Platelet-derived microparticles trigger THP-1 monocytic cell aggregation and release of pro-coagulant tissue factor-expressing microparticles in vitro.

Microparticles (MPs) released by blood or endothelial cells are present in plasma for transfusion. They originate from the collected donor blood or are triggered by the variable steps taking place during collection and production/storage processes of blood components. While MPs may contribute to hemostasis, their presence in transfused plasma may lead to uncontrolled thrombin generation when transfused to susceptible cancer or hypercoagulable patients. Understanding the biochemical and cellular triggers of MP-mediated thrombogenesis is therefore crucial. We isolated platelet MPs (PMPs) present in platelet concentrate supernatant plasma (N-PMPs) or prepared by activation of isolated platelets using 0.1 IU/mL thrombin (T-PMPs). N-PMPs and T-PMPs were characterized by dynamic light scattering and counted by tunable resistive pulse sensing to determine population size and number. T-MPMs, but not N-PMPs, induced immediate, long-lasting, strong aggregation of THP-1 monocytic cells in vitro. In addition, co-cultures of THP-1 cells with both N-PMPs and T-PMPs triggered the generation of pro-coagulant tissue factor (TF)-bearing MPs from THP-1 cells. Therefore, some PMPs may induce THP-1 monocytic cell aggregation in vitro and trigger immune cell-mediated thrombogenicity linked to the release of pro-coagulant tissue factor-bearing MPs. Controlling the impact of the presence of PMPs in transfused blood components in certain patient population or critically ill patients deserves in-depth consideration.