Behaviour of the von Willebrand Factor in Blood Flow

Abstract

The von Willebrand factor (vWF), a large multimeric protein, is essential in hemostasis. Under normal conditions, vWF is present in blood as a globular polymer. However, in case of an injury, vWF is able to unwrap and bind to the vessel wall and to flowing platelets. Thus, platelets are significantly slowed down and can adhere to the wall and close the lesion. Nevertheless, it is still not clear how the unwrapping of the vWF is triggered. To better understand these complex processes, we employ a particle-based hydrodynamic simulation method to study the behaviour of vWF in blood flow. The vWF is modelled as a chain of beads (monomers) connected by springs. In addition, the monomers are subject to attractive interactions in order to represent characteristic properties of the vWF. The behaviour of vWF is investigated under different conditions including a freely-suspended polymer in shear flow and a polymer attached to a wall. We also examine the migration of vWF to a wall (margination) depending on shear rate and volume fraction of red blood cells (RBCs). Furthermore, the stretching of the vWF in flow direction depending on its radial position in a capillary is monitored. Our results show that attractive interactions between monomer beads increase margination efficiency and significantly affect the extension of vWF at different radial positions in blood vessels.