MiR-125b regulates osteogenic differentiation of human bone marrow mesenchymal stem cells by targeting Smad4

Abstract

To investigate whether miR-125b regulates the osteogenic differentiation of bone marrow mesenchymal stem cells (MSCs) by modulating Smad4, a predicted target in silicon. Smad4 3'-UTR-luciferase vector was constructed and dual-luciferase reporter gene assay was employed to examine the effect of miR-125b on luciferase activity. MSCs were isolated and cultured from human bone marrow, and then transfected with miR-125b mimics followed by induction of osteogenic differentiation. qRT-PCR and Western blot were used to detect the expressions of Smad4 mRNA and protein. MSCs were induced into the osteoblasts after transfecting with Smad4 siRNA, and the effect of Smad4 downregulation on osteogenic differentiation was observed by AKP activity and RUNX2 mRNA levels. miR-216b bound Smad4 3'-UTR and inhibited the luciferase activity (P<0.05). Smad4 mRNA and protein expressions were significantly down-regulated in the MSCs induced into osteogenic differentiation when miR-125b was overexpressed. Downregulation of Smad4 suppressed the AKP activity and RUNX2 mRNA expression, indicating that Smad4 siRNA simulated at least in part the function of miR-125b as the regulator of MSCs osteogenic differentiation. miR-125b can suppress MSCs osteogenic differentiation by directly targeting Smad4.