Protective effect of dexamethasone against hypoxia-induced disruption of barrier function in human corneal epithelial cells

The corneal epithelium functions as a barrier to protect the cornea from external agents such as infectious organisms and toxins and thereby contributes to corneal homeostasis. The barrier function of epithelia is dependent on the formation of tight and adherens junctions between adjacent epithelial cells. We have previously shown that hypoxia disrupts the barrier function of cultured human corneal epithelial (HCE) cells by affecting tight junctions. We have now examined the effect of dexamethasone on this barrier disruption induced by hypoxia in HCE cells. Measurement of transepithelial electrical resistance revealed that the hypoxia-induced decrease in the barrier function of HCE cells was inhibited by dexamethasone in a concentration-dependent manner. The hypoxia-induced loss of the tight junction protein ZO-1 from the borders of adjacent HCE cells (as revealed by immunofluorescence analysis) as well as the hypoxia-induced down-regulation of ZO-1 expression (as revealed by immunoblot analysis) were also inhibited by dexamethasone, whereas this drug had no effect on the expression or distribution of the tight junction protein occludin or of the adherens junction proteins E-cadherin and β-catenin. Moreover, dexamethasone attenuated the reorganization of the actin cytoskeleton, the formation of focal adhesions, and the up-regulation of myosin light chain kinase expression induced by hypoxia in HCE cells. Our results thus suggest that dexamethasone protects corneal epithelial cells from the hypoxia-induced disruption of barrier function by maintaining the distribution and expression of ZO-1 as well as the organization of the actin cytoskeleton.     

Protection of human corneal epithelial cells from hypoxia-induced disruption of barrier function by keratinocyte growth factor

PURPOSE: The possible detrimental effect of hypoxia on the barrier function of corneal epithelial cells and whether keratinocyte growth factor (KGF) might protect against such an effect were investigated. METHODS: Simian virus 40-transformed human corneal epithelial (HCE) cells were cultured for 4 days to allow the establishment of barrier function. They were then deprived of serum for 24 hours before exposure to 1% (hypoxia) or 21% (normoxia) oxygen for 24 hours. Barrier function was evaluated by measurement of transepithelial electrical resistance (TER). The localization of ZO-1 and occludin was determined by immunofluorescence microscopy, and the expression of these tight junctional proteins as well as the phosphorylation of the mitogen-activated protein kinases ERK, p38, and JNK were examined by immunoblot analysis. RESULTS: Hypoxia induced a decrease in the TER of HCE cells compared with that of cells maintained under normoxia. The localization of ZO-1 at cell-cell borders was disrupted by hypoxia, whereas the distribution of occludin was not affected. Hypoxia also induced the downregulation of ZO-1 and a decrease in the phosphorylation of ERK without affecting the phosphorylation of p38 or JNK. All these effects of hypoxia were inhibited by KGF. The effects of KGF on TER and ZO-1 localization in cells exposed to hypoxia were inhibited by PD98059, an inhibitor of ERK signaling. Neither hypoxia nor KGF exhibited mitogenic or cytotoxic effects in HCE cells. CONCLUSIONS: Hypoxia induces disruption of the barrier function of HCE cells by eliciting the redistribution and degradation of ZO-1, and this effect is inhibited by KGF in a manner dependent on ERK activation.     

神经生长因子对人角膜上皮细胞增殖的影响

目的研究神经生长因子(nervegrowthfactor,NGF)在体外培养的人角膜上皮细胞中的表达,观察外源性给予NGF对人角膜上皮细胞增殖的作用,进一步探讨NGF在角膜疾病治疗中的意义。方法采用刮片法进行人角膜上皮细胞培养,外源性给予NGF作用于第2代～第3代培养的人角膜上皮细胞,通过四甲基偶氮唑盐(methylthiazolyltetrazolium,MTT)法测定其对细胞增殖的影响,并用流式细胞仪检测角膜上皮细胞中细胞增殖核抗原的表达情况。结果本实验成功培养出人角膜上皮细胞,加入外源性NGF后,培养的人角膜上皮细胞的增殖率较对照组明显增加(P<0.01),流式细胞仪检测到的细胞增殖核抗原的表达也较对照组明显增多(P<0.01)。结论外源性给予NGF对体外培养的人角膜上皮细胞的细胞增殖有明显的促进作用。     

