Minocycline-loaded nHAP/PLGA microspheres for prevention of injury-related corneal angiogenesis

BACKGROUND

Corneal neovascularization (CoNV) threatens vision by disrupting corneal avascularity, however, current treatments, including pharmacotherapy and surgery, are hindered by limitations in efficacy and adverse effects. Minocycline, known for its anti-inflammatory properties, could suppress CoNV but faces challenges in effective delivery due to the cornea's unique structure. Therefore, in this study a novel drug delivery system using minocycline-loaded nano-hydroxyapatite/poly (lactic-co-glycolic acid) (nHAP/PLGA) nanoparticles was developed to improve treatment outcomes for CoNV.

RESULTS

Ultra-small nHAP was synthesized using high gravity technology, then encapsulated in PLGA by a double emulsion method to form nHAP/PLGA microspheres, attenuating the acidic by-products of PLGA degradation. The MINO@PLGA nanocomplex, featuring sustained release and permeation properties, demonstrated an efficient delivery system for minocycline that significantly inhibited the CoNV area in an alkali-burn model without exhibiting apparent cytotoxicity. On day 14, the in vivo microscope examination and ex vivo CD31 staining corroborated the inhibition of neovascularization, with the significantly smaller CoNV area (29.40% ± 6.55%) in the MINO@PLGA Tid group (three times daily) than that of the control group (86.81% ± 15.71%), the MINO group (72.42% ± 30.15%), and the PLGA group (86.87% ± 14.94%) (p < 0.05). Fluorescein sodium staining show MINO@PLGA treatments, administered once daily (Qd) and three times daily (Tid) demonstrated rapid corneal epithelial healing while the Alkali injury group and the DEX group showed longer healing times (p < 0.05). Additionally, compared to the control group, treatments with dexamethasone, MINO, and MINO@PLGA were associated with an increased expression of TGF-β as evidenced by immunofluorescence, while the levels of pro-inflammatory cytokines IL-1β and TNF-α demonstrated a significant decrease following alkali burn. Safety evaluations, including assessments of renal and hepatic biomarkers, along with H&E staining of major organs, revealed no significant cytotoxicity of the MINO@PLGA nanocomplex in vivo.

CONCLUSIONS

The novel MINO@PLGA nanocomplex, comprising minocycline-loaded nHAP/PLGA microspheres, has shown a substantial capacity for preventing CoNV. This study confirms the complex's ability to downregulate inflammatory pathways, significantly reducing CoNV with minimal cytotoxicity and high biosafety in vivo. Given these findings, MINO@PLGA stands as a highly promising candidate for ocular conditions characterized by CoNV.

ABCB5+ Limbal Epithelial Stem Cells Inhibit Developmental but Promote Inflammatory (Lymph) Angiogenesis While Preventing Corneal Inflammation

The limbus, the vascularized junction between the cornea and conjunctiva, is thought to function as a barrier against corneal neovascularization. However, the exact mechanisms regulating this remain unknown. In this study, the limbal epithelial stem cell (LESC) marker ABCB5 was used to investigate the role of LESCs in corneal neovascularization. In an ABCB5KO model, a mild but significant increase of limbal lymphatic and blood vascular network complexity was observed in developing mice (4 weeks) but not in adult mice. Conversely, when using a cornea suture model, the WT animals exhibited a mild but significant increase in the number of lymphatic vessel sprouts compared to the ABCB5KO, suggesting a contextual anti-lymphangiogenic effect of ABCB5 on the limbal vasculature during development, but a pro-lymphangiogenic effect under inflammatory challenge in adulthood. In addition, conditioned media from ABCB5-positive cultured human limbal epithelial cells (ABCB5+) stimulated human blood and lymphatic endothelial cell proliferation and migration. Finally, a proteomic analysis demonstrated ABCB5+ cells have a pro(lymph)angiogenic as well as an anti-inflammatory profile. These data suggest a novel dual, context-dependent role of ABCB5+ LESCs, inhibiting developmental but promoting inflammatory (lymph)angiogenesis in adulthood and exerting anti-inflammatory effects. These findings are of high clinical relevance in relation to LESC therapy against blindness.

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.

Canonical NF-κB signaling maintains corneal epithelial integrity and prevents corneal aging via retinoic acid

Disorders of the transparent cornea affect millions of people worldwide. However, how to maintain and/or regenerate this organ remains unclear. Here, we show that Rela (encoding a canonical NF-κB subunit) ablation in K14+ corneal epithelial stem cells not only disrupts corneal regeneration but also results in age-dependent epithelial deterioration, which triggers aberrant wound-healing processes including stromal remodeling, neovascularization, epithelial metaplasia, and plaque formation at the central cornea. These anomalies are largely recapitulated in normal mice that age naturally. Mechanistically, Rela deletion suppresses expression of Aldh1a1, an enzyme required for retinoic acid synthesis from vitamin A. Retinoic acid administration blocks development of ocular anomalies in Krt14-Cre; Relaf/f mice and naturally aged mice. Moreover, epithelial metaplasia and plaque formation are preventable by inhibition of angiogenesis. This study thus uncovers the major mechanisms governing corneal maintenance, regeneration, and aging and identifies the NF-κB-retinoic acid pathway as a therapeutic target for corneal disorders.

Protective roles of the TIR/BB-loop mimetic AS-1 in alkali-induced corneal neovascularization by inhibiting ERK phosphorylation

Hydrocinnamoyl-L-valylpyrrolidine (AS-1), a synthetic low-molecule mimetic of myeloid differentiation primary response gene 88 (MyD88), inhibits inflammation by disrupting the interaction between the interleukin-1 receptor (IL-1R) and MyD88. Here, we describe the effects of AS-1 on injury-induced increases in inflammation and neovascularization in mouse corneas. Mice were administered a subconjunctival injection of 8 μL AS-1 diluent before or after corneal alkali burn, followed by evaluation of corneal resurfacing and corneal neovascularization (CNV) by slit-lamp biomicroscopy and clinical assessment. Corneal inflammation was assessed by whole-mount CD45⁺ immunofluorescence staining, and corneal hemangiogenesis and lymphangiogenesis following injury were evaluated by immunostaining for the vascular markers isolectin B4 (IB4) and the lymphatic vascularized marker lymphatic vessel endothelial hyaluronan receptor 1 (LYVE1), respectively. Additionally, corneal tissues were collected to determine the expression of 35 cytokines, and we detected activation of IL-1RI, MyD88, and mitogen-activated protein kinase (MAPK). The results showed that alkali conditions increased the number of CD45⁺ cells and expression of vascular endothelial growth factor (VEGF)-A, VEGF-C, and LYVE1 in corneas, with these levels decreased in the AS-1-treated group. Moreover, AS-1 effectively prevented alkali-induced cytokine production, blocked interactions between IL-1RI and MyD88, and inhibited MAPK activation post-alkali burn. These results indicated that AS-1 prevented alkali-induced corneal hemangiogenesis and lymphangiogenesis by blocking IL-1RI-MyD88 interaction, as well as extracellular signal-regulated kinase phosphorylation, and could be efficacious for the prevention and treatment of corneal alkali burn.

Corneal angiogenic privilege and its failure

The cornea actively maintains its own avascular status to preserve its ultimate optical function. This corneal avascular state is also defined as "corneal angiogenic privilege", which results from a critical and sensitive balance between anti-angiogenic and pro-angiogenic mechanisms. In our review, we aim to explore the complex equilibrium among multiple mediators which prevents neovascularization in the resting cornea, as well as to unveil the evolutive process which leads to corneal angiogenesis in response to different injuries.

Loss of Osteopontin Expression Reduces HSV-1-Induced Corneal Opacity

Purpose

Corneal opacity and neovascularization (NV) are often described as outcomes of severe herpes simplex virus type 1 (HSV-1) infection. The current study investigated the role of colony-stimulating factor 1 receptor (CSF1R)+ cells and soluble factors in the progression of HSV-1-induced corneal NV and opacity.

Methods

MaFIA mice were infected with 500 plaque-forming units of HSV-1 in the cornea following scarification. From day 10 to day 13 post-infection (pi), mice were treated with 40 µg/day of AP20187 (macrophage ablation) or vehicle intraperitoneally. For osteopontin (OPN) neutralization experiments, C57BL/6 mice were infected as above and treated with 2 µg of goat anti-mouse OPN or isotypic control IgG subconjunctivally every 2 days from day 4 to day 12 pi. Mice were euthanized on day 14 pi, and tissue was processed for immunohistochemistry to quantify NV and opacity by confocal microscopy and absorbance or detection of pro- and anti-angiogenic and inflammatory factors and cells by suspension array analysis and flow cytometry, respectively.

