Biphasic positive effect of formononetin on metabolic activity of human normal and osteoarthritic subchondral osteoblasts.

Osteoarthritis is a multifactorial disease characterized by loss of articular cartilage and subchondral plate thickening. Therefore, biochemical analysis of the underlying bone tissue has provided important information for treatment of osteoarthritis. In this study, we determined the potential role of formononetin, a phytoestrogen isolated from Astragalus membranaceus to alter the expression of metabolic markers and cytokine production of human normal osteoblasts (Obs) and osteoarthritis subchondral osteoblasts (OA Obs). Human OA Obs and normal Obs were cultured for 3days, 7days or 14days in the present medium only or were treated with various doses of formononetin. Cells were analyzed for viability by WST-8 assay, alkaline phosphatase (ALP) activity, osteogenic markers (osteocalcin (OCN) and type I collagen (Col I)) and cytokines (interleukin-6 (IL-6), vascular endothelial growth factor (VEGF), bone morphogenic protein-2 (BMP-2)). The level of IL-6, VEGF, BMP-2, OCN and Col I was increased in OA Obs compared with normal Obs. Formononetin dose-dependently decreased ALP, IL-6, VEGF, BMP-2, OCN and Col I in OA Obs, while markedly increased ALP, VEGF, BMP-2, OCN and Col I in normal Obs. Interestingly, formononetin markedly increased the expression of VEGF and BMP-2 for 3days of culture and significantly increased OCN and Col I at 14days in human normal Obs. The remodeling effect of formononetin on osteogenic markers and cytokines of inflammatory mediators was more striking in OA Obs as well. Taken together, these results could suggest that formononetin has biphasic positive effects on normal Obs and OA Obs by modifying their biological synthetic capacities.