Related Experiment Video
Updated: Jun 5, 2026
Investigating von Willebrand Factor Pathophysiology Using a Flow Chamber Model of von Willebrand Factor-platelet String Formation
Published on: August 14, 2017
GPIbα-vWF rolling under shear stress shows differences between type 2B and 2M von Willebrand disease
L A Coburn1, V S Damaraju, S Dozic
1Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University School of Medicine, Atlanta, USA.
Abstract:
Both type 2B and type 2M von Willebrand disease result in bleeding disorders; however, whereas type 2B has increased binding affinity between platelet glycoprotein Ibα and von Willebrand factor (vWF), type 2M has decreased binding affinity between these two molecules. We used R687E type 2B and G561S type 2M vWF-A1 mutations to study binding between flowing platelets and insolubilized vWF mutants. We measured rolling velocities, mean stop times, and mean go times at 37°C using high-speed video microscopy. The rolling velocities for wt-wt interactions first decrease, reach a minimum, and then increase with increasing shear stress, indicating a catch-slip transition. By changing the viscosity, we were able to quantify the effects of force versus shear rate for rolling velocities and mean stop times. Platelet interactions with loss-of-function vWF-A1 retain the catch-slip bond transition seen in wt-wt interactions, but at a higher shear stress compared with the wt-wt transition. The mean stop time for all vWF-A1 molecules reveals catch-slip transitions at different shear stresses (gain-of-function vWF-A1 < wt vWF-A1< loss-of-function vWF-A1). The shift in the catch-slip transition may indicate changes in how the different mutants become conformationally active, indicating different mechanisms leading to similar bleeding characteristics.
Insights
Type 2B and 2M von Willebrand disease cause bleeding disorders. This study reveals how different von Willebrand factor (vWF) mutations affect platelet interactions and binding dynamics, offering insights into disease mechanisms.
Area of Science:
- Biophysics
- Hematology
- Molecular Biology
Background:
- Von Willebrand disease (vWD) encompasses bleeding disorders stemming from von Willebrand factor (vWF) dysfunction.
- Type 2B vWD involves increased vWF binding affinity, while Type 2M vWD features decreased affinity between vWF and platelet glycoprotein Ibα.
Purpose of the Study:
- To investigate the binding dynamics between flowing platelets and immobilized vWF mutants (R687E type 2B and G561S type 2M).
- To elucidate the relationship between shear stress, force, and platelet-vWF interactions in different vWF mutation types.
Main Methods:
- Utilized high-speed video microscopy to measure rolling velocities, mean stop times, and mean go times at 37°C.
- Manipulated fluid viscosity to differentiate the effects of force versus shear rate on platelet-vWF interactions.
- Studied interactions with wild-type (wt) and mutant vWF-A1 domains.
Main Results:
- Wild-type vWF-A1 interactions exhibit a catch-slip bond transition, where rolling velocity initially decreases then increases with shear stress.
- Platelet interactions with loss-of-function vWF-A1 mutants also show catch-slip transitions, but at higher shear stresses.
- Mean stop times across vWF-A1 variants demonstrate catch-slip transitions at varying shear stresses, ordered as gain-of-function < wt < loss-of-function.
Conclusions:
- The observed catch-slip transitions in platelet-vWF interactions are modulated by vWF mutations.
- Shifts in catch-slip transition points suggest distinct conformational changes in vWF mutants, leading to varied binding behaviors.
- These findings provide insights into the molecular mechanisms underlying different types of von Willebrand disease.