Results

In the absence of CSF1R+ cells, HSV-1-induced blood and lymphatic vessel growth was muted. These results correlated with a loss in fibroblast growth factor type 2 (FGF-2) and an increase in OPN expression in the infected cornea. However, a reduction in OPN expression in mice did not alter corneal NV but significantly reduced opacity.

Conclusions

Our data suggest that CSF1R+ cell depletion results in a significant reduction in HSV-1-induced corneal NV that correlates with the loss of FGF-2 expression. A reduction in OPN expression was aligned with a significant drop in opacity associated with reduced corneal collagen disruption.

Controlled release of dexamethasone sodium phosphate with biodegradable nanoparticles for preventing experimental corneal neovascularization

Corneal neovascularization (CNV) leads to the loss of corneal transparency and vision impairment, and can ultimately cause blindness. Topical corticosteroids are the first line treatment for suppressing CNV, but poor ocular bioavailability and rapid clearance of eye drops makes frequent administration necessary. Patient compliance with frequent eye drop application regimens is poor. We developed biodegradable nanoparticles (NP) loaded with dexamethasone sodium phosphate (DSP) using zinc ion bridging, DSP-Zn-NP, with dense coatings of poly(ethylene glycol) (PEG). DSP-Zn-NP were safe and capable of providing sustained delivery of DSP to the front of the eye following subconjunctival (SCT) administration in rats. We reported that a single SCT administration of DSP-Zn-NP prevented suture-induced CNV in rats for two weeks. In contrast, the eyes receiving SCT administration of either saline or DSP solution developed extensive CNV in less than 1 week. SCT administration of DSP-Zn-NP could be an effective strategy in preventing and treating CNV.

Epigallocatechin gallate inhibits corneal neovascularization in ratalkaline burn model

To evaluate the effectiveness of epigallocatechin gallate (EGCG) in inhibiting corneal neovascularization in rat alkaline burn model. Corneal neovascularization model was induced by sodium hydroxide alkaline burn injury in SD rats. Rats were randomly divided into two groups and were given intraperitoneal injection with EGCG or PBS per day for up to 14 days respectively. Corneal inflammation and neovascularization area were assessed on days 3, 7, and 14 after cauterization with digital photographs. Vascular endothelial growth factor (VEGF) and pigment epithelium derived factor (PEDF) mRNA levels were measured by reverse transcription-polymerase chain reaction (qRT-PCR). The nuclear transfactor-Κb (NF-κB) subunit P65 protein was assayed by immunohistochemistry. The differences of corneal inflammation scores between two groups were significant. The area of CNV between two groups had no significant difference on day 3 but have significant difference on days 7 and 14.The PDEF mRNA expression in EGCG group was significantly higher and the expression of VEGF mRNA was lower than those in PBS group. The results of immunohistochemistry showed from day 7, expression of NF-κB P65protein was suppressed considerably in EGCG group. This study demonstrates that EGCG inhibits corneal neovascularization in a rat model induced by alkali burn.

Suppression of VEGF-induced angiogenesis and tumor growth by Eugenia jambolana, Musa paradisiaca, and Coccinia indica extracts

CONTEXT

Abnormal angiogenesis and evasion of apoptosis are hallmarks of cancer. Accordingly, anti-angiogenic and pro-apoptotic therapies are effective strategies for cancer treatment. Medicinal plants, namely, Eugenia jambolana Lam. (Myrtaceae), Musa paradisiaca L. (Musaceae), and Coccinia indica Wight & Arn. (Cucurbitaceae), have not been greatly investigated for their anticancer potential.

OBJECTIVE

We investigated the anti-angiogenic and pro-apoptotic efficacy of ethyl acetate (EA) and n-butanol (NB) extracts of E. jambolana (seeds), EA extracts of M. paradisiaca (roots) and C. indica (leaves) with respect to mammary neoplasia.

MATERIALS AND METHODS

Effect of extracts (2-200 μg/mL) on cytotoxicity and MCF-7, MDA-MB-231 and endothelial cell (EC) proliferation and in vitro angiogenesis were evaluated by MTT, 3[H]thymidine uptake and EC tube formation assays, respectively. In vivo tumour proliferation, VEGF secretion and angiogenesis were assessed using the Ehrlich ascites tumour (EAT) model followed by rat corneal micro-pocket and chicken chorioallantoic membrane (CAM) assays. Apoptosis induction was assessed by morphological and cell cycle analysis.

RESULTS

EA extracts of E. jambolana and M. paradisiaca exhibited the highest cytotoxicity (IC50 25 and 60 μg/mL), inhibited cell proliferation (up to 81%), and tube formation (83% and 76%). In vivo treatment reduced body weight (50%); cell number (16.5- and 14.7-fold), secreted VEGF (∼90%), neoangiogenesis in rat cornea (2.5- and 1.5-fold) and CAM (3- and 1.6-fold) besides EAT cells accumulation in sub-G1 phase (20% and 18.38%), respectively.

DISCUSSION AND CONCLUSION

Considering the potent anti-angiogenic and pro-apoptotic properties, lead molecules from EA extracts of E. jambolana and M. paradisiaca can be developed into anticancer drugs.

MMP14 Cleavage of VEGFR1 in the Cornea Leads to a VEGF-Trap Antiangiogenic Effect

PURPOSE

To determine the possible antiangiogenic effect of metalloproteinase (MMP) 14 cleavage of vascular endothelial growth factor receptor 1 (VEGFR1) in the cornea.

METHODS

Recombinant mouse (rm) VEGFR1 was incubated with various concentrations of recombinant MMP14 to examine proteolysis in vitro. The reaction mixture was analyzed by SDS-PAGE and stained with Coomassie blue. The fragments resulting from rmVEGFR1 cleavage by MMP14 were subjected to Edman degradation, and the amino acid sequences were aligned with rmVEGFR1 sequences. Surface plasmon resonance was used to determine the equilibrium dissociation constant (KD) between MMP14 and rmVEGFR1. The KD value of rmVEGFR1 and the 59.8-kDa cleavage product binding to VEGF-A₁₆₅ was also determined. Cell proliferation assays were performed in the presence of VEGF-A₁₆₅ plus the 59.8-kDa VEGFR1 fragment or VEGF-A₁₆₅ alone.

RESULTS

Matrix metalloproteinase 14 binds and cleaves rmVEGFR1 to produce 59.8-kDa (N-terminal fragment, Ig domains 1-5), 35-kDa (C-terminal fragment containing IgG and His-tag), and 21-kDa (Ig domains 6-7) fragments. The 59.8-kDa fragment showed binding to VEGF-A₁₆₅ and inhibited VEGF-induced endothelial cell mitogenesis.

CONCLUSIONS

Our findings suggest that VEGFR1 cleavage by MMP14 in the cornea leads to a VEGF-trap effect, reducing the proangiogenic effect of VEGF-A₁₆₅, thereby reducing corneal angiogenesis.

[Ursolic acid inhibits corneal graft rejection following orthotopic allograft transplantation in rats]

OBJECTIVE

To investigate the effects of ursolic acid on corneal graft rejection in a rat model of othotopic corneal allograft transplantation.

METHODS

Forty-eight recipient Wistar rats were divided into normal control group with saline treatment (group A), autograft group with saline treatment (group B), SD rat allograft group with saline treatment (group C), and SD rat allograft group with intraperitoneal ursolic acid (UA) treatment group (group D). The rats received saline or UC (20 mg·kg(-1)·d(-1)) treatment for 12 days following othotopic graft transplantation. The grafts were evaluated using the Larkin corneal rejection rating system, and the graft survival was assessed with Kaplan-Meier analysis. On day 14, the grafts were harvested for histological examination, Western blotting, and assessment of expressions of interlukin-2 (IL-2), interferon-γ (IFN-γ), nuclear transcription factor-κB (NF-κB) p65, vascular endothelial growth factor (VEGF) and intercellular adhesion molecule-1 (ICAM-1).

RESULTS

The allograft survival was significantly longer in group D than in group C (29.12±9.58 vs 9.67±2.16 days, P<0.05). UC treatment obviously reduced the expression levels of IL-2, IFN-γ, NF-κBp65, ICAM-1 and VEGF and increased inhibitory kappa B alpha (IκB-α) expression in the grafts, where no obvious inflammatory cell infiltration or corneal neovascularization was found.

CONCLUSION

As a NF-κB inhibitor, ursolic acid can prevent corneal neovascularization and corneal allograft rejection to promote graft survival in rats following orthotopic corneal allograft transplantation.

[Efficacy of epigallocatechin gallate in treatment of alkali burn injury of murine cornea]

OBJECTIVE

To evaluate the efficacy of epigallocatechin gallate (EGCG) in treatment of corneal alkali burn injury in mice.