易贝滴眼液治疗角膜上皮点状缺损的初步临床观察

目的　评价易贝滴眼液治疗角膜上皮点状缺损的疗效和安全性。方法　观察角膜上皮点状缺损病例 2 4例 4 4眼 ,随机分成易贝治疗组 11例 2 2眼 ,贝复舒治疗组 13例 2 2眼。 2种滴眼液均滴眼 4次·d-1,于用药后 7、14d和 1月分别观察角膜缺损修复、角膜点染情况。结果　易贝和贝复舒均有明显促进角膜上皮点状缺损痊愈的作用 (P <0 .0 1) ,且治疗前后角膜点染差值 2组间差异无显著性 (P >0 .0 5 )。易贝治疗角膜上皮点状缺损的痊愈率和总有效率治疗 7d分别为 2 0 .0 %、4 5 .0 % ,治疗 14d为 18.8%、5 0 .0 % ,治疗 1月为4 6 .2 %、92 .3% ;贝复舒组治疗 7d分别为 18.2 %、4 0 .9% ,治疗 14d为 35 .3%、4 7.1% ,治疗 1月为 4 6 .2 %、6 9.2 % ;但 2组疗效差异均无统计学意义 (P >0 .0 5 )。观察过程中 2组药物均未出现局部刺激现象及全身不良反应。结论　易贝滴眼液治疗角膜上皮点状缺损安全、有效。     

表皮生长因子对不同区域角膜上皮细胞体外传代培养的影响

目的　观察表皮生长因子 (EGF)对角膜上皮细胞体外传代培养的影响。方法　用抗 Brdu抗体标记法 ,流式细胞仪检测细胞增殖情况。结果　对照组 :中央部细胞传代次数为 ( 5± 1)代 ,周边部的为 ( 7± 1)代 ,角膜缘部的为 ( 8±2 )代。EGF组 :角膜中央及周边部上皮细胞传代次数分别提高 ( 1± 1)及 ( 2± 1)代 ;角膜缘部的增加 ( 5± 1)代。结论　角膜缘细胞在添加EGF后 ,细胞体外传代有显著提高 (P <0 .0 1)。由此提示 :通过进一步改善培养条件 ,体外延长角膜缘部细胞的存活是可能的     

Effects of epidermal growth factor on transforming growth factor-beta1-induced epithelial-mesenchymal transition and potential mechanism in human corneal epithelial cells

AIM: To evaluate the effects of epidermal growth factor (EGF) on transforming growth factor-beta1 (TGF-β1)-induced epithelial-mesenchymal transition (EMT) in human corneal epithelial cells (HCECs). METHODS: HCECs were cultured and treated with TGF-β1 for establishing the model of EMT in vitro. Biological effect of EGF on TGF-β1-induced EMT was evaluated. Proteins and mRNAs expression changes of E-cadherin, N-cadherin and Fibronectin (EMT-relative markers) after TGF-β1 or TGF-β1 combined EGF treatment were detected by Western blot and RT-PCR, respectively. Viability and migration of HCECs were measured by CCK-8, transwell cell migration assay and cell scratch wound healing assay. Activation of Smad2, ERK, p38, JNK and Akt signaling pathways were evaluated by Western blot. Inhibitors of relevant signaling pathways were added to the HCECs to explore the key signal mechanism. RESULTS: With treatment of TGF-β1 only, three EMT-relative proteins and mRNA expression showed that EMT up-regulated in a concentration-dependent and time-dependent manner, with significantly decreasing cell viability (TGF-β1≥5 ng/mL, P<0.05) and increasing cell migration (TGF-β1≥5 ng/mL, P<0.01). The phosphorylation of Smad2 and p38 was a key process of TGF-β1-induced EMT. Meanwhile, EMT-relative proteins and mRNA expression showed that EGF inhibited TGF-β1-indued EMT, with significantly increasing cell viability (EGF≥10 ng/mL, P<0.01). It was noteworthy that EGF significantly enhanced cell migration although EMT was inhibited (EGF≥10 ng/mL, P<0.01), and the blockage of p38 (by SB202190, a p38 inhibitor) was a potential mechanism of this phenomenon. CONCLUSION: EGF inhibits TGF-β1-induced EMT via suppressive p38, and promotes cells proliferation and migration in a non-EMT process by inhibiting p38 pathway.     

