CalciumInduced Human Differentiation ofSV 40 Immortalized Epidermal Keratinocytes in a Defined Medium Cultured

Human epidermal keratinocytes, immortalized by the intToduction of SV40-adenovirus recombinants {9). were maintained in a low calcium <e.I5 mM) defined medium. When differentiation was induced by a higher extracellular calcium concentration {I.5 mM), these cells altered in shape and developed stratification with forrnation of desmosornes, while they demons(rated limited terminal keratinization. The expression of involucrin, one of the precursor proteins bf the cbrriified envelope, became elevated as the cell density increased, but was not affected by calcium. These results indicate that the SV40 immortalized human keratinocytes, maintained in a low calcium defined medium, paTtially respend to changes in extracellular calcium concentratibn.