Abstract
Purpose: :
To determine whether lymphangiogenesis occurs in an animal model of laser-induced choroidal neovascularization and whether its presence is associated with the development of choroidal neovascular complex.
Methods: :
Choroidal neovascularization was induced in 6 eyes of 3 adult C57BL/6 mice. For this purpose, mice were anesthetized intraperitoneal injection of a mixture of 80 mg/kg ketamine and 12 mg/kg xylazine. Topical anesthesia was achieved by instilling 1% proparacaine solution, and both pupils were dilated with 2.5% topical cyclopentolate. 16-24 laser spots were placed in each posterior quadrant of the fundus using a double frequency NdYAG laser (532 nm; 50 micrometer spot size; 0.1 seconds; 600 mW). One week later, animals were perfused through the heart under deep anesthesia with 1 ml of 5% (weight/volume) high-molecular-weight (1x106 Da) dextran-fluorescein complex in PBS. Eyes were enucleated and flatmounts of the RPE-choroid complex was immunostained Cy3-conjugated antibody for the expression lymphatic vessel endothelial receptor-1 (LYVE-1). Using a multiphoton scanning laser confocal microscope (FluoView, Olympus, Tokyo, Japan) the incidence as well as the co-presence of choroidal neovascular complex and lymphatic vessels was determined. Specimens that were not stained with the primary antibody were taken as negative controls, whereas conjunctiva was used for positive control.
Results: :
One week after laser photocoagulation 63.2% of the laser spots yielded choroidal neovascular complex. There were scattered LYVE-1 positive cells in the sensory retina close to the inner surface. These individual cells were more abundant at around the laser spots. Unlike to these single cells, 10.5% of the laser spots also revealed LYVE-1 positive cells that were organized as tubular structures similar to lymphatic channels. These lymphatic channels were originating deep in the choroid and extending into the subretinal space. They were present only at spots were positive for choroidal neovascularization.
Conclusions: :
Lymphangiogenesis is a part laser-induced choroidal neovascularization. Its concordance with neovascular complex suggests its role in the development of subretinal neovascularization. Possible effects of lymphangiogenesis inhibitors on choroidal neovascularization are yet to be determined.
Keywords: age-related macular degeneration • choroid: neovascularization • immunohistochemistry