Treatments for corneal neovascularization: a review

Immune reactions after modern lamellar (DALK, DSAEK, DMEK) versus conventional penetrating corneal transplantation

In the past decade, novel lamellar keratoplasty techniques such as Deep Anterior Lamellar Keratoplasty (DALK) for anterior keratoplasty and Descemet stripping automated endothelial keratoplasty (DSAEK)/Descemet membrane endothelial keratoplasty (DMEK) for posterior keratoplasty have been developed. DALK eliminates the possibility of endothelial allograft rejection, which is the main reason for graft failure after penetrating keratoplasty (PK). Compared to PK, the risk of endothelial graft rejection is significantly reduced after DSAEK/DMEK. Thus, with modern lamellar techniques, the clinical problem of endothelial graft rejection seems to be nearly solved in the low-risk situation. However, even with lamellar grafts there are epithelial, subepithelial and stromal immune reactions in DALK and endothelial immune reactions in DSAEK/DMEK, and not all keratoplasties can be performed in a lamellar fashion. Therefore, endothelial graft rejection in PK is still highly relevant, especially in the "high-risk" setting, where the cornea's (lymph)angiogenic and immune privilege is lost due to severe inflammation and pathological neovascularization. For these eyes, currently available treatment options are still unsatisfactory. In this review, we will describe currently used keratoplasty techniques, namely PK, DALK, DSAEK, and DMEK. We will summarize their indications, provide surgical descriptions, and comment on their complications and outcomes. Furthermore, we will give an overview on corneal transplant immunology. A specific focus will be placed on endothelial graft rejection and we will report on its incidence, clinical presentation, and current/future treatment and prevention options. Finally, we will speculate how the field of keratoplasty and prevention of corneal allograft rejection will develop in the future.

Corneal opacities in mice exposed to repeated contact procedures during ocular examinations

BACKGROUND

Cystine/glutamate exchanger (xCT) knockout mice are reported to exhibit an oxidative shift in the plasma cystine/cysteine ratio reminiscent of that seen in human plasma of ageing individuals. This suggests that the xCT knockout mouse is a model of accelerated ageing. The aim of this study was to examine the progression of age-related pathologies in the ocular tissues of wild-type mice and compare this to the xCT knockout mice.

METHODS

Wild-type and xCT knockout mice were examined longitudinally or as separate groups of animals at six weeks, three months, six months, nine months, and 12 months of age. All groups of mice were anaesthetised, intraocular pressure measured using the iCare TONOLAB rebound tonometer and eyes examined using the Micron IV system.

RESULTS

While the aim of the study was to determine if xCT knockout mice developed age-related pathologies earlier than wild-type mice, it was inadvertently discovered in the longitudinal cohort of animals, that the eyes developed corneal lesions in both groups of animals by six months of age, which obscured examination of the lens and retina. These lesions were not characteristic of age-related pathologies, but rather due to an external stressor. Lesions in the xCT knockout mice developed at an earlier age compared to wild-type mice, suggesting that loss of xCT exacerbates damage to the cornea, most likely caused by the rebound tonometer. When the same ocular procedures were performed on separate cohorts of mice of specific ages, no corneal lesions were detected for both groups of mice.

CONCLUSIONS

While it may seem advantageous to examine the same cohort of mice to monitor the development of age-related pathologies, the type of ophthalmic tests conducted needs to be carefully considered to avoid introducing pathologies that are inadvertently a result of the examination process itself.

Cucurbita argyrosperma Seed Extracts Attenuate Angiogenesis in a Corneal Chemical Burn Model

Severe corneal inflammation produces opacity or even perforation, scarring, and angiogenesis, resulting in blindness. In this study, we used the cornea to examine the effect of new anti-angiogenic chemopreventive agents. We researched the anti-angiogenic effect of two extracts, methanol (Met) and hexane (Hex), from the seed of Cucurbita argyrosperma, on inflamed corneas. The corneas of Wistar rats were alkali-injured and treated intragastrically for seven successive days. We evaluated: opacity score, corneal neovascularization (CNV) area, re-epithelialization percentage, and histological changes. Also, we assessed the inflammatory (cyclooxigenase-2, nuclear factor-kappaB, and interleukin-1β) and angiogenic (vascular endothelial growth factor A, VEGF-A; -receptor 1, VEGFR1; and -receptor 2, VEGFR2) markers. Levels of Cox-2, Il-1β, and Vegf-a mRNA were also determined. After treatment, we observed a reduction in corneal edema, with lower opacity scores and cell infiltration compared to untreated rats. Treatment also accelerated wound healing and decreased the CNV area. The staining of inflammatory and angiogenic factors was significantly decreased and related to a down-expression of Cox-2, Il-1β, and Vegf. These results suggest that intake of C. argyrosperma seed has the potential to attenuate the angiogenesis secondary to inflammation in corneal chemical damage.

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.

Efficacy of Sunitinib, Sunitinib-Hesperetin, and Sunitinib-Doxycycline Combinations on Experimentally-Induced Corneal Neovascularization

