Nitric oxide promotes epidermal stem cell proliferation via FOXG1-c-Myc signalling

Objective: Epidermal stem cells (ESCs) play a critical role in wound repair, but the mechanism underlying ESC proliferation is unclear. Here, we explored the effects of nitric oxide (NO) on ESC proliferation and the possible underlying mechanism. Methods: The effect of NO (two NO donors, SNAP and spermine NONOate, were used) on cell proliferation was detected using cell proliferation and DNA synthesis assays. Thereafter, expression of FOXG1 and c-Myc induced by NO was determined by immunoblot analysis. pAdEasy-FOXG1 adenovirus and c-Myc siRNA plasmids were infected or transfected, respectively, into human ESCs to detect the effect of FOXG1 and c-Myc on NO-induced cell proliferation. Additionally, NO-induced ESC proliferation in vivo was detected by BrdU incorporation and a superficial second-degree mouse burn model. Moreover, the relationships among NO, FOXG1 and c-Myc were detected by western blotting, real-time PCR and dual luciferase assay. Results: NO exerted a biphasic effect on ESC proliferation, and 100 mu M SNAP and 10 mu M spermine NONOate were the optimal concentrations to promote cell proliferation. Additionally, NO-promoted human ESC proliferation was mediated by FOXG1 and c-Myc in vitro and vivo. Furthermore, NO regulated FOXG1 expression through cGMP signalling, and NO-induced transcription of c-Myc was regulated by FOXG1-mediated c-Myc promoter activity. Conclusion: This study showed that the biphasic effect of NO on ESC proliferation as well as NO induced ESC proliferation were regulated by the cGMP/FOXG1/c-Myc signalling pathway, suggesting that NO may serve as a new disparate target for wound healing.