Résumé :
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Cardiac cell replacement has emerged as a potent new therapy by regenerating irreversibly damaged heart areas in the setting of heart failure. Cell therapy approaches have been extensively developed in the indication of ischemic infarction, but have not been thoroughly investigated yet for dilated cardiomyopathy (DCM). Among candidate cell types, Embryonic Stem cells (ES) demonstrate a high and efficient cardiomyogenic commitment in vitro, especially upon stimulation by Bone Morphogenic Factor 2 (BMP2) prior to administration, and an efficient integration in vivo following implantation in several experimental models. In order to demonstrate the concept that cardiac progenitor cells could improve heart function in a DCM mouse model, we assessed the efficacy of murine ES (mES) implantation in vivo. Cellular implantation and integration were analysed by immunohistochemistry. Functional efficacy was assessed by echocardiography. The genetically engineered mouse model LmnaH222P/H222P harbours mutation in the laminA/C gene. Adult homozygous mutant mice develop muscular dystrophy and dilated cardiomyopathy similar to the clinical features of human laminopathies. Concerning the cardiac phenotype, they develop chamber dilation and hypokinesia with conduction defects. 3.105 mES cells, expressing the enhanced yellow fluorescent protein (EYFP) under control of the cardiac-specific a-actin promoter, were stimulated for 24 hours with BMP-2, and transplanted sub-epicardially into dilated mouse myocardium. The immunosuppression of mice was required to avoid rejection of transplanted cells. Cell fate, localization and integration were assessed by immunohistochemistry based on detection of EYFP and identification of cardiac-specific antigens. Echocardiography was performed one and two months post engraftment using a VIVID7 apparatus.Transplantation of stimulated mES cells into LmnaH222P/H222P mouse hearts tended to stabilize cardiac function, as determined by echocardiography. Engrafted cardiac-committed mES cells were observed at several time points after injection and expressed specific markers, as demonstrated by EYFP detection and immunostaining of gap junction proteins. These results indicate that cardiac-committed mES are attracting candidates for generating cardiac progenitor cells, able to integrate as cardiomyocytes and to palliate the cardiomyopathy in DCM mouse model.
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