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Weiming Mao, Tara Tovar-Vidales, Robert J. Wordinger, Abbot F. Clark; Perfusion Cultured Bovine Anterior Eye Segments As An Ex Vivo Model For Studying Glucocorticoid-induced Ocular Hypertension (OHT) And Glaucoma. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5922.
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Glucocorticoid treatment elevates intraocular pressure (IOP) and causes secondary glaucoma, which mimics many features of primary open angle glaucoma (POAG). Studies have shown that elevated IOP is the key risk factor for the development and progression of glaucoma, while lowering IOP prevents disease progression and vision loss. Therefore, induction of OHT is widely used to develop glaucoma models. However, in vivo animal models are time-consuming, and the ex vivo human eye model is limited by high cost, as well as unstable supply and donor eye quality. Thus, we decided to test whether perfusion cultured bovine anterior segments would be a suitable model for glaucoma research.
Fresh bovine eyes were dissected at the equator to remove the posterior segment, vitreous, uvea, retina and lens. After cleaning the pigmented tissue adjacent to the trabecular meshwork, the anterior segment was sealed on a custom-made plexi-dish with an O-ring. Perfusion medium was infused by a syringe pump at 5ul/min. After IOP was stable for 12 to 24 hours, bovine eyes were perfused with medium containing either ethanol (EtOH) as a vehicle control or dexamethasone (DEX) for up to 7 days. IOP was recorded by a pressure transducer and a computerized system. Perfusion medium was collected for Western immunoblotting (WB) analysis of myocilin (myoc) and fibronectin (FN).
The morphology of the bovine TM after 9 days of perfusion culture was similar to that of freshly dissected, non-perfused bovine eyes. Treatment with 0.1µM DEX elevated IOP more than 3 mmHg in some bovine eyes, while others showed little change. In order to define OHT, we analyzed data from 18 EtOH-treated control eyes. The threshold was set at 2.82mmHg, which equals mean pressure change + 2x SD. Approximately 40% (12/29) of the bovine eyes were DEX-responders, which is very close to the DEX-responsive rates observed in human and monkey eyes. WB data showed that DEX treatment not only elevated IOP, but also induced the expression of two DEX-inducible genes, myoc and FN, in perfusion cultured bovine anterior segments.
OHT can be induced by DEX in perfusion cultured bovine anterior segments. This is a fast, affordable and reliable model for studying DEX-induced OHT and trabecular outflow research.
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