Clusterin maintains hemostatic equilibrium by stabilizing VWF multimers in plasma

The coagulation-anticoagulation balance is tightly regulated by endothelial-derived factors, which have not been clearly defined. Here, we report that clusterin, a component of Weibel-Palade bodies (WPBs), plays a crucial role in maintaining hemostatic equilibrium by sta bilizing von Willebrand factor (VWF) multimers in plasma. Clusterin was identified by proteomic analysis as a component of endothelial secretome under both chemical and physical conditions and demonstrated as a WPB component via immunostaining and co-transfection assays. Notably, a significant reduction of clusterin protein level was observed in type 2A von Willebrand disease (VWD) patient plasma. Furthermore, loss of clusterin in mice led to hemorrhagic diathesis and impaired thrombosis, accompanied by reduced high molecular weight (HMW) VWF levels. These defects were rescued by exogenous clusterin administration, underscoring its therapeutic potential. Mechanistically, clusterin binds to the D4N domain of VWF, which competitively inhibits ADAMTS13-mediated proteolysis under shear stress, and thereby preserves HMW VWF multimers essential for hemostasis. This study redefines WPBs as hubs for regulatory proteins and establishes clusterin as a key modulator of VWF multimer quality, offering a paradigm shift in targeting coagulation dysfunction through multimer stabilization rather than protein replacement. Our findings bridge a critical gap in understanding endothelial-driven coagulation homeostasis and suggest a potential therapeutic strategy targeting VWF multimer quality for bleeding disorder diseases.