Shear stress and platelet-induced tensile forces regulate ADAMTS13-localization within the platelet thrombus

Area of Science:

• Hematology
• Biophysics
• Molecular Biology

Background:

• Von Willebrand factor (VWF) is a multimeric glycoprotein essential for platelet adhesion and aggregation at vascular injury sites.
• ADAMTS13, a metalloprotease, regulates VWF multimer length, thereby influencing platelet thrombus growth in a shear-dependent manner.
• The precise mechanisms by which ADAMTS13 regulates thrombus formation under shear stress remain incompletely understood.

Purpose of the Study:

• To investigate the mechanistic basis of ADAMTS13's role in regulating platelet thrombus growth under shear stress.
• To visualize ADAMTS13 localization within platelet thrombi and assess the influence of platelet-mediated tensile forces on its activity.

Main Methods:

• Development of an mCherry-tagged murine ADAMTS13 protein for visualization.
• Utilization of an ex vivo flow chamber system to observe ADAMTS13 localization under varying shear conditions.
• Assessment of tensile force effects using VWF/ADAMTS13 DKO mice with modified GPIb and GPIIbIIIa binding functionalities.

Main Results:

• ADAMTS13-mCherry was visualized localizing to the growing platelet thrombus under high shear conditions.
• ADAMTS13 localized predominantly at the thrombus apex, reducing overall thrombus size.
• Platelet-mediated tensile force, specifically involving GPIb receptors, influenced ADAMTS13 localization at pathological shear rates (7500 s⁻¹).

Conclusions:

• Shear stress-induced tensile force on VWF, mediated by platelet GPIb binding, is critical for ADAMTS13 activity during thrombus formation.
• ADAMTS13 activity is regulated by a shear stress and platelet-dependent feedback mechanism.
• This regulatory mechanism plays a vital role in preventing vessel occlusion and pathological thrombosis.