The living skin equivalent: Its manufacture, its organotypic properties and its responses to irritants.

A living skin equivalent that resembles human skin has been manufactured as a quality controlled product and commercialized. The skin equivalent consists of a dermal equivalent, reconstituted with collagen and dermal fibroblasts that are biosynthetically active, and a differentiated epidermis that arises from cultured keratinocytes plated onto the surface of the dermal equivalent. The organotypic system is configured so that the dermis is in contact with a nutrient pool while the stratum corneum of the epidermis is exposed to the atmosphere and is thereby accessible for the application of test substances in liquid, gel, emulsion, salve, powder or other forms. The stratum corneum of the living skin equivalent possesses a partial barrier function compared with that of skin. For example, the permeability constant (K(p)) for tritiated water is approximately 20-fold higher than that of skin. The living skin equivalent also lends itself to the study of radiation effects. The dermal equivalent has been used to assess the efficacy of sunscreens applied directly upon it, and a good correlation between sun protection factor values and the degree of protection afforded to the living dermal equivalent has been demonstrated. The present report provides evidence that threshold doses for damage caused by various substances to living skin equivalent are similar to those for damage to skin.