METHODS

Corneal alkali burn injury was induced by sodium hydroxide method in C57BL/6J mice. The mice with cornea burns were treated intraperitoneally with EGCG solution or phosphate buffer solution (PBS) respectively. The healing of corneal epithelium, the formation of corneal neovascularization (CNV) and the inflammation reaction were assessed by slit -lamp microscopy and histological examination. Expression of vascular endothelial growth factor (VEGF) mRNA and protein in cornea was evaluated by real -time reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry, respectively. Myeloperoxidase (MPO) assay was used to quantitatively evaluate the polymorphonuclear neutrophils (PMNs) infiltration in the corneas.

RESULTS

The healing rate of corneal epithelium in EGCG group was significantly higher than that of PBS group at d1, d3 and d7 after treatment (d1: 41.0%±13.0% vs 23.8%±7.6%; d3: 76.6%±7.5% vs 61.2%±6.8%; d7: 87.8%±8.5% vs 74.0%±9.1%; all P <0.05). The CNV scores and the number of CNV in the corneal sections of EGCG group were significantly lower than those of PBS group at d3, d7 and d14 after treatment (CNV score: d3: 1.1±0.5 vs 6.6±1.0; d7: 1.3±0. 3 vs 8.1±1.0; d14: 0.9±0.2 vs 9.2±1.1; CNV number: d3: 1.68±0.61 vs 2.92±0.95; d7: 4.80±1.36 vs 7.92±1.28; d14: 3.64±0.71 vs 5.88±0.76; all P<0.05) . The expression of VEGF protein at d3 (0.19±0.05 vs 0.45±0.08) and d7 (0.42±0.07 vs 0.84±0.09), the expression of VEGF mRNA at d1, d3 and d7 in EGCG group were significantly lower than those in PBS group (all P <0.05). Compared to PBS group, the inflammatory index at d3 (3.2±0.4 vs 3.7±0.5) and d7 (2.3±0.5 vs 4.0±0.0), the number of PMNs in the corneal sections and the MPO values at d3, d7 and d14 in EGCG group were significantly decreased (PMNs: d3: 34.5±15.7 vs 90.0±28.8; d7: 17.1±11.4 vs 54.9±25.9; d14: 12. 8±4.6 vs 39.0±17.9; all P <0.05).

CONCLUSION

In the murine corneal alkali burn model, intraperitoneal injection of EGCG solution can promote the healing of corneal epithelium, inhibit the formation of CNV and reduce the inflammatory cell infiltration in the corneas.

[Effect of KH902 in inhibiting suture induced corneal neovascularization]

OBJECTIVE

To evaluate the effect of topical KH902 on experimental corneal neovascularization (CNV) in rats.

METHODS

Suture models of CNV were established in 60 adult healthy rats. The rats were randomly divided into 3 groups: Group A (20 rats) were treated with KH902 (KH902 30 mg/mL was injected subconjunctivally once every other day); Group B (20 rats) were treated with dexamethasone (0.1% dexamethasone was injected subconjunctivally once every other day); Group C (20 rats) served as blank control. CNV growth were observed by slitlamp microscopy 3, 7 and 14 d after suture. Medicines were administered 14 d after operations. CNV changes were observed and recorded 1, 7, 14, and 21 d after administration of medicines. VEGF expression in cornea was measured by immunohistochemistry.

RESULTS

No significant differences were found in average areas of CNV between groups at 1 and 7 d after administration of medicines. At 14 and 21 d after administration of medicines, significant differences in average areas of CNV were found between Group A and Group C, and between Group B and Group C (P < 0.01). Maximum expression of VEGF in corneal stroma was observed 14 d after corneal suture. The expression of VEGF decreased with medications, which was associated with neovascularization.

CONCLUSION

Topical use of KH902 inhibits corneal suture-induced CNV in rats without significant adverse corneal effect on eyes.

[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.

Topical Ranibizumab inhibits inflammatory corneal hem- and lymphangiogenesis

PURPOSE

Ranibizumab (Lucentis(®) ) is a Fab-Fragment of a recombinant, humanized, monoclonal VEGF (anti-vascular endothelial growth factor) antibody. This study analyzed the ability of topical Ranibizumab to inhibit lymphangiogenesis in addition to hemangiogenesis after acute corneal inflammation in vivo. In addition, the effect of Ranibizumab on the proliferation of human lymphatic endothelial cells (LECs) and blood endothelial cells (BECs) in vitro was studied.

METHODS

The inhibitory effect of Ranibizumab on LECs and BECs was studied in vitro using a proliferation enzyme-linked immunosorbent assay (ELISA) assay. To study the in vivo effects of Ranibizumab, the mouse model of suture induced inflammatory corneal neovascularization was used. Study mice received topical Ranibizumab as eye drops. After 1 week excised corneas were stained with LYVE-1 and CD31. Hemangiogenesis and lymphangiogenesis were analyzed morphometrically by using a semiautomatic method based on the image analyzing program Cell^F.

RESULTS

An antiproliferative effect of Ranibizumab was seen in vitro on both human BECs and LECs with a significance of p < 0.0001 and p < 0.0004, respectively. In vivo experiments showed that topical application of Ranibizumab significantly inhibits both hemangiogenesis (p = 0.0026) and lymphangiogenesis (p = 0.0026) in the cornea.

CONCLUSION

Ranibizumab is a potent inhibitor of inflammatory corneal hemangiogenesis and lymphangiogenesis in vivo with a direct inhibitory effect on both endothelial cell types in vitro. This study for the first time demonstrates an inhibitory effect of Ranibizumab on lymphatic vessels which could have a wider range of clinical applications.

Inhibition of corneal neovascularization with the combination of bevacizumab and plasmid pigment epithelium-derived factor-synthetic amphiphile INTeraction-18 (p-PEDF-SAINT-18) vector in a rat corneal experimental angiogenesis model

Bevacizumab, a 149-kDa protein, is a recombinant humanized monoclonal antibody to VEGF. PEDF, a 50-kDa glycoprotein, has demonstrated anti-vasopermeability properties. In this study, we demonstrated that the combination of bevacizumab and plasmid pigment epithelium-derived factor-synthetic amphiphile INTeraction-18 (p-PEDF-SAINT-18) has a favorable antiangiogenic effect on corneal NV. Four groups (Group A: 0 μg + 0 μg, B: 0.1 μg + 0.1 μg, C: 1 μg + 1 μg, and D: 10 μg + 10 μg) of bevacizumab + p-PEDF-SAINT-18 were prepared and implanted into the rat subconjunctival substantia propria 1.5 mm from the limbus on the temporal side. Then, 1 μg of p-bFGF-SAINT-18 was prepared and implanted into the rat corneal stroma 1.5 mm from the limbus on the same side. The inhibition of NV was observed and quantified from days 1 to 60. Biomicroscopic examination, western blot analysis and immunohistochemistry were used to analyze the 18-kDa bFGF, 50-kDa PEDF and VEGF protein expression. No inhibition activity for normal limbal vessels was noted. Subconjunctival injection with the combination of bevacizumab and p-PEDF-SAINT-18 successfully inhibited corneal NV. The bFGF and PEDF genes were successfully expressed as shown by western blot analysis, and a mild immune response to HLA-DR was shown by immunohistochemistry. We concluded that the combination of bevacizumab and p-PEDF-SAINT-18 may have more potent and prolonged antiangiogenic effects, making it possible to reduce the frequency of subconjunctival bevacizumab administration combined with a relatively safe profile and low toxicity.

Blockade of the intermediate-conductance Ca(2+)-activated K+ channel inhibits the angiogenesis induced by epidermal growth factor in the treatment of corneal alkali burn

Epidermal growth factor (EGF) is used to treat alkali-burned corneas. However, EGF-induced corneal angiogenesis, which is currently untreatable, is a side effect of this therapy. We therefore explored the role of the intermediate-conductance Ca(2+)-activated K(+) channel (KCa3.1) in EGF-induced angiogenesis and tested whether KCa3.1 blockade can suppress EGF-induced corneal angiogenesis. The proliferation, migration and tube formation of HUVECs (human umbilical vein endothelial cells) in response to EGF, the MEK inhibitor PD98059 and the KCa3.1 inhibitor TRAM-34 were analyzed in vitro via MTT, cell counting, scratch and tube formation assays. The protein and mRNA levels of KCa3.1, phosphorylated-ERK (P-ERK), total-ERK (T-ERK), cyclin-dependent kinase 4 (CDK4), vimentin and MMP-2 were assessed via western blotting and RT-PCR. KCa3.1 and vimentin expression were also detected through immunofluorescence staining. Flow cytometry was performed to examine the cell cycle. Further, an in vivo murine alkali-burned cornea model was developed and treated with EGF and TRAM-34 eye drops to analyze the effect of these treatments on corneal healing and angiogenesis. The corneas were also analyzed by histological staining. The in vitro results showed that EGF induces the upregulation of KCa3.1 and P-ERK in HUVECs and that this upregulation is suppressed by PD98059. EGF stimulates proliferation, migration and tube formation in HUVECs, and this effect can be suppressed by TRAM-34. TRAM-34 also arrests HUVECs in the G1 phase of the cell cycle and downregulates CDK4, vimentin and MMP-2 in these cells. The in vivo results indicated that TRAM-34 suppresses EGF-induced corneal angiogenesis without affecting EGF-induced corneal wound healing. In summary, the upregulation of KCa3.1 may be crucial for EGF-induced angiogenesis through the MAPK/ERK signaling pathway. Thus, KCa3.1 may be a potential target for the treatment of EGF-induced corneal angiogenesis.

