Skeletal muscle-derived extracellular vesicles during eccentric and concentric exercise promote muscle regeneration after injury

Methods

A murine model of barium chloride-induced muscle injury was used to compare the effects of EE and CE on muscle regeneration. mEVs were isolated from sedentary (SED), CE-, and EE-conditioned muscle and characterized by nanoparticle tracking analysis, transmission electron microscopy, and western blotting. Metabolic profiling of mEVs was performed using LC–MS. The functional roles were assessed through intramuscular injection of mEVs and GW4869-mediated inhibition of mEVs secretion.

The effects of mEVs on myogenesis were further examined in C2C12 myoblasts. Results: EE significantly enhanced muscle regeneration compared to CE, as evidenced by improved histology, reduced fibrosis, and increased expression of myogenic markers such as Myod , Myog , and eMyhc . EE also induced greater release of mEVs than CE, as indicated by higher expression of mEVs markers and Rab27a/b.

Inhibition of mEVs secretion with GW4869 abolished the regenerative benefits of exercise. Exogenous administration of EE-mEVs enhanced muscle repair and C2C12 differentiation more effectively than CE-mEVs or SED-mEVs. Metabolomic analysis revealed significant enrichment of lipid metabolites in EE-mEVs, which was consistent with the upregulation of lipid metabolism-related genes.

RNA-seq analyses further indicated that lipid metabolites enriched in mEVs promoted muscle repair by upregulating energy-sensing genes associated with fatty acid metabolism in myoblasts. Conclusions: EE facilitates muscle repair more effectively than CE by promoting the release of mEVs enriched in pro-regenerative lipid metabolites. These findings suggest EE-mEVs as a promising biological therapeutic strategy for muscle injury, particularly in cases where exercise is not feasible.