Differential Response of Early and Late Passage Fibroblasts to Collagenase Stimulatory Factor in Conditioned Media

Comparison of the proteins secreted by early and late passage cultures of humanfibroblasts reveals enhanced production of three proteins (M_r = 55,000, 58,000, and 61,000) in the late passage culture conditioned medium. The 55,000 and 58,000 Da proteins react with anticollagenase antibodies and are identified as procollagenase (Sottile, J. M. and Millis, A. J. T., J. Cell Biol. 106: 1518a, 1987). The production of immunoreactive collagenase was assayed using immunoprecipitation and immunofluorescence. Immunofluores cence microscopy revealed that each culture was heterogenous. The percentage of collagenase positive cells ranged from 1% (early passage) to 35% (late passage). Late passage cultures also secreted higher levels of immunoprecipitable collagenase into the culture medium than early passage cultures. High levels of collagenase production were also observed in fibroblasts cultured from donors with Werner's syndrome and from an aged donor. Media conditioned by the growth of human fibroblasts contained collagenase stimulating activity. In the presence of conditioned medium, the percentage of collagenase positive cells was increased to 10–20% (early passage) and 85% (late passage), indicating that each culture contains both responding and non-responding cells.