Mechanism of Impairment in Wound Healing of Electron Beam‐Irradiated Rat Skin

Abstract

Aim: Preoperative radiotherapy for head and neck or colon cancer frequently prevents the following surgical operation, since effective dose of ionized radiation induces wound complication. To make the operation possible, causes for the impaired wound healing were clarified.Methods: Thighs of F344 rats were irradiated with electron beam (30 Gy). Seven days after the irradiation, full‐thickness skin of the thigh was cut by punch biopsy (4‐mm diameter). Healing process was determined by measuring size of wound opening. Cytokeratin 14, smooth muscle actin (a marker of myofibroblasts), and integrin beta1 were detected by immunohistochemical analyses.Results: The wounds in the nonirradiated rats healed almost completely on day 7, whereas repair of epidermis was impaired in the irradiated skin. Numbers of hair follicles and micro‐vessels decreased, and myofibroblasts were almost missing in the scar and dermis adjacent to the wounds of irradiated skins. Proliferation indexes of epidermal basal cells were much higher in irradiated skins than those in nonirradiated skins, however, these basal cells did not express cytokeratin 14, concomitant with the absence of integrin beta1 in basement membrane of the irradiated epidermis. On the other hand, apoptosis appeared in the dermal follicular cells of hair bulbs, 18 h after the irradiation. On day 3, structures of hair follicles were destructed.Conclusions: Reepithelialization of wounds was blocked in the irradiated skin. Since epidermal basal cells are supplied from stem cells in the hair bulge during cutaneous wound healing, one of causes for the impaired wound healing may be insufficiency of epidermal stem cells.