Conditioned medium of human mesenchymal stromal/stem cells cultured on decellularized extracellular matrix promotes murine skeletal muscle repair after acute injury.

Mesenchymal stromal/stem cells (MSCs) and their secretome are known to exert beneficial effects in many pathological states. However, MSCs therapeutic properties can be reduced due to unsuitable in vitro maintenance conditions. Standard culture protocols neglect the fact that MSCs exist in vivo in the closest connection with the extracellular matrix (ECM), the complex protein network providing an instructive microenvironment. We found recently that conditioned medium from human endometrial MSCs cultured on cell-derived decellularized extracellular matrix (CM-dECM) is dramatically enriched in a number of paracrine factors such as GM-CSF, FGF-2, HGF, MMP-1, MCP-1, IL-6, IL-8, CXCL-1, -2, -5, -6 (Ushakov et al., 2024). Given that several upregulated molecules belong to myokines that are known to participate in skeletal muscle regeneration, we hypothesized that CM-dECM may promote restoration of damaged muscle tissue. Here, we found that CM-dECM injections into barium chloride-injured murine m. tibialis anterior caused myofiber hypertrophy and promoted angiogenesis. Besides, CM-dECM significantly contributed to progression of murine C2C12 myoblasts cell cycle suggesting that muscle repair in vivo may be connected with stimulation of resident myoblasts proliferation. In this study, a role for secretome of endometrial MSCs cultured on dECM in injured murine skeletal muscle regeneration was outlined first. Our findings demonstrate that culture on dECM may be considered as a novel preconditioning approach enhancing MSCs therapeutic potential.