The pivotal role of von Willebrand factor binding to platelet αIIbβ3 in stabilizing the formation of a platelet plug at sites of injury

The interaction between von Willebrand factor (VWF) and platelet αIIbβ3 is thought to be essential for clot formation at injury sites, but its biological properties remain poorly understood due to the complexity and overlap with other αIIbβ3 ligands. Here, we developed a novel binding assay using a recombinant αIIbβ3 headpiece to evaluate VWF-αIIbβ3 binding in plasma from 441 Zimmerman Program participants. The VWF:αIIbβ3 to VWF:Ag ratio was significantly lower in patients with type-1, 2A, and 2B VWD than healthy controls. We identified five index cases with the p.R2464C variant in the VWF-C-domain, where affected family members displayed significantly reduced VWF:αIIbβ3/VWF:Ag ratios. To investigate the function of the VWF-αIIbβ3 interaction, we created a mouse model (VWFRGES/RGES) by altering the VWF-RGDS motif to RGES, which abolished VWF-αIIbβ3 binding. VWFRGES/RGES mice exhibited increased blood loss following lateral tail vein transection and reduced thrombus stability in a laser injury model, showing a 59-fold larger AUC for emboli compared to wild-type. However, initial bleeding times and outcomes of carotid artery injury were comparable. Overall, our VWF:αIIbβ3 binding assay is valuable for characterizing VWD, and the VWFRGES mouse model underscores the physiological significance of the VWF-αIIbβ3 interaction, highlighting that VWF-αIIbβ3 interaction is crucial for stabilizing platelet plug formation at injury sites.