Disruption of the complement cascade delays retinal ganglion cell death following retinal ischemia-reperfusion

Recent reports have indicated that components of the complement cascade are synthesized during the degeneration of retinal ganglion cells (RGC) in glaucoma. While complement deposition in the retina may simply serve to aid phagocytosis of damaged RGC, activation of the complement cascade can also contribute to neuronal loss in neurodegenerative diseases. This study was designed to determine if disruption of the complement cascade affects RGC survival in a murine model of retinal ischemia-reperfusion (I/R) injury. We induced retinal ischemia in the eyes of normal mice and mice with a targeted disruption of the complement component 3 (C3) gene. Tissue was harvested 7 and 21 days after induction of I/R and retinal complement synthesis was determined by quantitative PCR and immunohistochemical methods. RGC death and associated axon loss was evaluated through histological examination of the optic nerve and retina. Our data show that retinal I/R induces the expression and deposition of complement components. C3 deficient mice clearly exhibited reduced optic nerve damage and substantial preservation of RGC 1 week after I/R when compared to normal animals (p = 0.005). Three weeks after the ischemic event C3 deficient mice retained more RGC cell bodies although the degree of optic nerve damage was similar between both groups. These findings demonstrate that inhibition of the complement cascade delays optic nerve axonal and RGC degeneration in retinal I/R. It appears that injured RGC are targeted and actively destroyed through complement mediated processes. These results may have implications for the pathophysiology and clinical management of ischemic retinal conditions.     

急性高眼压对大鼠包含黑视素的视网膜神经节细胞的影响

目的观察高眼压是否会对大鼠包含黑视素的视网膜神经节细胞（mcRGCs）产生损伤。方法利用前房灌注制作急性高眼压诱导的视网膜缺血再灌注模型,利用免疫组织化学法显示mcRGCs及普通神经节细胞,观察其密度的改变。结果急性高眼压后7d,mcRGCs和其他神经节细胞的密度较正常组明显下降,密度分别为（23．36±2．22）、（33．36±1．53）、（3353．02±114．38）个／mm^2和（3952．99±19．92）个／mm^2,存活率分别为67．03％和84．82％。mcRGCs2级及以上的细胞树突分支减少,树突野范围变小,部分损伤严重的细胞只有胞体着色。结论缺血再灌注可以造成大鼠mcRGCs密度下降以及树突分支结构的改变,此类细胞的损伤程度重于其他的神经节细胞的损伤程度。     

促红细胞生成素对大鼠急性缺血视网膜节细胞的保护作用

目的:探讨重组人促红细胞生成素(recombinant human erythropoietin,rhEPO)对大鼠视网膜缺血再灌注损伤(retina ischemia reperfusion injury,RIR)中视网膜神经节细胞(retinal ganglion cell,RGC)的保护作用。方法:成年雌性SD大鼠20只,采用夹闭视网膜动脉30min造成大鼠双眼缺血再灌注模型。所有大鼠均于建模前1h给予左眼rhEPO10U(6μL),右眼给予同等剂量眼用平衡盐液。按照建模后眼球取材时间不同(1,4,7,14d)分为4组,每组5只,均于取材前4d利用荧光金(fluorogold,FG)逆行标记大鼠RGC,视网膜铺片RGC计数,比较双眼存活RGC数量。结果:rhEPO治疗眼RGC存活数多于平衡盐液对照眼。结论:rhEPO对大鼠视网膜急性缺血后RGC具有保护作用。     

