PB2195 ASSESSMENT OF PLATELET MEMBRANE ALTERATION IN PATIENTS WITH MYELOID METAPLASIA WITH MYELOFIBROSIS
Authors: V. Popov, C. O. Matei, B. M. Matei, R. Leu, I. Dumitru, C. Dobrea, A. Trifa, A. Iova, M. Begu, M. G. Moisescu, T. Savopol, E. Kovacs, A. M. Vladareanu, M. Omer, M. Andreescu, O. Patrinoiu, D. Georgescu, H. Bumbea
Journal: HemaSphere (2019)

Background: Patients with Myeloid Metaplasia with Myelofibrosis (MMM) present at the onset or during evolution thrombotic complications. In the assessment of thrombosis risk are important the presence of JAK2 mutation as well as platelet function. Receptors that define the status of activated platelets (CD62P, CD36) are better expressed in chronic myeloproliferative neoplasms (MPNs) patients with thrombotic complications. Numerous studies have shown a high oxidative status in MPNs patients, a situation that correlates with a higher thrombotic risk. Aims: The aim of our study was to determine if resting membrane potential could be correlated with alterations in expression of platelet receptors and reactive species production (ROS) Methods This retrospective study included 35 patients with MMM (16 male and 19 female), median age 61.1 (95% CI of median 60,71‐72) as well as 15 healthy volunteers. The diagnosis of MMM was made according to World Health Organization (WHO) classification of MPNs. We evaluated the flow cytometry markers of platelet adhesion (CD42a, CD42b), aggregation (CD41, CD61) and CD36. Production of reactive species (ROS) was examined using fluorescence method with DCFDA and was assessed by aria under curve (AUC) in serial measurements during 900 sec. The determination of platelet membrane potential was done by fluorescence method using 3,3′‐dipropyl‐2,2′‐thiadicarbocyanine iodide (DiSC3‐5) Results: The ROS production is significantly higher in MMM group: median value of AUC patient group 12780882862,5000 compared with controls 11621365017,5000, p= 0.04. Patients in advanced phase (grade 5 Hackett of splenomegaly) has high level of ROS production compared with patients diagnosed in early stage (grade 1 or 2 Hackett of splenomegaly) median value: 13178014970 vs 12303298585, p = 0.001. There are no differences between groups that was splitted by type of treatment Ruxolitinib/Hydroxiureea or type of mutation diagnosed JAK2V617F/CALR/no mutation. Patients with MMM present higher resting membrane potential (RMP) compared with controls (median value ‐ 63 mV vs–57.5 mV, p = 0.05). The expression of CD36 receptor was higher in MMM group vs controls: median value 27.91 vs 20.91, p = 0.003. Number of microparticle (MP) derivated from platelet, erythrocyte and endothelial cells are no different between patient and control group. We obtain only lower receptor expression on MP surface for CD41/CD61, CD42b and GlyA in patient group compared with control group, p &lt; 0.05. There are significant correlation between resting membrane potential and expression of CD42b (r ‐0.45, p = 0.04) and GlyA receptors (r ‐0.45, p = 0.04). Summary/Conclusion: Patients with MMM especially those with have a higher level of ROS production especially in advanced phase. The hyperpolarisation of cell macrophages membrane could be associated with high ROS production, no reports are regarding platelet membrane. In our study we did not obtain any significant correlation between RMP and ROS production. The expression of CD 36 is higher in MMM patients but was not correlated with ROS production. It was proved that generation of intracellular ROS is associated with CD36 signaling and represent one start point for thrombosis. Low expression of CD42b and GlyA of microparticle surface is associated with lower RMP that correspond to activated status of platelet membrane. We have to verify these results in higher number of patients in order to find significant correlations