The effects of hypertonic salicylate on neutrophil migration and vascularization in the rat cornea

Thermal cauterization of the center of the rat cornea results in emigration of neutrophils into the extravascular limbal tissue and blood vessel growth into the cornea. In this study, 1.0 M sodium salicylate, 1.0 M sodium chloride, and ointment vehicle were administered to normal and cauterized rat corneas for periods of 6, 48, and 144 h. When applied to the normal cornea, salicylate resulted in a marked increase in neutrophils in the limbal tissue at 6 h, but an inhibition at 48 h. Similarly, for the cauterized corneas, administration of salicylate increased the extent of neutrophil emigration at 6 h, but this effect was not sustained at 48 h. Neither vehicle nor sodium chloride had any effect on the extravascular neutrophil population. After 6 days, administration of the vehicle resulted in a slight increase in vascular growth into the cornea, whereas sodium salicylate caused a decrease. These findings indicate that hypertonic (1 M) sodium salicylate does not inhibit the emigration of neutrophils from limbal vessels of cauterized rat corneas, but does appear to have a cytotoxic effect on the tissues and on blood vessel endothelial cells.     

大鼠角膜化学伤后PEDF和VEGF的不平衡表达

目的比较硝酸银化学伤后大鼠角膜和正常角膜色素上皮衍生因子（PEDF）和血管内皮生长因子（VEGF）表达水平，揭示两者与角膜新生血管的相关性。方法10只大鼠左眼角膜硝酸银化学伤后为实验组，右眼为正常对照组，伤后15d行免疫组织化学法定位及Western blot定量检测样本角膜PEDF、VEGF等的表达。结果免疫组织化学检查：实验组角膜VEGF、碱性成纤维细胞生长因子（bFGF）强表达，PEDF未见表达或弱表达。正常组角膜PEDF高表达，VEGF弱表达，bFGF几乎不表达。Western Blot分析：实验组角膜PEDF表达明显下降（t=8．0049，P〈0．01），VEGF表达显著升高（t=48．3637，P〈0．01）。结论角膜严重化学伤后新生血管抑制因子PEDF破坏，刺激因子VEGF产生增加，PEDF／VEGF比值降低，角膜血管新生。     

Time course of angiogenesis and lymphangiogenesis after brief corneal inflammation

PURPOSE: To study the time course of angiogenesis and lymphangiogenesis in the cornea after a short inflammatory insult. This might be helpful for the timing of corneal transplantation in high-risk eyes. METHODS: The mouse model of suture-induced inflammatory corneal neovascularization was used. After placement of 3 interrupted 11-0 sutures into the corneal stroma of BALB/c mice (left in place for 14 days), corneas were excised 2, 3, 5, 7, 14, and 21 days as well as 1, 2, 3, 6, and 8 months after surgery. Hem- and lymphangiogenesis were evaluated using double immunohistochemistry of corneas with CD31/PECAM1 as panendothelial and LYVE-1 as lymphatic endothelial marker. RESULTS: Both blood and lymphatic vessels grew into the cornea as early as day 2 after suture placement. The outgrowth was initially parallel. Hem- and lymphangiogenesis peaked around day 14. Thereafter, both vessel types started to regress. Regression of lymphatic vessels started earlier and was more pronounced than that of blood vessels. Whereas at 6 and 8 months (partly) perfused CD31+++/LYVE-1(-) blood vessels and (nonperfused) ghost vessels could still be observed, there were no CD31+/LYVE-1+++ lymphatic vessels detectable beyond 6 months after this short inflammation. CONCLUSIONS: After a temporary inflammatory insult to the cornea, there is initially parallel outgrowth of both blood and lymphatic vessels. But thereafter, lymphatic vessels regress earlier than blood vessels and are completely regressed by 6 months. Earlier regression of pathologic corneal lymph versus blood vessels suggests that corneal graft survival in high-risk eyes might best be delayed for a prolonged interval following an inflammatory insult.     

