PRESERVATION OF HUMAN SKIN-STRUCTURE AND FUNCTION IN ORGAN-CULTURE

Human keratinocytes can be maintained in monolayer culture under serum -free conditions for an extended period of time. Under low Ca2+ condit ions (e.g., 0.05-0.15 mM), an undifferentiated state is maintained and the cells proliferate optimally. When the Ca2+ concentration is raise d to approximately 1.0 mM, differentiation occurs and growth slows. Hu man dermal fibroblasts can also be maintained in monolayer culture und er serum-free conditions, but in contrast to keratinocytes, a physiolo gical level of extracellular Ca2+ (above approximately 1.0 mM) is requ ired. A variety of growth factors stimulate proliferation of both cell types but do not replace the Ca requirement of the fibroblast populat ion. All-trans retinoic acid also promotes proliferation of both cell types and, most interestingly, replaces the requirement for a physiolo gical level of Ca2+ in the fibroblast cultures. Human skin can be main tained in organ culture for an extended period of time under serum-fre e conditions. Conditions optimized for fibroblast proliferation (eithe r physiological Ca2+ or all-trans retinoic acid) are required. In the presence of culture conditions optimized for the epithelial cell compo nent, both the epidermis and dermis rapidly lyse. These data suggest t hat the fibroblast is the critical component in maintaining homeostasi s of skin, and that maintenance of the epidermis as well as the dermis depends on the viability and functioning of these cells.