Purpose: To investigate the preventive effects of topical sunitinib, sunitinib-hesperetin and sunitinib-doxycycline combinations on corneal neovascularization (CNV), apoptosis and fibrosis in a corneal alkali burn model. Materials and Methods: The corneas of 32 Wistar albino rats were cauterized with silver nitrate to induce CNV. Four groups were created receiving artificial tears (sham), sunitinib (0.5 mg/ml), sunitinib-hesperetin (0.5 mg/ml-0.2 mg/ml), and sunitinib-doxycycline (0.5 mg/ml-20 mg/ml) treatments. Corneal photographs were taken on days 0, 7 and 15‎. Photographs of the cornea were digitally analyzed to measure the size of the neovascularization area in comparison to the total corneal surface area. On the 15th day, the animals were euthanized, and the eyes were enucleated for immunohistochemical staining to investigate neovascularization, apoptosis, and fibrosis. Results: CNV areas on the 7th day in the sunitinib (4.8% ± 0.07%) and sunitinib-hesperetin (1.1% ± 0.03%) groups were smaller than those in the sham group (33.9% ± 0.12%) (p = 0.001 and, p < 0.001 respectively). On the 15th day, the CNV area in the sunitinib-hesperetin (20.8% ± 0.37%) group was significantly smaller than that of the sham group (74.6% ± 0.32%) (p = 0.039). The combination groups had lower levels of VEGF, TUNEL and α-SMA positivity than the sunitinib monotherapy group. TUNEL positivity was lowest in the sunitinib-hesperetin and sunitinib-doxycycline groups, and α-SMA positivity was lowest in the sunitinib-hesperetin group. Conclusion: Topical sunitinib-hesperetin was more effective than sunitinib alone and the sunitinib-doxycycline combination in the treatment of CNV. The combination of sunitinib and hesperetin seems to be a promising treatment for preventing corneal fibrosis and apoptosis.

Mesoporous silica nanoparticles as a delivery system for improving antiangiogenic therapy

PURPOSE

Antiangiogenic drugs usually have short-acting efficacy and poor treatment compliance. The purpose of this study was to determine whether mesoporous silica nanoparticles (MSNs) could be utilized as a nanodrug delivery system for improving antiangiogenic therapy.

MATERIALS AND METHODS

MSN-encapsulated bevacizumab nanoparticles were prepared by the nanocasting strategy and characterized by Fourier transform infrared, transmission electron microscopy, and Brunauer-Emmett-Teller method. Encapsulation efficiency and drug loading efficiency of MSN-encapsulated bevacizumab nanoparticles were calculated. The pharmacokinetics, cytotoxicity, and tissue toxicity were evaluated in vitro and in vivo. The antiangiogenic effects of MSN-bevacizumab nanoparticles were evaluated in vitro and in vivo.

RESULTS

MSN encapsulation could prolong the residency of bevacizumab in vitreous/aqueous humor and maintain the long-lasting drug concentration. MSN-encapsulated bevacizumab nanoparticles did not show any obvious cytotoxicity and tissue toxicity. MSN-encapsulated bevacizumab nanoparticles were more effective than bevacizumab in suppressing vascular endothelial growth factor-induced endothelial cell proliferation, migration, and tube formation in vitro. MSN-encapsulated bevacizumab nanoparticles showed sustained inhibitory effects on corneal neovascularization and retinal neovascularization in vivo.

CONCLUSION

This study provides a novel strategy of encapsulating bevacizumab to protect and deliver it, which could increase the time between administration and formulation shelf-life. MSN-encapsulated bevacizumab is a promising drug delivery alternative of antiangiogenic therapy.

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.

Treatment of corneal neovascularization with topical aflibercept in a case of exposure keratopathy following cerebellar astrocytoma surgery

In this report, we report the case of a 7-year-old boy with corneal neovascularization due to exposure keratopathy following cerebellar astrocytoma surgery. Corneal surface healing was achieved with topical treatment and therapeutic contact lens, after which topical steroid was administered for stromal haze and corneal neovascularization. After 2 months of steroid therapy failed, corneal neovascularization responded well to topical aflibercept administration, showing complete regression.

Topical axitinib is a potent inhibitor of corneal neovascularization

BACKGROUND

This study evaluated the effects of topically applied axitinib, a tyrosine kinase inhibitor, in an experimental model of corneal neovascularization (CNV).

METHODS

A total of 48 New Zealand rabbits were used. CNV was induced by placing five silk sutures in the upper cornea of one eye per rabbit. Rabbits were randomized into four groups (12 rabbits each): 0.9% saline (control group), 0.02 mg/mL axitinib, 0.35 mg/mL axitinib and 0.5 mg/mL axitinib groups. All treatments were administered three times daily for 14 days. Photographs were taken using a slit lamp on days 7 and 14. The area of neovascularization was measured in mm2 , as the percentage of total corneal area and as the percentage of corneal surface covered by sutures (SCS).

RESULTS

On day 14, the CNV area in the control group (31.50 ± 7.47 mm2 ; 115.00 ± 22.55% of the corneal SCS) was larger than that in the 0.02 mg/mL axitinib group (19.20 ± 8.92 mm2 ; 73.89 ± 34.98%), the 0.35 mg/mL axitinib group (8.83 ± 3.92 mm2 ; 31.90 ± 13.59%) and the 0.5 mg/mL axitinib group (5.12 ± 3.97 mm2 ; 18.38 ± 13.65%). Compared with saline, CNV was inhibited 39.04% by 0.02 mg/mL axitinib, 71.96% by 0.35 mg/mL axitinib and 84.73% by 0.5 mg/mL axitinib.

CONCLUSION

Topical administration of the three axitinib concentrations inhibited CNV in rabbits, blocking both vascular endothelial growth factor and platelet-derived growth factor pathways. Axitinib at 0.5 mg/mL induced profound inhibition of corneal angiogenesis.

Method for selective quantification of immune and inflammatory cells in the cornea using flow cytometry

The cornea serves as a protective surface against the environment (i.e., allergens, pollutants, desiccation and microorganisms) and promotes vision, made possible by corneal transparency. This protocol describes corneal preparation for flow cytometry to assess cells localized in the cornea. Our model details the process, from determining how many corneas are needed in the experiment to corneal excision to digestion and staining of the cornea cells. The simplicity of the model allows for systematic analysis of different corneal mechanisms of immunity, inflammation, angiogenesis and wound healing. In corneal transplantation, residential immune and inflammatory cells are key to the mechanisms that underlie angiogenesis, opacity, and graft rejection. In addition, this model can also elucidate cellular mechanisms mediating corneal graft outcomes and wound healing. Lastly, this model can be used to analyze the efficacy of new medications such as instillation and subconjunctival injections and assess the potential of therapeutic molecules to enhance graft survival and wound healing in vivo.

