Vascular endothelial growth factor binds to fibrinogen and fibrin and stimulates endothelial cell proliferation

Vascular development and response to injury are regulated by several cytokines and growth factors including the members of the fibroblast growth factor and vascular endothelial cell growth factor (VEGF) families. Fibrinogen and fibrin are also important in these processes and affect many endothelial cell properties. Possible specific interactions between VEGF and fibrinogen that could play a role in coordinating vascular responses to injury are investigated. Binding studies using the 165 amino acid form of VEGF immobilized on Sepharose beads and soluble iodine 125 ((125)I)-labeled fibrinogen demonstrated saturable and specific binding. Scatchard analysis indicated 2 classes of binding sites with dissociation constants (K(d)s) of 5.9 and 462 nmol/L. The maximum molar binding ratio of VEGF:fibrinogen was 3.8:1. Further studies characterized binding to fibrin using (125)I-labeled VEGF- and Sepharose-immobilized fibrin monomer. These also demonstrated specific and saturable binding with 2 classes of sites having K(d)s of 0.13 and 97 nmol/L and a molar binding ratio of 3.6:1. Binding to polymerized fibrin demonstrated one binding site with a K(d) of 9.3 nmol/L. Binding of VEGF to fibrin(ogen) was independent of FGF-2, indicating that there are distinct binding sites for each angiogenic peptide. VEGF bound to soluble fibrinogen in medium and to surface immobilized fibrinogen or fibrin retained its capacity to support endothelial cell proliferation. VEGF binds specifically and saturably to fibrinogen and fibrin with high affinity, and this may affect the localization and activity of VEGF at sites of tissue injury. (Blood. 2000;96:3772-3778)