Glaucoma-inducing Procedure in an In Vivo Rat Model and Whole-mount Retina Preparation.

Glaucoma is a disease of the central nervous system affecting retinal ganglion cells (RGCs). RGC axons making up the optic nerve carry visual input to the brain for visual perception. Damage to RGCs and their axons leads to vision loss and/or blindness. Although the specific cause of glaucoma is unknown, the primary risk factor for the disease is an elevated intraocular pressure. Glaucoma-inducing procedures in animal models are a valuable tool to researchers studying the mechanism of RGC death. Such information can lead to the development of effective neuroprotective treatments that could aid in the prevention of vision loss. The protocol in this paper describes a method of inducing glaucoma - like conditions in an in vivo rat model where 50 µl of 2 M hypertonic saline is injected into the episcleral venous plexus. Blanching of the vessels indicates successful injection. This procedure causes loss of RGCs to simulate glaucoma. One month following injection, animals are sacrificed and eyes are removed. Next, the cornea, lens, and vitreous are removed to make an eyecup. The retina is then peeled from the back of the eye and pinned onto sylgard dishes using cactus needles. At this point, neurons in the retina can be stained for analysis. Results from this lab show that approximately 25% of RGCs are lost within one month of the procedure when compared to internal controls. This procedure allows for quantitative analysis of retinal ganglion cell death in an in vivo rat glaucoma model.

Neuroprotective Strategies in Glaucoma.

BACKGROUND: Glaucoma is characterized as a neuropathic disease that causes progressive degeneration of retinal ganglion cells (RGCs) in the retina, resulting in irreversible loss of vision. All conventional treatments for glaucoma are focused on reducing intraocular pressure (IOP) in the anterior chamber of the eye. However, these treatments alone are insufficient to halt the progression of the disease. As a result, neuroprotective strategies have been developed that prevent retinal neuron loss and disease progression. METHODS: The goal of this review is to summarize and discuss neuroprotective strategies in glaucoma at the level of the retina and the ganglion cell layer instead of treatments targeting IOP. Recent and past neuroprotective therapies used to prevent the loss of retinal ganglion cells, the loss of axons in the optic nerve and the loss of vision and function associated with glaucoma are presented. RESULTS: Pharmacological approaches have targeted specific receptors, signaling cascades and neurotrophic factors to induce neuroprotection in the retina, while others have focused on the mechanism of cellular loss associated with glaucoma, including excitotoxicity, oxidative stress and apoptotic processes. In addition to neuroprotective pharmacological treatments, stem cell, gene therapy and viral research have demonstrated neuroprotection against the loss of RGCs in glaucomatous conditions. CONCLUSION: It is likely that future development for glaucoma treatment will include a combination of these treatments to prevent the pathophysiology of glaucoma.