Corneal neovascularization and the utility of topical VEGF inhibition: ranibizumab (Lucentis) vs bevacizumab (Avastin)

RIP1 kinase mediates angiogenesis by modulating macrophages in experimental neovascularization

Pathological angiogenesis has been implicated in diverse pathologies. Infiltrating macrophages, especially those activated to M2-like phenotype, are critically important for angiogenesis. Although the role of RIP1 kinase in the regulation of apoptosis, necroptosis, and inflammation has been well-established, its role in angiogenesis remains elusive, despite being abundantly expressed in angiogenesis-related infiltrating macrophages. This study demonstrates that RIP1 kinase inhibition attenuates angiogenesis in multiple mouse models of pathological angiogenesis in vivo and suggests a therapeutic role of RIP1 kinase inhibition in pathological angiogenesis. Mechanistically, the inhibitory effect on angiogenesis depends on RIP kinase inhibition-mediated caspase activation in infiltrating macrophages through suppression of M2-like polarization, and subsequent attenuation of pathological angiogenesis.

Inflammation plays an important role in pathological angiogenesis. Receptor-interacting protein 1 (RIP1) is highly expressed in inflammatory cells and is known to play an important role in the regulation of apoptosis, necroptosis, and inflammation; however, a comprehensive description of its role in angiogenesis remains elusive. Here, we show that RIP1 is abundantly expressed in infiltrating macrophages during angiogenesis, and genetic or pharmacological inhibition of RIP1 kinase activity using kinase-inactive RIP1^K45A/K45A mice or necrostatin-1 attenuates angiogenesis in laser-induced choroidal neovascularization, Matrigel plug angiogenesis, and alkali injury-induced corneal neovascularization in mice. The inhibitory effect on angiogenesis is mediated by caspase activation through a kinase-independent function of RIP1 and RIP3. Mechanistically, infiltrating macrophages are the key target of RIP1 kinase inhibition to attenuate pathological angiogenesis. Inhibition of RIP1 kinase activity is associated with caspase activation in infiltrating macrophages and decreased expression of proangiogenic M2-like markers but not M1-like markers. Similarly, in vitro, catalytic inhibition of RIP1 down-regulates the expression of M2-like markers in interleukin-4–activated bone marrow-derived macrophages, and this effect is blocked by simultaneous caspase inhibition. Collectively, these results demonstrate a nonnecrotic function of RIP1 kinase activity and suggest that RIP1-mediated modulation of macrophage activation may be a therapeutic target of pathological angiogenesis.

VEGF188 promotes corneal reinnervation after injury

Vascular endothelial growth factor A (VEGF) induces angiogenesis and vascular hyperpermeability in ocular tissues and is therefore a key therapeutic target for eye conditions in which these processes are dysregulated. In contrast, the therapeutic potential of VEGF's neurotrophic roles in the eye has remained unexploited. In particular, it is not known whether modulating levels of any of the 3 major alternatively spliced VEGF isoforms might provide a therapeutic approach to promote neural health in the eye without inducing vascular pathology. Here, we have used a variety of mouse models to demonstrate differences in overall VEGF levels and VEGF isoform ratios across tissues in the healthy eye. We further show that VEGF isoform expression was differentially regulated in retinal versus corneal disease models. Among the 3 major isoforms - termed VEGF120, VEGF164, and VEGF188 - VEGF188 was upregulated to the greatest extent in injured cornea, where it was both necessary and sufficient for corneal nerve regeneration. Moreover, topical VEGF188 application further promoted corneal nerve regeneration without inducing pathological neovascularization. VEGF isoform modulation should therefore be explored further for its potential in promoting neural health in the eye.

Prevention of Corneal Neovascularization by Adenovirus Encoding Human Vascular Endothelial Growth Factor Soluble Receptor (s-VEGFR1) in Lacrimal Gland

Purpose

The aims of this study were (1) to determine the efficacy of adenovirus vector serotype 5 (Ad) encoding human soluble VEGF receptor 1 (s-VEGFR1) gene transfer to the lacrimal gland (LG); (2) to investigate whether expression of s-VEGFR1 prevents corneal neovascularization (CNV) induced by alkali burns; and (3) to evaluate the safety of the procedure.

Methods

AdVEGFR1 vectors (25 μL, 1 × 1010 pfu/mL) were injected in the right LGs of rats and were compared with AdNull vector (25 μL, 1 × 1010 pfu/mL) or 25 μL of saline (Control) before cornea alkali burns with 1 M NaOH. After 7 days, CNV was documented at the slit lamp. Tear secretion was measured with phenol red threads. The animals were tested for s-VEGFR1 mRNA and protein in the LG by quantitative (q)PCR and immunohistochemistry staining, respectively. qPCR was used to compare the mRNA levels of IL-1β, IL-6, and TNF-α in the LG and ipsilateral trigeminal ganglion (TG).

Results

Ad-VEGFR1 transfected 83% (10/12) of the rats. VEGFR1 was present in LG acinar cells. CNV was prevented in 9 of 12 animals in the Ad-VEGFR1 group, compared with the Ad-Null (3:10) and Control groups (1:10) (P = 0.0317). The tear secretion and cytokine mRNA levels in the LG and TG were similar in all three groups (P > 0.05).

Conclusions

Adenoviral vector gene transfer was safe for LG structure and function. The LG as the target tissue showed local expression of human s-VEGFR1, and CNV was prevented in most of the eyes exposed to alkali burns.

Short-term regression of corneal neovascularization with combination therapy of argon green laser photocoagulation and subconjunctival bevacizumab

We present a case of a 49 year-old male with history of corneal neovascularization secondary to herpes zoster keratitis that clinically and subjectively improved for approximately 4 months after treatment with argon laser photocoagulation to feeder vessels and subconjunctival bevacizumab. This is the first report in the literature that describes this novel combination treatment for corneal neovascularization in the setting of varicella-zoster virus and discusses its efficacy.

The Effect of Periocular Fatty Acids and 0.15% Hyaluronate Eye Drops Application on Keratoconjunctivitis Sicca in Dogs: An Exploratory Study

The aim of this exploratory study was to evaluate the efficacy of a periophthalmic cream of a pool of fatty acids (FAG®) in association with 0.15% hyaluronate eye drops in alleviating the clinical symptoms of keratoconjunctivitis sicca (KCS) in a case series of dogs. The study was conducted on 10 dogs diagnosed with idiopathic KCS. All dogs had been previously treated with topical tobramycin alone, which had been ineffective in improving clinical signs. The affected eyes were treated with 2 applications daily of a periophthalmic cream of FAG® and 1 drop 3 times a day of 0.15% of hyaluronate eye drops for 8 weeks. Schirmer tear test I (STT I) values were recorded and ocular signs (conjunctival hyperemia, ocular discharge, corneal opacity, vascularization and pigmentation, and discomfort level) were collected, scored on a 3-point scale (grade 0, grade 1, and grade 2). Differences between scores and STT data recorded at baseline and at 8 weeks of therapy were statistically analysed. The effect of treatment was pronounced (increase in STT values by more than 4 mm/min, no signs of inflammation) in 8/18 eyes; moderate (increase in STT values of 3-4 mm/min or mild improvement in signs of corneal/conjunctival inflammation) in 3/18 eyes; and unsatisfactory in 7 of 18 eyes. Median of STT values significantly improved compared with baseline levels, while statistically significant decreases in clinical-sign scores of conjunctival hyperemia, ocular discharge, and discomfort were recorded. However, in moderate and advanced stages, reduction of neovascularization or corneal pigmentation was not observed throughout the treatment period. No noticeable adverse reactions were recorded. Preliminary results indicate that the application of periocular FAG and topical 0.15% hyaluronate eye drops may be a suitable treatment for KCS in dogs in selected cases. A larger comparative study is necessary to further confirm these findings.