Inhibition of ocular neovascularization by a novel peptide derived from human placenta growth factor-1

PURPOSE

To evaluate the effect of ZY1, a novel 21-amino acid peptide from human placenta growth factor-1 (PlGF-1), against ocular neovascularization, and to study its possible toxicity to the retina and the underlying mechanism of antiangiogenic effect.

METHODS

MTS assays, a modified Boyden chamber and Matrigel(™) were used to evaluate the effect of ZY1 on the proliferation, migration and tube formation of RF/6A rhesus macaque choroid-retina endothelial cells induced by vascular endothelial growth factor (VEGF) in vitro. The antiangiogenic effect of ZY1 was also studied with corneal micropocket angiogenesis assays and oxygen-induced retinopathy (OIR) assays in mice. Electrophysiological tests and histological examinations were used to study the possible toxicity of ZY1 against mouse neuroretina. Competitive ELISA and Western blotting were performed to elucidate the underlying mechanism of ZY1.

RESULTS

ZY1 inhibited VEGF-induced RF/6A proliferation, migration and tube formation. It also inhibited ocular neovascularization when applied to the corneal micropocket angiogenesis assays and OIR assays in mice. Electrophysiological tests and histological examinations revealed no evident functional or morphologic abnormalities in mouse neuroretina after ZY1 injection. ZY1 competed for binding to VEGFR-1 against PlGF and VEGF and inhibited VEGFR-1/ERK/AKT activation.

CONCLUSION

 It is concluded that the novel peptide ZY1 is an effective inhibitor of ocular pathologic angiogenesis and may provide a promising alternative for ocular antiangiogenic therapy.

[Recombinant fragment of pigment epithelium-derived factor (44-77) prevents pathological corneal neovascularization]

Pigment epithelium-derived factor (PEDF), a 50 kDa secreted glycoprotein, is among the most potent endogenous inhibitors of angiogenesis. PEDF-derived fragment (44-77) possesses antiangiogenic properties of the full-sized protein and is a potential drug candidate for the treatment of ocular neovascular diseases. In this study we propose an efficient scalable biotechnological method for the production of PEDF (44-77) as part of a fusion protein with SspDnaB intein. The fusion protein was obtained in bacterial E. coli cells in the form of inclusion bodies, solubilized and subjected to autocatalytic cleavage with the release of PEDF (44-77) (yield, 77%). The target peptide was separated from the intein using tangential ultrafiltration. The final purification of PEDF (44-77) was performed by reversed-phase HPLC. The yield of the target peptide (purity, 99%) was 65 mg per 1 liter of culture. Antiangiogenic activity of the obtained peptide was studied in vitro using murine endothelial cells SVEC-4-10. PEDF (44-77) suppressed proliferation of endothelial cells by 53% and inhibited endothelial cell tube formation at the concentration of 1 nM. The ability of the recombinant PEDF (44-77) to block initial stages of angiogenesis was demonstrated using the model of rabbit corneal neovascularization.

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.

Effect of topical azithromycin on corneal innate immune responses

PURPOSE

To determine the effect of azithromycin (AZM) in a murine model of corneal inflammation.

METHODS

The effect of topical AZM was studied in murine corneal inflammation. Corneal inflammation was induced by thermal cautery in BALB/c mice. Leukocyte infiltration at different time points was analyzed by flow cytometry. At set time points, real-time polymerase chain reaction was performed to quantify the expression of different inflammatory cytokine transcript in the cornea. Corneal samples were analyzed immunohistochemically for the expression of intercellular adhesion molecule-1 (ICAM-1). Corneal neovascularization (CNV) was induced by micropellet (VEGF-A) placement. Mice were then treated topically with either AZM or vehicle. CNV was evaluated morphometrically.

RESULTS

Eyes receiving AZM showed a significant decrease in corneal infiltration compared with the vehicle-treated group. AZM also significantly decreased messenger RNA expression levels of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) and ICAM-1 in the cornea. There was no significant difference in CNV between the AZM- and vehicle-treated groups.

CONCLUSIONS

After an inflammatory insult, topical AZM significantly reduced leukocyte infiltration into the cornea. This was further supported by an associated decrease in expression of IL-1β, TNF-α, and ICAM-1 in the cornea, indicating AZM may have a potential anti-inflammatory effect on corneal inflammation.

[VEGF short hairpin RNA expression plasmid blocks VEGF expression in rat vascular endothelial cell and inhibits rat corneal neovascularization]

OBJECTIVE

To investigate RNA interference in rat corneal neovascularization and vascular endothelial cells of vascular endothelial growth factor expression and its mechanism.

METHODS

In empirical study short hairpin RNA (shRNA) targeting VEGF mRNA was designed and synthesized and VEGF shRNA eukaryotic plasmids were transfected into EC with Lipofectamine 2000 transfection system. Expression of VEGF mRNA and protein in transfected cells was detected by RT-PCR and Western blot. Twenty SD rats were randomized into two groups by randomly Design, experimental group were 10 and 10 in the control group. CNV was induced in vivo by alkaline cauterization of the central cornea, the rats received subconjunctival injection of VEGF shRNA3 plasmid. Then corneal neovascularization was evaluated with microscope. After seven days, VEGF mRNA and protein was determined by RT-PCR and Western blot respectively.

RESULTS

VEGF shRNA expression plasmids were successfully constructed and identified by restriction enzyme and sequence analysis. VEGF expression was down regulated by VEGF shRNA1, 2, 3 plasmids, and VEGF shRNA3 plasmid showed stronger inhibitory effect. The inhibitory effects of VEGF mRNA and protein are 68.92% and 66.22%. At the 3, 5 and 7 days after alkali cauterization, the CNV length of the experimental group was obviously decreased comparing with the control group, the difference between two groups has statistics meaning (F=402.700, P=0.000); the CNV area of the experimental group was also obviously decreased comparing with the control group, the difference between two groups has statistics meaning (F=402.700, P=0.000); the VEGF mRNA and protein in corneas was also decreased, the inhibitory effects of which are 41.84% and 41.86%.

CONCLUSIONS

RNAi significantly suppresses expression of VEGF in rat EC in vitro. In vivo, subconjunctival delivery of VEGF shRNA3 plasmid suppresses injury-induced VEGF expression and CNV.

Parstatin suppresses ocular neovascularization and inflammation

PURPOSE

Parstatin is a 41-mer peptide formed by proteolytic cleavage on activation of the PAR1 receptor. The authors recently showed that parstatin is a potent inhibitor of angiogenesis. The purpose of the present study was to evaluate the therapeutic effect of parstatin on ocular neovascularization.

METHODS

Choroidal neovascularization was generated in mice using laser-induced rupture of Bruch's membrane and was assessed after 14 days after perfusion of FITC-dextran. Oxygen-induced retinal neovascularization was established in neonatal mice by exposing them to 75% O(2) at postnatal day (P)7 for 5 days and then placing them in room air for 5 days. Evaluation was performed on P17 after staining with anti-mouse PECAM-1. The effect of parstatin was tested after intravitreal administration. The effects of subconjunctival-injected parstatin on corneal neovascularization and inflammation in rats were assessed 7 days after chemical burn-induced corneal neovascularization. Retinal leukostasis in mice was assessed after perfusion with FITC-conjugated concanavalin A.

RESULTS

Parstatin potently inhibited choroidal neovascularization with an IC(50) of approximately 3 μg and a maximum inhibition of 59% at 10 μg. Parstatin suppressed retinal neovascularization with maximum inhibition of 60% at 3 μg. Ten-microgram and 30-μg doses appeared to be toxic to the neonatal retina. Subconjunctival parstatin inhibited corneal neovascularization, with 200 μg the most effective dose (59% inhibition). In addition, parstatin significantly inhibited corneal inflammation and VEGF-induced retinal leukostasis. In all models tested, scrambled parstatin was without any significant effect.

