视网膜色素变性的组织病理学改变

视网膜色素变性患者的眼前节即结膜、角膜、前房角和虹膜无病理改变，而病理改变是在眼后部，包括晶状体、玻璃体、视网膜、脉络膜、视乳头和视神经的异常，主要的病变发生在视网膜。在早期病例中，梗网膜的感光细胞发生变性和死亡，故病人表现夜盲。中心视力下降和视野缩窄。晚期病例，视网膜感觉层退变坏死，胶质细胞增生，视网膜瘢痕化，从而导致失明．视网膜色素上皮细胞继发性变性、消失，或局部增生，色素细胞迁移到赤道附近血管交叉的周围，形成骨针样色素沉着的典型眼底改变。 （中华眼底病杂志，1994，10：63-66）     

视网膜色素变性光感受器的组织病理学观察

目的：研究视网膜色素变性光感受器的组织病理学改变。 方法：对9例11眼视网膜色素变性的光感受器进行光学和电子显微镜观察。 结果：发现赤道部光感受器病理损害最明显，其次为周边区、后极部和黄斑。中期病例病理改变包括外节盘膜退变、变小和连接纤毛减少或消失；内节粗短、线粒体肿胀。晚期病例内、外节和纤毛消失，外界膜粘附在色素上皮细胞或Bruch膜上。光感受器细胞核减少、排列紊乱，细胞变性、结构破坏。移位的Müller细胞和增生肥大的细胞突占据了内外节和光感受器细胞核消失所遗留的空间。色素上皮细胞退变，部分消失或移位到视网膜内。结论：视网膜色素变性光感受器有明显损害。 （中华眼底病杂志，1996，12：160-162）     

兔胚胎全层视网膜移植至大鼠视网膜下的观察

视网膜色素变性(RP)是一组能导致进行性感光细胞变性和视觉障碍的遗传病症候群，目前尚无有效治疗方法。近年来研究表明视网膜移植是最接近临床应用治疗RP的方法。当RP进展到晚期，感光细胞和视网膜色素上皮(RPE)细胞都出现变性死亡，单独移植这两种成分都没有作用，此时病变视网膜的修复需要全层视网膜的移植。我们将青紫蓝兔胚胎全层视网膜移植到正常Wistar大鼠和视网膜变性RCS大鼠的视网膜下腔，观察移植物在宿主视网膜下腔的发育状况，从而探讨异种胚胎全层视网膜移植方法的可行性。     

病理性近视视网膜变性中感光细胞的凋亡

目的：了解凋亡在病理性近视视网膜感光细胞变性中所起的作用。 方法：9例病理性近视眼球被选作病理组织学和DNA断端标记即TUNEL技术研究。 结果：在其中的4个眼球，观察到凋亡的特征性改变—分散性的视网膜感光细胞DNA的片断化。 结论：结果提示凋亡是病理性近视视网膜感光细胞死亡的一个重要机制。 （中华眼底病杂志，1996，12：144-146）     

睫状神经营养因子对视网膜色素变性中感光细胞的作用

遗传性视网膜色素变性类疾病是人类的主要致盲眼病之一,目前尚无有效阻止病变进展和恢复视网膜功能的治疗方法.此类疾病的最后结果是感光细胞不可逆的凋亡.阻断感光细胞走向凋亡的进程是近年来研究的热点.在大量的体内外实验中发现,很多神经生长因子对遗传性视网膜色素变性类疾病有一定的治疗作用,其中睫状神经营养因子保护感光细胞、延缓感光细胞凋亡的作用颇受关注.本文就近年来睫状神经营养因子对视网膜色素变性疾病中感光细胞的作用研究作一综述.     

