Skeletal Muscle sEVs Mediate Exercise-Induced Cardioprotection in I/R Injury

BACKGROUND: Exercise training has been demonstrated to provide direct endogenous cardioprotection and to reduce cardiovascular disease risk. Skeletal muscle functions not only as an organ for movement but also as a vital secretory organ. However, how muscle-heart crosstalk contributes to exercise-induced cardioprotection remains largely unclear. Here, we investigated the cardioprotective effects of exercise-induced small extracellular vesicles (sEVs) derived from skeletal muscle in myocardial ischemia/reperfusion (MI/R) injury in mice. METHODS: An adeno-associated virus 8-dMCK (double-muscle creatine kinase)-CD63-EGFP (enhanced green fluorescent protein) reporter system was used to track skeletal muscle-derived sEVs in the heart of mice after 4 weeks of exercise. To determine whether sEVs from exercised skeletal muscle mediate cardioprotection, cardiac sEV abundance was increased by intramyocardial injection and decreased by generating skeletal muscle-specific Rab27a knockout mice. The molecular mechanism was elucidated by profiling sEV-enriched microRNAs and validating their functions in cardiomyocytes and mouse MI/R injury models. The translational potential was then assessed in human exercise cohorts. Finally, the therapeutic efficacy was evaluated using miRNA agomirs and adeno-associated virus 8-mediated, skeletal muscle-specific overexpression of miRNAs in MI/R injury models. RESULTS: Exercise promoted the entry of skeletal muscle-derived sEVs into the heart. Skeletal muscle-derived sEVs from exercised mice significantly attenuated MI/R injury by reducing cardiomyocyte apoptosis and improving mitochondrial respiration. Exercise-mediated protection against MI/R injury was attenuated after inhibiting the secretion of sEVs from skeletal muscle. Mechanistically, exercise-enriched sEVs delivered miR-451a and miR-143-3p to cardiomyocytes, thereby modulating the PERK (protein kinase R-like endoplasmic reticulum kinase)-ATF4-CHOP stress-response pathway and the USP46/P53 axis, thus reducing cardiomyocyte death. Skeletal muscle-specific overexpression of miR-451a/143-3p recapitulated the cardioprotective effects of exercise in vivo. Furthermore, exercising humans also showed elevated levels of miR-451a/143-3p in their skeletal muscle and circulating sEVs. CONCLUSIONS: Our study reveals a novel exercise-induced cardioprotective mechanism via muscle-heart crosstalk, highlighting a promising therapeutic approach for treating cardiovascular disease.