CONCLUSIONS

Parstatin is a potent antiangiogenic agent of ocular neovascularization and may have clinical potential in the treatment of angiogenesis-related ocular disorders.

Inhibition of corneal neovascularization by topical bevacizumab (Anti-VEGF) and Sunitinib (Anti-VEGF and Anti-PDGF) in an animal model

PURPOSE

To evaluate the effects of topically applied bevacizumab and sunitinib on experimentally induced corneal neovascularization.

DESIGN

Experimental animal study.

METHODS

Thirty-six New Zealand rabbits were involved. One eye per rabbit was used. Corneal neovascularization was induced by placing 5 silk sutures in the upper cornea. Rabbits were randomized to 1 of 3 groups (12 rabbits each): Group 1 received saline 0.9%, Group 2 bevacizumab 5 mg/mL, and Group 3 sunitinib 0.5 mg/mL. All treatments were administered 3 times daily for 14 days. Photographs were taken on a slit lamp on days 7 and 14, and angiographic photographs were taken on day 14. The area of neovascularization was measured in mm(2), percentage of the total corneal area, and percentage of the corneal surface covered by sutures.

RESULTS

On day 14, corneal neovascularization area in Group 1 (25.92 ± 5.08 mm(2), 18.78% ± 3.5% of corneal surface, 105.59% ± 18.9% of corneal surface with sutures) was larger than in Groups 2 (18.52 ± 7.94 mm(2), 13.67% ± 5.8%, 76.35% ± 33.2%) (1-way analysis of variance, P = .041) and 3 (4.57 ± 2.32 mm(2), 3.40% ± 1.7%, 18.94% ± 9.2%)(P < .001). Neovascularization in Group 2 was larger than in Group 3 (P < .001). Compared to saline, corneal neovascularization was inhibited 28.5% by bevacizumab and 82.3% by sunitinib. Sunitinib settled on the iris.

CONCLUSIONS

Topical administration of both bevacizumab and sunitinib inhibits corneal neovascularization in rabbits. But vascular endothelial growth factor (VEGF) pathway blockade by bevacizumab was not sufficient for a profound inhibition. Blocking both VEGF and platelet-derived growth factor pathways using sunitinib was 3-fold more effective.

Inhibition of mouse alkali burn induced-corneal neovascularization by recombinant adenovirus encoding human vasohibin-1

PURPOSE

To evaluate the activity of recombinant adenovirus encoding human vasohibin-1 (Ad-Vasohibin-1) on mouse corneal neovasularization induced by alkali burn.

METHODS

For the treatment group, 50 mice each received subconjunctival injection (5 microl) of 10(9) plaque forming units of replication-defective Ad-Vasohibin-1. Control group mice received the same dosage of blank adenoviral vector (AdNull). Five days after injection, corneal neovascularization (CNV) was induced by placing 2.5 microl of 0.1 M NaOH on the right cornea for 30 s. Subsequently, CNV was observed and photographed every 3 days for a total duration of 9 days after the alkali burn. The percentage of neovascularized area was measured and compared with the AdNull control. The expression of human vasohibin-1 protein was detected by immunohistochemistry and western blotting at 5, 8, and 14 days after injection. The mRNA expression levels of murine vascular endothelial growth factor (Vegf), VEGF receptor 1 and 2 (Vegfr1, Vegfr2), and vasohibin-1 (Vash1) were analyzed and compared by real time quantitative reverse-transcription polymerase chain reaction.

RESULTS

The percentage of neovascularized area within the cornea was significantly reduced in mice treated with Ad-Vasohibin-1 compared to mice treated with AdNull at every time point after alkali-induced injury (7.11%+/-3.91% and 15.48%+/-1.79% of corneal area in the treatment and control groups, respectively, on day 3; 31.64%+/-4.71% and 43.93%+/-6.15% on day 6, and 45.02%+/-9.98% and 66.24%+/-7.17% on day 9, all p<0.001). Human vasohibin-1 protein was detected at the injection sites on day 3 after corneal burn and was highly expressed in the central subepithelial stroma and co-localized with neovascularized vessels within the alkali-treated cornea on day 6. On day 9, the peripheral cornea exhibited a similar staining pattern as the central cornea, but a more intense vasohibin-1 immunostaining signal was detected in the deep stroma. Some of the vasohibin-1 stain signal diffused into the frontal and deep stroma of the central cornea and was not co-localized with new vessels. By contrast, in mice injected with AdNull or normal corneas, no vasohibin-1 stain signal was detected within the corneas. Vasohibin-1 protein expression within treated corneas was also further confirmed by western blotting on day 5. Expression appeared to peak by day 8 and was maintained at high levels until day 14. However, Vasohibin-1 protein was not detected in the corneas of normal mice or mice treated with AdNull. Real-time quantitative reverse-transcription polymerase chain reaction analysis showed that expression of Vegfr2 and endogenous Vash1 mRNA were significantly decreased in the treatment versus control group (t(1)=-2.161, p(1)=0.047; t(2)=-2.236, p(2)=0.041). In contrast, there were no significant differences in Vegf and Vegfr1 mRNA expression levels between the treatment and control groups (p>0.05 for both).

CONCLUSIONS

Subconjunctival injection of Ad-Vasohibin-1 significantly reduces corneal neovascularization in alkali-treated mouse corneas. This effect of anti-neovascularization may be related to the downregulation of Vegfr2 expression.

[Initial clinical observation of tissue-engineered epithelium transplantation for treating corneal conjunctivalization caused by burn]

OBJECTIVE

To study the therapeutic results of tissue-engineered epithelium transplantation for corneal conjunctivalization caused by chemical and thermal burns.

METHODS

Clinical case series. From December 2007 to May 2008, in Beijing Tongren Eye Center and Beijing Tongren Hospital, six patients (6 eyes) with chemical or thermal burn injury were treated by auto-transplantation of limbus stem cells cultured on fibrin gel membrane and followed up 6 to 12 months for clinical evaluation. The clinical outcomes included visual acuity, corneal clarity and neovascularization.

RESULTS

In 5 of 6 eyes, the postoperative visual acuity was slightly improved. During followed up period, the corneal new-forming vessels were lessen than before, but one eye showed neovascularization recurrent. The corneal clarity in 5 eyes was improved. 4 eyes were covered with transparent epithelium, 2 eyes showed light corneal opacity.

CONCLUSION

The ocular surface condition of corneal conjunctivalization caused by corneal burn could be improved in short period by tissue-engineered epithelium transplantation.

Inhibition of corneal neovascularization with plasmid pigment epithelium-derived factor (p-PEDF) delivered by synthetic amphiphile INTeraction-18 (SAINT-18) vector in an experimental model of rat corneal angiogenesis

The use of Synthetic Amphiphile INTeraction-18 (SAINT-18) carrying plasmid pigment epithelium-derived factor (p-PEDF) as an anti-angiogenesis strategy to treat corneal neovascularization in a rat model was evaluated. Four partially dried forms (Group A: 0 microg, B: 0.1 microg, C: 1 microg, D: 10 microg) of a p-PEDF-SAINT-18 were prepared and implanted into the rat subconjunctival substantia propria 1.5 mm from the limbus at the temporal side. The 1 microg of plasmid-basic fibroblast growth factor--SAINT-18 (p-bFGF-SAINT-18) (1 microg) was prepared and implanted into the rat corneal stroma 1.5 mm from the limbus on the same side. Inhibition of neovascularization was observed and quantified from day 1 to day 60. PEDF (50-kDa) and bFGF (18-kDa) protein expression were analyzed by biomicroscopic examination, Western blot analysis, and immunohistochemistry. Gene expression in corneal and conjunctival tissue was observed as early as 3 days after gene transfer and stably lasted for over 3 months with minimal immune reaction. Subconjunctival injection of a highly efficient p-PEDF-SAINT-18 successfully inhibited corneal neovascularization. Successful gene expression of bFGF, PEDF and a mild immune response of HLA-DR were shown by immunohistochemistry staining. We concluded that SAINT-18 was capable of directly delivering genes to the ocular surface by way of subconjunctival injection, and delivered sustained, high levels of gene expression in vivo to inhibit angiogenesis.

Antiangiogenic properties of fasudil, a potent Rho-Kinase inhibitor

PURPOSE

Vascular endothelial growth factor (VEGF) plays a pivotal role in pathological angiogenesis. In this study, we addressed the therapeutic potential of fasudil, a potent Rho-kinase inhibitor, for VEGF-elicited angiogenesis and also for the intracellular signalings induced by VEGF.