神经生长因子对角膜上皮细胞增殖的影响

目的 探讨神经生长因子（nerve growth factor,NGF）对角膜上皮细胞增殖的影响,寻找促进角膜上皮损伤修复的有效方法。方法 在培养兔角膜上皮细胞的培养液中加浓度为5u/ml、50u/ml和500u/ml的NGF,加药后的第3、7天,采用四甲基偶氮唑盐（MTT）法,于酶标仪上测定570nm波长处的吸光度值来观测细胞增殖情况。结论 浓度为50u/ml和500u/ml的NGF对兔角膜上皮细胞增殖有明显促进作用,且两组间有差异,呈剂量依赖性（P＜0.05）,而浓度为5u/ml的NGF促细胞增殖作用不显著（P＞0.05）。结论 外源性NGF对培养的兔角膜上皮细胞增殖有明显促进作用。表明NGF具有临床应用的可能性。     

表皮生长因子对碱烧伤角膜伤口愈合的实验研究

目的　观察鼠表皮生长因子 (m ouse epiderm al grow th factor,m EGF)对角膜上皮创伤修复的作用 ,并探讨其量效关系。方法　采用兔角膜碱烧伤后上皮缺损模型 ,分别给予 0 .5、1、2 g· L- 1m EGF滴眼液治疗 ,生理盐水作对照组 ,每日荧光染色裂隙灯观察、记录 ,疗程 1周。结果　 2 g· L - 1m EGF治疗组与其他 3组有显著性差异 ,0 .5及 1g· L- 1m EG F与对照组之间无显著性差异。结论　尽管量效关系复杂 ,2 g· L- 1m EGF对角膜碱烧伤后上皮缺损的修复起到一定的促进作用。     

Establishment of human corneal epithelial cells stably expressing human connexin43

Corneal epithelial cells communicate with each other through gap junctions. Whereas this property is retained in corneal epithelial cells in primary culture, it is often lost in immortalized epithelial cells. However, the life span of primary cultured corneal epithelial cells is short and the availability of human tissue for their preparation is limited. To examine the role of the gap-junction protein connexin43 (Cx43) in human corneal epithelial cells, we set out to establish an immortal human corneal epithelial cell line that stably expresses this protein. An expression vector encoding human Cx43 fused to enhanced green fluorescent protein (EGFP) was constructed and introduced by transfection into SV40-immortalized human corneal epithelial (HCE) cells. Stable transfectants were isolated by selection with the antibiotic G418. The expression and localization of the Cx43-EGFP fusion protein were examined by immunoblot analysis and fluorescence microscopy, respectively, and gap-junctional intercellular communication was monitored on the basis of dye coupling. HCE cells stably expressing Cx43-EGFP manifested intercellular dye transfer, whereas those stably expressing EGFP alone did not. Cx43-EGFP localized to the interfaces of neighboring cells. Stable expression of Cx43-EGFP in HCE cells did not affect the expression of keratins 3 and 12, which is a characteristic of corneal epithelial cells, but it did inhibit cell proliferation. We have established an HCE cell line that stably expresses human Cx43 and forms functional gap junctions. These cells may prove useful for studies of the role of gap junctions in the human corneal epithelium.     

肝细胞生长因子对人视网膜色素上皮细胞表型的影响

目的 探讨肝细胞生长因子(HGF)对人视网膜色素上皮(RPE)细胞形态及细胞表面抗原的影响.方法 体外培养人RPE细胞,分别采用0.4%小牛血清和重组人HGF因子刺激人RPE细胞,应用相差显微镜观察细胞形态变化;免疫组织化学方法 检测细胞表面抗原细胞角蛋白、波形蛋白、成纤维细胞特异性蛋白-1(Fsp-1)的表达变化;采集经HGF(20 ng/mL)刺激后0、12、24、48 h的RPE细胞应用RT-PCR方法 观察Fsp-1mRNA的表达变化.结果 体外培养的人RPE细胞,在含0.4%小牛血清培养液中呈多角形,贴壁生长融合后呈铺路石样;细胞角蛋白的表达阳性率为89.7%,波形蛋白阳性率为100%,Fsp-1阳性率为45.3%.HGF(20 ng/mL)刺激24 h后,细胞呈长梭形,具有成纤维细胞形态特征;细胞角蛋白阳性率为50.1%(χ2=38.1,P＜0.01),Fsp-1阳性率为91.2%(χ2=48.62,P＜0.01),而波形蛋白表达无明显变化.HGF作用后,Fsp-1mRNA表达升高(F=13.761,P=0.002). 结论 HGF促进人RPE细胞向成纤维细胞的表型转化,提示HGF在RPE细胞上皮-间质转化过程中起重要作用.     

