HUVECs (Lonza) were grown in endothelial cell basal medium, EBM-2 (Lonza), with the addition of 2% FBS and SingleQuots Kit (EGM-2 medium; Lonza) at 37°C with 5% CO2. After the first expansion, cells were then grown in EGM-2 medium using 2% exosome-depleted FBS (System Biosciences). To mimic ischemia in vitro, ECs were exposed to hypoxia (1% pO2) for 24 hr followed by treatment with different concentrations of PF/plasma-derived exosomes or exosome-depleted PF/plasma for 24 hr. HUVECs were used between passages 2 and 6.