Retinal glutamate transporter changes in experimental glaucoma and after optic nerve transection in the rat

PURPOSE: High levels of glutamate can be toxic to retinal ganglion cells. Effective buffering of extracellular glutamate by retinal glutamate transporters is therefore important. This study was conducted to investigate whether glutamate transporter changes occur with two models of optic nerve injury in the rat. METHODS: Glaucoma was induced in one eye of 35 adult Wistar rats by translimbal diode laser treatment to the trabecular meshwork. Twenty-five more rats underwent unilateral optic nerve transection. Two glutamate transporters, GLAST (EAAT-1) and GLT-1 (EAAT-2), were studied by immunohistochemistry and quantitative Western blot analysis. Treated and control eyes were compared 3 days and 1, 4, and 6 weeks after injury. Optic nerve damage was assessed semiquantitatively in epoxy-embedded optic nerve cross sections. RESULTS: Trabecular laser treatment resulted in moderate intraocular pressure (IOP) elevation in all animals. After 1 to 6 weeks of experimental glaucoma, all treated eyes had significant optic nerve damage. Glutamate transporter changes were not detected by immunohistochemistry. Western blot analysis demonstrated significantly reduced GLT-1 in glaucomatous eyes compared with control eyes at 3 days (29.3% +/- 6.7%, P = 0.01), 1 week (55.5% +/- 13.6%, P = 0.02), 4 weeks (27.2% +/- 10.1%, P = 0.05), and 6 weeks (38.1% +/- 7.9%, P = 0.01; mean reduction +/- SEM, paired t-tests, n = 5 animals per group, four duplicate Western blot analyses per eye). The magnitude of the reduction in GLT-1 correlated significantly with mean IOP in the glaucomatous eye (r(2) = 0.31, P = 0.01, linear regression). GLAST was significantly reduced (33.8% +/- 8.1%, mean +/- SEM) after 4 weeks of elevated IOP (P = 0.01, paired t-test, n = 5 animals per group). In contrast to glaucoma, optic nerve transection resulted in an increase in GLT-1 compared with the control eye (P = 0.01, paired t-test, n = 15 animals). There was no significant change in GLAST after transection. CONCLUSIONS: GLT-1 and GLAST were significantly reduced in an experimental rat glaucoma model, a response that was not found after optic nerve transection. Reductions in GLT-1 and GLAST may increase the potential for glutamate-induced injury to RGC in glaucoma.     

Optic nerve dynein motor protein distribution changes with intraocular pressure elevation in a rat model of glaucoma

Acute intraocular pressure (IOP) elevation causes accumulation of retrogradely-transported brain derived neurotrophic factor and its receptor at the optic nerve head (ONH) in rats and monkeys. Obstruction of axonal transport may therefore be involved in glaucoma pathogenesis, but it is unknown if obstruction is specific to certain transported factors or represents a generalized failure of retrograde axonal transport. The dynein motor complex mediates retrograde axonal transport in retinal ganglion cells (RGC). Our hypothesis was that elevated IOP interferes with dynein-mediated axonal transport. We studied the distribution of dynein subunits in the retina and optic nerve after acute and chronic experimental IOP elevation in the rat. IOP was elevated unilaterally in 54 rats. Dynein subunit distribution was compared in treated and control eyes by immunohistochemistry and Western blotting at 1 day (n=12), 3 days (n=4), 1 week (n=15), 2 weeks (n=12) and 4 weeks (n=11). For immunohistochemistry, sections through the ONH were probed with an anti-dynein heavy chain (HC) antibody and graded semi-quantitatively by masked observers. Other freshly enucleated eyes were microdissected for separate Western blot quantification of dynein intermediate complex (IC) in myelinated and unmyelinated optic nerve, ONH and retina. Immunohistochemistry showed accumulation of dynein HC at the ONH in IOP elevation eyes compared to controls (P<0.001, Wilcoxon paired sign-rank test, n=29). ONH dynein IC was elevated by 46.5% in chronic IOP elevation eyes compared to controls by Western blotting (P<0.001, 95% CI=25.9% to 67.8%, n=17). The maximum increase in ONH dynein IC was 78.7% after 1 week (P<0.05, n=5), but significant increases were also detected after 4 h and 4 weeks of IOP elevation (P<0.05, n=4 rats per group). Total retinal dynein IC was increased by 8.7% in chronic IOP elevation eyes compared to controls (P<0.03, 95% CI 1.4% to 16.1%, n=24). In the retina, IOP elevation particularly affected the 72 kD subunit of dynein IC, which was 100.7% higher in chronic IOP elevation eyes compared to controls (P<0.00001, 95% CI 71.0% to 130.4%, n=21). Dynein IC changes in myelinated and unmyelinated optic nerve were not significant (P>0.05). We conclude that dynein accumulates at the ONH with experimental IOP elevation in the rat, supporting the hypothesis that disrupted axonal transport in RGC may be involved in the pathogenesis of glaucoma. The effect of IOP elevation on other motor proteins deserves further investigation in the future.     

