内源性促红细胞生成素对大鼠脱离视网膜光感受器细胞的保护作用

背景促红细胞生成素（EPO）对多种视网膜疾病模型中视网膜神经元具有一定的保护作用,但EPO对视网膜脱离（RD）后光感受器细胞是否具有保护作用尚不清楚。目的探讨内源性EPO对RD状态下光感受器细胞的保护作用及可能机制。方法利用视网膜下腔注射质量分数1．4％透明质酸钠建立大鼠RD模型,按每组情况各组玻璃体腔内分别单次注射PBS或不同剂量的外源性可溶性EPO受体（EPOsR）,采用计算机产生随机数字法将72只SD大鼠随机平均分为正常对照组、RD组、RD＋PBS组、RD＋EPOsR2、20、200ng组。分别于造模后3d和14d用过量麻醉法处死大鼠并获得大鼠视网膜标本,采用末端脱氧核苷酸转移酶介导的dUTP缺口末端标记（TUNEL）法检测光感受器细胞的凋亡情况,并分别采用Westernblot和免疫荧光法检测视网膜中caspase-3的活性,RD造模后14d进行组织病理学检查并测量外核层（ONL）厚度。结果RD造模后3d,RD组ONL出现凋亡细胞核,玻璃体腔注射EPOsR组光感受器细胞凋亡进一步增加,随着玻璃体腔注射EPOsR的剂量增加,ONL凋亡细胞核有增加趋势。Westernblot和免疫荧光检测结果均显示,各组视网膜caspase-3表达的条带灰度值分别为（0．15±0．04）、（0．49±0．03）、（0．50±0．07）、（0．63±O．03）、（0．69±0．04）、（0．83±0．04）,各组的总体差异有统计学意义（F=76．016,P=0．000）,RD＋EPOsR200ng组的caspase-3活性均强于其他各组,差异均有统计学意义（P〈0．01）。RD造模后14d,正常对照组、RD组、RD＋PBS组、RD＋EPOsR2、20、200ng组的ONL厚度分别为（47．39±3．39）、（33．96±3．54）、（31．83±5．21）、（31．40±2．63）、（24．99±2．06）、（19．30e3．71）μm,总体差异有统计学意义（F=44．733;P=0．000）;EPOsR处理组ONL厚度明显薄于单纯RD组和RD＋PBS组,差异均有统计学意义（P〈0．05）。结论RD状态下,EPOsR通过剂量依赖的方式诱导视网膜细胞的凋亡和caspase-3活性增强,而缺氧状态下视网膜神经上皮的内源性EPO表达增强可通讨抑制casDase-3活性和抗凋亡作用发挥对光感受器细胞的保护作用。     

bcl-XL抗视网膜光感受器细胞凋亡作用的实验研究

目的评价抗凋亡基因bcl-XL对视网膜光感受器细胞的抗凋亡作用.方法首先建立谷氨酸损伤的SD大鼠视网膜光感受器细胞凋亡模型.将体外培养的光感受器细胞分为A组(正常对照组)、B组(谷氨酸组)及C组(rAd-gfp-bcl-XL转染+谷氨酸组);其中C组在加入谷氨酸前48 h用滴度为6.5×l012 pfu/mL的重组腺病毒rAd-gfp-bcl-XL转染光感受器细胞;荧光显微镜下观察光感受器细胞中的绿色荧光蛋白表达情况;用免疫组化法分析rAd-gfp-bcl-XL转染细胞和未转染细胞Bcl-XL蛋白水平;DNA琼脂糖凝胶电泳以评判3个组神经元凋亡发生与否及凋亡程度;采用Hoechst33258染色做正常核和凋亡核的形态学检测.结果免疫组化检测结果表明转染细胞与未转染细胞的Bcl-XL蛋白表达水平有差异,DNA电泳分析发现B组呈典型的DNA"梯度"条带,而A组和C组几乎无DNA"梯度"条带,核形态学检测结果亦证实转染组较未转染组的核有明显差异.结论重组腺病毒介导转染的bcl-XL对体外培养的视网膜光感受器细胞有抗凋亡作用,提高视网膜光感受器细胞bcl-XL的表达水平可能为视网膜变性疾病提供潜在有效的治疗方法.     

