Abstract: Objective To compare the expression of miR-181b in bone marrow-derived mesenchymal stem cells (BM-MSCs) between health controls and adolescent idiopathic scoliosis (AIS) patients and to study the role of miR-181b in osteogenic differentiation of BM-MSCs. Methods The expression of miR-181b in BM-MSCs from health controls and AIS patients were detected by RT-qPCR. To investigate the function of miR-181b, BM-MSCs were transfected with miR-181b mimic, inhibitor or their corresponding controls, and culture medium was then changed to osteogenic induction medium. RT-qPCR and Western blot were used to detect the expression of osteogenesis markers and specific transcriptional factors. ALP staining and ALP activity assay were used to detect early ostogenic differentiation. Alizarin red staining was used to determine later osteogenic differentiation. Lentivirus was utilized to overexpress or block miR-181b in BM-MSCs, and the effects of miR-181b on bone formation were evaluated in ectopic bone formation model in nude mice. Western blot was used to detect the levels of phosphorylation ERK1/2 after miR-181b was overexpressed or blocked. Results MiR-181b was remarkably upregulated in AIS BM-MSCs compared with that of health control. Overexpression of miR-181b suppressed osteogenic differentiation of BM-MSCs in vitro and impaired ectopic bone formation in vivo. Inhibition of endogenous miR-181b promoted ostogenic differentiation of BM-MSCs in vitro and enhanced ectopic bone formation of BM-MSCs in vivo. Mechanistcally, overexpression of miR-181b inhibited the phosphorylation of ERK1/2, while blocking miR-181b elevated the phosphorylation of ERK1/2. Conclusions MiR-181b suppresses osteogenic differentiation of BM-MSCs and may be responsible for decreased bone mineral density of AIS.

Key words: Adolescent Idiopathic Scoliosis AIS, Mesenchymal stem cells, Osteogenic differentiation, miR-181b