Retrograde axonal transport of BDNF in retinal ganglion cells is blocked by acute IOP elevation in rats

PURPOSE: To determine whether acute experimental glaucoma in rats obstructs retrograde transport of brain-derived neurotrophic factor (BDNF) to retinal ganglion cells (RGCs). METHODS: Forty rats had unilateral injection of either (125)I-BDNF (20 animals) or a mixture of (125)I-BDNF and 100-fold excess nonradiolabeled BDNF (20 animals). In each group of 20 animals, eyes contralateral to injection had either normal intraocular pressure (IOP; 10 animals) or IOP elevated to 25 mm Hg below the systolic blood pressure of the eye (10 animals). In each group of 20 rats, ipsilateral eyes had IOP set at systolic blood pressure (4 eyes), had optic nerve transection (10 eyes), or had normal IOP (6 eyes). Six hours after injection, animals were killed and tissues were fixed, embedded, and sectioned for autoradiography. Grain counts were performed over retina and optic nerve using automated image analysis. RESULTS: IOP elevation to 25 mm Hg below systolic blood pressure (perfusion pressure [PP] 25) decreased median retinal nerve fiber layer (NFL) grains by 38% compared with controls (P: < 0.001). Competition by cold BDNF reduced NFL grains by 28% (P: = 0.013). Considering only the radioactivity representing specific retrograde transport of BDNF, IOP elevation to PP25 reduced transport by 74%, whereas elevation to PP0 (equaling systolic blood pressure) reduced specific transport by 83%. CONCLUSIONS: BDNF is transported retrogradely from the superior colliculus in adult rats, and this transport is substantially inhibited by acute IOP elevation. Deprivation of BDNF among RGCs may contribute to neuron loss in glaucoma.     

Experimental Glaucoma Model in the Rat Induced by Laser Trabecular Photocoagulation After an Intracameral Injection of India Ink

A simple and reproducible rodent glaucoma model is required to elucidate the pathophysiology of damage to the optic nerve. We developed chronically elevated intraocular pressure (IOP) unilaterally in rats by injecting india ink into the anterior chamber of one eye using a 30-gauge needle. One week later, trapped carbon particles in the chamber angle formed a black band along the corneal limbus in the injected eyes. We performed direct laser photocoagulation without a gonio lens, and selectively burned the trabecular meshwork. Intraocular pressure was measured every week and laser photocoagulation was repeated until mean IOP in the experimental eyes rose above 25 mmHg. Unilateral IOP elevation was attained in all rats within 4 weeks. Twelve weeks after ink injection, we sacrificed the rats and excised the eyes for histologic analysis. The anterior chamber angle showed peripheral anterior synechia caused by laser photocoagulation, and carbon particles were engulfed by macrophages that infiltrated the ciliary cleft. In the optic nerve head, a remarkable decrease in the nerve fiber layer and cavernous degeneration were observed, suggesting glaucomatous optic nerve damage. This experimental rodent model should facilitate the study of the complex mechanisms involved in glaucoma.     