Apoptotic retinal ganglion cell death in the DBA/2 mouse model of glaucoma

The DBA/2 mouse has been used as a model for spontaneous secondary glaucoma. We attempted to determine the in vivo time course and spatial distribution of retinal ganglion cells (RGCs) undergoing apoptotic death in DBA/2 mice. Female DBA/2 mice, 3, 9-10, 12, 15, and 18 months of age, received intravitreal injections of Annexin-V conjugated to AlexaFluor 1h prior to euthanasia. Retinas were fixed and flat-mounted. Annexin-V-positive RGCs in the hemiretina opposite the site of injection were counted, and their locations were recorded. Positive controls for detection of apoptotic RGCs by Annexin-V labeling included rats subjected to optic nerve ligation, and C57BL/6 mice subjected to either optic nerve ligation or intravitreal injection of NMDA. To verify that Annexin-V-labeled cells were RGCs, intravitreal Annexin-V injections were also performed on retinas pre-labeled retrogradely with FluoroGold or with DiI. Annexin-V-positive RGC locations were analyzed to determine possible clustering and areas of preferential loss. Annexin-V labeled apoptotic RGCs in eyes after optic nerve ligation, intravitreal NMDA injection, as well as in aged DBA/2 animals. In glaucomatous DBA/2 mice 95-100% of cells labeled with Annexin-V were also FluoroGold- and DiI-positive. This confirms that Annexin-V can be used to specifically detect apoptotic RGCs in rodent retinas. In DBA/2 mice, apoptotic RGC death is maximal from the 12th to the 15th month of age (ANOVA, p<0.001, Fisher's post hoc test) and occurs in clusters. These clusters are initially located in the midperipheral retina and progressively occur closer to the optic nerve head with increasing age. Retrograde axonal transport of FluoroGold in the glaucomatous mouse retina is functional until at least 2-3days prior to initiation of apoptotic RGC death.     

藏红花素对视网膜缺血再灌注损伤小鼠视网膜神经节细胞的保护作用及其机制研究

目的　研究藏红花素对视网膜缺血再灌注损伤（RIRI）小鼠视网膜神经节细胞（RGC）的保护作用及其机制。方法　将144只C57BL/6小鼠随机分为3组:假手术组、模型组、藏红花素治疗组。模型组和藏红花素治疗组小鼠建立RIRI模型,藏红花素治疗组小鼠造模前30 min腹腔注射50 mg·kg^-1藏红花素。RIRI后14 d,视网膜铺片染色比较各组小鼠RGC密度差异。RIRI后24 h,HE染色比较各组小鼠视网膜内层厚度差异。于RIRI后不同时间点（0 h、3 h、6 h、9 h、12 h、15 h）取各组小鼠视网膜组织,通过多重基因定量分析系统检测NLRP3、ASC、Caspase-1、白细胞介素-1β（IL-1β） mRNA的表达变化。RIRI后6 h和12 h取各组小鼠视网膜组织,Western blot检测NLRP3、ASC、Caspase-1、IL-1β蛋白的表达,ELISA检测IL-1β蛋白的含量,并对比分析。结果　小鼠RIRI后14 d,视网膜铺片染色结果显示,藏红花素治疗组较模型组小鼠RGC密度增加约18.5%（P<0.05）。RIRI后24 h,HE染色结果显示,藏红花素治疗组小鼠视网膜内层厚度较模型组显著降低（P<0.01）。多重定量分析系统检测结果显示,RIRI后6 h、9 h及12 h,藏红花素治疗组小鼠视网膜组织中Caspase-1以及IL-1β mRNA表达较模型组均显著降低（均为P<0.05)。Western blot检测结果显示,藏红花素治疗组小鼠视网膜组织中Caspase-1以及IL-1β蛋白表达较模型组均显著降低（均为P<0.05)。RIRI后6 h、12 h,模型组小鼠视网膜组织中NLRP3、ASC mRNA和蛋白表达与假手术组相比无显著变化（均为P>0.05)。ELISA检测结果进一步证实,RIRI后6 h和12 h,藏红花素治疗组小鼠视网膜组织中IL-1β蛋白含量较模型组均显著降低（均为P<0.05)。结论　藏红花素通过抑制Caspase-1和IL-1β表达保护RIRI小鼠RGC。     

Mouse models of retinal ganglion cell death and glaucoma

Once considered too difficult to use for glaucoma studies, mice are now becoming a powerful tool in the research of the molecular and pathological events associated with this disease. Often adapting technologies first developed in rats, ganglion cell death in mice can be induced using acute models and chronic models of experimental glaucoma. Similarly, elevated IOP has been reported in transgenic animals carrying defects in targeted genes. Also, one group of mice, from the DBA/2 line of inbred animals, develops a spontaneous optic neuropathy with many features of human glaucoma that is associated with IOP elevation caused by an anterior chamber pigmentary disease. The advent of mice for glaucoma research is already having a significant impact on our understanding of this disease, principally because of the access to genetic manipulation technology and genetics already well established for these animals.     

