Metalloproteinases are not involved in the phagocytosis of collagen fibrils by fibroblasts.

The effect of various metalloproteinase-inhibiting compounds on collagen phagocytosis by fibroblasts was studied in cultured periosteal tissue. Evidence is presented indicating that neither anti-collagenase nor anti-stromelysin interfere with the uptake of collagen fibrils from the extracellular space and their intracellular digestion. Similar results were obtained with tissue inhibitor of metalloproteinases (TIMP). In the presence of the proteinase inhibitor leupeptin, a compound which strongly inhibits the intracellular degradation of phagocytosed collagen, a time-dependent increase in the amount of internalized collagen was found. This increase proved to be similar in explants treated as well as in those not treated with the metalloproteinase-inhibiting compounds. It is concluded that enzymes, such as collagenase and stromelysin, do not play a crucial role in the phagocytosis and intracellular digestion of collagen fibrils by fibroblasts. If these enzymes are involved it must be prior to these events. Based on the morphometric data the intralysosomal degradation time of collagen was calculated to be about 30 minutes. A comparison with findings in the literature on collagen metabolism in the periodontal ligament of the rat molar suggests that all collagen degraded may pass through the phagolysome pathway during physiological turnover and remodelling.