titin, is also a major human disease gene. In this review, we cover the roles of cardiac titin in normal and failing hearts, with a special emphasis on the contribution of titin to diastolic stiffness. We provide an update on disease-associated titin mutations in cardiac and skeletal muscles and summarize what is known about the impact of protein-protein interactions on titin properties and functions. We discuss the importance of titin-isoform shifts and titin phosphorylation, as well as titin modifications related to oxidative stress, in adjusting the diastolic stiffness of the healthy and the failing heart. Along the way we distinguish among titin alterations in systolic and in diastolic heart failure and ponder the evidence for titin stiffness as a potential target for pharmacological intervention in heart disease.
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Affiliation(s)
- Wolfgang A Linke
- From the Department of Cardiovascular Physiology, Ruhr University Bochum, Bochum, Germany
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27
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Chung CS, Mitov MI, Callahan LA, Campbell KS. Increased myocardial short-range forces in a rodent model of diabetes reflect elevated content of β myosin heavy chain. Arch Biochem Biophys 2013; 552-553:92-9. [PMID: 24012810 DOI: 10.1016/j.abb.2013.08.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Revised: 08/02/2013] [Accepted: 08/24/2013] [Indexed: 01/13/2023]
Abstract
Diastolic dysfunction is a clinically significant problem for patients with diabetes and often reflects increased ventricular stiffness. Attached cross-bridges contribute to myocardial stiffness and produce short-range forces, but it is not yet known whether these forces are altered in diabetes. In this study, we tested the hypothesis that cross-bridge-based short-range forces are increased in the streptozotocin (STZ) induced rat model of type 1 diabetes. Chemically permeabilized myocardial preparations were obtained from 12week old rats that had been injected with STZ or vehicle 4weeks earlier, and activated in solutions with pCa (=-log10[Ca(2+)]) values ranging from 9.0 to 4.5. The short-range forces elicited by controlled length changes were ∼67% greater in the samples from the diabetic rats than in the control preparations. This change was mostly due to an increased elastic limit (the length change at the peak short-range force) as opposed to increased passive muscle stiffness. The STZ-induced increase in short-ranges forces is thus unlikely to reflect changes to titin and/or collagen filaments. Gel electrophoresis showed that STZ increased the relative expression of β myosin heavy chain. This molecular mechanism can explain the increased short-ranges forces observed in the diabetic tissue if β myosin molecules remain bound between the filaments for longer durations than α molecules during imposed movements. These results suggest that interventions that decrease myosin attachment times may be useful treatments for diastolic dysfunction associated with diabetes.
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Affiliation(s)
- Charles S Chung
- Department of Physiology, Critical Care and Sleep Medicine, University of Kentucky, Lexington, KY 40536-0298, United States; Center for Muscle Biology, Critical Care and Sleep Medicine, University of Kentucky, Lexington, KY 40536-0298, United States
| | - Mihail I Mitov
- Department of Physiology, Critical Care and Sleep Medicine, University of Kentucky, Lexington, KY 40536-0298, United States; Center for Muscle Biology, Critical Care and Sleep Medicine, University of Kentucky, Lexington, KY 40536-0298, United States
| | - Leigh Ann Callahan
- Center for Muscle Biology, Critical Care and Sleep Medicine, University of Kentucky, Lexington, KY 40536-0298, United States; Division of Pulmonary, Critical Care and Sleep Medicine, University of Kentucky, Lexington, KY 40536-0298, United States
| | - Kenneth S Campbell
- Department of Physiology, Critical Care and Sleep Medicine, University of Kentucky, Lexington, KY 40536-0298, United States; Center for Muscle Biology, Critical Care and Sleep Medicine, University of Kentucky, Lexington, KY 40536-0298, United States.
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28
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Vikhlyantsev IM, Podlubnaya ZA. New titin (connectin) isoforms and their functional role in striated muscles of mammals: facts and suppositions. BIOCHEMISTRY (MOSCOW) 2013; 77:1515-35. [PMID: 23379526 DOI: 10.1134/s0006297912130093] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
This review summarizes results of our studies on titin isoform composition in vertebrate striated muscles under normal conditions, during hibernation, real and simulated microgravity, and under pathological conditions (stiff-person syndrome, post-apoplectic spasticity, dilated cardiomyopathy, cardiac hypertrophy). Experimental evidence for the existence in mammalian striated muscles of higher molecular weight isoforms of titin (NT-isoforms) in addition to the known N2A-, N2BA-, and N2B-titin isoforms was obtained. Comparative studies of changes in titin isoform composition and structure-functional properties of human and animal striated muscles during adaptive and pathological processes led to a conclusion about the key role of NT-isoforms of titin in maintenance of sarcomere structure and contractile function of these muscles.
