Dexamethasone and MicroRNA-204 Inhibit Corneal Neovascularization

INTRODUCTION

This was an in vivo animal study designed to investigate the interaction between dexamethasone (Dex) and microRNA-204 (miR-204) in a mouse alkali burn-induced corneal neovascularization (CNV) model. The function of miR-204 was then investigated in human mammary epithelial cells (HMECs) in vitro.

MATERIALS AND METHODS

The CNV model was induced by corneal alkali burn in BLAB/c mice. The mice were randomly divided into five groups: normal control (Ctrl), alkali burn-induced corneal injury (Alkali), alkali burn + Dex (Dex), alkali burn + negative control (NTC), and alkali burn + miR-204 agomir (miR-204). Subconjunctival injection of NTC, Dex, or miR-204 agomir was conducted at 0, 3, and 6 days, respectively, after alkali burn. The corneas were collected at day 7 after injury, and the CNV area was observed using immunofluorescence staining. The expression of miR-204 was analyzed with quantitative real time (qRT)-PCR. In HMECs, exogenous miR-204 agomir or antagomir was used to strengthen or inhibit the expression of miR-204. Migration assays and tube formation studies were conducted to evaluate the function of miR-204 on HMECs.

RESULTS

At 7 days post-alkali burn, CNV grew aggressively into the cornea. MicroRNA-204 expression was reduced in the Alkali group in contrast with the Ctrl group (P = .003). However, miR-204 was upregulated in the Dex group (vs. alkali group, P = .008). The CNV areas in the NTC and miR-204 groups were 59.30 ± 8.32% and 25.60 ± 2.30%, respectively (P = .002). In vitro, miR-204 agomir showed obvious inhibition on HMEC migration in contrast with NTC (P = .033) and miR-204 antagomir (P = .017). Compared with NTC, miR-204 agomir attenuated tube formation, while miR-204 antagomir accelerated HMEC tube formation (P < .05).

CONCLUSION

The role of Dex in attenuating CNV may be partly attributed to miR-204. MiR-204 may be a potential therapeutic target in alkali burn-induced CNV.

Predicting clinical outcome of sulfur mustard induced ocular injury using machine learning model

The sight-threatening sulfur mustard (SM) induced ocular injury presents specific symptoms in each clinical stage. The acute injury develops in all exposed eyes and may heal or deteriorate into chronic late pathology. Early detection of eyes at risk of developing late pathology may assist in providing unique monitoring and specific treatments only to relevant cases. In this study, we evaluated a machine-learning (ML) model for predicting the development of SM-induced late pathology based on clinical data of the acute phase in the rabbit model. Clinical data from 166 rabbit eyes exposed to SM vapor was used retrospectively. The data included a comprehensive clinical evaluation of the cornea, eyelids and conjunctiva using a semi-quantitative clinical score. A random forest classifier ML model, was trained to predict the development of corneal neovascularization four weeks post-ocular exposure to SM vapor using clinical scores recorded three weeks earlier. The overall accuracy in predicting the clinical outcome of SM-induced ocular injury was 73%. The accuracy in identifying eyes at risk of developing corneal neovascularization and future healed eyes was 75% and 59%, respectively. The most important parameters for accurate prediction were conjunctival secretion and corneal opacity at 1w and corneal erosions at 72 h post-exposure. Predicting the clinical outcome of SM-induced ocular injury based on the acute injury parameters using ML is demonstrated for the first time. Although the prediction accuracy was limited, probably due to the small dataset, it pointed out towards various parameters during the acute injury that are important for predicting SM-induced late pathology and revealing possible pathological mechanisms.

The Possible Protective Effect of Boric Acid in an Alkaline-Induced Corneal Neovascularization Rat Model

It is known that boric acid (BA) exerts it antioxidant and anti-inflammatory effects by activating the activating transcription factor 4 (ATF4) and nuclear factor-erythroid 2-related factor 2 (Nrf2) pathway. This pathway has been reported to control antioxidant status in the eye. The aim of this study was to investigate the possible preventive effects of boric acid administration on oxidative damage and corneal neovascularization (CNV). Sixteen adult female Wistar albino rats were divided into two groups: (I) control (n = 8); the CNV model was applied to the right eye of the rats, and the left eyes were used as healthy controls. (II) CNV + BA (n = 8): After the CNV model was applied to the right eyes, a single subconjunctival dose (0.05 mL) of 0,018 g/mL BA was injected into the right and left eyes of the rats. Biochemical, histopathological, and immunohistochemical analyses were performed. Moderate VEGF positivity was observed in the vessels of the CNV group, a decrease in vessel proliferation, and weak VEGF positivity in the CNV + BA group. The TAS level in the CNV + BA group was significantly higher than that in the other groups. The TOS level was significantly higher in all groups than it is in the control group. The OSI value was increased in all groups when compared to the control group, but only the CNV and BA groups were statistically significant. BA not only reduced alkaline-induced corneal damage histologically but also showed a protective effect on oxidative stress biochemically.

B-cell leukemia/lymphoma 10 promotes angiogenesis in an experimental corneal neovascularization model

PURPOSE

Corneal neovascularization (CrNV) arises from many causes including corneal inflammatory, infectious, or traumatic insult, and frequently leads to impaired vision. This study seeks to determine the role of B-cell leukemia/lymphoma 10 (BCL-10) in the development of experimental CrNV.

METHODS

Corneas from BCL-10 knockout (KO) mice and wild-type (WT) mice were burned by sodium hydroxide (NaOH) to create the CrNV model and neovascular formation in the corneas was assessed 2 weeks later. Intracorneal macrophage accumulation and the expression of angiogenic factors were quantified by flow cytometric analysis (FCM) and real-time PCR, respectively.

RESULTS

The amount of CrNV was determined 2 weeks after alkali burn. Compared to WT mice, the amount of CrNV in BCL-10 KO mice was significantly decreased. FCM revealed that F4/80-positive macrophages were markedly decreased in BCL-10 KO mice compared with WT mice. Reverse transcription PCR showed that the mRNA expression levels of intracorneal vascular endothelial growth factor-A (VEGF-A), basic fibroblast growth factor (bFGF) and monocyte chemotactic protein 1 were reduced in BCL-10 KO mice compared with WT mice.

CONCLUSION

BCL-10 KO mice exhibited reduced alkali-induced CrNV by suppressing intracorneal macrophage infiltration, which subsequently led to decreased VEGF-A and bFGF expression, suggesting that BCL-10 may become a potential clinical intervening target of CrNV.

Histopathological and Molecular Changes in the Rabbit Cornea From Arsenical Vesicant Lewisite Exposure

Lewisite (LEW), a potent arsenical vesicating chemical warfare agent, poses a continuous risk of accidental exposure in addition to its feared use as a terrorist weapon. Ocular tissue is exquisitely sensitive to LEW and exposure can cause devastating corneal lesions. However, detailed pathogenesis of corneal injury and related mechanisms from LEW exposure that could help identify targeted therapies are not available. Using an established consistent and efficient exposure system, we evaluated the pathophysiology of the corneal injury in New Zealand white rabbits following LEW vapor exposure (at 0.2 mg/L dose) for 2.5 and 7.5 min, for up to 28 day post-exposure. LEW led to an increase in total corneal thickness starting at day 1 post-exposure and epithelial degradation starting at day 3 post-exposure, with maximal effect at day 7 postexposure followed by recovery at later time points. LEW also led to an increase in the number of blood vessels and inflammatory cells but a decrease in keratocytes with optimal effects at day 7 postexposure. A significant increase in epithelial-stromal separation was observed at days 7 and 14 post 7.5 min LEW exposure. LEW also caused an increase in the expression levels of cyclooxygenase-2, IL-8, vascular endothelial growth factor, and matrix metalloproteinase-9 at all the study time points indicating their involvement in LEW-induced inflammation, vesication, and neovascularization. The outcomes here provide valuable LEW-induced corneal injury endpoints at both lower and higher exposure durations in a relevant model system, which will be helpful to identify and screen therapies against LEW-induced corneal injury.

Therapeutic effects of a novel PIGF-1 derived peptide, ZY-1, on corneal neovascularization in vitro and in vivo

Corneal neovascularization (NV) is one of the major sight-threatening pathological changes caused by corneal diseases. Current therapeutics generate various adverse effects. Small peptides derived from endogenous protein display certain advantages. This study aims to evaluate the anti-angiogenic effect and molecular mechanism of a novel peptide ZY-1, derived from placental growth factor-1 (PlGF-1), on corneal NV by topical administration, and to investigate its safety profile after long-term treatment. CCK-8 assay and tube formation assay were used to evaluate the effect of ZY-1 on human umbilical vein endothelial cells (HUVECs). The anti-angiogenic effect of topical ZY-1 was estimated in a rat model of alkali burn induced corneal NV. The safety profile of topical ZY-1 was analyzed by CCK-8 assay, tear film break-up time (BUT), and histological examination. Firstly, we found that ZY-1 co-localized with membrane vascular epithelial growth factor receptor-1 (VEGFR-1) and effectively inhibited VEGF/PlGF-1 induced proliferation and tube formation of HUVECs. The topical ZY-1 administration efficiently inhibited alkali-burn induced corneal NV, while it did not show any significant effect on human corneal epithelial cell (HCEC) proliferation, as well as the functionality and morphology of cornea and conjunctiva. Our findings suggested that topical administration of ZY-1 could effectively and safely inhibit corneal NV partially through competing for VEGFR-1 binding, and it would be a promising alternative for ocular topical anti-angiogenic therapy.