重组腺病毒介导的gfp-bcl-XL对视网膜变性鼠光感受器细胞保护作用的研究

目的 观察重组腺病毒rAd-gfp-bcl-XL治疗视网膜变性(retinal degeneration,RD)鼠的疗效。方法 40只RD鼠随机分成A、B组,每组20只,右眼为治疗眼,左眼为对照眼。A、B组治疗眼分别于RD鼠生后10d及22d视网膜下腔注射含绿色荧光蛋白基因gfp和抗凋亡基因bcl-XL的重组腺病毒颗粒;术后15、30d摘除治疗眼和对照眼行冰冻切片、透射电镜下观察、石蜡切片、HE染色并提取视网膜总RNA;行逆转录聚合酶链反应分析bcl-XL基因的mRNA表达水平;免疫组化分析治疗眼和对照眼的Bcl-XL蛋白水平。结果 治疗眼视网膜有较广泛的绿色荧光蛋白表达,说明重组腺病毒成功的将bcl-XL转染至视网膜光感受器细胞,且有bcl-XL表达;术后30d,A组鼠治疗眼和对照眼bcl-XL的mRNA表达水平及Bcl-XL蛋白含量有明显差异;透射电镜下可见治疗眼的内节段较对照眼完好;HE染色示治疗眼视网膜光感受器细胞层较对照眼厚。而B组鼠治疗眼和对照眼的视网膜光感受器细胞层的厚度无明显差异。结论 注射至早期RD鼠视网膜下腔中的rAd-gfp-bcl-XL能有效转染光感受器细胞并发挥抗凋亡作用,但对晚期RD鼠的疗效不明显。     

碱性成纤维细胞生长因子对鸡近视眼视网膜细胞凋亡的影响

目的:探讨外源性碱性成纤维细胞生长因子(basicfibrob-lastgrowthfactor,bFGF)对鸡形觉剥夺性近视眼视网膜细胞凋亡及眼球屈光状态的影响。方法:缝合1日龄雄性海兰鸡的单眼建立形觉剥夺性近视眼模型,10wk后开始玻璃体注射bFGF5ng(10μL),3d1次。鸡12wk龄时,检影验光测眼球屈光度、游标卡尺测眼轴长度,末端脱氧核糖核苷酸连接酶介导的生物素化脱氧尿苷酸末端标记(TdT-mediatedbiotin-dUTPnick-endlabelling,TUNEL)技术检测视网膜的凋亡细胞,以Ac-DEVD-pNA为底物的比色法测定视网膜caspase-3活性。结果:鸡眼睑缝合12wk后,缝合眼眼轴延长,形成高度近视眼,缝合眼视网膜caspase-3活性高于正常对照眼(P<0.05),TUNEL技术在缝合眼视网膜内、外核层检测到凋亡细胞。5ngbFGF玻璃体注射后,缝合眼近视程度减轻,视网膜内、外核层的凋亡细胞减少和caspase-3活性下调(P<0.05)。结论:玻璃体注射bFGF能下调视网膜caspase-3活性而抑制视网膜细胞凋亡,还能抑制鸡形觉剥夺性近视眼形成。     

