Immunohistochemical localization of transforming growth factor-B1 in epithelializing human keratinocyte inclusion cysts grown in athymic mice

Human epidermal keratinocytes suspended in a fibrin clot were implanted subcutaneously in athymic nude mice. These keratinocytes organized to form epidermal inclusion cysts. The inclusion cysts were stained immunohistochemically to detect involucrin and TGF-beta. Involucrin is a protein found in human stratified squamous epithelium which can serve as a marker for epidermal regeneration. TGF-beta is a polypeptide which enhances wound healing and has a broad array of other biological effects. Whereas in normal skin only the upper spinous and granular layers of the epidermis stained for involucrin, staining was observed through all cell layers except the outermost in the inclusion cysts. This pattern of staining is typically seen in actively regenerating epidermal tissue. Of particular significance was the observation that the epidermal inclusion cysts stained for the presences of TGF-beta, while the epidermis of normal skin did not. TGF-beta has previously been reported to promote wound healing by stimulating fibroblast proliferation, collagen deposition, and angiogenesis. Our observations suggest that TGF-beta may also play a role in the regulation of epithelialization in vivo.