Targeted disruption of the CD18 or ICAM-1 gene inhibits choroidal neovascularization

PURPOSE. To investigate the role of the leukocyte adhesion molecules CD18 and intercellular adhesion molecule (ICAM)-1 in the development of choroidal neovascularization (CNV). METHODS. Laser photocoagulation was used to induce CNV in wild-type C57BL/6J mice and species-specific counterparts with targeted homozygous disruption of the CD18 or ICAM-I gene. Expression of CD18 and ICAM-I after laser injury was assessed by immunostaining. CNV responses were compared on the basis of en masse volumetric measurements Obtained by confocal microscopy 2 weeks after laser injury and by determination of fluorescein angiographic leakage at 1, 2, and 4 weeks after laser injury. RESULTS. The site of laser injury showed upregulation of ICAM-I and invasion by CD18-positive leukocytes within I day of laser injury. Significantly fewer lesions exhibited fluorescein leakage defined to be pathologically significant in CD18-deficient mice at weeks 1, 2, and 4 weeks and in ICAM-1-deficient mice at 1 and 4 weeks, compared with the control. There were a significantly greater number of lesions without fluorescein leakage in CD18-deficient mice than in the other two groups at all time points. The volume of CNV in CD18- and ICAM-1-deficient mice was significantly less than in wild type. CONCLUSIONS. These data suggest a nonredundant role for leukocyte adhesion to vascular endothelium in the development of laser-induced choroidal neovascularization.