Vitexin enhances osteoblast differentiation through phosphorylation of Smad and expression of Runx2 at in vitro and ex vivo

Vitexin (apigenin-8-C-d-glucopyranoside) is a flavonoid isolated from natural sources. It has been employed as an anti-oxidant, anti-inflammatory, and anti-cancer agent, and is used as a traditional Chinese medicine to treat a variety of illnesses. The present study investigated the effect of vitexin on osteoblast differentiation of C3H10T1/2 mesenchymal stem cells, MC3T3-E1 preosteoblast, mouse calvarial primary cells, and primary bone marrow stem cells (BMSCs). RT-PCR and quantitative PCR demonstrated that vitexin increased mRNA expression of the osteogenic genes distal-less homeobox 5 (Dlx5) and Runxt-related transcription factor 2 (Runx2). Vitexin also increased the Dlx5 and Runx2 protein levels, Smad1/5/9 phosphorylation, and alkaline phosphatase (ALP) activity. In addition, vitexin increased Runx2-luciferase activity. Moreover, knockdown of Runx2 attenuated the increase in ALP activity induced by vitexin. These results demonstrate that vitexin enhances osteoblast differentiation via Runx2.