Influence of plasma fibronectin on collagen cleavage by collagenase

The influence of plasma fibronectin on the cleavage of interstitial collagen types I, II, and III by mammalian collagenase was investigated. To this end, rheumatoid arthritis synovial tissue collagenase was isolated from tissue culture supernatants. A highly active enzyme preparation was obtained. Different dilutions of the collagenase were incubated in tubes coated with [3H]-labeled collagens. Liberation of labeled fragments in the presence (200 micrograms per ml) or absence of fibronectin was measured at different time intervals (1-30 min). A significant inhibition of collagen degradation was observed in case of type I and type III collagens. Analogous experiments were carried out using collagen-coated tubes preincubated with fibronectin at a concentration of 200 micrograms/ml. Here, a strong inhibition (76 percent) of type III collagen digestion by collagenase was observed, while the cleavage of type I or type II collagen was completely unchanged after preincubation with fibronectin. A direct attack of the collagenase preparation on plasma fibronectin could be excluded in control digestion experiments using radioiodinated fibronectin as substrate.