Low expression of miR-1 promotes osteogenic repair of bone marrow mesenchymal stem cells by targeting TLR1.

OBJECTIVE: Bone marrow mesenchymal stem cells (BMSCs) promote bone tissue repair. MiR-1 regulates myogenic and osteogenic differentiation of human adipose tissue stem cells. However, miR-1's effect on BMSCs osteogenesis is unclear. MATERIALS AND METHODS: Rat BMSCs were isolated and divided into control group, miR-1 group, and si-miR-1 group respectively transfected with miR-1 plasmid and miR-1 siRNA followed by analysis of cell proliferation by MTT assay and Caspase 3 activity. The expression of osteogenic genes Runx2 and OPN was measured by Real Time-PCR. Healthy male Sprague-Dawley rats were separated into fracture group. NC group, and si-miR-1 group followed by analysis of bone mineral density, miR-1 level by Real Time-PCR, type I collagen, and BMP-2 by enzyme-linked immunosorbent assay (ELISA), and TLR1 expression by Western blot. RESULTS: Transfection of miR-1 siRNA into BMSCs significantly downregulated miR-1 expression, promoted BMSCs cell proliferation, inhibited Caspase 3 activity, as well as promoted osteogenic genes Runx2 and OPN expression and decreased TLR1 expression (p<0.05). The upregulation of miR-1 expression significantly reversed the above changes. TLR1 is a target of miR-1. Downregulation of miR-1 expression in BMSCs of fractured rats significantly increased bone density and ALP activity, promoted type I collagen and BMP-2 expression, and decreased TLR1 expression (p<0.05). CONCLUSIONS: The downregulation of miR-1 promotes BMSCs osteogenic differentiation via targeting TLR1, which promotes osteogenic differentiation and bone healing.