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L. Wu, J. Cao, M. Forbes, J.C. Tsai; Immunoreactivity of Erythropoietin and Its Receptor in Retina and Optic Nerve in an Experimental Rat Model of Glaucoma . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1316.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To assess the ocular histological changes induced by episcleral venous cautery (EVC) in a rat model of glaucoma and to describe the expression pattern of erythropoietin (EPO) and erythropoietin receptor (EPO–R) in retina and optic nerve following intraocular administration of exogenous EPO. Methods: The EVC method was performed to create an ocular hypertensive model of glaucoma in adult rats. A single intravitreal injection of EPO or normal saline (NS) was administered at the end of the EVC procedure. The eye tissues were collected for histological and immunohistochemistry (IHC) evaluation after 21 days of elevated intraocular pressure. Immunohistochemistry was assessed in retinal and optic nerve specimens, focusing on EPO and EPO–R reactivity, as well as assaying for Thy–1, a specific marker for retinal ganglion cells (RGCs). Results: Compared to normal eyes, morphological changes were observed in the EVC eyes, including dilation of the aqueous humor drainage pathways and iridial and choroidal vascular beds. Histological changes encompassed vacuolization in the retina (especially in the photoreceptor inner and outer segment, RGC and inner limiting membrane layers), as well as reduced RGC density. In the EVC–EPO treated eyes, the extent of vacuolization as well as the reduction in RGC density were attenuated. No significant differences were observed in EPO immunoreactivity between EVC–EPO and the normal contralateral eyes. In terms of EPO–R reactivity, stronger positive signals were observed in the RGC layer, inner nuclear layer, and photoreceptor inner segment in the EVC–EPO eyes when compared to normal eyes. For Thy–1, positive reactions were localized to the photoreceptor outer segment, RGC layer, and retinal nerve fiber layer in control eyes, and were increased in the EVC–EPO eyes. In the optic nerve specimens, intensive immunoreactivity of EPO–R and Thy–1 were observed in the EVC–EPO eyes. Conclusions: In the EVC cautery model of glaucoma, widespread histological changes were observed throughout the aqueous drainage and surrounding vascular systems. Increased immunoreactivity of EPO–R and Thy–1 were observed in EVC–EPO eyes. These immunoreactivity changes might contribute to the increased RGC survival observed with intraocular administration of EPO.
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