Suppression of neovascularization in corneal stroma in a TRPA1-null mouse

Corneal neovascularization and inflammatory fibrosis induced by severe injury or infection leads to tissue opacification and even blindness. Transient receptor potential (TRP) channel subtypes contribute to mediating these maladaptive responses through their interactions with other receptors. TRPV1 is one of the contributing channel isoforms inducing neovascularization in an alkali burn mouse wound healing model. VEGF-A upregulation contributes to neovascularization through interaction with its cognate receptors (VEGFR). Since the TRP isoform in this tissue, TRPA1, is also involved, we determined here if one of the pathways mediating neovascularization and immune cell infiltration involve an interaction between VEGFR and TRPA1 in a cauterization corneal mouse wound healing model. Localization of TRPA1 and endothelial cell (EC) CD31 immunostaining pattern intensity determined if TRPA1 expression was EC delimited during cauterization induced angiogenesis. Quantitative RT-PCR evaluated the effects of the absence of TRPA1 function on VEGF-A and TGF-β1 mRNA expression during this process. Macrophage infiltration increased based on rises in F4/80 antigen immunoreactivity. TRPA1 immunostaining was absent on CD31-immunostained EC cells undergoing neovascularization, but it was present on other cell type(s) adhering to EC in vivo. Absence of TRPA1 expression suppressed both stromal neovascularization and inhibited macrophage infiltration. Similarly, the increases occurring in both VEGF-A and TGF-β1 mRNA expression levels in WT tissue were blunted in the TRPA1^-/- counterpart. On the other hand, in the macrophages their levels were invariant and their infiltration was inhibited. To determine if promotion by TRPA1 of angiogenesis was dependent on its expression on other unidentified cell types, the effects were compared of pharmacological manipulation of TRPA1 activity on EC proliferation tube formation and migration. In the presence and absence of a fibroblast containing feeder layer. Neither VEGF-induced increases in human vascular endothelial cell (HUVEC) proliferation nor migration were changed by a TRPA1 antagonist HC-030031 in the absence of a feeder layer. However, on a fibroblast feeder layer this antagonist suppressed HUVEC tube formation. In conclusion, during corneal wound healing transactivation by VEGFR of TRPA1 contributes to mediating neovascularization and macrophage infiltration. Such crosstalk is possible because of close proximity between VEGFR delimited expression on EC and TRPA1 expression restricted to cell types adhering to EC.

Detection of Pro- and Antiangiogenic Factors in the Human Sclera

PURPOSE

Avascular tissues can be used to identify antilymph- or antihemangiogenic factors. The human sclera-the outer covering layer of the eye, lacks lymphatic vessels and contains only a superficial network of blood vessels and was used here to identify endogenous antiangiogenic factors.

METHODS

Expression levels of a panel of 96 known pro- and antiangiogenic factors were analyzed in 12 scleral or conjunctival control samples from normal human donors using real-time PCR. In vitro, scleral homogenate was cocultured with blood- and lymphatic endothelial cells (BECs and LECs) and immunohistochemistry was performed of scleral fibroblasts and BECs.

RESULTS

Three antiangiogenic factors were significantly upregulated in the human sclera compared to the conjunctiva, including FBLN5 (fibulin 5), SERPINF1 (serpin peptidase inhibitor, clade F, member 1 = pigment epithelium derived factor) and TIMP2 (Tissue inhibitor of metalloproteinases 2). Six proangiogenic factors were significantly downregulated in the sclera, including FLT4 (Fms-related tyrosine kinase 4=VEGF-R3), HGF (hepatocyte growth factor), KIT (CD117 / c-kit), PROX1 (prospero homeobox 1), SEMA3F (semaphorin-3F) and TGFA (transforming growth factor alpha). In vitro, scleral homogenate inhibited the growth of both BECs and LECs. Immunohistochemistry labeling of three major antiangiogenic factors from scleral tissue confirmed TIMP3 and PEDF expression both in scleral fibroblasts and in blood endothelial cells, whereas TIMP2 was not detectable.

CONCLUSION

Balancing anti- and proangiogenic factors actively regulates human scleral avascularity, inhibits endothelial cell growth in vitro, and thus may help maintaining the vascular privilege of the inner eye.

Comparison of Optical Coherence Tomography Angiography to Indocyanine Green Angiography and Slit Lamp Photography for Corneal Vascularization in an Animal Model

Corneal neovascularization (CoNV) could be treated by novel anti-angiogenic therapies, though reliable and objective imaging tools to evaluate corneal vasculature and treatment efficacy is still lacking. Optical coherence tomography angiography (OCTA) -currently designed as a retinal vascular imaging system- has been recently adapted for anterior-segment and showed good potential for successful imaging of CoNV. However, further development requires an animal model where parameters can be studied more carefully with histological comparison. Our study evaluated the OCTA in suture-induced CoNV in a rabbit model compared to indocyanine green angiography (ICGA) and slit-lamp photography (SLP). Overall vessel density measurements from OCTA showed good correlation with ICGA (0.957) and SLP (0.992). Vessels density by OCTA was higher than ICGA and SLP (mean = 20.77 ± 9.8%, 15.71 ± 6.28% and 17.55 ± 8.36%, respectively, P < 0.05). OCTA was able to depict CoNV similarly to SLP and ICGA, though it could better detect small vessels. Moreover, the depth and growth of vessels could be assessed using en-face and serial-scans. This study validated the OCTA in a rabbit model as a useful imaging tool for translational studies on CoNV. This may contribute to further studies on OCTA for anterior-segment including serial evaluation of emerging anti-angiogenic therapies.

Targeting corneal inflammation by gene therapy: Emerging strategies for keratitis

Inflammation is the underlying process of several diseases within the eye, specifically in the cornea. Current treatment options for corneal inflammation or keratitis, and related neovascularization, are restricted by limited efficacy, adverse effects, and short duration of action. Gene therapy has shown great potential for the treatment of diseases affecting the ocular surface, and major efforts are being targeted to inflammatory mediators and neovascularization, in order to develop potential treatments for corneal inflammation. Gene therapy to treat ocular disorders is still starting, and current therapies are primarily experimental, with most human clinical trials still in research state, although some of them have already shown encouraging results. In this review, we focus on the progress and challenges of gene therapy to treat corneal inflammation. After introducing the inflammation process, we present the main nucleic acid delivery systems, including viral and non-viral vectors, and the most studied strategies to address the therapy: control of neovascularization and regulation of pro- and anti-inflammatory cytokines.