Platelet response to corneal abrasion is necessary for acute inflammation and efficient re-epithelialization

PURPOSE: Adhesion molecules play a critical role in leukocyte emigration to wound sites, but differences are evident in different vascular beds. In this study, the contributions of P-selectin to neutrophil emigration into the cornea after central epithelial abrasion were investigated. METHODS: Re-epithelialization, neutrophil influx, and platelet accumulation were assessed in C57BL/6 mice after removal of a 2-mm diameter area of central corneal epithelium that did not directly injure the limbal vessels or the avascular stroma of the cornea. Comparisons were made between wild-type (WT) mice and mice with targeted deletions of genes for P-selectin, CD18, or CD54, or mice with antibody-induced neutropenia or thrombocytopenia. RESULTS: After central corneal epithelial abrasion, platelets localized in the limbal vessels and neutrophils emigrated from the limbal vessels to the region of the epithelial wound. There was temporal correspondence of platelet and neutrophil localization, peaking within 12 hours of wounding. Platelet accumulation, neutrophil emigration and corneal epithelial healing as measured by wound closure, basal epithelial cell density, and epithelial cell division were significantly reduced in P-selectin-deficient mice (P-sel(-/-)). Anti-GP1balpha antibody-induced thrombocytopenia in WT mice significantly reduced platelet and neutrophil accumulation and wound healing. Passive transfer of wild-type platelets into P-sel(-/-) mice significantly restored platelet localization in limbal vessels, neutrophil emigration, epithelial cell division, and epithelial cell migration into the abraded region of the cornea. CONCLUSIONS: Platelet localization in the limbus of abraded corneas contributes to re-epithelialization, and P-selectin provides a necessary step in this process.     

Short- and long-term corneal vascular effects of tafluprost eye drops

Background

Prostaglandin analogs are first line therapy in the treatment of glaucoma, but also display side effects during ocular inflammation. In this context, the potential side effects of prostaglandin analogs on the normally avascular cornea, the main application route for eye drops, are so far not fully defined. Therefore, the aim of this study was to evaluate the vascular effects of the prostaglandin analog tafluprost on the healthy and inflamed cornea.

Methods

For in vitro studies, blood and lymphatic endothelial cells were treated with tafluprost; cell proliferation was assessed after 48 h. For long-term in vivo studies under healthy conditions, naïve corneas of BALB/c mice were treated with tafluprost eye drops for 4 weeks. For short-term in vivo studies under inflammatory conditions, corneal inflammation was induced by suture placement; mice then received tafluprost eye drops for 1 week. Afterwards, corneas were stained with CD31 as panendothelial and LYVE-1 as lymphendothelial (and macrophage) marker.

Results

In vitro, tafluprost did not alter blood or lymphatic endothelial cell proliferation. In vivo, there was no change in limbal blood or lymphatic vessel anatomy after long-term treatment with tafluprost. Short-term treatment with tafluprost under inflammatory conditions did not influence the recruitment of LYVE-1 positive macrophages into the cornea. Moreover, treatment of inflamed corneas with tafluprost did not significantly influence corneal hem- and lymphangiogenesis.

Conclusions

Tafluprost does not affect blood and lymphatic vessel growth, neither under resting nor under inflammatory conditions. These findings suggest a safe vascular profile of tafluprost eye drops at the inflammatory neovascularized cornea.     

In vivo observations on experimental corneal neovascularization with a newly developed macroscope

The process of corneal neovascularization induced by alkali burns was periodically observed with a newly developed macroscope. The central corneas were burned using filter discs measuring 6 mm in diameter that had been immersed in 1 N NaOH. At 0, 1, 3 and 7 days and at 2, 3 and 4 weeks after injury, the corneas were observed with the macroscope and then examined histologically. At 1 day post-burn, the limbal vascular plexus was engorged but no new vessel formation was detected. By 3 days, many vascular sprouts had arisen from the limbal vascular arcade. At 7 days, the vascular sprouts grew and became fine new vessels. At 2 weeks, the new vessels lengthened further to the central cornea. At 3 weeks, trunk vessels extended and branched like a vascular tree. Blood in the trunk vessels appeared to flow slowly to and fro. The ends of the vessels swelled in a fusiform shape on the application of slight pressure of the macroscope probe. Histological examination revealed that the ends of the vessels consisted of single vascular endothelial cells and the trunk vessels were covered by pericytes. By 4 weeks, the branch vessels around the burned lesion had degenerated and collapsed. Thus, our in vivo study using the new macroscope not only clarified the process of corneal neovascularization from the early to the regressive phases but also provided some valuable new information.     

