视网膜下液致视网膜色素上皮细胞增殖过程中蛋白激酶C活性的变化

目的 探讨视网膜下液（SRF）能否引起体外培养的视网膜色素上皮（RPE）细胞增殖及在其增殖过程中是否出现蛋白激酶C（PKC）的激活和转位,进一步明确RPE细胞增殖与RPE细胞中PKC信号系统变化的关系及PKC抑制剂的作用。方法 实验对象为体外培养的RPE细胞;刺激因素为提取的增生性玻璃体视网膜病变（PVR）为B、C级患者的SRF和来自角膜移植后的供体眼球所提供的正常玻璃体成分;PKC特异激活剂佛波酯（PMA）为阳性对照;DMEM培养液作为空白对照。用^3H-胸腺嘧啶脱氧核苷（^3H-TdR）掺入法测定各自的RPE细胞增殖情况。用B、C级SRF、正常玻璃体成分、PMA、DMEM培养液分别在不同的时间刺激RPE细胞,通过细胞裂解和离心获取细胞质和细胞膜蛋白粗提液,用同位素^32P标记和液体闪烁计数法检测细胞质和细胞膜PKC活性水平。选用PKC特异抑制剂N,N-二甲基鞘氨醇预处理各组细胞后,再分别观察各组RPE细胞中PKC活性表达水平及增殖情况。结果 用B、C级SRF和PMA处理过的RPE细胞出现高增殖;SRF和PMA都可以激活RPE细胞质中的PKC,并使其由胞质向胞膜转位,但SRF作用于RPE细胞时,胞膜上PKC活性峰值出现的时问较PMA明显延长。其中,B级SRF作用于RPE细胞时,胞膜上PKC活性峰值出现的时间较C级长且峰值低,增殖程度也低;正常玻璃体成分和DMEM培养液组未出现PKC活性变化和高增殖。用PKC特异抑制剂预处理各组细胞后,未出现PKC活性和细胞增殖的改变,组间比较差异无统计学意义（P〉0．05）。结论 SRF可促进RPE细胞增殖,RPE细胞中的PKC是以激活和转位方式参与细胞增殖的过程;使用PKC特异抑制剂可阻止此过程发生。（中华眼科杂志,2006,42：738-743）     

Persistent subretinal indocyanine green induces retinal pigment epithelium atrophy

PURPOSE: To describe a case of a patient with macular hole with subretinal indocyanine green (ICG) during vitrectomy. DESIGN: Interventional case report. METHODS: A 66-year-old woman with macular hole underwent a vitrectomy with ICG. RESULTS: After application of ICG into the vitreous, ICG was introduced in the subretinal space. Indocyanine green was found to be present for more than 6 months. Retinal pigment epithelium atrophy appeared at the site of the lesion. CONCLUSIONS: Although ICG may be a useful tool for distinguishing the internal limiting membrane and other tissues careful application is required to prevent side effects.     

视网膜下液致视网膜色素上皮细胞和神经胶质细胞增殖过程中PKC活性的变化

目的:研究视网膜下液(SRF)能否引起体外培养的人视网膜色素上皮(RPE)和神经胶质(RG)细胞发生增殖及在其增殖过程中是否出现蛋白激酶 C 的激活和转位, 来探讨RPE 和 RG 细胞增殖与其细胞中 PKC 信号系统变化的关系以及 PKC 抑制剂的作用。方法:实验对象为体外培养的 RPE 和 RG 细胞;刺激因素为提取 PVR 分级是 B、C 级两级患者的 SRF 和来自角膜移植后的供体眼球所提供的正常玻璃体成分;PKC 特异激活剂佛波酯(PMA)为阳性对照;DMEM 培养液作为空白对照。用 3H- 胸腺嘧啶脱氧核苷(3H- TdR)掺入法测定各自的RPE 和 RG 细胞增殖情况。用 B、C 级 SRF、正常玻璃体成分、PMA、DMEM 培养液分别在不同的时间刺激 RPE 和 RG细胞, 通过细胞裂解和离心获取细胞质和细胞膜蛋白粗提液,用同位素 32P 标记和液体闪烁计数法检测细胞质和细胞膜 PKC 活性水平。选用 PKC 抑制剂地喹氯铵预处理各组细胞后,再分别观察各组 RPE 和 RG 细胞中 PKC 活性表达水平及增殖情况。结果:用 B、C 级 SRF 和 PMA 处理过的 RPE 细胞出现高增殖;SRF 和 PMA 都可以激活 RPE 和 RG 细胞质中的 PKC,并使其由胞质向胞膜转位,但 SRF 作用于 RPE 和 RG 细胞时,胞膜上 PKC 活性峰值出现的时间较 PMA 明显延长。其中,B 级 SRF 作用于 RPE 和 RG 细胞时,胞膜上 PKC 活性峰值出现的时间较 C 级长且峰值低,增殖程度也低;正常玻璃体成分和 DMEM 培养液组没有出现 PKC 活性变化和高增殖。用 PKC 特异抑制剂预处理各组细胞后,没有出现PKC 活性和细胞增殖的改变,组间无显著性差异,P>0.05。结论:SRF 可促进 RPE 和 RG 细胞增殖,RPE 和 RG 细胞中的 PKC 是以激活和转位方式参与细胞增殖的过程;使用PKC 特异抑制剂可阻止此过程发生。     