Rhodopsin和recoverin在MNU诱导的光感受器损伤中的表达变化

目的：观察N-甲基-N-亚硝基脲( MNU)诱导的大鼠视网膜光感受器损伤过程中Rhodopsin 和recoverin表达变化与损伤的时效关系。
　　方法：将36只SPF级7周龄大鼠随机分为正常对照组, MNU模型组(6h组,12h组,24h组,3d组,7d组),每组各6只。模型组一次性腹腔注射60mg/kg MNU,正常对照组腹腔注射等量PBS。右眼行HE,TUNEL,透射电镜评估视网膜组织损伤的超微结构变化及细胞凋亡程度,左眼取视网膜组织通过Western blot和免疫荧光观察视网膜组织中Rhodopsin和recoverin的mRNA表达变化。
　　结果：透射电镜观察到MNU注射12 h 后出现凋亡小体,24 h后外核层大部分细胞呈阳性反应;TUNEL 检测发现MNU注射24 h 光感受器细胞凋亡指数最高,达(29.7±2.3)%,与电镜结果吻合。 Western blot 结果表明, MNU注射12 h后表达有极显著性差异( P<0.01),而Recoverin的表达从注射后24h有极显著性差异(P<0.01)。
　　结论：一次性腹腔注射60 mg/kg MNU能特异性诱导SD大鼠视网膜光感受器细胞凋亡, Rhodopsin和recoverin表达下调与MNU诱导光感受器细胞的选择性凋亡有关。     

rd小鼠遗传性视网膜变性中内质网应激蛋白的激活

目的 探讨rd小鼠遗传性视网膜变性光感受器细胞变性凋亡中内质网应激反应蛋白的表达变化.方法 实验研究.取出生后8、10、12、14、24 d的rd小鼠和同年龄段的正常对照C3B小鼠.免疫印迹法检验视网膜中GRP78/BiP、半胱天冬酶-12酶原(procaspase-12)和活性caspase-12、p-PERK、p-eIF2a蛋白表达变化.免疫荧光染色共聚焦显微镜观测GRP78/BiP、caspase-12、p-PERK和p-eIF2a的表达部位及表达量的变化.用SPSS单因素方差分析对数据进行统计学分析,以P＜0.01为差异有统计学意义.结果 伴随rd小鼠遗传性视网膜变性过程免疫印迹结果显示GRP78/Bip、半胱天冬酶-12酶原和活性caspase-12、p-PERK、p-eIF2a蛋白的表达上调,与正常对照组之间的差异具有统计学意义(F=65.82,55.76,152.29,50.54,20.91;P＜0.05);免疫荧光染色结果显示GRP78/Bip、easpase-12、p-PERK和p-eIF2a主要表达于视网膜光感受器细胞的内节和光感受器细胞核中.结论 在rd小鼠遗传性视网膜变性光感受器细胞变性凋亡中,内质网应激反应蛋白的激活对于光感受器细胞的凋亡具有重要作用.应用内质网应激反应调节剂可能对此类疾病起到有效治疗作甩.     

急性心肌缺血诱发应激反应对大鼠视网膜细胞凋亡的影响

目的 采用细胞凋亡率和半胱氨酸天冬蛋白酶3(caspase-3)活性为观察指标,观察急性心肌缺血诱发机体急性应激反应对大鼠视网膜细胞凋亡的影响. 方法 将健康成年雄性SD大鼠24只分为两组.对照组:穿线不结扎冠状动脉;冠状动脉结扎组:结扎冠状动脉左前降支.每组根据观察时点又分为3h、6h两个亚组.在预定时间分别取大鼠一眼做石蜡切片后进行TUNEL染色;取另一眼视网膜,进行caspase-3活性检测.TUNEL染色以凋亡指数(染色阳性细胞占所计数细胞总数的百分比)表示,Caspase-3采用活性表示. 结果 与对照组比较,结扎冠状动脉3h、6h视网膜细胞凋亡指数均明显升高(P=0.004,P<0.05),且阳性细胞主要出现于视网膜的神经节细胞层和内核层;Caspase-3活性均明显升高(P=0.001,P<0.05). 结论 急性心肌缺血诱发的急性应激反应可引发大鼠视网膜细胞凋亡增加,凋亡主要出现在视网膜神经节细胞层和内核层.     

