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Thuy Linh Tran, Toke Bek, Morten D. de La Cour, Søren Nielsen, Jan U. Prause, Steffen Hamann, Steffen Heegaard; Aquaporins in glaucoma eyes. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6609.
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Glaucoma is a neurodegenerative disorder with loss of retinal ganglion cells and axons. Elevated intraocular pressure is a significant risk factor in the development of glaucoma. Aqueous humour secretion is in part maintained by the aquaporins (AQPs) and AQPs also regulate fluid homeostasis in the retina. We investigate the expression of AQP1, AQP3, AQP4, AQP5, AQP7 and AQP9 in human glaucoma eyes compared to control normal eyes.
Immunohistochemistry for AQP1, AQP3, AQP4, AQP5, AQP7 and AQP9 was performed on human paraffin embedded eyes. Nine glaucoma eyes were examined comprising three eyes diagnosed with simplex glaucoma, three eyes with neovascular glaucoma and three eyes with chronic angle closure glaucoma. The three control eyes had normal intraocular pressure without glaucoma. From each immunohistochemical slide representative fields (x20 objective) of various structures within the eye were captured. Using Photoshop software optical densities were generated and indices of immunohistochemical intensity were calculated.
Immunostaining showed labeling of AQP7 in the Müller cell endfeet with an increased intensity in glaucoma eyes (P=0,006). AQP9 labeling of the retinal ganglion cells (RGC) showed decreased intensity per cell (P<0,0001). In the optic nerve fibers immunolabeling of AQP1 and AQP4 was seen in the myelinated part and AQP9 was found in both the unmyelinated and myelinated part. No difference in AQP1, AQP4 and AQP9 labeling was found in the optic nerve fibers between normal and glaucoma eyes.
This is the first study investigating the AQPs in human glaucoma eyes. We found a reduced expression of AQP9 in retinal ganglion cells in glaucoma eyes. Glaucoma also induced increased AQP7 expression in the Müller cell endfeet. These results suggest that changes in retinal AQP expression are associated with the development of glaucoma.
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