神经生长因子对糖尿病大鼠神经视网膜超微结构的影响

目的:通过观测实验性糖尿病动物的神经视网膜的超微结构变化,从视网膜的神经功能角度来探讨糖尿病视网膜病变的发生机制以及相关药物干预后的影响作用。方法:用链脲佐菌素制作糖尿病大鼠动物模型,分为正常对照组(CON组)、糖尿病对照组(DM组)、糖尿病神经生长因子治疗组(D+N组)。分别于病程3,6,9,12mo取大鼠眼球制备石蜡切片,将视网膜组织行HE染色,并将上述标本制备超薄切片,用透射电镜观察并分析。结果:从病程3mo开始,DM组视网膜血管内皮细胞及周细胞的核变形、线粒体肿胀变性、基底膜增厚。视神经节细胞水肿,胞器减少,线粒体变性。光感受器细胞(视锥、视杆)膜盘间隙扩大,线粒体及核也有病理改变。上述病变随病程延长而逐渐加重。经过NGF治疗后,上述DM改变有所减轻,主要表现在感光细胞外节膜盘间隙较DM组缩小,平行度好转;神经细胞突起水肿减轻,胞器水肿好转。各组DM大鼠的视网膜血管、神经网膜及视神经的糖尿病性病变之间未见明显的先后因果关系。结论:神经生长因子对DM大鼠视网膜形态学上所见的视网膜血管、感光细胞和神经节细胞的超微结构改变有着明确的改善作用。在DR的发病过程中,视网膜血管的病变与视网膜神经组织的病变可能是同时存在、互相促进,共同造成糖尿病视网膜病变和视功能的损害。     

犬周边部视网膜变性的病理改变

目的：观察犬周边部视网膜变性的特征，并探讨其与人类周边部视网膜变性的异同。 方法：随机对40头犬80只眼球的周边眼底作解剖显微镜观察，对变性灶照相后，经病理加工作光学显微镜检查。 结果：发现囊样变性、变性性视网膜劈裂症、销路石样变性，格子佯变性四种萎缩性视网膜变性．这些病变的病理表现与人类相应周边部视网膜变性具诸多相同特点。 结论：犬周边眼底存在与人类相似的萎缩性视网膜变性。 （中华眼底病杂志，1996，12：151-152）     

视网膜色素变性大鼠闪光视网膜电图及神经节细胞动作电位改变

皇家外科学院大矗土（RCS）为遗传性视网膜色素变性的经典动物模型，随着感光细胞的变性死亡，包括视网膜神经节细胞（RGC）在内的内层神经元电生理功能究竟发生了怎样的改变，至今知之甚少。RGC以动作电位（AP）的方式将来自于感光细胞的信息向上传递，视网膜变性过程中RGC电生理特性的变化尚未见报道。     

中药复方制剂对rds小鼠感光细胞凋亡的干预作用研究

目的观察中药复方制剂对先天性视网膜变性小鼠视网膜感光细胞凋亡的影响。方法以黄芪等药组成复方制剂1。对先天性视网膜变性动物模型rds小鼠,采用原位末端转移酶标记(TUNEL)方法及组织病理学技术,观察复方制剂1作用后,小鼠视网膜感光细胞数量及感光细胞凋亡的变化。结果仔鼠2周时,中药组小鼠视网膜感光细胞核数与对照组相比无明显差别,两组感光细胞凋亡率分别为1.6%及6.5%,组间差异有显著性(P<0.01);4周时中药组感光细胞核数目较对照组多,差异有显著统计学意义(P<0.01),两组感光细胞凋亡率分别为3.3%及8.5%,组间差异有显著统计学意义(P<0.01)。结论中药复方制剂1可以延缓rds小鼠视网膜色素变性过程中感光细胞凋亡的发展。     

视网膜色素变性固视性质与视功能关系的研究

许多眼底病变,当中心凹受累机能丧失时,会发生固视性质的改变,固视点的偏移。视网膜色素变性是以视网膜进行性变性伴有夜盲、视野缩小为特征的一种遗传性疾病,广泛损害感光细胞和色素上皮功能,当     

Retinal oxygenation and oxygen metabolism in Abyssinian cats with a hereditary retinal degeneration

