MicroRNA-132-3p represses Smad5 in MC3T3-E1 osteoblastic cells under cyclic tensile stress.

MicroRNAs (miRNAs) regulate osteogenic differentiation of bone cells, which has applications in orthodontics. Here we evaluated the miRNA expression profile of MC3T3-E1 osteoblasts under cyclic tensile stress with chip technology and found that miR-132-3p was up-regulated by 12% cyclic tensile stress. Alkaline phosphatase activity and osteocalcin expression in MC3T3-E1 cells were decreased under these conditions. Smad2 and Smad5 were identified as potential target genes of miR-132-3p. Native and phosphorylated Smad2 and Smad5 expression was negatively correlated with miR-132-3p levels in the cells under cyclic stretch; however, only Smad5 protein level was reduced upon miR-132-3p overexpression. The luciferase reporter assay confirmed a direct interaction between miR-132-3p and Smad5. Thus, miR-132-3p maybe regulates osteoblast differentiation via Smad5 in response to cyclic tensile stress.