Degradation of basement membrane collagen by proteinases from human gingiva, leukocytes and bacterial plaque.

Basement membranes in human gingiva are found in dento-epithelial junction, epithelial-connective tissue junction and endothelium-connective-tissue junction where they have important attachment and filtering functions. The ability of plaque and gingiva-derived proteinases to degrade Type IV collagen, the major protein of basement membranes, was examined in vitro. The basement membrane collagen (Type IV) isolated from bovine lens capsules was incubated in the presence of enzyme samples. The degradation was assayed by the release of hydroxyproline from the insoluble substrate and by examining the peptide pattern of the residue by polyacrylamide gel electrophoresis. Salt extracts of inflamed gingival specimens degraded basement membrane collagen into soluble form and produced degradation products that were similar to those produced by human leukocyte extracts. Gingival crevicular fluid collected from patients with severe adult periodontitis also digested the substrate but the degradation pattern was different from the leukocyte and gingival extract samples. The pattern closely resembled the degradation produced by bacterial plaque extracts. A third type of cleavage was observed when collagenase from Clostridium histolyticum was incubated with basement membrane collagen. Crevicular fluid and the extracts from gingiva, leukocytes and plaque also contained gelatinase and elastase-like enzyme activities that have earlier been shown to be potent in degrading basement membrane. It was concluded that enzymes capable of degrading basement membrane collagen in gingivitis and periodontal disease may originate from both plaque bacteria and human leukocytes. It also appeared that the enzymes responsible are more likely to be gelatinase and elastase-like enzymes than specific collagenases.