Recent drug therapies for corneal neovascularization

High-efficiency antioxidant ROS-responsive thermosensitive hydrogel encapsulated Fenofibrate for the treatment of corneal neovascularization

Corneal neovascularization (CNV) has become one of the common blinding ocular diseases recognized worldwide, affecting millions of people every year. Numerous studies have shown that oxidative stress and inflammation are important factors for the occurrence and development of CNV. In the present study, we established an antioxidant and reactive oxygen species (ROS) responsive thermosensitive hydrogel for long-acting drug delivery, combining with the loaded anti-angiogenic drug to the therapy for CNV. Se-PEG-PPG (SePEP) could in-situ gelling on the ocular surface temperature and cover the ocular surface. The hydrophobic interaction between the selenium ether segment and ocular mucin will further increase its adhesion on the ocular surface, which is conducive to drug Fenofibrate (Feno) retention and sustained release on the ocular surface. SePEP also played a role in reducing intracellular oxidative stress and oxidative responsive sustained release drug due to its selenium ether groups that scavenge ROS. Finally, the combined anti-oxidation, anti-inflammation, and anti-angiogenesis therapeutic effect of Feno@Se-PEG-PPG (SePEP-Feno) eye drops were demonstrated in a corneal neovascularization animal model. In conclusion, the multifunctional delivery system provided a promising method for the treatment of CNV and various ROS-related ocular diseases.

Delivery of Itgb1-siRNA by triptolide-modified and anti-Flt1 peptide-guided ionizable cationic LNPs for targeted therapy of corneal neovascularization

Corneal neovascularization (CoNV) is a leading cause of visual impairment worldwide. However, CoNV remains challenging to cure clinically because of the limitations of current drugs. New and more effective therapeutic formulations for CoNV treatment are therefore urgently needed. Antisense oligonucleotide drugs hold great promise for the treatment of neovascular diseases, and ionizable cationic lipid nanoparticles (icLNPs) have shown excellent performance for nucleic acid delivery, with high encapsulation, good cellular uptake, and effective endosomal escape. In the present study, we identified integrin β1 (Itgb1) as a key gene involved in angiogenesis and revealed the significant upregulation of Flt1 in vascular endothelial cells and pericytes in CoNV using single-cell sequencing. Itgb1 knockdown significantly inhibited the proliferation and migration of vascular endothelial cells and CoNV in mice. Based on these findings, we developed Itgb1-small interfering RNA (siRNA)-loaded icLNPs, and conjugated anti-Flt1 peptide to their surface to improve CoNV targeting. Furthermore, because lipid nanoparticles reportedly trigger immune responses by upregulating pro-inflammatory cytokine expression, which may promote neovascularization, we modified triptolide (a compound with anti-inflammatory properties) into the icLNPs. The triptolide-modified, anti-Flt1 peptide-conjugated, and Itgb1-siRNA-loaded icLNPs (Itgb1-siRNA@TPL) effectively inhibited the proliferation and migration of vascular endothelial cells in vitro and CoNV in mice after eye drop administration. These effects occurred via downregulation of the PI3K/AKT and NF-κB signaling pathways. Finally, the biosafety of Itgb1-siRNA@TPL was tested, and the results revealed that it was not toxic to the cornea or major organs and had no impact on corneal epithelial healing. In conclusion, Itgb1-siRNA@TPL represent a novel, noninvasive, and effective approach for the treatment of CoNV.

Glucocorticoid Receptor Signaling Is Critical for Mouse Corneal Development, Inhibition of Inflammatory Response, and Neovascularization of the Cornea

The cornea protects the interior of the eye from external agents such as bacteria, viruses, and debris. Synthetic glucocorticoids are widely prescribed in the treatment of ocular infections and disorders. The actions of glucocorticoids are mediated by the glucocorticoid receptor (GR); however, the molecular and physiological functions of GR signaling in the cornea are poorly understood. This study found that treatment of mice with glucocorticoid eye drops led to a profound regulation of the corneal transcriptome. These glucocorticoid-regulated genes were associated with multiple biological functions, including the immune response. To understand the direct role of GR signaling in the cornea, mice with conditional knockout of GRs in the corneal epithelium were generated. Mice lacking corneal GRs exhibited microphthalmia, loss of pupils, a deformed and opaque lens, and mislocalization of key structural proteins within the corneal epithelial layers. Global transcriptomic approaches revealed that loss of GR signaling in the cornea also resulted in the dysregulation of a large cohort of genes strongly associated with an enhanced inflammatory response. Finally, corneal GR signaling was required for preventing neovascularization of blood and lymphatic vessels and thereby immune cell infiltration of the cornea. These results reveal that corneal GR signaling plays a critical role in ocular development and in maintaining the homeostasis of the eye.

