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Yoko Ito, Nicolas A Belforte, Jorge Luis Cueva Vargas, Christine Vande Velde, Adriana Di Polo; Alterations in the retinal vascular network after induction of ocular hypertension in a murine glaucoma model.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2447.
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© ARVO (1962-2015); The Authors (2016-present)
Vascular endothelial dysfunction resulting in decreased ocular blood flow has been proposed to contribute to neurodegeneration in glaucoma. Using a murine glaucoma model, we examined the effect of ocular hypertension (OHT) on various aspects of the retinal vasculature.
OHT was induced in mice by injection of polystyrene magnetic microbeads (8 x 108 beads/ml) in the anterior chamber to block aqueous outflow through the trabecular meshwork. This procedure leads to gradual increase in intraocular pressure and subsequent retinal ganglion cell (RGC) death detected as early as three weeks after OHT induction. C57BL/6 mice or EndoMito-EGFP mice, which exhibit selective expression of green fluorescent protein (GFP) in the mitochondria of endothelial cells, were subjected to OHT. Three, six, and ten weeks later, mice were perfused and retinal flat-mounts were prepared for immunohistochemical analyses using the vascular marker isolectin. The retinal vascular network and the endothelial mitochondria were visualized by confocal microscopy and three-dimensionally reconstructed using Imaris software (Bitplane). Vessel density, mitochondrial volume density, and the number of mitochondrial components were quantified and compared using ANOVA.
The total capillary density in the superficial, middle and deep layers of the retinal vasculature network remained unchanged at three (N=5), six (N=4), and ten (N=3) weeks of OHT induction relative to intact retinas (N=6). Interestingly, there was a significant decrease in total mitochondrial volume density per volume of vasculature at three weeks (p<0.001) and six weeks (p=0.001) after OHT induction (N=4-6/group). Moreover, glaucomatous retinas displayed a substantial reduction in the number of individual mitochondrion with a volume density greater than 75µm3.
Our data indicate that OHT triggers important morphological alterations in endothelial cell mitochondria in vivo. Changes in mitochondrial dynamics in response to environmental and metabolic stress are known to regulate endothelial cell function. Therefore, our study suggests that alterations in endothelial mitochondria might contribute to vascular dysfunction in glaucoma.
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