Current and emerging therapies for corneal neovascularization

The cornea is unique because of its complete avascularity. Corneal neovascularization (CNV) can result from a variety of etiologies including contact lens wear; corneal infections; and ocular surface diseases due to inflammation, chemical injury, and limbal stem cell deficiency. Management is focused primarily on the etiology and pathophysiology causing the CNV and involves medical and surgical options. Because inflammation is a key factor in the pathophysiology of CNV, corticosteroids and other anti-inflammatory medications remain the mainstay of treatment. Anti-VEGF therapies are gaining popularity to prevent CNV in a number of etiologies. Surgical options including vessel occlusion and ocular surface reconstruction are other options depending on etiology and response to medical therapy. Future therapies should provide more effective treatment options for the management of CNV.

Effect of metronidazole ophthalmic solution on corneal neovascularization in a rat model

PURPOSE

To evaluate the effect of metronidazole ophthalmic solutions on corneal neovascularization (CNV) in a rat model.

METHODS

A chemical burn was created in the right central cornea of 40 rats. Animals were randomized and distributed into four study groups (n = 10 rats per group) designated Met_0.1%, Met_0.5%, sham, and untreated groups. Chemical-burned corneas in the Met_0.1% and Met_0.5% groups received ophthalmic solutions of 0.1 and 0.5% metronidazole, respectively. Corneas in the sham group received phosphate-buffered saline (metronidazole diluent). All treated eyes received ophthalmic solution at intervals of 6 h, for up to 30 days. Untreated corneas received no treatment. CNV was evaluated postinjury using corneal photographs at different evaluation time points. The main CNV outcome measures were: burn intensity, index of CNV, and percentage of vascularized corneal area. Five rats from each group were euthanized, on days 15 and 30; the samples were collected for histological analyses. Differences with P < 0.05 were considered significant.

RESULTS

CNV was observed in the eyes from day 7 postinjury. However, the indices of CNV for the Met_0.1% and Met_0.5% groups were smaller than those for the sham and untreated groups (P < 0.05). Furthermore, corneas treated with 0.1 or 0.5% metronidazole had smaller vascularized areas compared to control corneas. On histological study, the presence of blood vessels confirmed clinical outcomes.

CONCLUSIONS

Regular instillation of 0.1 or 0.5% metronidazole had a significant inhibitory effect for CNV on chemical burns induced in a rat model.

Intraocular Penetration of a vNAR: In Vivo and In Vitro VEGF165 Neutralization

Variable new antigen receptor domain (vNAR) antibodies are novel, naturally occurring antibodies that can be isolated from naïve, immune or synthetic shark libraries. These molecules are very interesting to the biotechnology and pharmaceutical industries because of their unique characteristics related to size and tissue penetrability. There have been some approved anti-angiogenic therapies for ophthalmic conditions, not related to vNAR. This includes biologics and chimeric proteins that neutralize vascular endothelial growth factor (VEGF)₁₆₅, which are injected intravitreal, causing discomfort and increasing the possibility of infection. In this paper, we present a vNAR antibody against human recombinant VEGF₁₆₅ (rhVEGF₁₆₅) that was isolated from an immunized Heterodontus francisci shark. A vNAR called V13, neutralizes VEGF₁₆₅ cytokine starting at 75 μg/mL in an in vitro assay based on co-culture of normal human dermal fibroblasts (NHDFs) and green fluorescence protein (GFP)-labeled human umbilical vein endothelial cells (HUVECs) cells. In the oxygen-induced retinopathy model in C57BL/6:Hsd mice, we demonstrate an endothelial cell count decrease. Further, we demonstrate the intraocular penetration after topical administration of 0.1 μg/mL of vNAR V13 by its detection in aqueous humor in New Zealand rabbits with healthy eyes after 3 h of application. These findings demonstrate the potential of topical application of vNAR V13 as a possible new drug candidate for vascular eye diseases.

Cornea-Derived Mesenchymal Stromal Cells Therapeutically Modulate Macrophage Immunophenotype and Angiogenic Function

Macrophages are crucial drivers of inflammatory corneal neovascularization and thus are potential targets for immunomodulatory therapies. We hypothesized that therapeutic use of cornea-derived mesenchymal stromal cells (cMSCs) may alter the function of macrophages. We found that cMSCs can modulate the phenotype and angiogenic function of macrophages. In vitro, cMSCs induce apoptosis of macrophages while preferentially promoting a distinct CD14^hi CD16^hi CD163^hi CD206^hi immunophenotype that has significantly reduced angiogenic effects based on in vitro angiogenesis assays. In vivo, application of cMSCs to murine corneas after injury leads to reduced macrophage infiltration and higher expression of CD206 in macrophages. Macrophages cocultured ("educated") by cMSCs express significantly higher levels of anti-angiogenic and anti-inflammatory factors compared with control macrophages. In vivo, injured corneas treated with cMSC-educated macrophages demonstrate significantly less neovascularization compared with corneas treated with control macrophages. Knocking down the expression of pigment epithelial derived factor (PEDF) in cMSCs significantly abrogates its modulating effects on macrophages, as shown by the reduced rate of apoptosis, decreased expression of sFLT-1/PEDF, and increased expression of vascular endothelial growth factor-A in the cocultured macrophages. Similarly, cMSCs isolated from PEDF knockout mice are less effective compared with wild-type cMSCs at inhibiting macrophage infiltration when applied to wild-type corneas after injury. Overall, these results demonstrate that cMSCs therapeutically suppress the angiogenic capacity of macrophages and highlight the role of cMSC secreted PEDF in the modulation of macrophage phenotype and function. Stem Cells 2018;36:775-784.

Selective IKK2 inhibitor IMD0354 disrupts NF-κB signaling to suppress corneal inflammation and angiogenesis

Corneal neovascularization is a sight-threatening condition caused by angiogenesis in the normally avascular cornea. Neovascularization of the cornea is often associated with an inflammatory response, thus targeting VEGF-A alone yields only a limited efficacy. The NF-κB signaling pathway plays important roles in inflammation and angiogenesis. Here, we study consequences of the inhibition of NF-κB activation through selective blockade of the IKK complex IκB kinase β (IKK2) using the compound IMD0354, focusing on the effects of inflammation and pathological angiogenesis in the cornea. In vitro, IMD0354 treatment diminished HUVEC migration and tube formation without an increase in cell death and arrested rat aortic ring sprouting. In HUVEC, the IMD0354 treatment caused a dose-dependent reduction in VEGF-A expression, suppressed TNFα-stimulated expression of chemokines CCL2 and CXCL5, and diminished actin filament fibers and cell filopodia formation. In developing zebrafish embryos, IMD0354 treatment reduced expression of Vegf-a and disrupted retinal angiogenesis. In inflammation-induced angiogenesis in the rat cornea, systemic selective IKK2 inhibition decreased inflammatory cell invasion, suppressed CCL2, CXCL5, Cxcr2, and TNF-α expression and exhibited anti-angiogenic effects such as reduced limbal vessel dilation, reduced VEGF-A expression and reduced angiogenic sprouting, without noticeable toxic effect. In summary, targeting NF-κB by selective IKK2 inhibition dampened the inflammatory and angiogenic responses in vivo by modulating the endothelial cell expression profile and motility, thus indicating an important role of NF-κB signaling in the development of pathologic corneal neovascularization.

