AGING, DIFFERENTIATION AND APOPTOSIS IN HUMAN EPIDERMAL-KERATINOCYTESIN CULTURE

Aging of human epidermal keratinocytes was studied by serial passaging them as a monolayer culture in a serum-free medium containing 0.09 M calcium. Under these conditions the cells were constantly kept in a pr oliferative mode and in an undifferentiated state. Aging characteristi cs in terms of growth and longevity, cumulative population doubling le vel, cell yield, protein content, and alterations in morphology and in macromolecular synthesis were studied. Furthermore, the induction of differentiation by raising the calcium concentration in the growth med ium has facilitated the use of this system to address the issues of th e relationship among aging, differentiation and apoptosis in keratinoc ytes in culture.