玻璃体腔注射大麻素HU-211治疗鼠青光眼视神经损伤的研究

目的：评价玻璃体腔内注射大麻素HU-211对大鼠青光眼模型视神经的保护作用,为青光眼视神经损伤治疗提供实验依据。

方法：采用电凝巩膜表面静脉法制作大鼠青光眼模型18眼,随机分为3组：A组分别隔日一次玻璃体腔注射1mg/0.1mL大麻素HU-211,B组隔日一次玻璃体腔注射0.1mL生理盐水,C组为高眼压组。随机选6只对侧眼为空白对照组,每日观察眼压变化情况,用药4wk后处死大鼠,视网膜冰冻切片,HE染色通过视网膜神经元的密度变化评估大鼠慢性高眼压模型视网膜神经元的损伤程度。

结果： B组的凋亡程度及RGC的损伤程度明显高于A组,差异有统计学意义(P<0.05), B组与C组比较差异无统计学意义(P>0.05)。

结论： 玻璃体腔注射大麻素(HU-211)对大鼠青光眼模型视神经视网膜有明显的保护作用。     

Microarray analysis of changes in mRNA levels in the rat retina after experimental elevation of intraocular pressure

PURPOSE: The goal of this study was to identify altered patterns of retinal mRNA expression after experimental elevation of intraocular pressure (IOP) in a rat glaucoma model. METHODS: Brown Norway rats (N = 16) received unilateral episcleral vein injection of hypertonic saline to elevate IOP. IOP was monitored daily by handheld tonometer, and retinas were collected 8 days and 5 weeks after surgery. Comparison of mRNA levels between experimental and fellow retinas was made using gene microarrays (rat U34A rat arrays; Affymetrix, Santa Clara, CA). Semiquantitative RT-PCR was used to confirm selected results from array analysis and to compare with alterations after optic nerve transection. RESULTS: IOP elevation for 5 weeks resulted in reproducible changes in levels of 81 mRNAs. Of these, 74 increased, whereas only 7 decreased. The expression levels of 27 of these same messages were changed after 8 days of IOP elevation. In addition, four other genes demonstrated altered expression after the shorter period of elevated IOP exposure. Approximately half of the mRNAs with altered expression were associated with either neuroinflammatory responses or apoptosis. For 25 of the selected functionally relevant messages altered by array analysis, the alterations were confirmed by semiquantitative RT-PCR. The levels of 24 of 25 selected messages were also changed after optic nerve transection. CONCLUSIONS: The activation of glia and the complement system after IOP elevation, which is similar to that described in several neurodegenerative diseases and after optic nerve transection, suggests that this rat glaucoma model could be used to evaluate the neuroprotective potential of therapeutic agents that target these processes.     

灯盏细辛对大鼠慢性高眼压模型视神经损伤保护的实验研究

目的:建立大鼠慢性高眼压模型,观察灯盏细辛(Erigeronbrevicapas hand mass,EBHM)对眼压升高诱导视神经损伤的保护作用。方法:选用健康成年Wistar大鼠90只,分为3组。用波长为532nm的氪离子黄绿激光光凝第1和第2组大鼠双眼小梁网,建立大鼠高眼压模型。在眼压升高后1wk开始用EBHM对第2组大鼠15mg/100g肌肉注射,行视神经保护性治疗。第1组作为光凝对照组,第3组大鼠作为正常对照组。在第9wk同时处死3组大鼠做全视网膜铺片,1%甲苯氨蓝染色,记数平均视网膜神经节细胞(retinalganglion cells,RGCs)密度。结果:所有光凝眼眼压均中等程度升高,光凝前眼压为14.70±3.2mmHg;光凝后第3,6,9wk眼压分别为27.25±4.75,28.75±6.24,25.47±5.60mmHg,与光凝前比较,差别有显著性(P<0.05)。经视网膜铺片甲苯胺蓝染色,视网膜RGCs密度值(个/mm2)为:第1组1654±136,第2组2135±125,第3组2516±196。第2组大鼠视网膜RGCs密度值与第1和第3组大鼠RGCs密度值比较,差别有显著性(P<0.05)。结论:光凝大鼠小梁网成功建立大鼠慢性高眼压模型,光凝眼眼压中等程度升高,RGC密度降低;EBHM能够部分保护大鼠慢性高眼压诱导的视神经损害。     

