Gingiva-Derived Mesenchymal Stem Cell-Extracellular Vesicles Activate Schwann Cell Repair Phenotype and Promote Nerve Regeneration

A fully functional recovery of peripheral nerve injury remains a major challenge and an unmet clinical need. Recent evidence has reported promising therapeutic effects of mesenchymal stem cell (MSC)-derived extracellular vesicles (EVs) in experimental models of tissue injuries and inflammatory diseases, but less is known about their effects on peripheral nerve regeneration. In this study, we investigated the effects of gingiva-derived mesenchymal stem cell (GMSC)-derived EVs on peripheral nerve regeneration of crush-injured mice sciatic nerves. In vivo studies mimicking clinical nerve repair showed that locally wrapping Gelfoam embedded with GMSC-derived EVs at the crush injury site promoted functional recovery and axonal regeneration, which were comparable with effects conferred by direct transplantation of GMSCs. Mechanistically, we showed that GMSC-derived EVs promoted proliferation and migration of Schwann cells, upregulated the protein expressions of c-JUN, Notch1, GFAP (glial fibrillary acidic protein), and SRY (sex determining region Y)-box 2 (SOX2), characteristic genes of dedifferentiation or repair phenotype of Schwann cells, through which pharmacologically blocking c-JUN/JNK (c-JUN N-terminal kinase) activity significantly abrogated GMSC-derived EV-induced upregulation of these Schwann cell dedifferentiation/repair phenotype-related genes. These findings suggest that GMSC-derived EVs promote peripheral nerve regeneration possibly by activating c-JUN-governed repair phenotype of Schwann cells. Impact Statement Peripheral nerve injuries (PNIs) are common and debilitating, usually resulting in considerable long-term disability and remaining an unmet clinical need. Even though the combination of mesenchymal stem cells (MSCs) and the state-of-the-art tissue engineering technologies has shown promising therapeutic potentials for PNI, there is still not a single licensed stem cell-based product for peripheral nerve repair/regeneration. Emerging evidence indicates that MSC-derived extracellular vesicles (EVs) are comparably effective as MSCs in the therapy of a variety of disease models or pathological conditions. This report shows that local delivery of gingiva-derived mesenchymal stem cell (GMSC)-derived EVs could obviously promote axonal regeneration and functional recovery of injured mice sciatic nerves. Importantly, the findings suggest that GMSC-derived EVs promoted the expression of Schwann cell dedifferentiation/repair phenotype-related genes in vitro, particularly c-JUN, a key transcription factor that drives the activation of repair phenotype of Schwann cells during PNI and regeneration.