2.1 Cell culture
Primary HUVECs were purchased from American Sciencecell company and cultured in endothelial cell medium (ECM) in a 37℃ 5% CO2 saturated humidity incubator. The flasks or dishes used to culture primary HUVECs were coated with fibronectin ( 2 μg/cm2) overnight at 37℃. When the cell fusion rate reached 90%-95%, cells from the logarithmic growth phase were digested with trypsin cell digestive solution at a concentration of 0.05% and then sub-cultured. HUVECs were taken from generations 3-6 and used in subsequent experiments.