Endothelin-1 and ETA/ETB receptor protein and mRNA: expression in normal and vascularized human corneas

PURPOSE: Neovascularization of the cornea causes blindness and increases the risk of immune rejections after keratoplasty. The purpose of this study was to investigate involvement of the potent angiogenic growth factor endothelin (ET)-1 and its receptors, ETA and ETB, in corneal neovascularization. METHODS: ET-1, ETA, and ETB receptor protein expression was evaluated in nonvascularized and vascularized human corneas by immunohistochemistry. Epithelial ET-1 protein expression of both groups was compared using a semiquantitative scoring system. Double immunofluorescence was used to colocalize ETA and ETB receptor with CD31. In situ hybridization and immunoelectron microscopy analyzed ET-1 and its receptors in normal and vascularized corneas. RESULTS: Nonvascularized corneas displayed ET-1 and ETA/ETB receptor protein and mRNA in epithelial and some corneal endothelial cells. ETA more than ETB receptors were expressed on some keratocytes. In vascularized corneas, ET-1 and ETA/ETB receptor expression was found in the endothelial lining of new blood vessels (as shown by CD31-colocalization). ET-1 protein expression was significantly increased in the epithelium of vascularized corneas (P < 0.001). Immunogold localized ET-1 and its receptors to the nuclear/perinuclear space and to the luminal side of endothelial cells of new blood vessels. CONCLUSIONS: In corneal neovascularization, ET-1 protein and mRNA expression is upregulated in epithelial cells. Together with ET-1, ETA, and ETB receptor expression on endothelial cells of ingrown new blood vessels, this points to an involvement of ET-1 and its receptors in corneal angiogenesis. As potent ETA and ETB receptors are available, the endothelin system may represent an additional target for corneal antiangiogenic therapy.     

Histological and immunohistochemical findings after laser in situ keratomileusis in human corneas

PURPOSE: To describe histopathological and immunohistochemical findings in human corneas after myopic laser in situ keratomileusis (LASIK) followed by iatrogenic keratectasia and after hyperopic LASIK. SETTING: Department of Ophthalmology, University of Innsbruck, Innsbruck, Austria. METHODS: Clinical, histological, and immunohistochemical investigations were performed of 1 human cornea with iatrogenic keratectasia following myopic LASIK and 1 human cornea with irregular astigmatism and central scar formation after hyperopic LASIK. Corneal buttons were obtained during penetrating keratoplasty in both patients. RESULTS: Histopathological examination showed thinning of the central stroma with a posterior residual thickness of 190 microm in the patient with iatrogenic keratectasia after myopic LASIK and significant midperipheral thinning in the patient who had hyperopic LASIK. However, this characteristic ablation profile of the stroma after hyperopic LASIK was partially mitigated and compensated by the epithelium, which was significantly thinned in the center and markedly thickened in the midperiphery. Traces of wound healing with minimal scar tissue were present at the flap margin after myopic and hyperopic LASIK. In a few sections of the cornea with keratectasia after myopia LASIK, only a few collagen lamellae were visible crossing between the posterior residual stroma and the superficial flap. Immunohistochemical examination revealed minimally increased staining of dermatan sulfate proteoglycan within the stroma adjacent to the interface of the microkeratome incision. Increased staining of hepatocyte growth factor was found on keratocytes/fibroblasts at the flap margin in both corneas. CONCLUSIONS: The wound-healing response is generally poor after LASIK, which may result in significant weakening of the tensile strength of the cornea after myopic LASIK, probably due to biomechanically ineffective superficial lamella. After LASIK in patients with high hyperopia, compensatory epithelial thickening in the annular midperipheral ablation zone might be partly responsible for regression.     

Expression of vascular endothelial growth factor and its receptors in inflamed and vascularized human corneas

