Stimulation of PAR-1 or PAR-4 promotes a similar pattern of platelet-mediated angiogenesis

J ETULAIN; HA MENA; S NEGROTTO; M SCHATTNER

Toronto

Congreso; ISTH 2015: International Congress of Thrombosis and Haemostasis. ISTH; 2015

The International Society on Thrombosis and Haemostasis (ISTH)

Background: Platelets mediate vessel formation though the secretion of angiogenic-modulating factors from α-granules, including the pro-angiogenic vascular endothelial growth factor (VEGF) and the anti-angiogenic endostatin. Initial findings indicated that these molecules are packed into different α-granules and that they are selectively released by the specific stimulation of protease-activated receptor (PAR)-1 or PAR-4 using either platelet rich plasma (PRP) or washed platelets (WPs). In contrast, recent evidences are against this hypothesis. Aims: To clarify these controversies, here we evaluated the release of VEGF and endostatin from WPs and PRP activated with PAR-1 activated peptide (AP) or PAR-4-AP and determined the angiogenic effect of platelet-releasates. Methods: The levels of VEGF and endostatin (ELISA) and endothelial proliferation (enzymatic activity), wound healing (microscopy) and tubule formation (microscopy) were determined using supernatants from PAR-1- or PAR-4-stimulated platelets. Results: We found that due to the high levels of plasmatic endostatin vs platelet-lysates content (83±5 vs 2.5±0.3ng/ml), the release of endostatin induced by PARs activation was not detected using PRP. In contrast, PAR-1 or PAR-4 platelet activation resulted in a significant release of VEGF (10±2 and 11±2ng/ml vs resting platelets p