Retinal ganglion cell protection with geranylgeranylacetone,a heat shock protein inducer,in a rat glaucoma model

PURPOSE: To study the effects of geranylgeranylacetone (GGA) on the expression of inducible (HSP72) and constitutive (HSC70) heat shock proteins (HSPs) on retinal ganglion cells (RGCs) in a rat model of glaucoma. METHODS: Adult Wistar rats were given intraperitoneal injections of GGA at 200 mg/kg daily. Western blot analysis and immunohistochemical staining for HSP72 and HSC70 were performed after 1, 3, and 7 days of treatment with GGA. After 7 days of GGA pretreatment, intraocular pressure (IOP) was elevated unilaterally by repeated trabecular argon laser photocoagulation 5 days after intracameral injection of india ink. After the first laser photocoagulation, GGA was administered twice a week. RGC survival was evaluated after 5 weeks of elevated IOP. Immunohistochemistry and TdT-mediated biotin-dUTP nick end labeling (TUNEL) were performed after 1 week of elevated IOP. Quercetin, an inhibitor of HSP expression, was also administered to a separate group. RESULTS: There was increased expression of HSP72 in RGCs at 3 and 7 days after administration of GGA, but HSC70 was unchanged. After 5 weeks of elevated IOP, there was a 27% +/- 6% loss of RGCs. The administration of GGA significantly reduced the loss of RGCs, lessened optic nerve damage, decreased the number of TUNEL-positive cells in the RGC layer, and increased HSP72. Quercetin abolished these protective effects. CONCLUSIONS: These results demonstrate that systemic administration of GGA protects RGCs from glaucomatous damage in a rat model and suggest a novel pathway for neuroprotection in patients with glaucoma.     

Induction of heat shock protein 72 protects retinal ganglion cells in a rat glaucoma model

PURPOSE: To investigate whether heat shock protein (Hsp) 72 is induced in retinal ganglion cells (RGCs) in experimental rat glaucoma and whether the induction of Hsp72 by heat stress or zinc (Zn(2+)) administration can increase survival of RGCs in the model. METHODS: Intraocular pressure (IOP) was elevated unilaterally in Wistar rats with argon laser irradiation of the trabecular meshwork 5 days after intracameral injection of india ink. Immunohistochemical staining for Hsp72 was performed. The rats with elevated IOP were treated with heat stress once a week (six rats) or intraperitoneal injection of zinc (10 mg/kg) every two weeks (six rats). Untreated rats with elevated IOP served as a control group (six rats). Quercetin, an inhibitor of Hsp expression was injected in the rats with heat stress (six rats) and zinc injection (seven rats). Subsequent to 4 weeks of IOP elevation, RGCs were counted. RESULTS: The IOP increase compared with the contralateral eyes was 48% +/- 4% throughout the study period. Hsp72 was detected only in the eyes with elevated IOP at 1 and 2 days and was weakly detected at 1 week of IOP elevation. A single administration of zinc strongly induced Hsp72 in RGCs of rats with elevated IOP for 2 weeks. Treatment with heat stress or zinc in rats with elevated IOP increased RGC survival after 4 weeks of IOP elevation, compared with the untreated control group (P = 0.004, n = 6). Quercetin reversed the positive effect of heat stress or zinc injection on RGC survival. CONCLUSIONS: These results demonstrate the possibility of a novel therapeutic approach to glaucoma through an enhanced induction of the endogenous heat shock response.     

A rat model for acute rise in intraocular pressure: immune modulation as a therapeutic strategy

