Abstract: Objective　To investigate the effect of miR-30d-5p on osteogenic differentiation and apoptosis of bone marrow stromal cells and its mechanism. Methods　Bone marrow stromal cells were divided into miR-30d-5p overexpression negative control group, miR-30d-5p overexpression group, miR-30d-5p inhibition negative control group and miR-30d-5p inhibition group. Alkaline phosphatase (ALP) staining was used to identify osteogenesis, alizarin red staining was used to detect calcium nodules precipitation, and TUNEL was used to detect apoptosis. mRNA and protein expression levels were detected by qPCR and Western blot, and the potential binding sites of miR-30d-5p were predicted by the bioinformatics analysis website Targetscan7.1. Results　After miR-30d-5p overexpression, osteogenic differentiation ability, and mineralization ability of the cells decreased (P<0.05), while apoptosis level increased (P<0.05). The expression of glucoregulatory protein 78 (GRP78) and osteogenic specific transcription factor RUNX2 was significantly decreased (P<0.05). However, miR-30d-5p inhibitor-treated the cells with increased osteogenic differentiation and mineralization ability (P<0.05), and apoptosis level decreased (P<0.05). GRP78 and RUNX2 protein levels increased (P<0.05). The miR-30d-5p binding site is located at 142-148bp of the 3'UTR of the GRP78 gene. Conclusion　MiR-30d-5p inhibits osteogenic differentiation and promotes apoptosis of bone marrow stromal cells by down-regulating the expression of GRP78 protein.

Key words: Bone formation, Osteogenic differentiation, Mineralization, MicroRNA-30d-5p, Real-time PCR