Comparative immunological study of penetrating and anterior lamellar keratoplasty in a murine model

In lamellar keratoplasty, the diseased part of a cornea is replaced while the healthy tissue remains lamellar keratoplasty has the advantage of better graft survival compared to penetrating keratoplasty (PK). We compared the immunological responses to PK and anterior lamellar keratoplasty (ALK) in a murine model. PK or ALK was performed using C57BL/6 donor grafts and BALB/c recipients, and graft opacity was assessed to evaluate graft rejection up to 8 weeks. We evaluated the immunological responses in both groups, which were not clinically considered as graft failure on postoperative day 21. PK mice showed reduced clinical graft survival compared to ALK mice. The mRNA expression of inflammatory mediators, such as IL-1β, IFN-γ, and granzyme B, in grafted corneas of PK mice, was significantly increased compared to the levels in ALK mice at postoperative day 21. PK led to a higher delayed-type hypersensitivity response and IFN-γ secretion in an in vitro T cell assay from draining lymph nodes (LNs), as compared to ALK. Furthermore, PK showed increased angiogenesis and lymphangiogenesis in grafted corneas compared to ALK and led to greater infiltration of CD3⁺ T cells into grafted corneas and increased frequencies of mature antigen presenting cells (APC; MHC-II^highCD11c + cells) and IL-12 + dendritic cells (DCs) in the draining LNs of transplanted mice. In conclusion, PK results in increased graft rejection compared to ALK through relatively increased neovascularization and lymphangiogenesis, which can induce infiltration of pathologic T cells and mature APC migration into grafted corneas and draining LNs.

New Therapeutic Perceptions in a Patient with Complicated Herpes Simplex Virus 1 Keratitis: A Case Report and Review of the Literature

Patient: Male, 80

Final Diagnosis: Unilateral complicated Herpetic Simplex Virus 1 Keratitis

Symptoms: Visual impairment

Medication: Anti-herpetic treatment • Anti-VEGF • Cyclosporine A • Matrix regeneration therapy

Clinical Procedure: Amniotic membrane and limbal stem cell transplantation

Specialty: Ophthalmology

Angiogenesis and lymphangiogenesis in corneal transplantation-A review

Corneal transplantation has been proven effective for returning the gift of sight to those affected by corneal disorders such as opacity, injury, and infections that are a leading cause of blindness. Immune privilege plays an important role in the success of corneal transplantation procedures; however, immune rejection reactions do occur, and they, in conjunction with a shortage of corneal donor tissue, continue to pose major challenges. Corneal immune privilege is important to the success of corneal transplantation and closely related to the avascular nature of the cornea. Corneal avascularity may be disrupted by the processes of angiogenesis and lymphangiogenesis, and for this reason, these phenomena have been a focus of research in recent years. Through this research, therapies addressing certain rejection reactions related to angiogenesis have been developed and implemented. Corneal donor tissue shortages also have been addressed by the development of new materials to replace the human donor cornea. These advancements, along with other improvements in the corneal transplantation procedure, have contributed to an improved success rate for corneal transplantation. We summarize recent developments and improvements in corneal transplantation, including the current understanding of angiogenesis mechanisms, the anti-angiogenic and anti-lymphangiogenic factors identified to date, and the new materials being used. Additionally, we discuss future directions for research in corneal transplantation.

Therapeutic approaches for corneal neovascularization

Angiogenesis refers to new blood vessels that originate from pre-existing vascular structures. Corneal neovascularization which can lead to compromised visual acuity occurs in a wide variety of corneal pathologies. A large subset of measures has been advocated to prevent and/or treat corneal neovascularization with varying degrees of success. These approaches include topical corticosteroid administration, laser treatment, cautery, and fine needle diathermy. Since the imbalance between proangiogenic agents and antiangiogenic agents primarily mediate the process of corneal neovascularization, recent therapies are intended to disrupt the different steps in the synthesis and actions of proangiogenic factors. These approaches, however, are only partially effective and may lead to several side effects. The aim of this article is to review the most relevant treatments for corneal neovascularization available so far.

Growth inhibition of formed corneal neovascularization following Fosaprepitant treatment

PURPOSE

The aim of this study was to test the efficacy of Neurokinin-1 Receptor (NK-1R) antagonist -Fosaprepitant- in inducing regression of established corneal neovascularization (CNV).

METHODS

Twenty C57BL/6 mice underwent alkali burn. Seven days later, when corneal neovessels had developed, they received Fosaprepitant 10 mg/ml, administered topically six times a day in the right eye for 10 days. In parallel, a group of 20 causticated mice was treated with normal saline, as control. A second independent experiment was also performed (n = 10/group). Finally, ten healthy mice received the same topical treatment for 10 days to evaluate Fosaprepitant safety. Haemangiogenesis and lymphangiogenesis were measured by means of vesselj plugin (imagej). Secondary endpoints, such as leucocyte infiltration, corneal opacity and corneal fluorescein staining were also evaluated. Inflammatory cell composition was assessed by flow cytometry. Differences between groups were assessed using unpaired t-test, Mann-Whitney U-test or two-way anova, as appropriate.

RESULTS

Topical Fosaprepitant administration induced a significant reduction of (i) CD31⁺ blood corneal neovessels (-27%, p = 0.0132), (ii) LYVE1⁺ lymphatic corneal neovessels (-31%, p = 0.0118) and (iii) CD45⁺ leucocyte infiltration (-36%; p = 0.0237). The second independent experiment confirmed these data. Moreover, Fosaprepitant-treated corneas showed a reduction in opacity, no impairment in corneal fluorescein staining and decreased infiltration of neutrophils (-72%, p < 0.05) and macrophages (-75%, p < 0.01). Finally, topical Fosaprepitant was not toxic to the ocular surface: no signs of conjunctivitis, opacity, perforations or corneal fluorescein staining were detected. Similarly, corneal TUJ1⁺ nerve density was not affected.

CONCLUSIONS

Our data suggest that NK-1R antagonists, such as Fosaprepitant, could be a new, promising therapeutic tool to inhibit CNV after this has been established.

Effects of Combined Photodynamic Therapy and Topical Bevacizumab Treatment on Corneal Neovascularization in Rabbits

PURPOSE

To evaluate the effects of combined photodynamic therapy (PDT) and topical bevacizumab treatment on corneal neovascularization in rabbits.

METHODS

Corneal neovascularization was induced by placing a suture for 7 days in both eyes of 15 rabbits. After suture removal, the right eyes of the rabbits were divided into 3 treatment groups (n = 5 each): group 1, 5 mg/mL bevacizumab eye drops; group 2, PDT at 150 J/cm; and group 3, combined PDT and topical bevacizumab treatment. All 15 left eyes formed a control group. After 2 weeks of treatment, digital photographs were obtained and analyzed to determine the area of corneal neovascularization. The rabbits were then killed to measure vascular endothelial growth factor (VEGF) levels in corneal tissues.

RESULTS

The corneal neovascularization area after treatment was significantly smaller in the 3 treatment groups compared with that in the control group. A significant difference was observed between groups 1 and 2 and group 3, but not between groups 1 and 2. VEGF levels were significantly lower in groups 1 and 3 than in the control group. Although group 2 exhibited relatively higher VEGF levels compared with the control group, the difference was not significant.

CONCLUSIONS

Our results suggest that combined PDT and topical bevacizumab treatment is significantly more effective than monotherapy for the treatment of corneal neovascularization in rabbits. Such quantitative comparison in the laboratory is believed to provide the theoretical basis for clinical application of combined PDT and topical bevacizumab treatment.

Kinetics of Angiogenic Responses in Corneal Transplantation

PURPOSE

To delineate and compare the kinetics of corneal angiogenesis after high-risk (HR) versus low-risk (LR) corneal transplantation.

