RGDRGD肽对人晶状体上皮细胞黏附与增生作用的影响

背景RGD肽是一类含有精氨酸-甘氨酸-天冬氨酸的小分子多肽,其在抑制肿瘤细胞黏附、转移和肿瘤新生血管的生成中起重要作用。研究证实RGD肽能够抑制晶状体上皮细胞（LECs）的黏附和增生,RGDRGD肽串联起来作用增强。目的研究RGDRGD肽对体外培养的人LECs黏附与增生的影响,并与RGD肽的作用进行比较。方法将在体外分离培养的LECs中分别加入250、500、1000mg／L的RGDRGD肽和RGD肽作为实验组,仅加入细胞培养液作为对照组。将LECs以2×10。／ml密度接种到含有纤维连接蛋白（FN）和I型胶原蛋白预孵化的96孔培养板中,培养1h后用MTT比色法检测RGDRGD肽与RGD肽对细胞黏附率的影响。将LECs接种于培养板,分别加入250、500、1000、2000mg／L的RGDRGD肽和RGD肽培养24、48、72h,检测RGDRGD肽和RGD肽对LECs增生的影响。结果RGDRGD肽对人LECs黏附率的抑制呈明显的剂量依赖性,随着其质量浓度的增加,对细胞黏附的抑制作用越强,500mg／L的RGDRGD肽比RGD肽抑制人LECs黏附的作用更强（P〈0．01）。RGDRGD肽对人LECs增生的抑制呈明显的时间剂量依赖性,1000mg／L的RGDRGD肽作用48h比RGD肽对人LECs增生的抑制作用更强（P〈0．01）。结论RGDRGD肽抑制LECs黏附与增生的作用强于RGD肽,为进一步临床应用提供了理论依据。     

Production of fibronectin and tenascin isoforms and their role in the adhesion of human immortalized corneal epithelial cells

PURPOSE: To study the production and deposition of fibronectin (Fn) isoforms and tenascin-C (Tn-C) by immortalized human corneal epithelial (HCE) cells and their integrin-dependent adhesion characteristics. METHODS: Indirect immunofluorescence with isoform-specific monoclonal antibodies (mAbs) was used to study extracellular matrix (ECM) protein composition and their integrin receptors in HCE cells. The synthesis of proteins was studied by Western blot analysis and adhesion by quantitative adhesion assay. RESULTS: HCE cells deposited fibrillar matrix containing extradomain EDA-Fn and sparser deposits of Onc-Fn, whereas Tn-C was deposited diffusely. EDA-Fn was present both in ECM and in culture medium, whereas Tn-C was present only in ECM. Fn-binding integrin (Int) alpha(5) subunit was present in subconfluent cells in focal adhesions (FAs) and matrix adhesions, whereas Int alpha(v)beta(5) was present in FAs in sparse cultures and as ringlike structures in denser cultures. Int alpha(v)beta(6) was colocalized with Int alpha(5) in FAs, only in cells adhering to growth substratum coated with Fn or Fn/Tn-C. Ints alpha(5)beta(1) and alpha(v)beta(6) mediated adhesion to Fn and Int alpha(v)beta(5) mediated adhesion to Vn, and both were inhibited by RGD peptide. The cells failed to adhere to Tn-C but adhered to Fn/Tn-C and were then more efficiently inhibited by the function-blocking integrin mAbs and RGD peptide. CONCLUSIONS: The results suggest corneal epithelial cells as the possible source for Fn isoforms and Tn-C in wound healing and pathologic conditions. The presence of Tn-C only in ECM suggest a vectorial deposition and adhesion experiments also indicate a role for Tn-C in Fn functioning.     

