Fig. 5. Vascular response to OIR at P17 and P19. (A-D) Numbers of cell nuclei and capillary tufts in the vitreous body, assessed on retinal cross sections at P17. (E) Cell nuclei in the vitreous body at P19. (F-H) Extent of the vascular-free zone as a measure of the vascular response to OIR, assessed on whole-mounted retinas at P17 in which vessels were detected by isolectin staining (F,G, red). During relative hypoxia (P12-P17; Fig. 4A), avascular zones (F) become vascularized. A massive neovascular response occurs around the veins and capillary tufts grow toward the vitreous body (G, arrows). The areas of avascularity at P17 (delineated in G) were comparable in wild-type and GFAP^–/– Vim^–/– retinas (H). (I) VEGF was expressed at similar levels in wild-type and GFAP^–/– Vim^–/– retinas from controls (wt_c vs g–/–v–/–_c) and from mice subjected to OIR (wt_oir vs g–/–v–/–_oir). The data are presented as mean±s.e.m. Asterisks indicate P-values obtained by using Student's t test: ^*, 0.05; ^**, 0.01; ^***, 0.005; ^****, 0.002; ^*****, 0.001. Scale bar, 500 µm (F,G).