Hypoxic microenvironment promotes dermal fibroblast migration and proliferation via a BNIP3-autophagy pathway

Upon injury, nearby cells, including fibroblasts at the wound edge, are often found in a hypoxic microenvironment. Nevertheless, the influence of hypoxia on skin fibroblasts is poorly understood. Using previously established mouse full-thickness wounds, we show that Bcl-2 and adenovirus E1B 19-kDa interacting protein 3 (BNIP3) expression was significantly elevated at the wound edge, and hypoxia treatment enhanced BNIP3 expression in fibroblasts. Interestingly, BNIP3 promoted the migration and proliferation, as well as the activation of autophagy, in fibroblasts under hypoxia. The hypoxia-induced autophagy was found to induce the migration and proliferation of fibroblasts, a process that could be reversed by knocking down the autophagy-related gene for autophagy protein 5, ATG5. Furthermore, hypoxia-inducible factor 1 subunit alpha (HIF-1 alpha) was significantly upregulated in fibroblasts under hypoxia treatment, and HIF-1 alpha knockdown attenuated the hypoxia-induced expression of BNIP3 and the migration and proliferation of fibroblasts. Altogether, our results establish the hypoxia-BNIP3-autophagy signaling axis as a newly identified regulatory mechanism of skin fibroblast migration and proliferation upon wounding. Autophagy intervening might thus represent a promising therapeutic strategy for patients with chronic refractory wounds.