Apoptosis of Retinal Ganglion Cell after Ischemia-reperfusion Injury of Optic Nerve in Rabbits

ABSTRACT

To develop a new animal model for ischemia-reperfusion infury of the optic nerve in rabbits and to investigate the pattern of retinal ganglion cell apoptosis and bcl-2 staining in the model, occlusion of the posterior ciliary arteries for 2 hours and reperfusion were performed in one eye of thirty rabbits. In Group I(15 eyes), the optic nerve and the posterior ciliary arteries were tied while in Group II(15 eyes), the posterior ciliary arteries only were tied. The contralateral eyes received sham operation without occlusion. Following reperfusion of 24 hours(5 eyes), 48 hours(5 eyes), and 1 week(5 eyes), in each group respectively, both eyes were enucleated. TUNEL(TdT-mediated dUTP nick end labeling) staining for DNA fragmentation and bcl-2 immunohistochemical staining were done. The numbers of TUNEL-postitive ganglion cells were significantly increased at 24 and 48 hours in Group I and II compared to the control eyes(P<0.05). The numbers of TUNEL-positive ganglion cells in Group I were significantly larger than in Group II at 48 hours(p=0.01). Though the numbers of TUNEL-positive ganglion cells decreased progressively until 1 week, those in Group II at 1 week were still significantly larger than in control eyes(P=0.04), Which suggested the ischemia-reperfusion induced apoptosis of ganglion cell occurred at least until 1 week. Bcl-2 was stained strongly positive at the TUNEL-positive area and in Muller cells compared to the control eyes. The ischemia-reperfusion injury of the optic nerve induced apoptosis of retinal ganglion cell in the new animal model. The overexpressionof bcl-2 at the TUNEL-positive area and in Muller cells can be assumed to be a defense mechanism against retinal ganglion cell death by apoptosis under the ischemic condition. The results of this study will provide baseline data ganglion cell death.