The long-term effect of tacrolimus on alkali burn-induced corneal neovascularization and inflammation surpasses that of anti-vascular endothelial growth factor

Purpose

To investigate the effect of tacrolimus in alkali burn-induced corneal neovascularization (NV) and inflammation and to compare with anti-vascular endothelial growth factor (anti-VEGF).

Methods

After corneal alkali-burn, 84 Wistar rats were randomly divided into three groups and received either saline solution or 0.05% tacrolimus (0.5 mg/mL) four times daily, or subconjunctival anti-VEGF injection (0.5 mg/0.05 mL). Corneal NV, opacity and epithelial defects, the status of inflammation, and the levels of proinflammatory and angiogenic cytokines were assessed on Days 3, 7, 14 and 28 post-injury.

Results

Compared with the control, tacrolimus significantly reduced corneal NV on Days 7, 14 and 28 post-injury, and anti-VEGF significantly reduced corneal NV at each assessment. Nevertheless, the tacrolimus group had significantly less corneal NV than the anti-VEGF group on Days 14 and 28. Furthermore, both tacrolimus and anti-VEGF significantly decreased the VEGF-A expression on Days 7 and 14, with no significant difference between the two groups. Moreover, corneal inflammatory response was alleviated, and corneal opacity and epithelial defects were significantly reduced by tacrolimus. Additionally, the expression of IL-1β, IL-6, monocyte chemotactic protein-1, macrophage inflammatory protein-1α and TGF-β were significantly decreased by tacrolimus.

Conclusion

Our findings suggested that 0.05% tacrolimus suspension eye drops effectively reduced alkali burn-induced corneal NV and inflammation, with a better effect than subconjunctival anti-VEGF injections on Days 14 and 28.

Prevention of corneal neovascularization by subconjunctival injection of avastin® loaded thermosensitive hydrogels in rabbit model

The antibody avastin® (Ava) has been clinically to treat various intraocular neovascular diseases, but suffering from the rapid clearance and short shelf-life of Ava in the requirement of frequent administration. In the present study, we reports the sustained release of Ava from a thermosensitive hydrogel based on poly(ethylene glycol)-poly(ɛ-caprolactone)-poly(ethylene glycol) (PECE) copolymer for the control of corneal neovascularization in rabbit model. Ava were physically mixed with PECE aqueous solution at 4 °C, and resulting Ava-PECE solution showed a sol-gel transition at physiological temperature (37 °C). In vitro release study indicated that Ava-PECE hydrogel provided a sustained release of Ava up to 28 days and the drug release behavior could be finely modulated by the change of PECE concentration. A single subconjunctival injection of PECE hydrogel hardly caused the change of intraocular pressure and corneal endothelial morphology during the entire study period. Intraocular pharmacokinetic analysis suggested that the Ava-PECE hydrogel provided a relatively higher Ava concentration in cornea over Ava solution up to 14 days. In addition, anti-angiogenic effects of the Ava-PECE hydrogel in a suture-induced corneal neovascularization rabbit model indicated that the Ava-PECE hydrogel treatment exhibited superior anti-angiogenic efficacy over Ava solution treatment by decreasing the area ratio of neovascularization on 17 days. Overall, the proposed Ava-PECE hydrogel acting a sustained drug delivery system might be a promising vehicle for the treatment of corneal neovascularization.

Transcriptome Profiling of Neovascularized Corneas Reveals miR-204 as a Multi-target Biotherapy Deliverable by rAAVs

Corneal neovascularization (NV) is the major sight-threatening pathology caused by angiogenic stimuli. Current drugs that directly target pro-angiogenic factors to inhibit or reverse the disease require multiple rounds of administration and have limited efficacies. Here, we identify potential anti-angiogenic corneal microRNAs (miRNAs) and demonstrate a framework that employs discovered miRNAs as biotherapies deliverable by recombinant adeno-associated viruses (rAAVs). By querying differentially expressed miRNAs in neovascularized mouse corneas induced by alkali burn, we have revealed 39 miRNAs that are predicted to target more than 5,500 differentially expressed corneal mRNAs. Among these, we selected miR-204 and assessed its efficacy and therapeutic benefit for treating injured corneas. Our results show that delivery of miR-204 by rAAV normalizes multiple novel target genes and biological pathways to attenuate vascularization of injured mouse cornea. Importantly, this gene therapy treatment alternative is efficacious and safe for mitigating corneal NV. Overall, our work demonstrates the discovery of potential therapeutic miRNAs in corneal disorders and their translation into viable treatment alternatives.

Precise long non-coding RNA modulation in visual maintenance and impairment

Long non-coding RNAs (lncRNAs) are remarkably powerful, flexible and pervasive cellular regulators. With the help of cheaper RNA-seq, high-throughput screening of lncRNAs has become widely applied and has identified large numbers of specific lncRNAs in various physiological or pathological processes. Vision is known to be a complex and vital perception that comprises 80% of the sensory information we receive. A consensus has been reached that normal visual maintenance and impairment are primarily driven by gene regulation. Recently, it has become understood that lncRNAs are key regulators in most biological processes, including cell proliferation, apoptosis, differentiation, immune responses, oxidative stress and inflammation. Our review is intended to provide insight towards a comprehensive view of the precise modulation of lncRNAs in visual maintenance and impairment. We also highlight the challenges and future directions in conducting lncRNA studies, particularly in patients whose lncRNAs may hold expanded promise for diagnostic, prognostic and therapeutic applications.