Limbal vascular response prior to corneal vascularization

In spite of claims of a significant latent period of up to 2 days between corneal injury and the beginning of corneal vascularization, there is evidence of a limbal reaction occurring only hours after injury. In this study, the central area of rat corneas was cauterized to give an injury which was remote from the limbal vessels. The resulting changes in vascular permeability were investigated. Significant emigration of neutrophil polymorphonuclear leucocytes began at 36 min and leakage of Trypan blue was discernible at about 1 hr after injury. Eosinophilic leucocytes do not appear to be involved in the response and mast cells, while not showing signs of increased degranulation, may be decreased in number over several days. The significance of these results in relation to the stimulus factors involved in these changes, and the importance of separating inflammatory and proliferative changes, are diseussed.     

Involvement of cysteine proteases in bFGF-induced angiogenesis in guinea pig and rat cornea.

Overexpression and activation of matrix metalloprotease (MMP) have been implicated in angiogenesis. However, the involvement of cysteine proteases, such as calpains (EC 34.22.17), is obscure. Thus, the purpose of this experiment was to study the involvement of cysteine proteases in angiogenesis induced by basic fibroblast growth factor (bFGF) in guinea pig and rat corneas using cysteine protease inhibitors. Sustained-release polymers containing bFGF were implanted into guinea pig and rat corneas to induce angiogenesis. For treatment of corneal angiogenesis, polymers containing cysteine protease inhibitors, leupeptin or SJA6017, were also implanted into corneas. Using the slit lamp, the corneas were observed for nine days after polymer implantation. Soluble proteins and albumin levels were used as markers of corneal injury by angiogenesis. bFGF induced angiogenesis in guinea pig and rat corneas. In guinea pig cornea, wet weight, the amount of soluble protein and albumin was highest at four days after bFGF-containing pellet implantation. In rat cornea, the amount of soluble protein and albumin was highest at six days, and wet weight increased within four days. One hundred nmole of leupeptin showed a tendency to reduce bFGF-induced angiogenesis in guinea pig cornea, and 10 nmole of SJA6017 was effective in reducing bFGF-induced angiogenesis in rat cornea, although SJA6017 showed a stronger effect than leupeptin. Ten nmole of SJA6017 significantly reduced the number of new blood vessels. These data suggested involvement of cysteine proteases in angiogenesis in guinea pig and rat cornea.     

