Skeletal Muscle-Derived Extracellular Vesicles During Eccentric and Concentric Exercise Promote Muscle Regeneration...

Skeletal muscle injuries significantly impair mobility and function, yet effective therapeutic interventions remain limited. Both eccentric exercise (EE) and concentric exercise (CE) promote muscle repair, but the underlying mechanisms are not fully understood. Muscle-derived extracellular vesicles (mEVs) have emerged as critical mediators of intercellular communication; however, their role in exercise-induced regeneration remains unclear.

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 characterised 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 mEV secretion. The effects of mEVs on myogenesis were further examined in C2C12 myoblasts.

EE significantly enhanced muscle regeneration compared with CE, as evidenced by improved histology, reduced fibrosis (F (2,15) = 59.37, p < 0.0001) and increased expression of myogenic markers such as Myod (p < 0.001), Myog (p < 0.001) and eMyhc (p < 0.001). EE also induced greater release of mEVs than CE, as indicated by higher expression of mEV markers and Rab27a/b (Rab27a, p < 0.001; Rab27b, p = 0.1222). Inhibition of mEV secretion with GW4869 abolished the regenerative benefits of exercise. Exogenous administration of EE-mEVs enhanced muscle repair and C2C12 differentiation (Myod, F (2, 6) = 33.09, p < 0.001; Myog, F (2, 6) = 66.41, p < 0.001) more effectively than CE-mEVs or SED-mEVs. Metabolomic analysis revealed significant enrichment of lipid metabolites in EE-mEVs (N = 5, p < 0.05), which was consistent with the upregulation of lipid metabolism-related genes. RNA-seq analyses further indicated that lipid metabolites enriched in mEVs contributed to muscle repair potentially through activation of energy-sensing pathways such as AMPK.

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.