PO-19 - Platelet (PLT) adhesion under flow condition in essential thrombocythemia (ET) and polycythemia vera (PV) is variably influenced according to patient mutational status

Introduction The myeloproliferative neoplasms ET and PV are characterized by a high incidence of both arterial and venous thrombosis, and/or microcirculatory disturbances. Three somatic mutations, i.e. JAK2-V617F, Calreticulin (CalR) and MPL, commonly found in these diseases, correlate with different thrombotic risk levels. Aim To analyze the influence of JAK2-V617F, CalR and MPL mutations on PLT adhesion, evaluated by a dynamic method under flow conditions in a group of patients with ET and PV. Materials and Methods 86 patients, i.e. 51 ET (19 M/32 F; age range 32-86 years) and 35 PV (22 M/13 F; 41-83 yrs.), and 24 healthy controls (13 M/11 F; 28-61 yrs.) were enrolled upon informed consent. For the adhesion assay, peripheral venous whole blood was perfused over collagen for 4’ at a 1,000 s-1 shear rate. PLTs were then stained with an anti-P-selectin-FITC antibody to evaluate PLT activation, and annexin V-AlexaFluor647 to detect procoagulant phosphatidylserine expression. Then, images of adherent PLTs in random fields were taken using phase contrast and fluorescence imaging by EVOS® fluorescence microscope. Results are mean ± SEM of the % area covered by PLTs, or as the % of adherent PLTs positive for P-selectin or phosphatidylserine. Main hematological parameters and mutational status were recorded. Results PLT adhesion was significantly (p  Conclusions ET and PV platelets show an increased adhesion to collagen in vitro, particularly in those carrying the JAK2-V617F mutation. A prospective study is ongoing to evaluate the predictive value of our PLT thrombus formation dynamic model for the thrombotic risk in ET and PV patients. Acknowledgement Project funded by “AIRC-IG2013” grant Nr. 14505 from the “Italian Association for Cancer Research” (A.I.R.C.).