ABSTRACT
BACKGROUND:Induction of osteoblasts differentiating into osteocytes is a hot spot in tissue engineering;however, the regulatory mechanism underlying differentiation has not been ful y elucidated. MicroRNA, as an endogenous smal RNA molecule, can regulate post-transcriptional gene expression by binding to the 3’ nontranslated region of the target gene mRNA, which also has been found to play an important regulatory role in osteocyte differentiation. OBJECTIVE:To study the regulation of miR-155 on osteoblast differentiation and the underlying mechanism. METHODS:The mouse osteoblast cel lines MC3T3-E1 were selected and induced by mouse bone morphogenetic protein-2 (BMP2, 200 ng/mL) and then the miR-155 mRNA expression was determined by quantitative real-time PCR at 1, 3, 7 and 14 days. MC3T3-E1 cel s were divided into control, BMP2, miR-155 and miR-155 inhibitor groups, fol owed by cultured withα-MEM medium, BMP2, miR-155 and miR-155 inhibitor, respectively, for 2 weeks. RESULTS AND CONCLUSION:After induction using BMP2, miR-155 expression was downregulated in a time dependent manner. The staining intensity of alizarin red in the BMP2 group was significantly higher than that of the control group, and the activity of alkaline phosphatase and mRNA expression were also significantly higher than those in the control group (P<0.01). The staining intensity of alizarin red, activity of alkaline phosphatase and mRNA expression in the miR-155 group were significantly lower than those in the control group (P<0.01), while al above measurements were reversed significantly by miR-155 inhibitor (P<0.05). miR-155 could bind to the 3’ untranslated region of SMAD5 mRNA and significantly downregulated the expressions of SMAD5 protein and mRNA in MC3T3-E1 cel s (P<0.01). These results show that miR-155 can inhibit MC3T3-E1osteogenic differentiation by downregulating SMAD5 expression.