miR-22 represses osteoblast viability with ESR1 presenting a direct target and indirectly inactivating p38 MAPK/JNK signaling.

Background MicroRNAs (miRs) hold critical implications in the modulation of osteogenesis. This work was designed to unravel the underlying regulatory mechanism of miR-22 during osteoblast differentiation. Methods Synthetic miR-22 mimics or inhibitors were transfected into preosteoblast MC3T3-E1 cells to regulate miR-22 expression. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] and flow cytometry analyses were employed to assess cell proliferation and apoptosis. A quantitative real-time polymerase chain reaction and western blot assays were applied to measure mRNA and protein expression. Alkaline phosphatase activity and alizarin red staining were tested to further analyze cell differentiation. In silico analysis and luciferase reporter assays were utilized to identify the direct binding between miR-22 and its potential target. Results MTT and flow cytometry analyses showed that miR-22 repressed MC3T3-E1 cell viability and promoted cell apoptosis. By detecting osteogenic-specific molecule expression, alkaline phosphatase activity and alizarin red staining, miR-22 was observed to suppress osteogenic differentiation of MC3T3-E1 cells. In silico analysis and luciferase reporter assays confirmed that ESR1 is a direct target gene of miR-22. In addition, miR-22 expression affected the phosphorylation of p38 mitogen-activated protein kinase and Jun N-terminal kinase expression in MC3T3-E1 cells. Conclusions The findings of the present study highlight the functional significance of miR-22 in osteoblast differentiation and suggest its role as a possible therapeutic target in metabolic bone disorders.