Differential expression of mi RNAs occurs in injured proximal nerve stumps and includes mi RNAs that are firstly down-regulated and then gradually up-regulated following nerve injury.These mi RNAs might be related to a Schwann cell phenotypic switch.mi R-30 c,as a member of this group,was further investigated in the current study.Sprague-Dawley rats underwent sciatic nerve transection and proximal nerve stumps were collected at 1,4,7,14,21,and 28 days post injury for analysis.Following sciatic nerve injury,mi R-30 c was down-regulated,reaching a minimum on day 4,and was then upregulated to normal levels.Schwann cells were isolated from neonatal rat sciatic nerve stumps,then transfected with mi R-30 c agomir and co-cultured in vitro with dorsal root ganglia.The enhanced expression of mi R-30 c robustly increased the amount of myelin-associated protein in the co-cultured dorsal root ganglia and Schwann cells.We then modeled sciatic nerve crush injury in vivo in Sprague-Dawley rats and tested the effect of perineural injection of mi R-30 c agomir on myelin sheath regeneration.Fourteen days after surgery,sciatic nerve stumps were harvested and subjected to immunohistochemistry,western blot analysis,and transmission electron microscopy.The direct injection of mi R-30 c stimulated the formation of myelin sheath,thus contributing to peripheral nerve regeneration.Overall,our findings indicate that mi R-30 c can promote Schwann cell myelination following peripheral nerve injury.The functional study of mi R-30 c will benefit the discovery of new therapeutic targets and the development of new treatment strategies for peripheral nerve regeneration. Differential expression of mi RNAs occurs in injured proximal nerve stumps and includes miRNAs that are first down-regulated and then gradually up-regulated following nerve injury. These miRNAs might be related to a Schwann cell phenotypic switch. MiR-30c, as a member of this group, was further investigated in the current study. Sprague-Dawley rats underwent sciatic nerve transection and proximal nerve stumps were collected at 1, 4, 7, 14, 21, and 28 days post injury for analysis. Following sciatic nerve injury, mi R-30 c was down-regulated, reaching a minimum on day 4, and was then upregulated to normal levels. Schwann cells were isolated from neonatal rat sciatic nerve stumps, then transfected with mi R-30 c agomir and co -cultured in vitro with dorsal root ganglia. The enhanced expression of mi R-30 c robustly increased the amount of myelin-associated protein in the co-cultured dorsal root ganglia and Schwann cells. We then modeled sciatic nerve crush injury in vivo in Sprague -Dawley rats and te sted the effect of perineural injection of mi R-30 c agomir on myelin sheath regeneration. Fourteen days after surgery, sciatic nerve stumps were harvested and subjected to immunohistochemistry, western blot analysis, and transmission electron microscopy. direct injection of mi R-30 c stimulated the formation of myelin sheath, thus contributing to peripheral nerve regeneration. Overall, our findings indicate that mi R-30 c can promote Schwann cell myelination following peripheral nerve injury. The functional study of mi R-30 c will benefit the discovery of new therapeutic targets and the development of new treatment strategies for peripheral nerve regeneration.