Transient downregulation of microRNA-206 protects alkali burn injury in mouse cornea by regulating connexin 43

PURPOSE

Chemical burn in cornea may cause permanent visual problem or complete blindness. In the present study, we investigated the role of microRNA 206 (miR-206) in relieving chemical burn in mouse cornea.

METHOD

An alkali burn model was established in C57BL/6 mice to induce chemical corneal injury. Within 72 hours, the transient inflammatory responses in alkali-treated corneas were measured by opacity and corneal neovascularization (CNV) levels, and the gene expression profile of miR-206 was measured by quantitative real-time PCR (qPCR). Inhibitory oligonucleotides of miR-206, miR-206-I, were intrastromally injected into alkali-burned corneas. The possible protective effects of down-regulating miR-206 were assessed by both in vivo measurements of inflammatory responses and in vitro histochemical examinations of corneal epithelium sections. The possible binding of miR-206 on its molecular target, connexin43 (Cx43), was assessed by luciferase reporter (LR) and western blot (WB) assays. Cx43 was silenced by siRNA to examine its effect on regulating miR-206 modulation in alkali-burned cornea.

RESULTS

Opacity and CNV levels, along with gene expression of miR-206, were all transiently elevated within 72 hours of alkali-burned mouse cornea. Intrastromal injection of miR-206-I into alkali-burned cornea down-regulated miR-206 and ameliorated inflammatory responses both in vivo and in vitro. LR and WB assays confirmed that Cx43 was directly targeted by miR-206 in mouse cornea. Genetic silencing of Cx43 reversed the protective effect of miR-206 down-regulation in alkali-burned cornea.

CONCLUSION

miR-206, associated with Cx43, is a novel molecular modulator in alkali burn in mouse cornea.

[Inhibited experimental mouse corneal neovascularization by CCR3 antagonist]

OBJECTIVE

To explore the effect of CCR3 antagonist on the development of experimental corneal neovascularization.

METHODS

Mouse corneas were burned by NaOH to induce corneal neovascularization.Fifty four clean male BABL/c mice aged 7-8 weeks were divided into control group, CCR3 antagonist group and VEGF antibody positive group according to randomized number table. The gene expression of CCR3 and its ligand eotaxin in burned corneas was examined by Real-time PCR. CCR3 antagonist was locally administrated after alkali injury and the formation of corneal neovascular 2 weeks after injury was examined using a digital camera linked to a slit lamp microscope and corneal whole mount staining with CD31. The mRNA and protein expression of chemokines in burned corneas was detected by Real-time PCR and western blot.

RESULTS

Compared to control group, CCR3 antagonist treated mice resulted in significantly decreased corneal neovascularization. The related CNV area was 0.51 ± 0.03 in the CCR3 antagonist group, and that in the control group was 0.77 ± 0.15, with significant difference between them (t = 12.91, P = 0.00).Western blot detection did not show significant difference of VEGF protein expression between two groups.Expression level of VEGF in the CCR3 antagonist group was 0.91 ± 0.24, and that in the control group was 1.15 ± 0.30, showing no significant difference (t = 1.08, P = 0.34).

CONCLUSIONS

Alkali-induced corneal neovascularization was inhibited by CCR3 antagonist. The mechanism that CCR3 pathway plays an important role in corneal neovascularization needs further exploration.

7-Ketocholesterol induces inflammation and angiogenesis in vivo: a novel rat model

Accumulation of 7-Ketocholesterol (7KCh) in lipid deposits has been implicated in a variety of chronic diseases including atherosclerosis, Alzheimer's disease and age-related macular degeneration. 7KCh is known to be pro-inflammatory and cytotoxic to various types of cultured cells but little is known about its effects in vivo. In this study we have investigated the effects of 7KCh in vivo by implanting biodegradable wafers into the anterior chamber of the rat eye. The wafers were prepared using a mixture of two biodegradable polymers with different amounts of 7KCh. The 7KCh-containing implants induced massive angiogenesis and inflammation. By contrast, no angiogenesis and very little inflammation were observed with cholesterol-containing implants. The neovessel growth was monitored by fluorescein angiography. Neovessels were observed 4 days post implantation and peaked between 7 to 10 days. The angiography and isolectin IB(4) labeling demonstrated that the neovessels originated from the limbus and grew through the cornea. Immunolabeling with anti-CD68 suggested that the 7KCh-containing implants had extensive macrophage infiltration as well as other cell types. A significant increase in VEGF was also observed in 7KCh-containing implants by fluorescent immunolabeling and by immunoblot of the aqueous humor (AH). Direct measurement of VEGF, IL-1β and GRO/KC demonstrated a marked elevation of these factors in the AH of the 7KCh-implants. In summary this study demonstrates two important things: 1) 7KCh is pro-angiogenic and pro-inflammatory in vivo and 2) implants containing 7KCh may be used to create a novel angiogenesis model in rats.

Use of amphoteric rinsing solution for treatment of ocular tissues exposed to nitrogen mustard

PURPOSE

Ocular exposure to mustard agents may cause severe and prolonged injury to the anterior segment tissues. Effective decontamination of the external eye surface after exposure is of paramount importance. The purpose of the present study was to assess the effectiveness of Diphoterine rinsing solution (DRS) in reducing ocular damage after exposure to nitrogen mustard (NM) and to compare it with normal saline solution.

METHODS

One eye of 16 New Zealand albino rabbits was exposed to 2% NM. Immediate thorough irrigation was performed with either 500 ml of DRS (treated group) or with 500 ml of normal saline (control group). The magnitude of ocular injury and response to treatment were assessed by examiners masked to the treatment assignment during 22 days following the exposure.

RESULTS

Immediate ocular irrigation with DRS was more effective compared with saline in reducing corneal, iris and anterior chamber injury. In the DRS-treated group, the corneal opacity and corneal neovascularization were less severe, and development of iris atrophy was delayed. Intraocular pressure (mmHg) was better maintained when compared to the control group (day 7 24.3 versus 14.8, p = 0.003; day 12 28 versus 15, p = 0.003; day 22 33.5 versus 21.8, p = 0.014, respectively). Systemic oxidative stress associated with exposure to NM was significantly higher in the saline-treated group than in DRS-treated group (p < 0.011).

CONCLUSIONS

The findings of this study indicate the effectiveness of DRS in reducing of NM-induced ocular injuries. Its use should be considered as an immediate treatment modality following exposure to mustard agents to reduce potential ocular injury.

The regulatory roles of apoptosis-inducing factor in the formation and regression processes of ocular neovascularization

The role of apoptosis in the formation and regression of neovascularization is largely hypothesized, although the detailed mechanism remains unclear. Inflammatory cells and endothelial cells both participate and interact during neovascularization. During the early stage, these cells may migrate into an angiogenic site and form a pro-angiogenic microenvironment. Some angiogenic vessels appear to regress, whereas some vessels mature and remain. The control mechanisms of these processes, however, remain unknown. Previously, we reported that the prevention of mitochondrial apoptosis contributed to cellular survival via the prevention of the release of proapoptotic factors, such as apoptosis-inducing factor (AIF) and cytochrome c. In this study, we investigated the regulatory role of cellular apoptosis in angiogenesis using two models of ocular neovascularization: laser injury choroidal neovascularization and VEGF-induced corneal neovascularization in AIF-deficient mice. Averting apoptosis in AIF-deficient mice decreased apoptosis of leukocytes and endothelial cells compared to wild-type mice and resulted in the persistence of these cells at angiogenic sites in vitro and in vivo. Consequently, AIF deficiency expanded neovascularization and diminished vessel regression in these two models. We also observed that peritoneal macrophages from AIF-deficient mice showed anti-apoptotic survival compared to wild-type mice under conditions of starvation. Our data suggest that AIF-related apoptosis plays an important role in neovascularization and that mitochondria-regulated apoptosis could offer a new target for the treatment of pathological angiogenesis.

Altered angiogenesis in caveolin-1 gene-deficient mice is restored by ablation of endothelial nitric oxide synthase

Caveolin-1 is an essential structural protein of caveolae, specialized plasma membrane organelles highly abundant in endothelial cells, where they regulate multiple functions including angiogenesis. Caveolin-1 exerts a tonic inhibition of endothelial nitric oxide synthase (eNOS) activity. Accordingly, caveolin-1 gene-disrupted mice have enhanced eNOS activity as well as increased systemic nitric oxide (NO) levels. We hypothesized that excess eNOS activity, secondary to caveolin deficiency, would mediate the decreased angiogenesis observed in caveolin-1 gene-disrupted mice. We tested tumor angiogenesis in mice lacking either one or both proteins, using in vitro, ex vivo, and in vivo assays. We show that endothelial cell migration, tube formation, cell sprouting from aortic rings, tumor growth, and angiogenesis are all significantly impaired in both caveolin-1-null and eNOS-null mice. We further show that these parameters were either partially or fully restored in double knockout mice that lack both caveolin-1 and eNOS. Furthermore, the effects of genetic ablation of eNOS are mimicked by the administration of the NOS inhibitor N-nitro-L-arginine methyl ester hydrochloride (L-NAME), including the reversal of the caveolin-1-null mouse angiogenic phenotype. This study is the first to demonstrate the detrimental effects of unregulated eNOS activity on angiogenesis, and shows that impaired tumor angiogenesis in caveolin-1-null mice is, at least in part, the result of enhanced eNOS activity.

