Overexpression of miR-195-5p reduces osteoporosis through activating BMP-2/SMAD/Akt/RUNX2 pathway via targeting SMURF1.

Osteoporosis (OP) is among the most common frequent chronic metabolic bone diseases in postmenopausal women. Here, the effect and underlying mechanisms of miR-195-5p in OP were investigated both in vivo and in vitro. In this study, the microgravity (MG) environment was simulated in MC3T3-E1 cells, and miR-195-5p overexpression or SMURF1 knockdown model was constructed to test their effects on the proliferation, apoptosis and osteogenic differentiation of MC3T3-E1 cells. Furthermore, an OVX mouse model was constructed in vivo, and adenovirus-loaded miR-195-5p mimics were administered to the mice to overexpress miR-195-5p. HE staining and µCT were adopted to observe pathological changes of femur. The targeted relationship between miR-195-5p and SMURF1 was predicted by bioinformatics analysis and verified by the dual-luciferase reporter assay and RNA immunoprecipitation (RIP) experiment. The results indicated that miR-195-5p was down-regulated in the head of femur of OP mouse model and MC3T3-E1 cells subjected to MG microenvironment. In addition, overexpression of miR-195-5p promoted MC3T3-E1 cell osteogenic differentiation and inhibited apoptosis. Mechanistically, SMURF1 is identified as a target of miR-195-5p, and overexpressing miR-195-5p activates the BMP-2/SMAD/Akt/RUNX2 signal by inhibiting the SMURF1 expression. Moreover, SMURF1 downregulation accelerated the osteogenic differentiation of MC3T3-E1 cells and attenuated MG-mediated apoptosis. In addition, upregulating miR-195-5p reduced osteoporosis in the OVX mouse model, accompanied with SMURF1 downregulation and BMP-2/SMAD/Akt/RUNX2 pathway activation. Collectively, miR-195-5p enhances osteogenic differentiation of osteoclast and relieve OP progression in the mouse model through activation of the BMP-2/SMAD/Akt/RUNX2 axis by targeting SMURF1.