Targeted intracorneal delivery-Biodistribution of triamcinolone acetonide following topical iontophoresis of cationic amino acid ester prodrugs

The aim was to investigate intracorneal iontophoresis of biolabile triamcinolone acetonide (TA) amino acid ester prodrugs (TA-AA). Arginine and lysine esters of TA (TA-Arg and TA-Lys, respectively) were synthesized and characterized; quantification was performed by HPLC-UV and UHPLC-MS/MS. The aqueous solubility of the prodrugs (at pH 5.5) was ∼1000-fold greater than TA. Anodal iontophoresis (10min at 3mA/cm²) of TA-AA was investigated using isolated porcine cornea. Although no statistically significant difference was observed in total intracorneal delivery of TA (468.25±59.70 and 540.85±79.16nmol_TA/cm², for TA-Arg and TA-Lys, respectively), the different susceptibilities of the prodrugs to hydrolysis influenced intracorneal biodistribution. Quantification of TA in twenty-five 40μm thick corneal lamellae revealed significantly deeper penetration of TA following TA-Lys iontophoresis. Its superior resistance to hydrolysis enabled sustained electromigration into the deeper cornea suggesting judicious prodrug selection might enable targeted regioselective drug delivery. The intracorneal biodistribution following anodal iontophoresis of TA-Arg (2.3mM; 10min, 3mA/cm²) was visualized by full field optical coherence tomography providing qualitative confirmation of the extensive intracorneal penetration of TA. Short duration iontophoresis of TA-AA prodrugs may improve deep corneal bioavailability and efficacy in vivo, constituting a "single-shot" treatment option for corneal allograft rejection.

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.

Tissue and cellular characterisation of nucleolin in a murine model of corneal angiogenesis

PURPOSE

Corneal neovascularisation (CNV), with consequent loss of transparency, is due to an imbalance of proangiogenic factors. Cell-surface nucleolin (NCL) has been associated with neo-angiogenesis. There are studies identifying NCL translocation from nucleus to the cell surface, which is essential for endothelial cell proliferation. To find the possible role of NCL in the generation of corneal neovessels, the aim of this study is to characterise the NCL presence and cell-localisation in non-injured corneas, as well as to describe the changes in NCL cell and tissue localisation in CNV, and to analyse the effect of bevacizumab on NCL cellular and tissular distribution.

METHODS

Suture-induced CNV was performed in mice. The corneal tissues were obtained and the histological and co-immunofluorescence assays were performed using different proteins, such as CD31, cadherin and isolectin B4. To determine the possible role of VEGF in NCL presence and localisation in our CNV model, bevacizumab was concomitantly used.

RESULTS

Nucleolin was principally observed in the nucleus of the basal epithelial cells of normal corneas. Interestingly, angiogenesis-induced changes were observed in the localisation of NCL, not only in tissue but also at the cellular level where NCL was extranuclear in epithelial cells, stromal cells and neovessels. In contrast, these changes were reverted when bevacizumab was used. Besides, NCL was able to stain only aberrant corneal neovessels in comparison with retinal vessels.

CONCLUSIONS

NCL mobilisation outside the nucleus during angiogenesis could have a possible role as a proangiogenic molecule in the corneal tissue.

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.

MK2 inhibitor reduces alkali burn-induced inflammation in rat cornea

MK2 activation by p38 MAPK selectively induces inflammation in various diseases. We determined if a MK2 inhibitor (MK2i), improves cornea wound healing by inhibiting inflammation caused by burning rat corneas with alkali. Our study, for the first time, demonstrated that MK2i inhibited alkali burn-induced MK2 activation as well as rises in inflammation based on: a) blunting rises in inflammatory index, inflammatory cell infiltration, ED1⁺ macrophage and PMN⁺ neutrophil infiltration; b) suppressing IL-6 and IL-1β gene expression along with those of macrophage inflammatory protein-1α (MIP-1α), intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1); c) reducing angiogenic gene expression levels and neovascularization (NV) whereas anti-angiogenic PEDF levels increased. In addition, this study found that MK2i did not affect human corneal epithelial cell (HCEC) proliferation and migration and had no detectable side effects on ocular surface integrity. Taken together, MK2i selectively inhibited alkali burn-induced corneal inflammation by blocking MK2 activation, these effects have clinical relevance in the treatment of inflammation related ocular surface diseases.

[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.

Novel Insights into the Role of Long Noncoding RNA in Ocular Diseases

Recent advances have suggested that long noncoding RNAs (lncRNAs) are differentially expressed in ocular tissues and play a critical role in the pathogenesis of different types of eye diseases. Here, we summarize the functions and mechanisms of known aberrantly-expressed lncRNAs and present a brief overview of relevant reports about lncRNAs in such ocular diseases as glaucoma, proliferative vitreoretinopathy (PVR), diabeticretinopathy (DR), and ocular tumors. We intend to highlight comprehensive studies that provide detailed data about the mechanisms of lncRNAs, their applications as diagnostic or prognostic biomarkers, and their potential therapeutic targets. Although our understanding of lncRNAs is still in its infancy, these examples may provide helpful insights into the methods by which lncRNAs interfere with ocular diseases.

Inhibition of Pathologic Corneal Neovascularization by Topical Application of a Novel Peptide In Vivo

PURPOSE

To investigate the antiangiogenic effect of topical application of H-KI20, a novel 20-amino acid peptide from the hepatocyte growth factor, on 2 animal models of corneal neovascularization (NV), and its possible toxic effects on the cornea and conjunctiva.

METHODS

The antiangiogenic effect of topical H-KI20 in vivo was studied on corneal NV induced by a mouse corneal micropocket assay and rat intrastromal suture model. In each model, H-KI20, scrambled control peptide H-KI20S, bevacizumab, and phosphate buffer solution (PBS) were applied topically 4 times a day. Corneal NV was examined, photographed, and analyzed. Histological analysis of the corneas was performed. Tear film breakup time and gross and histological examinations were used to study the possible toxicity of topical H-KI20.