A peptide derived from type 1 thrombospondin repeat-containing protein WISP-1 inhibits corneal and choroidal neovascularization

PURPOSE

Ocular neovascularization is the primary cause of blindness in a wide range of prevalent ocular diseases including proliferative diabetic retinopathy, exudative age-related macular degeneration, and retinopathy of prematurity, among others. Antiangiogenic therapies are starting to give promising results in these diseases. In the present study the antiangiogenic potential of an 18-mer peptide derived from type 1 thrombospondin repeat-containing protein WISP-1 (wispostatin-1) was analyzed in vitro with human retinal endothelial cell proliferation and migration assays. The peptide was also tested in vivo in the corneal micropocket and the laser-induced choroidal neovascularization (CNV) mouse models.

METHODS

Human retinal endothelial cells were treated with the WISP-1 peptide and in vitro migration and proliferation assays were performed. Also evaluated was the antiangiogenic effect of this peptide in vivo using the corneal micropocket assay and the laser-induced CNV model.

RESULTS

Wispostatin-1 derived peptide demonstrated antimigratory and antiproliferative activity in vitro. Wispostatin-1 completely abolished bFGF-induced neovascularization in the corneal micropocket assay. The peptide also demonstrated significant inhibition of laser-induced CNV.

CONCLUSIONS

An inhibitory effect of Wispostatin-1 on ocular neovascularization was found in vitro and in vivo. The identification of novel and potent endogenous peptide inhibitors provides insight into the pathogenesis of corneal and choroidal neovascularization. The results demonstrate potential for therapeutic application in prevalent ocular disease.

The effects of the subconjunctival injection of bevacizumab (Avastin®) on angiogenesis in the rat cornea

The purpose of this study was to evaluate the effects of the use of the subconjunctival injection of bevacizumab (Avastin®) on angiogenesis in the rat cornea. Corneas of 20 Wistar male rats were cauterized with silver nitrate crystal. Animals were divided in four groups: control group (GC) that received subconjunctivally 0.02 ml of 0.9% saline solution on the day of the lesion; group GO that received subconjunctivally 0.02 ml of bevacizumab just after the lesion; group G3 that received bevacizumab on day 3 and group G5 that received bevacizumab on day 5 after lesion. Animals were euthanized on day 7. The newly formed vessels were quantified after China Ink perfusion and photographs were obtained and analyzed in a computerized system (Image Pro-Plus®). In the control group, neovascularization covered 53.56% ± 15.11 (mean ± SD) of the corneal surface, compared with 35.57% ± 18.80 (mean ± SD) in the G0 group, 30.60%±11.82 (mean±SD) in the G3 and 35.86%±0.07 (mean±SD) in the G5. The results showed an inhibition of angiogenesis when the control group was compared with all treated groups. These results suggest that subconjunctival injection of bevacizumab is able to inhibit corneal angiogenesis independently of the day of treatment.

The role of integrin alpha5beta1 in the regulation of corneal neovascularization

Integrins are transmembrane receptor proteins critical for growth and stabilization of vessels, but the mechanisms by which integrin activities are involved in neoangiogenesis of the eye remain unclear. Specific inhibitors to fibronectin receptor integrin alpha(5)beta(1) impeded pathological neovascularization in vivo. Our objective was to determine whether alpha(5)beta(1) plays a role in ocular angiogenesis, and whether a novel alpha(5)beta(1)-inhibiting small molecule is able to reduce angiogenesis in a model of inflammatory corneal neovascularization. Corneal neovascularization was induced in C57Bl/6 mice by NaOH-application and debridement of the limbal epithelium. Mice were randomized into six groups receiving either no treatment, or intraperitoneal osmotic pumps delivering three different doses of integrin antagonist or control substance on day 10 after scraping. In order to quantify the neovascular response, flatmounts were stained with FITC-CD31. Integrin alpha(5) expression was determined by immunohistochemistry and quantified by semiquantitative western blot analysis. Influence of integrin antagonist treatment on the mRNA expression of VEGF, bFGF and integrin alpha(5) was quantified by real-time RT-PCR. Vascularized corneas demonstrated a strong up-regulation of integrin alpha(5) within affected areas. Animals treated systemically with alpha(5)beta(1)-inhibiting small molecule showed a significant inhibition and regression of corneal neovascularization. PCR analysis evinced a significant up-regulation of VEGF and integrin alpha(5) mRNA levels in injured animals compared to controls, and a significant reduction of integrin alpha(5) mRNA in substance-treated animals compared to control substance, but no significant differences of bFGF levels in all groups. Western blot analysis of integrin alpha(5)beta(1) protein expression showed a trend towards up-regulation in injured animals, both control substance-treated and those treated with the alpha(5)beta(1)-inhibiting small molecule. Systemic delivery of an alpha(5)beta(1)-inhibiting small molecule inhibits and regresses corneal neovascularization induced by mechanical-alkali burn corneal injury. These results suggest an essential role for the integrin alpha(5)beta(1) in pathological neovascular processes of the cornea. Integrin alpha(5)beta(1) inhibitors could become a new approach for treatment of neovascularization in the eye.

A bio-mathematical model of time prediction in corneal angiogenesis after alkali burn

BACKGROUND

The determination of angiogenesis time is the key prerequisite to obtaining a balance between valid repair and excessive angiogenesis in wound healing. The aim of the investigation was to establish a bio-mathematical model predicting corneal angiogenesis time after alkali burn by back propagation neural network (BP neural network).

METHODS

The corneas of mice in 24 groups were burned by 0.01 mol/l NaOH. Five mice in each group were sacrificed at 6h after alkali burn. The expression levels of vegf and tsp2, determined by real-time quantitive PCR, were used as input vectors in BP neural network. Meanwhile, the corneal angiogenesis of other mice, inspected every 3h in 24 groups till the angiogenesis time were determined, served as output vectors. The data of 18 groups were randomly chosen for network adaptation while that of other 6 groups for simulation forecasting with functions of minmax (), postreg, prepca, trapca, respectively.

RESULTS

A bio-mathematical model of two-level BP neural network was established, for its purpose to predict the angiogenesis time through the expression values of vegf and tsp2. The performance index (0.00999996) was smaller than the target value (0.01) after adapting 36,557 times and the accuracy rate of this predict system was 83.33%. Furthermore, the ideal regression line and the optimization regression line were almost coincident (R=0.988 in network adaptation and R=0.793 in simulation forecasting).

CONCLUSIONS

The investigation indicated that the bio-mathematical model had available performance of simulation and forecasting. It might provide a novel method to solve clinical problems.

Inhibition of corneal angiogenesis by ascorbic acid in the rat model

PURPOSE

To evaluate the effect of topically administered ascorbic acid on experimentally induced corneal neovascularization in the rat model.

MATERIALS AND METHODS

Corneal chemical cauterization of 72 eyes in Long-Evans male rats was performed using silver nitrate/potassium nitrate sticks. Nine groups of eight eyes were used to evaluate eight concentrations of ascorbic acid with one group of eight eyes serving as a control. Topical instillation of 100 mg/ml non-pH-neutralized ascorbic acid was performed in one group while the remaining seven groups were evaluated using pH-neutralized ascorbic acid in concentrations of 100 mg/ml, 50 mg/ml, 10 mg/ml, 5 mg/ml, 1 mg/ml, 500 microg/ml, and 250 microg/ml.

RESULTS

The percentage of corneal neovascularization and burn stimulus score was determined for all the eyes. The means of percent of corneal neovascularization in ascorbic acid 100 mg/ml (non-neutralized), 100 mg/ml, 50 mg/ml, 10 mg/ml, 5 mg/ml, 1 mg/ml, 500 microg/ml, 250 microg/ml, and control group were 17.50 +/- 12.80 (p = 0.001), 17.00 +/- 19.30 (p = 0.001), 15.25 +/- 13.26 (p = 0.001), 17.62 +/- 11.89 (p = 0.001), 28.87 +/- 23.08 (p = 0.001), 29.62 +/- 16.91 (p = 0.001), 60.12 +/- 8.50 (p = 0.04), 65.62 +/- 2.26 (p = 0.185), and 68.25 +/- 4.06, respectively (Tables 1 and 2). All animals had a burn score of 2+ or higher (Table 1).

CONCLUSION

Ascorbic acid applied in a topical solution appears to inhibit corneal neovascularization in the rat model of inflammatory neovascularization in concentrations in a dose-dependent manner. The optimal dose-effect relation was in our model found in concentrations between 1 mg and 500 microg/ml. At concentrations below 500 microg/ml there was no statistically significant inhibition in the degree of corneal neovascularization compared to control.