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Affiliation(s)
- I M Vikhlyantsev
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
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29
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Titin-based tension in the cardiac sarcomere: molecular origin and physiological adaptations. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2012; 110:204-17. [PMID: 22910434 DOI: 10.1016/j.pbiomolbio.2012.08.003] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Accepted: 08/03/2012] [Indexed: 01/08/2023]
Abstract
The passive stiffness of cardiac muscle plays a critical role in ventricular filling during diastole and is determined by the extracellular matrix and the sarcomeric protein titin. Titin spans from the Z-disk to the M-band of the sarcomere and also contains a large extensible region that acts as a molecular spring and develops passive force during sarcomere stretch. This extensible segment is titin's I-band region, and its force-generating mechanical properties determine titin-based passive tension. The properties of titin's I-band region can be modulated by isoform splicing and post-translational modification and are intimately linked to diastolic function. This review discusses the physical origin of titin-based passive tension, the mechanisms that alter titin stiffness, and titin's role in stress-sensing signaling pathways.
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30
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Ghosh E, Kovács SJ. Spatio-temporal attributes of left ventricular pressure decay rate during isovolumic relaxation. Am J Physiol Heart Circ Physiol 2012; 302:H1094-101. [DOI: 10.1152/ajpheart.00990.2011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Global left ventricular (LV) isovolumic relaxation rate has been characterized: 1) via the time constant of isovolumic relaxation τ or 2) via the logistic time constant τ L. An alternate kinematic method, characterizes isovolumic relaxation (IVR) in accordance with Newton's Second Law. The model's parameters, stiffness Ek, and damping/relaxation μ result from best fit of model-predicted pressure to in vivo data. All three models (exponential, logistic, and kinematic) characterize global relaxation in terms of pressure decay rates. However, IVR is inhomogeneous and anisotropic. Apical and basal LV wall segments untwist at different times and rates, and transmural strain and strain rates differ due to the helically variable pitch of myocytes and sheets. Accordingly, we hypothesized that the exponential model (τ) or kinematic model (μ and Ek) parameters will elucidate the spatiotemporal variation of IVR rate. Left ventricular pressures in 20 subjects were recorded using a high-fidelity, multipressure transducer (3 cm apart) catheter. Simultaneous, dual-channel pressure data was plotted in the pressure phase-plane (dP/d t vs. P) and τ, μ, and Ek were computed in 1631 beats (average: 82 beats per subject). Tau differed significantly between the two channels ( P < 0.05) in 16 of 20 subjects, whereas μ and Ek differed significantly ( P < 0.05) in all 20 subjects. These results show that quantifying the relaxation rate from data recorded at a single location has limitations. Moreover, kinematic model based analysis allows characterization of restoring (recoil) forces and resistive (crossbridge uncoupling) forces during IVR and their spatio-temporal dependence, thereby elucidating the relative roles of stiffness vs. relaxation as IVR rate determinants.
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Affiliation(s)
- Erina Ghosh
- Department of Biomedical Engineering, School of Engineering and Applied Science, Washington University, St. Louis, Missouri
| | - Sándor J. Kovács
- Cardiovascular Biophysics Laboratory, Cardiovascular Division, Department of Internal Medicine, School of Medicine; and
- Department of Biomedical Engineering, School of Engineering and Applied Science, Washington University, St. Louis, Missouri
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31
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Titin-actin interaction: PEVK-actin-based viscosity in a large animal. J Biomed Biotechnol 2011; 2011:310791. [PMID: 22162634 PMCID: PMC3227466 DOI: 10.1155/2011/310791] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2011] [Accepted: 09/01/2011] [Indexed: 12/16/2022] Open
Abstract
Titin exhibits an interaction between its PEVK segment and the actin filament resulting in viscosity, a speed dependent resistive force, which significantly influences diastolic filling in mice. While diastolic disease is clinically pervasive, humans express a more compliant titin (N2BA:N2B ratio ~0.5–1.0) than mice (N2BA:N2B ratio ~0.2). To examine PEVK-actin based viscosity in compliant titin-tissues, we used pig cardiac tissue that expresses titin isoforms similar to that in humans. Stretch-hold experiments were performed at speeds from 0.1 to 10 lengths/s from slack sarcomere lengths (SL) to SL of 2.15 μm. Viscosity was calculated from the slope of stress-relaxation vs stretch speed. Recombinant PEVK was added to compete off native interactions and this found to reduce the slope by 35%, suggesting that PEVK-actin interactions are a strong contributor of viscosity. Frequency sweeps were performed at frequencies of 0.1–400 Hz and recombinant protein reduced viscous moduli by 40% at 2.15 μm and by 50% at 2.25 μm, suggesting a SL-dependent nature of viscosity that might prevent SL “overshoot” at long diastolic SLs. This study is the first to show that viscosity is present at physiologic speeds in the pig and supports the physiologic relevance of PEVK-actin interactions in humans in both health and disease.
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