Improved wound healing in transgenic mice overexpressing heme oxygenase-1 in the skin

Heme oxygenase-1 is a proangiogenic and cytoprotective enzyme, which degrades heme to CO, biliverdin and Fe2+. HO-1 is induced after blood vessel disruption upon injury and plays an important role in tissue repair. Our aim was to clarify a role of local HO-1 overexpression in cutanous wound healing.

Therefore we created transgenic mice overexpressing human HO-1 under the control of keratin 14 promoter. In vitro, the augmented expression of HO-1 accelerated the closure of scratch in a monolayer of primary keratinocytes isolated from transgenic newborns. Transgenic keratinocytes displayed also a slight tendency to increased proliferation (BrdU incorporation assay). Finally, HO-1 overexpression improved viability (MTT assay) of the cells kept for 24 h under hypoxic conditions (1% O2), and slightly increased production of VEGF (ELISA) induced by hypoxia. For in vivo experiments, two full-thickness circular wounds (4 mm in diameter) were generated on dorsal skin of the mice. The mice overexpressing HO-1 in keratinocytes had improved re-epithelialization and vascularization of wounds, whereas in mice deficient of HO-1 restoration of tissue integrity was strongly retarded and vascularization was diminished. Moreover, we observed delayed HO-1 expression and poor vascularization during deregulated wound healing in diabetic (db/db) mice. Finally, we accelerated injury repair and strengthened vascularization of wounds in db/db mice by local overexpression of HO-1 using adenoviral vectors.

To conclude, we demonstrated that tissue-specific upregulation of HO-1 in keratinocytes is enough to accelerate reepithelialization and augment vascularization. These findings provide new potential approaches in tissue repair.