In vivo imaging and counting of rat retinal ganglion cells using a scanning laser ophthalmoscope

PURPOSE: To determine whether a scanning laser ophthalmoscope (SLO) is useful for in vivo imaging and counting of rat retinal ganglion cells (RGCs). METHODS: RGCs of Brown Norway rats were retrogradely labeled bilaterally with the fluorescent dye 4-(4-(dihexadecylamino)styryl)-N-methylpyridinium iodine (DiA). The unilateral optic nerve was crushed intraorbitally with a clip. RGCs were imaged in vivo with an SLO with an argon blue laser (488 nm) and optical filter sets for fluorescein angiography, before and 1, 2, and 4 weeks after the crush. Fluorescent cells were also counted in retinal flatmounts at baseline and 1, 2, and 4 weeks after the crush. An image overlay analysis was performed to check cell positions in the SLO images over time. Lectin histochemical analysis was performed to determine the relationship of microglia to the newly emerged DiA fluorescence detected by image overlay analysis after the optic nerve crush. RESULTS: Fluorescent RGCs were visible in vivo with an SLO. RGC survival decreased gradually after the crush. In the retina after the optic nerve crush, newly emerged DiA fluorescence detected by image overlay analysis corresponded to fluorescent cells morphologically different from RGCs in the retinal flatmount and was colocalized mostly with lectin-stained microglial processes. RGC counts by SLO were comparable to those in retinal flatmounts. CONCLUSIONS: The SLO is useful for in vivo imaging of rat RGCs and therefore may be a valuable tool for monitoring RGC changes over time in various rat models of RGC damage.     

A new calcium channel antagonist, lomerizine, alleviates secondary retinal ganglion cell death after optic nerve injury in the rat

PURPOSE: We investigated whether lomerizine, a new diphenylmethylpiperazine calcium channel blocker, exerted a neuroprotective effect on axonal or retinal damage induced by optic nerve injury in the rat. METHODS: A partial crush lesion was inflicted unilaterally on the optic nerve, 2 mm behind the globe, in adult Wistar albino rats. Animals were treated with the vehicle, 10 or 30 mg/kg lomerizine. Each solution was given orally twice daily for 4 weeks. One week before euthanization, Fluoro-Gold (FG) was injected into both superior colliculi to retrogradely label surviving retinal ganglion cells (RGCs). Approximately 1 month after the optic nerve injury, the retinal damage was assessed morphologically, and the optic nerve axons surrounding the initial lesion were examined histologically. RESULTS: The mean RGC density in the control group decreased to 65.9 +/- 1.32% of the contralateral eye, whereas the systemic application of 10 or 30 mg/kg of lomerizine significantly enhanced the RGC survival to 88.1 +/- 0.38% and 89.8 +/- 0.28%, respectively. Histological examination of damaged axons revealed no significant enhancement of the density or total number of axons of the retinal ganglion cells in the lomerizine-treated group. The crush force we employed caused no significant morphological differences in the retinal layers between the sham-operated animals and the animals from the experimental groups. CONCLUSIONS: Our findings suggest that lomerizine alleviates secondary degeneration of RGCs induced by an optic nerve crush injury in the rat, presumably by improving the impaired axoplasmic flow.     

Retinal ganglion cell axotomy induces an increase in intracellular superoxide anion

PURPOSE: Retinal ganglion cells (RGCs) undergo apoptosis after axonal injury. The time course of cell death is variable and depends in part on the degree of injury sustained. Decreasing reactive oxygen species (ROS) levels or shifting the redox state to reduction promotes the survival of RGCs in tissue culture after axotomy. It was hypothesized that a specific ROS, superoxide anion, acts as an intracellular signaling molecule for RGC death after axotomy. METHODS: Intracellular superoxide levels were measured after dissociation in retrograde-labeled rat RGCs with use of the superoxide-sensitive fluorophores hydroethidium and MitoSOX Red. Having found a significant increase, the effect of axotomy was determined on superoxide levels independent of dissociation with an optic nerve crush model. RESULTS: Optic nerve crush caused RGCs to undergo a superoxide burst. The burst was asynchronous and was manifested in only a fraction of cells at any given time. Neurotrophin deprivation was not responsible for the superoxide burst because it was not prevented by incubation with the neurotrophic factors brain-derived neurotrophic factor, ciliary neurotrophic factor, forskolin, or insulin. Several inhibitors of intracellular superoxide generation were studied, but only antimycin A, which inhibits complex III of the mitochondrial electron transport chain, blocked the increase in superoxide. CONCLUSIONS: These findings suggest that superoxide generated in the mitochondrial electron transport chain could be a parallel system to neurotrophic deprivation for signaling cell death after axonal injury.     