PURPOSE: To help further define the possible role of vascular endothelial growth factor (VEGF) in the pathogenesis of corneal neovascularization, the expression of VEGF and of its receptors Flt-1 and Flk-1 was investigated in various inflammatory corneal diseases. METHODS: Polyclonal antibodies to VEGF and its receptors were used for immunohistochemical staining of frozen sections of 38 human corneas with various degrees of neovascularization and inflammation. In addition, a panel of monoclonal antibodies was used to characterize the composition of the inflammatory infiltrates and to confirm the presence of neovascularization. Furthermore, VEGF concentrations were determined in vascularized corneas using a sensitive enzyme-linked immunosorbent assay. RESULTS: VEGF was expressed by epithelial cells, by corneal endothelial cells, by vascular endothelial cells of limbal vessels and of newly formed vessels in the stroma, and weakly by keratocytes. Furthermore, VEGF expression was often markedly increased in inflamed corneas on epithelial cells and on vascular endothelial cells, particularly in the vicinity of macrophage infiltrates, and on fibroblasts in scar tissue. Correspondingly, VEGF concentrations were significantly higher in vascularized corneas compared with normal control corneas (P < 0.001). Expression of both VEGF receptors, Flt-1 and Flk-1, was increased on endothelial cells of newly formed vessels in the stroma of inflamed corneas compared with limbal vessels of normal control corneas. In addition, Flt-1 was also expressed by corneal endothelial cells and by macrophages, whereas Flk-1 expression was lacking. CONCLUSIONS: These results demonstrate that VEGF, Flt-1, and Flk-1 are strongly expressed in inflamed and vascularized human corneas and, thus, may play an important role in corneal neovascularization.     

Comparison of EphA receptor tyrosine kinases and ephrinA ligand expression to EphB-ephrinB in vascularized corneas

PURPOSE: Eph cell surface receptors and their ligands, ephrins, are involved in neuronal patterning and neovascularization. Our purpose is to compare and characterize the expression of ephrinA ligands and EphA receptors to ephrinB ligands and EphB receptors in excised mouse corneal tissue, in corneal epithelial and keratocyte cell lines, and during corneal angiogenesis. METHODS: Mouse corneal epithelial cells and keratocytes were immortalized using SV40T antigen viral infection of primary cultures. The immortalized epithelial cells and keratocytes were cloned and characterized using antibodies to keratin, vimentin, integrin alpha5beta1, and alpha-smooth muscle actin. Basic fibroblast growth factor pellets were implanted to induce corneal neovascularization. The eyes of wild-type, ephrinB2(tlacZ/+), and EphB4(tlacZ/+) heterozygous mice were harvested and sectioned 7 days after pellet implantation. Confocal immunohistochemistry was performed to compare the expression of the Eph/ephrinA family (EphA1-8, ephrinA1-5) and Eph/ephrinB family (EphB1-4, EphB6 ephrinB1-3). RESULTS: EphA1, EphA3, ephrinA1, ephrinA2, EphB1, EphB4, ephrinB1, and ephrinB2 were detected in wild-type mouse corneal epithelial cells and keratocytes. EphA2 was immunolocalized only in epithelial cells. Also, EphA3, ephrinA1, EphB1, EphB4, and ephrinB1 were immunolocalized to the corneal epithelium and stroma. In the vascularized corneas, ephrinB1 was immunolocalized mainly to the keratocytes around the vessels, and ephrinB2, EphB1, and EphB4 were colocalized mainly with CD31 to the vascular endothelial cells. CONCLUSIONS: The characterization of ephrin ligand and Eph receptor expression during cornea angiogensis in this study suggests that the Eph/ephrin family of receptor tyrosine kinases and their ligands may play a role in the regulation of corneal angiogenesis.     

Distribution of fibronectin in human and rabbit corneas

In order to study the possible role of fibronectin (FN) in corneal wound healing and the relationship between FN and sensory innervation, FN was demonstrated immunohistochemically in both normal and sensorily denervated rabbit corneas and in normal or tissue-cultured human corneas. The distribution of FN was the same in the groups examined: a thin subepithelial band of FN-like immunoreactivity was seen at the level of epithelial basement membrane and at the stromal side of Descemet's membrane. Epithelial abrasions were also performed in both normal and denervated rabbit corneas. The results were compared with those obtained from organ-cultured human corneas. Following abrasion of the corneal epithelium, FN was detected in the anterior margin of the denuded stroma 18 hr after the operation in the areas where the epithelium had not healed, but not 49 hr after. Sensory denervation did not affect the distribution of FN in normal, denervated or healing rabbit cornea. It is concluded that FN is probably not controlled by sensory innervation.     

Preservation of human corneas in organ culture: technical protocol

Using organ-culture preservation human corneas were preserved up to 5 weeks in a modified tissue culture medium at 37 degrees C. The endothelial viability was examined after staining with trypan-blue 0.3%, after determination of endothelial cell density and cell loss and by light microscopy after staining with trypan-blue 0.3% and alizarin red 1%. The biochemical analysis of the medium (pH, glucose, lactate) has allowed the evaluation of three kinds of storage. The influence of time preservation on the endothelial viability and the metabolic conditions are determined. At the end of this study a clinical trial is proposed.     