METHODS

In mice, intrastromal sutures were placed in the recipient graft bed 2 weeks before allogeneic transplantation to induce angiogenesis and amplify the risk of graft rejection. Control (LR) graft recipients did not undergo suture placement, and thus the host bed remained avascular at the time of transplantation. Graft hemangiogenesis and opacity scores were evaluated for 8 weeks by slit-lamp biomicroscopy. Immunohistochemistry was used to measure CD31 (blood vessels) and LYVE-1 (lymphatic vessels) cells.

RESULTS

Biphasic kinetics were observed for hemangiogenesis in both HR and LR transplant recipients using clinical and immunohistochemical assessments. The biphasic kinetics were composed of a rise-fall (phase 1) followed by a second rise (phase 2) in the degree of vessels. Compared with LR recipients, HR recipients showed higher hemangiogenesis (whole cornea and graft) throughout 8 weeks. Analyzing grafts revealed sustained presence of lymphatic vessels in HR recipients; however, lymphatic neovessels regressed in LR recipients 2 weeks posttransplantation. In contrast to HR host beds, the LR host bed microenvironment cannot sustain the growth of lymphatic neovessels in allografts, whereas it can sustain continued hemangiogenesis.

CONCLUSIONS

The sustained presence of lymphatic vessels in HR host beds can facilitate host immunity against allografts and is likely associated with ongoing higher risk of rejection of these grafts in the long term, suggesting that therapeutic interventions targeting inflammation and lymphatic vessels need to be sustained long term in the HR corneal transplant setting.

Corneal Endothelial Cell Integrity in Precut Human Donor Corneas Enhanced by Autocrine Vasoactive Intestinal Peptide

PURPOSE

To demonstrate that vasoactive intestinal peptide (VIP), a corneal endothelial (CE) cell autocrine factor, maintains the integrity of corneal endothelium in human donor corneoscleral explants precut for endothelial keratoplasty.

METHODS

Twelve paired human donor corneoscleral explants used as control versus VIP-treated explants (10 nM, 30 minutes, 37°C) were shipped (4°C) to the Lions Eye Institute for Transplantation and Research for precutting (Moria CBM-ALTK Keratome), shipped back to the laboratory, and cultured in ciliary neurotrophic factor (CNTF, 0.83 nM, 37°C, 24 hours). Trephined endothelial discs (8-8.5 mm) were analyzed for differentiation markers (N-cadherin, CNTF receptor α subunit [CNTFRα], and connexin 43) by Western blot after a quarter of the discs from 4 paired explants were cut away and stained with alizarin red S for microscopic damage analysis. Two additional paired explants (6 days in culture) were stained for panoramic view of central CE damage.

RESULTS

VIP treatment increased N-cadherin and CNTFRα levels (mean ± SEM) to 1.38 ± 0.11-fold (P = 0.003) and 1.46 ± 0.22-fold (P = 0.03) of paired controls, respectively, whereas CE cell CNTF responsiveness in upregulation of connexin 43 increased to 2.02 ± 0.5 (mean ± SEM)-fold of the controls (P = 0.04). CE damage decreased from (mean ± SEM) 10.0% ± 1.2% to 1.6% ± 0.3% (P < 0.0001) and 9.1% ± 1.1% to 2.4% ± 1.0% (P = 0.0006). After 6 days in culture, the damage in whole CE discs decreased from 20.0% (control) to 5.5% (VIP treated).

CONCLUSIONS

VIP treatment before precut enhanced the preservation of corneal endothelium.

Prox1-GFP/Flt1-DsRed transgenic mice: an animal model for simultaneous live imaging of angiogenesis and lymphangiogenesis

The roles of angiogenesis in development, health, and disease have been studied extensively; however, the studies related to lymphatic system are limited due to the difficulty in observing colorless lymphatic vessels. But recently, with the improved technique, the relative importance of the lymphatic system is just being revealed. We bred transgenic mice in which lymphatic endothelial cells express GFP (Prox1-GFP) with mice in which vascular endothelial cells express DsRed (Flt1-DsRed) to generate Prox1-GFP/Flt1-DsRed (PGFD) mice. The inherent fluorescence of blood and lymphatic vessels allows for direct visualization of blood and lymphatic vessels in various organs via confocal and two-photon microscopy and the formation, branching, and regression of both vessel types in the same live mouse cornea throughout an experimental time course. PGFD mice were bred with CDh5CreERT2 and VEGFR2lox knockout mice to examine specific knockouts. These studies showed a novel role for vascular endothelial cell VEGFR2 in regulating VEGFC-induced corneal lymphangiogenesis. Conditional deletion of vascular endothelial VEGFR2 abolished VEGFA- and VEGFC-induced corneal lymphangiogenesis. These results demonstrate the potential use of the PGFD mouse as a powerful animal model for studying angiogenesis and lymphangiogenesis.

Therapeutic Potential of Ranibizumab in Corneal Neovascularization

Ranibizumab is a humanized, affinity-matured vascular endothelial growth factor (VEGF) antibody fragment that neutralizes all isoforms of VEGF and is FDA approved for use in ophthalmology. Recently it was suggested that ranibizumab may be useful in the treatment of corneal neovascularization, but in reality this therapy is not yet evidence based.

Proangiogenic Function of T Cells in Corneal Transplantation

BACKGROUND

Corneal neovascularization increases the risk of T cell-mediated allograft rejection. Here, we investigate whether T cells promote angiogenesis in transplantation.

METHODS

Conventional effector T cells were collected from draining lymph nodes of allogeneic or syngeneic corneal transplanted BALB/c mice. T cells were either cocultured with vascular endothelial cells (VECs) to assess VEC proliferation or used in a mixed lymphocyte reaction assay. Messenger RNA (mRNA) expression of vascular endothelial growth factor (VEGF)-A, -C, and VEGF receptor 2 (VEGF-R2) in VECs was assessed by real-time PCR. VEGF-A protein expression was determined by enzyme-linked immunosorbent assay. Flow cytometry was used to analyze VEGF-R2 expression in corneal CD31 cells, and VEGF-A and IFNγ expression in corneal CD4 T cells.

RESULTS

Allogeneic T cells from high-risk (HR) grafted mice induced more VEC proliferation than those from syngeneic transplant recipients (P = 0.03). Vascular endothelial growth factor-A mRNA and protein expression were higher in T cells from draining lymph nodes (P = 0.03 and P = 0.04, respectively) and cornea (protein; P = 0.04) of HR compared with low-risk (LR) grafted hosts. Vascular endothelial growth factor-A, VEGF-C, and VEGF-R2 mRNA expression were increased in VECs when cocultured with T cells from HR transplants compared with LR transplants and naive mice. In addition, IFNγ blockade in T cell/VEC coculture increased VEC proliferation and VEGF-A protein expression, whereas blocking VEGF-A significantly reduced VEC proliferation (P = 0.04).

CONCLUSIONS

Allogeneic T cells from corneal transplant hosts promote VEC proliferation, probably via VEGF-A signaling, whereas IFNγ shows an antiangiogenic effect. Our data suggest that T cells are critical mediators of angiogenesis in transplantation.

