Expression of microRNA-21 in bone tissue and serum of patients with osteoporosis (OP) and its involvement in the regulation of osteogenic differentiation of rat bone marrow mesenchymal stem cells (BMSCs) were investigated. Bone tissue and serum were collected from 48 patients with OP and 48 normal subjects. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression of six microRNAs. Among these microRNAs, the expression level of microRNA-21 in bone tissue and serum of OP patients was the lowest. In addition, BMSCs of SD rats were isolated and cultured. Subculture was performed 3 times, transfection of microRNA-21 was performed and osteogenic differentiation was induced. Control group [negative control (NC)] was transfected with microRNA-21 mimics followed by osteogenic induction. Experimental groups were transfected with microRNA-21 analogue (mimics) and microRNA-21 inhibitor (inhibitor) followed by osteogenic induction. Ten days after osteogenic induction, alkaline phosphatase (ALP) staining and alizarin red staining were performed to measure the mineralized stained area and the number of mineralized nodules in each treatment group. RT-qPCR was used to detect the expression of osteogenic genes in each group of cells. RT-qPCR results showed that microRNA-21 expression was lower in bone tissue and serum of patients with OP than that of normal subjects. Moreover, compared with control group, BMSCs showed increased stained mineralized areas, deeper color and increased number of mineralized nodules. In addition, increased mRNA expression of osteogenic genes was evident after microRNA-21 mimics transfection and osteogenic induction (p<0.05). Compared with control group, BMSCs showed decreased stained mineralized areas, lighter color, decreased number of mineralized nodules, and decreased mRNA expression of osteogenic genes after microRNA-21 inhibitor transfection and osteogenic induction (p<0.05). MicroRNA-21 is expressed at low level in bone tissue and serum in patients with OP, and microRNA-21 can promote osteogenic differentiation of BMSCs. Our study provided theoretical basis for drug treatment of OP.
Keywords: bone marrow mesenchymal stem cells; microRNA-21; osteogenic differentiation; osteoporosis.