Neuroprotective effect of latanoprost on rat retinal ganglion cells

Background To investigate the neuroprotective effect of intravitreal administration of latanoprost on retinal ganglion cell (RGC) damage induced by N-methyl-D-aspartic acid (NMDA) or optic nerve axotomy.Methods Using Sprague-Dawley rats, retinal ganglion cell damage was induced by either intravitreal administration of NMDA or optic nerve axotomy. Latanoprost at doses of 0.03, 0.3, 3, 30 and 300 pmol was administered intravitreally before NMDA injection or optic nerve axotomy. Retinal damage was evaluated by counting the number of surviving RGCs retrogradely labeled with fluorogold under the microscope.Results Seven days after the NMDA injury, the number of surviving RGCs was significantly increased at doses of more than 30 pmol atanoprost (846±178 cells/mm² P=0.0166) compared with vehicle control (556±122 cells/mm²). Ten days after the optic nerve axotomy, the number of surviving RGC was significantly increased even at a dose of 0.3 pmol (815±239 cells/mm², P=0.0359) compared with control (462±75 cells/mm²).Conclusions Intravitreal administration of latanoprost has a neuroprotective effect on rat RGC damage induced by either NMDA or optic nerve axotomy, while its pharmacological features are different.     

视网膜下移植睫状神经营养因子编码基因修饰的细胞保护SD大鼠视神经横断伤后视网膜节细胞变性

目的探讨移植表达睫状神经营养因子(CNTF)的细胞对SD大鼠视神经横断伤后视网膜节细胞的保护作用。方法通过脂质体将CNTF表达质粒转移至人胚肺成纤维细胞,建立稳定、高水平表达CNTF的细胞株。采用双侧背外侧膝状体及上丘核团注射3%荧光金逆行标记视网膜节细胞。将标记后的大鼠分为两组,于标记后7d手术切断眶内段视神经其中一组左眼不做手术作为正常对照组,右眼切断视神经作为手术对照组;另一组双眼均手术切断视神经,左眼注射PBS作为治疗对照组,右眼视网膜下移植表达CNTF的细胞作为实验组。术后5、14、17、21及28d取出眼球,铺片后荧光显微镜观察并计数视网膜内存活的节细胞。结果手术切断眶内段视神经后2周,视网膜内节细胞数减少6744%,视网膜下移植表达CNTF的细胞后第5、17、21d视网膜内存活的节细胞数明显多于治疗对照组(P<005)。结论视网膜下移植高水平表达CNTF的细胞对视网膜节细胞有保护作用。     

Protection of retinal ganglion cells against optic nerve injury by induction of ischemic preconditioning

