p63 expression during normal cutaneous wound healing in humans

p63, a recently identified member of the p53 family, was shown to play a role in morphogenesis and, probably, in tumors of keratinocyte origin. Because p63 seems to be a marker of keratinocytes with a high proliferative potential, the expression of this protein was studied along with another marker of cell proliferation, Ki67, during normal epidermal regeneration in humans. Serial biopsies of human skin healing by a secondary intention were taken at various time intervals (between days 2 and 21 after the injury) and were studied immunohistochemically with the use of a 4A4 monoclonal antibody against the DeltaNp63 variant and MM1 monoclonal antibody against the Ki67 antigen. In the normal and injured skin, the expression of the DeltaNp63 protein was restricted to the epidermal keratinocytes and hair follicle keratinocytes. In the first days of the healing process, there was a dramatic down-regulation of both DeltaNp63 and Ki67 expression in the area of the epidermal tongue invading under the crust. Five days after the injury, induction of DeltaNp63 in the basal keratinocytes could be detected, followed by a gradual increase of its expression in subsequent days. Several days after complete wound closure, DeltaNp63 was still strongly expressed not only in the basal keratinocytes but also in the entire spinous layer, whereas the Ki67 expression was restricted to single cells in the basal layer. The results indicate that DeltaNp63 could be involved in the control of physiologic processes, such as cell proliferation and migration, related to epidermal repair during healing of normal skin in humans.