MicroRNA-301a knockout attenuates peripheral nerve regeneration by delaying Wallerian degeneration

Our recent study demonstrated that knockout of microRNA-301a attenuates migration and phagocytosis in macrophages. Considering that macrophages and Schwann cells synergistically clear the debris of degraded axons and myelin during Wallerian degeneration, which is a prerequisite for nerve regeneration, we hypothesized that microRNA-301a regulates Wallerian degeneration and nerve regeneration via impacts on Schwann cell migration and phagocytosis. Herein, we found low expression of microRNA-301a in intact sciatic nerves, with no impact of the microRNA-301a knockout on nerve structure and function. By contrast, we found significant upregulation of microRNA- 301a in injured sciatic nerves. We established a sciatic nerve crush model in microRNA-301a knockout mice, which exhibited attenuated morphological and functional regeneration following sciatic nerve crush injury. The microRNA-301a knockout also led to significantly inhibited Wallerian degeneration in an in vivo sciatic nerve-transection model and in an in vitro nerve explant block model. Schwann cells with the microRNA-301a knockout showed inhibition of phagocytosis and migration, which was reversible under transfection with microRNA-301a mimics. Rescue experiments involving transfection of microRNA-301a-knockout Schwann cells with microRNA-301a mimics or treatment with the C-X-C motif receptor 4 inhibitor WZ811 indicated the mechanistic involvement of the Yin Yang 1/C-X-C motif receptor 4 pathway in the role of microRNA-301a. Combined with our previous findings in macrophages, we conclude that microRNA-301a plays a key role in peripheral nerve injury and repair by regulating the migratory and phagocytic capabilities of Schwann cells and macrophages via the Yin Yang 1/C-X-C motif receptor 4 pathway.