Background: The GPVI-pathway has previously been reported to be involved in procoagulant platelet activity via GPVI-collagen binding. More recently, newly discovered fibrin-GPVI interactions have been reported to play a role in thrombosis. Nevertheless, the impact of GPVI-fibrin interaction on the development of procoagulant platelets, and how interfering with this interaction alters clot structure, remains to be established.

Aims: Our study aims were to investigate the role of GPVI-fibrin interaction on the development of procoagulant platelet and, subsequently, to characterize the effects of modulating GPVI-fibrin interaction on clot structure.

Methods: Procoagulant platelets were analysed in platelet-rich plasma (PRP) clots by SEM (wild-type and GPVI-deficient samples) and confocal microscopy. Procoagulant platelets were determined, and clot structure analysis assessing clot density, porosity, and retraction was performed in PRP or whole-blood clots from healthy volunteers in the presence of tyrosine kinase inhibitors (PRT-060318, ibrutinib and dasatinib), Affimer proteins inhibiting GPVI-fibrin(ogen) interaction, and eptifibatide control.

Results: In the presence of fibrin (and absence of collagen), GPVI-deficient clots, and clots where GPVI-fibrin(ogen) interaction or GPVI-signalling pathway were inhibited (by Affimer and tyrosine kinase inhibitors, respectively) showed fewer procoagulant platelets and decreased fibrin fibre density. Clot porosity was increased in the presence of all inhibitors, however, final clot weight following whole-blood clot retraction was altered only by ibrutinib. The effects of tyrosine kinase inhibitors on procoagulant platelet number were exacerbated by eptifibatide, which also significantly impaired whole-blood clot retraction.

Conclusion(s): Our results show that interaction of GPVI with fibrin plays a role in the development of procoagulant platelets and indicate that modulating this interaction has downstream effects on clot structure. Our findings suggest that targeting GPVI-fibrin interaction may alleviate structural characteristics commonly associated with a pro-thrombotic phenotype and, thereby, have important implications in development of novel anti-thrombotic interventions.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/increased-platelet-procoagulant-activity-driven-by-fibrin-gpvi-interaction-alters-clot-structure/