Age‐dependent impairment of HIF‐1α expression in diabetic mice: Correction with electroporation‐facilitated gene therapy increases wound healing, angiogenesis, and circulating angiogenic cells

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 1α (HIF‐1α) as well as its downstream target genes; and (b) could be overcome by HIF‐1α 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‐1α gene therapy. HIF‐1α 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‐1α, followed by electroporation, induced increased levels of HIF‐1α 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‐1α gene therapy corrects the age‐dependent impairment of HIF‐1α expression, angiogenic cytokine expression, and CACs that contribute to the age‐dependent impairment of wound healing in db/db mice. J. Cell. Physiol. 217: 319–327, 2008.