RESULTS

Topical application of H-KI20 significantly inhibited corneal NV induced by vascular endothelial growth factor (VEGF), and intrastromal suture (P < 0.01 vs. the PBS group), and the area of corneal NV was suppressed by 80.3% and 83.6%, respectively (PBS group as 100%). No significant difference was found between 1.0 mg/mL H-KI20 and 10 mg/mL bevacizumab (P > 0.05). Both hematoxylin and eosin and CD34 staining revealed fewer new blood vessels in the H-KI20 and bevacizumab groups. Tear film breakup time and histological examinations showed that H-KI20 had no obvious toxic effects on the cornea and conjunctiva in vivo.

CONCLUSIONS

The novel peptide H-KI20 is an effective and safe inhibitor of corneal NV. It may provide a promising alternative for ocular topical antiangiogenic therapy.

NADPH oxidase 2 plays a role in experimental corneal neovascularization

Corneal neovascularization, the growth of new blood vessels in the cornea, is a leading cause of vision impairment after corneal injury. Neovascularization typically occurs in response to corneal injury such as that caused by infection, physical trauma, chemical burns or in the setting of corneal transplant rejection. The NADPH oxidase enzyme complex is involved in cell signalling for wound-healing angiogenesis, but its role in corneal neovascularization has not been studied. We have now analysed the role of the Nox2 isoform of NADPH oxidase in corneal neovascularization in mice following chemical injury. C57BL/6 mice aged 8-14 weeks were cauterized with an applicator coated with 75% silver nitrate and 25% potassium nitrate for 8 s. Neovascularization extending radially from limbal vessels was observed in corneal whole-mounts from cauterized wild type mice and CD31+ vessels were identified in cauterized corneal sections at day 7. In contrast, in Nox2 knockout (Nox2 KO) mice vascular endothelial growth factor-A (Vegf-A), Flt1 mRNA expression, and the extent of corneal neovascularization were all markedly reduced compared with their wild type controls. The accumulation of Iba-1+ microglia and macrophages in the cornea was significantly less in Nox2 KO than in wild type mice. In conclusion, we have demonstrated that Nox2 is implicated in the inflammatory and neovascular response to corneal chemical injury in mice and clearly VEGF is a mediator of this effect. This work raises the possibility that therapies targeting Nox2 may have potential for suppressing corneal neovascularization and inflammation in humans.

Inhibition of Corneal Neovascularization by Subconjunctival Injection of Fc-Endostatin, a Novel Inhibitor of Angiogenesis

We assessed the antiangiogenic effects of subconjunctival injection of Fc-endostatin (FcE) using a human vascular endothelial growth factor-induced rabbit corneal neovascularization model. Angiogenesis was induced in rabbit corneas through intrastromal implantations of VEGF polymer implanted 2 mm from the limbus. NZW rabbits were separated into groups receiving twice weekly subconjunctival injections of either saline; 25 mg/mL bevacizumab; 2 mg/mL FcE; or 20 mg/mL FcE. Corneas were digitally imaged at 5 time points. An angiogenesis index (AI) was calculated (vessel length (mm) × vessel number score) for each observation. All treatment groups showed a significant decrease in the vessel length and AI compared to saline on all observation days (P < 0.001). By day 15, FcE 2 inhibited angiogenesis significantly better than FcE 20 (P < 0.01). There was no significant difference between FcE 2 and BV, although the values trended towards significantly increased inhibition by BV. BV was a significantly better inhibitor than FcE 20 by day 8 (P < 0.01). FcE was safe and significantly inhibited new vessel growth in a rabbit corneal neovascularization model. Lower concentration FcE 2 exhibited better inhibition than FcE 20, consistent with previous FcE studies referencing a biphasic dose-response curve. Additional studies are necessary to further elucidate the efficacy and clinical potential of this novel angiogenesis inhibitor.

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.

Effects of lapatinib and trastuzumab on vascular endothelial growth factor in experimental corneal neovascularization

BACKGROUND

The aim of this study was to compare the effects of lapatinib and trastuzumab on vascular endothelial growth factor on experimental corneal neovascularization.

METHODS

A total of 35 Wistar albino rats were randomly divided into five groups, each containing seven animals. Corneas of rats in the control group were not cauterized and did not receive any treatment. A silver nitrate pencil was applied on the right corneas of rats in the non-control groups to induce corneal neovascularization. Rats in the sham, lapatinib, trastuzumab and lapatinib +  trastuzumab groups were administered systemic saline, 50 mg/kg lapatinib once a day orally by gavage, 4 mg/kg trastuzumab once a day intraperitoneally, or 50 mg/kg lapatinib once a day orally by gavage together with 4 mg/kg trastuzumab once a day intraperitoneally, respectively, for 7 days. Rats were sacrificed on the eighth day, and corneas were excised using a 4-mm punch trephine. Vascular endothelial growth factor immunostaining in the corneal epithelial and stromal layers was evaluated. Staining intensities were determined semi-quantitatively, and corneal vascular endothelial growth factor levels were measured by enzyme-linked immunosorbent assay.

RESULTS

The mean immunostaining intensities of epithelial and stromal vascular endothelial growth factor in the control group were significantly lesser than those in the sham group (P < 0.05). The mean immunostaining intensities of epithelial and stromal vascular endothelial growth factor and vascular endothelial growth factor enzyme-linked immunosorbent assay levels of corneas in all treatment groups (lapatinib, trastuzumab and lapatinib + trastuzumab groups) were lesser than those in the sham group (P < 0.05); however, it was similar to those in the control group (P > 0.05).

CONCLUSIONS

It is suggested that systemically administered lapatinib is more effective than systemically administered trastuzumab in preventing corneal neovascularization.

