Biological and physical factors influencing the successful engraftment of a cultured human skin substitute.

Skin tissue may be engineered in a variety of ways. Our cultured skin substitute (Graftskin, living skin equivalent or G-LSE), Apligraf, is an organotypic culture of skin, containing both a dermis and epidermis. The epidermis is an important functional component of skin, responsible for biologic wound closure. The epidermis possesses a stratum corneum which develops with time in culture. The stratum corneum provides barrier function properties and gives the LSE improved strength and handling characteristics. Clinical experience indicated that the stratum corneum might play an important role in improving the clinical utility of the LSE. Handling and physical characteristics improved with time in culture. We examined the LSE at different stages of epidermal maturation for barrier function and ability to persist as a graft. LSE grafted onto athymic mice before significant development of barrier function did not withstand bandage removal at 7 days postg raft. LSE grafted after barrier function had been established in vitro were able to withstand bandage removal at day 7. Corneum lipid composition and structure are critical components for barrierfunction. Media modifications were used in an attempt to improve the fatty acid composition of the stratum corneum. The barrier developed more rapidly and was improved in a serum-free, lipid-supplemented condition. Lipid lamellar structure was improved with 10% of the stratum corneum exhibiting broad-narrow-broad lipid lamellar arrangements similar to human skin. Fatty acid metabolism was not appreciably altered. Barrier function in vitro was 4- to 10-fold more permeable than human skin. Epidermal differentiation does not compromise engraftment or the wound healing ability of the epidermis. The stratum corneum provides features beneficial for engraftment and clinical use.