Characteristics of Optic Nerve Damage Induced by Chronic Intraocular Hypertension in Rat

Purpose:To set up the Sharma‘s chronic intraocular hypertension model and investigate the intraocular pressure (IOP) as well as the optic nerve damage of this model in rat.Methods :The operations of the chronic intraocular hypertension model were performed as described by Sharma in 60 male Lewis albino rats. IOP was measured using the TonoPen XL immediately after surgery and then at 5 day, 2 week or 4 week intervals. Cresyl violet staining of whole-mounted retinas was used to label retinal ganglion cells (RGCs),then RGCs were counted. Paraphenylenediamine (PPD) staining was performed in the semi-thin cross sections of optic nerve of rat, in order to know whether the axons of optic nerve were degenerated or not.Results:There were 47 rats with higher IOP after the episcleral veins cauterized in 60 rats. The ratio of elevated IOP was 78.3%. The IOPs were stable in 4 weeks. After cresyl violet staining, the RGCs loss was 11.0% and 11.3% was found in the central and peripheral retina respectively after 2 weeks of increased IOP. After 4 weeks of increased IOP, the loss of RGCs was 17% for the central retina and 24.6% for the peripheral retina. In the retinas without higher IOP, there was no loss of RGCs. PPD staining showed that optic nerve of rat with about 5.3% damage of axons located at the superior temporal region. Region of affected optic nerve 1 mm posterior to the globe by light microscope showed evidence of damaged axons with axonal swelling and myelin debris.Conclusion:Sharma‘s chronic intraocular hypertension model is a reproducible and effective glaucoma model, which mimics human glaucoma with chronically elevation IOP and induced RGCs loss and damage of optic nerve.     

糖尿病合并视网膜脱离术后高眼压的处理及危险因素探讨

目的：观察糖尿病合并孔源性视网膜脱离患者行玻璃体切割术后短期内眼压的波动情况并探讨可能的危险因素及有效的治疗方法。

方法：连续收集100例糖尿病合并高度近视及孔源性视网膜脱离的患者并分为两组：试验组和对照组,试验组患者术后使用妥布霉素地塞米松滴眼液。分别监测术眼玻璃体切割术术前及术后的眼压情况,神经纤维层厚度(RNFL)和视盘参数,同时记录对侧眼术前的情况。实验数据采用Graphpad 7.0进行分析。

结果：所有的糖尿病患者中有42眼在玻璃体切割术后1wk内出现眼压升高,其中试验组31眼,而对照组11眼。术后5d-1wk及1mo时两组间差异有显著统计学意义。随后,39眼经过治疗后眼压下降,3眼接受了青光眼滤过手术。与眼压升高前的视盘各参数相比,眼压升高后,平均及下方RNFL厚度变薄,盘沿面积变小,同时视杯容积和垂直杯盘比增加。眼压升高患者对侧眼的RNFL厚度相比于从未出现高压眼的患者明显变薄。