Stimulation of corneal epithelial migration by a synthetic peptide (PHSRN) corresponding to the second cell-binding site of fibronectin

PURPOSE: Fibronectin plays an important role in the migration of corneal epithelial cells in vivo. The Arg-Gly-Asp (RGD) sequence in the principal cell binding domain of fibronectin mediates the interaction of fibronectin with integrins, whereas the Pro-His-Ser-Arg-Asn (PHSRN) sequence of fibronectin is thought to modulate this interaction. The authors examined the effects of a PHSRN peptide on corneal epithelial migration in vitro and in vivo. METHODS: Epithelial migration in vitro was examined with the rabbit cornea in organ culture. The motility and phenotype of simian virus 40-transformed human corneal epithelial (HCE) cells were evaluated by time-lapse and immunofluorescence microscopy, respectively. Tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin was examined by immunoprecipitation and immunoblot analysis. The healing of rabbit corneal epithelial wounds induced by 1-heptanol was evaluated by fluorescein staining. RESULTS: The PHSRN peptide stimulated corneal epithelial migration in organ culture in a concentration-dependent manner, and it increased HCE cell motility in vitro. The peptide induced the accumulation of F-actin and the formation of focal adhesions at the leading edge of HCE cells. It also upregulated the tyrosine phosphorylation of FAK and paxillin in HCE cells, but it did not affect HCE cell proliferation or attachment to a fibronectin matrix. Administration of the PHSRN peptide in eye drops promoted corneal epithelial wound closure in vivo in a dose-dependent manner. None of these effects of the PHSRN peptide were induced by a control NRSHP peptide. CONCLUSIONS: The PHSRN peptide mimics many of the effects of fibronectin on corneal epithelial cells and may prove suitable as a substitute for fibronectin in the treatment of persistent corneal epithelial defects.     

BIGH3基因定点突变体R555W的构建及其对人角膜上皮细胞的影响

目的 构建野生型BIGH3和突变型R555W-BIGH3基因的真核表达载体,探讨其过表达对人角膜上皮细胞的影响.方法 以pMD18-T/BIGH3载体为模板扩增野生型BIGH3基因全长编码序列,克隆至真核表达载体pIRES2-EGFP上,采用快速体外定点诱变技术获得R555W突变体.瞬时转染体外培养的人角膜上皮细胞,免疫印迹检测野生与突变型BIGH3基因的表达,流式细胞仪和透射电镜定量和定性检查细胞凋亡,分析caspase3活性.多组间数据采用单因素方差分析进行统计学处理.结果 PCR成功扩增了野生型和R555W突变型的BIGH3基因.荧光显微镜下可见成功转染BIGH3/R555W-BIGH3-pIRES2-EGFP的CRL-11135细胞发绿色荧光,转染率为30.1%.瞬时转染48 h后的HCE细胞的上清液及其细胞裂解液免疫印迹分析显示,BIGH3/R555W-BIGH3-pIRES2-EGFP两组免疫印迹条带的密度比分别为1.26±0.06和1.27±0.08.正常HCE细胞组、转染pIRES2-EGFP空质粒及BIGH3-pIRES2-EGFP细胞凋亡率分别为(1.49 ±0.02)%、(1.53 ±0.02)%、(1.50 ±0.06)%,转染R555W-BIGH3-pIRES2-EGFP组细胞凋亡率达到19.46%±0.08%.差异有统计学意义(F=175 261.23,p<0.01).透射电镜下可见转染组细胞核内染色质凝集,固缩,分布于核膜下,核仁消失,有的胞核碎裂,细胞呈典型的凋亡改变.转染R555W-BIGH3-pIRES2-EGFP组caspase-3活性为561.03 ±1.05,与其他组相比,差异有统计学意义(F=629 347.38,P<0.01).结论 应用快速体外定点诱变技术,成功获得突变型R555W-BIGH3基因,转染人角膜上皮细胞后,通过caspase3途径引起细胞凋亡.     

