Activated platelets transfer miRNA to endothelial cells in vitro. (A) Relative quantity of intracellular and secreted cel-miR-39 from resting and activated platelets is shown. Expression data are normalized to an exogenous miRNA spike in for the supernatant and to U6 RNA for the intracellular levels (n = 3). (B) Relative quantity of cel-miR-39 in HMEC-1 cells cocultured with transfected platelets after 3 hours of coculture in the presence or absence of 1 U/mL thrombin (n = 3). Levels are presented relative to miR-16 and normalized against the mean of the cells without thrombin. (C) Representative confocal image of HMEC-1 cells cocultured with miR-Scr-FITC transfected platelets in the presence of 1 U/mL thrombin. Nuclei are stained red.