Figure 2

Flt1^+/− embryos showed enhancement of vascular permeability with huge vesicle-like structures in capillary endothelial cells.

(A–C) Vascular permeability assay in E14.5 embryos. Frozen sagittal sections show the nuclei of BECs alone in WT embryos and those of surrounding tissues in Flt1^+/− embryos following intravenous injection of Hoechst 33258 (n = 6 each group). (D–J) Transmission electron microscopic images of capillaries in WT and Flt1^+/− embryonic back skin at E14.5. Endothelial cells of the blood capillaries containing erythrocytes (e) have an intricate intricate infolding of the plasma membrane and more huge vesicle-like structures (asterisks) which sometimes reach the lateral plasma membrane where adherens junctions reside (H, arrowheads) or are connected to the vascular lumen ((I,J) arrow in adjacent sections) in Flt1^+/− embryos. (K) Number of vesicle-like structures in capillary endothelial cells (n = 6 each group). Data are presented as mean ± standard error of the mean. ***P < 0.001 and **P < 0.01 as determined by unpaired two-tailed Student’s t-test. N.S. = not significant.