METHODS

In vitro, the inhibitory effects of fasudil on the VEGF-dependent VEGF receptor 2 (VEFGR2 or KDR), extracellular signal-related kinase (ERK) 1/2, Akt and myosin light chain (MLC) phosphorylation, as well as on the migration and proliferation of bovine retinal microvascular endothelial cells (BRECs) were analyzed with Western blotting, [3H]-thymidine uptake, and modified Boyden chamber assay. VEGF-elicited in vivo angiogenesis was analyzed with a mouse corneal micropocket assay coembedded with or without fasudil.

RESULTS

VEGF caused enhanced MLC phosphorylation of BRECs, which was almost completely attenuated by 10microM fasudil. VEGF-dependent phosphorylation of ERK1/2 and Akt were also partially but significantly attenuated by treatment with fasudil without affecting VEGFR2 (KDR) phosphorylation. Moreover, both VEGF-induced [3H]-thymidine uptake and the migration of BRECs were significantly inhibited in the presence of fasudil. Finally, VEGF-elicited angiogenesis in the corneal micropocket assay was potently attenuated by coembedding with fasudil (P < 0.01).

CONCLUSIONS

These findings indicate that fasudil might have a therapeutic potential for ocular angiogenic diseases. The antiangiogenic effect of fasudil appears to be mediated through the blockade not only of Rho-kinase signaling but also of ERK and Akt signaling.

Subconjunctival injection of recombinant AAV-angiostatin ameliorates alkali burn induced corneal angiogenesis

PURPOSE

To evaluate the effect of subconjunctival injection of recombinant adeno-associated virus (rAAV)-angiostatin in alkali burn-induced corneal angiogenesis.

METHODS

Adeno-associated viral vector-mediated gene delivery into extraocular tissue was determined by fluorescent microscopy three weeks after subconjunctival injection of viral vector expressing green fluorescent protein (rAAV-GFP). Subconjunctival injection of recombinant adeno-associated viral vector expressing human angiostatin (rAAV-angiostatin) and blank rAAV viral vector (control) was performed in the left eye of male Sprague-Dawley rats (n=6). Alkaline induction of corneal neovascularization (NV) was performed three weeks later. Corneal NV regression was analyzed 7-14 days after alkali burn with slit lamp and digital pictures. Transgenic expression of angiostatin in the cornea, conjunctiva, retina, and muscle insertions was confirmed by reverse-transcriptase polymerase chain reaction (RT-PCR).

RESULTS

Transgenic GFP gene expression was detected mainly in the muscle fibers at the extraocular muscle (EOM) insertions after subconjunctival injection. The area of corneal neovascularization was significantly lower in eyes injected with rAAV-angiostatin (p<0.01) than in eyes injected with the control virus. RT-PCR demonstrated that the angiostatin gene expression was highly detectable in muscle fibers and not detectable in the conjunctiva, cornea, and retina.

CONCLUSIONS

Subconjunctival injection of rAAV-angiostatin reduced alkali burn-induced corneal angiogenesis. We proved the concept that ocular gene therapy by subconjunctival injection of adenovirus-associated gene transfer of angiogenesis inhibitors can be a simple and safe treatment modality that can achieve therapeutic levels and long lasting effects in the treatment of corneal NV induced by ocular surface disorders.

Inhibitory effects of topical thymoquinone on corneal neovascularization

PURPOSE

Thymoquinone, one of the biologically active components of black seed oil, has anti-inflammatory and antioxidant properties. We aimed to study the effect of thymoquinone on corneal neovascularization in rats and to compare its efficacy with that of triamcinolone acetonide.

METHODS

Chemical cauterization of the cornea was performed with silver nitrate/potassium nitrate sticks in 40 eyes in 40 rats. An examiner blinded to the experiments scored the intensity of the cauterization. Topical instillation of thymoquinone 0.1%, thymoquinone 0.4%, and triamcinolone acetonide was continued for 7 days. The inhibitory effects of the drugs on corneal neovascularization were tested and compared with each other and with controls with a computer program that evaluates percent areas of cornea covered by neovascularization.

RESULTS

The means of percent area of corneal neovascularization in the thymoquinone 0.1%, thymoquinone 0.4%, triamcinolone acetonide, and control groups were 60.1%, 45%, 46%, and 72%, respectively. The inhibitory effect of thymoquinone 0.4% was found to be equal to that of triamcinolone acetonide (P = 0.87). The thymoquinone 0.4% and triamcinolone groups were different from the thymoquinone 0.1% and control groups (P < 0.05). There was also a significant difference between the percent area of corneal neovascularization in the thymoquinone 0.1% group and that of the controls (P < 0.05). The mean burn stimulus intensities were not different among the groups (P = 0.54).

CONCLUSIONS

Thymoquinone was shown to have an inhibitory effect, comparable with that of triamcinolone, on corneal neovascularization in this rat model. However, thymoquinone decreased corneal neovascularization in a dose-dependent manner.

Very late antigen 1 blockade markedly promotes survival of corneal allografts

OBJECTIVE

To investigate the role of very late antigen 1 (VLA-1) (also known as integrin receptor alpha(1)beta(1)) in corneal transplantation inflammation and allograft survival.

METHODS

Cell infiltration and vasculogenesis (both angiogenesis and lymphangiogenesis) associated with allodisparate corneal transplantation were assessed in VLA-1-deficient conditions and controls by immunofluorescent microscopic studies. Corneal allograft survival was also assessed after anti-VLA-1 antibody treatment and in VLA-1 knockout recipient mice.

RESULTS

Anti-VLA-1 antibody treatment leads to a profound reduction in the granulocytic, monocytic, and T-cell infiltration after corneal transplantation. In addition, corneal angiogenesis and lymphangiogenesis were both significantly suppressed in VLA-1 knockout mice. Remarkably, universal graft survival was observed in both anti-VLA-1 antibody treatment and knockout mice.

CONCLUSIONS

Very late antigen 1 blockade markedly reduces inflammation and inflammation-induced tissue responses, including vasculogenic responses, associated with corneal transplantation and promotes allograft survival.

CLINICAL RELEVANCE

These studies offer insights into important integrin-mediated mechanisms of corneal transplant-related inflammation and provide possible new integrin-based immunotherapies for transplant rejection.

Endogenous TNFα Suppression of Neovascularization in Corneal Stroma in Mice

PURPOSE

To examine the role of tumor necrosis factor alpha (TNFalpha) in stromal neovascularization in injured cornea in vivo and in cytokine-enhanced vessel-like endothelial cell tube formation in vitro.

METHODS

An in vitro model of angiogenesis was used to examine the roles of TNFalpha on tube formation by human umbilical vein endothelial cells (HUVECs) cocultured with fibroblasts on induction by transforming growth factor beta1 (TGFbeta1) and vascular endothelial growth factor (VEGF). Central cauterization was used to induce stromal neovascularization in corneas of wild-type (WT) and TNFalpha-null (Tnfalpha(-/-)) mice. At 7, 14, or 21 days of injury, experimental mice were killed, and the eyes were enucleated and subjected to histologic and immunohistochemical examination and real-time reverse transcription-polymerase chain reaction.

RESULTS

HUVECs formed a vessel-like tube structure on the fibroblast feeder layer. Adding TGFbeta1, VEGF, or both augmented vessel-like tube formation by HUVECs cocultured with fibroblasts. Adding TNFalpha (5 ng/mL) completely abolished the formation of tube-like structures despite the presence or absence of TGFbeta1 or VEGF in coculture. In vivo, cauterization of the central cornea induced the formation of CD31(+) new vessels surrounding the limbus in WT mice. More prominent central stromal neovascularization accompanied by increased expression of TGFbeta1 and VEGF was found in Tnfalpha(-/-) mice compared with WT mice.

CONCLUSIONS

In addition to inhibiting TGFbeta1 and VEGF expression by fibroblasts, endogenous TNFalpha may counter the induction effects of TGFbeta1 and VEGF on vascular endothelial cells and may block neovascularization.

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.

Nanoparticles sustain expression of Flt intraceptors in the cornea and inhibit injury-induced corneal angiogenesis

PURPOSE

To determine whether long-term expression of intraceptors can be achieved using plasmid albumin nanoparticles and whether nanoparticles can inhibit and cause regression of murine corneal neovascularization induced by mechanical-chemical trauma.

METHODS

Albumin nanoparticles encapsulating pCMV.Flt23K were developed as a lyophilized product that is easily redispersed in an aqueous medium. Nanoparticles were injected into the corneas of uninjured BALB/c mice and observed for toxicity for 3 weeks. Entry of nanoparticles into corneal cells was demonstrated through transmission electron microscopy and confocal imaging. Naked pCMV.Flt23K, nanoparticles encapsulating pCMV.Flt23K, or empty pCMV nanoparticles were injected into uninjured mouse corneas. These corneas were subjected to mechanical alkali trauma 3 weeks after injection.