Induction of apoptosis in human corneal and HeLa cells by mutated BIGH3

PURPOSE: To determine the effects of overexpression of mutated BIGH3 in HeLa and human corneal epithelial (HCE) cells. METHODS: Six mutations known to be responsible for autosomal dominant corneal dystrophies linked to chromosome 5 were generated in a BIGH3 expression vector and transfected in HeLa and HCE cells. The expression and secretion of the various BIGH3-EGFP fusion proteins were measured by Western blot analysis. Apoptotic cells were identified by Hoechst/propidium iodide and annexin V staining. Lactate dehydrogenase (LDH) activity was measured in the medium of transfected cells. Truncated BIGH3 protein and site-specific mutations were generated to determine the exact region that mediated apoptosis. RESULT: The overexpressed BIGH3 fusion protein was secreted regardless of its mutation status and was clearly observed in the culture medium. Overexpression of mutated BIGH3 induced apoptosis in both cell lines through activation of caspase-3. Although all the disease-causing mutations tested in this experiment induced apoptosis, the strongest effect was observed with the R124C and R555W mutations. Overexpression of a carboxyl-truncated BIGH3 protein did not induce apoptosis, suggesting that a region located in the C-terminal domain was necessary to mediate cell death. In addition, mutation of the Pro-Asp-Ile (PDI) site at 616-618 was sufficient to prevent induction of apoptosis. CONCLUSIONS: Overexpression of mutated BIGH3 induces apoptosis in HeLa and HCE cells through activation of a pathway that uses the PDI domain of the fourth internal Fas domain and activation of caspase-3. Because DI is a known site of interaction with alpha 3 beta 1 integrins, it suggests that integrins play a role in mediating apoptosis in the system used in the current study. This work suggests that apoptosis is a key element in the pathophysiology of BIGH3-related corneal dystrophies.     

The functions of exogenous and endogenous laminin-5 on corneal epithelial cells

Recent evidence suggests that the basement membrane not only separates basal cells from Bowman's layer, but also has a crucial role in the proliferation, differentiation and migration of corneal epithelial cells. The basement membrane is composed of a mixture of matrix components including collagens, laminins and heparan sulfate proteoglycans. In these extracellular matrixes, laminin is a major component of the basement membrane. Of 11 laminin isoformes, laminin-5 is a variant, composed of three nonidentical subunits alpha3, beta3, gamma2 and is a major component of the corneal basement membrane. However, little is known about the interactions of laminin-5 with corneal epithelial cells. In this study, we investigated the functions of laminin-5 on SV-40 transfected human corneal epithelial cells (HCE cells). We also revealed different functions between exogenous and endogenous laminin-5 on HCE cells. Laminin-5 is synthesized initially as a 490 kDa molecule that undergoes specific processing to cleavaged isoforms after being secreted. The alpha3 subunit is processed from 200-190 kDa to 160 kDa/145 kDa. The gamma2 subunit is processed from 150 kDa to 105 kDa/80 kDa. The beta3 subunit (140 kDa) is not processed. Exogenously added laminin-5 (soluble form) in this study was purified from a serum-free, conditioned medium of a human gastric carcinoma cell line STKM-I. This soluble laminin is a processed isoform containing alpha3 (160 kDa), beta3 (140 kDa) and gamma2 (105 kDa) chains. On the other hand, immunocytochemical analysis showed that HCE cells themselves secreted laminin-5 endogenously. Western blotting analysis revealed that HCE cells initially produced unprocessed isoform containing 190 kDa alpha3, 140 kDa beta3 and 150 kDa gamma2 chains and that after being secreted, the alpha3 chain was processed to 160 kDa/145 kDa and the gamma2 chain was processed to 105 kDa.Initially we investigated the functions of exogenous (processed) laminin-5 on HCE cells. Exogenously added laminin-5 strongly promoted cell adhesion via alpha3beta1 integrin, cell spreading, assembly of hemidesmosomes and mildly inhibited cell migration. Next we estimated the effect of endogenous (unprocessed) laminin-5 on HCE cells. Using an anti laminin-5 monoclonal antibody (mAb) or anti integrin alpha3beta1 mAbs, the blocking of the interaction between endogenously secreted laminin-5 and HCE cells caused strong inhibition of cell migration. Integrin alpha3beta1 and alpha6beta4 were expressed in HCE cells. These integrins are receptors of laminin-5. But, anti integrin alpha6beta4 mAbs did not have any blocking ability against cell migration. These results indicated that endogenous (unprocessed) laminin-5 has a crucial role in cell migration on HCE cells via alpha3beta1 integrin.In conclusion, structural differences between exogenous (processed) and endogenous (unprocessed) laminin-5 regulated their functions on HCE cells. Exogenously added laminin-5 strongly promoted cell adhesion, cell spreading and assembly of hemidesmosomes. Endogenously secreted laminin-5 had a crucial role in cell migration. In the future, processed soluble laminin-5 could be a useful drug for the prevention of recurrent corneal erosion, and unprocessed soluble laminin-5 could be applied for the treatment of prolonged corneal epithelial defects.     