AIM: To explore if ischemic preconditioning (IPC) can enhance the survival of retinal ganglion cells (RGCs) after optic nerve axotomy. METHODS: Twenty-four hours prior to retinal ischemia 60min or axotomy, IPC was applied for ten minutes in groups of (n=72) animals. The survival of RGCs, the cellular expression of heat shock protein 27 (HSP27) and heat shock protein 70 (HSP70) and the numbers of retinal microglia in the different groups were quantified at 7 and 14d post-injury. The cellular expression of HSP27 and HSP70 and changes in the numbers of retinal microglia were quantified to detect the possible mechanism of the protection of the IPC. RESULTS: Ten minutes of IPC promoted RGC survival in both the optic nerve injury (IPC-ONT) and the retinal ischemia 60min (IPC-IR60) groups, examined at 7d and 14d post-injury. Microglial proliferation showed little correlation with the extent of benefit effects of IPC on the rescue of RGCs. The number of HSP27-positive RGCs was significantly higher in the IPC-ONT group than in the sham IPC-ONT group, although the percentage of HSP27-positive RGCs did not significantly differ between groups. For the IPC-IR60 group, neither the number nor the percentage of the HSP27-positive RGCs differed significantly between the IPC and the sham-operated groups. The number of HSP70-positive RGCs was significantly higher for both the IPC-ONT and the IPC-IR60 experimental groups, but the percentages did not differ. CONCLUSION: The induction of IPC enhances the survival of RGCs against both axotomy and retinal ischemia.     

大鼠视神经损伤视网膜病理改变的实验研究

目的研究现神经损伤早期视网膜的病理改变。方法采用大鼠球后视神经横断伤和钳夹伤模型,观察视网膜组织学及超微结构的改变。结果1）光镜：早期表现为神经纤维层血管扩张,损伤后7、14天可见散在的核染色质边聚。空化的节细胞。2）电镜：损伤后1天节细胞出现胞浆成分疏松,内质网扩张等变性样改变,横断伤3天及钳夹伤7天可见节细胞坏死,部分节细胞凋亡。结论视神经损伤导致节细胞出现迟发性死亡,提示早期治疗具有重要意义。     

Superoxide signaling and cell death in retinal ganglion cell axotomy: effects of metallocorroles

Injury to retinal ganglion cell (RGC) axons within the optic nerve causes apoptosis of the soma. We previously demonstrated that in vivo axotomy causes elevation of superoxide anion within the RGC soma, and that this occurs 1-2 days before annexin-V positivity, a marker of apoptosis. Pegylated superoxide dismutase delivery to the RGC prevents the superoxide elevation and rescues the soma. Together, these results imply that superoxide is an upstream signal for apoptosis after axonal injury in RGCs. We then studied metallocorroles, potent superoxide dismutase mimetics, which we had shown to be neuroprotective in vitro and superoxide scavengers in vivo for RGCs. RGCs were retrograde labeled with the fluorescent dye 4Di-10Asp, and then axotomized by intraorbital optic nerve transection. Iron(III) 2,17-bis-sulfonato-5,10,15-tris(pentafluorophenyl)corrole (Fe(tpfc)(SO(3)H)(2)) (Fe-corrole) was injected intravitreally. Longitudinal imaging of RGCs was performed and the number of surviving RGCs enumerated. There was significantly greater survival of labeled RGCs with Fe-corrole, but the degree of neuroprotection was relatively less than that predicted by their ability to scavenge superoxide-This implies an unexpected complexity in signaling of apoptosis by reactive oxygen species.     

RGC death in mice after optic nerve crush injury: oxidative stress and neuroprotection

PURPOSE: To establish a method for morphometric analysis of retrogradely labeled retinal ganglion cells (RGCs) of the mouse retina, to be used for the study of molecular aspects of RGC survival and neuroprotection in this model; to evaluate the effect of overexpression of Cu-Zn-superoxide dismutase (CuZnSOD) on RGC survival after severe crush injury to the optic nerve, and to assess the effect of the alpha2-adrenoreceptor agonist brimonidine, recently shown to be neuroprotective, on RGC survival. METHODS: A severe crush injury was inflicted unilaterally in the orbital portion of the optic nerves of wild-type and transgenic (Tg-SOD) mice expressing three to four times more human CuZnSOD than the wild type. In each mouse all RGCs were labeled 72 hours before crush injury by stereotactic injection of the neurotracer dye FluoroGold (Fluorochrome, Denver, CO) into the superior colliculus. Survival of RGCs was then assessed morphometrically, with and without systemic injection of brimonidine. RESULTS: Two weeks after crush injury, the number of surviving RGCs was significantly lower in the Tg-SOD mice (596.6 +/- 71.9 cells/mm(2)) than in the wild-type control mice (863. 5 +/- 68 cells/mm(2)). There was no difference between the numbers of surviving RGCs in the uninjured retinas of the two strains (3708 +/- 231.3 cells/mm(2) and 3904 +/- 120 cells/mm(2), respectively). Systemic injections of brimonidine significantly reduced cell death in the Tg-SOD mice, but not in the wild type. CONCLUSIONS: Overexpression of CuZnSOD accelerates RGC death after optic nerve injury in mice. Activation of the alpha2-adrenoreceptor pathway by brimonidine enhances survival of RGCs in an in vivo transgenic model of excessive oxidative stress.     