结论：玻璃体切割术术后连续使用激素类药物是糖尿病合并视网膜脱离患者术后眼压升高的危险因素,并且可疑青光眼患者使用激素后眼压更易升高。     

Selective ganglion cell functional loss in rats with experimental glaucoma

PURPOSE: To characterize retinal functional consequences of elevated intraocular pressure (IOP) in a rat model of experimental glaucoma. METHODS: Unilateral elevation of IOP was produced by hypertonic saline injection into an episcleral vein in 20 adult male Brown-Norway rats. IOP was measured in both eyes of awake animals four to five times per week. After 5 weeks, animals were dark adapted overnight (>12 hours) and full-field electroretinograms (ERGs) were obtained simultaneously from both eyes. Scotopic ERG stimuli were brief white flashes (-6.64-2.72 log cd-s/m(2)). Photopic responses were also obtained (0.97-2.72 log cd-s/m(2)) after 15 minutes of light adaptation (150 cd/m(2)). Eyes were processed the following day for histologic evaluation by light microscopy, including masked determination of optic nerve injury grade (ONIG; 1, normal; 5, severe, diffuse damage). RESULTS: Among experimental eyes, the group average IOP (+/-SD) was 34.5 +/- 4.1 mm Hg, whereas the average for control eyes was 28.1 +/- 0.5 mm Hg (t = 7.1, P < 0.0001). The average ONIG for experimental and control eye groups, respectively, was 3.4 +/- 1.7 and 1.0 +/- 0.02 (t = 6.3, P < 0.0001). The ONIG increased with mean IOP in experimental eyes (r(2) = 0.78, P < 0.0001) and was unrelated to mean IOP in control eyes (r(2) = 0.09, P = 0.18). In experimental eyes with relatively mild IOP elevation (mean IOP < 31 mm Hg) and no structural (histologic) damage to the optic nerve evident by light microscopy (ONIG = 1.1 +/- 0.2, n = 5), there was a selective reduction of the positive scotopic threshold response (pSTR; P < 0.001), whereas other ERG components remained unaltered. In four of the five eyes, pSTR amplitude was reduced by more than 50%, whereas all five had normal scotopic a-wave, b-wave, and OP amplitudes. Eyes with mean IOP of more than 35 mm Hg had reduced a-wave, b-wave, and oscillatory potential (OP) amplitudes. CONCLUSIONS: As demonstrated by prior studies, selective loss of the pSTR is indicative of selective retinal ganglion cell (RGC) injury. In this rat model of experimental glaucoma, selective RGC functional injury occurred before the onset of structural damage, as assessed by light microscopy of optic nerve tissue. The highest IOP levels resulted in nonselective functional loss. Thus, in rodent models of experimental glaucoma, lower levels of chronically elevated IOP may be more relevant to human primary chronic glaucoma.     

The effect of experimental glaucoma and optic nerve transection on amacrine cells in the rat retina

PURPOSE: To detect alterations in amacrine cells associated with retinal ganglion cell (RGC) depletion caused by experimental optic nerve transection and glaucoma. METHODS: Intraocular pressure (IOP) was elevated unilaterally in 18 rats by translimbal trabecular laser treatment, and eyes were studied at 1 (n = 6), 2 (n = 5), and 3 (n = 7) months. Complete optic nerve transection was performed unilaterally in nine rats with survival for 1 (n = 4) and 3 (n = 5) months. Serial cryosections (five per eye) were immunohistochemically labeled with rabbit anti-gamma-aminobutyric acid (GABA) and anti-glycine antibodies. Cells in the ganglion cell and inner nuclear layers that labeled for GABA or glycine were counted in a masked fashion under bright-field microscopy. Additional labeling with other RGC and amacrine antigens was also performed. RGC loss was quantified by axon counts. RESULTS: Amacrine cells identified by GABA and glycine labeling were not significantly affected by experimental glaucoma, with a mean decrease of 15% compared with bilaterally untreated control cells (557 +/- 186 neurons/mm [glaucoma] versus 653.9 +/- 114.4 neurons/mm [control] of retina; P = 0.15, t-test). There was no significant trend for amacrine cell counts to be lower in eyes with fewer RGCs (r = -0.39, P = 0.11). By contrast, there was highly significant loss of GABA and glycine staining 3 months after nerve transection, both in the treated and the fellow eyes (P < 0.0001, t-test). However, there was a substantial number of remaining amacrine cells in transected retinas, as indicated by labeling for calretinin and calbindin. CONCLUSIONS: Experimental glaucoma causes minimal change in amacrine cells and their expression of neurotransmitters. After nerve transection, neurotransmitter presence declines, but many amacrine cell bodies remain. Differences among optic nerve injury models, as well as effects on "untreated" fellow eyes, should be recognized.     

