Figure 4. Chronic elevation of VEGF in the retinas of rho/VEGF-transgenic mice causes gradually increasing leukostasis and retinal nonperfusion.

Rho/VEGF-transgenic mice of different ages, day 16, day 20, day 30, 7 months, 12 months, or 15 months, or normal wild-type mice at 5 weeks (N-5wk) or 8 months of age (N-mo8) were perfused with rhodamine-labeled Con A. Several vessels showed single adherent leukocytes in day 20 rho/VEGF mice (A) and more were seen in day 30 mice (B). In 7-month-old or older rho/VEGF mice, there were many more intravascular leukocytes and they often appeared to occlude the lumen of vessels exemplified in 3 separate 7-month-old mice by plugging at a vessel bifurcation (C), by a line of leukocytes (D), or packing of a substantial length of a vessel lumen with a large aggregate (E). Similarly, there were leukocytes plugging vessels particularly at branch points in the retinas of 12-month-old (F) and 15-month-old (G) rho/VEGF mice. The mean (± SEM) number of intravascular leukocytes per retina in both 20-day-old and 30-day-old rho/VEGF mice, but not 16-day-old mice, was significantly greater than that in N-5W control mice (*P = 0.05; P = 0.022 [day 20], P < 0.001 [day 30], P = 0.349 [day 16] compared to 5 weeks by unpaired t tests) and mean intravascular leukocytes were significantly greater in 7-month-old, 12-month-old, and 15-month-old rho/VEGF mice compared with N-8M control mice (H) (n = 6 for each bar except 7 months, for which n = 9; **P < 0.001 by unpaired t tests). Retinal flat mounts from fluorescein-dextran-perfused 7-month-old (I) and 12-month-old (J) rho/VEGF mice show abruptly ending vessels and large areas of nonperfusion (asterisks). Scale bar: 50 μm (A–D and G); 100 μm (E and F).