视网膜脱离模型中外源性促红细胞生成素对其受体表达的影响

目的探讨外源性促红细胞生成素（EPO）对促红细胞生成素受体（EPOR）在脱离的视网膜中表达的影响。方法通过视网膜下腔注射质量分数1.4%透明质酸钠在60只SD大鼠的右眼建立视网膜脱离（RD）模型,12只正常SD大鼠为正常对照组。不同组RD模型眼（每组12只眼）玻璃体腔内分别注射PBS或100、200、400ng重组大鼠源性EPO。玻璃体注射后3d应用Westernblot法半定量检测各组SD大鼠脱离的视网膜中EPOR蛋白表达水平的变化并进行比较,应用免疫组织化学法定位检测脱离的视网膜中EPOR蛋白的表达。结果 Westernblot检测结果表明大鼠正常视网膜中EPOR表达量少,为0.28±0.02;造模后3d,EPOR在脱离的视网膜中表达量明显增加,为0.41±0.05,差异有统计学意义（P〈0.05）。RD＋PBS组、RD＋EPO100ng组、RD＋EPO200ng组和RD＋EPO400ng组EPOR蛋白的表达量分别为0.39±0.03、0.41±0.03、0.43±0.07、0.44±0.05,明显高于对照组,差异均有统计学意义（P〈0.05）,但RD＋PBS组、RD＋EPO100ng组、RD＋EPO200ng组和RD＋EPO400ng组间EPOR蛋白的表达差异均无统计学意义（P〉0.05）。RD组与RD＋不同剂量EPO组比较EPOR表达的差异无统计学意义（P〉0.05）。免疫组织化学检测结果证实EPOR蛋白表达于视网膜各层,RD＋不同剂量的EPO处理组EPOR表达均强于正常对照组。结论 RD发生后补充外源性EPO对EPOR的表达并无影响。     

促红细胞生成素与促红细胞生成素受体在大鼠脱离视网膜中的表达

目的 观察促红细胞生成素（EPO）和促红细胞生成素受体（EPOR）在大鼠脱离视网膜中的表达情况。方法48只雄性SD大鼠,随机分为正常对照组、视网膜脱离（RD）后1、3、6、12、24、48、72 h组,每组6只大鼠12只眼。视网膜下腔单次注射1.4%透明质酸钠致上半侧视网膜隆起建立RD模型,采用逆转录聚合酶链式反应（RT-PCR）和蛋白免疫印迹（Western blot）测定不同时间点EPO和EPOR的mRNA和蛋白水平的表达情况,同时采用免疫组织化学方法观察EPO和EPOR在视网膜中定位表达的情况。结果 EPO和EPOR的mRNA表达水 平在RD后均上调,均于RD后48 h达到高峰,分别于RD后6、12 h显著高于正常对照组,差异具有统计学意义（P＜0.05）;同样,EPO和EPOR的蛋白表达水平也在RD后均增高并在RD后48 h达到高峰,均于RD后3 h显著高于正常对照组,差异具有统计学意义（P＜0.05）。免疫组织化学结果显示正常视网膜自神经节细胞层至光感受器细胞的内外节均有EPO弱表达,RD后48 h视网膜相应部位呈强阳性表达;正常视网膜自神经节细胞层至光感受器细胞的内节均有EPOR表达,RD后48 h视网膜相应部位呈强阳性着染。结论 RD后大鼠视网膜EPO和EPOR表达均逐渐增强,48 h达到高峰;大鼠神经视网膜大部分层次能表达EPO和EPOR。     