羊膜培养液体外抑制兔角膜上皮细胞血管内皮生长因子的表达

目的:探讨羊膜培养液对角膜上皮细胞中血管内皮细胞生长因子(vascula rendothelial growth factor,VEGF)表达的影响。方法:刮除并收集新鲜兔角膜上皮细胞,传代培养接种于35mm培养皿及自制的羊膜培养皿上。实验分为4组,Ⅰ组(对照组):无血清的DMEM培养液,Ⅱ组:去上皮的羊膜培养液,Ⅲ组:未去上皮的羊膜培养液,Ⅳ组:将细胞直接接种于无上皮羊膜。作用48h后用Trizol法提取各组样本的总RNA,进行RT-PCR一步法反应检测各组VEGF mRNA表达并与β-actin比较。结果:正常角膜上皮细胞中有VEGF基因表达,在Ⅲ,Ⅳ组中表达受到明显抑制(P<0.01,n=5)。结论:羊膜培养液明显抑制VEGF mRNA在角膜上皮细胞中的表达。     

Transforming growth factor beta2-induced myofibroblastic differentiation of human retinal pigment epithelial cells: regulation by extracellular matrix proteins and hepatocyte growth factor

Retinal pigment epithelial (RPE) cells possess the potential to transdifferentiate into myofibroblasts after stimulation with transforming growth factor beta (TGFbeta) and are implicated in the pathogenesis of proliferative vitreoretinopathy. In this study we evaluated how TGFbeta2 and various extracellular matrix (ECM) proteins modulate the transdifferentiation of human fetal retinal pigment epithelial cells (RPE) cells into myofibroblast-like cells. Furthermore, we investigated whether hepatocyte growth factor (HGF) can suppress this transdifferentiation. RPE cells were cultured on ECM coated or uncoated surfaces in the presence or absence of TGFbeta2. HGF was added to certain cultures only once or on a daily basis during the treatment. Transdifferentiation of RPE cells into myofibroblasts was assessed by the quantitation of alpha-smooth muscle actin (alpha-SMA) using immunocytochemistry, flow cytometry, real-time PCR and Western blotting. TGFbeta2 induced a significant increase of alpha-SMA expression in a dose-dependent manner. Compared with growth on uncoated surfaces, RPE cultured on fibronectin (FN)-coated surfaces and stimulated with TGFbeta2 showed a significantly higher alpha-SMA expression than untreated cells. This upregulation of alpha-SMA could be markedly reduced by daily treatment with HGF; however, a single HGF administration did not significantly reduce alpha-SMA. These findings are important for further understanding the interaction of cytokines, RPE cells and their environment in mesenchymal transformation as well as its possible modulation. Continuous or long-term treatment with HGF should be further investigated for its potential to prevent mesenchymal transdifferentiation of RPE cells, and ultimately, PVR in vivo.     

肝细胞生长因子对培养的人晶状体上皮细胞增生及移行作用的研究

目的研究肝细胞生长因子(hepatocyte growth factor,HGF)对体外培养的人晶状体上皮细胞(hu-man lens epithelial cells,HLECs)增生及移行的作用。方法在无血清培养液培养的HLECs中分别加入不同浓度的HGF(2.5、5、10、20、40、50、100μg/L),MTT法测定促细胞增生的情况;流式细胞仪分析细胞周期;HLECs损伤愈合模型,观察不同浓度HGF(10、20、50μg/L)处理24h后HLECs的移行情况。结果HGF浓度处于10、20、40、50μg/L时对HLECs具有促增生作用(P<0.05或P<0.01),增生率分别为10.5%、30.2%、28.3%和11.1%;当浓度为20μg/L作用24h能达到最大促增生效果(P<0.01),增生率为29.6%;HGF通过促进细胞G0向G1的转化来促进细胞的增生;HGF可明显促进HLECs的移行,其移行能力分别为22.1%(10μg/L)、57.7%(20μg/L)和208.6%(50μg/L)。结论HGF可促进HLECs的增生和移行,是HLECs的有丝分裂原和强有力的促移行因子。     