PURPOSE: To investigate the effects of a hereditary retinal degeneration on retinal oxygenation and determine whether it is responsible for the severe attenuation of retinal circulation in hereditary photoreceptor degenerations. METHODS: Seven adult Abyssinian cats affected by hereditary retinal degeneration were studied. Oxygen microelectrodes were used to collect spatial profiles of retinal oxygenation in anesthetized animals. A one-dimensional model of oxygen diffusion was fitted to the data to quantify photoreceptor oxygen utilization (Qo(2)). RESULTS: Photoreceptor Qo(2) progressively decreased until it reached zero in the end stage of the disease. Average inner retinal oxygen tension remained within normal limits at all disease stages, despite the observed progressive retinal vessel attenuation. Light affected photoreceptors normally, decreasing Qo(2) by approximately 50% at all stages of the disease. CONCLUSIONS: Loss of photoreceptor metabolism allows choroidal oxygen to reach the inner retina, attenuating the retinal circulation in this animal model of retinitis pigmentosa (RP) and probably also in human RP. As the degeneration progresses, there is a strong relationship between changes in the a-wave of the ERG and changes in rod oxidative metabolism, indicating that these two functional measures change together.     

Ultrastructural study of primary canine and human pigmentary retinopathy

An electron microscopic study was performed on eyes of Labrador dogs afflicted with progressive retinal atrophy (PRA). There was complete loss of photoreceptors, atrophy of the remaining retina and gliosis in the peripheral part while the central retina showed incomplete loss of photoreceptors and an almost total disappearance of photoreceptor outer segments. Melanin-bearing cells, largely containing melanolysosomes, were found deep inside the retina.

This electron microscopic study also incorporated the retina of a middle-aged woman affected by retinopathia pigmentosa (RP). The fine structure of the diseased retina showed a similar pattern of lesions, more pronounced in the periphery of the retina. Similar electron microscopic findings between the two disease processes render PRA of the Labrador dog a useful model for a comparative study of the development and intraretinal spread of human RP.     

Retinal prostheses: current clinical results and future needs

Degenerative diseases such as age-related macular degeneration (AMD) and retinitis pigmentosa (RP) primarily affect the photoreceptors, ultimately resulting in significant loss of vision. Retinal prostheses aim to elicit neural activity in the remaining retinal cells by detecting and converting light into electrical stimuli that can then be delivered to the retina. The concept of visual prostheses has existed for more than 50 years and recent progress shows promise, yet much remains to be understood about how the visual system will respond to artificial input after years of blindness that necessitate this type of prosthesis. This review focuses on 3 major areas: the histopathologic features of human retina affected by AMD and RP, current results from clinical trials, and challenges to overcome for continued improvement of retinal prostheses. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosures may be found after the references.     

Morphologic changes in photoreceptor connecting cilia in experimental phototoxic retinopathy

PURPOSE: It has been suggested that structural alterations of the photoreceptor connecting cilium are a primary defects leading to photoreceptor degeneration in some forms of inherited retinal degenerations (5). In a series of 17 eyes with retinitis pigmentosa (RP) and with various genetic forms of RP, examined by electron microscopy, no structural abnormalities were found in the arrangement of the ciliary microtubules. However, a 10% reduction in the ciliary diameter was recorded in RP photoreceptors (12). The question arose: is thinning of the cilium a primary defect associated with RP, or a secondary abnormality related to degenerative processes in photoreceptors irrespective of the cause? The aim of this study was to examine the photoreceptor connecting cilia in the early stages of experimental light induced retinal degeneration in the rat, by conducting a structural and morphometric survey of the relevant electron-micrographs. In addition, the effects of various fixation techniques on the ciliary structure were compared. MATERIAL AND METHOD: Analysis of 124 transmission electron micrographs of 9 controls and 155 transmission electron micrographs of 55 light damaged animals was conducted. For the effects of fixation on morphometry 72 transmission electron micrographs from an additional 4 controls (43 negatives) and 8 light damaged animals (29 negatives) were examined. Light damage was induced by exposure to 1000 lux of white light for 120 minutes. Retinal samples were fixed either in 2.5% glutaraldehyde or by high pressure freezing followed by freeze-substitution. RESULTS: This study showed that one of the early morphological alterations occurring in rat photoreceptors damaged by light is a reduction of ciliary diameter of approximately 10%. It was not associated with any apparent ultrastructural changes in the axoneme. It was also found that the degree of ciliary shrinkage largely depends on the fixation technique used. Cryo-fixation followed by freeze substitution shows more shrinkage than chemical fixation by immersion in glutaraldehyde. CONCLUSIONS: It is suggested, that reduction in photoreceptor cilium diameter is a secondary and non-specific change. It is not a unique phenomenon, observed not only in human photoreceptors, which are undergoing degeneration in RP. It can be induced in otherwise healthy rat retina, in which photoreceptor degeneration was caused by exposure to toxic levels of light.     

