Abstract
Wound healing is impaired in elderly patients with diabetes mellitus. We hypothesized that age-dependent impairment of cutaneous wound healing in db/db diabetic mice: (a) would correlate with reduced expression of the transcription factor hypoxia-inducible factor 1alpha (HIF-1alpha) as well as its downstream target genes; and (b) could be overcome by HIF-1alpha replacement therapy. Wound closure, angiogenesis, and mRNA expression in excisional skin wounds were analyzed and circulating angiogenic cells (CACs) were quantified in db/db mice that were untreated or received electroporation-facilitated HIF-1alpha gene therapy. HIF-1alpha mRNA levels in wound tissue were significantly reduced in older (4-6 months) as compared to younger (1.5-2 months) db/db mice. Expression of mRNAs encoding the angiogenic cytokines vascular endothelial growth factor (VEGF), angiopoietin 1 (ANGPT1), ANGPT2, platelet-derived growth factor B (PDGF-B), and placental growth factor (PLGF) was also impaired in wounds of older db/db mice. Intradermal injection of plasmid gWIZ-CA5, which encodes a constitutively active form of HIF-1alpha, followed by electroporation, induced increased levels of HIF-1alpha mRNA at the injection site on day 3 and increased levels of VEGF, PLGF, PDGF-B, and ANGPT2 mRNA on day 7. CACs in peripheral blood increased 10-fold in mice treated with gWIZ-CA5. Wound closure was significantly accelerated in db/db mice treated with gWIZ-CA5 as compared to mice treated with empty vector. Thus, HIF-1alpha gene therapy corrects the age-dependent impairment of HIF-1alpha expression, angiogenic cytokine expression, and CACs that contribute to the age-dependent impairment of wound healing in db/db mice.