Abstract
Abstract: :
Purpose:To characterize the early response of retinal ganglion cells (RGC) and microglia in a rat model of glaucoma. Methods: Glaucoma was induced in adult female Sprague Dawley rats by cauterizing two episcleral veins. IOP was measured using a Tono Pen. RGCs were retrogradely labeled with the fluorescent dye, 4-Di-10ASP and their reaction to raised intraocular pressure (IOP) was examined in-vivo and on retinal flat mounts. Dying RGCs are phagocytosed by microglia, which become visible when they take up the fluorescent cell debris. Results: Cauterizing two episcleral veins resulted in a consistent increase in IOP. Fundoscopic examination of the optic nerve head revealed cupping 2 months after glaucoma induction. Using in-vivo imaging the earliest signs of RGC death could be detected 20 hours after glaucoma induction in the anesthetized, living animal. Ganglion cells continued to degenerate over time, with 40% having degenerated 2.5 months later. Retinal microglia, which phagocytose dying RGC appeared as early as 72 hours after glaucoma induction. Conclusion: Occlusion of two episcleral veins in the rat results in a reproducible elevation in IOP, optic nerve cupping and RGC loss. In-vivo imaging enabled ganglion cell loss to be traced in the living animal. Microglia are apparently involved in the phagocytosis of dying retinal ganglion cells.
Keywords: 415 ganglion cells • 316 animal model • 470 microglia