Aberrant retinal tight junction and adherens junction protein expression in an animal model of autosomal dominant Retinitis pigmentosa: the Rho(-/-) mouse

Retinitis pigmentosa (RP) comprises a heterogeneous group of inherited diseases that are characterised by primary degeneration of rod photoreceptors and secondary degeneration of cone photoreceptors in the retina. Additional pathological changes include vascular changes and invasion of the inner retina by retinal pigment epithelial (RPE) cells. RP represents a major cause of progressive retinal disease worldwide. Using a mouse model of autosomal dominant Retinitis pigmentosa (adRP) with retinopathy induced by targeted disruption of the rhodopsin gene Rho(-/-), we have analysed the levels of expression of a range of tight and adherens junction associated proteins, in order to further elucidate the pathogenic mechanisms occurring at an early stage of this condition. Using western blot analysis and indirect immunostaining of retinal cryosections from 6-week-old mice from a C-129 background we have determined changes, if any, in the levels of expression and localisation of a series of tight and adherens junction associated proteins, including Zonula Occludens-1 (ZO-1), occludin, N-Cadherin, p120-Catenin, alpha-Catenin, gamma-Catenin, beta-Catenin, and E-Cadherin. We have found an up-regulation of the tight junction and adherens junction associated protein Zonula Occludens-1 (ZO-1) in the neural retina of 6-week-old Rho(-/-) knockout mice compared with 6-week-old Wild-Type (WT) mice. Following immunohistochemistry, however, it appears, that ZO-1, beta-Catenin and p120-Catenin expression at the Outer Limiting Membrane (OLM) of the Rho(-/-) retina is compromised, in part, compared to WT animals of the same age. We hypothesise that these retinal changes following photoreceptor cell death may contribute to the pathogenesis of adRP. Our findings of changes in the levels of expression of ZO-1 and associated adherens junction proteins beta-Catenin and p120-Catenin at the OLM in 6-week-old Rho(-/-) mice provide evidence for tight junction and adherens junction associated protein modifications in an animal model of autosomal dominant RP (adRP).     

Disease expression of RP1 mutations causing autosomal dominant retinitis pigmentosa

PURPOSE: To determine the disease expression in heterozygotes for mutations in the RP1 gene, a newly identified cause of autosomal dominant retinitis pigmentosa (adRP). METHODS: Screening strategies were used to detect disease-causing mutations in the RP1 gene, and detailed studies of phenotype were performed in a subset of the detected RP1 heterozygotes using electroretinography (ERG), psychophysics, and optical coherence tomography (OCT). RESULTS: Seventeen adRP families had heterozygous RP1 changes. Thirteen families had the Arg677ter mutation, whereas four others had one of the following: Pro658 (1-bp del), Ser747 (1-bp del), Leu762-763 (5-bp del), and Tyr1053 (1-bp del). In Arg677ter RP1 heterozygotes, there was regional retinal variation in disease, with the far peripheral inferonasal retina being most vulnerable; central and superior temporal retinal regions were better preserved. The earliest manifestation of disease was rod dysfunction, detectable as reduced rod ERG photoresponse maximum amplitude, even in heterozygotes with otherwise normal clinical, functional, and OCT cross-sectional retinal imaging results. At disease stages when cone abnormalities were present, there was greater rod than cone dysfunction. Patients with the RP1 frameshift mutations showed similarities in phenotype to those with the Arg677ter mutation. CONCLUSIONS: Earliest disease expression of RP1 gene mutations causing adRP involves primarily rod photoreceptors, and there is a gradient of vulnerability of retinopathy with more pronounced effects in the inferonasal peripheral retina. At other disease stages, cone function is also affected, and severe retina-wide degeneration can occur. The nonpenetrance or minimal disease expression in some Arg677ter mutation-positive heterozygotes suggests important roles for modifier genes or environmental factors in RP1-related disease.     

