miR-221 and miR-222 promote Schwann cell proliferation and migration by targeting LASS2 after sciatic nerve injury.

microRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at the post-transcriptional level. Their roles in regulating the responses of Schwann cells (SCs) to injury stimuli remain unexplored. Here we report dynamic alteration of miRNA expression following rat sciatic nerve injury using microarray analysis. We harvested the proximal nerve stumps and identified 77 miRNAs that showed significant changes at four time points after nerve transection. Subsequently, we analyzed the expression pattern of miRNA, selected one significant profile, and then integrated putative miRNA targets with differentially expressed mRNA yielding 274 potential targets. The 274 targets were mainly involved in cell proliferation, cell locomotion and cellular homeostasis that were known to play important roles in modulating cell phenotype. The upregulation of the miR-221 and miR-222 cluster (miR-221/222) was found to correlate with the injury-induced SC phenotypic modulation. Enhanced expression of miR-221/222 could promote SC proliferation and migration in vitro, whereas silencing their expression resulted in a reduced proliferation and migration. Further studies revealed that longevity assurance homologue 2 (LASS2) was a direct target of miR-221/222 in SCs because miR-221/222 bound directly to the 3'-untranslated region of LASS2, thus reducing both mRNA and protein levels of LASS2. Silencing of LASS2 recapitulated the effects of miR-221/222 mimics, whereas enforced knockdown of LASS2 reversed the suppressive effects of miR-221/222 inhibitors. Our findings indicate that injury promotes SC proliferation and migration through the regulation of miR-221/222 by targeting LASS2, and provide new insights into the role of miRNAs in nerve regeneration.