人羊膜匀浆上清液对兔角膜上皮细胞中bFGF表达的影响

目的:观察不同浓度人羊膜匀浆上清液对体外培养的兔角膜上皮细胞碱性成纤维细胞生长因子(basic fibroblast growth factor, bFGF)表达的影响,探讨人羊膜匀浆上清液在促进角膜上皮损伤修复中的作用。方法:将兔角膜上皮细胞离体培养并传代,然后分组。实验组分别在含100mL/L胎牛血清的DMEM培养液中分别加入终浓度为40,80,160μg/mL 的人羊膜匀浆上清液,对照组仅用100mL/L胎牛血清的DMEM培养液。分别在培养24,48和96h后,采用甲基噻唑基四唑(methyl thiazolyl tetrazolium,MTT)比色法观察人羊膜匀浆上清液对兔角膜上皮细胞增殖的影响。同时,采用RT-PCR技术检测三个不同等级浓度对兔角膜上皮细胞bFGF-mRNA表达的影响。结果:培养24h后,与对照组（0.087±0.013）比较,加入终浓度为40,80,160μg/mL人羊膜匀浆上清液的实验组角膜上皮细胞增殖数量（分别为0.185±0.010,0.318±0015,0.501±0.014）明显增加,差异具有显著性(P<0.05);同时,随着作用时间的延长,差异愈加明显;加入40μg/mL和80μg/mL浓度羊膜匀浆上清液组兔角膜的bFGF-mRNA（分别为0.750±0.007,0.785±0.006）和空白对照组（0.708±0.013）比较,差异无显著性意义（P>0.05）,但160μg/mL浓度羊膜匀浆上清液组（1.013±0.120）与其它两组及对照组（0.708±0.013）比较,差异均具有显著性（P<0.05）。结论:人羊膜匀浆上清液具有促进兔角膜上皮细胞增殖的作用,并随着人羊膜匀浆上清液所含蛋白浓度的增加,其促进作用增强;人羊膜匀浆上清液具有促进体外培养的兔角膜上皮细胞bFGF-mRNA表达的作用,但与羊膜匀浆上清液的浓度有关。     

Activation of ERK1/2 MAP kinase pathway induces tight junction disruption in human corneal epithelial cells

Activation of protein kinase C (PKC) by exposure of cultured human corneal epithelial cells to phorbol 12-myristate 13-acetate (PMA) resulted in an increase in paracellular permeability as evidenced by a decrease in transepithelial electrical resistance (TER). A change in the membrane distribution of the tight junction protein ZO-1 was also observed in the PMA-treated cells. In contrast, when the cells were treated with PMA in the presence of PD98059, a specific inhibitor of mitogen-activated protein kinase (MAPK) kinase, all barrier characteristics were preserved, suggesting that PKC induces tight junction disruption through the activation of MAPK. The role of this signaling pathway in the regulation of epithelial permeability was further elucidated by the use of corneal epithelial-derived cell lines expressing constitutively activated (ca) or dominant-negative (dn) mutants of MAPK kinase-1 (MEK1). Transfectants of caMEK1, when compared to parental cells, had higher levels of phosphorylated extracellular regulated protein kinase (ERK), altered distribution of ZO-1 and occludin, and much reduced TER. On the other hand, dnMEK1 transfectants had lower but detectable levels of ERK phosphorylation, more flattened morphology, and, most importantly, significantly higher TER when compared to parental cells. Our study demonstrates that activation of PKC causes the disruption of tight junctions through activation of MAP kinase and that the MAP kinase signaling pathway plays a key role in the regulation of epithelial cell morphology and barrier function in the cornea.     

