Preparation of platelet-poor plasma Platelet-poor plasma was obtained using three different centrifugation protocols (Table 1). Each centrifugation protocol included two steps. The initial step for protocol 1 consisted of two centrifugations at 5000 × g for five minutes at room temperature. After the first centrifugation at 5000 × g for five minutes, the supernatant was transferred into a new tube, leaving 200 µL above the cell pellet, and was centrifuged again for five minutes at 5000 × g. In protocol 2, platelet-poor plasma was obtained by an initial single centrifugation at 5000 × g for 15 minutes, and in protocol 3 by centrifugation at 1500 × g for 15 minutes. After centrifugation, the supernatant was transferred into a new tube, while discarding the last 500 µL at the base of the centrifuged tube. Aliquots of 500 µL were stored at −80°C. After thawing quickly at 37°C, a microparticle pellet was obtained from the platelet-poor plasma by a second centrifugation step at 17,000 × g for either 20 or two minutes. Subsequently, the supernatant was discarded and the microparticle pellet was reconstituted in Annexin V buffer (Becton Dickinson, Franklin Lakes, NJ) at 4°C. All buffers were sterile-filtered with a 0.2 µm filter (Whatman, Piscataway, NJ).