Book of Abstracts - New Frontiers 2022

Abstracts of oral presentations

PATIENT-SPECIFIC DERIVED CARDIOMYOCYTES: WILL WE BE ABLE TO PREDICT THE CARDIOMYOPATHIES IN THE DISH TOMORROW? M. Souidi 1 , J. Resta 2 , Y. Sleiman 1 , S. Reiken 3 , P. Amedro 1 , P. Meyer 1 , A. Charrabi 1 , O. Cazorla 1 , M. Vincenti 1 , S. Blot 4 , F. Rivier 1 , A. Parini 2 , A. Marks 3 , J. Mialet-Perez 2 , A. Lacampagne 1 , A. Meli 1 1 PhyMedExp, Montpellier, France; 2 Institute of Metabolic and Cardiovascular Diseases, Toulouse, France; 3 Department of Physiology and Cellular Biophysics, Clyde and Helen Wu Center for Molecular Cardiology, Columbia University Vagelos College of Physicians and Surgeons, New York, USA; 4 IMRB - Biology of the neuromuscular system, INSERM, UPEC, EFS, EnvA, Maisons-Alfort, France Aims: Duchenne Muscular Dystrophy (DMD) is an X-linked disorder characterized by progressive muscle weakness due to absence of functional dystrophin. DMD patients developed dilated cardiomyopathy (DCM). In the past, we have demonstrated that aberrant sarcoplasmic reticulum (SR) calcium (Ca 2+ ) handling is an early pathophysiological feature in DMD mouse (mdx), DMD canine (GRMD) as well as in human CMs. We have also evidenced that abnormal intracellular Ca 2+ cycling is related to early-stage pathological remodeling of the ryanodine receptor channel (RyR2) leading to age-dependent DCM. Methods and Results: Here, we used hiPSC-CMs from DMD patients selected by Speckle-tracking echocardiography and canine DMD cardiac biopsies to assess key early-stage DMD-associated DCM features including the cellular defects associated with SR Ca 2+ leak. Independently of the clinical observations from the 3 DMD patients, our data reveal that dystrophin-deficiency quickly induces RyR2 remodeling and Ca 2+ leak. When evaluating the SR Ca 2+ handling, we revealed that all DMD hiPSC-CMs exhibited aberrant Ca 2+ transients, diastolic leak and elevated diastolic Ca 2+ level. By evaluating the contractile properties, we found that RyR2 leak causes hypocontractility in DMD hiPSC-CMs. This force defect was associated with hiPSC-CM hypertrophy, sarcomere disorganization and fibrosis. Furthermore, we demonstrated for the first time that DMD hiPSC-CMs and GRMD cardiac biopsies exhibit a profile of premature senescence, with higher gene and protein expression of the senescence markers SA- β -gal, p15/p16, nuclear enlargement and cell hypertrophy. Preventing RyR2 dysfunction, by stabilizing its closed state conformation, improves the intracellular Ca 2+ dynamics and restores normal contractility and prevents fibrosis development and senescence. Conclusions: We revealed that cellular damages are established earlier than cardiac clinical pathology in DMD patients, with major perturbation of the cardiac ECC. We revealed RyR2 as an early biomarker of DMD-associated cardiac damages. The progressive and later DCM onset could be linked with the increased fibrosis and premature senescence, eventually causing cell death and further cardiac fibrosis in a vicious cycle leading to further hypocontractility as a major feature of DCM. Finally, our work reinforces the interest of using hiPSC-CMs as an optimal tool to dissect molecular mechanisms of the early stage of dystrophin deficiency leading to the development of DMD-associated-DCM.

Keywords: DMD, hiPSC-derived cardiomyocytes, ryanodine receptor, calcium, senescence

Funding:AFM

55