Biology of human skin transplanted to the nude mouse: I. Response to agents which modify epidermal proliferation.

To accept human skin transplanted to the congenitally athymic (nude) mouse as a system to study human skin and its physiologic and pathologic states, it must be demonstrated that skin so maintained retains its function as a biologic unit. We have found that responses of grafted human skin and nude mouse skin to various agents differ. This difference in response has been utilized to assess barrier function and proliferative capacity of human skin grafts. Human skin grafts undergo a proliferative response when 10 ng of the tumor promoter, 12-O-tetradecanoyl phorbol 13-acetate (TPA) is applied. Nudes do not respond to this dose. Increasing the dose to 100 ng of TPA evokes a response in both. However, only in the human skin grafts can this response be blocked with betamethasone valerate (BV). In that human skin grafts do not take on their hosts' responsiveness, and the response of domestic pig skin to these agents before and after grafting is identical, the conclusion is reached that human skin appears to retain its inherent biologic unit function. The data also demonstrate some of the potential of this system to study kinetics of the epidermis of human skin.