Tracking retinal microgliosis in models of retinal ganglion cell damage

Purpose. To investigate the longitudinal profiles of microgliosis after optic nerve injury induced by optic nerve crush and acute elevation of intraocular pressure (IOP). Methods. A confocal scanning laser ophthalmoscope was used to image the retinal microglia of the CX3CR1(GFP/+) transgenic mice in vivo at baseline, 3 days and then weekly for 4 weeks after optic nerve crush (n = 3), and after elevating the IOP to 110 mm Hg for 30 (n = 3) or 60 (n = 3) minutes. Results. After optic nerve crush, the density of microglia increased by 2.43 ± 0.19-fold at week 1 and then gradually declined with 2.04 ± 0.24-, 1.69 ± 0.25-, and 1.29 ± 0.11-fold increases at week 2, 3, and 4, respectively. Microgliosis followed a similar pattern after acute IOP elevation and the increase in microglia was associated with the duration of IOP elevation. There were 1.35 ± 0.17- and 2.03 ± 0.08-fold increases in microglia at week 1, and 1.15 ± 0.11- and 1.11 ± 0.10-fold increases at week 4, after 30 and 60 minutes of acute IOP elevation, respectively. The morphology of microglia changed from ramified to ameboid form in 1 week, and then returned to ramified form in the subsequent weeks. There was a significant negative association between the number of surviving retinal ganglion cells (RGCs) and the extent of microgliosis during the follow-up period (R(2) = 0.72, P = 0.004). Conclusions. Longitudinal in vivo imaging of the retinal microglia can provide an effective approach to study microgliosis and its association with RGC degeneration.     

表没食子儿茶素没食子酸酯对大鼠视神经钳夹伤后视网膜神经节细胞的保护作用

　　目的　观察绿茶提取物表没食子儿茶素没食子酸酯(EGCG)对大鼠视神经钳夹伤视网膜神经节细胞（RGC）是否具有保护作用。方法　72只Wistar大鼠随机分为正常对照组（A组）、假手术+EGCG组（B组）、视神经钳夹+生理盐水组（C组）、视神经钳夹+EGCG组（D组）等4组,每组各18只。B、D组在视神经钳夹或假手术前2 d起给予腹腔注射EGCG  25 mg/（kg·d）,直至手术后2 d,共5 d;随后改为口服2 mg/（kg·d）。C组以生理盐水替代EGCG。每次每组取6只大鼠,采用3%荧光金经上丘逆行标记RGC方法,比较各组视神经钳夹伤后7、14、28 d RGC的存活数量;采用免疫组织化学染色及蛋白免疫印迹方法检测各组视神经组织神经丝蛋白（NF-L）的表达。结果　视神经钳夹伤后7 d,C、D组RGC存活数量分别为（943.61±85.06）、（1 134.45±117.85） 个/mm2;14 d时分别为（812.76±172.07）、（1 021.67±94.02） 个/mm2;28 d时分别为（766.94±171.45）、（1 009.72±126.40）个/mm2。各时间点D组RGC存活数量均显著高于C组（t=3.216,2.609,2.792;P=0.009,0.026,0.019）。各时间点A、B组间RGC存活数量差异无统计学意义（t=0.749,0.403,0.254;P值均＞0.05）;视神经钳夹后7、14、28 d,D组视神经组织NFL表达均高于C组（t=9.847,5.731,2.868;P=0.001,0.005,0.045）。结论　EGCG对大鼠视神经钳夹伤后RGC具有一定的保护作用。      