Culture of retinal pigment epithelial cells from subretinal fluid

Culture of cells from subretinal fluid (SRF) was performed using 29 SRF samples obtained at retinal reattachment surgery. Proliferating cells were found in 58.6% of the samples studied. The cells were of retinal pigment epithelial (RPE) origin, as evidenced by their brown pigmentation in primary culture and their positive immunostaining for cytokeratins 8/18. The age of the patients did not affect the proliferative capacity of the cells. Proliferating cells were present in all samples from eyes with proliferative vitreoretinopathy (PVR) of grade C1 or more. In primary culture the cells had a fibroblast-like morphology, resembling that of ordinary RPE cells exposed to the vitreous. We conclude that the SRF of many patients with PVR contains viable proliferating RPE cells and that SRF offers a new source of RPE cells for studies on the pathogenesis of PVR.     

培养人视网膜色素上皮细胞在PVR患者视网膜下液作用下c-fos和c-jun的表达

目的 观察培养的人视网膜色素上皮细胞(human retinal pigment epithelium，hRPE)在不同程度增生性玻璃体视网膜病变(proliferative vitreoretinopathy，PVR)患者视网膜下液(subretinal fluid，SRF)作用下细胞增生与c—fos和c—jun的表达。方法 不同程度PVR患者SRF作用于培养的hRPE细胞后利用细胞计数和MTT比色实验观察SRF对培养hRPE细胞的作用，同时采用SP法在不同时间点作兔抗人c—fos多抗和兔抗人c—jun多抗的免疫组织化学染色。结果 PVR患者SRF作用组与对照组相比可明显促进培养hRPE细胞的增殖，同时实验组hRPE细胞c—fos和c—jun均表达增高，视网膜下液作用lh后，Fos蛋白抗体染色阳性，细胞核呈明显棕黄色染色；3h表达达高峰，持续约12h；视网膜下液作用lh后，Jun蛋白抗体染色阳性，细胞核呈明显棕黄色染色；6h表达达高峰，持续约48h，对照组hRPE细胞(未经SRF作用仅加入等量PBS)Fos蛋白抗体和Jun蛋白抗体染色均为阴性。结论 PVR患者SRF中含有能诱导c—fos和c—jun等“立早基因”转录的细胞外生长或分化因子；c—fos和c—jun的表达是SRF促进RPE细胞的增殖过程中一个非常重要的早期分子事件。     

The role of retinal pigment epithelium in the involution of subretinal neovascularization

The extravascular milieu around laser-induced experimental subretinal neovascularization (SRN) was studied during the evolution of the neovascular membrane from its early leaky stage to its late involuted stage. When the first signs of visible leakage appeared on angiography, newly formed vessels were spread in the subretinal space around the break in Bruch's membrane, fluid was accumulating in the subretinal space, and retinal pigment epithelial (RPE) cells were proliferating in a papillary pattern around the newly formed vessels; the RPE proliferation began with the undamaged cells at the edges of the laser injury. With further maturation, the RPE continued to envelope the subretinal vessels. This RPE proliferation was associated with the disappearance of fluid between the enveloped vessels and the sensory retina, and the gradual cessation of fluorescein leakage during angiography. At the end of the involution process, when the neovascular membrane no longer demonstrated any leakage, the subretinal vessels were found to be tightly enveloped by RPE cells, and no fluid separated them from the sensory retina. The authors' results suggest that involution of the neovascular membrane with maturation, as demonstrated by the cessation of visible fluorescein leakage, is the result of RPE proliferation that tightly envelopes the newly formed vessels and probably resorbs the previously accumulated subretinal fluid, as well as preventing its further accumulation in the subretinal space.     