中性粒细胞在不同品系正常小鼠角膜的分布及其与角膜创伤修复的关系

背景 以往人们通常认为角膜无血管、无髓系来源的免疫细胞存在.C57BL/6J小鼠、BALB/c小鼠和裸鼠是眼科免疫学基础研究的常用模型,这些小鼠的角膜是否存在天然免疫的关键细胞——中性粒细胞是值得关注的问题. 目的 研究实验室常用的C57BL/6J鼠、BALB/c鼠和裸鼠正常角膜的中性粒细胞分布特征及其与角膜创伤修复的关系,为相关研究提供依据. 方法 选取角膜正常、10 ～ 12周龄的SPF级雄性C57BL/6J鼠、BALB/c鼠和BALB/c背景的裸鼠各16只,取3种小鼠各8只制备成中央区相连的4瓣角膜铺片,并以角膜周边血管缘为界向内以3个同心圆分区.分别用Gr-1-FITC抗体和CD31/PECAM-1-PE抗体对角膜中性粒细胞和血管进行免疫荧光染色,用免疫荧光显微镜和AR软件测量角膜血管面积并计数中性粒细胞.选取3种小鼠各8只制备角膜创伤模型,用无菌手术刀片以角膜中央为中心做十字划痕,深度至角膜前弹力层.创伤后即刻（0 h）、12h、24 h用2 g/L荧光素钠点眼,荧光显微镜下以AR软件计算不同时间点的创伤面积.于划痕后24 h取小鼠角膜制备铺片,用Gr-1-FITC抗体和CD31/PECAM-1-PE抗体行荧光染色,比较3种创伤小鼠角膜的血管分布、中性粒细胞的数量和分布情况.实验动物的饲养与使用均遵循美国视觉与眼科研究协会制定的科研动物使用规范. 结果 正常C57BL/6J小鼠、BALB/c小鼠和裸鼠角膜中性粒细胞总数分别为（1 733±237）、（353±96）和（1 601 ±223）个/角膜,BALB/c小鼠角膜中性粒细胞数明显少于C57BL/6J小鼠和裸鼠,差异均有统计学意义（P＜0.01）.3种正常小鼠角膜缘均可见血管分布,BALB/c小鼠角膜缘血管面积明显小于C57BL/6J小鼠和裸鼠,C57BL/6J小鼠角膜缘血管面积明显大于裸鼠,差异均有统计学意义（P＜0.01）.3种正常小鼠中性粒细胞的数量与血管面积均呈明显正相关（C57BL/6J：r=0.936,P=0.001;BALB/c：r =0.939,P=0.001;     

Plasminogen activator (urokinase) causes vascularization of the cornea

The presence of a peripheral zone of (presumed intracellular) plasminogen activator in the normal rabbit cornea has suggested that activator, once released, might regulate the permeability of limbal vessels and angiogenesis, by plasmin-dependent pathways. Plasminogen activator (urokinase [UK]) in rabbit serum albumin (RSA) was injected once (20 microliter, 3.7 CTA U) into the corneal stroma, 2 mm from the limbus. Sprouts arose from the engorged circumlimbal vessels (16 of 20 corneas) beginning on the third day and grew into the cornea over the next several days. Histologically, PMNs were observed in association with growing vessels. Contralateral corneas injected with UK (in RSA) previously inactivated by 99.7% with the specific active site inhibitor, Phe-Ala-Arg-chloromethyl ketone showed minimal vessel engorgement or stromal edema and no vascularization (0 to 20 corneas). Injuries to the so-called (plasminogen activator-containing)"critical zone" of the cornea which elicit neovascularization possibly do so by causing extracellular release of endogenous plasminogen activator. Thus, in addition to initiating the destructive events of ulceration, activator might initiate increases in vessel permeability and also neovascularization, which would result in the eventual arrest of ulceration.     

高糖抑制角膜缘干细胞间质性及其迁移能力的研究

目的　探讨高糖环境对角膜缘干细胞增殖、迁移能力及表面分子标志的影响。方法　通过细胞免疫荧光、细胞增殖检测（CCK-8）、划痕和Transwell实验观察角膜缘干细胞在高糖环境下的迁移及增殖能力的改变。选取16只SPF级大鼠用链脲霉素进行糖尿病造模，14只正常SPF级大鼠作为对照组，刮除两组大鼠角膜上皮观察上皮创伤愈合情况，采用HE染色和免疫组织化学染色探讨糖尿病对角膜缘干细胞表面分子标志及细胞状态的影响。结果　高糖可导致体外培养的角膜缘干细胞增殖减慢，24 h、48 h及72 h增殖率为0.728、0.345及0.395，较对照组明显降低（P<0.05），迁移功能障碍（48 h时正常对照组迁移率为100%，高糖组为17.6%）；高糖组细胞表面分子β-catenin和vimentin的mRNA和蛋白表达水平降低、细胞内定位异常。糖尿病大鼠角膜上皮创伤后愈合延迟，角膜组织HE染色发现糖尿病大鼠角膜上皮层变薄，基底细胞结构紊乱、形态异常。角膜免疫组织化学染色发现与对照组相比，角膜基底细胞的vimentin和β-catenin蛋白表达明显降低。结论　高糖可导致角膜缘干细胞迁移障碍和增殖抑制，其损伤机制与高糖导致角膜缘干细胞表面分子标志的丢失有关。     