A Synergistic Therapy With Antioxidant and Anti-VEGF: Toward its Safe and Effective Elimination for Corneal Neovascularization

Corneal neovascularization (CNV) is one of the leading causes of blindness in the world. In clinical practice; however, it remains a challenge to achieve a noninvasive and safe treatment. Herein, a biocompatible shell with excellent antioxidant and antivascularity is prepared by co-assembly of epigallocatechin gallate/gallic acid and Cu (II). After loading glucose oxidase (GOx) inside, the shell is modified with dimeric DPA-Zn for codelivering vascular endothelial growth factor (VEGF) small interfering RNA (VEGF-siRNA). Meanwhile, the Arg-Gly-Asp peptide (RGD) peptide-engineered cell membranes coating improves angiogenesis-targeting and is biocompatible for the multifunctional nanomedicine (CEGs/RGD). After eye drops administration, CEGs/RGD targets enrichment in neovascularization and CEGs NPs enter cells. Then, the inner GOx consumes glucose with a decrease in local pH, which in turn leads to the release of EGCE and VEGF-siRNA. As a result, the nanomedicines significantly reduce angiogenesis and inhibit CNV formation through synergistic effect of antioxidant and antivascular via down-regulation of cluster of differentiation 31 and VEGF. The nanomedicine represents a safe and efficient CNV treatment through the combined effect of antioxidant/gene, which provides important theoretical and clinical significance.

Animal Models in Eye Research: Focus on Corneal Pathologies

The eye is a complex sensory organ that enables visual perception of the world. The dysfunction of any of these tissues can impair vision. Conduction studies on laboratory animals are essential to ensure the safety of therapeutic products directly applied or injected into the eye to treat ocular diseases before eventually proceeding to clinical trials. Among these tissues, the cornea has unique homeostatic and regenerative mechanisms for maintaining transparency and refraction of external light, which are essential for vision. However, being the outermost tissue of the eye and directly exposed to the external environment, the cornea is particularly susceptible to injury and diseases. This review highlights the evidence for selecting appropriate animals to better understand and treat corneal diseases, which rank as the fifth leading cause of blindness worldwide. The development of reliable and human-relevant animal models is, therefore, a valuable research tool for understanding and translating fundamental mechanistic findings, as well as for assessing therapeutic potential in humans. First, this review emphasizes the unique characteristics of animal models used in ocular research. Subsequently, it discusses current animal models associated with human corneal pathologies, their utility in understanding ocular disease mechanisms, and their role as translational models for patients.

Preparation of a Sunitinib loaded microemulsion for ocular delivery and evaluation for the treatment of corneal neovascularization in vitro and in vivo

Background: Corneal neovascularization (CNV) is a pathological condition that can disrupt corneal transparency, thus harming visual acuity. However, there is no effective drug to treat CNV. Sunitinib (STB), a small-molecule multiple receptor tyrosine kinase inhibitor, was shown to have an effect on CNV. The purpose of this study was to develop an STB microemulsion (STB-ME) eye drop to inhibit CNV by topical application. Methods: We successfully prepared an STB-ME by the phase inversion emulsification method, and the physicochemical properties of STB-MEs were investigated. The short-term storage stability, cytotoxicity to human corneal epithelial cells, drug release, ocular irritation, ocular pharmacokinetics and the inhibitory effect on CNV were evaluated in vitro and in vivo. Results: The optimal formulation of STB-ME is composed of oleic acid, CRH 40, Transcutol P, water and sodium hyaluronate (SH). It is a uniform spherical particle with a mean droplet size of 18.74 ± 0.09 nm and a polydispersity index of 0.196 ± 0.004. In the in vitro drug release results, STB-ME showed sustained release and was best fitted by a Korsmeyer-Peppas model (R ² = 0.9960). The results of the ocular pharmacokinetics in rabbits showed that the formulation containing SH increased the bioavailability in the cornea (2.47-fold) and conjunctiva (2.14-fold). STB-ME (0.05% and 0.1%), administered topically, suppressed alkali burn-induced CNV in mice more effectively than saline, and high-dose (0.1%) STB-ME had similar efficacy to dexamethasone (0.025%). Conclusion: This study provides a promising formulation of STB-ME for the inhibition of CNV by topical administration, which has the excellent characteristics of effectiveness, sustained release and high ocular bioavailability.