PURPOSE: To establish a rat model of acute increase in intraocular pressure (IOP) and to investigate the therapeutic window for protection against death of retinal ganglion cells (RGCs) by vaccination with glatiramer acetate (Cop-1) or by treatment with brimonidine or MK-801. DESIGN: Animal study, laboratory investigation. METHODS: IOP was transiently increased in anesthetized Lewis rats by infusing normal saline (0.9%) into the anterior chamber of the eye for one hour. RGC survival was assessed one week and two weeks later by counting the RGCs retrogradely labeled with rhodamine dextran. MAIN OUTCOME MEASURES: RGC survival. RESULTS: IOP rose to 100 cm H(2)O (76 mm Hg) and returned to baseline after 24 hours. The RGC count decreased by 23% a week after the insult and by a further 7% after the second week. Vaccination with Cop-1 on the day of the insult prevented 50% of the IOP-induced RGC loss. Similar neuroprotection was achieved by daily intraperitoneal injections of brimonidine, but not with MK-801. CONCLUSIONS: A transient increase in IOP to 100 cm H(2)O causes death of RGCs in rats. A single immunization with Cop-1 or daily injections of brimonidine protected up to 50% of potentially doomed RGCs from IOP-induced death, suggesting that not all of the cell death in the untreated model results from the IOP insult directly, but that some of it is caused by insult-induced environmental cytotoxicity, which is unrelated to glutamate toxicity or at least to NMDA receptors. These findings can be applied immediately as a basis for acute glaucoma therapy.     

Different responses of macrophages in retinal ganglion cell survival after acute ocular hypertension in rats with different autoimmune backgrounds

Recently macrophages were shown to play a protective role in retinal ganglion cells (RGCs) after optic nerve (ON) injury. In the present study, we investigated how macrophages responded after acute intraocular pressure (IOP) elevation in experimental autoimmune encephalomyelitis (EAE)-resistant Fischer 344 (F344) and Sprague Dawley (SD) rats and EAE-vulnerable Lewis rats. Acute IOP elevation was performed at 110mmHg for 2h to mimic acute glaucoma. Phagocytic cells in the eye were removed by intravitreal application of clodronate liposomes whereas macrophage activation was achieved by intravitreal injection of zymosan, a yeast wall preparation. Fluorescence dye, FluoroGold, was applied behind the eyeballs to retrogradely label surviving RGCs 40h before animal sacrifice. Macrophages in the retina were identified by ED1 immunostaining. Loss of 25% RGCs in F344 but over 90% in Lewis rats was seen 2 weeks after acute IOP elevation. Significant increase in the number of macrophages in the retina was seen to accompany the great RGC loss in Lewis rats; removal of these macrophages reduced the extent of RGC loss, suggesting the involvement of macrophages in RGC death in Lewis strain. Low numbers of macrophages were seen in F344 retinas after acute IOP elevation, and removal of macrophages did not show clear effect on RGC viability. Whereas macrophage activation by zymosan protected RGCs after ON axotomy in F344 rats, the same macrophage activation became detrimental to RGCs after acute IOP elevation. The extent of RGC loss 3 weeks after acute IOP elevation or after macrophage activation by zymosan in EAE-resistant SD rats was similar to that in F344 rats. We thus demonstrate that macrophages in rats with different autoimmune backgrounds react differently to acute IOP elevation and differentially modulate RGC loss, a phenomenon contrary to the protective action in RGCs after ON axotomy. These data suggest that autoimmune background plays a role in modulating vulnerability of RGCs to acute IOP elevation.     

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。     

鼠青光眼模型视网膜神经节细胞中热休克蛋白27表达的研究

目的探讨热休克蛋白27(HSP27)在鼠青光眼模型视网膜神经节细胞(RGCs)中的表达及其与血清中相应抗体的关系。方法将49只Wistar大鼠随机分为高眼压组(32只鼠)、sham对照(假手术)组(12只鼠)及正常对照组(5只鼠)。电凝鼠巩膜表面至少3组静脉及角膜缘周围血管,减少房水静脉回流,建立鼠青光眼模型。分别于术后1、2、3、4及8周分别处死大鼠。处死前测眼压,抽血2ml,供酶联免疫吸附测定使用,分析视网膜组织内HSP27蛋白抗原产生的血清中相应抗体水平。同时对鼠眼视网膜组织进行石蜡切片,采用免疫组化法检测RGCsHSP27的表达及分布情况,并对检测结果进行统计学分析。结果高眼压组右眼术后眼压明显升高,术后3d眼压(27.52±6.63)mmHg(1mmHg=0.133kPa),术后1周眼压(31.42±6.18)mmHg,此后眼压基本稳定。术后各时间点高眼压组右眼眼压与其术前、左眼及sham组右眼和左眼比较,差异有统计学意义(P<0.01)。血清中抗HSP27抗体滴度在术后1周缓慢升高,2、3周达高峰,此后逐渐下降至接近正常水平。术后2周和3周,高眼压组血清中HSP27抗体含量与sham对照组和正常对照组比较,差异有统计学意义(P<0.01和P<0.05)。RGCs中HSP27阳性表达率在术后各时间点,高眼压组右眼与左眼、sham对照组右眼和左眼及正常对照组右眼和左眼比较,差异有统计学意义(P<0.01)。RGCs中HSP27阳性表达随着眼压升高及高眼压持续时间延长逐渐增强,且视网膜神经纤维层中也出现较明显的HSP27的阳性表达。结论内源性HSP27表达增强可能在青光眼视神经病变中具有重要作用。     

