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Kayla Ficarrotta, Christopher L Passaglia; Effect of continuous eye perfusion on rat retinal ganglion cells. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2558. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Optic neuropathies observed in human glaucoma can be induced in animals by damaging the trabecular meshwork of the eye and increasing intraocular pressure (IOP). Existing methods of glaucoma induction cause IOP changes that are variable in time course and magnitude. The aim of this study was to develop a method of chronically elevating IOP in a prescribed and controlled manner that does not target the trabecular meshwork.
A fine polyimide tube was implanted in the anterior chamber of one eye of Brown-Norway rats and passed subdermally to a skull mount, which was connected via a tether system to an external reservoir filled with artificial aqueous humor. An in-line pressure transducer continuously measured IOP, and pressure readings were sporadically checked by tonometry. In five implanted animals, IOP was elevated 10 mmHg for 9 weeks. In three implanted animals, IOP was left undisturbed for the 9-week period. Following the experiment, fundal imaging was performed on each eye to visualize the optic nerve head and retinal vasculature and both retinas were dissected, immunoreacted for Brn3a, and prepared as wholemounts. Fluorescent micrographs were obtained at multiple depths across the entire retina to create a maximum z-projection montage. Retinal ganglion cells (RGC) were counted using an automatic process and a size-based correction algorithm that accounts for overlapping cells.
IOP was successfully elevated in implanted animals, without chronic leakage of fluid or obvious damage to the cornea or iris. Optic nerve and retinal vasculature anatomy looked normal. RGC counts for implanted high-IOP eyes, implanted normal-IOP eyes, and non-implanted control eyes were 64298 ± 3945, 96662 ± 1068, and 94565 ± 2672, respectively. RGC counts differed significantly from normal only for high-IOP eyes, indicating that the cell loss was not caused by the surgical procedure or presence of the cannula. Regional variations in RGC density were also observed and quantified.
Continuous eye perfusion for several weeks causes glaucoma-like patterns of RGC loss in rats without experimentally blocking fluid outflow pathways of the eye. The perfusion-induced glaucoma model that we have developed allows researchers to set and reversibly manipulate IOP for the first time, which could yield unique and important insights into the disease.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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