Abstract： Objective:To investigate the effects of quercetin on the cell proliferation, apoptosis, cell cycle, surface markers expression and osteogenic differentiation of human gingival mesenchymal stem cells (GMSCs) .Methods:Using GMSCs without quercetin treatment as the control group, and the effects of quercetin at levels of 2.5, 5, 10, and 20 μmol/L on GMSCs proliferation were examined with CCK-8 assay. At 96 h after treatment with 10 μmol/L and 20 μmol/L quercetin, the GMSCs cells were examined for apoptosis and surface markers expression with flow cytometry, and the protein expression of cleaved PARP, p-BCL-2, Bax, and cleaved caspase 3 with Western blotting. At 4 weeks after treatment with 10 μmol/L quercetin, Alizarin red staining was used to determine the effect of quercetin on osteogenic differentiation of GMSCs.Results:Compared with the control group, the viability of GMSCs treated with various levels of quercetin was significantly decreased. The viability of GMSCs after treatment with 2.5, 5, 10, and 20 μmol/L quercetin for 96 h was 78.93%, 66.81%, 56.35%, and 39.22%, respectively ( P<0.05) . At 96 h after treatment with various levels of quercetin, flow cytometry showed significantly increases in the number of early or late apoptotic GMSCs, with the apoptotic rates in the control group, 10 μmol/L and 20 μmol/L quercetin groups being 8.30%, 17.88%, and 20.77%, respectively ( P<0.05) ; Western blotting showed that, compared with the control group, GMSCs treated with 10 μmol/L and 20 μmol/L quercetin had higher protein expression of the pro-apoptotic cleaved PARP, Bax and cleaved caspase 3 proteins, and lower expression of anti-apoptotic p-BCL-2 protein (all P<0.05) . Flow cytometry showed that, compared with the control group, GMSCs treated with 10 μmol/L quercetin resulted in lowered CD90 positivity from 88.4% to 15.3%; those treated with 20 μmol/L quercetin resulted in higher CD45 positivity from 3.18% to 9.77%, and higher CD34 positivity 1.08% to 5.70% (all P<0.05) . Alizarin red staining did not show formation of mineralized nodules in GMSCs at 4 weeks after treatment with 10 μmol/L quercetin. Conclusion:Quercetin may significantly inhibit the cell function of GMSCs, suggesting the need to avoid the interference by quercetin and other flavonoids in the culture or therapeutic use of GMSCs.