神经生长因子对兔角膜内皮细胞增殖的影响

目的 探讨神经生长因子（NGF）对角膜内皮细胞增殖的影响。方法 在培养兔角膜内皮细胞的培养液中分别添加5U／ml,50U／ml和500u/ml的NGF,加药后第3,7天采用四甲基偶氮唑盐（MTT）法,在酶标仪上测定570nm波长处的吸光度值来观测细胞增殖情况。结果 与对照组比较,加药后第3,7天,3组的NGF对培养的兔角膜内皮细胞增殖均促进作用（P＜0．01）,且呈剂量依赖性。其中50U／ml组及500U／ml组作用强于5U／ml（P＜0．05）,而50U／ml组和500U／ml组比较作用无差异（P＞0．05）。结论 外源性NGF对培养的兔角膜内皮细胞增殖有明显的促进作用。     

重组人表皮生长因子治疗外伤性角膜上皮缺损

目的　评价重组人表皮生长因子 (rhEGF)滴眼液治疗外伤性角膜上皮缺损的临床疗效。方法　观察 84例外伤性角膜上皮缺损病例 ,随机分成rhEGF滴眼液治疗组和常规治疗对照组 (0 3 %氧氟沙星滴眼液 )各 42例。治疗组用rhEGF滴眼液 ,对照组用 0 3 %氧氟沙星滴眼液 ,每日滴眼 4次 ,共 10天。隔日观察上皮缺损修复情况。结果　rhEGF治疗外伤性角膜上皮缺损的有效率明显高于常规治疗对照组 ,两者差异有非常显著意义 (P <0 0 1)。结论　rhEGF滴眼液治疗外伤性角膜上皮缺损能有效地促进角膜上皮缺损的修复。     

EGF体外对人晶状体上皮细胞迁移的影响

目的:研究表皮生长因子对人晶状体上皮细胞迁移的影响。方法:DMEM 100g/LFBS将人晶状体上皮细胞培养在T-25培养瓶内,划痕法检测EGF的促细胞迁移作用,蛋白质免疫印迹(Westernblot)方法检测β-catenin蛋白表达。结果:人晶状体上皮细胞在20μg/LEGF作用下,其迁移距离随着作用时间的延长而增加,在48h达到高峰;人晶状体上皮细胞在不同浓度EGF作用48h后,其迁移距离随着EGF浓度的增加而增加,在20μg/L时达到高峰;人晶状体上皮细胞在10μg/LEGF作用下,β-catenin蛋白表达水平随着作用时间的延长而升高,在2h达到高峰;人晶状体上皮细胞在不同浓度EGF作用2h,β-catenin蛋白表达水平随着EGF浓度的增加而升高,在10μg/LEGF作用下达到最大值。结论:EGF对人晶状体上皮细胞具有促进其迁移的作用,β-catenin在晶状体上皮细胞中的表达趋势说明其在晶状体上皮细胞迁移过程中起重要的作用。     

透镜诱导型近视眼视网膜色素上皮细胞肝细胞生长因子表达的变化

目的观察豚鼠镜片诱导型近视眼（LIM）眼球前部及后极部视网膜色素上皮（RPE）细胞中肝细胞生长因子（HGF）的表达变化,探讨近视眼的发病机制。方法取2周龄豚鼠10只,随机选择一眼作为实验眼,制备近视眼模型（眼前配戴凹透镜45d）,对侧眼作为自身对照。实验前后测量豚鼠双眼屈光度和眼轴长度。原代培养豚鼠视网膜前部及后极部RPE细胞,传1代后,对各组RPE细胞HGF表达进行免疫细胞化学分析。采用SPSS12．0统计软件对相关数据进行配对t检验和单因素方差分析。结果①豚鼠经过45d的透镜诱导后,形成（-6．70±1．93）D的相对近视,眼轴延长（1．53±0．31）mm,前后差异有统计学意义（t=-9．25,t=9．17,P〈0．05）,近视模型造模成功。②在光镜下观察免疫细胞化学爬片显示．HGF存RPE细胞中的表达定位于细胞浆,细胞核无着色。近视眼前部和后极部RPE细胞的HGF表达明最高于自身对照组,差异有统计学意义（P〈0．05）;近视模型眼和对照眼自身前部与后极部HGF表达比较,差异无统计学意义（P〉0．05）。结论体外培养的豚鼠RPE细胞稳定表达HGF：HGF在近视模型眼前部和后极部RPE细胞中的活性都升高,参与了实验性近视眼的形成。