MicroRNA-133b negatively regulates the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells

Osteogenic differentiation of bone marrow mesenchymal stem cells (BMMSCs) is accurately regulated by essential transcription factors and signaling cascades. However, the precise mechanisms involved in this process remain unknown. MicroRNAs (miRNAs) regulate various biological processes by binding target mRNA to attenuate protein synthesis. The purpose of this study was to investigate the role of miR-133b in regulation of BMMSC proliferation and osteogenic differentiation. Quantitative real time PCR was performed to investigate the expression pattern of miR-133b during osteogenic differentiation of MSCs at different time points. Then the effects of miR133b downreguation/upregulation on proliferation and osteogenic differentiation were evaluated by MTT, expression levels of osteogenic differentiation markers and Alizarin red S staining. The expression level of miR-133b was downregulated during osteogenic differentiation of BMMSCs (P<0.01). miR-133b-specific siRNA promoted proliferation and osteogenic differentiation of BMMSCs, with increased mRNA expression of the osteogenic markers alkaline phosphatase (ALP), runt-related transcription factor (RUNX2), osteocalcin (OCN) and bone morphogenetic protein 2 (BMP-2) as well as stronger intensity of Alizarin red S staining (P<0.05, P<0.01). Opposite findings were observed when miR-133b was overexpressed. In conclusion, miR-133b plays a important role in regulating the proliferation and osteogenic differentiation of BMMSCs.