A–C FSA-FITC uptake assay (N = 2 biological replicates) on ETV2-ECs and ETV2-SPI1-ECs with and without addition of VEGFA, as well as on BALB/c LSECs and hepatic stellate cells (HSCs). Images are representative for 24 h exposure to FSA-FITC. Scale bars are 300 µm. FITC fluorescence was measured every hour. Statistical differences were assessed by mixed ANOVA. D IgG-AF555 uptake assay. ETV2-ECs and ETV2-SPI1-ECs were exposed for 2 h to 100 µg/ml IgG-AF555 to measure the clathrin-mediated endocytosis of IgGs upon their binding to CD32B. Scale bars are 50 µm (representative example of N = 3 biological replicates). E Comparison of the percentage of IgG-AF555-positive cells in ETV2-ECs and ETV2-SPI1-ECs at day 12 of differentiation. Statistical assessment by Student’s T test. F Comparison of the AF555 intensity of IgG-AF555-positive cells in ETV2-ECs and ETV2-SPI1-ECs at day 12 of differentiation. Statistical assessment by Wilcoxon rank-sum test. G Confocal imaging of ETV2-SPI1-ECs exposed to IgG-AF555. Cells were co-stained with an anti-RAB5 antibody to evaluate co-localisation of IgG-AF555 and endosomes. H Scanning electron microscopy of ETV2-ECs, ETV2-SPI1-ECs, and BALB/c LSECs. Scale bars are 5 µm (representative example of all cells per coverslip). Average pore diameters are shown in I.