Dioscin promotes osteoblastic proliferation and differentiation via Lrp5 and ER pathway in mouse and human osteoblast-like cell lines

Background: Dioscin, a typical steroid saponin, is isolated from Dioscorea nipponica Makino and Dioscorea zingiberensis Wright. It has estrogenic activity and many studies have also reported that dioscorea plants have an effect in preventing and treating osteoporosis. However, the molecular mechanisms underlying their effect on osteoporosis treatment are poorly understood. Therefore, the present study aims to investigate the mechanism (s) by which dioscin promotes osteoblastic proliferation and differentiation in mouse pre-osteoblast like MC3T3-E1 cells and human osteoblast-like MG-63 cells. Results: We found that dioscin (0.25 mu g/ml, 0.5 mu g/ml, and 1.0 mu g/ml) promoted MC3T3-E1 cells and MG-63 cells proliferation and differentiation dose dependently. Western blot analysis results showed that estrogen receptor a (ER-a), estrogen receptor beta (ER-beta), beta-catenin and Bcl-2 protein expression increased after MC3T3-E1 cells were treated with dioscin. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis indicated that dioscin could increase the ratio of osteoprotegerin (OPG)/receptor activator of NF-kappa B ligand (RANKL) and up-regulate the level of Lrp5 and beta-catenin. And by RNA interference analysis, we proved that the effect of dioscin increasing the ratio of OPG/RANKL was dependent on Lrp5 pathway. In addition, we also found that these effects of dioscin were abolished by ICI 182, 780 (100 nM), an antagonist of ER, indicating that an ER signaling pathway was also involved. We also found that dioscin (0.25 mu g/ml, 0.5 mu g/ml, and 1.0 mu g/ml) induced MG-63 cells proliferation and differentiation in a dose-dependent manner. Western blot analysis results indicated that ER-alpha, ER-beta and beta-catenin protein expression increased after MG-63 cells were treated with dioscin. Conclusions: The current study is the first to reveal that dioscin can promote osteoblasts proliferation and differentiation via Lrp5 and ER pathway.