Chronic experimental glaucoma in primates. II. Effect of extended intraocular pressure elevation on optic nerve head and axonal transport

Intraocular pressure (IOP) elevations lasting from 2 to 42 days were produced in 13 primate eyes by anterior chamber injections of autologous, fixed red blood cells. The retina, optic nerve head, and optic nerves were studied by electron microscopy, and ganglion cell rapid axonal transport was examined after IOP elevations for various durations. Transport of axonal material was blocked at the scleral lamina cribrosa by IOP elevations to 50 mm Hg. With IOP elevation for less than 1 week, return to normal IOP restored normal transport in some axons. However, in other axons IOP elevation for less than 1 week intiated ganglion cell degeneration. The process of cellular death involved a rapid ascending degeneration from nerve head to brain, followed 3 to 4 weeks later by descending degeneration of the ganglion cell body and its attached axon. Axons of the superior and inferior optic nerve head and nerve seem to be damaged more extensively than those in the nasal and temporal optic nerve. Two to four days after IOP elevation, axons of the superficial optic nerve head were swollen with accumulating axonal material, leading to histologic disk edema. In those eyes with IOP elevation longer than 1 week, the loss of anterior disk nerve fibers combined with posterior and lateral movement of the lamina cribrosa lead to an increase in optic disk cupping. Astrocytes and capillaries of the optic nerve head seem to tolerate elevated IOP well and were relatively spared.     

超声乳化白内障手术对剥脱综合征性青光眼的降眼压作用

目的 观察和分析剥脱综合征性青光眼患者行超声乳化白内障摘除人工晶体植入术后的眼压变化。方法 对7例伴有高眼压、明显影响视力的白内障但尚无严重的视神经、视野损害的剥脱综合征患者施行超声乳化白内障摘除人工晶体植入术，比较手术前后的眼压变化。结果 术前平均眼压31．57mmHg，术后1周时平均眼压18．19mmHg，降幅为13．38mmHg，术前术后眼压差异极显著。结论 伴有明显影响视力白内障的剥脱综合征性青光眼病人在行超声乳化白内障摘除人工晶体植入术后眼压会显著下降，对那些尚未发生明显视神经视野损害的剥脱综合征性青光眼患者，行超声乳化白内障摘除人工晶体植入术可有效降低眼压。     

Obstructed axonal transport of BDNF and its receptor TrkB in experimental glaucoma

PURPOSE: In both animal model system and in human glaucoma, retinal ganglion cells (RGCs) die by apoptosis. To understand how RGC apoptosis is initiated in these systems, the authors studied RGC neurotrophin transport in experimental glaucoma using acute intraocular pressure (IOP) elevations in rats and chronic IOP elevation and unilateral optic nerve transections in monkeys. METHODS: Eyes were studied in masked fashion by light and electron microscopy and by immunohistochemistry with antibodies directed against the tyrosine kinase receptors (TrkA, B, and C) and against brain-derived neurotrophic factor (BDNF), as well as by autoradiography to identify retrograde axonal transport of 125I-BDNF injected into the superior colliculus. RESULTS: With acute glaucoma in the rat, RGC axons became abnormally dilated, accumulating vesicles presumed to be moving in axonal transport at the optic nerve head. Label for TrkB, but not TrkA, was relatively increased at and behind the optic nerve head with IOP elevation. Abnormal, focal labeling for TrkB and BDNF was identified in axons of monkey optic nerve heads with chronic glaucoma. With acute IOP elevation in rats, radiolabeled BDNF arrived at cells in the RGC layer at less than half the level of control eyes. CONCLUSIONS: Interruption of BDNF retrograde transport and accumulation of TrkB at the optic nerve head in acute and chronic glaucoma models suggest a role for neurotrophin deprivation in the pathogenesis of RGC death in glaucoma.     

