Cellular source of collagenase and TIMP-1 in carrageenin-induced granuloma

We have examined the occurrence and cellular localization of interstitial collagenase and TIMP-1 mRNAs in a model of granuloma induced by carrageenin in guinea pigs. Granulomas were studied at 4, 7, 10, and 14 days after carrageenin injury using a combined protocol for in situ hybridization and immunofluorescence. Anti-vimentin monoclonal antibody was used to identify fibroblasts. Avidin-FITC and Texas red horse antimouse IgG were employed for detection of probes and antibody, respectively. Our results showed that during the extracellular matrix deposit phase (4 and 7 days), interstitial collagenase and TIMP-1 mRNAs were expressed only by fibroblasts as demonstrated by the colocalization of mRNA and vimentin. By contrast, during the initiation of the resorptive phase (10 and 14 days), fibroblasts and vimentin-negative cells, probably macrophages, expressed collagenase and TIMP-1. This study suggests that fibroblasts are the cell type expressing interstitial collagenase and TIMP-1 mRNA during all phases of the evolution of carrageenin granuloma and that macrophages, by contrast, express the mRNA for the enzyme and the inhibitor exclusively in the degradative phase.