TLR-4/MyD88通路激活和小胶质细胞极化在氧化低密度脂蛋白导致的小鼠视网膜损伤中的作用

目的 探讨氧化低密度脂蛋白(ox-LDL)导致的视网膜损伤是否与Toll样受体-4(TLR-4)/MyD88通路激活和活化小胶质细胞使其极化为M1表型相关。方法 雄性C57BL/6小鼠分为两组,实验组小鼠视网膜下注射1μL ox-LDL,对照组小鼠注射等体积的磷酸盐缓冲液(PBS);2周后,采用免疫荧光染色检测视网膜小胶质细胞的离子钙结合适配器分子1(Iba-1)、iNOS的表达,TUNEL染色检测光感受器细胞凋亡,OCT检测视网膜外核层(ONL)和内核层(INL)厚度,ERG检测视网膜功能,qPCR检测视网膜Iba-1、TLR-4和MyD88的mRNA和蛋白表达。体外实验使用ARPE-19细胞,ox-LDL组细胞用100 mg·L^-1 ox-LDL处理24 h, PBS组细胞使用等体积的PBS处理24 h; TUNEL染色检测细胞凋亡,Western blot和qPCR检测细胞TLR-4和MyD88的mRNA和蛋白表达。结果 qPCR和Western blot检测结果均显示,与对照组相比,实验组小鼠视网膜中TLR-4、MyD88、Iba-1的mRNA和蛋白表达水...     

Safety and efficacy of intravitreal injection of recombinant erythropoietin for protection of photoreceptor cells in a rat model of retinal detachment

Purpose

To elucidate the safety and efficacy of exogenous erythropoietin (EPO) for the protection of photoreceptor cells in a rat model of retinal detachment (RD).

Methods

Recombinant rat EPO (400 ng) was injected into the vitreous cavity of normal rats to observe the eye manifestations. Retinal function was assessed by flash electroretinograms. Histopathological examination of retinal tissue was performed at 14 days and 2 months after injection, respectively. To investigate the inhibitory effect of EPO on photoreceptor cell apoptosis in RD rats, 100, 200, or 400 ng EPO was injected into the vitreous cavity immediately after RD model establishment. Apoptosis of photoreceptor cells was determined at 3 days after injection. Caspase-3 activation was measured by western blot analysis and immunofluorescence, respectively, and the level of Bcl-X_L expression was analyzed by western blot.

Results

Intravitreal injection of EPO 400 ng into normal rats had no significant impact on retinal function, morphology, or structure. Apoptosis of retinal photoreceptor cells apparently increased after RD and was significantly reduced following EPO treatment. The thickness of the outer nuclear layer in the RD+400 ng group was significantly thicker than that in other experimental RD groups both at 14 days and at 2 months after RD (P<0.05). Western blot and immunofluorescence analyses showed decreased caspase-3 activation and increased Bcl-X_L expression following EPO treatment.

Conclusion

Intravitreal injection of EPO 400 ng is safe, and EPO may suppress caspase-3 activation and enhance Bcl-X_L expression, resulting in inhibition of apoptosis and protection of photoreceptor cells.     

Neuroprotective effects of lutein in a rat model of retinal detachment

Background

Retinal detachment (RD) is a leading cause of blindness, and although final surgical re-attachment rate has greatly improved, visual outcome in many macula-off detachments is disappointing, mainly because of photoreceptor cell death. We previously showed that lutein is anti-apoptotic in rodent models of ischemia/reperfusion injury. The objective of this study is to investigate lutein as a possible pharmacological adjunct to surgery.

Methods

Subretinal injections of 1.4 % sodium hyaluronate were used to induce RD in Sprague–Dawley rats until their retinae were approximately 70 % detached. Daily injections of corn oil (control group) or 0.5 mg/kg lutein in corn oil (treatment group) were given intraperitoneally starting 4 h after RD induction. Animals were euthanized 3 days and 30 days after RD and their retinae were analyzed for photoreceptor apoptosis and cell survival at the outer nuclear layer (ONL) using TUNEL staining and cell counting on retinal sections. Glial fibrillary acidic protein (GFAP) and rhodopsin (RHO) expression were evaluated with immunohistochemistry. Western blotting was done with antibodies against cleaved caspase-3, cleaved caspase-8 and cleaved caspase-9 to delineate lutein’s mechanism of action in the apoptotic cascade. To seek a possible therapeutic time window, the same set of experiments was repeated with treatment commencing 36 h after RD.