Proangiogenic role of ephrinB1/EphB1 in basic fibroblast growth factor-induced corneal angiogenesis

Corneal neovascularization is a vision-threatening condition caused by various ocular pathological conditions. The aim of this study was to evaluate the function of the ephrin ligands and Eph receptors in vitro and in vivo in corneal angiogenesis in a mouse model. The Eph tyrosine kinase receptors and their ligands, ephrins, are expressed on the cell surface. The functions of Eph and ephrins have been shown to regulate axonal guidance, segmentation, cell migration, and angiogenesis. Understanding the roles of Eph and ephrin in corneal angiogenesis may provide a therapeutic intervention for the treatment of angiogenesis-related disorders. Immunohistochemical studies demonstrated that ephrinB1 and EphB1 were expressed in basic fibroblast growth factor (bFGF)-induced vascularized corneas. EphB1 was specifically colocalized with vascular endothelial marker CD31 surrounded by type IV collagen. EphrinB1 was expressed in corneal-resident keratocytes and neutrophils. Recombinant ephrinB1-Fc, which induces EphB receptor activation, enhanced bFGF-induced tube formation in an in vitro aortic ring assay and promoted bFGF-induced corneal angiogenesis in vivo in a corneal pocket assay. Synergistically enhanced and sustained activation of extracellular signal-regulated kinase was noted in vascular endothelial cell lines after stimulation with ephrin B1 and bFGF combinations. These results suggest that ephrinB1 plays a synergistic role in corneal neovascularization.

Descemet membrane endothelial keratoplasty (DMEK)

PURPOSE

To describe Descemet membrane endothelial keratoplasty (DMEK) with organ cultured Descemet membrane (DM) in a human cadaver eye model and a patient with Fuchs endothelial dystrophy.

METHODS

In 10 human cadaver eyes and 1 patient eye, a 3.5-mm clear corneal tunnel incision was made. The anterior chamber was filled with air, and the DM was stripped off from the posterior stroma. From organ-cultured donor corneo-scleral rims, 9.0-mm-diameter "DM rolls" were harvested. Each donor DM roll was inserted into a recipient anterior chamber, positioned onto the posterior stroma, and kept in position by completely filling the anterior chamber with air for 30 minutes.

RESULTS

In all recipient eyes, the donor DM maintained its position after a 30-minute air-fill of the anterior chamber followed by an air-liquid exchange. In the patient's eye, 1 week after transplantation, best-corrected visual acuity was 1.0 (20/20) with the patient's preoperative refraction, and the endothelial cell density averaged 2350 cells/mm.

CONCLUSION

DMEK may provide quick visual rehabilitation in the treatment of corneal endothelial disorders by transplantation of an organ-cultured DM transplanted through a clear corneal tunnel incision. DMEK may be a highly accessible procedure to corneal surgeons, because donor DM sheets can be prepared from preserved corneo-scleral rims.

Inhibition of experimental corneal neovascularisation by bevacizumab (Avastin)

AIM

To evaluate the effect of topically administered bevacizumab (Avastin) on experimental corneal neovascularisation in rats.

METHODS

Silver nitrate sticks (75% silver nitrate, 25% potassium nitrate) were used to perform chemical cauterisation on the corneas of 16 eyes from 16 male Long Evans rats. For the following 7 days, the 10 eyes in the treatment group were instilled with bevacizumab 4 mg/ml drops twice daily, whereas the 6 eyes in the control group received placebo (normal saline drops twice daily). Digital photographs of the cornea were analysed to determine the area of cornea covered by neovascularisation as a percentage of the total corneal area.

RESULTS

In the bevacizumab-treated eyes, neovascularisation covered, on average, 38.2% (15.5%) (mean (SD)) of the corneal surface compared with 63.5% (5.0%) in the control group (p<0.02, Mann-Whitney U test).

CONCLUSION

Topically administered bevacizumab (Avastin) at a concentration of 4 mg/ml limits corneal neovascularisation following chemical injury in the male Long Evans rat model.

Triamcinolone acetonide inhibits IL-6- and VEGF-induced angiogenesis downstream of the IL-6 and VEGF receptors

PURPOSE

To test whether triamcinolone acetonide (TA) inhibits angiogenesis induced by IL-6 or VEGF and whether this inhibition is through antagonism of the IL-6 or the VEGF receptor 2.

METHODS

A rat cornea micropocket assay was used to initiate IL-6- and VEGF-mediated angiogenesis. The ability of TA or neutralizing VEGF antibody to inhibit IL-6- or VEGF-mediated neovascularization was analyzed by measuring vessel length, vessel extension, and vessel area. The phosphorylation of signal transduction activator 3 (STAT3), VEGF receptor, and extracellular signal-regulated kinase 1/2 (ERK1/2) was determined by Western blot in human umbilical vein endothelial cell (HUVEC) lysates after stimulus with IL-6 or VEGF, with and without TA pretreatment. The effect of IL-6 or TA on STAT3 expression in cornea was determined by Western blot.

RESULTS

IL-6 induced corneal angiogenesis in a dose-dependent manner, with 350 ng producing a peak at day 6. VEGF antibodies and TA blocked IL-6-mediated limbal neovascularization. TA also directly inhibited angiogenesis stimulated by a VEGF pellet; the glucocorticoid receptor antagonist mifepristone neutralized TA inhibition of angiogenesis. TA did not inhibit IL-6-induced STAT3 phosphorylation and did not inhibit VEGF-induced phosphorylation of the VEGF receptor 2 or of ERK1/2 in endothelial cells, but TA decreased IL-6-induced STAT3 expression in cornea.

CONCLUSIONS

IL-6- and VEGF-mediated corneal neovascularization are blocked by TA through the mifepristone-sensitive steroid receptor. TA inhibits IL-6-induced STAT3 expression in cornea, but it does not inhibit activation of the IL-6 or the VEGF receptor in cultured human endothelial cells. This finding has two implications. The fact that TA directly inhibits VEGF action implies that other factors may be critical to angiogenesis and sensitive to glucocorticoids.

Anti-angiogenic activities of hypericin in vivo: potential for ophthalmologic applications

Hypericin, a perihydroxylated dianthraquinone is shown here to be a highly potent inhibitor of angiogenesis in several ocular models examined in rat eyes. Extensive angiogenesis induced in the cornea and iris by intra-ocular administration of FGF-2 was effectively inhibited by a minimum of four dose regimens of hypericin (2 mg/kg) administered via the intraperitoneal route at 48 h intervals. Maximal inhibition was achieved when animal treatment with hypericin was initiated 48 h prior to inoculation of FGF-2. The molecular basis for the hypericin-mediated inhibition of angiogenesis in the anterior eye compartment appears to involve several sites in the cascade leading to angiogenesis. We show that the activating phosphorylation of extracellular signal-regulated MAP kinases (ERK1/2) is inhibited by hypericin in human retinal pigment epithelial cells and in EA.hy926 cells, an endothelial hybridoma expressing endothelial cell properties. ERK1/2 activity is required for the transactivation of hypoxia-inducible factor 1 alpha (HIF-1alpha) and in VEGF-induced blood vessel sprouting. MT1-MMP activity in human microvascular endothelial cells was also inhibited. The findings identify hypericin as a potentially useful agent in the treatment of ophthalmic neovascularization pathogeneses.

[Study on the rat models of corneal neovascularization induced by alkali burn]

PURPOSE

The aim of this series of experiments was to test appropriate rat models of corneal neovascularization (CNV) induced by alkali injury.

METHODS

All animals (n=48) were randomly assigned to four groups, each consisting of twelve eyes. Alkali injury was induced on day 0 by application of iN NaOH to right eyes of S-D rats for 15 30 AG and 6Os respectively. Biomicroscopic features including corneal neovascularization, corneal ulceration and hyphema were observed for 28 days.

RESULTS

Corneal neovascularization began to invade pericornea on day 3 and flourished on day 7, then reached its developmental peak on day 14, and regressed gradually after day 14. The induced rate of CNV for groups 15s, 30s, 40, 60s, were 16.7%, 75%, 100%, 100% respectively, the induced rate of corneal neovascularization in all groups increased with time prolonging. CNV distributed sparsely in group iSs and its length was more shorter. CNV in group 30s reached the margin of burn area and distributed sparsely. There had uniform growth of CNV in group 40s and the hyphema was not more excessive than that of group 60s which was difficult to observe CNV. Significant difference (P < 0.05) was found between Group 30s and 40s in length and area of CNV respectively. The rate of hyphema was 16.7%, 83.3% respectively between Group 40s and 60s and significant difference (P < 0.05) was also found. The rate of corneal ulceration and perforation was 50% and 33.3% respectively in Group 60s.

CONCLUSIONS

The appropriate induced time for S-D rat models of corneal neovascularization by using filter paper which diameter is 3 mm and inmerged solution of 1 mol/L sodium hydroxide was 40s. It's an ideal animal model for CNV induced by chemical injuries.

Contribution of bone marrow-derived pericyte precursor cells to corneal vasculogenesis

PURPOSE

Bone-marrow (BM)-derived hematopoietic precursor cells are thought to participate in the growth of blood vessels during postnatal vasculogenesis. In this investigation, multichannel laser scanning confocal microscopy and quantitative image analysis were used to study the fate of BM-derived hematopoietic precursor cells in corneal neovascularization.