Distribution of ascorbate in the retina, subretinal fluid and pigment epithelium

The posterior segment of the eye was divided into four compartments: retinal cytosol (R), subretinal fluid on the retinal surface (S/R), retinal pigment epithelial (RPE) cytosol, and subretinal fluid on the RPE surface (S/RPE). The volume of each compartment was estimated from the dilution of creatinine (in the extraction buffer) by the endogenous tissue fluid. The ascorbate concentrations in R, S/R, S/RPE, and RPE were 20.6, 12.3, 3.7, and 5.8 mg/dl respectively. Dehydroascorbate was observed only in the RPE and S/RPE. The decreasing ascorbate concentration from the retina to RPE, and the distribution of dehydroascorbate suggest a movement of ascorbate from the vitreous cavity into the subretinal space. The permeability of retinal cell layers to ascorbate was confirmed by the high radioactivity observed in the subretinal space after an intravitreal injection of C14-ascorbate. The occurrence of dehydroascorbate in the RPE and the S/RPE indicates the presence of oxidative reaction of ascorbate in these compartments, where light induced free radicals are located.     

Functional and morphological analysis of the subretinal injection of retinal pigment epithelium cells

Replacement of retinal pigment epithelium (RPE) cells by transplantation is a potential treatment for some retinal degenerations. Here, we used a combination of invasive and noninvasive methods to characterize the structural and functional consequences of subretinal injection of RPE cells. Pigmented cells from primary cultures were injected into albino mice. Recovery was monitored over 8 weeks by fundus imaging, spectral domain optical coherence tomography (sdOCT), histology, and electroretinography (ERG). sdOCT showed that retinal reattachment was nearly complete by 1 week. ERG response amplitudes were reduced after injection, with cone-mediated function then recovering better than rod function. Photoreceptor cell loss was evident by sdOCT and histology, near the site of injection, and is likely to have been the main cause of incomplete recovery. With microscopy, injected cells were identified by the presence of apical melanosomes. They either established contact with Bruch's membrane, and thus became part of the RPE monolayer, or were located on the apical surface of the host's cells, resulting in apposition of the basal surface of the injected cell with the apical surface of the host cell and the formation of a series of desmosomal junctions. RPE cell density was not increased, indicating that the incorporation of an injected cell into the RPE monolayer was concomitant with the loss of a host cell. The transplanted and remaining host cells contained large vacuoles of ingested debris as well as lipofuscin-like granules, suggesting that they had scavenged the excess injected and host cells, and were stressed by the high digestive load. Therefore, although significant functional and structural recovery was observed, the consequences of this digestive stress may be a concern for longer-term health, especially where RPE cell transplantation is used to treat diseases that include lipofuscin accumulation as part of their pathology.     

A role of the retinal pigment epithelium in the involution of subretinal neovascularization]

We clarified a role of the retinal pigment epithelium (RPE) in the regression of experimentally induced subretinal neovascularization (SRN) in monkey. Eight eyes of 5 rhesus monkeys were used in this study. Two weeks after intense krypton laser photocoagulation to the posterior pole of the fundus, 0.5M l-ornithine hydrochloride solution 0.03 ml was injected intravitreously for the purpose of selective RPE damage. After ornithine injection, SRN continued without any evidence of spontaneous regression over 8 weeks following photocoagulation. Histopathologically, SRN developed with wide lumen in the subretinal space accompanied with serous detachment of the sensory retina, and new vessels were not enveloped completely by the proliferating RPE cells. We already showed that experimentally induced subretinal neovascularizations naturally regress spontaneously by envelopment of RPE cells 5 to 8 weeks after photocoagulation. Our results suggested that SRN persist actively without regression due to incomplete enclosure by RPE by selective damage of RPE at the active stage of SRN. We have confirmed that the RPE cells played an important role at the involution stage of SRN.     

