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

A model of human skin has been developed in vitro using epidermal keratinocytes, dermal fibroblasts, and type I collagen as starting materials. The bilayered model (Testskin, LSE) consists of a contracted collagen lattice populated with dermal fibroblasts overlaid with keratinocytes that form a multilayered epidermis at the air-liquid interface. Structural, kinetic, biochemical, and functional data suggest that during cultivation the construct undergoes a gradual transition from a ''culture'' phenotype to an organotypic phenotype marked by changes in keratin content, cell kinetics, corneocyte shape and size, lipid biosynthesis, morphologic organization, and function. Timing of this transition 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 stratum corneum and continuous basement membrane. Analysis indicates that the organotypic culture is most characteristic of a newly healed wound. A better understanding of the factors influencing the transition to the organotypic phenotype should help us achieve even further development of the skin construct in the future.