Characterization of antigen-presenting cells in fresh and cultured human corneas using novel dendritic cell markers

PURPOSE: Adult healthy human corneas bear a distinctive number of antigen-presenting cells (APCs) important for the fate of a graft. The purpose of this study was to differentiate between Langerhans cells (LCs) and other dendritic cells (DCs) and between mature and immature APCs in fresh and cultured human corneas using specific markers. METHODS: Immunofluorescence double staining was performed for Langerin/CD207, CD1a, DC-SIGN/CD209, DC-LAMP/CD208, CD45, CD11c, CD11b and HLA-DR. RESULTS: Langerin(+)/CD1a(+)/HLA-DR(+) LCs (approximately 100 cells/mm(2) in fresh corneas) were found in the limbal and peripheral regions of corneal epithelium and the anterior stroma up to 83 days of culture. All these cells coexpressed CD45 and CD11c. DC-SIGN(+)/CD45(+) DCs (approximately 150 cells/mm(2) in fresh corneas) were detected mainly peripherally and in the anterior stroma, even in long-term cultured corneas. Most of these cells were HLA-DR(-). Few mature DCs (DC-LAMP(+)/HLA-DR(+)) were found in fresh and cultured corneas. Macrophages (CD11c(-)/CD11b(+)) were seen in the peripheral, paracentral, and even central regions of the posterior stroma. CONCLUSIONS: This is the first demonstration that human corneas harbor populations of Langerin(+)/CD1a(+)/HLA-DR(+) LCs and DC-SIGN(+) DCs in a distribution pattern similar to that in the skin. Few APCs are in a mature state (DC-LAMP(+)). Given the reduced but not complete depletion of APCs during organ culture, these grafts still bear a potential risk for rejection.     

Depth and age-dependent distribution of keratocytes in healthy human corneas: a study using scanning-slit confocal microscopy in vivo

PURPOSE: To document keratocyte distribution and changes with age in the cellular network of the human cornea in vivo. SETTING: Department of Ophthalmology, University of Rostock, Rostock, Germany. METHODS: Forty-nine eyes of 31 healthy subjects of various ages were examined with a modified Microphthal scanning-slit confocal microscope (SSCM) (Hund) to document keratocyte distribution in the intact living cornea. Optical sections made by confocal microscopy were recorded on videotape, and the keratocyte density was determined for the total volume of the cornea and for the stromal sublayers. RESULTS: The highest cell density was in the anterior stroma of the cornea immediately posterior to Bowman's membrane (24 320 cells/mm(3) +/- 6740 [SD]), the lowest in the central area (11,610 +/- 4290 cells/mm(3)), and an intermediate density in the posterior stroma immediately adjacent to Descemet's membrane (18,850 +/- 4610 cells/mm(3)). The differences were statistically significant (P <.005). The keratocyte density was significantly lower in the anterior and posterior regions in the group older than 50 years: Cell density at 4% depth was 20,960 +/- 8200 cells/mm(3) and at 96%, 15 520 +/- 4290 cells/mm(3) (P <.05). CONCLUSIONS: In healthy living corneas, the keratocyte density was high in the areas adjacent to Bowman's and Descemet's membranes and was lower in patients older than 50 years than in those younger than 50 years. Further studies are needed to document the rate of change with age and to better understand the role and capacity of aging keratocytes in regenerative processes following corneal diseases or surgical procedures.     

