Pathophysiology of von Willebrand factor in the circulation

• Applicant: Professor Dr. Reinhard Schneppenheim
• Subject Area: Hematology, Oncology ; Biophysics
• Term: from 2011 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 172540668

Von Willebrand factor (VWF) is an adhesive, multi-functional, multimeric protein with multiple domains harboring binding sites for collagen and platelet glycoprotein receptors mediating its role in primary hemostasis. ln secondary hemostasis VWF is important as a transport proteinthat protects coagulation factor VIII (FVIII) from degradation. lts functional domains enable VWF to bind to the injured vessel wall, to recruit platelets to the site of injury by adhesion and aggregation and to bind FVIII. VWF functions in the circulation are shear-dependent and some of them are strictly correlating with its multimer size. ln this project we will focus on two novel aspects of the pathophysiologic relevance of VWF: effects of genetic variations within VWF on collective network formation and VWF's regulatory influence on FVIII half-life.After secretion into the blood stream VWF high molecular weight multimers and platelets form collective networks that facilitate primary hemostasis but can also have pathological prothrombotic effects. Our data indicate that mutations within VWF can have unforeseeable effects on platelet binding and aggregation independent of the mutated domain. Further, we found that genetic variations of VWF influence critical shear rate and tendency for collective network formation. These data underpin the necessity to investigate the shear-dependent function and dysfunction of VWF in detail under shear flow conditions. Firstly, we will investigate the physiological and pathophysiological role of VWF collective networks. Questions we will address employing shear flow assays and cone and plate analysis are: 1) which VWF domains are involved in network formation, 2) how does platelet-VWF contribute to collective network formation 3) what are the patho-mechanisms behind the influence of genetic variations of VWF on platelet aggregation? Secondly, we will investigate VWF as a limiting factor of FVIII half-life. Since FVIII travels the circulation mainly bound to VWF, half-life of the two proteins is directly correlated to clearance and recycling of VWF. To characterize the VWF clearance mechanism we will identify amino acids in the D'-03 assembly critical for VWF clearance, determine differences in wtVWF and mutant VWF internalization and recycling by macrophages, and finally develop strategies to prolong VWF half-life. Long-term goal is to unravel the mechanisms of the shear-dependent pathophysiologic roles of VWF to develop novel strategies with VWF astarget for antithrombotic agents and secondarily as therapeutic option both for patients with Haemophilia A and VWD.

• DFG Programme: Research Units
• Subproject of: FOR 1543: Shear Flow Regulation of Hemostasis - Bridging the Gap between Nanomechanics and Clinical Presentation
• Cooperation Partner: Professor Dr. Ulrich Budde