Steroids and Immunosuppressant Agents Do Not Affect Indirect Revascularization in Quasi-Moyamoya Disease Associated with Pure Red Cell Aplasia: A Case Report

A 31-year-old woman with pure red cell aplasia presented with motor aphasia and right homonymous hemianopia due to a left temporal and parietal lobe infarction. Magnetic resonance angiography revealed an occlusion of the left anterior and middle cerebral artery, with the development of moyamoya vessels. She was diagnosed with quasi-moyamoya disease and subsequently underwent direct and indirect anastomosis surgery, while continuing steroid and immunosuppressant therapy for pure red cell aplasia. The postoperative course was uneventful, and follow-up cerebral angiography 6 months after the surgery revealed the development of neovascularization through an indirect anastomosis. Neovascularization can be induced while the patient is receiving steroid and immunosuppressant therapy in quasi-moyamoya disease.

Paxillin regulates vascular endothelial growth factor A-induced in vitro angiogenesis of human umbilical vein endothelial cells

The purpose of the present study was to investigate the role of paxillin in the vascular endothelial growth factor A (VEGF-A)-induced adhesion, proliferation, migration and capillary formation of endothelial cells (ECs) in vitro. Human umbilical vein ECs (HUVECs) were used to evaluate these four processes in vitro. The HUVECs were either mock-transfected (control), transfected with scramble small interference RNA (siRNA) or transfected with siRNA specifically targeting paxillin. VEGF-A (20 ng/ml) was used to stimulate angiogenesis. The VEGF-A treatment significantly increased the adhesion, proliferation, migration and tube formation of the HUVECs in the control and scramble siRNA groups, whereas the siRNA-mediated knockdown of paxillin inhibited these VEGF-A-induced effects. Paxillin is essential for VEGF-A-mediated angiogenesis in ECs and its inhibition may be a potential target for antiangiogenic therapies.

Ocular delivery of macromolecules

Biopharmaceuticals are making increasing impact on medicine, including treatment of indications in the eye. Macromolecular drugs are typically given by physician-administered invasive delivery methods, because non-invasive ocular delivery methods, such as eye drops, and systemic delivery, have low bioavailability and/or poor ocular targeting. There is a need to improve delivery of biopharmaceuticals to enable less-invasive delivery routes, less-frequent dosing through controlled-release drug delivery and improved drug targeting within the eye to increase efficacy and reduce side effects. This review discusses the barriers to drug delivery via various ophthalmic routes of administration in the context of macromolecule delivery and discusses efforts to develop controlled-release systems for delivery of biopharmaceuticals to the eye. The growing number of macromolecular therapies in the eye needs improved drug delivery methods that increase drug efficacy, safety and patient compliance.

Intrastromal delivery of bevacizumab using microneedles to treat corneal neovascularization

PURPOSE

This study tested the hypothesis that highly targeted intrastromal delivery of bevacizumab using coated microneedles allows dramatic dose sparing compared with subconjunctival and topical delivery for treatment of corneal neovascularization.

METHODS

Stainless steel microneedles 400 μm in length were coated with bevacizumab. A silk suture was placed in the cornea approximately 1 mm from the limbus to induce corneal neovascularization in the eyes of New Zealand white rabbits that were divided into different groups: untreated, microneedle delivery, topical eye drop, and subconjunctival injection of bevacizumab. All drug treatments were initiated 4 days after suture placement and area of neovascularization was measured daily by digital photography for 18 days.

RESULTS

Eyes treated once with 4.4 μg bevacizumab using microneedles reduced neovascularization compared with untreated eyes by 44% (day 18). Eyes treated once with 2500 μg bevacizumab using subconjunctival injection gave similar results to microneedle-treated eyes. Eyes treated once with 4.4 μg subconjunctival bevacizumab showed no significant effect compared with untreated eyes. Eyes treated with 52,500 μg bevacizumab by eye drops three times per day for 14 days reduced the neovascularization area compared with untreated eyes by 6% (day 18), which was significantly less effective than the single microneedle treatment. Visual exam and histological analysis showed no observable effect of microneedle treatment on corneal transparency or microanatomical structure.

CONCLUSIONS

This study shows that microneedles can target drug delivery to corneal stroma in a minimally invasive way and demonstrates effective suppression of corneal neovascularization after suture-induced injury using a much lower dose compared with conventional methods.

Small-interfering RNAs (siRNAs) as a promising tool for ocular therapy

RNA interference (RNAi) can be used to inhibit the expression of specific genes in vitro and in vivo, thereby providing an extremely useful tool for investigating gene function. Progress in the understanding of RNAi-based mechanisms has opened up new perspectives in therapeutics for the treatment of several diseases including ocular disorders. The eye is currently considered a good target for RNAi therapy mainly because it is a confined compartment and, therefore, enables local delivery of small-interfering RNAs (siRNAs) by topical instillation or direct injection. However, delivery strategies that protect the siRNAs from degradation and are suitable for long-term treatment would be help to improve the efficacy of RNAi-based therapies for ocular pathologies. siRNAs targeting critical molecules involved in the pathogenesis of glaucoma, retinitis pigmentosa and neovascular eye diseases (age-related macular degeneration, diabetic retinopathy and corneal neovascularization) have been tested in experimental animal models, and clinical trials have been conducted with some of them. This review provides an update on the progress of RNAi in ocular therapeutics, discussing the advantages and drawbacks of RNAi-based therapeutics compared to previous treatments.

Inhibitory effects of regorafenib, a multiple tyrosine kinase inhibitor, on corneal neovascularization

AIM

To evaluate the inhibitory effects of regorafenib (BAY 73-4506), a multikinase inhibitor, on corneal neovascularization (NV).

