Promotion of corneal angiogenesis and VEGFR2 expression in PD-L1−/− mice after suture placement. A: Corneal NV was induced in WT and PD-L1−/− mice (arrows show the upper margin of the NV area). B: In a masked fashion, corneal NV was scored biomicroscopically with a slit-lamp using a grid system. Values are expressed as the mean (±standard error of the mean) of 6 corneas. C: On day 14, whole corneas were dissected and stained with anti–CD31-FITC (shown in gray scale). D: The density of blood vessels (CD31+) covering the cornea was analyzed. Values are expressed as the mean (±standard error of the mean) of 6 corneas per treatment group (**P < 0.01 vs vehicle-treated group). E: The mRNA expression level of VEGFR2 on the corneas was determined 24 hours or 72 hours after suture placement. Data were normalized to glyceraldehyde-3-phosphate dehydrogenase mRNA and values were expressed as the fold change over normal control corneas. Results represent the mean (±standard error of the mean) of 4 samples per group (one cornea per sample, *P < 0.05, **P < 0.01, t-test). Data are representative of two independent experiments.