Effect of MCI-9042, a 5-HT2 receptor antagonist,on retinal ganglion cell death and retinal ischemia

The neuroprotective effect of MCI-9042 (Mitsubishi Pharma Corporation) was investigated on glutamate-induced retinal ganglion cell (RGC) death in vitro and on rat retinal ischemia in vivo. RGCs were purified from retinal cells isolated from 6-day-old Wistar rats and cultured in serum-free media. After application of 25 microM glutamate, the viability of RGCs treated with or without several serotonin 2 (5-HT(2)) receptor antagonists: MCI-9042, M-1 (a major metabolite of MCI-9042), ketanserin, and LY-53857; was evaluated by calcein-acetoxymethyl ester staining. Retinal ischemia was induced by intraocular pressure (IOP) elevation (130 mmHg, 50 min). Rats were intraperitoneally injected with MCI-9042 at a dose of 3, 30 mg/kg or base at 30 min before and just after ischemia-reperfusion. Retinal damages were evaluated by histology, morphometric analysis and electroretinograms (ERGs) recordings at 7 days after ischemia-reperfusion. 25 microM glutamate decreased the number of viable RGCs to about 60 to 65% of untreated RGCs. MCI-9042, M-1, ketanserin, and LY-53857 significantly reduced glutamate-induced RGC death at concentrations of more than 100 nM, 1 nM, 1 microM and 100 nM, respectively. Ischemia-reperfusion caused thinning of the thickness between the inner plexiform layer and the outer plexiform layer and attenuation of a-and b-waves in ERG recordings. The intraperitoneal injection of MCI-9042 significantly reduced morphological and functional damages in retinal ischemia. Our data demonstrate that 5-HT(2) receptor antagonists including MCI-9042 and M-1 have the neuroprotective effects in cultured RGCs and that MCI-9042 protects against ischemic retinal diseases.     

Caspase inhibitors protect against NMDA-mediated retinal ganglion cell death

Background: Apoptosis is a major mechanism of cell death in glutamate‐induced excitotoxicity and caspases as the executors of apoptosis play an important role in the development of various central nervous system and eye diseases. We studied the involvement of certain caspases in excitotoxic retinal ganglion cell death, which was experimentally induced in Brown Norway Rats by application of the glutamate receptor agonist N‐methyl‐D‐aspartate (NMDA). Methods: Animals were injected intravitreally with one of six caspase inhibitors (against caspases 1, 3, 4, 6, 8 and 9). Seven hours later, NMDA or phosphate‐buffered saline as a control was injected intravitreally into the respective eyes. The neuroprotective potential against NMDA toxicity was assessed by retinal ganglion cell quantification. Additionally, wholemount TUNEL was performed. Results: Statistical analysis revealed significant neuroprotective effects for the inhibitors of caspases 3, 6, 8 and 9, but not for those of caspases 1 and 4. The inhibitors of caspases 6 and 9 showed greater neuroprotective potential than those of caspases 3 and 8, although cell death was not entirely averted in any case. Results of ganglion cell counts were confirmed for the most pronounced treatment groups using wholemount TUNEL. Conclusion: Excitotoxic retinal ganglion cell death after NMDA injection is mediated mainly through apoptosis, whereby extrinsic as well as intrinsic pathways of caspase activation play a role.     

Neuroprotective effects of brimonidine against transient ischemia-induced retinal ganglion cell death: a dose response in vivo study