Cooperation of isoforms of laminin-332 and tenascin-CL during early adhesion and spreading of immortalized human corneal epithelial cells

The repair of corneal wounds requires both epithelial cell adhesion and migration. We have studied the early adhesion process of immortalized human corneal epithelial (HCE) cells and show by field emission scanning electron microscopy (FESEM) that the cells first adhere via foot-like process to the growth substratum and later present lamellar spreading. During early adhesion indirect immunofluorescence showed that the cells codeposited laminin (Lm) -332 and the large subunit of tenascin-C (Tn-CL) as a demarcated plaque beneath the cells. Instead, unprocessed Lm-332 (alpha 3'32) was found in a wider area in cells showing lamellar spreading and was also prominently expressed in the cytoplasm of the migrating marginal cells in the in vitro wounded HCE cultures. Confocal laser scanning microscopy (CLSM) showed that the Golgi apparatus was located to the vicinity of the Lm-332/Tn-CL-containing adhesion plaque and accordingly treatment of the cells with demecolcine, dispersing the Golgi apparatus, prevented the formation of plaques. This suggests that formation of the adhesion plaque depends on a direct vectorial secretion of Lm-332 and Tn-CL to the culture substratum. Instead, cytochalasin B treatment disrupted microfilaments and arborized the cells but did not affect the deposition of Tn-CL/Lm-332 as a plaque beneath the cells. The suggestion was supported by immunoprecipitation experiments which showed that Tn-CL and Lm alpha 3' chain were found in cell-free matrices on the culture substratum of spreading cells but not at all (Tn-CL) or much less (Lm-332) in the culture medium. Quantitative cell adhesion experiments showed that HCE cells did not adhere to plain Tn-C coat and that integrin (Int) alpha(3)beta(1) mediated the adhesion of HCE cells to purified Lm-332 and to Lm-332/Tn-C while Int beta4 did not mediate adhesion to these proteins. Taken together, our data suggest that Lm-332 and Tn-CL cooperate in early adhesion process of HCE cells. Furthermore, the results show that Lm-3'32 isoform functions in the spreading of the cells beyond the early adhesion stage and appears to emerge into HCE cells starting to migrate in experimental wounds.     

Intercellular adhesion molecule-1 expression on human corneal epithelial outgrowth from limbal explant in culture

AIM: To investigate the relation between intercellular adhesion molecule (ICAM)-1 expression and cellular dynamics occurring concomitantly with epithelial cell movement. METHODS: Outgrowing epithelial sheets of human corneal epithelial (HCE) cells from cultured limbal explants were examined by immunoperoxidase staining with anti-ICAM-1 monoclonal antibody. An adhesion assay was performed using the epithelial sheets of HCE cells and an Epstein-Barr virus (EVB) infected B cell lymphoma cell line (EVB(+)BJAB) expressing CD11a/CD18, a counter-receptor of ICAM-1. Also, the effect of calphostin C, a specific protein kinase C (PKC) inhibitor, on ICAM-1 expression on the outgrowing epithelial sheets of HCE cells was examined. RESULTS: Strong positive staining for ICAM-1 was found predominantly on HCE cells in the marginal segment of the epithelial sheet, particularly on the cells at the leading edge. EBV(+)BJAB cells adhering to the HCE cells corresponded well to the area of ICAM-1 staining. Treatment of outgrowing epithelial sheets with calphostin C markedly decreased the ICAM-1 expression on the HCE cells. CONCLUSION: ICAM-1 is actively expressed on HCE cells in the marginal segment of the outgrowing epithelial sheets where there is active movement mediated through a PKC dependent mechanism, suggesting the role of ICAM-1 in epithelial cell motility such as the spreading and migration of cells.     

