The Role Of Erythropoietin In Retinal Ischemia And Retinal Degeneration

Objective: To observe the therapeutic effects of erythropoietin (EPO) on experimental retinal ischemia, and to explore the possible protective mechanism of EPO. Methonds: The Wistar rat model of experimental retinal ischemia was made by increasing the introcular pressure. A total of 36 male rats were divided into normal (4), saline (16) and EPO (16) groups randomly. Befour 24 hours of ischemia/reperfusion, rhEPO 5,000U/kg was injected intraperitoneally in EPO group and saline was injected intraperitoneally in saline group. The saline and EPO group were diveded into 12, 24, 48 and 72 hours after reperfusion. The EPO expression in retina was observed by EPO detectation. Photoreceptor necrosis and apoptosis was assessed by the method of HE staining and TUNEL. The expression of Caspase-2, Bcl-2,. Fas, FasL were detected by immunohistochemistry.Results: (1) EPO detectation: The expression of EPO was observed in the retinae of both normal and ischemic rats, localized primarily within the inner retina. Sixty minutes of ischemia led to a dramatic reduction in EPO staining 24 h after reperfusion. By 48 h after ischemia, EPO protein levels dropped to 50% as compared with the normal eye. (2) HE staining: In saline group, the inner nuclear layer of retina was slightly thinner and the number of cells was slightly reduced by 12 h after reperfusion. The number of cells in the ganlion cell layer (GCL) was reduced and the inner layer (INL) disorganized by 24 h after reperfusion. The thickness of the inner retina was furtherly thinner and the number of cells was obviously reduced by 48 h after reperfusion. The thickness of the inner retinawas reduced dramatically by 72 h after reperfusion. During all the post-reperfusion stages, the thickness of the retina from inner nuclear layer to inner limiting membrane and the number of cells in the inner nuclear layer and the ganglion cell layer of EPO group were greater than that of the saline group.(3) TUNEL delectation: No positive cells were observed in the normal rats' retinae. In the saline group, the positive cells were observed in the INL and the GCL by 12 h after reperfusion. The number of TUNEL positive cells reached a maximum at the 24 h after reperfusion, maily located in the INL, and followed by a decrease at the 48 h after reperfusion. The expression of positive cells of the EPO group was similar to that of the saline group, but the positive cells were less than that of the saline group.(4) Bcl-2 staining: The positive cells were observed in the INL and GCL by 12 h, 24h after reperfusion in the saline group and the EPO group. By 12 h after reperfusion, the positive staining (33.25±1.87) per 10nm length of INL in the EPO group, (22. 25+1.69) per 10u.m length of INL in the saline group. By 24 h after reperfusion, (25. 27 ± 1. 31) per 10u.m length of INL in the EPO group, (15.16± 1. 89) per lOjim length of INL in the saline group. There was distinct difference between the EPO group and saline group(P<0. 01) .(5) Fas staining: No positive cells were observed in the normal rats' retinae. The expression of Fas of the saline group gradually increased as early as when it was at the 12 h after reperfusion, reached a peak at the 24 h after reperfusion, and then decreased at the 48 h after reperfusion. The expression of Fas of the EPO group was similar to that of the saline group, but it is less during all the post-reperfusion stages.(6) FasL staining: The expression of FasL of the saline group gradually increased as early as when it was at the 12 h after reperfusion, reached a peak at the 24 h after reperfusion, and then decreased at the 48 h after reperfusion. The expression of FasL of the EPO group was similar to that of the saline group, but it is less during all the post-reperfusion stages.(7) Caspase-2 staining: No positive cells were observed in the normal rats' retinae. By 12 h after reperfusion, the positive staining (31.25±1.67) per 100u,m length of GCL in the...