Neuroprotective and intraocular pressure-lowering effects of (-)Delta9-tetrahydrocannabinol in a rat model of glaucoma

In glaucoma, retinal ganglion cell (RGC) death is induced by many risk factors, including ocular hypertension. It has been proposed that glutamate-mediated oxidative stress may also contribute to this RGC death. Cannabinoids are known to possess therapeutic properties including ocular hypotension and antioxidation. In this study, we test the hypothesis that (-)Delta(9)-tetrahydrocannabinol (THC) lowers intraocular pressure (IOP) and prevents RGC death in a rat model of glaucoma. Arat model of experimental glaucoma with chronic, moderately elevated IOP was produced unilaterally by cauterization of episcleral vessels. Rats received weekly injections of THC at a level of 5 mg/kg or vehicle for 20 weeks. IOP of both eyes was measured weekly on anesthetized animals immediately before THC treatment. RGCs were labeled in a retrograde fashion and counted in whole-mounted retinas. IOP was elevated in all operated eyes 1 day after the operation and remained elevated in the vehicle-treated rats throughout 20 weeks. In THC-treated rats, IOP elevation in operated eyes was diminished 2 weeks after operation and remained reduced. IOP in the contralateral control eyes was not affected by THC. In the operated eyes of vehicle-treated animals, there was a loss of approximately 50 and 40% of the RGCs in the peripheral and central retina, respectively. The RGC loss in the operated eyes of the THC-treated animals was reduced to 10-20%. These results demonstrate that THC is a neuroprotectant that preserves RGCs in an experimental model of glaucoma, possibly through a reduction in IOP.     

Does peak intraocular pressure measured by water drinking test reflect peak circadian levels? A pilot study

Background:  To determine whether there is a correlation between peak intraocular pressure (IOP) measured after water drinking test (WDT) and patient's peak daytime IOP.
Methods:  Patients who were diagnosed with glaucoma, ocular hypertension and/or glaucoma-like discs were enrolled in this prospective observational pilot study. All subjects underwent daytime IOP measurement by a single observer using a Goldmann Applanation Tonometer at 3-h intervals. Subjects were then given 10 mL/kg body weight of water to drink over 5 min; IOP was measured every 15 min for an hour. Correlations between peak IOP and IOP fluctuations as measured by the two methods were analyzed using Pearson's correlation coefficient.
Results:  Twenty-five patients were recruited for the study. There were 16 males and 9 females. The mean age was 68.8 ± 8.7 years (50–82 years), and 48% had primary open angle glaucoma. The mean peak IOP measured by diurnal testing (15.52 ± 3.6 mm Hg) was not statistically different from that measured by WDT (15.92 ± 3.2 mm Hg) ( P  = 0.7). The mean fluctuation in IOP measured during the day (2.32 ± 1.3 mm Hg) was also not significantly different from that measured by WDT (2.24 ± 1.2 mm Hg) ( P  = 0.8). Though peak IOP measured during diurnal testing showed strong correlation with peak IOP during WDT ( r  = 0.876), IOP fluctuation measured by the two tests showed poor correlation ( r  = −0.0789).
Conclusion:  WDT may provide a satisfactory alternative measure of peak IOP in a clinic setting. A larger sample is required to assess whether it is a good measure of IOP fluctuation.     