Potential risk factors and treatment of IOP elevation after operation in retinal detachment eyes of diabetic patients

AIM: To observe the intraocular pressure (IOP) fluctuation at the early stage of pars plana vitrectomy (PPV) and silicon oil tamponade in high myopia with rhegmatogenous retinal detachment (RRD) eyes in diabetic patients and analyze the potential risk factors and effective treatment. METHODS: One hundred consecutive diabetic patients of RRD in highly myopic eyes were retrospectively reviewed. Patients were divided into two groups: the experimental group, those who used Tobramycin Dexamethasone Eye Drops (TDED), and control group. Pre- and postoperative IOPs, retinal nerve fiber thickness (RNFL) and optic nerve head parameters were recorded before and after IOP elevation, and in the contralateral eye before the operation. Graphpad 7.01 was used for data analysis. RESULTS: IOP elevation occurred in 42 eyes within 1wk after vitrectomy in all diabetic participants. Ocular hypertension (OHTN) was observed in 31 of 53 eyes in experimental group and 11 eyes of 47 eyes in control group at the early stage after operation. Significant differences were found between groups in 5d-1wk and 1mo after vitrectomy. In addition, IOP of 39 eyes had decreased by proper treatment and 3 eyes received glaucoma filtration surgery. Compared to the optic disc parameters before IOP elevation, the average and inferior RNFL thickness were thinner and rim area decreased as well as cup volume and vertical C/D radio increased after IOP elevation. The RNFL thickness of the opposite eyes in patients with IOP elevation was found thinner than the ones who never suffered ocular hypertension. CONCLUSION: Continual use of glucocorticoid after vitrectomy is a potential risk factor of IOP elevation in high myopia with diabetes, and doubtful open angle glaucoma should be focused on its sensibility to glucocorticoid and IOP elevation.     

大鼠实验性慢性高眼压对视网膜神经节细胞的损伤

目的:制作高眼压大鼠模型,观察高眼压对视神经的损害。方法:成年Wistar雄性大鼠65只,烧灼右眼上方2支和外侧1支巩膜上静脉,建立慢性高眼压模型。左眼作为对照眼。对造模成功的,分别于造模后1d,1,2,3,4,6,8,10wk各摘除6只大鼠双眼。在取出眼球前24h,用Fluoro-gold进行视网膜神经节细胞(retinal ganglion cells,RGC)逆行性染色,做视网膜铺片计数RGC,观察不同时段高眼压对RGC的影响。结果:右眼巩膜上静脉烧灼后各时间点造模眼平均眼压分别为42.2±1.8mmHg,37.9±2.3mmHg,36.1±2.0mmHg,33.6±2.2mmHg,32.2±2.4mmHg,30.1±2.0mmHg,30.5±2.1mmHg和27.6±1.3mmHg。术后各时间点的成模率分别为80.0%,76.9%,74.5%,71.7%,63.8%,56.1%,42.9%,41.4%。成模率和成模眼的眼压随时间延长呈下降趋势。实验组和对照组的RGC密度在早期(巩膜上静脉烧灼术后3wk内)没有显著差别。造模后4wk高眼压组RGC密度明显低于对照组(P<0.05),随着时间的推移差别越来越显著。结论:巩膜上静脉烧灼法能诱导出持续的肯定的大鼠慢性高眼压模型,成模眼的眼压和随时间而下降。高眼压持续的时间越长,RGC的损失越多。     

The use of cyclodialysis to limit exposure to elevated intraocular pressure in rat glaucoma models