Efficacy of Subconjunctival Aflibercept Versus Bevacizumab for Prevention of Corneal Neovascularization in a Rat Model

PURPOSE

We aimed to evaluate the efficacy of subconjunctival aflibercept, a vascular endothelial growth factor trap compound, for the treatment of corneal neovascularization in a rat model.

METHODS

Chemical burn was produced in the central cornea of 31 male Sprague-Dawley rats. Animals were randomized to receive treatment with subconjunctival injection of 0.08 mL aflibercept (25 mg/mL), 0.05 mL bevacizumab (25 mg/mL), or 0.05 mL physiologic saline. Corneal neovascularization was evaluated on postinjury days 1, 3, 7, 9, and 13 by corneal photographs. The rats were killed on day 21 and samples were collected for histological and flat-mount immunofluorescence analyses.

RESULTS

In all rats, vascular sprouting began on day 3, reached maximum density on days 7-9, and spontaneously regressed thereafter. Mean burn area in the central cornea comprised ∼15% of the total corneal area. The aflibercept group had a significantly smaller relative area of neovascularization than both control group (P < 0.05, 12.27 ± 9.91, 29.66 ± 9.96 days 7) and bevacizumab group (P < 0.05, 12.27 ± 9.91, 21.27 ± 8.19 days 7 and 15.5 ± 10.25, 32.38 ± 9.44 days 9; Mann-Whitney test). On histological study, hematoxylin and eosin staining revealed blood vessels extending to the central cornea in the control and bevacizumab groups and limited to the periphery in the aflibercept group. Immunofluorescence study with an endothelial marker revealed a smaller area of staining in the aflibercept group.

CONCLUSIONS

Aflibercept effectively inhibits corneal neovascularization in a rat model of chemical burn-induced neovascularization and warrants further study for potential use in humans.

Update on the Management of High-Risk Penetrating Keratoplasty

PURPOSE OF REVIEW

In this article, we review the indications and latest management of high-risk penetrating keratoplasty.

RECENT FINDINGS

Despite the immune-privilege status of the cornea, immune-mediated graft rejection still remains the leading cause of corneal graft failure. This is particularly a problem in the high-risk graft recipients, namely patients with previous graft failure due to rejection and those with inflamed and vascularized corneal beds. A number of strategies including both local and systemic immunosuppression are currently used to increase the success rate of high-risk corneal grafts. Moreover, in cases of limbal stem cell deficiency, limbal stem cells transplantation is employed.

SUMMARY

Corticosteroids are still the top medication for prevention and treatment in cases of corneal graft rejection. Single and combined administration of immunosuppressive agents e.g. tacrolimus, cyclosporine and mycophenolate are promising adjunctive therapies for prolonging graft survival. In the future, cellular and molecular therapies should allow us to achieve immunologic tolerance even in high-risk grafts.

Topical Timolol Inhibits Corneal Neovascularization in Rabbits

Timolol is a non-selective beta-adrenergic antagonist that is similar to propranolol. The mechanism through which these drugs act on the regression of neovascularization is largely unknown. However, it is thought that the drugs may act through vascular endothelial growth factor signaling, vasoconstriction, and vascular endothelial cell apoptosis. The aim of this study was to determine the effect of timolol on corneal neovascularization in rabbits. Neovascularization was induced in the eyes of 20 rabbits. Next, the rabbits were divided into two groups: the timolol (experimental) group received eye drops containing timolol 0.5% twice per day; and the saline (control) group received saline drops twice per day for two weeks. After 7 days, the mean area of corneal neovascularization (presented as a percentage relative to baseline) was significantly lower in the timolol group than in the saline group (4.63 ± 4.61% versus 58.39 ± 6.31%, P < 0.001). After 2 weeks, the mean area of corneal neovascularization was 0.85 ± 1.33% in the timolol group and 1.73 ± 2.06% in the saline group (P = 0.315). After the first week of treatment, timolol significantly reduced the area of neovascularization compared to control. Timolol may increase the rate of recovery from corneal neovascularization.

Management of high-risk corneal transplantation

The cornea is the most commonly transplanted tissue in medicine. The main cause of corneal graft failure is allograft rejection. The incidence of graft rejection depends on the presence of high-risk characteristics, most notably corneal neovascularization. Although corneal grafting has high success rates in the absence of these risk factors, high-risk keratoplasty is associated with low success rates because of a high incidence of immune-mediated graft rejection. To improve the survival of high-risk corneal transplantation, various preoperative, intraoperative, and postoperative measures can be considered; however, the key step in the management of these grafts is the long-term use of local and/or systemic immunosuppressive agents. Although a number of immunosuppressive agents have been used for this purpose, the results vary significantly across different studies. This is partly due to the lack of an optimized method for their use, as well as the lack of a precise stratification of the degree of risk in each individual patient. New targeted biologic treatments, as well as tolerance-inducing methods, show promising horizons in the management of high-risk corneal transplantation in near future.

Differential Effects of Bevacizumab, Ranibizumab, and Aflibercept on the Viability and Wound Healing of Corneal Epithelial Cells

PURPOSE

This study compared the effects of 3 antivascular endothelial growth factor (VEGF) agents (bevacizumab, ranibizumab, and aflibercept) on corneal epithelial cell viability and wound healing using human corneal epithelial cells (HCECs).

METHODS

To determine the cytotoxic effects of anti-VEGF agents on HCECs, HCEC viability was determined at various concentrations of these agents. An in vitro migration assay was used to investigate the migration of HCECs treated with 3 anti-VEGF agents. The protein level of extracellular signal-regulated kinase was used to evaluate the effect of anti-VEGF treatment on cell proliferation. The protein levels of p38 mitogen-activated protein kinase (MAPK) were analyzed by Western blotting to investigate cell migration.

RESULTS

After 24 or 48 h of exposure, aflibercept treatment showed no apparent effect on cell viability; however, bevacizumab and ranibizumab treatment decreased cell viability at high concentrations (1 and 2 mg/mL). A migration assay showed that HCEC migration was different among the 3 anti-VEGF treatment groups. Bevacizumab significantly delayed HCEC migration. Western blotting showed that bevacizumab treatment decreased the expression levels of phosphorylated p38 MAPK.

CONCLUSIONS

Bevacizumab, the most widely used and investigated anti-VEGF agent, decreased epithelial cell migration and viability. Anti-VEGF agents other than bevacizumab might therefore be better for treating corneal neovascularization complicated with epithelial defects.

Current and Upcoming Therapies for Ocular Surface Chemical Injuries

Chemical injuries frequently result in vision loss, disfigurement, and challenging ocular surface complications. Acute interventions are directed at decreasing the extent of the injury, suppressing inflammation, and promoting ocular surface re-epithelialization. Chronically, management involves controlling inflammation along with rehabilitation and reconstruction of the ocular surface. Future therapies aimed at inhibiting neovascularization and promoting ocular surface regeneration should provide more effective treatment options for the management of ocular chemical injuries.