Ocular hypotensive effects of topically administered agmatine in a chronic ocular hypertensive rat model

Agmatine, a primary polyamine and potential neuromodulator, exhibits a high affinity to the α₂-adrenergic receptor as well as imidazoline receptors. As α₂-adrenergic receptor agonists display positive ocular hypotensive effects, we assessed whether agmatine effectively lowers intraocular pressure (IOP) using a chronic ocular hypertensive rat model. We raised IOP in unilateral eyes of Sprague-Dawley rats by cauterizing three episcleral veins per eye. Four weeks later, we topically administered 10⁻³ M agmatine solution 4 times a day for 6 consecutive weeks. After confirming the recovery of IOP to pretreatment level at 13 weeks after cauterization, the retinal ganglion cells (RGCs) were retrogradely labeled and counted. Eyes subjected to episcleral vein cauterization (EVC) demonstrated significant increases in IOP (48.39% increase over baseline IOP), and the elevated IOP was well maintained until 12 weeks. Topically administered agmatine powerfully lowered IOP to 30.29% of its pretreatment level, and the associated washout period was about two weeks. EVC was associated with a 55.44% loss of RGCs in the control group, but agmatine appeared to attenuate this RGC loss to 18.65%. Overall, topically administered agmatine appeared to effectively lower IOP and rescue RGCs in a chronic ocular hypertensive rat model. Although the mechanism underlying these effects is not yet established, it is possible that agmatine offers a powerful new ocular hypotensive agent for eyes with chronic ocular hypertension and/or glaucoma.     

热休克蛋白72（HSP72）对大鼠青光眼模型视网膜神经节细胞和视神经的保护作用

目的　探讨热休克蛋白72（heat shock protein 72,HSP72）对大鼠青光眼模型视网膜神经节细胞（retinal ganglial cells,RGCs）和视神经的保护作用。方法　选取Wistar大鼠46只，采用随机数字表法将所有大鼠分为正常对照组（6只）和实验组（40只），实验组40只大鼠中8只不作处理（实验对照组），在制作青光眼模型后2 d，给予16只大鼠热休克反应处理（热休克反应组），16只大鼠硫酸锌腹腔注射（硫酸锌注射组）。观察及比较治疗前后各组大鼠眼压、RGCs中HSP72抗体含量、RGCs平均密度。结果　激光后3 d、7 d、14 d、28 d，各组大鼠右眼眼压均较激光前有所上升，且各组间差异均无统计学意义（均为P>0.05）。正常对照组大鼠不同时间点HSP72抗体在RGCs中无表达，激光后3 d实验组各组大鼠RGCs中HSP72抗体含量缓慢上升，7 d、14 d达高峰，此后逐渐下降至接近正常水平。激光后，实验组各组大鼠RGCs中HSP72抗体含量显著高于正常对照组，且热休克反应组RGCs中HSP72抗体含量均高于实验对照组，低于硫酸锌注射组，差异均有统计学意义（均为P<0.05）。激光后3 d、7 d、14 d、28 d实验组各组大鼠RGCs平均密度均明显低于正常对照组，且热休克反应组RGCs平均密度显著高于实验对照组和硫酸锌注射组，差异均有统计学意义（均为P<0.05）。结论　热休克蛋白反应可在青光眼模型大鼠RGCs中诱导HSP72的生成，且对青光眼性RGCs和视神经具有保护作用。     

Dorzolamide and timolol saves retinal ganglion cells in glaucomatous adult rats.

PURPOSE: This study was designed to evaluate the effects of a dorzolamide-timolol combination or dorzolamide on retinal ganglion cell (RGC) density and intraocular pressure (IOP) in glaucomatous eyes of adult rats. METHODS: Glaucoma was induced in the right eye of adult Wistar rats by episcleral venous occlusion. One experimental group was administered dorzolamide 2%-timolol 0.5% combination eye drops, while the other experimental group was administered dorzolamide 2% eye drops. Control groups had surgery without drug administration. Drug application was initiated either 2 weeks before surgery (Group A), from the day of surgery (Group B), 2 weeks after surgery (Group C), or 4 weeks after surgery (Group D). RGCs were labeled by intratectal Fluorogold injections and counted from flat-mount preparations, and IOP was measured using Tonopen. RESULTS: Both dorzolamide-timolol combination and dorzolamide, when applied topically, significantly reduced IOP and improved RGC densities in experimental eyes when compared to control eyes. Earlier initiation, as well as longer duration of drug application, resulted in higher RGC densities. CONCLUSIONS: Topical application of a dorzolamide-timolol combination or dorzolamide saved RGCs to a significant extent and reduced IOP in glaucomatous rat eyes.     