METHODS

A BM-reconstituted mouse model was used in which the BM from enhanced green fluorescent protein (GFP)-positive mice was transplanted into C57BL/6 mice. Basic fibroblast growth factor (bFGF) was used to induce corneal neovascularization in mice. The vasculogenic potential of adult BM-derived cells and their progeny were tested in this in vivo model. Seventy-two histologic sections selected by systematic random sampling from four mice were immunostained and imaged with a confocal microscope and analyzed with image-analysis software.

RESULTS

BM-derived endothelial cells did not contribute to bFGF-induced neovascularization in the cornea. BM-derived periendothelial vascular mural cells (pericytes) were detected at sites of neovascularization, whereas endothelial cells of blood vessels originated from preexisting blood vessels in limbal capillaries. Fifty three percent of all neovascular pericytes originated from BM, and 47% of them originated from preexisting corneoscleral limbus capillaries. Ninety-six percent and 92% of BM-derived pericytes also expressed CD45 and CD11b, respectively, suggesting their hematopoietic origin from the BM.

CONCLUSIONS

Pericytes of new corneal vessels have a dual source: BM and preexisting limbal capillaries. These findings establish BM as a significant effector organ in corneal disorders associated with neovascularization.

Cellular Events in the Normal and Inflamed Cornea

PURPOSE

Although normal cornea is an avascular transparent structure, bone marrow (BM)-derived cells exist in situ even in noninflamed conditions. We evaluated constitutive cellular trafficking into the cornea in the naive state and investigated how corneal inflammation may be initiated by various stimuli.

METHODS

BM chimeric mice were generated using BM from enhanced green fluorescent protein (eGFP) transgenic mice. Corneas of chimeric mice were carefully studied by fluorescent biomicroscopy until 6 months after transplantation. To analyze initiation of cellular events in corneal immune response, we cauterized the center of the cornea or inoculated IL-1 beta into the corneal micropocket. Cellular events were analyzed by flow cytometry.

RESULTS

At 2 weeks after BM transplantation, GFP cells gradually migrated into the cornea from the limbal area and were distributed over the entire cornea at 6 months. In both the cauterization and micropocket assays, infiltration of neutrophils and macrophages occurred on days 2 and 4, respectively. Depletion of neutrophils by anti-Gr-1 Ab significantly reduced corneal edema/opacity induced by cauterization. IL-1 beta-induced angiogenesis was markedly reduced in monocyte chemoattractant protein-1 knockout mice.

CONCLUSIONS

BM-derived cells are recruited into the normal cornea and may be essential to maintain corneal clarity. In the inflamed cornea, neutrophils might be responsible for acute corneal edema/opacity and macrophages for corneal angiogenesis and chronic inflammation.

Corneal toxicity and inflammation secondary to retained perfluorodecalin

PURPOSE

To describe a case with bullous keratopathy and anterior segment inflammation associated with heavy liquids.

DESIGN

Observational case report.

METHODS

Review of clinical and histopathologic changes.

RESULTS

A 65-year-old patient underwent a pars plana vitrectomy for a rhegmatogenous retinal detachment. Perfluorodecalin was used as a temporary retinal tamponade. After surgery, bubbles of heavy liquid were noted in the anterior chamber. Fifteen months later, severe corneal edema developed, associated with corneal vascularization and keratic precipitates. Removal of heavy liquid through a paracentesis was attempted but the cornea remained edematous, and a penetrating keratoplasty was performed. In the histopathologic examination inflammatory changes from retention of perfluorodecalin were observed. There was a decompensated cornea with florid bullous keratopathy, inflammatory infiltration with vascularization, and deposition of perfluorodecalin within keratocytes and perivascular macrophages.

CONCLUSION

Presence of heavy liquids in the anterior chamber may be associated with an intense inflammatory response and corneal decompensation.

Inhibitory effect of triamcinolone acetonide on corneal neovascularization

BACKGROUND

Corneal neovascularization (NV) plays an important role in the pathogenesis of corneal disorders. Recently, triamcinolone acetonide (TA) has been reported as a potential treatment for ocular angiogenesis. However, there are no reports on the inhibitory effect of TA on the corneal NV.

METHODS

Triamcinolone acetonide (2 mg) was administered to four rabbits' eyes by a subconjunctival injection immediately after a basic fibroblast growth factor (bFGF)-pellet was placed into the cornea. As a control, four eyes received an injection of distilled water. Four weeks later, the inhibition of corneal NV was evaluated as the percentage ratio of the vessel invasion area to the area that was sandwiched between the pellet and the limbus cornea. To identify the characteristic appearance of new corneal vessels, the control cornea was examined by using the antibody of vascular endothelial growth factor (VEGF). To confirm TA concentration in TA-treated corneas, the TA level was measured using high-performance liquid chromatography.

RESULTS

Neovascularization from the limbus to the pellet was detected in control eyes 4 weeks after the bFGF pellet implantation. TA-treated eyes demonstrated the inhibition of the neovascular response to the pellet. The severity of NV as compared between control and TA-treated eyes was statistically significant (P<0.05). Morphologically, new vessel growth was shown in the control cornea, and endothelial cells of new vessels were positively stained with the antibody of VEGF. TA concentration in TA-treated corneas at 2 weeks showed 63.5+/-42.8 microg/g (n=4, mean +/- SD), while TA was not detected in control and TA-treated corneas at 4 weeks. The level of TA was effectively maintained for at least 2 weeks after the subconjunctival injection.

CONCLUSION

We have demonstrated that subconjunctival TA administration inhibited rabbit corneal NV. This agent may prove useful in the treatment of corneal angiogenic disorders.

Treatment of ocular tissues exposed to nitrogen mustard: beneficial effect of zinc desferrioxamine combined with steroids

PURPOSE

Exposure of the ocular surface to mustard gas chemical warfare leads to a destructive inflammatory reaction. Both steroids and a novel metalocomplex free radical scavenger, zinc desferrioxamine (Zn/DFO), have been shown to be effective separately in reducing ocular damage. The purpose of the present study was to investigate whether the effectiveness of both medications applied simultaneously is superior to the effectiveness of either one applied alone.

METHODS

One eye in each of 52 rabbits was exposed to 2% nitrogen mustard (NM). Topical treatment with eye drops of a metal complex-zinc desferrioxamine (Zn/DFO)-combined with dexamethasone phosphate (0.1%), was compared with the administration of saline or treatment with Zn/DFO or dexamethasone alone. Eight eyes (four animals) that were not exposed to NM served as the control. Examiners masked to the treatment groups assessed the extent of ocular injury and the response to treatment using clinical, histologic, and biochemical criteria.

RESULTS

Treatment with the combination of Zn/DFO and dexamethasone was significantly more effective than was dexamethasone or Zn/DFO alone in reducing NM injury to ocular anterior segment structures. In combination-treated eyes, corneal re-epithelization was faster, corneal neovascularization was less severe, and intraocular pressure was not as severely elevated as in the saline or the Zn/DFO- or dexamethasone-alone groups. In addition, systemic antioxidant status was better conserved in the combination-treated animals.

CONCLUSIONS

The findings suggest that the combination of topically applied Zn/DFO and dexamethasone, by virtue of their additive inhibitory effects on free radical formation and inflammation, should be considered as a basis for the treatment of ocular mustard gas injuries.

Characterization of a monoclonal antibody that antagonizes the function of human endostatin

Endostatin, a 20-kDa proteolytic fragment of collagen XVIII, is a potent inhibitor of angiogenesis and tumor growth. The anti-angiogenic effects of endostatin include inhibition of endothelial cell migration and proliferation, and inhibition of the activity of MMP2. Structure-function analysis of endostatin that implies this contravention function buried in separate fragments of endostatin introduces new issues into the understanding of the structure-function relationship of endostatin. We developed and characterized a novel murine MAb, 4E7, to human endostatin, which antagonizes the function of endostatin. As we show here, MAb 4E7 blocks the anti-migration/adhesion effects of endostatin in vitro and the anti-angiogenesis effect of endostatin in vivo, but the inhibition effect of endostatin on endothelial cell proliferation is not affected by MAb4E7. These results suggest that the anti-migration and anti-proliferation functions of endostatin may have distinct structural foundations.

Corneal neovascularization suppressed by TIMP2 released from human amniotic membranes

PURPOSE

To investigate the effects of culture medium of human amniotic membrane (AM) on corneal neovascularization (CNV) induced by basic fibroblast growth factor (bFGF) in mice.

METHODS

Culture medium of amniotic membrane was prepared by cultivating AM (with epithelium side up) in EGM basic medium for 3 days, and was collected separately to three groups, e.g. control (EGM only), AM with epithelium (AM) and AM without epithelium (De-AM). Corneal neovascularization was induced in mice by using micropocket assay with Hydron polymer pellets containing 100 ng bFGF. Migration and proliferation of human umbilical cord vein endothelial cells (HUVEC) were performed in Boyden chambers and by using the CyQUANT fluorescence binding assay respectively. The levels of tissue inhibitors of metalloproteinase 1 and 2 (TIMP1, TIMP2) in culture medium were determined by ELISA assay.

