MSCs-derived Apoptotic Extracellular Vesicles Promote Muscle Regeneration by Inducing Pannexin 1 Channel-Dependent Creatine Release by Myoblasts

Severe muscle injury is hard to heal and always results in a poor prognosis. Recent studies found that extracellular vesicle-based therapy has promising prospects for regeneration medicine, however, whether extracellular vesicles have therapeutic effects on severe muscle injury is still unknown. Herein, we extracted apoptotic extracellular vesicles derived from mesenchymal stem cells（MSCs-Apo EVs） to treat cardiotoxin induced tibialis anterior（TA） injury and found that MSCs-Apo EVs promoted muscles regeneration and increased the proportion of multinucleated cells. Besides that, we also found that apoptosis was synchronized during myoblasts fusion and MSCs-Apo EVs promoted the apoptosis ratio as well as the fusion index of myoblasts. Furthermore, we revealed that MSCs-Apo EVs increased the relative level of creatine during myoblasts fusion, which was released via activated Pannexin 1 channel. Moreover, we also found that activated Pannexin 1 channel was highly expressed on the membrane of myoblasts-derived Apo EVs（Myo-Apo EVs） instead of apoptotic myoblasts, and creatine was the pivotal metabolite involved in myoblasts fusion. Collectively, our findings firstly revealed that MSCs-Apo EVs can promote muscle regeneration and elucidated that the new function of Apo EVs as passing inter-cell messages through releasing metabolites from activated Pannexin 1 channel, which will provide new evidence for extracellular vesicles-based therapy as well as improving the understanding of new functions of extracellular vesicles.