Inhibition of experimental choroidal neovascularization in rats by an alpha(v)-integrin antagonist

PURPOSE: Integrin alpha(v)beta3 is predominantly expressed on endothelial cells in choroidal neovascularization (CNV). We evaluated the efficacy of cyclic RGD (Arg-Gly-Asp) peptide, an alpha(v)-integrin antagonist, in a rat model of laser-induced CNV METHODS: We evaluated the effect of cyclic RGD on the adhesion and cell viability of bovine choroidal endothelial cells (BCECs) by cell counting and the trypan blue dye exclusion test. CNV was induced by laser photocoagulation in female Long Evans rats (day 0), followed by intravitreal administration of one dose of cyclic RGD of 200 (n = 9), 100 (n = 10), 50 (n = 4), or 0 microg (n = 9) on days 9 and 11. We assessed the area of CNV by fluorescein angiography and the thickness microscopically on histologic sections. Neovascular vessels were detected by an antibody against factor VIII. RESULTS: Cyclic RGD (0.02 to 200 microg/ml) inhibited adhesion of BCECs in a dose-dependent manner without changing the cell viability (p < 0.01). In eyes treated with two injections of 200 or 100 microg of cyclic RGD peptide, the development of CNV was significantly (p < 0.01) inhibited in the area of leakage on fluorescein angiography. Histologically, the CNV membrane was observed beneath the retina and the factor VIII-positive cells and red blood cells were involved. The thickness of the lesions was significantly (p < 0.01) reduced in eyes that received 200 or 100 microg of RGD. CONCLUSIONS: Cyclic RGD effectively inhibited CNV progression in a rat model of laser-induced CNV, suggesting that this alpha(v)-integrin antagonist may be beneficial in the treatment of CNV.     

In vitro bovine and human lens epithelial cell culture studies on inhibition of posterior capsule opacification using a cyclic RGD peptide

BACKGROUND: RGD peptides competitively inihibit adhesion molecules of the lens epithelial cells (LEC). The purpose of our study was to investigate whether this peptide is capable of detaching adherent cells and preventing posterior capsule opacification (PCO). METHODS: Cultures of bovine and human LECs on culture dishes and discs of bovine anterior lens capsules were used. The inhibition of adhesion and the detachment of confluent LEC layers by the cyclic RGD peptide cRGDdFV were studied (incubation time was 3 days and 1 h and concentrations of 10(-4) and 10(-3) M were used). RESULTS: A dose-dependent inhibition of adhesion (48% and 42%, respectively) was obtained. There was a significant difference between the control peptide group and cRGDdFV (p < 0.0001). Cell detachment from lens capsules was not achieved but complete detachment from the culture dish occurred after 37 min. CONCLUSIONS: Short-term incubation of LECs by cRGDdFV did not lead to a sufficient inhibition of adhesion in vitro. A detachment of adherent LECs by cRGDdFV was not achieved.     

Inhibitory effects of Arg-Gly-Asp (RGD) peptide on cell attachment and migration in a human lens epithelial cell line

Posterior capsule opacification (PCO) after cataract surgery is caused by growth of residual human lens epithelial (HLE) cells on the posterior capsule. We have shown that extracellular matrix (ECM) is an essential factor for HLE cell attachment and migration. The purpose of this study was to examine the inhibitory effects of Arg-Gly-Asp (RGD) peptide on cell attachment and migration in an HLE cell line. HLE cell line cells (SRA 01/04) that were obtained by transfection of large T antigen of SV40 were cultured in the absence of serum. The culture dishes were coated with type IV collagen, laminin or fibronectin, and Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) RGD peptide (0.1, 0.3, 1.0, 2.0 mg/ml) was added to the medium. The number of attached cells was counted after 90 min of incubation, and the inhibitory effects of GRGDSP RGD peptide on cell attachment were calculated. Cell attachment on the fibronectin-coated dishes was inhibited by GRGDSP RGD peptide at concentrations higher than 0.3 mg/ml; the inhibitory rate was 80% at a concentration of 2.0 mg/ml. The inhibition of cell attachment by GRGDSP RGD peptide on laminin-coated dishes appeared only at a concentration of 2.0 mg/ml, whereas no effects were observed on the type IV collagen-coated dishes. The inhibitory effects of GRGDSP RGD peptide on cell migration were measured in medium containing 2.0 mg/ml of GRGDSP RGD peptide after 1, 3, 5 and 7 days of culture. Cell migration was inhibited by GRGDSP RGD peptide from 1 day of culture on the fibronectin-coated dishes and from 5 days of culture on the laminin-coated dishes, whereas no effects were observed on the type IV collagen-coated dishes. GRGDSP RGD peptide inhibited cell attachment and migration on laminin and fibronectin that have RGD sequences. These data suggested that RGD peptide may have the potential to prevent PCO.     

