EFFECTS OF FIBRIN ON THE ANGIOGENESIS IN-VITRO OF BOVINE ENDOTHELIAL-CELLS IN COLLAGEN GEL

The effect of fibrin on angiogenesis in vitro was investigated using a n experimental model of tube formation by bovine capillary endothelial cells (BCEs) in type I collagen gel. One milligram per milliliter of fibrin added into type I collagen gel significantly increased the leng th of the tubular structures formed by BCEs in the gel by about 180% c ompared with type I collagen only. The facilitating effect of fibrin o n tube formation by BCEs was inhibited by either anti-basic fibroblast growth factor (bFGF) IgG (25 mu g/ml) or anti-urokinase type plasmino gen activator (uPA) IgG (10 mu g/ml) added to the gel and culture medi um, but not by anti-tissue type plasminogen activator (10 mu g/ml) or non-immune IgG. The Arg-Gly-Asp (RGD) containing peptides (100 mu g/ml ) added to the culture medium also suppressed tube formation by BCEs i n fibrin-containing type I collagen gel, but not in type I collagen ge l. These results suggest that the increased release of bFGF and uPA by BCEs therefore plays a role in the angiogenic effect of fibrin in vit ro, and the angiogenic effect of fibrin is mediated by the RGD sequenc e in fibrin, probably via the function of integrin receptor of the BCE s.