FasL-Fas interactions regulate neovascularization in the cornea

PURPOSE: Neovascularization of the avascular cornea is a significant problem associated with many corneal diseases. Because Fas ligand (FasL) is highly expressed in the cornea, the role of this molecule in controlling corneal neovascularization was examined in this study. METHODS: C57BL/6(B6), FasL (CD95L)-deficient B6-gld, and Fas (CD95)-deficient B6-lpr mice were subjected to the suture model of neovascularization. Corneas were evaluated for neovascularization and representative samples subjected to immunohistochemical analysis for expression of Fas antigen and CD31 (platelet-endothelial cell adhesion molecule [PECAM-1]) on vessels that were present in the tissue. Corneas were also explanted and placed in collagen gel cultures to test the ability of anti-Fas antibody to prevent vessel extension from explanted corneas. RESULTS: Immunohistochemical data demonstrated that quiescent vessels express CD31 alone, whereas vessels that penetrate the cornea coexpressed both the Fas antigen and CD31. A significant increase was observed in neovascularization in FasL-deficient B6-gld corneas compared with B6 corneas, and new vessel growth in both B6 and B6-gld was inhibited by anti-Fas antibody. Whereas Fas-deficient B6-lpr corneas displayed significantly less neovascularization than normal B6, B6-lpr mice express Fas on growing vessels. In corneal explant cultures, vessel growth from B6 and lpr mice corneas was inhibited by anti-Fas antibody, confirming functional Fas expression in B6-lpr mice. CONCLUSIONS: These data indicate that FasL is an important factor in controlling corneal neovascularization.     

Expression of HGF, KGF, EGF and receptor messenger RNAs following corneal epithelial wounding

Hepatocyte growth factor (HGF), keratinocyte growth factor (KGF), epidermal growth factor (EGF), and their receptors have been associated with homeostasis and wound healing in the cornea. The purpose of this study was to examine the expression of the messenger RNAs for these growth factors and receptors in a wounded series of mouse corneas using in situ hybridization. In situ hybridization was performed with 3H-labeled riboprobes on unwounded corneas and corneas at 30 minutes, 4, 12, 24, 48 and 72 hr, and 7 days after epithelial scrape wounds in Balb/C mice. Qualitative and semi-quantitative analyses were performed. Expression of HGF, KGF and EGF mRNAs in keratocytes in the unwounded cornea was low. EGF mRNA was also expressed in unwounded corneal epithelium. Following wounding, however, these growth factor mRNAs were markedly upregulated in keratocytes. EGF mRNA expression in the epithelium appeared unaffected by wounding. At seven days after wounding and several days following closure of the epithelial defect, HGF mRNA and KGF mRNA were still expressed at higher levels in keratocytes compared with unwounded corneas. No difference in expression of HGF or KGF mRNAs between limbal, peripheral corneal, or central corneal keratocytes was noted in the unwounded cornea, KGF receptor mRNA was prominently expressed throughout the unwounded corneal epithelium. HGF receptor mRNA and EGF receptor mRNAs were expressed at low levels in unwounded cornea epithelium. Following scrape injury, expression of HGF receptor mRNA and KGF receptor mRNA were markedly upregulated in the corneal epithelium, while no significant increase in EGF receptor mRNA expression was noted. These studies suggest a prominent role for HGF and KGF in modulating corneal epithelial wound healing following injury. Less prominent changes in EGF mRNA and EGF receptor mRNA in the corneal epithelium following wounding may suggest that EGF has more of a role in homeostasis in the mouse corneal epithelium.     

Muc4 expression during blood vessel formation in damaged rat cornea

PURPOSE: To determine the timing of Muc4 expression during the association of endothelial cells to form blood vessels in the rat corneal stroma after corneal wounding. METHODS: Corneal damage was inflicted using brief cauterization with silver nitrite. Contralateral and wounded corneas were examined at time periods after wounding by immunohistochemistry and immunofluorescence for Muc4 and for the blood vessel endothelial cell marker von Willebrand Factor. RESULTS: Blood vessels and von Willebrand Factor-stained cells were very sparse in corneal stroma from unwounded corneas. In contrast, aggregates of von Willebrand Factor-stained cells were prevalent in wounded corneas at days 4-5 and 7-10. Muc4 expression was limited at days 4-5, but extensive at days 7-10. CONCLUSION: Muc4 expression develops in endothelial cells during the mid-stages of cell aggregation and blood vessel formation.     

