miR-381 modulates human bone mesenchymal stromal cells (BMSCs) osteogenesis via suppressing Wnt signaling pathway...

The osteogenic differentiation of human bone mesenchymal stromal cells (BMSCs) has been considered as a central issue in fracture healing. Wnt signaling could promote BMSC osteogenic differentiation through inhibiting PPARγ. During atrophic nonunion, Wnt signaling-related factors, WNT5A and FZD3 proteins, were significantly reduced, along with downregulation of Runx2, ALP, and Collagen I and upregulation of PPARγ. Here, we performed a microarray analysis to identify differentially expressed miRNAs in atrophic nonunion tissues that were associated with Wnt signaling through targeting related factors. Of upregulated miRNAs, miR-381 overexpression could significantly inhibit the osteogenic differentiation in primary human BMSCs while increase in PPARγ protein level. Through binding to the 3'UTR of WNT5A and FZD3, miR-381 modulated the osteogenic differentiation via regulating β-catenin nucleus translocation. Moreover, PPARγ, an essential transcription factor inhibiting osteogenic differentiation, could bind to the promoter region of miR-381 to activate its expression. Taken together, PPARγ-induced miR-381 upregulation inhibits the osteogenic differentiation in human BMSCs through miR-381 downstream targets, WNT5A and FZD3, and β-catenin nucleus translocation in Wnt signaling. The in vivo study also proved that inhibition of miR-381 promoted the fracture healing. Our finding may provide a novel direction for atrophic nonunion treatment.