Granulocyte macrophage colony-stimulating factor expression in human herpetic stromal keratitis: implications for the role of neutrophils in HSK

PURPOSE: Granulocyte macrophage colony-stimulating factor (GM-CSF) is thought to play a key role in chronic inflammatory diseases by governing the survival and function of infiltrating neutrophils. The objective of this study was to determine the putative role of GM-CSF in the pathogenesis of human herpetic stromal keratitis (HSK). METHODS: Primary human corneal fibroblast (HCF) cultures and a telomerase-immortalized human corneal epithelial (HCE) cell line representative of native HCE were stimulated with the known HSK-inducing cytokines interferon (IFN)-gamma, interleukin (IL)-1beta, and tumor necrosis factor (TNF)-alpha. Alternatively, the T-cell cytokine IL-17 was added solely or simultaneously. Human neutrophils were incubated with conditioned medium (CM) of the HCF and HCE stimulated with the aforementioned cytokines, or recombinant GM-CSF, and their viability or activation status was determined by flow cytometry. GM-CSF and IL-8 secretion levels in the CM were determined by ELISA. The antibody-dependent cellular cytotoxicity (ADCC) of neutrophils toward herpes simplex virus (HSV)-infected HCFs was determined by flow cytometry. The expression of GM-CSF was determined in HSK and control corneal buttons by real-time RT-PCR and immunohistology. RESULTS: Compared with IFN-gamma, CM of either cell type stimulated with IL-1beta, or in the case of HCE cells, stimulated with TNF-alpha or IL-17, delayed neutrophil apoptosis significantly. Only in HCFs did IL-17 exhibit a synergistic effect with TNF-alpha. The antiapoptotic activity was attributable in part to the GM-CSF secreted by the activated HCFs and HCE cells. GM-CSF stimulation of neutrophils induced their activation and the secretion of IL-8. GM-CSF did not increase significantly the ADCC reaction of neutrophils toward HSV-infected HCFs. Finally, GM-CSF was expressed in corneas of the patients with HSK but not in control subjects. CONCLUSIONS: The data suggest that GM-CSF, expressed by cornea-resident cells such as HCFs and HCE cells, may play a role in the immunopathogenesis of HSK by prolonging the survival and modulating the effector function of corneal infiltrating neutrophils.     

Promotion of adhesion and migration of RPE cells to provisional extracellular matrices by TNF-alpha

