ALTERED TRANSCRIPTIONAL REGULATION OF HUMAN INTERSTITIAL COLLAGENASE IN CULTURED SKIN FIBROBLASTS FROM OLDER DONORS

Primary human dermal fibroblasts isolated from the medial aspect of the proximal forearm of young and old donors were compared for the expression of interstitial collagenase, 72 kDa type IV collagenase, the tissue inhibitor of metalloproteinase type 1, and pro-alpha 2 (I) collagen mRNA at basal levels and after stimulation with the tumor promotor 12-O-tetradecanoyl-phorbol-13-acetate. Higher basal and induced steady-state mRNA levels of interstitial collagenase were found in the cells from older donors. Ratios of basal and induced steady-state mRNA levels of interstitial collagenase to pro-alpha 2 (I) collagen, and interstitial collagenase to the tissue inhibitor of metalloproteinases type 1 were also higher in the cells from older donors. Seventy-two kiloDalton type IV collagenase and pro-alpha 2 (I) collagen mRNA showed similar levels of expression in the cells from young and old donors and were not altered by treatment with 12-O-tetradecanoyl-phorbol-13-acetate. Transient transfection assays with the interstitial collagenase promoter linked to a reporter gene showed increased activity of the reporter in cell strains with high interstitial collagenase mRNA levels. Mobility shift assays demonstrated increased binding activity to the specific 12-O-tetradecanoyl-phorbol-13-acetate response element in nuclear extracts from the cell strains with higher induced collagenase mRNA levels and higher reporter gene activity. These findings are consistent with the observed phenotype of interstitial collagenase and its specific tissue inhibitor in the senescent fibroblast aging model.