MicroRNA-100 inhibits bone morphogenetic protein-induced osteoblast differentiation by targeting Smad1.

OBJECTIVE: MicroRNAs (miRNAs) act as key regulators of diverse cellular activities by regulating the expression of protein-coding genes. Osteoblast differentiation, a fundamental step in skeletal development, involves the activation of several signaling pathways, including transforming growth factor β (TGF-β), bone morphogenetic protein (BMP), and Wnt signaling pathways.

MATERIALS AND METHODS: miRNA expression was measured using TaqManRT-PCR. Western blot was used to detect the protein expression of Smad1. Luciferase reporter assay was used to measure the luciferase activity.

RESULTS: In this study, we found that miR-100 was expressed in mesenchymal progenitor cell lines; furthermore, its expression was reduced during osteoblast differentiation. Retroviral overexpression of miR-100 decreased Smad1 protein levels, whereas miR-100 inhibition had the opposite effect, suggesting that miR-100 acts as an endogenous attenuator of Smad1 in osteoblast differentiation.

CONCLUSIONS: Together, our data demonstrate that miR-100 acts as an important endogenous negative regulator of BMP-induced osteoblast differentiation.