Development of human fetal skin transplanted to the nude mouse.

Thirty-five human fetal skin (HFS) grafts were transplanted to nude mice for 7 to 70 d and evaluated histologically with 64 biopsies. The estimated gestational ages (EGA) of the grafts at the time of the transplantation ranged from 8 to 19 weeks. The maturation of the engrafted fetal skin was evaluated by assessing epidermal, dermal, and appendage development. Within the nude mouse, the HFS demonstrated progression in stratification and maturation of the epidermis. The dermis increased in depth, adding fibrovascular stroma and adipose tissue. The appendages demonstrated invagination, differentiation, and progression of organogenesis. Subcutaneously placed grafts showed the same rate of HFS development as HFS in utero. The grafts transplanted to the surface of the nude mice and exposed to air demonstrated an acceleration of development. We conclude that HFS transplanted to the nude mouse is an effective in vivo model for maintaining and altering HFS maturation.