慢性高眼压大鼠视网膜神经胶质细胞组织病理学改变

目的 研究青光眼视网膜神经胶质细胞组织病理学改变及其在青光眼视网膜神经节细胞损伤中的作用机制.方法 对照实验研究.选用造模成功的慢性高眼压雄性SD大鼠72只,眼压＞22 mm Hg(1 mm Hg=0.133 kPa).右眼为慢性高眼压眼,左眼为假手术对照眼.根据慢性高眼压模型建立的时间(手术结束时开始计算),将实验鼠分为6组(2、12 h,1 d,1、4、8周),每组12只鼠.正常组SD大鼠12只,平均眼压12.56 mm Hg.分别取实验各组(慢性高眼压)、假手术组及正常组大鼠4只眼球,冰冻切片行胶质纤维酸性蛋白(GFAP)免疫组织化学染色,在激光共焦显微镜下观察视网膜星形胶质细胞及Müller细胞的GFAP表达情况;分别取实验各组(慢性高眼压)和正常组大鼠4只眼球,在视网膜铺片上进行GFAP免疫组织化学染色,进行星形胶质细胞计数并观察其形态;分别取实验各组(慢性高眼压)、假手术组及正常大鼠4只眼球的鼻侧半视网膜,在视网膜铺片上行小胶质细胞标记物OX42免疫组织化学染色,进行小胶质细胞计数并观察其形态;取剩余的颢侧中周部视网膜,半薄切片行甲苯胺蓝染色并进行Müller细胞计数.对不同时间点慢性高眼压组与正常组大鼠细胞表达数最进行比较,采用单因素多水平设计定量资料的方差分析.结果 慢性高眼压模型建立后2 h,即有活化的小胶质细胞出现;1 d后小胶质细胞的数量开始增加,为(327.40±68.32)个/mm2;1周后小胶质细胞的数量达到高峰,为(965.06±86.63)个/mmw,与正常组小胶质细胞数最比较,差异有统计学意义(F=196.56,P＜0.01);其后小胶质细胞数量逐渐减少.慢性高眼压模型建立后12 h,星形胶质细胞及Müller细胞开始呈现活化状态;4周时两种细胞的活化程度达到高峰,以后活化程度逐渐下降,且活化的星形胶质细胞在结构上出现明显异常,表现为星形胶质细胞突起变得粗短、僵硬,胞体的星型结构破坏;但慢性高眼压组视网膜星形胶质细胞及Müller细胞数量与正常组相比,差异均无统计学意义(F=1.36,1.89;均P＞0.05).结论 在慢性高眼压条件下,小胶质细胞可能是视网膜最早发生病理学改变的组织;活化的星形胶质细胞可出现明显的形态和结构变化,其结果不仅将加速神经节细胞的损伤,同时也会形成不利于神经节细胞轴突再生的视网膜微环境.

Pathological changes of retinal glial cells in a rat chronic ocular hypertension model

Objective To study the pathological changes of retinal glial cells and its effect on retinal ganglion cells (RGC) damage in a rat chronic ocular hypertension model. Methods Seventy-two of Sprague-Dawley (SD) rats with chronic elevated intraocular pressure (IOP) by ligating two superior or inferior episcleral veins were used in this study. Twelve normal rats served as control. The densities of glial cells were determined in flat mounted or transverse semithin sections of retinas, microglial cells were visualized by OX42 staining on whole-mounted retinas, and Muller cells were detected by expressing glial fibrillary acidic protein (GFAP) on frozen section or flat mounted retinas with confocal microscopy at 2 hours, 12 hours, 1 day, 1 week, 4 weeks, and 8 weeks after operation, respectively. Results Compared with control group, the densities of activated microglial cells were significantly ( F = 196. 56, P < 0. 01 )increased at 1 day (215.00±18.60 vs 327. 40±68. 32/mm2) and reached a peak value at 1 week ( 965.06±86. 63/mm2), then decreased gradually. But the densities of astrocytes and Muller cells were notsignificantly changed (F = 1.36, 1.89 ; P>0. 05 ) at all time points. The activated microglial cells were appeared at 2 hour while the activated Muller cells and astrocytes presented at 12 hours after operation. The activated Muller cells and astrocytes reached a peak value at 4 weeks, and then decreased gradually. The activated astrocyte had morphological changes including disappeared star-structure of cell body, stiffness,and shortness of cell processes. Conclusions The alteration of microglial cell densities appears to be the earliest pathological changes of retina in rat with chronic ocular hypertension. The activated astrocytes with morphological disorder may deteriorate the damage of RGC and result in a harmful microenvironment for axonal regeneration of RGC in glaucoma.