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.     

Heat Shock Protein 72 Protects Retinal Ganglion Cells in Rat Model of Acute Glaucoma

Purpose: To investigate whether the induction of heat shock protein (HSP)72 by heat stress (HS) or zinc (Zn2 ) administration can increase survival of retinal ganglion cells (RGC)in rat model of acute experimental glaucoma. Methods: Acute glaucoma model was made by intracameral irrigation with BSS at 102 mmHg for two hours in right eyes of male Wistar rats. Glaucoma model rats were treated with HS once a week (six rats) or intraperitoneal injection of zinc sulfate (24.6 mg/kg) every two weeks (six rats), and were referred to as HS group and zinc group, respectively. Untreated model rats served as damage group (six rats). In control groups, querc-etin (400 mg/kg) was intraperitoneally injected to inhibit the induction of heat shock proteins 6 hours before HS or zinc administration, and were referred to as HS que group (six rats) and zinc que group (six rats), respectively. Subsequent to 16 days of IOP elevation, the rats were sacrificed. Eyes were quickly enucleated, and the retinas were dissected. RGC were labeled with Nissl staining and counted under microscope. Results: The average RGC density in normal Wistar rats was (2504±181) cells/mm2. In damage group, it decreased to (2015±111) cells/mm2. The RGC densities at 1,2, and 3 mm from the center of the optic nerve head were (2716±215), (2496±168), and (2317±171) cells/mm2, respectively, for normal rats and (2211±133), (1969±154), and (1872±68) cells/mm2, respectively, for damage group. The latter was significantly lower at all locations compared with the former (P=0.027 for each, Mann-Whitney test). The average RGC densities were (2207±200) cells/mm2 for HS group, (2272±155) cells/mm2 for zinc group, (1964±188) cells/mm2 for HS que group, (2051 ±214) cells/mm2 for zinc que group and (2015±111) cells/mm2for damage group. There were significant differences in density of labeled RGCs among the five groups (P=0.040, Kruskal-Wallis test). Both HS and zinc group had higher RGC densities than damage group (P =0.036 between HS and damage group,P=0.019 between zinc and damage group,Mann-Whitney test). There was no significant difference in RGC densitiy between control groups and damage group (P=0.260 between HS que and damage group,P=0.748 between zinc que and damage group, Mann-Whitney test). Conclusions: The results demonstrated that the induction of HSP72 in RGCs by HS or zinc administration plays an important role in the survival of RGCs in rat model of acute glaucoma. A novel therapeutic approach to glaucoma through an enhanced induction of endogenous HSP72 could be possible. Eye Science 2005;21:163-168.     

Characterization of retinal damage in the episcleral vein cauterization rat glaucoma model

Episcleral vein cauterization (EVC) is used in rats to generate a glaucoma model with high intraocular pressure (IOP). The long-term retinal damage in this glaucoma model, however, has not been accurately quantified. We report the location and amount of retinal ganglion cell (RGC) damage caused by (EVC) induced IOP elevation in two rat strains. IOP was raised in one eye of Wistar (N = 5) and Brown-Norway(B-N)(N = 7) rats by EVC and monitored monthly until IOP in contralateral eyes equalized at 5 months post-surgery. Animals were maintained for 3.5-4.5 additional months. B-N rats (N = 7) that had no EVC served as controls for this strain. Scotopic flash ERGs were recorded at baseline and just prior to euthanasia. Automated counts of all retrogradely labeled RGCs in retinal flat-mounts were determined and compared between contralateral eyes. RGC density maps were constructed and RGC size distribution was determined. Oscillatory potentials in the group of eyes which had elevated IOP were decreased at the time of euthanasia, when IOP had returned to normal. The group of normal B-N rats had similar RGC counts between contralateral eyes. In the experimental group the mean number of RGCs was not significantly different between control and experimental eyes, but 1 of 5 Wistar and 2 of 7 B-N experimental eyes had at least 30% fewer RGCs than contralateral control eyes. Total retinal area in B-N experimental eyes was higher compared to contralateral eyes. Cumulative IOP exposure of the experimental eyes was modestly correlated with RGC loss while oscillatory potentials appeared to be inversely related to RGC loss. In retinas with extensive (> 30% RGC loss) but not complete damage, smaller cells were preserved better than larger ones. The above results indicate that RGC loss in both Wistar and B-N strains is variable after a prolonged elevation of IOP via EVC. Such variability despite equivalent IOP levels and ERG abnormalities, suggests unknown factors that can protect IOP-stressed RGCs. Identification and enhancement of such factors could prove useful for glaucoma therapy.     

