Effects of elevated intraocular pressure on mouse retinal ganglion cells

We developed and characterized a mouse model of elevated intraocular pressure (IOP) to investigate the underlying cellular and genetic mechanisms of retinal ganglion cell (RGC) death. IOP was unilaterally increased in C57BL/6J mice by photocoagulation of the episcleral and limbal veins. IOP was measured using an indentation tonometer. RGC survival was measured by retrograde labeling using Dil applied to the superior colliculous. The mechanism of RGC death was investigated using TUNEL staining, immunostaining for cleaved caspase-3, and Western blot for Bcl-2 and Bax expression. RT-PCR was used to measure changes in Bel-2, Bax. Bad, Bak, P53, ICE and Fas. Mean IOP was increased in the treated eyes from 13 +/- 1.8 to 20.0 +/- 2.8 mm HQ at four weeks and 17 +/- 2.2 mm Hg at eight weeks. RGC loss was 15.6 +/- 3.4% at two weeks and 27.3 +/- 4.5% at four weeks after laser photocoagulation. TUNEL staining and caspase-3 positive cells were increased in the ganglion cell layer (GCL) in the treated eyes and seldom found in the control eyes. Bcl-2 expression in control group was higher than in the experimental group, while Bax expression in the control group was less than in experimental group. This mouse model resulted in a consistent, sustained increase in IOP with a reduction in the number of RGCs in the treated eye. The RGCs in eyes with elevated IOP were TUNEL-positive. with increased caspase-3 and decreased Bcl-2, consistent with apoptosis as the mechanism of neuronal cell death. (C) 2004 Elsevier Ltd. All rights reserved.