Human skin in organ culture. Elaboration of proteolytic enzymes in the presence and absence of exogenous growth factors.

Proteinase levels were assessed in organ culture fluids from human neonatal foreskin maintained under growth factor-free conditions and in the presence of a combination of growth factors (ie, epidermal growth factor, insulin, hydrocortisone, pituitary extract, and all-trans-retinoic acid). Analysis of culture fluids by gelatin zymography revealed the presence of 92-kd and 72-kd gelatinases. There was a greater amount of 92-kd gelatinase activity in the presence of growth factors whereas the levels of 72-kd gelatinase were similar in growth factor-free and growth factor-containing media. Experiments with keratinocytes and fibroblasts in monolayer culture and with isolated dermal tissue in organ culture indicated that the epithelial component was responsible for most of the 92-kd gelatinase activity whereas fibroblasts were primarily responsible for the 72-kd gelatinase activity. Activation with aminophenyl mercuric acetate, requirement for divalent cations, inhibition with EDTA, and insensitivity to inhibition with phenylmethyl sulfonyl fluoride indicated that both gelatinases were metalloproteinases. In additional studies, culture fluids were examined for the presence of plasminogen activator activity. This was detected in culture fluids from tissues maintained under both conditions but was increased in the growth factor-containing medium. The increased amount seen in the growth factor-containing medium appeared to be due almost entirely to a single factor, ie, all-trans-retinoic acid. In monolayer culture, both keratinocytes and fibroblasts produced plasminogen activator; the level was higher in keratinocyte culture fluids than in culture fluids from fibroblasts.