RESULTS

Nanoparticles were nontoxic to the cornea and entered into corneal keratocyte cytoplasm. They persisted for at least 4 weeks in the cornea, expressed effective intraceptor levels for at least 5 weeks, and reduced corneal neovascularization by approximately 40% (P = 0.035) at 5 weeks after administration.

CONCLUSIONS

Albumin nanoparticles are not toxic to the cornea and can express intraceptors for extended periods that are effective in suppressing injury-induced corneal neovascularization.

Inhibition of angiogenesis induced by cerebral arteriovenous malformations using Gamma Knife irradiation

Object

The authors studied the effect of Gamma Knife irradiation on angiogenesis induced by cerebral arteriovenous malformation (AVM) tissues implanted in the corneas of rats.

Methods

Ten AVM specimens obtained from tissue resections performed at Marmara University between 1998 and 2004 were used. A uniform amount of tissue was implanted into the micropocket between the two epithelial layers of the cornea. Gamma Knife irradiation was applied with dose prescriptions of 15 or 30 Gy to one cornea at 100% iso-dose. Dosing was adjusted so that the implanted cornea of one eye received 1.5 Gy when 15 Gy was applied to the other cornea. Similarly, one cornea received 3 Gy when 30 Gy was applied to the other cornea. Angiogenic activity was graded daily by biomicroscopic observations. Forty-eight other rats were used for microvessel counting and vascularendothelial growth factor (VEGF) staining portions of the experiment. Micropieces of the specimens were again used for corneal implantation. Rats from each group were killed on Days 5, 10, 15, and 20, and four corneas from each group were examined.

Gamma Knife irradiation dose dependently decreased AVM-induced neovascularization in the rat cornea as determined by biomicroscopic grading of angiogenesis, microvessel count, and VEGF expression.

Conclusions

The results suggest that Gamma Knife irradiation inhibits angiogenesis induced by AVM tissue in the cornea angiogenesis model. The data are not directly related to understanding how Gamma Knife irradiation occludes existing AVM vasculature, but to understanding why properly treated AVMs do not recur and do not show neovascularization after Gamma Knife irradiation.

Effects of topical administration of 12-methyl tetradecanoic acid (12-MTA) on the development of corneal angiogenesis

Corneal vascularisation is a potentially devastating occurrence that can cause blindness. Currently, treatments for this condition are limited. In these studies, we have investigated a novel inhibitor of angiogenesis, 12-methyl tetradecanoic acid (12-MTA), to treat corneal vascularisation in mouse models of corneal alkali injury and corneal Pseudomonas aeruginosa infection. The effectiveness of 12-MTA was compared to treatment with dexamethasone. 12-MTA was found to be at least as effective as dexamethasone in reducing the angiogenesis that occurs following alkali injury or P. aeruginosa infection of the cornea. The major effect of both 12-MTA and dexamethasone in these models was to reduce the linear incursion of new blood vessels into the central cornea. A significantly better result was obtained at 14 days post-alkali injury when treatment was not delayed. A major advantage of treatment of alkali injury with 12-MTA compared to that with dexamethasone was the finding that there was a 5-fold less level of PMN infiltration and no persistent epithelial defects in corneas treated with 12-MTA compared to 50% of those treated with dexamethasone. Our studies indicate that 12-MTA may provide clinically significant advantages over conventional steroids for the treatment of vessel growth in the cornea.

Unique Homologous siRNA Blocks Hypoxia-Induced VEGF Upregulation in Human Corneal Cells and Inhibits and Regresses Murine Corneal Neovascularization

PURPOSE

To evaluate the results of amniotic membrane transplantation (AMT) for ocular surface reconstruction in chemical and thermal injuries.

METHODS

Retrospective review of case records of patients who had undergone AMT for chemical injuries (January 1998 to May 2001).

RESULTS

Seventy two eyes of 69 patients were studied of which 24 were acute cases (median-2 days, range, 1-20 days) and 48 were chronic cases (median-12.4 months, range, 1.02-95.8 months). Mean age was 22.4 years (SD +/- 13.34 years) and average follow up duration was 7.8 months (SD +/- 7.1). Main clinical findings were symblephara (52.8%), corneal vascularization (51.3%), conjunctivalization (45.8%), Limbal ischemia (45.8%), Limbal stem cell deficiency (55.5%) and epithelial defect (48.6%). 18 cases were due to acid injuries (5 acute, 13 chronic), 52 were due to alkali (18 acute and 34 chronic) and 2 cases were due to thermal burns (1 each acute and chronic). Overall success rate was 87.5% in acute cases and 72.9% in chronic cases. Indication-wise success rates were 94.3% for epithelial defect healing, 88.2% for symptomatic relief, 59.7% for ocular surface reconstruction, and 55% for improving limbal stem cell function. Success was not achieved in any outcome measure in 1/24 (4.2%) in acute group and 6/48 (12.5%) in chronic group.

CONCLUSION

AMT helps in ocular surface reconstruction, promotes rapid epithelial healing and partially restores limbal stem cell function. It can be considered as an effective modality for the ocular surface restoration in chemical and thermal injuries in selected cases. Success rates in acute and chronic cases are comparable.

Effect of a Dihydrobenzofuran Derivative on Lipid Hydroperoxide-Induced Rabbit Corneal Neovascularization

The aim of this study was to investigate the effect of A-3922, a dihydrobenzofuran derivative, on linoleic acid hydroperoxide (LHP)-induced corneal neovascularization (NV) in a rabbit model. Male New Zealand rabbits received intraperitoneal (i.p.) injections of 10 or 30 mg/kg per day A-3922 or its vehicle as control for 3 days. One day after i.p. injections, LHP was injected with a 30-gauge needle into the corneal stroma of the superior quadrant 4.5-mm below the limbus. Photographs of the vessels were taken for digital analysis with a surgical microscope. Vascular endothelial growth factor (VEGF) was measured using an immunoassay kit, and matrix metalloproteinase (MMP)-9 was measured by gelatin zymography in corneal samples. At 7 days post-LHP injection, the total vessel length was 26.7 +/- 3.8 mm in the control animals (n = 8), 16.1 +/- 0.8 mm in the A-3922 (10 mg/kg)-treated group (n = 5), and 11.4 +/- 2.1 mm in the 30 mg/kg group (n = 8, P<0.01 vs control), respectively. After LHP injection, the content of VEGF and MMP-9 activity were increased in the superior cornea, but these were not influenced by A-3922 treatments. These results indicate that LHP-induced corneal NV is inhibited by treatment with A-3922 and therefore may represent a potential pharmacological intervention for ocular neovascularization disorders.

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.

Immunological Characteristics of Amniotic Epithelium

We review recent experimental evidence of the immunosuppressive and immunogenic potential of amniotic epithelial cells. Since cryopreserved amniotic membrane (AM) has been used in clinical applications, much research has focused on the beneficial effects of amniotic stromal matrix rather than on the function of viable amniotic cells. However, viable human amniotic epithelial cells (HAECs) have been shown to elicit beneficial effects on secretion of anti-inflammatory factors. Topical application of culture supernatant from HAECs leads to profound suppression of suture-induced neovascularization in cornea and fewer major histocompatibility complex (MHC) class II antigen-presenting cells (APCs) in inflamed cornea after thermal cautery. Furthermore, expression of interleukin (IL)-1beta mRNA was suppressed in cauterized cornea. These results suggest that HAECs are a source of soluble anti-inflammatory factors that suppress corneal inflammation. However, viable amniotic epithelial cells display antigenicity and immunogenicity as allografts. Fresh allogeneic amniotic epithelium (AE) expresses MHC class I antigens and sensitizes recipients when placed in the eye, although long-term memory of allo-specific delayed hypersensitivity (DH) was not acquired. Allogeneic AE was clearly vulnerable to acute immune rejection in specifically sensitized recipients and recipients of repeated AE transplantation. We therefore suggest that immunogenicity of AE should not be ignored, and use of AM from different donor placentas should be emphasized when repeated AM transplantation is required in patients clinically.

Activation of CD36 inhibits and induces regression of inflammatory corneal neovascularization

PURPOSE

This study was undertaken to investigate the role of the antiangiogenic receptor CD36 during inflammatory corneal neovascularization (CNV).

METHODS

In a murine model of inflammatory CNV, CD36 expression was evaluated by RT-PCR and immunofluorescence. Mice subjected to CNV were treated topically (thrice daily) with CD36 functionally neutralizing antibodies against the oxidized low-density lipoprotein (oxLDL) and thrombospondin (TSP)-1 sites (clones JC63.1 and FA6-152, respectively). Neovascularization was analyzed by CD31-immunostained corneal flatmounts. The role of the less characterized oxLDL site during angiogenesis was elucidated by using the CD36 ligand 1-palmitoyl 2-(5'-oxovaleroyl) phosphatidylcholine (POVPC; 50, 100 microg/mL) 24 hours after corneal injury for 7 days, whereas in angioregressive studies, POVPC treatments were initiated 10 days after induction of CNV. In this process, VEGF expression was also studied. Effects of CD36 activation were further examined ex vivo using the mouse aortic ring assay.

