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Yoko Ito, Ariel Wilson, Christine Vande Velde, Przemyslaw Mike Sapieha, Adriana Di Polo; Ocular hypertension induces early mitochondrial alterations in retinal endothelial cells in a murine glaucoma model. Invest. Ophthalmol. Vis. Sci. 201657(12):.
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© 2017 Association for Research in Vision and Ophthalmology.
Vascular deficits have been proposed to contribute to glaucoma pathogenesis. Endothelial cell dysfunction is predicted to have harmful effects on the integrity of the neurovascular unit. Here, we tested the hypothesis that glaucoma-related ocular hypertension (OHT) leads to early metabolic stress in retinal endothelial cells compromising vascular homeostasis.
OHT was induced by injection of magnetic microbeads into the anterior chamber of EndoMitoEGFP mice, a strain expressing GFP selectively in the mitochondria of endothelial cells. Capillary density, mitochondrial volume, and number of mitochondrial components were analyzed in 3D-reconstructed images from flat-mounted retinas using Imaris software (Bitplane). The expression of proteins involved in mitochondrial dynamics, including dynamin-related protein-1 (DRP-1) and optic atrophy-1 (OPA-1), was examined by western blot analysis of isolated retinal blood vessels. The integrity of the blood retinal barrier was quantified using Evans blue.
At three weeks after induction of OHT, there was a significant decrease in total mitochondrial volume from 140 ± 2 µm3 in endothelial cells from intact, non-injured retinas to 93 ± 7 µm3 in glaucomatous eyes (mean per µm3 vasculature x 10-3 ± S.E.M, p <0.001; N=6/group). A substantial reduction in the number of mitochondrial complexes with a volume greater than 5 µm3 was observed, whereas the density of smaller complexes (<0.5 µm3) markedly increased. Significant upregulation of DRP-1 and OPA-1 was found in vessels isolated from glaucomatous retinas versus intact controls, suggesting alterations in mitochondrial dynamics. Structural alterations in endothelial cell mitochondria were accompanied by a 2.6-fold increase in vasculature leakage in hypertensive retinas (N=3-6/group, P<0.01). These changes were not the result of endothelial cell loss because the density of the vascular network in this model remained unchanged for up to ten weeks after glaucoma induction (N=4-6/group).
Our data demonstrate that OHT triggers early alterations in endothelial cell mitochondria, prior to capillary dropout, concomitant with loss of blood retinal barrier integrity. This study provides insight into mitochondrial damage in endothelial cells induced by ocular hypertension, and suggests that endothelial metabolic compromise contributes to vascular dysfunction in glaucoma.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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