PURPOSE: Adhesion and migration of retinal pigment epithelial (RPE) cells to provisional extracellular matrices (ECM) is important in the development of epiretinal membranes found in proliferative vitreoretinopathy (PVR). Tumor necrosis factor alpha (TNF-alpha) is found in PVR membranes and regulates many functions of RPE cells. In this study, the effects of TNF-alpha on adhesion and migration of RPE cells to various components of ECM were examined and elucidation of the mechanism of the response was attempted. METHODS: Mitogen activated protein kinase (ERK1/2; MAPK) activation was measured by immunoblot. RPE cells pretreated with TNF-alpha (10 ng/ml) or TNF-alpha + PD98059 (a specific inhibitor of MAPK, 30 microM) for 24 hours were compared with control RPE. Attachment was measured by modified MTT assay on fibronectin and collagen types I and IV. Spreading was measured by staining with fluo3-AM and confocal laser scanning microscopy. Migration of RPE cells on substrates was determined by Boyden chamber assay using PDGF-BB (20 ng/ml) as a chemotactic factor. Integrin expression was determined by flow cytometry and RT-PCR. RESULTS: TNF-alpha rapidly activated MAPK and increased the extent of attachment, spreading and migration on fibronectin and collagen type I (P < 0.01) but not on collagen type IV. TNF-stimulated RPE cells showed increased mRNA and surface protein expression for alpha1 and alpha5 integrin (P < 0.01) but not alpha3 integrin subunit. Neutralizing the anti-alpha1 antibody inhibited migration on collagen type I, whereas alpha5 antibody inhibited fibronectin-induced migration. Treatment with both TNF and PD98095 reduced attachment and migration on provisional ECM and reduced the upregulated integrin expression to control levels. CONCLUSIONS: After treatment with TNF-alpha, there is increased expression of specific integrins associated with increased adhesion and migration on provisional ECM (fibronectin and collagen type I). This effect is mediated, at least in part, by activation of MAPK signaling pathway.     

Advanced glycation of fibronectin impairs vascular repair by endothelial progenitor cells: implications for vasodegeneration in diabetic retinopathy

PURPOSE: Vascular repair by marrow-derived endothelial progenitor cells (EPCs) is impaired during diabetes, although the precise mechanism of this dysfunction remains unknown. The hypothesis for the study was that progressive basement membrane (BM) modification by advanced glycation end products (AGEs) contributes to impairment of EPC reparative function after diabetes-related endothelial injury. METHODS: EPCs isolated from peripheral blood were characterized by immunocytochemistry and flow cytometry. EPC interactions on native or AGE-modified fibronectin (AGE-FN) were studied for attachment and spreading, whereas chemotaxis to SDF-1 was assessed with the Dunn chamber assay. In addition, photoreactive agent-treated monolayers of retinal microvascular endothelial cells (RMECs) produced circumscribed areas of apoptosis and the ability of EPCs to "endothelialize" these wounds was evaluated. RESULTS: EPC attachment and spreading on AGE-FN was reduced compared with control cells (P < 0.05-0.01) but was significantly restored by pretreatment with Arg-Gly-Asp (RGD). Chemotaxis of EPCs was abolished on AGE-FN but was reversed by treatment with exogenous RGD. On wounded RMEC monolayers, EPCs showed clustering at the wound site, compared with untreated regions (P < 0.001); AGE-FN significantly reduced this targeting response (P < 0.05). RGD supplementation enhanced EPC incorporation in the monolayer, as determined by EPC participation in tight junction formation and restoration of transendothelial electric resistance (TEER). CONCLUSIONS: AGE-modification of vascular substrates impairs EPC adhesion, spreading, and migration; and alteration of the RGD integrin recognition motif plays a key role in these responses. The presence of AGE adducts on BM compromises repair by EPC with implications for vasodegeneration during diabetic microvasculopathy.     

Thymosin beta4 promotes human conjunctival epithelial cell migration

PURPOSE: In this study the effects of thymosin beta4 (Tbeta4) on migration and production of laminin-5 in the human conjunctival cell line HC0597 was analyzed. METHODS: Boyden chamber assays assessed the ability of Tbeta4 to stimulate in vitro cell migration. Control or Tbeta4-treated cells were processed for immunofluorescence microscopy using antibodies to vinculin or laminin-5. Cell lysates were processed for Western blot and densitometric analysis using antibodies to laminin-5 alpha3 or gamma2 chains. RESULTS: Tbeta4 stimulated migration in a dose-dependent manner. Focal adhesions present in Tbeta4-treated cells were smaller and more rounded compared to the "streaks" characteristic of controls. Western blot analysis and densitometry revealed that Tbeta4-treated cells expressed more laminin-5 alpha3 and gamma2 chain protein. CONCLUSION: Tbeta4 stimulates in vitro conjunctival epithelial cell migration, and results in altered focal adhesion formation and increased extracellular laminin-5 deposition. The increased migration may be correlated with increased production of laminin-5.     