Reduced retina microglial activation and improved optic nerve integrity with minocycline treatment in the DBA/2J mouse model of glaucoma

PURPOSE: In the context of the retinal ganglion cell (RGC) axon degeneration in the optic nerve that occurs in glaucoma, microglia become activated, then phagocytic, and redistribute in the optic nerve head. The authors investigated the potential contribution of retinal microglia activation to glaucoma progression in the DBA/2J chronic mouse glaucoma model. METHODS: The authors treated 6-week-old DBA/2J mice for 25 weeks with minocycline, a tetracycline derivative known to reduce microglia activation and to improve neuronal survival in other models of neurodegenerative disease. They quantified RGC numbers and characterized microglia activation, gliosis, and both axonal integrity and retrograde tracer transport by RGCs in mice systemically treated with minocycline or vehicle only. RESULTS: Minocycline reduced microglial activation and improved RGC axonal transport and integrity, yet it had no effect on the characteristic age-related ocular changes that lead to chronically elevated pressure and did not alter Müller or astrocyte gliosis. Specifically, minocycline increased the fraction of microglia with resting ramified morphology and reduced levels of Iba1 mRNA and protein, a microglia-specific calcium ligand linked to activation. The reduction in microglial activation was coupled to significant improvement in RGC axonal transport, as measured by neuronal retrograde tracing from the superior colliculus. Finally, minocycline treatment significantly decoupled RGC axon loss from increased intraocular pressure. CONCLUSIONS: These observations suggest that in glaucoma, retina and optic nerve head microglia activation may be a factor in the early decline in function of the optic nerve and its subsequent degeneration.     

Experimental induction of retinal ganglion cell death in adult mice

PURPOSE: Retinal ganglion cells die by apoptosis during development and after trauma such as axonal damage and exposure to excitotoxins. Apoptosis is associated with changes in the expression of genes that regulate this process. The genes that regulate apoptosis in retinal ganglion cells have not been characterized primarily because previous studies have been limited to animal models in which gene function is not easily manipulated. To overcome this limitation, the rate and mechanism of retinal ganglion cell death in mice was characterized using optic nerve crush and intravitreal injections of the glutamate analog N-methyl-D-aspartate (NMDA). METHODS: To expose retinal ganglion cells (RGCs) to excitotoxins, adult CB6F1 mice were injected intravitreally in one eye with NMDA. In an alternative protocol to physically damage the axons in the optic nerve, the nerve was crushed using self-closing fine forceps. Each animal had one or the other procedure carried out on one eye. Loss of RGCs was monitored as a percentage of cells lost relative to the fellow untreated eye. Thy1 expression was examined using in situ hybridization. DNA fragmentation in dying cells was monitored using terminal transferase-dUTP nick-end labeling (TUNEL). RESULTS: RGCs comprise 67.5% +/- 6.5% (mean +/- SD) of cells in the ganglion cell layer (GCL) of control mice based on nuclear morphology and the presence of mRNA for the ganglion cell marker Thy1. One week after optic nerve crush, these cells started to die, progressing to a maximum loss of 57.8% +/- 8.1% of the cells in the GCL by 3 weeks. Cell loss after NMDA injection was dose dependent, with injections of 10 nanomoles having virtually no effect to a maximum loss of 72.5% +/- 12.1% of the cells in the GCL within 6 days after injection of 160 nanomoles NMDA. Cell death exhibited features of apoptosis after both optic nerve crush and NMDA injection, including the formation of pyknotic nuclei and TUNEL staining. CONCLUSIONS: Quantitative RGC death can be induced in mice using two distinct signaling pathways, making it possible to test the roles of genes in this process using transgenic animals.     

