视网膜色素上皮紧密连接及血-视网膜外屏障功能

视网膜色素上皮细胞间的紧密连接( tight junctions,TJs)构成血-视网膜外屏障,对调节视网膜的微环境起重要作用。本文就TJs的分子结构、血-视网膜外屏障的功能、体外模型的构建与评估、相关眼病及细胞移植后屏障重建等问题加以综述。     

血-视网膜屏障损伤的机制及治疗对策

血-视网膜屏障在维持视网膜微环境稳态中具有重要作用,很多疾病如糖尿病视网膜病变、急性青光眼、早产儿视网膜病变等均会导致血-视网膜屏障损伤。目前对于引起血-视网膜屏障损伤的分子机制尚未完全阐释清楚,本文旨在综述血-视网膜屏障的结构与功能,各种眼部疾病导致的血-视网膜屏障损伤机制及采用药物治疗、激光治疗、手术治疗的治疗对策。     

细胞因子与血-视网膜屏障损害

血 -视网膜屏障 (BRB)存在于血液和视网膜之间具有限制性通透性的结构 ,拥有精细的解剖基础和特殊的通透性特点。视网膜正常功能的保持有赖于此屏障的存在。BRB功能障碍几乎和所有的视网膜脉络膜疾病关系密切 ,尤其是血管性视网膜病变和色素上皮病变。对于BRB功能障碍发生机理的研究具有非常重要的临床意义。近年来随着细胞因子研究的不断深入 ,发现BRB功能障碍与细胞因子有很大关系 ,许多学者在此方面作了许多深入细致的工作。本文对这方面的研究进行综述。一、血 -视网膜屏障的结构基础BRB由两部分组成 ,视网膜血管内皮细胞及其连接…     

血—视网膜屏障损伤中的细胞因子及信息分子

血－视网膜屏障（BRB）是一种重要的血－眼屏障，在视网膜代谢中起重要作用。它的损伤（尤其内屏障）导致的黄斑水肿严重影响视功能，但诱发其发生的分子生物学机制尚不清楚。本就近年来对BRB损伤的影响因素、调节因素等方面的研究进行综述。     

血-视网膜屏障损伤中的细胞因子及信息分子

血-视网膜屏障 (BRB)是一种重要的血 眼屏障 ,在视网膜代谢中起重要作用。它的损伤 (尤其内屏障 )导致的黄斑水肿严重影响视功能 ,但诱发其发生的分子生物学机制尚不清楚。本文就近年来对BRB损伤的影响因素、调节因素等方面的研究进行综述。     

眼血管的渗透性和穿越血-视网膜屏障的运转

复习了对视网膜与脉络膜血管渗透性的定量研究和营养物质超越血-视网膜屏障的交换。脉络膜内多孔状的毛细血管使低分子量物质很易渗透,钠的渗透性约为骨髂肌的50倍,因而脉络膜血管外间隙内的营养物质浓度高、周转快。但这种自由弥散受脉络膜上皮屏障和视网膜毛细血管的制约,其内皮细胞间有紧密连接,即使是对钠,渗透性也很低。吸收指数技术为血-视网膜屏障的数种载体系统提供了证据,己糖类、中性和碱性氨基酸类,以及单羧酸类,都与脑内所见极为相似。至少对葡萄糖和乳酸化物等载体,在血-视网膜屏障、视网膜色素上皮和视网膜毛细血管内皮的两侧均起作用,具有向内和向外的双向性。     

血-视网膜外屏障发育的研究现状

血-视网膜外屏障(BRB)由视网膜色素上皮(RPE)细胞间的连续网状紧密连接构成,是维持视网膜及视觉生理状态的重要基础.BRB由视神经管的膨出部分视泡发育而来,随着胚胎发育逐渐形成.发育过程中紧密连接复合体的结构及分子组成均发生了改变,且受周围组织的调控.BRB的发育具有种属差异.干细胞来源的RPE细胞有可能成为研究RPE屏障功能的最佳模型.     

糖尿病性视网膜病变中血视网膜屏障损伤机制研究进展

血视网膜屏障损伤是糖尿病视网膜病变多种临床表现的病理基础,近年对血视网膜屏障损伤的机制研究包括糖代谢异常、细胞因子及视网膜血管旁神经胶质细胞等方面,本文对此作一综述.     

