Elucidation of the molecular mechanisms that regulate the differentiation of adipose-derived mesenchymal stem cells into osteogenic cells may lead to new methods for bone tissue engineering. We examined the role of miR-26a-5p in the regulation of osteogenic differentiation of mouse adipose-derived mesenchymal stem cells (mADSCs) by using mimics and inhibitors of this microRNA. Our results showed that over-expression of miR-26a-5p inhibited osteogenesis and that suppression of endogenous miR-26a-5p promoted osteogenesis. Four bioinformatics algorithms indicated that the 3'UTR of Wnt5a was a potential target of miR-26a-5p. We confirmed this prediction by use of dual-luciferase reporter assay and GFP/RFP assay. We also examined the molecular mechanisms by which miR-26a-5p regulates osteogenesis. Fura-2AM and Western blot assays after transfection indicated that miR-26a-5p repressed WNT5A, inhibited calcium flux and protein kinase C, and suppressed osteogenic differentiation of mADSCs. By contrast, miR-26a-5p inhibition activated these signal proteins and promoted osteogenic differentiation. Taken together, our results suggest that up-regulation of miR-26a-5p inhibits osteogenic differentiation of mADSCs by directly targeting the 3'UTR of Wnt5a, thereby down-regulating the Wnt/Ca(2+) signaling pathway.
Keywords: Adipose-derived mesenchymal stem cell (ADSC); MicroRNA-26a-5p; Non-canonical Wnt pathway; Osteogenic differentiation; WNT5A.