Fig. 5. Endothelial cells-specific conditional deletion of IL-33 reduces hypoxia-induced pathological angiogenesis.

a Schematic diagram to show the generation of endothelial cells-specific IL-33 knockout mice. b Eyes from IL-33^+/+ and IL-33^iΔEC pups were enucleated, retinas isolated, and extracts were analyzed for IL-33 levels by Western blotting and normalized to β-tubulin. c–e IL-33^+/+ and IL-33^iΔEC mice pups were exposed to OIR and at P17 the retinas were isolated, stained with isolectin B4, and flat mounts were examined for endothelial tip cell formation (c) retinal neovascularization (d), and avascular area (e). The middle column in d shows the higher magnification of the area selected. Neovascularization is highlighted in red in the third column of d. The bar graphs represent quantitative analysis of percentage of neovascularization and avascular area, expressed as Mean ± SD. *P < 0.05 vs IL-33^+/+. Scale bar represents 20 μm in c upper row, 50 μm in c lower row, 500 μm in d, e.