RESULTS

CNV induced by bFGF was significantly suppressed by culture medium of amniotic membrane. When the medium was applied as an eyedrop 4 times a day for 7 days, the area of CNV was (2.48+/-0.76) mm(2),(0.64+/-0.52) mm(2) and (1.96+/-0.65) mm(2) in control, AM and De-AM group respectively. The migration and proliferation of HUVEC were strongly inhibited by culture medium of AM with epithelium, while the De-AM had no effect on the migration of HUVEC cells. The high level of TIMP2 was found in AM group, but not in De-AM group, while there was no difference in the amount of TIMP1 in medium among three groups.

CONCLUSION

Culture medium of amniotic membrane significantly suppresses the corneal nevovascularization induced by bFGF. The mechanism of which at least in part is that high level of TIMP2 protein secreted or released into the culture medium of AM and inhibition of migration and growth of vascular endothelial cells.

Inhibitory Effect of Rapamycin on Corneal Neovascularization In Vitro and In Vivo

PURPOSE

To examine the effect of rapamycin on the proliferation and the migration of human umbilical vein endothelial cells (HUVECs) and on the corneal neovascularization in the corneal alkaline burn murine model.

METHODS

HUVEC proliferation, migration, and apoptosis were examined after treatment with rapamycin. The effect of rapamycin on the mRNA expression of FK506 binding protein (FKBP)-12 and mammalian target of rapamycin (mTOR) was also evaluated in vitro. Corneal neovascularization was induced in vivo by an alkaline burn of the cornea with 1 N NaOH on BALB/c mice. Rapamycin was given intraperitoneally at 2 mg/kg body weight once a day for 12 days after the corneal alkaline burn. Growth factors and cytokines related with neovascularization and inflammation were evaluated in the corneal tissue and the peripheral blood by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. The corneal neovascularization was evaluated by a slit lamp biomicroscopy.

RESULTS

Rapamycin at the concentration of 1000 ng/mL for >48 hours' exposure significantly inhibited the growth of HUVECs. The double chamber assay showed that rapamycin dramatically inhibited the migration of HUVECs at concentrations of 10 and 100 ng/mL and that these concentrations did not affect endothelial cell growth. When TUNEL assays were performed, the number of apoptotic cells increased 1.9-, 2.1-, and 2.6-fold compared with the control at 10, 100, and 1000 ng/mL, respectively, of rapamycin at 48 hours of exposure. RT-PCR showed that the expression of mTOR was suppressed in the HUVECs after rapamycin treatment; however, FKBP-12 expression was not affected. Among the angiogenic factors, gene expression of substance P and hypoxia inducible factor (HIF)-1 alpha was inhibited by rapamycin earlier (1-3 days), with vascular endothelial growth factor (VEGFR)-1 gene expression being suppressed for the first 7 days in the corneal tissue. The protein level of substance P and vascular endothelial growth factor (VEGF) was significantly decreased--more in mice treated with rapamycin than the control mice--as shown by ELISA assay of peripheral blood. Furthermore, rapamycin significantly inhibited corneal neovascularization in the alkaline-burned cornea.

CONCLUSIONS

Rapamycin strongly inhibited HUVEC migration at doses that did not cause cytotoxicity and apoptosis in this in vitro model. Rapamycin also suppressed corneal neovascularization, possibly by inhibiting proinflammatory cytokines, as shown by the in vivo study. Therefore, rapamycin may be useful as an angiogenic regulator in the treatment of corneal diseases that manifest with neovascularization.

Inhibition of corneal angiogenesis by local application of vasostatin

PURPOSE

This study was designed to investigate the effects of the locally supplied endogenous angiogenesis inhibitor vasostatin (VS) on corneal angiogenesis.

METHODS

Recombinant VS was expressed and purified. The effects of VS on the proliferation of endothelial cells were investigated using the methyl thiazolyl tetrazolium (MTT) assay in the absence or presence of angiogenic factors such as basic fibroblast growth factor (bFGF) or vascular endothelial growth factor (VEGF). Corneal neovascularization was induced by implantation of hydron pellets containing bFGF in rat corneal micropockets. The potency of VS to inhibit corneal angiogenesis was investigated by incorporation of VS with bFGF in hydron pellets or topical application of VS containing eye drops to rat eyes implanted with bFGF pellets. The extent of corneal neovascularization was evaluated by microscopic and histological analyses.

RESULTS

VS potently inhibited the growth of endothelial cells in the absence or presence of angiogenic factors such as bFGF or VEGF. In the rat corneal micropocket assay, concurrent incorporation of VS abolished the bFGF induced neovascularization. When formulated in a methylcellulose eye drop, VS remained intact and functional in a 4 degrees C solution for more than 7 days. Topical application of VS eye drops potently inhibited bFGF induced neovascularization in rat corneas.

CONCLUSIONS

The present study effectively demonstrated the potential feasibility of local application of VS for treatment of corneal angiogenesis.

Comparative analysis of the in vivo angiogenic properties of stable prostacyclin analogs: a possible role for peroxisome proliferator-activated receptors

OBJECTIVE

Until recently, prostacyclin (PGI2) biological activities were thought to be exclusively mediated by cell surface receptors named IP. Recent studies have instead identified a novel pathway of PGI2 signaling, occurring through activation of peroxisome proliferator-activated receptors (PPARs) located in the nucleus. The availability of stable PGI2 analogs with different affinity for IP receptors and PPARs provides the possibility to test the importance and function of this dual pathway in vitro and in vivo. In this study, the in vivo angiogenic properties of different PGI2 analogs and the potential relationship between PPAR-mediated pathways, vascular endothelial growth factor (VEGF), and angiogenesis were investigated.

METHODS AND RESULTS

By using the murine corneal model of angiogenesis, we found that PGI2 analogs able to act on nuclear PPARs, such as iloprost and carbaprostacyclin (cPGI), induce angiogenesis in vivo. In contrast, cicaprost, a PGI2 analog that only acts on IP receptors, has no in vivo angiogenic activity. Interestingly, angiogenesis induced by iloprost and cPGI does not differ in extent and morphology from that induced by VEGF and is associated with local increment of VEGF mRNA expression and protein levels. Finally, iloprost-induced angiogenesis is significantly decreased by systemic inhibition of VEGF activity, obtained by gene transfer of a soluble form of the VEGF receptor Flt-1.

CONCLUSIONS

These data demonstrate that stable PGI2 analogs may have angiogenic properties in vivo, depending on their ability to act on PPARs. The resulting angiogenic process appears to be mediated by VEGF. These findings indicate that important physiological activities in the cardiovascular system, such as angiogenesis and VEGF induction, may be modulated by PGI2 through specific activation of the PPAR signaling pathway in vivo, with potentially important fundamental and clinical implications.

Platelet-activating factor (PAF) induces corneal neovascularization and upregulates VEGF expression in endothelial cells

PURPOSE

Platelet-activating factor (PAF) is a potent proinflammatory mediator that accumulates in the cornea after injury and induces the expression of genes related to inflammation and wound healing. The current study was conducted to investigate the direct effect of PAF on corneal neovascularization and on the expression of angiogenic growth factors in vascular endothelial cells.

METHODS

Pellets containing carbamyl-PAF (cPAF) were implanted in corneas of wild-type or PAF-receptor (PAF-R)-knockout mice, and the progression of angiogenesis was monitored by microscope. In some experiments, mice were treated with a daily intraperitoneal injection of the PAF-R antagonist LAU8080. Migration assays of human umbilical cord vein endothelial cells (HUVECs) and human dermal microvascular endothelial cells (HMVECs) were performed in a Boyden chamber after addition of various concentrations of cPAF or bovine fibroblast growth factor (FGF-2). Cell proliferation was assessed by fluorescence-binding assay in the presence of cPAF or FGF-2 for 8 days. Vascular endothelial growth factor (VEGF) and FGF-2 expression was studied by RT-PCR and Northern- and Western-blot analyses in cells stimulated with cPAF at different concentrations and for different times.

RESULTS

Six days after cPAF pellet implantation, there were new vessels growing from the limbus to the center of the cornea. The PAF-induced neovascularization was significantly reduced in PAF-R-knockout mice and in mice treated with the PAF antagonist. cPAF added to the lower well of the Boyden chamber produced a dose-dependent migration of HUVECs and HMVECs that was inhibited in cells preincubated with LAU8080 or with a VEGF-blocking antibody. In contrast, cPAF did not stimulate proliferation of endothelial cells. cPAF induced VEGF mRNA and protein expression but not FGF-2 expression in HUVECs and HMVECs.

CONCLUSIONS

PAF stimulates corneal neovascularization by a receptor-mediated mechanism. Induction of VEGF expression and stimulation of vascular endothelial cell migration are initial events in PAF-promoted corneal angiogenesis.

