Summary
The large glycoprotein vonWillebrand factor (VWF) is involved in the initial haemostatic
reaction mediating the interaction between platelets and the injured vessel wall.
It has been demonstrated that unusually large VWF (ULVWF) multimers after being released
from endothelium are capable of developing elongated membrane-anchored strings that
are hyperactive to bind platelets. In the present study we investigated whether soluble
plasma-derived VWF is competent to develop similar thrombotically active multimers.
We demonstrated that soluble VWF multimers isolated from human plasma self-assemble
to a network of fibers immobilized on a collagen matrix and are functionally active
to bind platelets. Formation of these VWF fibers depends on shear flow, concentration
of solubleVWF, and a suitable binding surface. Self-assembly of soluble VWF does not
require the presence of cellular membrane ligands. The network of fibers is subjected
to rapid degradation by proteolytic activity of plasma ADAMTS-13.Atomic force microscopy
images elucidate the nanostructure of VWF fibers and illustrate self-association and
-aggregation of several filamentous multimers. Together, these results suggest that
circulatingVWF can contribute to a formation of hyperactive VWF fibers on exposed
subendothelial collagen during vascular injury.
Keywords
ULVWF multimers - platelet adhesion - atomic force microscopy - soluble VWF