A distinct integrin-mediated phagocytic pathway for extracellular matrix remodeling by RPE cells.

PURPOSE: To characterize the phagocytosis of extracellular matrix components by retinal pigment epithelial cells and to determine which receptors and signal transduction pathways are involved. METHODS: Fluorescent latex beads were coated with fibronectin (FN), collagen type I or IV, or thrombospondin and incubated with human retinal pigment epithelial cells for 3 hours. Phagocytosis was quantified by flow cytometry. The effects of adhesion blocking antibodies to cell surface receptors (alpha1, alpha3, alpha5, beta1, alpha5beta1, alphavbeta3, alphavbeta5 integrins and CD36) and inhibitors of specific intracellular signaling pathways (tyrosine kinase phosphatidylinositol 3-kinase [PI3-kinase], protein kinase C [PKC], and mitogen-activated protein kinase) were determined using FN-coated beads. RESULTS: Phagocytosis of FN-coated beads was greater than phagocytosis of beads coated with collagen type I, collagen type IV, or thrombospondin or uncoated controls (P < 0.0005). Anti-alpha5, -beta1, and -alpha5beta1 antibodies markedly inhibited FN phagocytosis (P < 0.0005); the inhibitory effects of anti-alpha5 antibody were stronger in the initial stages (binding) than in the later stages (internalization) of phagocytosis. There was no significant effect on phagocytosis when anti-alpha1, -alpha3, -alphavbeta5, -alphavbeta3 or -CD36 antibodies were used. Fibronectin phagocytosis was decreased by inhibitors of tyrosine kinase (genistein, 100 microg/ml, P < 0.005) and PI3-kinase (wortmannin, 5 microM, P < 0.01), but these reagents did not affect the uncoated controls. The PKC inhibitor calphostin C (400 nM) nonspecifically increased the phagocytosis of FN-coated (P < 0.05) and uncoated beads (P < 0.01). CONCLUSIONS: Subconfluent retinal pigment epithelial cells preferentially phagocytose FN over other extracellular matrix components. Phagocytosis of FN utilizes the alpha5beta1 integrin, is mediated in part through tyrosine kinase and PI3-kinase signaling pathways, and is modulated by PKC. Phagocytosis of extracellular matrix by retinal pigment epithelial cells may represent a novel mechanism for remodeling of the provisional extracellular matrix during outer retinal wound healing.     

Role of Rac1 in fibronectin-induced adhesion and motility of human corneal epithelial cells

PURPOSE: The fibronectin-integrin system plays an important role in adhesion and migration of corneal epithelial cells and thereby contributes to epithelial wound healing. The role of Rac1, a member of the Rho family of GTPases, in the intracellular signaling responsible for regulation of the adhesion and motility of corneal epithelial cells by fibronectin was examined. METHODS: Simian virus 40-transformed human corneal epithelial (HCE) cells were plated on fibronectin or on bovine serum albumin as a control. Cell motility was monitored by time-lapse video microscopy. The actin cytoskeleton and focal adhesions were detected by staining of cells with rhodamine-phalloidin and antibodies to phosphotyrosine, respectively. The activation of Rac1 and phosphorylation of its effector PAK were evaluated with a pull-down assay and immunoblot analysis, respectively. The effects of mutant forms of Rac1 were determined by cell transfection. RESULTS: HCE cells plated on fibronectin manifested greater levels of cell adhesion and motility than did those plated on bovine serum albumin. Fibronectin also induced the accumulation of F-actin and the formation of focal adhesions at the cell periphery as well as the activation of Rac1 and the phosphorylation of PAK. Expression of the dominant negative mutant Asn17Rac1 inhibited the effects of fibronectin on cell adhesion and motility, the actin cytoskeleton, and focal adhesions. Expression of the constitutive active mutant Val12Rac1 mimicked the effects of fibronectin on F-actin and focal adhesions. CONCLUSIONS: Rac1 is necessary for the promotion of HCE cell adhesion and motility by fibronectin. It therefore probably plays an important role in corneal wound healing.