Quercetin promotes human epidermal stem cell proliferation through the estrogen receptor/β-catenin/c-Myc/cyclin A2 signaling pathway.

Skin epidermal stem cells (EpSCs) play an important role in wound healing. Quercetin is a phytoestrogen reported to accelerate skin wound healing, but its effect on EpSCs is unknown. In this study, we investigated the effect of quercetin on human EpSC proliferation and explored the underlying mechanisms. We found that quercetin at 0.1~1 μM significantly promoted EpSC proliferation and increased the number of cells in S phase. The pro-proliferative effect of quercetin on EpSCs was confirmed in cultured human skin tissue. Mechanistic studies showed that quercetin significantly upregulated the expressions of β-catenin, c-Myc, and cyclins A2 and E1. Inhibitor for β-catenin or c-Myc significantly inhibited quercetin-induced EpSC proliferation. The β-catenin inhibitor XAV-939 suppressed quercetin-induced expressions of β-catenin, c-Myc, and cyclins A2 and E1. The c-Myc inhibitor 10058-F4 inhibited the upregulation of c-Myc and cyclin A2 by quercetin. Pretreatment of EpSCs with estrogen receptor (ER) antagonist ICI182780, but not the G protein-coupled ER1 antagonist G15, reversed quercetin-induced cell proliferation and upregulation of β-catenin, c-Myc, and cyclin A2. Collectively, these results indicate that quercetin promotes EpSC proliferation through ER-mediated activation of β-catenin/c-Myc/cyclinA2 signaling pathway and ER-independent upregulation of cyclin E1 and that quercetin may accelerate skin wound healing through promoting EpSC proliferation. As EpSCs are used not only in clinic to treat skin wounds but also as seed cells in skin tissue engineering, quercetin is a useful reagent to expand EpSCs for basic research, skin wound treatment, and skin tissue engineering.