内源性促红细胞生成素对大鼠脱离视网膜光感受器细胞的保护作用

摘要

背景 促红细胞生成素(EPO)对多种视网膜疾病模型中视网膜神经元具有一定的保护作用,但EPO对视网膜脱离(RD)后光感受器细胞是否具有保护作用尚不清楚.目的 探讨内源性EPO对RD状态下光感受器细胞的保护作用及可能机制.方法 利用视网膜下腔注射质量分数1.4%透明质酸钠建立大鼠RD模型,按每组情况各组玻璃体腔内分别单次注射PBS或不同剂量的外源性可溶性EPO受体(EPOsR),采用计算机产生随机数字法将72只SD大鼠随机平均分为正常对照组、RD组、RD+PBS组、RD+EPOsR 2、20、200ng组.分别于造模后3d和14d用过量麻醉法处死大鼠并获得大鼠视网膜标本,采用末端脱氧核苷酸转移酶介导的dUTP缺口末端标记(TUNEL)法检测光感受器细胞的凋亡情况,并分别采用Western blot和免疫荧光法检测视网膜中caspase-3的活性,RD造模后14d进行组织病理学检查并测量外核层(ONL)厚度.结果 RD造模后3d,RD组ONL出现凋亡细胞核,玻璃体腔注射EPOsR组光感受器细胞凋亡进一步增加,随着玻璃体腔注射EPOsR的剂量增加,ONL凋亡细胞核有增加趋势.Western blot和免疫荧光检测结果均显示,各组视网膜caspase-3表达的条带灰度值分别为(0.15±0.04)、(0.49±0.03)、(0.50±0.07)、(0.63±0.03)、(0.69±0.04)、(0.83±0.04),各组的总体差异有统计学意义(F=76.016,P=0.000),RD+EPOsR 200ng组的caspase-3活性均强于其他各组,差异均有统计学意义(P＜0.01).RD造模后14d,正常对照组、RD组、RD+PBS组、RD+EPOsR 2、20、200ng组的ONL厚度分别为(47.39±3.39)、(33.96±3.54)、(31.83±5.21)、(31.40±2.63)、(24.99±2.06)、(19.30±3.71)μm,总体差异有统计学意义(F=44.733;P=0.000);EPOsR处理组ONL厚度明显薄于单纯RD组和RD+PBS组,差异均有统计学意义(P＜0.05).结论 RD状态下,EPOsR通过剂量依赖的方式诱导视网膜细胞的凋亡和caspase-3活性增强,而缺氧状态下视网膜神经上皮的内源性EPO表达增强可通过抑制caspase-3活性和抗凋亡作用发挥对光感受器细胞的保护作用.%Background Erythropoietin (EPO) has a protective effect on retinal neurons in many retinal diseases,but regarding the effect of EPO on apoptosis of retinal photoreceptor cells in retinal detachment (RD) is uncompletely clear.Objective This study was to investigate the protective effect of endogenous EPO on photoreceptors in a rat model of RD and explore its possible mechanism.Methods Seventy-two Sprague- Dawley (SD) rats were randomly assigned to control group,RD group,RD+PBS group,RD+erythropoietin soluble receptor (EPOsR) 2, 20, 200ng groups with 12 rats for each group.1.4% hyaluronic acid was slowly injected into the subretinal space to induce RD in rats,and PBS or 2,20 or 200ng EPOsR was then injected into the vitreous space.On day 3 after RD,apoptotic photoreceptors were detected using transferase-mediated dUTP nickend labeling (TUNEL),and caspase-3 activity was assessed by Western-blot and immunofluorescence staining.On day 14 after RD,retinal histopathologic examination was carried out and outer nuclear layer (ONL) thickness was measured under the light microscope.The use of animals complied with the Statement of Association for Research in Vision and Ophthalmology. Results Apoptotic photoreceptors were seen in ONL of rats of the RD group.Apoptotic photoreceptors were gradually increased with the elevation of EPOsR dose in the vitreous cavity.Western blot and immunofluorescence consistently showed that the gray scale of caspase-3 activity was 0.15±0.04,0.49±0.03,0.50±0.07,0.63±0.03,0.69±0.04 and 0.83±0.04 in the normal group,RD group,RD +PBS group,RD+EPOsR 2,20,200ng groups respectively with statistically significant differences (F=76.016;P=0.000),and caspase-3 activity was considerably stronger in the RD+EPOsR 200ng group than the other groups (P＜0.01).On day 14 after RD,the ONL thicknesses in the normal control group,RD group,RD+PBS group,RD+EPOsR 2,20,200ng groups were (47.39±3.39)μm,(33.96±3.54)μm,(31.83±5.21)μm,(31.40±2.63)μm,(24.99±2.06)μm and (19.30±3.71)μm,showing significant differences among these groups (F=44.733,P=0.000).ONL thicknesses the groups treated with different doses of EPOsR were markedly thinner than that of the RD group and RD +PBS group (P＜0.01).Conclusion EPOsR induces apoptosis of retinal cells and enhances the activity of caspase-3 in a dose-dependent manner.Endogenous EPO can protect photoreceptors against anoxia-mediated damage in RD eyes through decreasing caspase-3 activity and inhibiting apoptosis.