SKIN IN COMPLEX CULTURE - THE TRANSITION FROM CULTURE PHENOTYPE TO ORGANOTYPIC PHENOTYPE

A model of human skin has been developed in vitro using epidermal kera tinocytes, dermal fibroblasts, and type I collagen as starting materia ls. The bilayered model (Testskin, LSE) consists of a contracted colla gen lattice populated with dermal fibroblasts overlaid with keratinocy tes that form a multilayered epidermis at the air-liquid interface. St ructural, kinetic, biochemical, and functional data suggest that durin g cultivation the construct undergoes a gradual transition from a ''cu lture'' phenotype to an organotypic phenotype marked by changes in ker atin content, cell kinetics, corneocyte shape and size, lipid biosynth esis, morphologic organization, and function. Timing of this transitio n and final functional characteristics can be manipulated somewhat by culture conditions. Metabolism and biological response are similar to in vivo response at this stage. However, the organotypic culture is as yet not completely developed with respect to a fully functional strat um corneum and continuous basement membrane. Analysis indicates that t he organotypic culture is most characteristic of a newly healed wound. A better understanding of the factors influencing the transition to t he organotypic phenotype should help us achieve even further developme nt of the skin construct in the future.