Fibroblast-keratinocyte co-cultures in vitro: growth, morphometry and nutrient exchange

The interaction between fibroblasts and rat keratinocytes co-cultured in vitro was examined. The epidermal cells cultured with a basal medium or with a conditioning medium (derived from fibroblast cultures) presented a lower growth rate and significantly greater cellular dimensions than those cells grown in the presence of a feeder layer. Qualitative and quantitative differences in the keratin patterns of the cells grown in the three cultural conditions were found. Keratinocytes cultured with the feeder layer expressed seven keratin types (58, 57, 53, 52, 50, 48 and 45 kDa), those with conditioning medium, five types (58, 53, 52, 48 and 45 kDa) and those with basal medium, only one type (45 kDa). This data confirms the dependence of keratinocytes on fibroblasts. HPLC analysis of the culture media, suggested that a protein factor (MW approximately 65 kDa) was secreted by fibroblasts into the culture medium. This factor was added to the keratinocyte culture medium (conditioning medium), and, after a 48 hour culture, was apparently completely removed from the medium by the keratinocytes. Moreover, the keratinocytes cultured with the feeder layer and exposed to indomethacin, a cyclo-oxygenase inhibitor, showed a decrease in growth rate at drug concentrations of < or = 10 microM which did not induce a reduction in the viability of the fibroblasts and keratinocytes in separate cultures. This preliminary data suggests a relationship between fibroblast PGE2 secretion and keratinocyte growth.