Differential Expression of HIF-1α in Skin and Mucosal Wounds

Despite accelerated epithelial closure, oral mucosal wounds exhibit lower levels of VEGF and a more refined angiogenic response than do skin wounds. The specific differences in angiogenesis suggest that skin and oral mucosal wounds may experience dissimilar levels of hypoxia and HIF-1 alpha. Using a model of comparable wounds on murine dorsal skin and tongue, we determined levels of hypoxia and HIF-1 alpha. Skin wounds were found to be significantly more hypoxic and had higher levels of HIF-1 alpha than mucosal wounds. Furthermore, under stressed conditions, skin wounds, but not mucosal wounds, exhibited a further elevation of HIF-1 alpha beyond that of non-stressed levels. To determine if manipulation of oxygen levels might equalize the repair response of each tissue, we exposed mice to hyperbaric oxygen treatment (HBOT) following wounding. HBOT did not significantly change HIF-1 alpha or VEGF expression in either skin or mucosal wounds, nor did it alter wound bed vascularity. These studies suggest that skin wounds have higher levels of hypoxia than do mucosal wounds, along with a differential expression of HIF-1 alpha. Interestingly, modulation of oxygen by HBOT does not ameliorate this difference. These results suggest that differential responses to hypoxia may underlie the distinctive wound-healing phenotypes seen in skin and oral mucosa.