The most common cause of new blindness in young patients is retinal neovascularization , and in the elderly is choroidal neovascularization. Therefore, there has been a great deal of attention focused on the development of new treatments for these disease processes. Previous studies have demonstrated partial inhibition of retinal neovascularization in animal models using antagonists of vascular endothelial growth factor or other signaling molecules implicated in the angiogenesis cascade. These studies have indicated potential for drug treatment , but have left many questions unanswered. Is it possible to completely inhibit retinal neovascularization using drug treatment with a mode of administration that is feasible to use in patients? Do agents that inhibit retinal neovascularization have any effect on choroidal neovascularization? In this study , we demonstrate complete inhibition of retinal neovascularization in mice with oxygen-induced ischemic retinopathy by oral administration of a partially selective kinase inhibitor that blocks several members of the protein kinase C family , along with vascular endothelial growth factor and platelet-derived growth factor receptor tyrosine kinases. The drug also blocks normal vascularization of the retina during development but has no identifiable adverse effects on mature retinal vessels. In addition, the kinase inhibitor causes dramatic inhibition of choroidal neovascularization in a laser-induced murine model. These data provide proof of concept that pharmacological treatment is a viable approach for therapy of both retinal and choroidal neovascularization. (Am J Pathol 1999, 154:1743-1753)The retina receives its blood supply from two vascular beds: retinal vessels, which supply the inner two-thirds of the retina, and choroidal vessels, which supply the outer one-third. Damage to retinal blood vessels resulting in closure of retinal capillaries and retinal ischemia occurs in several disease processes, including diabetic retinopathy, retinopathy of prematurity, branch retinal vein occlusion, and central retinal vein occlusion; they are collectively referred to as ischemic retinopathies. Retinal ischemia results in release of one or more angiogenic factors that stimulate neovascularization. The new vessels break through the internal limiting membrane that lines the inner surface of the retina and grow along the outer surface of the vitreous. They recruit many other cells and produce sheets of vessels, cells, and extracellular matrix that exert traction on the retina, often leading to retinal detachment and severe loss of vision. Panretinal laser photocoagulation increases oxygenation in the retina and can result in involution of neovascularization. 1 However, despite the effectiveness of laser photocoagulation, 2 diabetic retinopathy remains the most common cause of severe vision loss in patients less than 60 years
Two outbreaks of acute toxoplasmosis involving 8 adult patients in Korea were linked to eating uncooked pork. In the first outbreak, 3 patients developed unilateral chorioretinitis within 3 months of eating a meal consisting of raw spleen and liver of a wild pig. In the second outbreak, 5 of 11 soldiers who ate a meal consisting of raw liver of a domestic pig developed lymphadenopathy. All 8 patients had high levels of IgG Toxoplasma gondii antibodies (> or = 1:1024) in the Sabin-Feldman dye test, modified agglutination test incorporating mercaptoethanol, and latex agglutination test. T. gondii IgM antibodies persisted in these patients for several months. Most patients had a favorable response to anti-T. gondii chemotherapy with pyrimethamine and sulfanomides.
Fibroblast growth factor-2 (FGF2) is a potent mitogen for vascular endothelial cells and exogenous administration of FGF2 stimulates angiogenesis. However, increased expression of FGF2 in the retina does not cause angiogenesis. One possible explanation is that FGF2 may not be capable of initiating angiogenesis unless it is administered in pharmacologic levels or there is coexpression of another angiogenic factor. Alternatively, there may be control mechanisms that sequester FGF2 in vivo, preventing it from manifesting its in vitro angiogenic activity. We tested the first hypothesis by crossing mice that express FGF2 in the retina with mice that express vascular endothelial growth factor (VEGF) in the retina. Surprisingly, despite comparable levels of VEGF expression, mice that expressed both FGF2 and VEGF had significantly less neovascularization than mice that expressed VEGF alone. The second hypothesis was tested by treating Rho/FGF2 transgenic mice with low-intensity laser photocoagulation that disrupts photoreceptors, but does not rupture Bruch's membrane, or intense laser that ruptures Bruch's membrane. In Rho/FGF2 transgenics, but not wild type mice, choroidal neovascularization developed in areas of low-intensity laser. Both wild type and transgenic mice developed choroidal neovascularization in areas of intense laser that ruptured Bruch's membrane, but the area of neovascularization was significantly greater in transgenics. These data suggest that increased retinal expression of FGF2 is angiogenic only when it is accompanied by cell injury that overcomes sequestration control mechanisms.
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