Extracellular vesicles from skin-derived precursor Schwann cells improve the microenvironment for peripheral nerve...

Effective repair of peripheral nerve injuries often requires nerve grafts, yet outcomes remain suboptimal due to limited intrinsic regenerative support. Developing bioactive grafts to actively orchestrate the regenerative microenvironment is a critical unmet need. Our previous studies have demonstrated that extracellular vesicles from skin-derived precursor Schwann cells remarkedly enhance peripheral nerve regeneration. The purpose of this study was to investigate the molecular mechanisms by which extracellular vesicles from skin-derived precursor Schwann cells influence peripheral nerve regeneration. We established rat models of sciatic nerve defects and designated three intervention groups: autograft, nerve grafts incorporating extracellular vesicles from skin-derived precursor Schwann cells, and a control group with nerve grafts (silicone conduits filled with vehicle). Nerve injury was induced and surgical implantation of the respective grafts to bridge the defect was performed. Transcriptomic profiles (RNA-sequencing) and bioinformatic analyses were performed at 11 time points spanning the 12-week period post-injury. Weighted gene co-expression network analysis revealed that critical regenerative processes, including axon regeneration, myelination, angiogenesis, inflammatory chemotaxis, cell death, and proliferation/migration, occurred in distinct temporal phases. Notably, the nerve grafts incorporating extracellular vesicles from skin-derived precursor Schwann cells demonstrated more robust and temporally coordinated activation of these processes compared with the control groups. Importantly, we found that the nerve grafts incorporating extracellular vesicles from skin-derived precursor Schwann cells downregulated Epha4, which encodes Ephrin receptor A4, a transmembrane receptor known to inhibit Schwann cell migration and myelination. We further identified that vesicle-enriched miR-20b-5p directly targets Epha4. Functional assays confirmed that miR-20b-5p overexpression promoted Schwann cell migration and myelination, whereas its inhibition within nerve grafts incorporating extracellular vesicles from skin-derived precursor Schwann cells attenuated their pro-regenerative effects. This study provides a comprehensive temporal transcriptomic atlas of nerve regeneration and demonstrates that nerve grafts incorporating extracellular vesicles from skin-derived precursor Schwann cells modulate the regenerative microenvironment after peripheral nerve injury via the miR-20b-5p/Epha4 axis. These results offer critical mechanistic insights regarding nerve regeneration and novel therapeutic perspectives for extracellular vesicle-based neural repair strategies.