Endothelial Cell Growth Medium 2 (EGM2, PromoCell) was used to culture human umbilical vein endothelial cells (HUVECs) in a 37 o C/5 % CO2 incubator. To harvest HUVECs from T75 culture flasks, cells were washed twice with pre-warmed PBS solution and then cells were detached from the flask by trypsinisation (versene/trypsin, 4/1 v/v, 5 mL, 37 °C). 15 mL of EGM2 medium was then added to the flask to quench the trypsin. Cells were transferred to a 50 mL centrifuge tube and centrifuged at 1200 rpm for 5 min. After discarding the supernatant solution, the pellet was resuspended in 10 mL EGM2 medium and the concentration of cells was measured with a haematocytometer.