A model to study differences between primary and secondary degeneration of retinal ganglion cells in rats by partial optic nerve transection

PURPOSE: To use a rat model of optic nerve injury to differentiate primary and secondary retinal ganglion cell (RGC) injury. METHODS: Under general anesthesia, a modified diamond knife was used to transect the superior one third of the orbital optic nerve in albino Wistar rats. The number of surviving RGC was quantified by counting both the number of cells retrogradely filled with fluorescent gold dye injected into the superior colliculus 1 week before nerve injury and the number of axons in optic nerve cross sections. RGCs were counted in 56 rats, with 24 regions examined in each retinal wholemount. Rats were studied at 4 days, 8 days, 4 weeks, and 9 weeks after transection. The interocular difference in RGCs was also compared in five control rats that underwent no surgery and in five rats who underwent a unilateral sham operation. It was confirmed histologically that only the upper optic nerve had been directly injured. RESULTS: At 4 and 8 days after injury, superior RGCs showed a mean difference from their fellow eyes of -30.3% and -62.8%, respectively (P = 0.02 and 0.001, t-test, n = 8 rats/group), whereas sham-operation eyes had no significant loss (mean difference between eyes = 1.7%, P = 0.74, t-test). At 8 days, inferior RGCs were unchanged from control, fellow eyes (mean interocular difference = -4.8%, P = 0.16, t-test). Nine weeks after transection, inferior RGC had 34.5% fewer RGCs than their fellow eyes, compared with 41.2% fewer RGCs in the superior zones of the injured eyes compared with fellow eyes. Detailed, serial section studies of the topography of RGC axons in the optic nerve showed an orderly arrangement of fibers that were segregated in relation to the position of their cell bodies in the retina. CONCLUSIONS: A model of partial optic nerve transection in rats showed rapid loss of directly injured RGCs in the superior retina and delayed, but significant secondary loss of RGCs in the inferior retina, whose axons were not severed. The findings confirm similar results in monkey eyes and provide a rodent model in which pharmacologic interventions against secondary degeneration can be tested.     

金丝桃素对视神经损伤大鼠视网膜节细胞的保护作用

目的观察金丝桃素对视神经损伤大鼠视网膜节细胞的保护作用。方法24只SD大鼠随机分为正常对照组、单纯夹伤组、生理盐水对照组、金丝桃素治疗组4组,每组6只（12眼）。对所有大鼠行双上丘注射2％荧光金逆行标记节细胞,7d后,对单纯夹伤组、生理盐水对照组、金丝桃素治疗组进行球后视神经钳夹．同时在生理盐水对照组、金丝桃素治疗组玻璃体内分别注入生理盐水和金丝桃素5ul,14d后进行视网膜节细胞的计数。采用SPSS13．0统计软件对所得数据进行t检验。结果视神经夹伤后14d,存活的视网膜节细胞显著减少。单纯夹伤组节细胞存活率为50％,生理盐水对照组节细胞存活率为52％,金丝桃素治疗组节细胞存活率为68％。金丝桃素治疗组相比单纯夹伤组和生理盐水对照组,存活的节细胞明显要多（P〈0．05）。结论玻璃体内注射金丝桃素能减少大鼠视神经损伤后视网膜神经节细胞的死亡率．对视网膜节细胞有保护作用。     

饱和氢气水对大鼠视神经夹伤模型视网膜神经节细胞保护作用的实验研究

 目的 探索饱和氢气水对大鼠视神经夹伤模型视网膜神经节细胞（RGC）的保护作用。设计 实验研究。研究对象 SPF级SD大鼠18只。方法 对18只大鼠采用随机数表法随机分为3组,每组6只。均选取右眼为实验眼,左眼为正常对照眼。使用40 g微型视神经夹在大鼠视神经球后2 mm处夹持60 s建立视神经夹伤模型。A组给予饱和氢气水腹腔注射,5 ml/kg,每日1次;B组和C组分别给予饱和氢气水和生理盐水滴眼,每次1滴,每日3次。用药第9天,麻醉下采用3%荧光金双上丘两点注射法逆行标记大鼠RGC,第14天深麻醉下取眼球并处死动物,行视网膜定向铺片,距离视乳头中心上下左右各2 mm 拍摄照片,盲法计数RGC。主要指标 RGC存活率。结果 A组、B组和C组RGC存活率分别为40.35%±13.04%、58.34%±14.00%和43.07%±7.80%（F=3.965, P=0.041）。其中B组与A组和C组之间均有显著性差异（P=0.020;P=0.042）;A组和C组之间无显著性差异（P=0.698）。结论 饱和氢气水滴眼2周对大鼠视神经夹伤模型视网膜神经节细胞可能具有一定的保护作用。（眼科,2014, 23： 107-110）     