Binding of basic fibroblast growth factor to normal and neovascularized rabbit cornea.

The labeling pattern of frozen sections of rabbit cornea incubated with radioiodinated basic fibroblast growth factor (bFGF) was investigated in normal corneas and prostaglandin-induced neovascularized corneas by autoradiography followed by image analysis. 125I-bFGF binds to Bowman's, Descemet's, and vascular basement membranes in a dose-dependent manner. The specificity of the binding of bFGF to basement membrane was demonstrated by the following experiments: 1) an excess of unlabeled growth factor displaced the labeling; 2) histones did not modify the labeling; and 3) 2 M NaCl washing and enzymatic treatment with heparitinase prevented binding of labeled growth factor without apparent destruction of the overall structure of the basement membrane. Our results suggest that bFGF binds to the heparan sulfate proteoglycan of basement membranes. Both normal limbal vessels and the newly formed corneal vessels exhibited the same type of labeling but with different intensities, according to the degree of maturation of the new vessels. bFGF binding also is located clearly on the endothelial cells in both types of vessels. This second binding site could correspond to the high affinity receptors on the cell surface and suggests a direct interaction of bFGF with endothelial cells during new vessel formation.     

鼠角膜碱烧伤后新生淋巴管上血管内皮生长因子受体-3的表达和意义

目的探讨鼠角膜碱烧伤后血管内皮生长因子受体-3(VEGFR-3)在新生淋巴管上的表达和意义,进一步证实角膜新生淋巴管的存在。方法在大鼠角膜上制作碱烧伤模型,应用免疫组化法检测第3、5、7天角膜中VEGFR-3蛋白的表达。电镜观测伤后第5、7、10、14天角膜新生淋巴管的情况。结果碱烧伤后,大鼠角膜组织中VEGFR-3表达从第3天开始明显上升,并于第5天达到最高峰,伤后第14天出现新生淋巴管。结论角膜碱烧伤后有新生淋巴管长入,VEGFR-3可能成为抑制角膜新生淋巴管的一个新靶点。     

Impaired eosinophil recruitment to the cornea in P-selectin-deficient mice in Onchocerca volvulus keratitis (River blindness)

PURPOSE: A murine model of helminth-induced keratitis (river blindness) that is characterized by a biphasic recruitment of neutrophils (days 1-3) and eosinophils (days 3+) to the cornea has been developed. The purpose of this study was to determine the relative contribution of P- and E-selectin in recruitment of these inflammatory cells from limbal vessels to the corneal stroma. METHODS: P- and E-selectin gene knockout (-/-) mice were immunized with antigens extracted from the parasitic helminth Onchocerca volvulus. One week after the last immunization, parasite antigens were injected directly into the corneal stroma. Mice were killed on days 1 and 3 postchallenge, and eyes were immunostained with either anti-eosinophil major basic protein (MBP) or with anti-neutrophil Ab. The number of cells in the cornea was determined by direct counting. RESULTS: Recruitment of eosinophils to the cornea was significantly impaired in P-selectin(-/-) mice (63.9% fewer eosinophils on day 1 [P: = 0.0015], and 61% fewer on day 3 [P: < 0.0001]) compared with control C57BL/6 mice. In contrast, P-selectin deficiency had no effect on neutrophil recruitment to the cornea. There was no inhibition of eosinophil and neutrophil migration to the corneas of E-selectin(-/-) mice, indicating that there is no direct role for this adhesion molecule in helminth-induced keratitis. CONCLUSIONS: The present study demonstrates that P-selectin is an important mediator of eosinophil recruitment to the cornea. P-selectin interactions may therefore be potential targets for immunotherapy in eosinophil-mediated ocular inflammation.