Identification of a 2-stage platelet aggregation process mediating shear-dependent thrombus formation

Area of Science:

• Cardiovascular Biology
• Hematology
• Biophysics

Background:

• Atherosclerotic plaque rupture causes blood flow disturbances, promoting platelet activation and arterial thrombus formation.
• While in vitro studies explored shear effects on platelets, in vivo mechanisms of shear-induced platelet aggregation remain unclear.

Purpose of the Study:

• To elucidate the in vivo mechanisms of shear-dependent platelet aggregation at sites of atherosclerotic plaque rupture.
• To identify the key factors and cellular processes involved in initiating platelet aggregation under high shear flow.

Main Methods:

• Utilized high-resolution imaging techniques in both in vitro and in vivo thrombosis models.
• Investigated the roles of platelet membrane tethers, adhesive molecules (GPIb/V/IX, integrin alphaIIbbeta3), and released ADP in aggregate formation.

Main Results:

• Demonstrated a novel mechanism of shear-dependent platelet aggregation initiated by discoid platelet aggregate formation.
• Identified membrane tethers between coadhering platelets as critical for initial aggregate stability.
• Showed that released ADP is required for converting unstable discoid aggregates into stable thrombi.

Conclusions:

• Identified a new shear-influenced pathway for platelet aggregation involving membrane tethers and ADP release.
• The process is regulated by adhesive substrate reactivity, shear flow levels, and platelet density.
• Platelet discoid morphology facilitates adhesion to thrombogenic surfaces under high shear stress.