Scientific Results

Pathogenesis of Hypertrophic Cardiomyopathy is Mutation Rather Than Disease Specific: A Comparison of the Cardiac Troponin T E163R and R92Q Mouse Models

Year: 2017

Authors: Ferrantini C., Coppini R., Pioner J.M., Gentile F., Tosi B., Mazzoni L., Scellini B., Piroddi N., Laurino A., Santini L., Spinelli V., Sacconi L., De Tombe P., Moore R., Tardiff J., Mugelli A., Olivotto I., Cerbai E., Tesi C., Poggesi C.

Autors Affiliation: Department of Experimental and Clinical Medicine, University of Florence, Italy;
Department of NeuroFarBa, University of Florence, Italy;
Department of Experimental and Clinical Medicine, University of Florence, Italy;
LENS, University of Florence & National Institute of Optics (INO-CNR), Florence, Italy;
Loyola University Medical Center Department of Physiology, Chicago, IL;
University of Arizona at Tucson, AZ;
Careggi University Hospital, Florence, Italy.

Abstract: BACKGROUND:
In cardiomyocytes from patients with hypertrophic cardiomyopathy, mechanical dysfunction and arrhythmogenicity are caused by mutation-driven changes in myofilament function combined with excitation-contraction (E-C) coupling abnormalities related to adverse remodeling. Whether myofilament or E-C coupling alterations are more relevant in disease development is unknown. Here, we aim to investigate whether the relative roles of myofilament dysfunction and E-C coupling remodeling in determining the hypertrophic cardiomyopathy phenotype are mutation specific.
METHODS AND RESULTS:
Two hypertrophic cardiomyopathy mouse models carrying the R92Q and the E163R TNNT2 mutations were investigated. Echocardiography showed left ventricular hypertrophy, enhanced contractility, and diastolic dysfunction in both models; however, these phenotypes were more pronounced in the R92Q mice. Both E163R and R92Q trabeculae showed prolonged twitch relaxation and increased occurrence of premature beats. In E163R ventricular myofibrils or skinned trabeculae, relaxation following Ca2+ removal was prolonged; resting tension and resting ATPase were higher; and isometric ATPase at maximal Ca2+ activation, the energy cost of tension generation, and myofilament Ca2+ sensitivity were increased compared with that in wild-type mice. No sarcomeric changes were observed in R92Q versus wild-type mice, except for a large increase in myofilament Ca2+ sensitivity. In R92Q myocardium, we found a blunted response to inotropic interventions, slower decay of Ca2+ transients, reduced SERCA function, and increased Ca2+/calmodulin kinase II activity. Contrarily, secondary alterations of E-C coupling and signaling were minimal in E163R myocardium.
CONCLUSIONS:
In E163R models, mutation-driven myofilament abnormalities directly cause myocardial dysfunction. In R92Q, diastolic dysfunction and arrhythmogenicity are mediated by profound cardiomyocyte signaling and E-C coupling changes. Similar hypertrophic cardiomyopathy phenotypes can be generated through different pathways, implying different strategies for a precision medicine approach to treatment.

Journal/Review: JOURNAL OF THE AMERICAN HEART ASSOCIATION

Volume: 6 (7)      Pages from: e005407-1  to: e005407-19

More Information: This work was supported by Telethon Italy (GGP13162 and GGP16191), the European Commission (STREP Project 241577 \”BIG HEART,\” 7th European Framework Program), the Italian Ministry of Health (GR-2011-02350583, RF-2013-02356787 and NET-2011-02347173), Regione Toscana (FAS-Salute 2014, ToRSADE project), and the National Institues of Health (projects HL075619 and HL62426).
KeyWords: excitation-contraction coupling; hypertrophic cardiomyopathy; pathophysiology; sarcomere physiology; troponin T
DOI: 10.1161/JAHA.116.005407

Citations: 10
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English