MicroRNA-145 regulates osteoblastic differentiation by targeting the transcription factor Cbfb

•miR-145 is a crucial regulator of Cbfb expression, an indispensable partner for Runx2.•miR-145 inhibits osteoblastic differentiation in cooperation with miR-34c, which targets Runx2.•miR-145 affects the physiological bone regenerative process in vivo. Osteoblastic differentiation is regulated by various factors, including hormones and transcription factors. Runt-related transcription factor 2 (Runx2) is an essential player in osteoblastogenesis and transactivates its molecular target by creating a protein complex with its hetero-dimeric partner core binding factor beta (Cbfb). However, the molecular regulation of Cbfb expression remains unknown. Here, we identified miR-145 as a crucial regulator of Cbfb expression. The expression of miR-145 increased during osteoblastogenesis, indicating that miR-145 works as an inhibitor of osteoblastogenesis. Stable expression of miR-145 decreased endogenous Cbfb expression and inhibited osteoblastogenesis, in cooperation with miR-34c. Furthermore, miR-145 decreased bone regeneration in vivo. Our results indicate that miR-145 physiologically regulates osteoblast differentiation and bone formation via Cbfb expression by forming a regulatory microRNA network.