Fibrillar cellular fibronectin supports efficient platelet aggregation and procoagulant activity

Area of Science:

• Biomedical research
• Hematology
• Vascular biology

Background:

• The role of fibrillar cellular fibronectin in the vessel wall in regulating platelet function and thrombus formation is not well understood.
• Cellular fibronectin exists in a fibrillar conformation within the vessel wall, suggesting a potential role in hemostasis and thrombosis.

Purpose of the Study:

• To investigate how parietal cellular fibronectin, in a fibrillar form, modulates platelet responses under physiological flow conditions.
• To identify the specific platelet receptors involved in adhesion, activation, and thrombus growth on fibrillar cellular fibronectin.

Main Methods:

• A fibrillar network of cellular fibronectin was created by mechanically stretching immobilized dimeric fibronectin.
• Anticoagulated whole blood was perfused over the fibrillar fibronectin surface to assess platelet adhesion and thrombus development.
• Platelet activation markers (filopodia extension, intracellular calcium) and receptor involvement were analyzed.

Main Results:

• Fibrillar cellular fibronectin supported efficient platelet adhesion and thrombus growth under flow.
• Initial platelet adhesion and activation depended on integrins α5β1 and αIIbβ3.
• Thrombus progression involved integrins α5β1, αIIbβ3, GPIb-V-IX complex, GPVI, and Toll-like receptor 4, with the latter potentially binding to the fibronectin EDA region.
• Platelets within the thrombus exhibited procoagulant activity and generated fibrin.

Conclusions:

• Fibrillar cellular fibronectin acts as a potent thrombogenic surface.
• Platelet adhesion, activation, aggregation, and procoagulant activity on this surface are mediated by a complex interplay of multiple receptors.
• This finding highlights a novel mechanism in thrombus formation involving cellular fibronectin and specific platelet receptors.