Intrastromal Injection of Bevacizumab in the Management of Corneal Neovascularization: About 25 Eyes

Introduction. Corneal neovessels are a major risk factor for corneal graft rejection, due to the loss of the immune privilege. The purpose of this study is to evaluate the effectiveness of intrastromal injection of bevacizumab in the treatment of corneal neovascularization. Material and Methods. This is a prospective study that included 25 eyes of 22 patients with deep corneal neovessels, treated with intrastromal injections of bevacizumab. Results. The average age of patients was 31 years ranging from 16 to 44 years. The causes of neovascularization were dominated by herpetic keratitis (10 cases). The evolution was marked by complete regress of neovessels in 16 patients, partial regress in 6 cases, and reduced opacity and improved visual acuity in 5 patients. No side effects were noted. Discussion. Short-term results demonstrated the effectiveness of intrastromal injection of bevacizumab in the treatment of corneal neovessels. It may be an option or a complement to other useful treatments in stabilizing or improving vision. Conclusion. Bevacizumab is an effective additional treatment for the improvement of corneal transplants prognosis with preoperative corneal neovascularization.

[Management of corneal neovascularization prior to corneal transplantation: Report of 112 cases]

INTRODUCTION

The avascular nature of the cornea results from a balance between angiogenic factors and anti-angiogenic factors. Under pathological conditions, this homeostasis can be disturbed, resulting in the onset of corneal neovascularization. The purpose of our study was to report our experience in the management of corneal neovascularization prior to keratoplasty.

MATERIALS AND METHODS

This is a prospective study of 112 patients with corneal neovascularization and candidates for possible corneal transplant.

RESULTS

The average age of patients was 38 years, ranging from 15 to 72 years. The etiologies of neovascularization were dominated by ocular trauma (26.8 %). In total, 48.33 % of patients had superficial neovascularization, 18.52 % moderately deep and 33.2 % deep neovascularization. All patients received topical corticosteroids, 29.4 % received subconjunctival injections of bevacizumab, and 22.32 % intrastromal bevacizumab injections. Clinical course was marked by a decrease in the percentage of corneal neovascularization compared to the total corneal surface area, from 45 % (between 16 and 82 %) to 28 % (between 0 and 69 %) at Day 120. There was no statistically significant improvement in visual acuity.

DISCUSSION

Corneal neovascularization is a major risk factor for graft rejection; its management is crucial prior to every keratoplasty.

CONCLUSION

Corneal neovascularization can lead to increased risk of graft rejection. Proper management increases the success rate of penetrating keratoplasty.

Quantitative proteomic analysis of mice corneal tissues reveals angiogenesis-related proteins involved in corneal neovascularization

Corneal neovascularization (CNV) was induced in Balb/c mice by alkali burns in the central area of the cornea with a diameter of 2.5mm. After fourteen days, the cornea from one eye was collected for histological staining for CNV examination, while the cornea from the other eye of the same mouse was harvested for proteomic analysis. The label-free quantitative proteomic approach was applied to analyze five normal corneal tissues (normal group mice n=5) and five corresponding neovascularized corneal tissues (model group mice n=5). A total of 2124 proteins were identified, and 1682 proteins were quantified from these corneal tissues. Among these quantified proteins, 290 proteins were significantly changed between normal and alkali burned corneal tissues. Of these significantly changed proteins, 35 were reported or predicted as angiogenesis-related proteins. Then, these 35 proteins were analyzed using Ingenuity Pathway Analysis Software, resulting in 26 proteins enriched and connected to each other in the protein-protein interaction network, such as Lcn-2, αB-crystallin and Serpinf1 (PEDF). These three significantly changed proteins were selected for further Western blotting validation. Consistent with the quantitative proteomic results, Western blotting showed that Lcn-2 and αB-crystallin were significantly up-regulated in CNV model, while PEDF was down-regulated. This study provided increased understanding of angiogenesis-related proteins involved in corneal vascular development, which will be useful in the ophthalmic clinic of specifically target angiogenesis.

Assessment of therapeutic options for reducing alkali burn-induced corneal neovascularization and inflammation

This article aims to review and provide the current knowledge of the possibilities of topical treatment of corneal neovascularization due to alkali burns, evidenced by laboratory experiments, in vitro studies, and clinical trials published in the specialized literature. Authors present clinically relevant treatment of corneal neovascularization used in clinical practice, potential antiangiogenic topical therapeutics against corneal neovascularization, which are under investigation, and anti-angiogenic gene-therapy.

Understanding lymphangiogenesis in knockout models, the cornea, and ocular diseases for the development of therapeutic interventions

A major focus of cancer research for several decades has been understand the ability of tumors to induce new blood vessel formation, a process known as angiogenesis. Unfortunately, only limited success has been achieved in the clinical application of angiogenesis inhibitors. We now know that lymphangiogenesis, the growth of lymphatic vessels, likely also plays a major role in tumor progression. Thus, therapeutic strategies targeting lymphangiogenesis or both lymphangiogenesis and angiogenesis may represent promising approaches for treating cancer and other diseases. Importantly, research progress toward understanding lymphangiogenesis is significantly behind that related to angiogenesis. A PubMed search of "angiogenesis" returns nearly 80,000 articles, whereas a search of "lymphangiogenesis" returns 2,635 articles. This stark contrast can be explained by the lack of molecular markers for identifying the invisible lymphatic vasculature that persisted until less than 2 decades ago, combined with the intensity of research interest in angiogenesis during the past half century. Still, significant strides have been made in developing strategies to modulate lymphangiogenesis, largely using ocular disease models. Here we review the current knowledge of lymphangiogenesis in the context of knockout models, ocular diseases, the biology of activators and inhibitors, and the potential for therapeutic interventions targeting this process.

A Comparative Study of Topical Mitomycin C, Cyclosporine, and Bevacizumab after Primary Pterygium Surgery

PURPOSE

To compare the recurrence rates and complications associated with instillation of topical mitomycin C, cyclosporine, and bevacizumab after primary pterygium surgery.

METHODS

Between July 2013 and June 2014, we performed surgery using the bare sclera method on 132 eyes (132 patients) with primary pterygium. We randomly selected 33 eyes (33 patients) and treated them with artificial tears four times a day for three months, 29 eyes (29 patients) were treated with topical 0.02% mitomycin C four times a day for five days, 34 eyes (34 patients) were treated with topical 0.05% cyclosporine four times a day for three months, and 36 eyes (36 patients) were treated with topical 2.5% bevacizumab four times a day for three months after surgery. We prospectively determined the recurrence rates of pterygium and complications at the six-month follow-up examination.

RESULTS

At six months after surgery, the recurrence rates in each group were as follows: 45.5% (15 eyes) in the control group, 10.3% (three eyes) in the mitomycin C group, 20.6% (seven eyes) in the cyclosporine group, and 41.7% (15 eyes) in the bevacizumab group (p = 0.004). No serious complications, except subconjunctival hemorrhages, were observed in any group.

CONCLUSIONS

Groups receiving topical 0.02% mitomycin C and 0.05% cyclosporine after surgery showed lower recurrence rates than the control group; however, no difference in recurrence rate was observed between the control group and the group receiving topical 2.5% bevacizumab after surgery.

[Current treatments for corneal neovascularization]

The extension of blood vessels into the normally avascular stroma defines corneal neovascularization. Though this phenomenon, pathophysiological and clinical features are well characterized, therapeutic modalities have been hindered by a lack of safe, efficacious and non-controversial treatments. In this literature review, we focus on available therapeutic options in light of recent evidence provided by animal and clinical studies. First, this review will focus on pharmacological treatments that target angiogenesis. The low cost and market availability of bevacizumab make it the first anti-angiogenic therapy choice, and it has demonstrable efficacy in reducing corneal neovascularization when administered topically or subconjunctivally. However, novel anti-angiogenic molecules targeting the intracellular pathways of angiogenesis (siRNA, antisense oligonucleotides) provide a promising alternative. Laser therapy (direct photocoagulation or photo-dynamic therapy) and fine needle diathermy also find a place in the treatment of stabilized corneal neovascularization alone or in association with anti-angiogenic therapy. Additionally, ocular surface reconstruction using amniotic membrane graft or limbal stem cell transplantation is essential when corneal neovascularization is secondary to primary or acquired limbal deficiency.