METHODS

Thirty adult male Sprague-Dawley rats weighing 250-300 g, were used. Corneal NV was induced by NaOH in the left eyes of each rat. Following the establishment of alkali burn, the animals were randomized into five groups according to topical treatment. Group 1 (n = 6) received 0.9% NaCl, Group 2 (n = 6) received dimethyl sulfoxide, Group 3 (n = 6) received regorafenib 1 mg/mL, Group 4 (n =6) received bevacizumab 5 mg/mL and Group 5 (n = 6) received 0.1% dexamethasone phosphate. On the 7d, the corneal surface covered with neovascular vessels was measured on photographs as the percentage of the cornea's total area using computer-imaging analysis. The corneas obtained from rats were semiquantitatively evaluated for caspase-3 and vascular endothelial growth factor by immunostaining.

RESULTS

A statistically significant difference in the percent area of corneal NV was found among the groups (P <0.001). Although the Group 5 had the smallest percent area of corneal NV, there was no difference among Groups 3, 4 and 5 (P >0.005). There was a statistically significant difference among the groups in apoptotic cell density (P = 0.002). The staining intensity of vascular endothelial growth factor in the epithelial and endothelial layers of cornea was significantly different among the groups (P <0.05). The staining intensity of epithelial and endothelial vascular endothelial growth factor was significantly weaker in Groups 3, 4 and 5 than in Groups 1 and 2.

CONCLUSION

Topical administration of regorafenib 1 mg/mL is partly effective for preventing alkali-induced corneal NV in rats.

An alkali-burn injury model of corneal neovascularization in the mouse

Under normal conditions, the cornea is avascular, and this transparency is essential for maintaining good visual acuity. Neovascularization (NV) of the cornea, which can be caused by trauma, keratoplasty or infectious disease, breaks down the so called 'angiogenic privilege' of the cornea and forms the basis of multiple visual pathologies that may even lead to blindness. Although there are several treatment options available, the fundamental medical need presented by corneal neovascular pathologies remains unmet. In order to develop safe, effective, and targeted therapies, a reliable model of corneal NV and pharmacological intervention is required. Here, we describe an alkali-burn injury corneal neovascularization model in the mouse. This protocol provides a method for the application of a controlled alkali-burn injury to the cornea, administration of a pharmacological compound of interest, and visualization of the result. This method could prove instrumental for studying the mechanisms and opportunities for intervention in corneal NV and other neovascular disorders.

Inhibitory effects of topical cyclosporine A 0.05% on immune-mediated corneal neovascularization in rabbits

BACKGROUND

We aimed to study the inhibitory effects of topical cyclosporine A (CsA) 0.05% on immune-mediated corneal neovascularization, and to compare its efficacy with those of dexamethasone 0.1% and bevacizumab 0.5%.

METHODS

Immune-mediated corneal neovascularization was created in 36 right eyes of 36 rabbits. The rabbits were then randomized into four groups. Group I received CsA 0.05%, Group II received dexamethasone 0.1%, Group III received bevacizumab 0.5%, and Group IV received isotonic saline twice a day for 14 days. The corneal surface covered with neovascular vessels was measured on the photographs. The rabbits were then sacrificed and the corneas excised. Paraffin-embedded sections were stained with hematoxylin-eosin and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay.

RESULTS

The means of percent area of corneal neovascularization in Group I, II, III, and IV were 24.4%, 5.9%, 37.1%, and 44.1%, respectively. The inhibitory effect of CsA 0.05% was found to be better than the effect found in the bevacizumab 0.5% and control groups (p = 0.03 and p = 0.02, respectively). CsA 0.05% was found to have significantly lesser inhibitory effects on corneal neovascularization than dexamethasone 0.1% (p < 0.001). Apoptotic cell density was higher in Group III and Group IV than in Group I and Group II. There was no difference between Group I and Group II in terms of apoptotic cell density (p = 0.7).

CONCLUSIONS

Topical CsA 0.05% was shown to have an inhibitory effect on immune-mediated corneal neovascularization in rabbits.

Comparison of subconjunctivally injected bevacizumab, ranibizumab, and pegaptanib for inhibition of corneal neovascularization in a rat model

AIM

To compare the efficacies of subconjunctival bevacizumab, ranibizumab, and pegaptanib sodium injections for the inhibition of corneal neovascularization in an experimental rat model.

METHODS

Sixteen corneas of 16 rats were chemically cauterized and randomized into four groups: bevacizumab group that treated with 0.05mL/1.25mg bevacizumab, ranibizumab group that treated with 0.05mL/0.5mg ranibizumab, pegaptanib group that treated with 0.05mL/0.15mg pegaptanib sodium, and control group that treated with 0.05mL saline solution. Digital photographs of the corneas were taken and analyzed using an image analysis software program. All corneas were excised and examined histologically on the 15(th) day.

RESULTS

Each treatment group had significantly less neovascularized corneal areas and fewer blood vessels than the control group (all P<0.05). In addition, bevacizumab group had significantly less neovascularized corneal areas and fewer blood vessels than ranibizumab and pegaptanib groups (both P<0.05). However, there was no significant difference between the ranibizumab and pegaptanib groups regarding percentage of neovascularized corneal areas and number of blood vessels (both P>0.05).

CONCLUSION

Subconjunctival bevacizumab, ranibizumab, and pegaptanib sodium were effective with no corneal epitheliopathy for inhibiting corneal neovascularization after corneal burn in rats. Bevacizumab was more effective than ranibizumab and pegaptanib sodium.