Retinopathy is reduced during experimental diabetes in a mouse model of outer retinal degeneration

PURPOSE: Diabetic patients who also have retinitis pigmentosa (RP) appear to have fewer and less severe retinal microvascular lesions. Diabetic retinopathy may be linked to increased inner retinal hypoxia, with the possibility that this is exacerbated by oxygen usage during the dark-adaptation response. Therefore, patients with RP with depleted rod photoreceptors may encounter proportionately less retinal hypoxia, and, when diabetes is also present, there may be fewer retinopathic lesions. This hypothesis was tested in rhodopsin knockout mice (Rho-/-) as an RP model in which the diabetic milieu is superimposed. The study was designed to investigate whether degeneration of the outer retina has any impact on hypoxia, to examine diabetes-related retinal gene expression responses, and to assess lesions of diabetic retinopathy. METHODS: Streptozotocin-induced diabetes was created in male C57Bl6 (wild-type; WT) and Rho-/- mice, and hyperglycemia was maintained for 5 months. The extent of diabetes was confirmed by measurement of glycated hemoglobin (%GHb) and accumulation of advanced glycation end products (AGEs). Retinal hypoxia was assessed using the bioreductive drug pimonidazole. The retinal microvasculature was studied in retinal flatmounts stained by the ADPase reaction, and the outer retina was evaluated histologically in paraffin-embedded sections. Retinal gene expression of VEGF-A, TNF-alpha, and mRNAs encoding basement membrane component proteins were quantified by real-time RT-PCR. RESULTS: The percentage GHb increased significantly in the presence of diabetes (P < 0.001) and was not different between WT or Rho-/- mice. Hypoxia increased in the retina of WT diabetic animals when compared with controls (P < 0.001) but this diabetes-induced change was absent in Rho-/- mice. Retinal gene expression of VEGF-A was significantly increased in WT mice with diabetes (P < 0.05), but was unchanged in Rho-/- mice. TNF-alpha gene expression significantly increased (4.9-fold) in WT mice with diabetes (P < 0.05) and also increased appreciably in Rho-/- mice but to a reduced extent (1.5 fold; P < 0.05). The outer nuclear layer in nondiabetic Rho-/- mice was reduced to a single layer after 6 months, but when diabetes was superimposed on this model, there was less degeneration of photoreceptors (P < 0.05). Vascular density was attenuated in diabetic WT mice compared with the nondiabetic control (P < 0.001); however, this diabetes-related disease was not observed in Rho-/- mice. CONCLUSIONS: Loss of the outer retina reduces the severity of diabetic retinopathy in a murine model. Oxygen usage by the photoreceptors during dark adaptation may contribute to retinal hypoxia and exacerbate the progression of diabetic retinopathy.     

Metabolic Studies on Retinal Tissue from a Donor with a Dominantly Inherited Chorioretinal Degeneratlon Resembling Sectoral Retinitis Pigmentosa

Protein synthesis, glycosylation, RNA synthesis, and neurotransmitter uptake were monitored using biochemical and autoradiographic techniques following in vitro labeling of retinal tissue from a 79-year-old female with sectoral retinitis pigmentosa (RP). Comparisons were made between degenerate and non-degenerate regions of the RP retina, and normal retinal tissues from an age- and postmortem-matched donor. Autoradiographs of non-degenerate retina from the RP eye following ³>H-uridine incubation revealed virtually identical silver grain density over nuclei in all retinal strata as compared to normal control retinas. In contrast, a photoreceptor-specific reduction in silver grain density in the non-degenerate RP retina was noted following ³H-leucine incubation. In the normal retina, rod photoreceptor labeling with ³H-mannose was always greater than cone photoreceptor labeling. This pattern of incorporation was reversed in the non-degenerate region of the RP retina where rod photoreceptor labeling was less pronounced than that observed for cone photoreceptors.In non-degenerate regions of the RP retina, a marked accumulation of ³H-GABA by the M?ller's cells was observed. Few cells exhibited selective uptake of³>H-muscimol, a GABA analog, indicating that few GABAergic neurons remained in the degenerate retina. ³H-dopamine-accumulating cell terminals were observed in the usual positions in the non-degenerate RP retina. In the degenerate region of the RP retina, heavy and diffuse uptake of ³H-GABA and³>H-muscimol, respectively, into broad cellular processes were noted, whereas³>H-dopamine was accumulated by only a few punctate terminals.