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H. Chen, K.-S. Cho, X. Wei, D. Chen; Constitutive Loss of Retinal Ganglion Cells Induced by a Transient and Chronic Elevation of Intraocular Pressure In Mice. Invest. Ophthalmol. Vis. Sci. 2010;51(13):6101.
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© ARVO (1962-2015); The Authors (2016-present)
To enable applications of genetic mouse technology to the study of glaucoma, we adopted and modified a method of anterior chamber injection of polystyrene microbeads that enables transient and reversible induction of IOP elevation in mice without apparent adverse effects to ocular structures.
Experimental glaucoma was induced in adult C57BL/6J mice unilaterally by anterior chamber inject of fluorescent polystyrene microbeads of different diameters (10 and 15 um). Mouse IOP levels were assessed every other day by a tonolab. Animals are sacrificed at 14, 30 and 60 days after first induction of IOP elevation. The degree of retinal ganglion cell loss was quantified in retinal sections and flat-mounts using FluoroGold retrograde labeling and immunohistochemistry with a primary antibody against beta-III-tubulin. Numbers of RGCs were recorded, and IOP induced axon loss was quantified in optic nerve cross sections using electron microscopy. Markers of retinal injury, such as the expression of HSP27 and retinal astroglial responses, were analyzed by Western blot analysis and immunohistochemistry.
76 out of 81 mice that received microbead injection exhibited consistent IOP elevation above that of uninjected contralateral eyes or PBS injected controls. A single injection of 15 or 10 µm microbeads induced IOP elevation for 2-4 weeks, respectively, while a second injection of 10 um microbeads in week 4 maintained the elevation of IOP to 8 weeks. Correlating with the IOP elevation, both RGC bodies in the retina and their axons underwent ongoing progressive degeneration. Most interestingly, a transient elevation of IOP for 2 weeks resulted in constitutive loss of RGCs even at 8 weeks after IOP had returned to a normal level. A significant increase of expression of Hsp27 and glial fibrillary acidic protein was observed in the retina of high IOP as compared with the controls.
Anterior chamber injection of Microspheres represents a useful and efficient method for inducing IOP elevation in mouse. Induction of constitutive RGC loss after a transient elevation of IOP suggests the involvement of a novel mechanism contributing to RGC degeneration in glaucoma. Development of an inducible model of experimental glaucoma will greatly facilitate our understanding of the mechanisms of glaucoma by taking advantage of the available genetically engineered mouse models. We suggestion that Hsp27 may be use as an injury marker in the glaucoma mouse model.
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