糖尿病大鼠血视网膜屏障损伤观察

血视网膜屏障破坏以及血管通透性增高是糖尿病视网膜微血管病变的主要病理学基础。我们以链脲佐菌素诱导的糖尿病大鼠为研究对象，观察了非增生期及临床前期糖尿病视网膜病变在发生临床可见的视网膜微血管病变前，血视网膜屏障是否已发生改变，随着病变进展其损害如何进一步加重以及此屏障功能损害与其形态结构改变的关系，现将结果报道如下。     

血-视网膜屏障及其临床意义

血-视网膜屏障(BRB)与视网膜病变有重要关系。此屏障使神经视网膜与血液、视网膜组织液与脉络膜组织液相分离,避免血液中某些有害成分如免疫复合物、淋巴毒素等对视网膜的侵害。它不仅具有选择通透性,还能通过主动运输排除视网膜组织中的代谢产物。缺氧、渗透压改变及某些化学物质能影响屏障的结构和功能。玻璃体荧光光度测定法能早期、定量地评价屏障的改变;磁共振成像技术则能在三维水平上较准确地显示屏障的状态。糖尿病性视网膜病变、视网膜脱离、眼外伤、视网膜色素变性、视网膜静脉阻塞等均伴有BRB的改变。     

Localised blood-retinal barrier leakage and retinal light sensitivity in diabetic retinopathy.

Twenty patients with insulin dependent diabetes mellitus were selected on the basis of morphological signs of blood-retinal barrier leakage--namely, hard exudates seen on fundus photographs and/or localised leakage of fluorescein seen on fluorescein angiograms. Computerised perimetry was carried out in visual field areas that corresponded to the morphological lesions, and the visual field data were accurately correlated with the morphology as seen on fundus photographs and fluorescein angiograms. In addition, in seven of the patients who represented the range of leakage among the patients studied, the blood-retinal barrier leakage was quantitated by vitreous fluorophotometry. In 16 cases normal light sensitivity was found in retinal areas showing localised leakage as studied on fluorescein angiograms. In four cases with pronounced maculopathy, where scotomata occurred, there was no topographical correlation between the scotomata and barrier leakage. Furthermore hard exudates often, but not consistently, caused localised scotomata when arranged in dense conglomerates. The permeability values correlated with angiographically observed hyperfluorescence in the macular area. On the basis of the techniques employed in the present study it seems that breakdown of the blood-retinal barrier is an earlier event than disturbance of neurosensory function in the development of diabetic retinopathy. However, the findings give no evidence of a causal relationship between barrier leakage and damage to sensory cell function.     

Effect of cyclospasmol on early diabetic retinopathy

A randomized, double-blind, placebo controlled study to investigate the long-term effect of Cyclospasmol^R (cyclandelate) on the abnormal permeability of the blood-retinal barrier was performed in 26 patients with insulin-dependent diabetes mellitus for at least 1 year and minimal retinopathy. Cyclospasmol 400 mg or placebo capsules were taken 4 times daily for 12 months by equal numbers in both groups.Each patient underwent a routine ophthalmoscopic examination, retinal fluorescein angiography and quantitative vitreous fluorophotometry to assess the permeability of the blood-retinal barrier just before the trial and following 6 and 12 months of therapy. Laboratory tests for determining blood and urine glucose levels and blood HbA₁-levels were also carried out at these assessments.Statistically significant changes in diabetic control, in HbA₁-levels or in the frequency of retinal microaneurysms could not be shown in either treatment group during the trial, nor were there any significant differences in these parameters between the two groups. Analysis of fluorophotometric data on fluorescein penetration into the left posterior vitreous demonstrated significant reductions in this parameter during the trial compared to the pretreatment level in Cyclospasmol treated diabetics. These changes in the pretreatment level after 6 and 12 months also differed significantly between the two groups.However, this statistically significant beneficial reduction in fluorescein penetration into the left posterior vitreous did not occur in the right eye in the Cyclospasmol group.In placebo treated patients a consistently deleterious trend for this parameter was observed for both eyes during the one year study. The consistently beneficial trend in the right eye following Cyclospasmol and the consistently deleterious trend in both eyes following placebo with regard to the abnormal permeability of the blood-retinal barrier of diabetics with minimal retinopathy could probably be explained by the small number of patients in both groups. No side-effects were reported.     