The purpose of this study was to investigate the dose-response effects of topically administered brimonidine (BMD) on retinal ganglion cell (RGC) survival, short and long periods of time after transient retinal ischemia. In adult Sprague-Dawley rats, RGCs were retrogradely labeled with the fluorescent tracer fluorogold (FG) applied to both superior colliculi. Seven days later, the left ophthalmic vessels were ligated for 90 min. One hr prior to retinal ischemia, two 5 microl drops of saline alone or saline containing 0.0001, 0.001, 0.01 or 0.1% BMD were instilled on the left eye. Rats were processed 7, 14 or 21 days later and densities of surviving RGCs were estimated by counting FG-labeled RGCs in 12 standard regions of each retina. The following have been found. (1) Seven days after 90 min of transient ischemia there is loss of approximately 46% of the RGC population. (2) topical pre-treatment with BMD prevents ischemia-induced RGC death in a dose-dependent manner. Administration of 0.0001% BMD resulted in the loss of approximately 37% of the RGC population and had no significant neuroprotective effects. Administration of higher concentrations of BMD (0.001 or 0.01%) resulted in the survival of 76 or 90%, respectively, of the RGC population, and 0.1% BMD fully prevented RGC death in the first 7 days after ischemia. (3) Between 7 and 21 days after ischemia there was an additional slow cell loss of approximately 25% of the RGC population. Pre-treatment with 0.1% BMD also reduced significantly this slow cell death. These results indicate that the neuroprotective effects of BMD, when administered topically, are dose-dependent and that the 0.1% concentration achieves optimal neuroprotective effects against the early loss of RGCs. Furthermore, this concentration is also effective to diminish the protracted loss of RGCs that occurs with time after transient ischemia.     

Simvastatin upregulates Bcl-2 expression and protects retinal neurons from early ischemia/reperfusion injury in the rat retina

Simvastatin has been shown to enhance the survival of retinal ganglion cells (RGCs) following ischemia-reperfusion (IR) injury by mediating the expression of stress proteins. The purpose of this study was to investigate the effect of simvastatin on retinal neurons and the expression of apoptotic proteins in a rat IR model. Wistar rats received intravitreal injection of simvastatin immediately after retinal reperfusion. Retinal ischemia was induced by increasing intraocular pressure to 150 mmHg for 60 min. The number of viable RGCs was measured after retrograde labeling with Fluoro-Gold. Ischemia-induced apoptotic cell death was studied using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). We found that simvastatin treatment enhanced RGC survival after retinal ischemia by approximately 40% and decreased retinal neuronal apoptosis. Using western blot analysis, we found that simvastatin upregulated the expression of Bcl-2 in the retina. In contrast, the level of the protein Bax was unaffected by simvastatin treatment. Our results suggest that RGC loss induced by retinal IR may be prevented by simvastatin and that the mechanism underlying this process possibly involves an alteration in the apoptotic pathway.     

Retinal ganglion cell numbers and delayed retinal ganglion cell death in the P23H rat retina

The P23H-1 rat strain carries a rhodopsin mutation frequently found in retinitis pigmentosa patients. We investigated the progressive degeneration of the inner retina in this strain, focussing on retinal ganglion cells (RGCs) fate. Our data show that photoreceptor death commences in the ventral retina, spreading to the whole retina as the rat ages. Quantification of the total number of RGCs identified by Fluorogold tracing and Brn3a expression, disclosed that the population of RGCs in young P23H rats is significantly smaller than in its homologous SD strain. In the mutant strain, there is also RGC loss with age: RGCs show their first symptoms of degeneration at P180, as revealed by an abnormal expression of cytoskeletal proteins which, at P365, translates into a significant loss of RGCs, that may ultimately be caused by displaced inner retinal vessels that drag and strangulate their axons. RGC axonal compression begins also in the ventral retina and spreads from there causing RGC loss through the whole retinal surface. These decaying processes are common to several models of photoreceptor loss, but show some differences between inherited and light-induced photoreceptor degeneration and should therefore be studied to a better understanding of photoreceptor degeneration and when developing therapies for these diseases.     

P2X7受体对缺氧诱发小鼠视网膜神经节细胞凋亡的影响

目的：：探讨嘌呤受体P2X7对缺氧诱发小鼠视网膜神经节细胞凋亡的影响。方法：以小鼠视网膜神经节细胞株RGC-5为研究对象,按照不同处理因素将细胞随机分为4组：正常对照组( G1)、缺氧组( G2)、缺氧+激动剂( BzATP )组( G3)、缺氧+拮抗剂(BBG)组(G4);采用四甲基偶氮唑蓝(MTT)法检测细胞的存活率;用Annxin V/PI染色流式细胞术检测细胞凋亡率;Western Blot检测细胞内cleave-caspase-3和cleave-PARP蛋白的表达。结果：与正常对照组相比, RGC-5细胞经缺氧处理后,细胞存活率明显降低;凋亡率显著升高;细胞内 cleave-caspase-3和cleave-PARP蛋白表达增加;P2X7受体激动剂BzATP能明显加重缺氧诱发的细胞凋亡,而BBG预处理可以显著拮抗缺氧所致的细胞凋亡。结论：缺氧能激活视网膜神经节细胞嘌呤受体P2X7,并参与视网膜神经节细胞的凋亡。     

