Fibrinogen and fibrin protect fibroblast growth factor-2 from proteolytic degradation

have recently reported that fibrinogen and fibrin bind to fibroblast growth factor-2 (FGF-2) and potentiate its ability to stimulate proliferation of endothelial cells. In the present report, we have investigated the potentia l of fibrinogen and fibrin to protect FGF-2 from proteolytic degradation. F GF-2 was incubated with trypsin or chymotrypsin in the presence or absence of fibrinogen or fibrin and proteolysis of FGF2 was assessed by sodium dode cyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blott ing. In the absence of fibrinogen there was progressive tryptic degradation of FGF-2, but in the presence of fibrinogen, FGF-2 was completely protecte d from trypsin with no evidence of degradation. The degree of protection wa s maximum at a molar ratio of FGF-2 to fibrinogen 1:2. Fibrinogen afforded similar protection from degradation by chymotrypsin. Polymerized fibrin pro vided partial protection of FGF2 from tryptic degradation, with intact FGF2 present for up to 360 min. Fibrin provided nearly complete protection from chymotrypsin. These observations indicate that binding of FGF-2 to fibrino gen or fibrin provides protection from proteolytic degradation, and this ma y modulate its cell proliferative activity.