大鼠视神经压榨伤模型的建立

目的建立大鼠标定性视神经损伤模型.方法健康SD大鼠28只,7只为正常对照组,只进行双上丘注射3%快蓝逆行标记视网膜神经节细胞(retinal ganglion cells,RGCs),另21只为标定性视神经损伤组,依损伤后存活时间的不同再分为A组(4d组)、B组(14d组)及C组(21d组),每组7只.21只大鼠以夹持力为40 g的特制视神经夹,在大鼠眼球后2 mm处夹持视神经4s,制成大鼠标定性视神经压榨伤模型,于处死前3d采用双上丘直接注射3%快蓝(fast blue)法标记双眼RGCs,将全视网膜铺片置于荧光显微镜下,在距视乳头1 mm处的颞上、颞下、鼻下、鼻上4处作荧光摄影(400 ×),并输入计算机经图像分析仪计数RGCs,按RGCs标识率进行统计学比较.RGCs标识率=损伤眼(右眼)RGCs数/未损伤眼(左眼)RGCs数×100%.结果正常大鼠的RGCs标识率右眼RGCs数/左眼RGCs数为99.79%±13.05%,左眼RGCs数/右眼RGCs数为101.86%±13.91%,无论是用左眼的RGCs数比右眼的RGCs数,或用右眼的RGCs数比左眼的RGCs数,其结果无显著性差异(P＞0.5).视神经损伤组的RGCs标识率A组(4d组)RGCs标识率为77.79%±7.11%;B组(14d组)RGCs标识率为63.76%±3.79%;C组(21d组)RGCs标识率为54.66%±4.75%.以上显示,损伤各组的RGCs标识率明显低于正常对照组(P＜0.05),且随着时间的推移,损伤A、B、C组的RGCs标识率渐进性降低.结论用特制的夹持力为40 g的视神经夹,夹持正常大鼠视神经4s,可造成部分性RGCs丧失,随大鼠存活时间的推移,RGCs呈渐进性丧失.眼科学报2001;1799～102.     

Intrinsic survival mechanisms for retinal ganglion cells

Retinal ganglion cells (RGCs) undergo programmed cell death (apoptosis) after axonal injury. This cell death is mediated by several mechanisms, including deprivation of neurotrophic factors, alterations in gene expression, and production of reactive oxygen species. However, death of RGCs is delayed after axonal injury, and a significant number survive even after several days. This suggests that RGC death is not an immediate result of axonal injury, and that other pro-survival factors may play a role. While we and other researchers have focused on the mechanisms of cell death after axonal injury, it may be that determining the regulation of cell survival mechanisms may lead to innovative methods for neuroprotection. The final common pathway of glaucomatous optic neuropathy is RGC death, probably via damage to their axons occurring at or near the lamina cribrosa. Axonal injury leads directly (1) or indirectly (2) to the death of retinal ganglion cells. We and others have demonstrated that axotomy is associated with RGC apoptosis (3-7) as well as specific changes in expression of certain genes at the mRNA and protein level (8, 9). Reactive oxygen species may also be part of the pathway for RGC death (10, 11). We therefore hypothesize that axotomy leads to molecular events that are potentially destructive to RGCs, but also induces changes that are potentially protective against cellular injury. If this is the case, then RGC death from axonal injury would result not only from initiation of apoptosis, but also from failure of intrinsic neuroprotective mechanisms. It should therefore be theoretically possible to modulate these two classes of responses, and thus improve RGC cell survival after axotomy.