鼠青光眼模型中热休克蛋白27的表达及其作用

目的:探讨热休克蛋白27(HSP27)在鼠青光眼模型视网膜神经节细胞(RGCs)中的表达以及眼压对抗HSP27自身抗体的影响。方法:使用SPSS12.0软件将55只Wistar大鼠随机分为高眼压组(25只鼠)、sham对照(假手术)组(25只鼠)及正常对照组(5只鼠)。采用电凝鼠巩膜表面至少3组静脉及角膜缘周围血管,建立鼠青光眼模型。采用免疫组化和酶联免疫吸附测定(ELISA)方法分别检测术后1,2,3,4及8wk视网膜中RGCs以及神经纤维层(RNFL)HSP27的表达、分布以及血清中抗HSP27抗体水平。结果:随着眼压升高及高眼压持续时间延长,高眼压组右眼RGCs中HSP27表达逐渐增强,与其左眼、sham对照组右、左眼和正常对照组右、左眼比较,差异均有统计学意义(P<0.001),且RNFL中也出现HSP27的表达。高眼压组血清中抗HSP27抗体水平在术后1wk轻度升高(P>0.05),随着眼压升高及高眼压持续至术后8wk,血清中HSP27抗体水平逐渐升高并稳定于较高水平,与sham对照组和正常对照组比较,差异有统计学意义(P<0.05)。结论:内源性HSP27表达增强可能在青光眼视神经病变中具有重要作用。     

Rat chronic glaucoma model induced by intracameral injection of microbeads suspended in sodium sulfate–sodium hyaluronate

Purpose

To establish a rat glaucoma model with chronic intraocular pressure (IOP) elevation induced by microbeads suspended in sodium sulfate–sodium hyaluronate.

Methods

Chronic elevation of IOP was induced unilaterally by injecting polystyrene microbeads, suspended in 4 % sodium sulfate and 3 % sodium hyaluronate, into the anterior chamber. The microbead suspension was injected through either the clear corneal (CC) or sclerocorneal (SC) tunnel. IOP changes were monitored up to 8 weeks after injection. The loss of retinal ganglion cells (RGCs) was assessed using fluorogold retrograde labeling of RGCs. RGC axons were evaluated by immunohistochemistry and immunoblotting.

Results

The resulting IOP elevation was maintained up to 3 weeks after the intracameral injection of microbeads through the CC route and up to 4 weeks after injection through the SC route. The density of RGCs was significantly reduced at 4 weeks after injection, with the SC route leading to more RGC loss than the CC route (p = 0.037). The neurofilament immunoreactivity and protein levels in the optic nerve were also significantly reduced at 4 weeks after injection. Some eyes in the SC route cohort received re-injection of the microbead suspension at 4 weeks after the initial injection, which led to an elevated IOP more than 8 weeks after the initial injection, and eventually a 27.5 % loss of RGC density compared with the control eyes.

Conclusion

The intracameral injection of microbeads suspended in hyaluronate effectively produced chronic IOP elevation and subsequent RGC degeneration in rat eyes. The sclerocorneal tunnel approach yielded a longer period of IOP elevation than the clear corneal approach. Our modified microbead injection offers a reliable high-pressure glaucoma model.     