Elevated intraocular pressure (IOP) is the most common risk factor for glaucoma and pressure control is the goal of current clinical glaucoma therapy. Yet, recent clinical studies have documented that, even after therapeutic lowering of IOP, glaucomatous visual field loss can progress in many patients. Experimental elevation of IOP in the rat is commonly used to model human glaucomatous injury. However, there currently is no rodent model for the clinical situation of glaucomatous progression in eyes with apparently controlled IOP. The purpose of this study was to evaluate the ability of surgical cyclodialysis to produce both prolonged, non-injurious reduction of IOP in rat eyes and to stably normalize IOP in eyes with experimental pressure elevation. To perform cyclodialysis, a blunted spatula was fashioned from a hypodermic needle and used to separate a portion of the ciliary body from the sclera, opening a channel into the suprachoroidal space to allow aqueous outflow. Experimental IOP elevation was produced in rats by unilateral injection of hypertonic saline. Cyclodialysis in normal eyes resulted in an average 40 +/- 4% reduction in IOP, without marked hypotony. IOP lowering could be sustained for at least 6 months. The risk of retinal or optic nerve injury following a single cyclodialysis procedure was minimal as evidenced by unaltered levels of four injury-responsive retinal mRNAs and by normal optic nerve morphology. Cyclodialysis in eyes with experimental IOP elevation resulted in IOP normalization that was sustained for durations of 7 and 21 days in 88% and 53% of eyes, respectively. In addition, in eyes with the same cumulative dose of elevated IOP prior to the procedure, successful IOP normalization by cyclodialysis resulted in significantly less optic nerve injury than that seen in eyes in which IOP control was ineffective (p = 0.03). These studies show that cyclodialysis provides a simple, non-injurious method to reduce experimentally elevated IOP in rats that can be used to model the clinical situation of eyes previously damaged by pressure. This tool offers new opportunities for identifying and studying the molecular processes associated with glaucomatous progression and for testing potential neuroprotective therapies in a clinically relevant situation.     

复方卡波姆诱发的兔高眼压模型与其它兔高眼压模型的比较研究

目的 建立适用于研究抗青光眼药物降眼压作用及保护视神经作用的兔青光眼模型。方法 将21只兔随机分为I、Ⅱ、Ⅲ及Ⅳ组,分别对其前房内注射复方卡波姆、甲基纤维素及复方甲基纤维素,结膜下注射地塞米松诱发青光眼,并对4种药物诱发的青光眼模型进行观察。结果 I组高眼压持续20－50d,平均眼压为29－35mmHg(1mmHg=0.133kPa),眼压峰值为37－45mmHg,青光眼模型成功率为91．7％。Ⅱ及Ⅲ级模型有10－20％的兔眼眼压升主持续3－4d,如按眼压为22mmHg持续1周的标准判断,Ⅱ及Ⅲ组模型均不理想。Ⅳ组眼压平均升高3mmHg,持续7d,亦为失败模型。结论 复方卡波姆诱发的兔青光眼模型具有引起眼压中度、稳定升高的时间长,方法简单,易于操作和控制等优点。可用于对青光眼性视神经视网膜损害的研究及对抗青光眼药物的研究,是一种较理想的兔青光眼模型。     

A rat model of glaucoma induced by episcleral vein ligation

To establish a reliable animal model of glaucoma, we examined if episcleral vein ligation in rat eyes can induce intraocular pressure (IOP) elevation and concomitant characteristic morphological features of glaucoma. IOP elevation was detected on the next day (30.1+/-4.4 mmHg: operated eyes; 21.0+/-1.8 mmHg: control eyes) and persisted at least 7 months after the procedure (24.5+/-2.3 mmHg: operated eyes; 19.7+/-1.9 mmHg: control eyes). These results suggest that episcleral vein ligation can induce very mild IOP elevation immediately after the operation, which can last over several months. Furthermore, it appears there was little variability in the patterns of IOP elevation among the individual eyes treated with episcleral vein ligation. Morphological changes were detected selectively in the retinal ganglion cell (RGC) layer and optic disc excavation was evident in the late stage of chronic IOP elevation. RGCs were selectively lost by apoptotic death. The number of RGCs was reduced by 18% at 12 weeks and eventually by 35% at 8 months postoperatively. Müller cells downregulated the expression of p27Kip1 and appeared to be partially in a reactive state even at the advanced stages of glaucoma. The expression of basic fibroblast growth factor and ciliary neurotrophic factor, which are neurotrophic factors implicated in the control of cell survivals and neuroprotection, significantly declined at the advanced stages. Taken altogether, these observations indicate that the episcleral vein ligation model based on the simple ligation procedure reproducibly provides a reliable glaucoma model and contributes to give insights into the underlying molecular and cellular bases of human glaucoma and to devise the new medication upon the disease.