激光共焦显微镜对正常人眼角膜缘和中央角膜的观察

目的应用激光共焦显微镜对正常人眼角膜缘和中央角膜的组织结构与细胞形态的观察和分析。方法选择15名正常人的28只眼接受常规裂隙灯显微镜和检眼镜检查后,作为正常健康眼入选本研究。使用激光共焦显微镜对其上、下方角膜缘和角膜中央区进行检查,各层角膜图像均被记录,观察组织结构和细胞形态,对细胞密度进行计数并分析。结果所获角膜缘和角膜中央各层平面图像(x,y轴)及纵向断层图像(z轴)均非常清晰,同时获取动态录像。上、下方角膜缘均呈现Vogt栅栏状结构,并动态观察到血细胞在血管内的流动。表层上皮细胞排列非常疏松,边界明亮,胞体发暗,上方和下方角膜缘表层上皮细胞平均密度分别为(812±297)个/mm2和(785±263)个/mm2,二者比较差异无统计学意义(P>0.05)。上皮下可见明亮的Langerhans细胞,形态不规则,呈树枝状,上方和下方角膜缘Langerhans细胞平均密度分别为(288±102)个/mm2和(254±127)/mm2,二者比较差异无统计学意义(P>0.05)。角膜中央表层上皮细胞排列疏松,边界发亮,胞体发暗,细胞平均密度为(1098±315)个/mm2,多于上方和下方角膜缘(P<0.05)。基底上皮细胞排列紧密。上皮下和前基质层可见反光强烈的神经纤维丛,旁边偶见明亮的Langerhans细胞,形态不规则,细胞密度难以计算。浅层的神经纤维细小、弯曲度大、多小分支,深层的神经纤维粗大、弯曲度小、少见分支。基质层暗背景下散在分布细长的基质细胞,边缘欠清,细胞核明亮呈纺锤形。内皮细胞为排列整齐的六边形细胞,胞体发亮,边界发暗。角膜中央全层、基质层、上皮层厚度分别为(543.0±62.9)、(462·0±69.5)、(59.9±11.2)μm。结论激光共焦显微镜不仅可以对角膜进行无创的、实时的、活体的检查,而且与传统的光学共焦显微镜相比,具有高清晰度、确切的深度定位、时间动态观察、纵向断层扫描等优势,更可提供理想的角膜缘图像,对角膜疾病尤其是角膜缘疾病的基础研究与临床诊断将更有价值。     

Actin filament localization in developing and pathologic human corneas

Actin is associated with motility, cell morphology, and cell-substrate adhesion. The molecular probe NBD phallacidin, which reacts with filamentous actin, was used to study the distribution of actin filaments in the corneal and conjunctival epithelium, stroma, and endothelium. Frozen sections of human fetal eyes from 8 weeks to 40 weeks of gestation were reacted with NBD phallacidin. Pathologic tissues included keratoplasty specimens from patients with hereditary posterior polymorphous corneal dystrophy (PPMD) and surgically excised tissues removed for treatment of epithelial down-growth. Normal human cornea was used as a control. Immunofluorescent staining disclosed actin filament distribution in corneal epithelium as early as 9-10 weeks of gestation. Staining increased with maturation until term. Adult human corneal epithelium showed more pronounced staining of the surface layers. Stromal staining was more extensive in earlier stages of gestation and decreased in later stages of gestation, after 20-21 weeks. In pathologic corneas with posterior polymorphous dystrophy, there was localization of actin, as well as keratin, in the abnormal epithelial-like layers lining the posterior cornea. In epithelial downgrowth, actin and keratin were demonstrated in multilayered squamous epithelium on the anterior iris surface. Actin appears to be involved in migration of corneal epithelial and endothelial cells.     

VEGF—C、LYVE—1 mRNA在喉鳞癌组织中的表达

目的 探讨血管内皮生长因子C(vascular endothelium growth factor-C,VEGF-C)与淋巴管内皮透明质酸盐受体1(lymphatic vascular endothelial HA receptor-1,LYVE-1)Mrna在喉鳞癌组织中的表达及其与喉鳞癌临床病理特征之间的关系.方法 采用逆转录聚合酶链式反应技术,对40例新鲜喉鳞癌标本及10例癌旁正常喉组织中的VEGF-C、LYVE-1 Mrna表达进行检测.结果 VEGF-C Mrna在喉鳞癌组织与癌旁正常喉组织中的表达,差异有非常显著性(P＜0.01);颈淋巴结转移组VEGF-C Mrna表达高于无颈淋巴结转移组,差异有显著性(P＜0.05);喉鳞癌组织VEGF-C Mrna表达与病变部位、T分期、病理分级未显示有关;喉鳞癌组织未显示有意义的LYVE-1 Mrna表达.结论 喉鳞癌颈淋巴结转移可能与VEGF-C Mrna表达水平有关.     

Laser in situ keratomileusis in human corneas: new organ culture model

PURPOSE: To establish an in vitro model of laser in situ keratomileusis (LASIK) in human donor eyes and to test its validity in comparison with animal models. SETTING: Department of Anatomy, Friedrich-Alexander Unviersity, Erlangen, Germany. METHODS: Laser in situ keratomileusis was performed on 20 organ-cultured human corneal buttons. The excimer laser ablations ranged from 0 to 12.0 diopters. The corneas were maintained in culture for up to 6 months and then evaluated with light microscopy and transmission electron microscopy. In addition, corneal sections were immunohistochemically stained for collagen type III, laminin, and fibronectin. The main outcome measures were the ultrastructural and immunohistochemical features of the stromal incision interface. RESULTS: Ultrastructural investigations in the peripheral cornea revealed a disarrangement of collagen fibers, indicating scar formation. These findings were not observed in the central area. Immunohistochemical staining for fibronectin and collagen type III was detected over the entire stromal incision interface, whereas laminin staining was related to the ingrowth of epithelial cells. CONCLUSIONS: The morphological changes after LASIK in an organ culture model can simulate the in vivo situation. Therefore, this model appears appropriate to use in further study of corneal wound-healing changes after LASIK.     