Suppression of In Vivo Neovascularization by the Loss of TRPV1 in Mouse Cornea

To investigate the effects of loss of transient receptor potential vanilloid receptor 1 (TRPV1) on the development of neovascularization in corneal stroma in mice. Blocking TRPV1 receptor did not affect VEGF-dependent neovascularization in cell culture. Lacking TRPV1 inhibited neovascularization in corneal stroma following cauterization. Immunohistochemistry showed that immunoreactivity for active form of TGFβ1 and VEGF was detected in subepithelial stroma at the site of cauterization in both genotypes of mice, but the immunoreactivity seemed less marked in mice lacking TRPV1. mRNA expression of VEGF and TGFβ1 in a mouse cornea was suppressed by the loss of TRPV1. TRPV1 gene ablation did not affect invasion of neutrophils and macrophage in a cauterized mouse cornea. Blocking TRPV1 signal does not affect angiogenic effects by HUVECs in vitro. TRPV1 signal is, however, involved in expression of angiogenic growth factors in a cauterized mouse cornea and is required for neovascularization in the corneal stroma in vivo.

Comparative study of tacrolimus and bevacizumab on corneal neovascularization in rabbits

PURPOSE

To compare the antiangiogenic effects of tacrolimus and bevacizumab on corneal neovascularization (CNV) in rabbits.

METHODS

Neovascularization was induced in 32 eyes of 16 rabbits by placing a suture in the corneal stroma. Seven days after suture placement, all rabbits were divided into 4 groups and were treated subconjunctivally with bevacizumab (AVA_sub) 0.05 mL (5 mg/0.05 mL), tacrolimus (TAC_sub) 0.05 mL (0.25 mg/0.05 mL), balanced salt solution (0.05 mL was subconjunctivally injected in 1 eye of each rabbit and applied by eye drops in the other eyes, control group), and tacrolimus eye drops (TAC_drop) (5 mg/5 mL applied 4 times daily). Digital photographs were obtained and surface area of CNV was measured 7 days after subconjunctival injections. Corneal specimens were analyzed histopathologically and were used to measure the concentration of vascular endothelial growth factor (VEGF), tumor necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), interleukin-1 beta (IL-1β), and monocyte chemoattractant protein 1 mRNA by reverse transcription polymerase chain reaction.

RESULTS

In digital photographs, the neovascularized area was decreased in all treatment groups (AVA_sub, 0.58; TAC_sub, 0.60; TAC_drop, 0.68) compared with the control group (balanced salt solution, 0.81). Histological examination showed markedly regressed new vessels in treatment groups, and immunohistochemical staining revealed weakly stained anti-VEGF and anti-F4/80 antibodies in treatment groups. In semiquantitative reverse transcription polymerase chain reaction, concentration of VEGF (AVA_sub, 0.24; TAC_drop, 0.18), TNF-α (AVA_sub, 0.19; TAC_sub, 0.24; TAC_drop 0.15), and IL-1β (AVA_sub, 0.19; TAC_sub, 0.33; TAC_drop, 0.18) mRNA were significantly lower in treatment groups than in the control group (VEGF, 0.47; TNF-α, 0.44; IL-1β, 0.87) (P < 0.05).

CONCLUSIONS

Topical and subconjunctival tacrolimus application may be useful in reducing CNV and have comparable effects to subconjunctival bevacizumab injection.

Two-photon microscopy of a Flt1 peptide-hyaluronate conjugate

AIM

Two-photon microscopy was performed to visualize ocular distribution of Flt1 peptide-hyaluronate (HA) conjugate micelles for eye drop treatment of corneal neovascularization.

MATERIALS & METHODS

Flt1 peptide-HA conjugate micelles were topically administered to the eye for two-photon microscopy and antiangiogenic effect assessment after silver nitrate cauterization.

RESULTS

In vivo two-photon microscopy revealed that Flt1 peptide-HA conjugate micelles were absorbed and remained on the corneal epithelia with an increased residence time, facilitating the corneal delivery of carboxyfluorescein succinimidyl ester (CFSE) as a model drug. Furthermore, repeated eye drops of Flt1 peptide-HA conjugate micelles showed comparable therapeutic effect to the subconjunctival injection on the corneal neovascularization.

DISCUSSION & CONCLUSION

We confirmed the feasibility of Flt1 peptide-HA conjugate micelles for eye drop treatment of corneal neovascularization.

Suberoylanilide hydroxamic acid suppresses inflammation-induced neovascularization

Histone deacetylases (HDACs) regulate gene transcription by modifying the acetylation of histone and nonhistone proteins. Deregulated expression of HDACs has been implicated in tumorigenesis and angiogenesis. In this study, we examined the effect of suberoylanilide hydroxamic acid (SAHA), a potent inhibitor of HDACs, on inflammatory corneal angiogenesis. In a mouse model of alkali-induced corneal neovascularization (CNV), topical application of SAHA to the injured corneas attenuated CNV. In addition, in vivo treatment with SAHA downregulated the expression of the pro-angiogenic factors vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), transforming growth factor beta 1 (TGFβ1), and epidermal growth factor (EGF), but upregulated the expression of the anti-angiogenic factors thrombospondin (TSP)-1, TSP-2, and ADAMTS-1 in the injured corneas. Furthermore, SAHA inhibited the expression of pro-angiogenic factors, migration, proliferation, and tube formation by human microvascular endothelial cells (HEMC-1) in vitro. These data indicate that SAHA has therapeutic potential for CNV.

A comparative study of different concentrations of topical bevacizumab on the recurrence rate of excised primary pterygium: a short-term follow-up study

The present study was undertaken to compare the pterygium recurrence rates after treatment with two different concentrations of topical bevacizumab in those who had undergone a primary pterygium excision. The 90 patients who underwent pterygium excision were enrolled in this prospective, placebo-controlled double-blinded interventional case series. The participants were randomly categorized into 3 groups each consisting of 30 subjects. 24 h after surgery, Group II and Group III received a total of 5 and 10 mg/mL dose of topical bevacizumab, respectively; whereas patients in Group I were administered only a placebo starting a day after surgery. Participants were instructed to instill their topical medicines 4 times a day for 1 week. The patients were examined for pterygium recurrence and complications at postoperative 1, 7, and 14 days as well as each month during the following year. Pterygia recurred in 14 patients (46.7 %) in Group I and in 4 patients (13.3 %) in Group II. No recurrence was observed in Group III during the follow-up period. The Kaplan-Meier survival analysis disclosed a significantly better outcome for those who had been treated with 10 mg/mL concentrations of bevacizumab (Mantel-Cox log rank analysis, P < 0.001). The mean recurrence time was not significantly different between Group I and Group II. No ocular or systemic complication developed till the end of follow-up. Thus, 10 mg/mL concentration of topical bevacizumab was more efficacious than 5 mg/mL dose in preventing pterygium recurrence.