AB0169 ENHANCED PLATELET ACTIVATION AMONG PATIENTS WITH SYSTEMIC SCLEROSIS

Background: The function of platelets (PLT), which can serve as reservoirs of transforming growth beta, leads to the question whether they are activated in systemic sclerosis (SSc) to such an extent as to associate with clinical severity. Objectives: To compare the level of PLT activation in SSc and to correlate with physical findings Methods: Blood was sampled from 12 patients participating in the randomized clinical trial LIGHT (ClinicalTrials.gov NCT040045743) evaluating the safety and efficacy of bermekimab in SSc. Patients had to meet the 2013 ACR/EULAR classification criteria and have a modified Rodnan skin score (mRSS) between 15 and 40. Sampling was done before allocation to treatment. Nil patient was on DMARDs. Ten healthy donors were used for comparison. Citrated whole blood was exposed to 0.1 mM adenosine diphosphate (ADP) to stimulate PLT. Total platelet populations were defined as CD42b-positive population; P-selectin (CD62p) served as an activation marker. Results: Expression of 42b(+)/62p(+) PLT was greater among patients (Figure 1). Mean fluorescence intensity (MFI) of 42b(+)/62p(+) PLTs was 0.16 +/- 0.08 in comparators and 0.51 +/- 0.07 in patients (p= 0.015). Negative correlation was found between the expression of 42b(+)/62p(+) on PLT and mRSS (r= -0.73, p= 0.028). Patients with grade 2 findings at capillaroscopy had greater expression of 42b(+)/62p(+) than patients with grade 3 findings (45.9 +/- 7.2 % vs 27.2 +/- 6.7 %; p: 0.041). Conclusion: PLTs are greatly activated in SSc and this is associated with disease progression. Findings suggest that this activation is greater at less severe patients. References: [1]Morel A, Rywaniak J, Bijak M, Miller E, Niwald M, Saluk J. Flow cytometric analysis reveals the high levels of platelet activation parameters in circulation of multiple sclerosis patients Mol Cell Biochem. 2017;430:69-80. doi: 10.1007/s11010-017-2955-7 Disclosure of Interests: None declared