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Takeshi Nakajima, Thomas R. Shearer, Mitsuyoshi Azuma; Increased Expression of Integrin α Chains and Their Ligands during Laser-Induced Neovascularization of Rat Choroid. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3010.
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Binding inhibitors of integrins αv and α5 were anti-angiogenic in experimental choroidal neovascularization (CNV). However, a comprehensive understanding of the expression of the integrin isoforms, ligands, and inter-associations is limited in the CNV model. Thus, the purpose of present study was to examine the expression and localization of integrin α chains and their extracellular matrix (ECMs) ligands in retinal/choroidal tissue after laser injury.
CNV, observed by staining with FITC-labeled lectin, was produced in Brown Norway rats with a 532 nm diode laser. Expression and localization of αv and α5 integrins and their ligands was performed by immunohistochemistry in consecutive cryosections. An in vitro cell adhesion assay using retinal endothelial cells and specific antibodies confirmed binding specificity between integrin α chains and ECMs.
Angiogenesis was observed on day 7 after laser injury in choroidal flatmounts and cryosections. Integrin α5 and αv expression massively increased at day 3 and then gradually decreased, but were still elevated on day 14. Increased ligands for α integrins localized closely to their integrins in the laser-injured region. One day after photocoagulation, integrin ligands fibronectin (FN) and vitronectin (VN) were already massively increased. Expression of FN remained stable, but VN returned to normal by day 14. Expression of laminin was only minimally increased at day 1 and then returned to normal by day 3. Cell adhesion assays confirmed specific association of integrin α5 to FN, and αV to VN. Negative control IgG did not stain.
Choroidal injury increased FN and VN ligands followed by time-dependent increases in integrins α5 and αv. The interaction of FN and VN with their specific integrin α chains may be part of the mechanism producing CNV.
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