Quercetin Stimulates Bone Marrow Mesenchymal Stem Cell Differentiation through an Estrogen Receptor-Mediated Pathway

Objectives. The present study aimed to investigate the overall effect of quercetin on mouse bone marrow mesenchymal stem cell (BMSC) proliferation and osteogenic differentiation in vitro. Materials and Methods. BMSCs were treated with different concentrations of quercetin for 6 days. The effects of quercetin on cell proliferation were assessed at predetermined times using Cell Counting Kit-8 (CCK-8) assay. The cells were then treated with quercetin, estrogen, or an estrogen receptor (ER) antagonist (which was also administered in the presence of quercetin or estrogen) for 7 or 21 days. The effects of quercetin on BMSC osteogenic differentiation were analyzed by an alkaline phosphatase (ALP) assay kit, Alizarin Red S staining (ARS), quantitative real-time PCR (qPCR), and western blotting. Results. The CCK-8 and ALP assays and ARS staining showed that quercetin significantly enhanced BMSC proliferation, ALP activity, and extracellular matrix production and mineralization, respectively. The qPCR results indicated that quercetin promoted osterix (OSX), runt-related transcription factor 2 (RUNX2), and osteopontin (OPN) transcription in the presence of osteoinduction medium, and the western blotting results indicated that quercetin enhanced bone morphogenetic protein 2 (BMP2), Smad1, Smad4, RUNX2, OSX, and OPN expression and Smad1 phosphorylation. Treatment with the ER inhibitor ICI182780 blocked the effects of quercetin. Conclusions. Our data demonstrated that quercetin promotes BMSC proliferation and osteogenic differentiation. Quercetin enhances BMP signaling pathway activation and upregulates the expression of downstream genes, such as OSX, RUNX2, and OPN, via the ER.