Polymerisation of fibrin αC-domains promotes endothelial cell migration and proliferation

Upon conversion of fibrinogen into fibrin, fibrinogen alpha C-domains containing the RGD recognition motif form ordered alpha C polymers. Our previous study revealed that polymerisation of these domains promotes integrin-dependent adhesion and spreading of endothelial cells, as well as integrin-mediated activation of the FAK and ERK1/2 signalling pathways. The major goal of this study was to test the impact of alpha C-domain polymerisation on endothelial cell migration and proliferation during wound healing, and to clarify the mechanism underlying superior activity of alpha C polymers toward endothelial cells. In an in vitro wound healing assay, confluent endothelial cell monolayers on tissue culture plates coated with the alpha C monomer or alpha C polymers were wounded by scratching and wound closure was monitored by time, lapse videomicroscopy. Although the plates were coated with equal amounts of alpha C species, as confirmed by ELISA, wound closure by the cells. occurred Much faster on alpha C polymers, indicating that alpha C-domain polymerisation promotes cell migration and proliferation. In agreement, endothelial cell proliferation was also more efficient on alpha C polymers, as revealed by cell proliferation assay. Wound closure on both types of substrates was equally inhibited by the integrin-blocking GRGDSP peptide and a specific antagonist of the ERK1/2 signalling pathway. In contrast, blocking the FAK signaling pathway by a specific antagonist decreased wound closure only on alpha C polymers. These results indicate that polymerisation of the alpha C-domains enhances integrin-dependent endothelial cell migration and proliferation mainly through the FAK signalling pathway. Furthermore, clustering of integrin-binding RGD motifs in alpha C polymers is the major mechanism triggering these events.