Results

When lutein was given 4 h after RD, there were significantly fewer TUNEL-positive cells in ONL 3 days after RD when compared with the vehicle group. Cell counting showed that there were significantly more nuclei in ONL in lutein-treated retinae by day 30. Treatment groups also showed significantly reduced GFAP immunoreactivity and preserved RHO expression. At day 3 after RD, Western blotting showed reduced expression of cleaved caspase-3 and cleaved caspase-8 in the treatment group. No difference was found for cleaved caspase-9. When lutein was given 36 h after RD similar results were observed.

Conclusions

Our results suggest that lutein is a potent neuroprotective agent that can salvage photoreceptors in rats with RD, with a therapeutic window of at least 36 h. The use of lutein in patients with RD may serve as an adjunct to surgery to improve visual outcomes.     

Minocycline partially inhibits caspase-3 activation and photoreceptor degeneration after photic injury

PURPOSE: To evaluate the possible role of caspase-3 in retinal photic injury, and to investigate whether minocycline can ameliorate light-induced photoreceptor degeneration. METHODS: Retinal photic injury was induced in rats by exposure to intense light. Expression of caspase-3 was studied using Western blot analysis, immunohistochemical staining and enzyme activity assay. Apoptotic photoreceptor cells were detected by the TdT-dUTP terminal nick-end labeling (TUNEL) method. Minocycline (15, 30 or 45 mg/kg) was administered before or after photic injury in rats randomly assigned to pretreatment and posttreatment groups. Minocycline and vehicle-treated retinas subjected to photic injury were compared with respect to Western blotting, enzyme activity assay, quantitative counts of TUNEL stains, morphometry of the outer nuclear layer (ONL) thickness and histopathological examination. RESULTS: After light exposure, active caspase-3 and poly-adenosine diphosphate-ribose-polymerase were upregulated in the retinas and increased caspase-3 immunoreactivity was observed in the ONL. Caspase-3 enzyme activity increased in the retinas that underwent photic injury, and this increase was significantly reduced in minocycline pretreated (30 and 45 mg/kg) and posttreated (45 mg/kg) groups. Intraperitoneal administration of minocycline before or after photic injury in rats also resulted in less TUNEL-positive photoreceptors, as assessed by the quantitative TUNEL counts. The degree of retinal degeneration, measured by the ONL thickness 14 days after photic injury, was significantly improved in minocycline pretreatment (45 mg/kg) rats. CONCLUSIONS: We demonstrate that increased caspase-3 activities localize specifically within the ONL after photic injury, and that minocycline partially inhibits caspase-3 activation and photoreceptor degeneration in this animal model.     

Gene therapy for detached retina by adeno-associated virus vector expressing glial cell line-derived neurotrophic factor