Platelets release CXCL4L1, a nonallelic variant of the chemokine platelet factor-4/CXCL4 and potent inhibitor of angiogenesis

Platelet factor-4 (PF-4)/CXCL4 was the first chemokine described to inhibit neovascularization. Here, the product of the nonallelic variant gene of CXCL4, PF-4var1/PF-4alt, designated CXCL4L1, was isolated for the first time from thrombin-stimulated human platelets and purified to homogeneity. Although secreted CXCL4 and CXCL4L1 differ in only three amino acids, CXCL4L1 was more potent in inhibiting chemotaxis of human microvascular endothelial cells toward interleukin-8 (IL-8)/CXCL8 or basic fibroblast growth factor (bFGF). In vivo, CXCL4L1 was also more effective than CXCL4 in inhibiting bFGF-induced angiogenesis in rat corneas. Thus, activated platelets release CXCL4L1, a potent regulator of endothelial cell biology, which affects angiogenesis and vascular diseases.

Free Autologous Buccal Mucosal Graft Transplantation to Treat Ocular Complications after Toxic Epidermal Necrolysis: Case Report

BACKGROUND

Toxic epidermal necrolysis (TEN) can lead to ocular surface scarring associated with pain, dry eye symptoms, and decreased visual acuity that often are difficult to treat.

HISTORY AND SIGNS

A 34-year-old woman was referred to our department two-years after TEN induced by lamotrigin (lamictal(R)). She was complaining of severe visual acuity loss, pain, and dry eye symptoms. Visual acuity was reduced to light perception in the right eye (RE) and to 0.2 in left eye (LE). Basal Schirmer test was 2 mm in RE and 3 mm in LE. With or without therapeutic contact lenses, the patient was experiencing severe discomfort requiring tear supplementation up to 50 - 80 times/day in both eyes.

THERAPY AND OUTCOME

A free autologous mucosal graft (3.5 x 2.0 cm) was transplanted from the lower lip into the upper RE fornix. Six months after surgery, with therapeutic contact lenses, the need for tear supplementation was markedly reduced to 3 - 4 times/day in RE while it remained unchanged in LE. In RE, slit-lamp examination revealed decreases in the corneal stromal edema and in the diameter of neo-vessels associated with an improvement of visual acuity (counting fingers at 30 cm). Basal Schirmer test values were unchanged. It has to be mentioned that the improvement observed after surgery was markedly dependent on wearing a therapeutic contact lens.

CONCLUSIONS

Free autologous buccal graft transplantation (with its presumably accessory salivary glands) in association with the use of a therapeutic contact lens can be an efficient approach to treat ocular complication following drug-induced TEN (Lyell's syndrome).

Evaluation of a New Bioadhesive Copolymer (ADAL??) to Seal Corneal Incisions

OBJECTIVE

To evaluate the efficacy and clinical tolerance of a new acrylic copolymer tissue adhesive, ADAL, in corneal surgery.

METHODS

Corneal incisions were performed on 24 New Zealand albino rabbits. The incision was either sealed with ADAL bioadhesive, hydrated with balanced salt solution, or closed with 10-0 nylon surgical sutures. The incisions underwent weekly tensile strength testing and clinical, histopathologic, and confocal microscopy evaluations.

RESULTS

Clinical evaluation revealed good sealing and no incision leakage in any group. There was no anterior chamber reaction in any case. Compared with the hydrated group, there was somewhat more incisional vascularization and localized corneal opacity in the ADAL group, but there were no cases of severe corneal opacity or neovascularization. On histologic analysis, a slightly larger inflammatory reaction was noted in the ADAL group compared with the hydrated group. Tensile strength during the first week was statistically significantly greater in the ADAL group (2.93 Newtons) than in the control groups (1.40 Newtons, hydrated group; 1.43 Newtons, sutured group) (P < 0.001). Confocal microscopy study revealed a unique dendritic keratocyte shape and structure resembling shiny crystalline particles after disappearance of the adhesive from the cornea.

CONCLUSIONS

Corneal surgical incisions sealed with ADAL adhesive have superior tensile strength in the first postoperative week compared with incisions closed with sutures or hydrated with salt solution. Thereafter, findings in both groups became similar. The use of ADAL adhesive was not associated with any deleterious effects during the corneal incision-healing process compared with hydration or sutures.

Mouse strain-dependent heterogeneity of resting limbal vasculature

PURPOSE

Heterogeneity of the extent of angiogenesis induced by exogenous growth factors may be determined by genetic influences. Because angiogenesis is the formation of new vessels from preexisting ones, strain-related influences on naïve resting limbal vessel phenotype and gene expression were determined in mice having divergently low and high angiogenic responses.

METHODS

Resting limbal vessel surface area and density and extent of bFGF-induced corneal angiogenesis were determined in C57BL/6J, BALB/cJ, F1 intercross identical with C57BL/6J X 129S3/SvIM, and 129S3/SvIM mouse strains by quantitative three-dimensional reconstruction confocal microscopy. Strain-related influences on pro- and antiangiogenic gene expression in naïve cornea were determined by quantitative real-time RT-PCR.

RESULTS

The strain-dependent rank order of resting limbal vessel surface area and resting vessel density paralleled bFGF-induced neovascularization: 129S3/SvIM > BALB/cJ, F1 > C57BL/6J (P < 0.0006). Pigment epithelium-derived factor (PEDF) was increased more than 67-fold compared to Ang-2 in resting cornea of both C57BL/6J and 129S3/SvIM strains (P < 0.0001; P < 0.0001), suggesting a strongly antiangiogenic environment. The corneas of the C57BL/6J mice demonstrated 1.8-, 1.5-, and 1.7-fold increased mRNA levels for Flt-1, VEGF, and bFGF, respectively (P < 0.02; P < 0.04; P < 0.02); however, TSP-1 expression was increased 2.4-fold compared with 129S3/SvIM (P < 0.0004).

CONCLUSIONS

Strain-dependent differences in the resting limbal vessel surface area and density correlated with heterogeneity in the extent of bFGF-induced angiogenesis. Differences in pro- and antiangiogenic gene expression levels in resting cornea may influence vascular limbal phenotype during quiescence and may predict susceptibility to angiogenesis-dependent diseases.

VEGF164(165) as the pathological isoform: differential leukocyte and endothelial responses through VEGFR1 and VEGFR2

PURPOSE

Vascular endothelial growth factor (VEGF) induces angiogenesis and vascular permeability and is thought to be operative in several ocular vascular diseases. The VEGF isoforms are highly conserved among species; however, little is known about their differential biological functions in adult tissue. In the current study, the inflammatory potential of two prevalent VEGF isoform splice variants, VEGF(120(121)) and VEGF(164(165)), was studied in the transparent and avascular adult mouse cornea.

METHODS

Controlled-release pellets containing equimolar amounts of VEGF(120) and VEGF(164) were implanted in corneas. The mechanisms underlying this differential response of VEGF isoforms were explored. The response of VEGF in cultured endothelial cells was determined by Western blot analysis. The response of VEGF isoforms in leukocytes was also investigated.

RESULTS

VEGF(164) was found to be significantly more potent at inducing inflammation. In vivo blockade of VEGF receptor (VEGFR)-1 significantly suppressed VEGF(164)-induced corneal inflammation. In vitro, VEGF(165) more potently stimulated intracellular adhesion molecule (ICAM)-1 expression on endothelial cells, an effect that was mediated by VEGFR2. VEGF(164) was also more potent at inducing the chemotaxis of monocytes, an effect that was mediated by VEGFR1. In an immortalized human leukocyte cell line, VEGF(165) was found to induce tyrosine phosphorylation of VEGFR1 more efficiently.

CONCLUSIONS

Taken together, these data identify VEGF(164(165)) as a proinflammatory isoform and identify multiple mechanisms underlying its proinflammatory biology.

Reverse Effects of Tetraarsenic Oxide on the Angiogenesis Induced by Nerve Growth Factor in the Rat Cornea

To compare the antiangiogenic effects of tetraarsenic oxide (As4O6) with those of diarsenic oxide (As2O3) in the rat cornea, rat cornea micropocket assay was conducted to induce angiogenesis by implantation of the pellet contained 1.0 ng of nerve growth factor (NGF). Ten of thirty eyes of Sprague-Dawley rats were randomly assigned to one of three groups, namely, control group (no medication), As2O3 group (50 mg/kg As2O3, PO, s.i.d.), and As4O6 group (50 mg/kg As4O6, PO, s.i.d.). After implantation, the number of new vessels, vessel length and clock hour of neovascularization were examined under the microscope from day 3 to day 7. The area of neovascularization was calculated using a mathematical formula. Although new vessels in control and As2O3 groups were first noticed at day 3, whereas those of As4O6 group were first observed on day 5. The number, length, clock hour of neovascularization and areas of the vessels in As4O6 group showed more significant inhibition than those of control and As2O3 groups from day 5 (P<0.05). However, there were no differences in all parameters between control group and As2O3 group during the entire study period. These results showed that As4O6 had antiangiogenic effects on the new vessels induced by NGF in the rat cornea.