Integrity of epithelium and endothelium in organ-cultured human corneas.

PURPOSE. To examine components of the junctional complex and the actin cytoskeleton and the incidence of apoptosis in epithelium and endothelium of organ-cultured human corneas. METHODS. Human corneas, either organ-cultured for 1 to >28 days or excised directly from eyes stored in moist chambers, were stained with antibodies to ZO-1, vinculin, and caspase 3 coupled to FITC-conjugated secondary antibody. These markers were combined with rhodamine-phalloidin staining for F-actin and DAPI labeling for DNA. The corneas were examined by confocal microscopy. RESULTS. The depth of the epithelium was reduced during organ culture, but no changes were observed in the distribution of ZO-1 or vinculin, or in the F-actin cytoskeleton. The appearance of apoptotic epithelial cells positive for caspase 3 or with condensed DNA increased with time after 14 days in organ culture, but there was no correlation with donor age. ZO-1 and F-actin staining patterns in endothelium were similarly undisturbed by organ culture, but apoptotic endothelial cells were only rarely seen and then only after >28 days in organ culture. CONCLUSIONS. Organ culture maintained the integrity of tight junctions and the actin cytoskeleton in epithelial and endothelial cell layers. Apoptosis was evident in epithelium but was observed rarely in the endothelium and then only after extended periods in organ culture.     

Extracellular matrix and Na+,K+-ATPase in human corneas following cataract surgery: comparison with bullous keratopathy and Fuchs' dystrophy corneas.

PURPOSE: To examine the distribution of extracellular matrix (ECM) and basement membrane (BM) components and of Na+,K+-ATPase in postcataract surgery (PCS) corneas. These corneas were from patients who never developed pseudophakic or aphakic bullous keratopathy (PBK/ABK) after cataract surgery. PCS corneas were compared with PBK/ABK and Fuchs' dystrophy corneas. METHODS: The distribution of PBKIABK ECM and BM markers and of all three Na+,K+-ATPase alpha subunits was studied by immunofluorescence in 10 healthy, 11 PCS, 16 PBK/ABK, and 12 Fuchs' dystrophy corneas. RESULTS: Fibrotic ECM proteins, tenascin-C and fibrillin-1, were found in only 1 of 10 healthy and in 2 of 11 PCS corneas. In contrast, these proteins were expressed in all PBK/ABK and more than half of the Fuchs' dystrophy corneas. BM components in PCS corneas were altered to a greater extent (40-60%), especially fibronectin and laminin-10. A decreased epithelial immunostaining for Na+,K+-ATPase alpha subunits was seen in approximately 40% of PCS corneas and in approximately two thirds of PBK/ABK and Fuchs' dystrophy corneas. However, the endothelial staining was normal in all groups. CONCLUSIONS: Because tenascin-C and fibrillin-1 were mostly found in diseased but not in PCS corneas, their expression may be related to later, clinical stages of corneal edema development. However, BM components abnormal in PBK/ABK and Fuchs' dystrophy corneas were also altered in PCS corneas without clinical evidence of ocular disease. This may result from subclinical corneal changes resulting from cataract surgery, lens removal, exposure to the intraocular lens, or endothelial cell damage. Alterations of epithelial Na+,K+-ATPase point to the importance of epithelial changes in the development of corneal edematous diseases.     

人类白细胞抗原DR分子和细胞间粘附分子-1在正常和病变角膜的表达及意义

目的　探讨正常及病变角膜中人类白细胞抗原ＤＲ 分子和细胞间粘附分子１ 的表达及其在角膜炎症和移植排斥反应中的作用和影响。方法　应用免疫组化技术对１０ 例正常人及４８ 例患者的病变角膜标本进行人类白细胞抗原ＤＲ分子和细胞间粘附分子１ 的表达的检测。结果　正常人角膜无或轻微表达人类白细胞抗原ＤＲ 分子和细胞间粘附分子１ ;病变角膜,尤其是炎症角膜及角膜移植术后发生排斥反应的角膜,其阳性表达率明显增高。结论　人类白细胞抗原ＤＲ 分子和细胞间粘附分子１ 的异常表达与角膜炎性反应有关,并可促进移植排斥反应的发生