MicroRNA-125b regulates osteogenic differentiation of mesenchymal stem cells by targeting Cbfβ in vitro.

Differentiation of mesenchymal stem cells (MSCs) into a specific lineage is firmly and precisely regulated via crucial transcription factors and signaling cascades, but the accurate mechanisms still need to be revealed. MicroRNAs (miRNA) negativity regulates the target mRNA protein synthesis to regulate various kinds of biological processes. In the present study we investigate miRNAs mediated regulatory mechanisms of osteoblastic differentiation in C3H10T1/2 cells and we identified that the level of miR-125b expression was obviously decreased compared with undifferentiated ones during differentiation process. Subsequently, dual-luciferase reporter gene assay data demonstrated that miR-125b targets a putative binding site in the 3'-UTR of Cbfβ gene, a key transcription factor for osteogenesis. We observed over and interferential expression of miR-125b down-regulate for Cbfβ protein in C3H10T1/2 cells and the over-expression decrease the mRNA levels of three osteoblastic marker genes, alkaline phosphatase (ALP), osteocalcin (OCN), osteopontin (OPN) by BMP-2-induced, whereas, anti-miR-125b increased the expression of these marker genes and hence up-regulated mRNA levels of Cbfβ. It is concluded from the result that miR-125b is a key regulatory factor of osteoblastic differentiation by directly targeting Cbfβ and indirectly acting on Runx2 at an early stage osteoblastic differentiation.