PURPOSE: To examine the protective effect of glial cell line-derived neurotrophic factor (GDNF) on retinal detachment (RD)-induced photoreceptor damage by using gene delivery. METHODS: Gene delivery to photoreceptors was achieved by subretinal injection of recombinant adeno-associated virus expressing GDNF (rAAV-GDNF) in the right eyes and AAV expressing Escherichia coli LacZ (rAAV-LacZ) in the left eyes of Lewis rats. RD in bilateral eyes was induced with subretinal injection of high-density vitreous substitute in the temporal retina 3 weeks after gene delivery. The synthesis and accumulation of GDNF within the retina was monitored 3 weeks after RD by immunohistochemistry and enzyme-linked immunosorbent assay (ELISA), respectively. The rescue of photoreceptors was evaluated by monitoring the preservation of the thickness of photoreceptor outer segment (OS) and outer nuclear layer (ONL). Apoptosis in the photoreceptors was studied using the TdT-dUTP terminal nick-end labeling (TUNEL) method 2 days after RD. Müller cell activity was checked using the immunohistochemistry with glial fibrillary acidic protein (GFAP) antibody 28 days after RD. RESULTS: Gene delivery was demonstrated by immunohistochemical study. The results of ELISA confirmed that high levels of neurotrophic factors were produced in retinas. Photoreceptor OS degeneration and the gradual shortening of the ONL were noted after RD in all the eyes. However, rAAV-GDNF-treated eyes retained longer OS than rAAV-LacZ-treated eyes 7 (P = 0.012) and 28 days (P = 0.008) after RD. ONL was also longer in rAAV-GDNF-treated eyes than in rAAV-LacZ-treated eyes 7 (P = 0.012) and 28 days (P = 0.008) after RD. GDNF-treated eyes had statistically less apoptotic cells than control eyes in photoreceptor layer (P = 0.043). Subretinal proliferation of Müller cells was suppressed in the GDNF-treated group, indicating less scar formation. CONCLUSIONS: GDNF is a potential factor that can protect photoreceptors from degeneration. In addition to preserving the OS and ONL structures, GDNF may exert its protective action by preventing the apoptosis of photoreceptors after RD. GDNF gene therapy may be a valuable adjuvant to current treatments in certain complicated forms of RD.     

Viral delivery of heme oxygenase-1 attenuates photoreceptor apoptosis in an experimental model of retinal detachment

This study was designed to evaluate the efficacy of subretinal injection of recombinant adeno-associated virus vector expressing heme oxygenase-1 (rAAV-HO-1) in attenuating photoreceptor apoptosis induced by experimental retinal detachment (RD) in Sprague-Dawley rats. Our results disclosed that subretinal rAAV-HO-1 delivery achieved localized high HO-1 gene expression in retinal outer nuclear layer (ONL) compared with rAAV-lacZ-injected eyes and eyes with RD left untreated both at 2 (p = 0.003) and 28 (p = 0.007) days of RD. The ONL thickness (p = 0.018) and mean photoreceptor nuclei count (p = 0.009) in eyes receiving rAAV-HO-1 injection was significantly higher than in rAAV-lacZ-injected or eyes with RD left untreated at 28 days of RD. There were fewer apoptotic photoreceptor nuclei at 2 (p = 0.008) and 5 (p = 0.018) days of RD and less activated caspase-3 expression (p = 0.008) at 2 days of RD in rAAV-HO-1 treated eyes than in control eyes. These data supported that gene transfer approach might attenuate photoreceptor apoptosis caused by RD with a resultant better ONL preservation.     

Retardation of photoreceptor degeneration in the detached retina of rd1 mouse

PURPOSE: To study the neuroprotective effect of experimental retinal detachment (RD) on photoreceptor degeneration in rd1 mice. METHODS: RD was produced in the eyes of rd1 mice at postnatal day (P) 9. These eyes were collected and compared to controls without RD. The effects of RD on retinal degeneration were evaluated by histochemical staining of nuclei in the outer nuclear layer (ONL), rod and cone photoreceptors, and retinal vessels at P30 in retinal sections and flatmounts. Apoptotic photoreceptors were detected by TdT-mediated dUTP nick-end labeling (TUNEL) at P15. Mice with or without RD were also reared in darkness and evaluated immunohistochemically at P30. RESULTS: The numbers of rhodopsin-positive (rod), peanut agglutinin-positive (cone), and diamino-2-phenyl-indol-stained (rod-plus-cone) cells in the ONL were increased by 2.0-fold, 1.3-fold, and 1.2-fold, respectively, in the rd1 eyes with RD compared to those without RD at P30. In the detached retina, the cone photoreceptor inner/outer segment structures and the deep retinal vessels surrounding the inner nuclear layer and the ONL, but not the ganglion cell layer, were preserved. At P15, TUNEL-positive cell numbers in the ONL were significantly reduced in the eyes with RD. Light exposure had no effect on photoreceptor degeneration in the eyes with or without RD. CONCLUSIONS: RD mediates the preservation of cone and rod photoreceptors in the ONL and surrounding vascular structures by reducing the rate of apoptosis of photoreceptors in rd1 mice. Light deprivation does not appear to be one of the mechanisms of photoreceptor protection in the detached retinas in these mice.     

