Silymarin enhanced matrix mineralization and boosted osteogenesis possibly through SMAD signaling

Bone is maintained by the balance between bone formation by osteoblast and bone resorption by osteoclast. Bone‐remodeling imbalance induced by increased bone resorption and over bone formation causes adult skeletal diseases such as osteoporosis. Silymarin(SM) is the mixture of milk flavonolignans extracted from blessed milk thistle. Several studies suggest that SM is a powerful antioxidant and has antihepatotoxic properties. This study was conducted to investigate that the enhancement of SM on matrix mineralization and then boosted osteogenesis effects. Mouse osteoblastic MC3T3‐E1 cells were treated with a 1–20 μM SM for 15 d in a differentiate medium. It was found that SM had a significant induction of osteoblast proliferation and differentiation. Additionally, cell and medium alkaline phosphatase activities, matrix ALP activity, secretion of collagen type 1 and matrix mineralization were enhanced by SM, as determined by Alizarin red stainings. SM at ≥ 10 μM activates bone morphogenetic protein‐2 (BMP‐2) expression and the effect of SM was mediated most likely through a SMAD signaling pathway, in which phospho‐SMADs triggered Runx2 transcripts into a nuclears causing osteocalcin expression. It was confirmed by a real‐time PCR. In conclusion, our findings demonstrate that SM could be a potential therapeutic agent for the prevention osteoporosis.