RESULTS

CD36 expression was upregulated after corneal injury; CD36 was expressed in corneal epithelium, limbus, invading microvessels, and stromal macrophages. Blocking CD36 activity with FA6-152 significantly increased CNV (P <0.001). Conversely, activating CD36 with POVPC dose dependently inhibited CNV (P = 0.003); this effect was blocked by JC61.3. POVPC also significantly regressed preformed blood vessels (P < 0.001). Ex vivo experiments on aortic rings confirmed the angioinhibitory and -regressive effects of POVPC. Because corneal macrophages express CD36 and may partake in angiogenesis via VEGF-A secretion, we surmised that VEGF-A could be modulated by CD36. Indeed, POVPC downregulated VEGF-A expression in a time-dependent fashion (P < 0.001), whereas FA6-152 induced its expression (P < 0.05).

CONCLUSIONS

CD36 is involved both physiologically and pharmacologically in inhibition and regression of CNV, by direct effect on endothelial cells and partly by negatively regulating VEGF expression in macrophages.

Sustained intraocular rapamycin delivery effectively prevents high-risk corneal allograft rejection and neovascularization in rabbits

PURPOSE

To evaluate the immunosuppressive and antiangiogenic activities of an intraocular rapamycin (RAPA) drug delivery system (DDS) in a rabbit model of high-risk penetrating keratoplasty.

METHODS

Forty New Zealand White rabbits with corneal neovascularization underwent allograft cornea transplantation and were randomly divided into four groups: a control group, a glycolide-co-lactide-co-caprolactone copolymer (PGLC)-implanted group, a RAPA eye drop group, and a RAPA-PGLC DDS-implanted group. Graft survival, corneal neovascularization, and RAPA concentration in the aqueous humor were monitored for 90 days. Corneal grafts were also examined by in situ hybridization and immunohistochemistry for proinflammatory gene expression.

RESULTS

In the control and PGLC groups, graft rejection occurred within 3 weeks of keratoplasty. In the RAPA eye drop and RAPA-PGLC groups, corneal rejection was significantly delayed, and neovascularization was markedly inhibited. Median graft survival times were 36 and >90 days in the eye drop and RAPA-PGLC groups, respectively. Mean RAPA concentrations in the aqueous humor were 10.7 ng/mL, 12.0 ng/mL, 9.2 ng/mL, and 7.0 ng/mL in the RAPA-PGLC group 2, 4, 8, and 12 weeks after surgery, respectively. By contrast, RAPA was undetectable in the aqueous humor in the eye drop group. High levels of IL-2R, MCP-1, TNF-alpha, and VEGF were detected in the corneal grafts of the control and PGLC groups but not in those of the RAPA-treated groups.

CONCLUSIONS

RAPA-PGLC DDS and RAPA eye drops can significantly prolong the survival of allografts at high risk and inhibit corneal neovascularization. However, RAPA-PGLC DDS is far more effective than RAPA eye drops in preventing corneal graft rejection.

Promotion of Corneal Epithelial Wound Healing by a Tetrapeptide (SSSR) Derived from IGF-1

PURPOSE

A prior study showed that a tetrapeptide (FGLM-amide) derived from the carboxyl terminus of substance P (SP) and a 12-residue peptide corresponding to the C domain of insulin-like growth factor (IGF)-1 mimic the synergistic effect of the full-length molecules on corneal epithelial wound healing. To develop an effective treatment for persistent corneal epithelial defects, the current study was conducted to investigate the minimal sequence within the C domain of IGF-1 that is required for such synergism with SP or FGLM-amide.

METHODS

The effects of IGF-1-derived peptides on corneal epithelial migration were evaluated with a rabbit corneal organ-culture system.

RESULTS

A tetrapeptide (SSSR; Ser(33)-Ser-Ser-Arg) derived from the C domain of IGF-1 was sufficient for the synergistic promotion with FGLM-amide both of corneal epithelial migration in vitro and of wound closure in vivo. The activity of the SSSR peptide was sequence specific and its potency was similar to that of IGF-1. The SSSR peptide by itself also promoted corneal epithelial migration in vitro at higher concentrations. It was devoid, however, of both the mitogenic action of IGF-1 and the ability of the full-length molecule to induce neovascularization.

CONCLUSIONS

The SSSR sequence mediates the synergistic effect of IGF-1 with SP on corneal epithelial wound healing. Clinical application of the SSSR peptide would be expected to be free of potentially deleterious side effects associated with treatment with full-length IGF-1. Local administration of the SSSR tetrapeptide, alone or in combination with FGLM-amide, is thus a potential new strategy for the treatment of nonhealing epithelial wounds.

Prevention of Corneal Neovascularization

PURPOSE

To evaluate the effect of topically administered agents doxycycline, triamcinolone, low molecular weight heparin (LMWH), and flurbiprofen on experimental corneal neovascularization in rats.

METHODS

Chemical cauterization of cornea was performed in 36 eyes of 36 rats by using silver nitrate/potassium nitrate sticks. Topical instillation of doxycycline, triamcinolone, LMWH, flurbiprofen, and normal saline solution was continued for 7 days. Percent areas of cornea covered by neovascularization and covered by scar in each group were calculated by use of computer software on digital photographs. Groups were compared for any significant (P < 0.05) differences among them.

RESULTS

The means of percent area of corneal neovascularization in triamcinolone, doxycycline, flurbiprofen, LMWH, and control groups were 13.3%, 35.5%, 50.6%, 66.7%, and 74.9%, respectively. The triamcinolone and doxycycline groups were different from control group (P < 0.05). There was no significant difference in the percent area of neovascularization between the LMWH and flurbiprofen groups compared with the controls. Although the effects of LMWH and flurbiprofen were not significant, there seemed to be a trend, and the lack of significance may be related to small sample size. Because the mechanisms of action of these agents are not identical to each other, performing other studies using combinations of them seems to be reasonable. There were no significant differences in percent area of corneal scar among groups.

CONCLUSION

Topical instillation of commercially available triamcinolone and doxycycline seems to diminish corneal neovascularization caused by chemical cauterization of cornea in rats.

The role of PDGF receptor inhibitors and PI3-kinase signaling in the pathogenesis of corneal neovascularization

PURPOSE

Corneal neovascularization remains an unsolved therapeutic problem. Platelet-derived growth factor (PDGF) is directly linked to vessel formation and stabilization. This study was undertaken to elucidate the mechanisms by which PDGF exerts its effects on corneal angiogenesis.

METHODS

Corneal neovascularization was induced in C57 mice by removal of the limbal epithelium. When mature vessels appeared after 7 days, mice were treated with the PDGF receptor-beta inhibitor AG 1296 or the phosphatidylinositol 3-kinase (PI3-K)-inhibitors wortmannin and LY294002, respectively, using an intraperitoneally implanted miniosmotic pump. At day 14 after scraping, corneas of treated and untreated (control) mice were dissected and immunostained with FITC-CD31 antibody for endothelial cells and with Cy3-SMA (smooth muscle actin) for pericytes. VEGF (vascular endothelial growth factor), ang1/2 (angiopoietin 1 and 2), and PDGF mRNA levels of treated and untreated corneas were determined by real-time RT-PCR.

RESULTS

Mice treated with the PDGF inhibitor AG 1296 showed an inhibition of corneal neovascularization of 21.1% and a reduction of pericytes of 52% in the newly formed vessels compared with untreated animals. VEGF, ang1, ang2, and PDGF mRNA expression was reduced in the corneas of AG 1296-treated mice compared with the respective control. Treatment with the PI3-K inhibitors wortmannin and LY29002 had similar effects, inducing a decrease in corneal neovascularization and a reduction of VEGF, ang1, ang2, and PDGF mRNA levels.

CONCLUSIONS

Inhibition of the PDGF signal pathway results in loss of pericytes and a reduction in vessel density in the neovascularized cornea that correlates with reduced expression of PDGF, ang1/2, and VEGF mRNA. Furthermore, PI3-K was shown to be involved in the regulation of VEGF, ang1, and PDGF, as the PI3-K inhibitors wortmannin or LY294002 had similar effects. Because PDGF is a known stimulus for PI3-K activation, it can be postulated that the observed decrease in VEGF, ang1/2, and PDGF mRNA levels on administration of the PDGF inhibitor is caused by the decreased activation of the PI3-K signaling cascade.