Preventing retinal detachment-associated photoreceptor cell loss in Bax-deficient mice

PURPOSE: To characterize photoreceptor cell apoptosis and cell loss in a mouse model of experimental retinal detachment (RD), and to use the technology of mouse genetics to study the molecular mechanisms underlying RD-associated photoreceptor degeneration. METHODS: Retinal detachments were created in adult wild-type and Bax-deficient mice by subretinal injection of 1.4% sodium hyaluronate. At 1, 3, 7, and 28 days after injection, animals were killed, eyes enucleated, and retinal sections studied by histochemistry, immunofluorescence labeling, and confocal microscopy. Rods and cones were labeled, and apoptotic cells were identified with terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL). Photoreceptor cell apoptosis and cell loss were assessed quantitatively by counting both surviving and TUNEL-positive rods and cones. RESULTS: TUNEL-positive cells were found within the outer nuclear layer (ONL) of the detached portions of the retina. They were detected in the detached retina on day 1, peaked on day 3, and dropped precipitously after day 7 after RD. Photoreceptor cell loss of both rods and cones followed a similar time course after RD. Moreover, deletion of the proapoptotic gene Bax in a knockout mouse model abolished the RD-associated photoreceptor cell degeneration. CONCLUSIONS: Apoptosis is a major mechanism leading to photoreceptor cell death after RD. Blockage of the activity of the proapoptotic molecule Bax in a knockout mouse model prevents photoreceptor cell apoptosis and cell loss. These data suggest that the Bax-mediated apoptotic signaling pathway plays a critical role in RD-associated photoreceptor cell death.     

银杏叶提取物对大鼠视网膜光损伤后感光细胞的保护作用

目的:探讨银杏叶提取物（EGb 761）对视网膜光损伤后感光细胞 的保护作用。 方法:72只Sprague-Dawley(SD)大鼠随机分为正常对照组 、模型组、模型+生理盐水组和模型+ EGb 761组，每组 各18只大鼠。模型组、模型+生理盐水组和模型+EGb 761组暗适应24 h后持续光照6 h，光照强度为（2740±120）lx ，建立光损伤模型。模型+EGb 761组和模型+生理盐水组分别于光照前7 d每日腹腔注射0.35 % EGb 761（100 mg/kg）和相应体积的生理盐水，光照后继续给药14 d；于光照后4 d对 各组进行视网膜原位凋亡细胞检测，并于光照后7、14 d作组织病理学检查并计数视盘 上、下方视网膜外核层（ONL）感光细胞层数。 结果:光照后4 d，除 正常对照组外，其余 各组ONL均出现凋亡感光细胞，但模型+ EGb 761组ONL凋亡感光细胞数明显少于模型组和模 型+生理盐水组。光照后7 d，模型组和模型+生理盐水组感光细胞核层数均为3~4层，模型+ EGb 761组为7~8层；模型+ EGb 761组平均感光细胞核层数（6.92 ± 0.82）少于正常对照 组（8.40±0.95）（t=-1.416，P＜0.05），但显著多于模型组（5.96±1.36）和 模型+生理盐水组（5.90±1.40）（t=1.024，1.084；P＜0 .05）。光照后14 d，模型 组和模型+生理盐水组感光细胞核为0~1层，而模型+ EGb 761组仍存有3~4层；模型+ EGb 76 1组平均感光细胞核层数（5.52±1.06）仍显著多于模型组（3.44±2.15）和模型+ 生理 盐水组（3.37±1.91）（t=2.082，2.146；P＜0.05）。 结论:EGb 761能部分抑制视网膜光损伤后感光细胞凋亡，对感光细胞具 有一定的保护作用。