Microparticles (MPs) could be considered biomarkers of cell damage and activation as well as novel signalling structures. Since rheumatoid arthritis (RA) is characterized by immune and endothelial activation, the main aim of the present study was to analyse MP counts in RA patients. Citrated-blood samples were obtained from 114 RA patients, 33 healthy controls (HC) and 72 individuals with marked cardiovascular (CV) risk without autoimmune manifestations (CVR). MPs were analysed in platelet-poor plasma (PPP) and different subsets were identified by their surface markers: platelet- (CD41+), endothelial- (CD146+), granulocyte- (CD66+), monocyte- (CD14+) and Tang- (CD3+CD31+) derived. Disease activity score (DAS28), clinical and immunological parameters as well as traditional CV risk factors (diabetes, hypertension, dyslipidaemia and obesity) were registered from clinical records and all data were integrated using Principal Component Analysis (PCA). Absolute MP number was increased in RA patients compared with HC and positively correlated with traditional CV risk factors, similar to that of CVR subjects. In addition, frequency of the different MP subsets was different in RA patients and significantly associated with disease features. Moreover, in vitro assays revealed that MPs isolated from RA patients were able to promote endothelial activation and exhibited detrimental effects on human microvascular endothelial cells (HMEC-I) endothelial cell functionality. Circulating MPs from RA patients displayed quantitative and qualitative alterations that are the result of both disease-specific and traditional CV risk factors. Accordingly, this MP pool exhibited in vitro detrimental effects on endothelial cells, thus supporting their role as biomarkers of vascular damage.

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