Neuroprotective effects of prostaglandin analogues on retinal ganglion cell death independent of intraocular pressure reduction

Prostaglandin (PG) analogues may have an additional effect to protect neurons independent of IOP reduction. Only a few reports indicated that some PG analogues had neuroprotective effects or increased blood flow in in vivo and in vitro models. However, there is no comparative study using all clinically available PG analogues and also using primary culture of retinal ganglion cell (RGC). Our purpose of study is to investigate the direct neuroprotective effect of PG analogues on glutamate- and hypoxia-induced RGC death using rat purified primary RGC culture with latanoprost acid, travoprost acid, bimatoprost acid, bimatoprost, tafluprost acid, unoprostone, and PGF2α. Purified RGCs cultures were obtained from retinas of 6 days old Wistar rats, following a two-step immuno-panning procedure. After 72 h of cultivation, the neuroprotective effect of PG analogues (1 nM, 10 nM and 100 nM) was investigated by culturing the RGCs in 25 μM glutamate for a further 72 h or 5% O2 hypoxic condition for 24 h. The RGC viability under each condition normalized to that under normal condition without stress was evaluated as live cell percentage based on a total of 15 repeated experiments. As a result, 100 nM of latanoprost acid, tafluprost acid, bimatoprost acid, and bimatoprost significantly increased RGC survival rate by suppressing apoptosis. PG analogues indicated IOP independent neuroprotective effect on glutamate- or hypoxia-induced RGC death using rat primary RGC culture at clinically available intracameral concentration. Since those profiles were different from clinical efficacy in IOP reduction, the mechanism of neuroprotection may be not related to FP receptor stimulation.     

Protective effects of catalase on retinal ischemia/reperfusion injury in rats

Retinal ischemia/reperfusion (I/R) injury causes profound tissue damage, especially retinal ganglion cell (RGC) death. The aims of the study were to investigate whether catalase (CAT) has a neuroprotective effect on RGC after I/R injury in rats, and to determine the possible antioxidant mechanism. Wistar female rats were randonmized into four groups: normal control group (Control group), retinal I/R with vehicle group (I/R with vehicle group), retinal I/R with AAV-CAT group (I/R with AAV-CAT group), and normal retina with AAV-CAT group (normal with AAV-CAT group). One eye of each rat was pretreated with recombinant adeno-associated virus containing catalase gene (I/R with AAV-CAT group or normal with AAV-CAT group) and recombinant adeno-associated virus containing GFP gene (I/R with vehicle group) by intravitreal injection 21 days before initiation of I/R injury. Retinal I/R injury was induced by elevating intraocular pressure to 100 mmHg for 1 h. The number of RGC and inner plexiform layer (IPL) thickness were measured by fluorogold retrograde labeling and hematoxylin and eosin staining at 6 h, 24 h, 72 h and 5d after injury. Hydrogen peroxide (H₂O₂), the number of RGC, IPL thickness, malondialdehyde(MDA), 8-hydroxy-2-deoxyguanosine (8-OHdG), CAT activity and nitrotyrosine were measured by fluorescence staining, immunohistochemistry and enzyme-linked immunosorbent assay analysis at 5 days after injury. Electroretinographic (ERG) evaluation was also used. Pretreatment of AAV-CAT significantly decreased the levels of H₂O₂, MDA, 8-OHdG and nitrotyrosine, increased the catalase activity, and prevented the reduction of a- and b- waves in the I/R with AAV-CAT group compare with the I/R with vehicle group (p < 0.01). Catalase attenuated the I/R-induced damage of RGC and IPL and retinal function. Therefore, catalase can protect the rat retina from I/R-induced injury by enhancing the antioxidative ability and reducing oxidative stress, which suggests that catalase may be relevant for the neuroprotection of inner retina from I/R-related diseases.     

