Departamento de Oftalmología, Facultad de Medicina, Campus Universitario de Espinardo, Universidad de Murcia, 30100 Espinardo, Murcia, Spain.
Exp Eye Res. 2010 Jan;90(1):168-83. doi: 10.1016/j.exer.2009.10.003. Epub 2009 Oct 14.
Ocular hypertension (OHT) is the main risk factor of glaucoma, a neuropathy leading to blindness. Here we have investigated the effects of laser photocoagulation (LP)-induced OHT, on the survival and retrograde axonal transport (RAT) of adult rat retinal ganglion cells (RGC) from 1 to 12 wks. Active RAT was examined with fluorogold (FG) applied to both superior colliculi (SCi) 1 wk before processing and passive axonal diffusion with dextran tetramethylrhodamine (DTMR) applied to the optic nerve (ON) 2 d prior to sacrifice. Surviving RGCs were identified with FG applied 1 wk pre-LP or by Brn3a immunodetection. The ON and retinal nerve fiber layer were examined by RT97-neurofibrillar staining. RGCs were counted automatically and color-coded density maps were generated. OHT retinas showed absence of FG+ or DTMR+RGCs in focal, pie-shaped and diffuse regions of the retina which, by two weeks, amounted to, approximately, an 80% of RGC loss without further increase. At this time, there was a discrepancy between the total number of surviving FG-prelabelled RGCs and of DMTR+RGCs, suggesting that a large proportion of RGCs had their RAT impaired. This was further confirmed identifying surviving RGCs by their Brn3a expression. From 3 weeks onwards, there was a close correspondence of DTMR+RGCs and FG+RGCs in the same retinal regions, suggesting axonal constriction at the ON head. Neurofibrillar staining revealed, in ONs, focal degeneration of axonal bundles and, in the retinal areas lacking backlabeled RGCs, aberrant staining of RT97 characteristic of axotomy. LP-induced OHT results in a crush-like injury to ON axons leading to the anterograde and protracted retrograde degeneration of the intraocular axons and RGCs.
眼压升高（OHT）是青光眼的主要危险因素，青光眼是一种导致失明的神经病变。在这里，我们研究了激光光凝（LP）诱导的 OHT 对成年大鼠视网膜神经节细胞（RGC）的存活和逆行轴突运输（RAT）的影响，时间范围从 1 周到 12 周。使用荧光金（FG）在处理前 1 周应用于上丘（SCi）来检查活性 RAT，并用葡聚糖四甲基罗丹明（DTMR）在牺牲前 2 天应用于视神经（ON）来进行被动轴突扩散。存活的 RGC 用 FG 在 LP 前 1 周应用或用 Brn3a 免疫检测来识别。通过 RT97-神经纤维染色检查 ON 和视网膜神经纤维层。RGC 自动计数，并生成彩色编码密度图。OHT 视网膜在视网膜的局灶性、饼状和弥漫性区域显示 FG+或 DTMR+RGC 的缺失，两周后，大约有 80%的 RGC 丢失，且无进一步增加。此时，存活的 FG 标记的 RGC 总数和 DMTR+RGC 之间存在差异，表明大部分 RGC 的 RAT 受损。通过识别 Brn3a 表达的存活 RGC 进一步证实了这一点。从 3 周开始，在同一视网膜区域，DTMR+RGCs 和 FG+RGCs 之间有密切的对应关系，提示 ON 头部的轴突收缩。神经纤维染色显示，在 ON 中，轴突束出现局灶性变性，在缺乏回溯标记的 RGC 的视网膜区域，RT97 出现异常染色，这是轴突切断的特征。LP 诱导的 OHT 导致 ON 轴突类似挤压的损伤，导致眼内轴突和 RGC 的顺行和进行性逆行变性。