慢性高眼压模型鼠视网膜神经节细胞及视神经中9位丝氨酸磷酸化糖原合酶激酶3β的表达变化

目的 观察慢性高眼压模型鼠视网膜神经节细胞(retina ganglion cells,RGCs)和视神经中9位丝氨酸磷酸化糖原合酶激酶3β[p-GSK3β(ser9)]的表达变化,探讨GSK3β是否在慢性高眼压RGCs及视神经退行性病变中发挥作用.方法 取健康SD大鼠30只,随机分为3组:模型对照组、慢性高眼压模型2周组、慢性高眼压模型4周组,每组10只.取大鼠右眼,采用巩膜上静脉结扎并烧灼法建立大鼠慢性高眼压模型.分别于造模后2周和4周取5只大鼠眼球行冰冻切片,尼氏染色观察RGCs数目,免疫荧光染色观察RGCs和视神经中p-GSK3β(ser9)的变化;各组取另外5只大鼠眼视网膜,Western blot检测p-GSK3β(ser9)及总-GSK3β的表达.结果 造模前3组大鼠右眼眼压差异无统计学意义(P=0.89);造模后3组间眼压差异有统计学意义(P＜0.01),慢性高眼压模型2周组和4周组眼压与模型对照组比较明显升高,分别升高了59.13％和26.93％,差异均有统计学意义(均为P＜O.01).视网膜尼氏染色RGCs计数发现模型对照组RGCs数为(149±12)个,慢性高眼压模型2周组和4周组RGCs数较模型对照组明显减少,分别为(120±10)个和(86±7)个,差异均有统计学意义(均为P＜0.05);且4周组比2周组进一步减少(P＜0.01).慢性高眼压模型2周组和4周组视网膜中p-GSK3β(ser9)阳性着色,同模型对照组相比,其RGCs层及视神经中p-GSK3β(ser9)染色荧光减弱;4周组较模型对照组减弱更明显.与模型对照组相比,慢性高眼压模型2周组和4周组视网膜中总-GSK3β的表达差异无统计学意义(F=0.24,P=0.79);而3组间p-GSK3β(ser9)表达差异有统计学意义(P＜0.01),与模型对照组相比,慢性高眼压模型2周组和4周组视网膜中p-GSK3β(ser9)分别减少了19.89％和36.46％(均为P ＜0.05).慢性高眼压模型4周组比2周组视网膜中p-GSK3β(ser9)表达持续减少,差异具有统计学意义(P＜0.05).结论 慢性高眼压模型鼠RGCs数目减少,RGCs和视神经中p-GSK3β(ser9)表达减少,推测p-GSK3β(ser9)表达变化可能参与了慢性高眼压模型鼠RGCs及视神经退行性病变.     

Changes of aqueous vascular endothelial growth factor and pigment epithelium-derived factor following intravitreal bevacizumab for macular oedema secondary to branch retinal vein occlusion

Background:  To investigate sequential changes of aqueous vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF) in macular oedema secondary to branch retinal vein occlusion (BRVO) following intravitreal injection of bevacizumab (IVB).
Methods:  We recruited 10 healthy controls and 40 patients with BRVO. Aqueous levels of VEGF and PEDF were measured by ELISA at the time of IVB and 6 weeks later. Non-response to IVB was defined as showing persistent macular oedema based on reduction of central macular thickness by less than 20% from baseline measurements by optical coherence tomography and vision improvement by <0.3 logMAR at 6 weeks after IVB. Fluorescein angiography was performed after resolution of foveal haemorrhage. We compared aqueous levels of VEGF and PEDF between responders and non-responders.
Results:  The aqueous levels of VEGF and PEDF were significantly higher in 16 non-responders than in 24 responders at baseline measurements (491 ± 231 pg/mL vs . 250 ± 112 pg/mL, P  < 0.001; 32 ± 4 ng/mL vs . 25 ± 5 ng/mL, P  < 0.001, respectively). Six weeks after IVB, the aqueous levels of VEGF and PEDF were still higher in non-responders than in responders (388 ± 141 pg/mL vs . 104 ± 40 pg/mL, P  < 0.001; 30 ± 8 ng/mL vs . 18 ± 5 ng/mL, P  < 0.001, respectively). Fluorescein angiography revealed that non-responders showed higher frequencies of macular ischaemia and ischaemic BRVO.
Conclusions:  Our results indicate that aqueous VEGF levels are associated with persistent macular oedema secondary to ischaemic BRVO following IVB.     

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.