糖尿病视网膜神经节细胞损伤的研究进展

糖尿病性视网膜病变( diabetic retinopathy,DR)是糖尿病严重并发症之一,可对患者造成严重视功能损害。在视网膜出现微血管病变之前,已经出现视网膜神经节细胞(retinal ganglion cell, RGC)的病变。神经细胞的病理改变是糖尿病早期视功能障碍的重要因素。 RGC的损伤机制可能与高血糖代谢紊乱、氧化应激损伤、神经营养因子缺乏以及谷氨酸兴奋毒性有关。许多实验研究发现神经元保护药物能减少RGC凋亡,一些关于有效性和安全性的临床研究为临床治疗糖尿病视网膜神经细胞病变奠定重要基础。     

Experimental detection of retinal ganglion cell damage in vivo

In vivo detection of retinal ganglion cell (RGC) damage should have experimental and clinical relevance. A number of experimental models have been recently described to visualize RGCs in vivo. With retrograde injection of fluorescent tracers into the superior colliculus, lateral geniculate body, or optic nerve, RGCs can be detected in vivo with confocal laser scanning microscopy, fluorescent microscopy, or confocal scanning laser ophthalmoscopy. Although the resolution of these imaging techniques is limited to detecting only the cell bodies, the addition of adaptive optics has allowed in vivo visualization of axonal and dendritic processes. An ideal experimental model for detection of RGC damage should be non-invasive and reproducible. The introduction of a strain of transgenic mice that express fluorescent proteins under the control of Thy-1 promoter sequence has offered a non-invasive approach to detect RGCs. Long- term serial monitoring of RGCs over a year has been shown possible with this technique. In vivo imaging of RGCs could provide crucial information to investigating the mechanisms of neurodegenerative diseases and evaluating the treatment response of neuroprotective agents.     

干细胞移植在视网膜神经节细胞损伤修复中的应用

进行性视网膜神经节细胞损伤在一些致盲性眼病中屡见不鲜。目前临床上缺乏有效的损伤修复方法,然而最近研究显示干细胞移植为受损视网膜神经节细胞的保护和替代治疗提供了新思路。本文将就干细胞移植为基础的研究进展进行综述。     

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.     

银杏叶制剂EGb 761对外伤后视网膜神经节细胞的保护作用

目的 探讨银杏叶提取物制剂EGb 761对大鼠视神经损伤后视网膜神经节细胞(RGC)存活的影响.方法 大鼠48只经荧光金逆行标记后制备视神经损伤的动物模型,随机分为治疗组和对照组,两组分别给予EGb 761 150 mg/kg·d和生理盐水灌胃.在视神经损伤后4d、7d及14d观察视网膜铺片,进行RGC计数.结果 大鼠视神经损伤后4d、7d及14d,RGC数量持续减少,但治疗组均高于对照组,各时间点的差异均有统计学意义(依次为P＜0.05,P＜0.01,P＜0.01).结论 EGb761可促进视神经损伤后RGC的存活,对RGC有保护作用.     

The emerging role of proteases in retinal ganglion cell death

Retinal ganglion cell (RGC) death is an important issue in Primary Open Angle-Glaucoma (POAG) in terms of both vision loss and health care costs. Yet, the pathophysiology underlying RGC death in glaucoma is unclear. A growing body of evidence indicates that proteases that modulate the extracellular matrix (ECM) milieu in the retina, either directly or indirectly, play an important role in dictating the fate of RGCs. Recent evidence indicates that proteases, in addition to ECM-remodeling, have broader functional roles in glutamate receptor processing and predisposing RGCs to secondary damage. This review is focused on discussing the role of two groups of proteases, the matrix metalloproteinases (MMPs) and the plasminogen activators (PAs), in RGC death. In a long-run, a better understanding of the mechanisms involved in the regulation of proteases may lead to the development of adjunctive treatment options to attenuate RGC death and improve vision loss in glaucoma.