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X. Zhou, L. Kong, L. L. Wong, J. F. McGinnis; VEGF Expression in Photoreceptors and Neovascularization in an Animal Model for AMD. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1195.
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In this study, we investigated the main cellular source of VEGF in the retina of the vldlr- -/- mouse and described the progression of neovascularization when new capillaries emerged in the retina.
We performed vascular filling assays using dextran conjugated fluorescein to visualize the choroidal and retinal blood supplies by confocal microscopy in animals ranging from postnatal day 10 to 28. The expression of VEGF in the retina was determined by quantitative real-time PCR, reverse transcription polymerase chain reaction (RT-PCR) and Western blots. We used a VEGF antibody (Santa Cruz) to determine the cellular and subcellular localization of VEGF in retinal sections.
The present study confirmed an increase in the amount of retinal VEGF mRNA and protein in the vldlr-/- mice compared to wild type mice. Confocal microscopy analysis of immunolabeled retinal sections localized VEGF in the outer nuclear layer (ONL) of the vldlr-/- retina adjacent to vascular lesions. Double labeling experiments with antibodies against the soluble photoreceptor protein Recoverin showed that VEGF was located within the cytoplasm of photoreceptor cells. Our results on the developmental appearance of retinal vascular lesions and choroidal neovascular tufts by 3D reconstruction of confocal images suggested that retinal lesions arose prior to the CNV tufts and indicated that the tufts arose from the coalescence of new retinal capillaries growing from the outer plexiform layer through the ONL, the retinal pigment epithelium layer and Bruch’s membrane.
Photoreceptor cells in the vldlr-/- mouse retina express VEGF which leads to the development of angiogenesis within the outer plexiform layer. These new blood vessels grow from the retina into the choroid. The identification of photoreceptors as a source of VEGF is a novel observation and suggests that they participate in the illicit angiogenesis within the ONL and the choroid. These data support the use of the vldlr-/- mouse retina as a model for the human disease, RAP and as a tool for the evaluation of therapeutic strategies to cure and/or prevent the disease.
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