视网膜色素上皮细胞的功能及其抗新生血管作用

视网膜色素上皮（ retinal pigment epithelial,RPE）由一单层排列整齐的六角形细胞所组成,位于视网膜光感受器细胞层和脉络膜的Bruch's膜之间,其形态及功能的正常维持对于光感受器细胞至关重要,具有维持选择性转运营养和代谢物质、表达分泌多种生长因子、参与视循环、维持血－视网膜屏障和吞噬光感受器细胞脱落的外节盘膜等重要生理功能。 RPE细胞所构成的血－视网膜外屏障对于视网膜稳态的维持必不可少,其功能异常与许多眼底新生血管性疾病密切相关。本文对RPE正常结构、分泌生长因子、血－视网膜屏障功能、抗新生血管等方面进行综述。     

Breakdown of the outer blood-retinal barrier in experimental commotio retinae

An animal model has been developed in this study to produce commotio retinae (Berlin's edema) by means of standardized, non-penetrating B.B. pistol injury to the cornea. Parameters have been established to ensure uniform blunt injury, enabling study of the retina and blood-retinal barrier by light- and electron microscopy, including use of horseradish peroxidase as a vascular tracer. Retinal whitening and swelling were found in the peripapillary and central regions, as occurs in the human. The earliest damage involved breakage of the connecting cilia of rods and cones, with rapid disorganization of the outer segments. Later changes included swelling of photoreceptor inner segments and breakdown of the outer blood-retinal barrier at the level of the retinal pigment epithelium. The outer blood-retinal barrier was re-established between 7 and 14 days, and at the longest survival (56 days), incompletely regenerated outer segments were present. This model for commotio retinae provides a new approach for the study of outer-segment regeneration in rods and cones after mechanical injury, as well as mechanisms that underlie re-establishment of the blood-retinal barrier following non-penetrating trauma to the eye.     

Intrachoroidal dye leakage in indocyanine green fundus angiography after experimental commotio retinae.

Dye leakage in sodium fluorescein (FLUO) fundus angiography indicates damage to the blood-retinal barrier. However, dye leakage in indocyanine green (ICG) fundus angiography does not mean the same, because of the larger molecular size of the dye and impermeability of the choroidal vessels to it. The possibility of dye leakage in ICG angiography has not yet been revealed in an experimental study in which the blood-retinal barrier is undamaged. We report here that intrachoroidal dye leakage may occur in ICG angiography in an experimental model of the traumatic retinal opacity of the rabbit eye, even when the blood-retinal barrier is undamaged. This mechanism of dye leakage in ICG angiography is quite different from the leakage of FLUO angiography. Pathological choroidal vessels with increased permeability, such as choroidal neovascularization under the retinal pigment epithelium, can be observed using ICG angiography.     

Early breakdown of the blood-retinal barrier in diabetes.

The blood-retinal barrier plays an important part in the processes of retinal pathophysiology. A new clinical method for the study of the blood-retinal barrier by vitreous fluorophotometry appears to satisfy the necessary requirements in that it is quantitative and shows good reproducibility and high sensitivity. The application of this method to a series of diabetic patients with apparently "normal" fundi revealed the presence of a significant breakdown of the blood-retinal barrier in the early stages of retinal involvement in diabetes. The extent of the breakdown can be measured allowing for comparative and evolutionary evaluations. The disturbance of the blood-retinal barrier, as evidence by vitreous fluorophotometry, appears before microaneurysms or capillary closure can be demonstrated by fluorescein angiography.     

The blood-ocular barriers: past, present, and future

The blood-ocular barriers system is formed by two main barriers: the blood-aqueous barrier and the blood-retinal barrier. They combine to maintain the eye as a privileged site and are essential for normal visual function. After reviewing where the blood-aqueous barrier and blood-retinal barrier are located and the main transport mechanisms involved in the regulation of the microenvironment of ocular tissues, special attention is given to the clinical significance of breakdown of the blood-retinal barrier. New perspectives on the clinical significance of breakdown of the blood-retinal barrier are offered by the demonstration of a specific alteration of the glucose transport in diabetes, by the development of new diagnostic instrumentation, and by the utilization of the blood-retinal barrier for new strategies for drug delivery to the retina. New diagnostic instrumentation includes the topographic imaging vitreous fluorometer, which simultaneously measures the localized blood-retinal barrier and images the retinal region, and the retinal thickness analyzer for mapping retinal edema. Drug delivery to the retina may be improved by modification of blood-retinal barrier permeability, chemical modification of the drug for better blood-retinal barrier penetration, and liposome encapsulation or coupling of the drug to specific vectors. Read at the October 27, 1966 meeting of the Academia Ophthalmogica Internationalis, in Chicago, Illinois.     

