Fibrin monomer and fibrinopeptide B act additively to increase DNA synthesis in smooth muscle cells cultured from human saphenous vein

Purpose: We investigated the hypothesis that fibrinogen increased DNA synth esis (and cell proliferation) of smooth muscle cells (SMCs) cultured from h uman saphenous vein and that the increased DNA synthesis was attenuated whe n cells were cultured on polymeric collagen. Methods: SMCs were cultured from human saphenous vein on plastic, fibronect in, monomeric, and polymeric collagen. Fibrinogen products were prepared by proteolytic digestion. DNA synthesis was measured by bromodeoxyuridine inc orporation into DNA, cell proliferation by cell counting, cyclic adenosine monophosphate by enzyme-linked immunosorbent assay, and fibrinopeptide B la beled with iodine 125 used for binding studies. Results: Fibrin monomer (0.003-0.1 mu mol/L) stimulated a concentration-dep endent increase in DNA synthesis of up to 10-fold, which could be inhibited by the peptide B beta 15-42. The stimulation of DNA synthesis was highest for cells cultured on plastic and lowest for cells cultured on type I colla gen polymer. Much higher concentrations of fibrinogen (0.3-1 mu mol/L) were required to effect similar increases in DNA synthesis. Fibrinogen had a pa rticular effect to augment DNA synthesis, up to 14-fold, when cells were cu ltured on monomeric type I collagen. This augmented DNA synthesis was inhib ited by a neutralizing antibody to urokinase-type plasminogen activator. In cubation of cells cultured on collagen monomer with fibrinogen resulted in production of fibrinopeptide B. Fibrinopeptide B (5 mu mol/L) increased DNA synthesis by fourfold and had additive effects with fibrin monomer to incr ease DNA synthesis. Iodinated tyrosine fibrinopeptide B bound to SMCs (diss ociation constant 0.6 mu mol/L). Conclusion: Cultured human saphenous vein SMCs appear to have high-affinity receptors for fibrin monomer and fibrinopeptide B, the engagement of which stimulates DNA synthesis. These mechanisms may be pertinent to the associa tion between fibrinogen and vein graft stenosis in vivo.