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Cavit Agca, Andreas Ebneter, Martin Sebastian Zinkernagel; Microglia dynamics in experimental branch vein occlusion in a mouse model. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2260.
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© ARVO (1962-2015); The Authors (2016-present)
Branch retinal vein occlusion (BRVO) is a common vision-threatening disease in the adult population. Loss of vision develops rapidly and mainly occurs due to formation of macular edema as a result of occluded vein. BRVO can be induced by laser photocoagulation in mouse and other animal models. In most reports on experimental vein occlusion the majority of veins was occluded, resulting in a phenotype resembling central vein occlusion disease. We describe here a mouse model of BRVO using laser photocoagulation to block a single vein and study retinal disease mechanisms in this model. Additionally, we wanted to characterize the microglia and Muller cell dynamics in this model.
Mice were injected with Bengal Rose dye through tail vein. Laser burns were applied to the superior vein inducing intravascular coagulation and blockage. Retinas were analyzed in vivo by fundus imaging and fluorescein angiography. To determine microglial response, vein occluded retinas were fixed and whole mount immunohistochemistry was performed using F4/80 and Iba1 antibodies as well as isolectin for co-imaging of the vasculature. Vein occluded retinas were also collected for RT-PCR analysis Vegf, Tnf, Ccl5, Cntf and Gfap transcript levels were determined at day 7 and 14 after laser.
We have successfully characterized a mouse model with a single vein occlusion. Whereas ischemic areas surrounding the lasered vein were evident at day 3, reperfusion was detectable at day 7 and 14 by fluorescein angiography often in conjunction with collaterals. Consistent with this finding, there was no significant upregulation of Vegf levels at day 7 and 14 timepoints compared to healthy controls. Immunohistochemical analysis using F4/80, Iba1 and isolectin identified a region of activated microglia/macrophages that co-localized with the drainage area of the occluded vein. This finding was also supported by increased levels of Ccl5 and Tnf expression. Moreover, Gfap and Cntf, which are expressed in activated Muller cells, are also upregulated.
These results strongly argue that BRVO of a single vein is sufficient to induce activation of Muller cells and microglia in mouse neuronal retina but does not upregulate Vegf. The experimental vein occlusion model resembling BRVO may be a very valuable tool to study disease mechanisms especially because specific questions can be answered by using genetically modified mouse models.
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