Effects of leptin on endothelial function with OB-Rb gene transfer in Zucker fatty rats

The metabolic syndrome in association with obesity is a major clinical problem inducing hypertension, diabetes mellitus, and atherosclerosis. Leptin induces angiogenesis by its proliferative effects on endothelial cells (ECs) via OB receptor (OB-Rb) gene. We evaluated the growth of ECs and intracellular signalings in response to leptin in vitro and the angiogenic effects of leptin in the cornea in vivo with and without adenovirus-mediated transfer of the OB-Rb gene in Zucker fatty (ZF) rats as a model for the metabolic syndrome. Recombinant adenovirus vector encoding rat OB-Rb (Ad.OB-Rb) or Escherichia coli. LacZ (Ad.LacZ) was transfected into cultured ECs from Zucker lean (ZL) rats and ZF rats. Leptin increased DNA synthesis dose-dependently in ECs from ZL rats but not ZF rats. Infection with Ad.OB-Rb, but not with Ad.LacZ, improved the growth effects of leptin in ECs from ZF rats. Leptin induced phosphorylation of Janus kinase (JAK)2, signal transducer and activator of transcription (STAT)3, and extracellular signal-regulated kinase (ERK) in ECs from ZL rats but not ZF rats. Infection with Ad.OB-Rb restored phosphorylation of JAK2 and STAT3 in ECs from ZF rats. Leptin induced angiogenesis in cornea from ZL rats, but not from ZF rats. Coadministration of leptin and Ad.OB-Rb induced angiogenesis in cornea from ZF rats. Ad.LacZ did not influence the angiogenic effects of leptin. The impaired endothelial function with the leptin resistance may be one of causes of the atherosclerosis in the metabolic syndrome.

Inhibition of experimental angiogenesis of cornea by somatostatin

BACKGROUND

This study evaluated the inhibitory activity of somatostatin 14 on the angiogenesis of cornea in vivo.

METHODS

Corneal neovascularization was induced with a pellet containing 90 ng of basic fibroblast growth factor (bFGF) in a rat corneal pocket model. Three kinds of pellets were made containing bFGF plus somatostatin (SST) 0 ng, 20 ng and 200 ng for the control group, group 1 and group 2, respectively. Neovascularization was observed biomicroscopically from day 4 to day 8, and the corneas were then examined for changes in histology. Quantitation of angiogenesis in the cornea was accomplished by caliper and image analysis.

RESULTS

The 200-ng dose of SST showed significant inhibition of both length and area of neovascularization on day 7 (0.62+/-0.11 mm vs 1.29+/-0.16 mm, 0.50+/-0.16 mm2 vs 1.35+/-0.29mm2, group 2 vs control; P<0.05). The 20 ng of somatostatin did not demonstrate any significant inhibition of neovascularization compared with the control group.

CONCLUSION

Our study demonstrated that SST 14 can reduce bFGF-induced corneal angiogenesis. This shows the potential value of somatostatin in the treatment of corneal neovascularization.

Corneal neovascularization possibly associated with latanoprost therapy

PURPOSE

To report a case of corneal neovascularization possibly associated with latanoprost therapy.

METHODS

CASE REPORT

A 67-year-old man developed a progressive stromal corneal neovascularization in his right eye within eight months of a corneal trauma. At admission, he was receiving latanoprost 0.005% therapy. His topical medications were rearranged: latanoprost was replaced with carteolol hydrochloride 1% twice daily bilaterally and prednisolone acetate 1% was added twice daily in the right eye.

RESULTS

One month later, he presented regression of the corneal neovascularization and an increase in visual acuity.

CONCLUSIONS

Latanoprost, an arachidonic acid derivative, could have directly or indirectly stimulated the corneal neovascularization in this patient with a history of nonpenetrating corneal trauma.

Effects of vitamin D(3)-binding protein-derived macrophage activating factor (GcMAF) on angiogenesis

BACKGROUND

The vitamin D(3)-binding protein (Gc protein)-derived macrophage activating factor (GcMAF) activates tumoricidal macrophages against a variety of cancers indiscriminately. We investigated whether GcMAF also acts as an antiangiogenic factor on endothelial cells.

METHODS

The effects of GcMAF on angiogenic growth factor-induced cell proliferation, chemotaxis, and tube formation were examined in vitro by using cultured endothelial cells (murine IBE cells, porcine PAE cells, and human umbilical vein endothelial cells [HUVECs]) and in vivo by using a mouse cornea micropocket assay. Blocking monoclonal antibodies to CD36, a receptor for the antiangiogenic factor thrombospondin-1, which is also a possible receptor for GcMAF, were used to investigate the mechanism of GcMAF action.

RESULTS

GcMAF inhibited the endothelial cell proliferation, chemotaxis, and tube formation that were all stimulated by fibroblast growth factor-2 (FGF-2), vascular endothelial growth factor-A, or angiopoietin 2. FGF-2-induced neovascularization in murine cornea was also inhibited by GcMAF. Monoclonal antibodies against murine and human CD36 receptor blocked the antiangiogenic action of GcMAF on the angiogenic factor stimulation of endothelial cell chemotaxis.

CONCLUSIONS

In addition to its ability to activate tumoricidal macrophages, GcMAF has direct antiangiogenic effects on endothelial cells independent of tissue origin. The antiangiogenic effects of GcMAF may be mediated through the CD36 receptor.

An experimental study of anti-angiogenesis with recombinant human kringle 5

OBJECTIVE

To investigate the anti-angiogenesis effects of recombinant human kringle 5 (rhk5) eye drops on corneal neovascularization (CNV) in rabbits induced by alkali burn.

METHODS

Forty New Zealand albino rabbits were burned on the central corneas of their right eyes by 1 mol/L NaOH for 60s. Animals were randomly divided into 4 groups, 10 rabbits each group. Then rhk5 eye drops with different concentrations were applied four times daily for four weeks on each group: 5 mg/L in group 1, 10 mg/L in group 2, 20 mg/L in group 3 and carrier solution in group 4 (controls). The occurrence and development of CNV was observed every other day by slit-lamp microscope, and the area of CNV was calculated. Then the rabbits were killed on the 28th day (d), and the corneas were taken for histopathological examinations. Pearson's analysis was used to analyze the correlation between the number of inflammatory cells and the area of CNV.

RESULTS

The occurrence of CNV in group 1 was (3.4 +/- 0.5) d, group 2 (6.8 +/- 0.4) d, group 3 (6.7 +/- 0.7) d and group 4 (3.7 +/- 0.5) d. Significant difference (P < 0.05) in the occurrence time of CNV was found between group 2 and the control. Compared with the control group, the CNV occurrence was significantly delayed in the group treated by 10 mg/L rhk5. No significant difference was found between control group and group 1, and between group 2 and group 3. The CNV areas of group 2 and group 3 were also smaller than the control group (P < 0.05). The area of CNV had close relationship with the retrocorneal membrane and with the number of inflammatory cells (P < 0.05).

CONCLUSION

Topical application of recombinant human rhk5 has prominent effectiveness on the inhibition of angiogenesis induced by alkali burn.

Lipid hydroperoxide induced corneal neovascularization in hyperglycemic rabbits

PURPOSE

To compare the effect of hyperglycemia on corneal neovascularization (NV) induced by linoleic acid hydroperoxide (LHP) in a rabbit model.

METHODS

Male New Zealand rabbits received 80 mg/kg alloxan i.v. and subsequently developed hyperglycemia. Four weeks later, 10 microl of LHP (40 mM) was injected into corneal stroma 5 mm from the superior limbus with a 30 gauge needle. Vessel growth area from the limbal vasculature was measured over a period of 2 weeks and was correlated with plasma levels of insulin, HbA(1c), and corneal vascular endothelial growth factor (VEGF).

RESULTS

Two days after alloxan, blood glucose was increased from 97 +/- 4 mg/dl in the untreated control group to 413 +/- 3 mg/dl. At 24 and 72 hours after LHP injection, VEGF in cornea of hyperglycemic rabbits was elevated 2 to 4 times above that of normoglycemic rabbits. At 14 days after LHP injection, the normoglycemic rabbits vessel growth area measured 2.42 +/- 0.31 mm(2), but in the hyperglycemic group, vessel growth area was significantly increased to 7.96 +/- 2.26 mm(2) (p < 0.05). At the end of the experimental period, HbA(1c) was elevated from 3.9 +/- 0.8 % to 8.4 +/- 0.6 % and insulin was decreased from 440 +/- 123.9 pg/ml to 24 +/- 11.0 pg/ml.

CONCLUSIONS

These data suggest that hyperglycemia may sensitize corneal and vascular endothelial cells, perhaps by glucose derived radicals, which enhance production of additional LHP through endogenous propagation reactions, and raise in turn the concentration of VEGF levels to induce an enhanced, sustained NV response.

[Expression and significance of vascular endothelial growth factor in rat cornea after cautery with alkali]

OBJECTIVE

To investigate the expression of vascular endothelial growth factor (VEGF) in rat cornea after cautery with alkali.

METHODS

In Sprague-Dawley rats, inflammatory corneal neovascularization was induced by cautery with alkali. VEGF was detected in corneal samples at different times by Western-blot, and immunohistochemistry method was used to investigate the distribution of VEGF at rat cornea after cautery with alkali.

RESULTS

The normal rat corneas did not express VEGF. The expression of VEGF increased with time after corneal cautery. The rat corneas were infiltrated by massive inflammatory cells that, especially adjacent to the cautery lesion, showed staining for VEGF.

CONCLUSION

VEGF production by inflammatory cells participates in inflammatory angiogenesis in rat corneas. VEGF has the effects on the induction and supporting of cautery-induced angiogenesis in rat cornea.