The rationale of targeting mammalian target of rapamycin for ischemic stroke

Given the current limitation of therapeutic approach for ischemic stroke, a leading cause of disability and mortality in the developed countries, to develop new therapeutic strategies for this devastating disease is urgently necessary. As a serine/threonine kinase, mammalian target of rapamycin (mTOR) activation can mediate broad biological activities that include protein synthesis, cytoskeleton organization, and cell survival. mTOR functions through mTORC1 and mTORC2 complexes and their multiple downstream substrates, such as eukaryotic initiation factor 4E-binding protein 1, p70 ribosomal S6 kinase, sterol regulatory element-binding protein 1, hypoxia inducible factor-1, and signal transducer and activator transcription 3, Yin Ying 1, Akt, protein kinase c-alpha, Rho GTPase, serum-and gucocorticoid-induced protein kinase 1, etc. Specially, the role of mTOR in the central nervous system has been attracting considerable attention. Based on the ability of mTOR to prevent neuronal apoptosis, inhibit autophagic cell death, promote neurogenesis, and improve angiogenesis, mTOR may acquire the capability of limiting the ischemic neuronal death and promoting the neurological recovery. Consequently, to regulate the activity of mTOR holds a potential as a novel therapeutic strategy for ischemic stroke.

Effect of glucocorticoid (triamcinolone acetonide) pretreatment in a murine penetrating keratoplasty and suture model

PURPOSE

To evaluate the effect of glucocorticoid (triamcinolone acetonide injectable suspension) pretreatment on corneal neovascularization, lymphangiogenesis, and inflammation in a murine penetrating keratoplasty (PK) and corneal suture model.

METHODS

For the PK model, BALB/c mice were used as recipients and C57BL/6 mice were used as donors. A group pretreated with subconjunctival glucocorticoid and a combination of post-subconjunctival and topical glucocorticoids (group I) was compared with two groups that did not receive glucocorticoid pretreatment [one group received a combination of subconjunctival and topical glucocorticoids postoperatively (group II) and the other group received only topical glucocorticoid treatment postoperatively (group III)]. All groups were treated with subconjunctival glucocorticoid on the day of surgery. For the corneal suture model, BALB/c mice were used. A group receiving only pre-suture glucocorticoid treatment (group A) and a group receiving only post-suture glucocorticoid treatment (group C) were compared with a control group that did not receive glucocorticoid therapy (group B). The degree of neovascularization, lymphangiogenesis, and inflammatory infiltration was compared in each of these models.

RESULTS

In the PK model, the group receiving glucocorticoid pretreatment (group I) showed less neovascularization compared with the posttreatment-only groups (group II, P=0.043; group III, P=0.020) and less lymphangiogenesis compared with group III (P=0.005). In the corneal suture model, the glucocorticoid pretreatment group showed a similar level of neovascularization, lymphangiogenesis, and inflammatory infiltration as the posttreatment-only groups (P>0.05).

CONCLUSIONS

Glucocorticoid pretreatment before PK decreases neovascularization and lymphangiogenesis compared with posttransplant glucocorticoid treatment alone.

Nanotechnology in corneal neovascularization therapy--a review

Nanotechnology is an up-and-coming branch of science that studies and designs materials with at least one dimension sized from 1-100 nm. These nanomaterials have unique functions at the cellular, atomic, and molecular levels. The term "nanotechnology" was first coined in 1974. Since then, it has evolved dramatically and now consists of distinct and independent scientific fields. Nanotechnology is a highly studied topic of interest, as nanoparticles can be applied to various fields ranging from medicine and pharmacology, to chemistry and agriculture, to environmental science and consumer goods. The rapidly evolving field of nanomedicine incorporates nanotechnology with medical applications, seeking to give rise to new diagnostic means, treatments, and tools. Over the past two decades, numerous studies that underscore the successful fusion of nanotechnology with novel medical applications have emerged. This has given rise to promising new therapies for a variety of diseases, especially cancer. It is becoming abundantly clear that nanotechnology has found a place in the medical field by providing new and more efficient ways to deliver treatment. Ophthalmology can also stand to benefit significantly from the advances in nanotechnology research. As it relates to the eye, research in the nanomedicine field has been particularly focused on developing various treatments to prevent and/or reduce corneal neovascularization among other ophthalmologic disorders. This review article aims to provide an overview of corneal neovascularization, currently available treatments, and where nanotechnology comes into play.

Lack of association between VAP-1/SSAO activity and corneal neovascularization in a rabbit model

The aim of this study is to determine the efficacy of a potent and specific vascular adhesive protein-1/semicarbazide-sensitive amine oxidase (VAP-1/SSAO) inhibitor, LJP 1207, as a potential antiangiogenic and anti-inflammatory agent in the therapy of corneal neovascularization. Corneal neovascularization was induced with intrastromal suturing in rabbits (n = 20). Topical treatment with VAP-1/SSAO inhibitor LJP 1207 (n = 5, 4 times a day), bevacizumab (n = 5, daily), their combination (n = 5) and vehicle only (n = 5, 4 times a day) were applied postoperatively for 2 weeks. The development and extent of corneal neovascularization were evaluated by digital image analysis. At the end of the observation period, the level of corneal and serum VAP-1/SSAO activity was measured fluorometrically and radiochemically. The corneal VAP-1/SSAO activity was significantly elevated in the suture-challenged vehicle-treated group (3,075 ± 1,009 pmol/mg/h) as compared to unoperated controls (464.2 ± 135 pmol/mg/h, p < 0.001). Treatment with LJP 1207 resulted in slower early phase neovascularization compared to vehicle-treated animals (not significant). At days 7-14, there was no significant difference in the extent of corneal neovascularization between inhibitor- and vehicle-treated corneas, even though inhibitor treatment caused a normalization of corneal VAP-1/SSAO activity (885 ± 452 pmol/mg/h). Our results demonstrate that the significant elevation of VAP-1/SSAO activity due to corneal injury can be prevented with VAP-1/SSAO inhibitor LJP 1207 treatment. However, normalization of VAP-1/SSAO activity in this model does not prevent the development of corneal neovascularization.