Platelet-derived microparticles generated in vitro resemble circulating vesicles of patients with rheumatoid arthritis and activate monocytes

Patients with rheumatoid arthritis (RA) have increased amount of platelet-derived microparticles (PMPs) positive for citrullinated peptides (CPs) that form immune complexes (PMPs-ICs). Monocytes are important inflammatory mediators that play a role in the clearance of PMPs-ICs. We aimed to generate PMPs-ICs in vitro and determine its effect on monocytes from patients with RA and healthy individuals (HI). PMPs from patients showed platelet markers, mitochondria content, and phosphatidylserine exposure similar to PMPs from HI. However, patients had a higher frequency of IgG+ and CPs+ vesicles than HI. PMPs-ICs generated in vitro were similar to the circulating vesicles of patients with respect to IgG- and CPs-positivity. PMPs-ICs induced pro-inflammatory cytokines and CX3CR1 expression in monocytes from HI, and IL-10 and CD36 upregulation in monocytes from patients. These results suggest that PMPs-ICs induce activation of monocytes, with a pro-inflammatory response in HI and a more tolerant response in cells of patients with RA.