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Bing Li, Yu Wang, Shutong Cao, Olga Kraszewska, Richard Ornberg, Ganesh Prasanna; Foreign-body-reaction-induced chronic ocular hypertension in rat. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1983.
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To develop a chronic ocular hypertension model in rats by inducing foreign body reaction (FBR) and scar tissue formation in Schlemm’s canal (SC) and trabecular meshwork (TM) following insertion of human hair into the SC .
A human hair was inserted around SC of one eye in rats; the other eye was untreated. Intraocular pressure (IOP) was monitored weekly for eight months with a TonoLab. Retinal functional changes were assessed using photopic negative response (PhNR) elicited using green Ganzfeld flashes (22.76cds/m2). Immunohistochemical analysis was performed on anterior segments of treated and control eyes. Sections were immunolabeled with Ilba1 antibody for macrophages and stained with Trichrome collagen. Retinal flat-mounts were prepared with Brn-3a immunolabeling to count retinal ganglion cells (RGCs).
Hair inserted into the rat SC produced a gradual, chronic IOP elevation lasting at least eight months. At week 31, a 25% increase in IOP was observed in the experimental eye (IOPexp eye = 20 ± 1 mmHg; mean ± SEM; IOPcontralateral eye = 16 ± 1 mmHg; p = 0.039). Six months post-procedure, granuloma, increased macrophages and foreign body giant cells, and dense fibrosis based on collagen staining were observed in the angle around the inserted hair of the experimental eye. The figure shows positive staining of CD3 immunoreactivity was mainly detected in the SC and TM area around the inserted hair, which confirm the T cell infiltrating. Preliminary data in FBR eyes indicate a trend toward reduction in PhNR post 8 months (35 ± 2.8%, p = 0.333), indicating reduced retinal ganglion cell (RGC) activity. In retinal sections, Brn-3a labeled RGCs were reduced 26% ± 19 (P = 0.001) at six months and 37 ± 16% (P = 0.001) at eight months compared to contralateral eyes.
In rats, a FBR model produces stable, moderately elevated IOP which results in functional and morphological changes to the retina, probably via changes in RGC density.
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