Interactions of the choroid,Bruch's membrane,retinal pigment epithelium,and neurosensory retina collaborate to form the outer blood-retinal-barrier

The three interacting components of the outer blood-retinal barrier are the retinal pigment epithelium (RPE), choriocapillaris, and Bruch's membrane, the extracellular matrix that lies between them. Although previously reviewed independently, this review integrates these components into a more wholistic view of the barrier and discusses reconstitution models to explore the interactions among them. After updating our understanding of each component's contribution to barrier function, we discuss recent efforts to examine how the components interact. Recent studies demonstrate that claudin-19 regulates multiple aspects of RPE's barrier function and identifies a barrier function whereby mutations of claudin-19 affect retinal development. Co-culture approaches to reconstitute components of the outer blood-retinal barrier are beginning to reveal two-way interactions between the RPE and choriocapillaris. These interactions affect barrier function and the composition of the intervening Bruch's membrane. Normal or disease models of Bruch's membrane, reconstituted with healthy or diseased RPE, demonstrate adverse effects of diseased matrix on RPE metabolism. A stumbling block for reconstitution studies is the substrates typically used to culture cells are inadequate substitutes for Bruch's membrane. Together with human stem cells, the alternative substrates that have been designed offer an opportunity to engineer second-generation culture models of the outer blood-retinal barrier.     

VEGF-initiated blood-retinal barrier breakdown in early diabetes

PURPOSE: The objectives of this study were to (1) determine whether endogenous vascular endothelial growth factor (VEGF) triggers diabetic blood-retinal barrier breakdown, and (2) identify the site as well as phenotype of the hyperpermeable diabetic retinal vessels. METHODS: Retinal VEGF mRNA levels were quantified in 1-week diabetic rats using the RNase protection assay. VEGF bioactivity was blocked via the systemic administration of a highly specific VEGF-neutralizing soluble Flt/F(c) construct (VEGF TrapA(40)). An inactive IL6 receptor/F(c) construct (IL6R Trap) was used as an isotype control. Blood-retinal barrier breakdown was quantified using the Evans blue technique and was spatially localized with fluorescent microspheres. RESULTS: Retinal VEGF mRNA levels in 1-week diabetic animals were 3.2-fold higher than in nondiabetic controls (P < 0.0001). Similarly, retinal vascular permeability in 8-day diabetic animals was 1.8-fold higher than in normal nondiabetic controls (P < 0.05). Diabetes-induced blood-retinal barrier breakdown was dose-dependently inhibited with VEGF TrapA(40), with 25 mg/kg producing complete inhibition of the diabetes-induced increases (P < 0.05). Blood-retinal barrier breakdown in diabetic animals treated with solvent alone or IL6R Trap did not differ significantly from untreated diabetic animals (P > 0.05). Spatially, early blood-retinal barrier breakdown was localized to the retinal venules and capillaries of the superficial retinal vasculature. CONCLUSIONS: Early blood-retinal barrier breakdown in experimental diabetes is VEGF dependent and is restricted, in part, to the venules and capillaries of the superficial inner retinal vasculature. VEGF inhibition should prove a useful therapeutic approach in the treatment of early diabetic blood-retinal barrier breakdown.     

人角膜内皮细胞的体外培养及其鉴定的研究进展

角膜内皮细胞对维持角膜的透明性和厚度起着关键性的作用。人体内角膜内皮细胞有限的增殖能力及角膜供体的短缺,使组织工程人角膜内皮的体外重建受到了关注。目前,人角膜内皮细胞的培养方法已基本成熟。但是体外培养的人角膜内皮细胞的功能评价及鉴定标准却尚未建立。本文就人角膜内皮细胞的体外培养及其鉴定的研究进展进行综述。