vWFAdhäsion

vWFAdhäsion refers to the adhesive function of von Willebrand factor (vWF) in hemostasis, coordinating the initial steps of platelet plug formation by mediating adhesion to exposed subendothelial structures and to platelets. It is essential for tethering platelets to sites of vascular injury and for stabilizing platelet interactions under high shear conditions.

vWF is produced by endothelial cells and megakaryocytes and released into the bloodstream as multimeric glycoproteins. The molecule contains distinct binding domains: the A3 domain binds to collagen in the subendothelial matrix, while the A1 domain binds to the platelet receptor complex GPIb-IX-V. The adhesive activity is size-dependent; high-molecular-weight and ultra-large multimers display greater platelet-binding capacity. Under shear stress, vWF unfolds, exposing the A1 domain and promoting efficient platelet capture.

Endothelial activation or injury triggers the release of vWF from Weibel-Palade bodies (and from platelet alpha granules). In flowing blood, ultra-large vWF multimers can rapidly recruit platelets to sites of injury, forming the initial platelet plug. This adhesion often precedes platelet activation and subsequent aggregation via integrin pathways, including activation of GPIIb/IIIa and binding of fibrinogen.

Regulation of vWF adhesion involves proteolysis by ADAMTS13, which cleaves ultra-large multimers into smaller, less adhesive forms. Deficiency of ADAMTS13 or qualitative defects in vWF lead to related bleeding disorders, most notably von Willebrand disease (vWD). Conversely, excessive vWF activity can contribute to pathologic thrombosis.

In summary, vWFAdhäsion describes the mechanism by which von Willebrand factor mediates platelet adhesion to damaged vessel walls and to subendothelial collagen, a critical step in primary hemostasis influenced by shear forces, multimer size, and regulatory proteolysis.