Fibroblasts in isogeneic skin equivalents persist for long periods after grafting.

We have fabricated skin equivalents by combining fibroblasts from female Fischer rats with collagen to form a lattice and overlaying the lattice with a suspension of epidermal cells. The epidermal cells attach and form a sheet which differentiates. These skin equivalents were then grafted to male Fischer rats in order to follow the fate of the fibroblasts after implantation. Biopsies of the skin equivalent were taken between 9 days and 13 months after grafting and examined histologically or placed in tissue culture to permit karyotyping of the resident fibroblasts. Approximately 82% of the fibroblasts from the graft biopsied at 9 days were female, with this proportion decreasing sharply to 50% at 2 weeks and 60-64% at 1 month. At 1 month, this initial sharp drop is followed by a slow, linear decline which continues through the 13th month when 42% of the fibroblasts are female. We conclude that fibroblasts of the grafted skin equivalent become permanent residents of the skin of the host rat.