移植的人胚眼色素上皮在猴眼视网膜下腔中的自然转归

观察猴视网膜下腔植入人胚眼视风膜色素上皮后不同时段的眼底,荧光血管造影和组织学的改变。方法１２－２４周的人胚眼色素上皮片和酶解后的浓缩色素上皮细胞悬液经一步法或二步法植入猴眼视网膜下腔。结果猴眼发生排异反应的时间为２－６月,猴眼黄斑区发生排异反应的比例高于黄斑周围区。结论异种ＲＰＥ视网膜下腔的移植在无无免疫抑制剂的条件下,只能短期存活。     

A model for transepithelial ion transport across the isolated retinal pigment epithelium of the frog

The contribution of chloride ion movement and sodium and bicarbonate concentrations to the net current across the isolated choroid-retinal pigment epithelium (RPE) of the bullfrog were studied. The presence of a ouabain-sensitive Na+/K+-pump on the retinal side was confirmed and complete inhibition of this pump with Na+ removal and ouabain treatment abolished nearly all the RPE transepithelial transport and SCC suggesting that all ionic transport was dependent on sodium. It was found that apical to basal (AB) chloride flux accounted for 26 +/- 2% (mean +/- S.E.M.) of the short circuit (SCC). Results suggest that AB bicarbonate and/or basal to apical (BA) hydrogen ion net transport accounts for 38 +/- 2% of the SCC while BA sodium is presumably responsible for the remaining 34% of the SCC. Transport was inhibited by apical administration of known chloride inhibitors. Trans-RPE 36Cl flux measurements indicate that furosemide (10(-4) M) and SITS (10(-3) ) decrease the retinal-choroid flux. Results suggest that net transport of chloride and bicarbonate are independent of each other and additive. It was found that a bicarbonate-free preparation was relatively unaffected by changes in pH (5.5-8.5) indicating that pH has little, if any, effect on sodium or chloride current in this range. A model is presented which is compatible with the various data. It is suggested that along with the apical Na+/K+-ATPase pump, there exists an apical Na+/Cl- -co-transport system which is driven by the established sodium gradient. Moreover, this pump established sodium gradient is postulated to drive a Na+/HCO3- -co-transport system tentatively placed on the retinal side of the RPE.     

The role of retinal pigment epithelium in the early stage of development of subretinal neovascularization

In order to evaluate the role of retinal pigment epithelium (RPE) in the early stage of experimental subretinal neovascularization, we severely damaged RPE cells before the development of subretinal neovascularization. Three adult rhesus monkeys were used in this study. One mol/l l-ornithine hydrochloride saline solution was injected intravitreously at 2 weeks before intense krypton laser photocoagulation on the retina at the posterior pole, and clinical and histopathological course were studied at 1 to 28 days after photocoagulation. As a result, no evidence of new vessel formation could be observed clinically throughout the entire course. Histopathologically, at 3 days after photocoagulation, slight proliferation of RPE cells was identified by electron microscopy at the margin of the laser lesions, and budding of vascular endothelial cells derived from choroidal microvessels was observed in the choroid. However, no newly-formed vessels extended into the subretinal space at 7 days or more after photocoagulation. These results confirmed our hypothesis that proliferated RPE cells had inductive effect on the growth of endothelial cells in the early stage of development of subretinal neovascularization.     

Aquaporin-1 channels in human retinal pigment epithelium: role in transepithelial water movement

PURPOSE: Aquaporin (AQP) is a hexahelical integral membrane protein that functions as a constitutive channel for water and regulated channel for cations in fluid transporting tissues, including many in the eye. Although AQP1 has been cloned from a cDNA library prepared from cultures of retinal pigment epithelial (RPE) cells isolated from human fetal tissue, three separate studies failed with various immunochemical techniques to detect AQP1 protein in adult human or rat RPE preparations. The purpose of this study was to examine specifically the expression and distribution of AQP1 in adult human RPE in situ by using alternative methodologies and model systems and to determine the contribution of AQP1 to water movement across cultured RPE cells isolated from human cadaveric and fetal eyes. METHODS: AQP1 in human RPE in situ was determined after biotinylation of proteins on cell surfaces and streptavidin chromatography, followed by immunoblot analyses. AQP1 distribution in a polarized in vitro RPE model was determined with indirect immunofluorescence confocal microscopy. The role of channel-mediated transport of water across RPE cell monolayers on filters was assessed by osmotic challenge assay. Expression levels of AQP1 were controlled with an adenovirus expression system and monitored by immunoblot analyses. RESULTS: AQP1 protein was detected in human RPE in situ and in cultures of human adult and fetal RPE cells. In functional assays, AQP1 facilitated water movement across RPE monolayers in an expression-dependent manner in two complementary model systems. CONCLUSION: The expression of AQP1 by RPE in vivo probably contributes to the efficient transepithelial water transport across RPE, maintains retinal attachment, and prevents subretinal edema.