MiR-545-3p Upregulated in Osteoporosis and Regulates The Apoptosis of Osteoblasts by Targeting SIRT6

Abstract

Background: The imbalance of proliferation and apoptosis plays an important role in the pathogenesis of osteoporosis. MicroRNAs play an important role in the apoptosis of osteoblasts cells. However, the role and potential mechanism of miR-545-3p in regulating osteoblast apoptosis remain unclear. The purpose of this study was to investigate the effect of miR-545-3p on osteoblast cells apoptosis and explore the mechanism of osteoporosis.Methods: Osteogenic medium was used to induce the differentiation of osteoblasts MC3T3-E1 to construct the osteoporosis model, and the expression of ALP, Runx2, OCN were detected by western blot; miR-545-3p mRNA was detected by RT-PCR. Transfected with miR-545-3p mimics into MC3T3-E1, then flow cytometry was used to detected the changes of apoptosis status. The expression of apoptosis related proteins Bcl-2 and Bax were detected by western blot. Bioinformatics was used to analyze the binding protein of miR-545-3p, and luciferase reporter gene experiment was used to verify whether miR-545-3p directly targets SIRT6; RT-qPCR and western blot were used to detect the expression level of SIRT6 after transfection of miR-545-3p mimics or miR-545-3p inhibitor. After co-transfection of miR-545-3p mimics and pcDNA3.1-SIRT6, the apoptosis status of osteoblasts was analyzed by flow cytometry, and the expression of apoptosis related proteins Bcl-2 and Bax were detected by western blot.Results: The expression of miR-545-3p in patients with osteoporosis was significantly higher than that of normal in GEO database (P<0.05). After osteoblasts were cultured in osteogenic medium, the expression of ALP, Runx2 and OCN was increased, and the expression of miR-545-3p was decreased. Flow cytometry analysis showed that overexpression of miR-545-3p promoted the apoptosis of osteoblasts. Western blot results showed that overexpression of miR-545-3p promoted the expression of Bax and decreased the expression of Bcl-2. Bioinformatics analysis showed that miR-545-3p could target SIRT6. The results of real-time PCR and western blot showed that SIRT6 expression was significantly inhibited by miR-545-3p mimics (P<0.05). Luciferase reporter gene assay showed that miR-545-3p significantly inhibited luciferase activity of wild-type SIRT6-3'UTR plasmid transfected cells (P<0.05), but had no effect on luciferase activity of mutant SIRT6-3'UTR plasmid transfected cells (P<0.05). However, co-transfection of miR-545-3p mimics and pcDNA3.1-SIRT6 could reduce the apoptosis, and western blot results showed that co-transfection promoted the expression of Bcl-2 and decreased the expression of Bax.Conclusions: miR-545-3p can promote the apoptosis of osteoblasts by inhibiting the expression of SIRT6, which provides a certain idea for the treatment of osteoporosis.