An Update on Novel Ocular Nanosystems with Possible Benefits in the Treatment of Corneal Neovascularization

Corneal neovascularization (CNV) is an ocular pathological change that results from an imbalance between angiogenic factors and antiangiogenic factors as a result of various ocular insults, including infection, inflammation, hypoxia, trauma, corneal degeneration, and corneal transplantation. Current clinical strategies for the treatment of CNV include pharmacological treatment and surgical intervention. Despite some degree of success, the current treatment strategies are restricted by limited efficacy, adverse effects, and a short duration of action. Recently, gene-based antiangiogenic therapy has become an emerging strategy that has attracted considerable interest. However, potential complications with the use of viral vectors, such as potential genotoxicity resulting from long-term expression and nonspecific targeting, cannot be ignored. The use of ocular nanosystems (ONS) based on nanotechnology has emerged as a great advantage in ocular disease treatment during the last two decades. The potential functions of ONS range from nanocarriers, which deliver drugs and genes to target sites in the eye, to therapeutic agents themselves. Various preclinical studies conducted to date have demonstrated promising results of the use of ONS in the treatment of CNV. In this review, we provide an overview of CNV and its current therapeutic strategies and summarize the properties and applications of various ONS related to the treatment of CNV reported to date. Our goal is to provide a comprehensive review of these considerable advances in ONS in the field of CNV therapy over the past two decades to fill the gaps in previous related reports. Finally, we discuss existing challenges and future perspectives of the use of ONS in CNV therapy, with the goal of providing a theoretical contribution to facilitate future practical growth in the area.

Combined delivery of small molecule and protein drugs as synergistic therapeutics for treating corneal neovascularization by a one-pot coassembly strategy

Combined drug administration is a potential strategy to increase efficacy through therapeutic synergy. Small molecule drugs and protein drugs are the two most popular kinds of drugs in medicine. However, efficiently encapsulating these two drugs still have key challenges due to their distinct properties (molecular weight, hydrophilicity, chemical groups, etc.), weak ability to penetrate through various biobarriers (cell membrane, endosome escape, tissue barriers dependent on the method of administration, etc.) and the easy deactivation of protein drugs during the construction of carrier and delivery process. Here, we utilize the hexahistidine-metal assembly (HmA), which can encapsulate a wide spectrum of drugs with high loading efficiency, to coencapsulate Dexp (a small molecule drug) and BVZ (protein drug) by a one-pot coassembly strategy. Our data demonstrated that Dexp and BVZ were coloaded into Dexp&BVZ@HmA with high efficiency, while the bioactivity of BVZ was well-maintained. Most importantly, when evaluating the therapeutic outcomes of drugs@HmA in a corneal neovascularization (CNV) model in vitro and in vivo, the combination group presented overwhelming efficacy compared to the monotherapy group. This strategy offers a platform to codeliver protein and small drugs and has the potential for treating anterior segment diseases as well as other diseases that need combination therapy.

Reactive Oxygen Species─Responsive Lipid Nanoparticles for Effective RNAi and Corneal Neovascularization Therapy

Corneal neovascularization (CNV) is a common disease that affects the vision ability of more than 1 million people annually. Small interfering RNA (siRNA) delivery nanoparticle platforms are a promising therapeutic modality for CNV treatment. However, the efficient delivery of siRNA into cells and the effective release of siRNA from delivery vehicles in a particular cell type challenge effective RNAi clinical application for CNV suppression. This study reports the design of a novel reactive oxygen species (ROS)-responsive lipid nanoparticle for siRNA delivery into corneal lesions for enhanced RNAi as a potential CNV treatment. We demonstrated that lipid nanoparticles could efficiently deliver siRNA into human umbilical vein endothelial cells and release siRNA for enhanced gene silencing by using the upregulated ROS of CNV to promote lipid nanoparticle degradation. Moreover, the subconjunctival injection of siRNA nanocomplexes into corneal lesions effectively knocked down vascular endothelial growth factor expression and suppressed CNV formation in an alkali burn model. Thus, we believe that the strategy of using ROS-responsive lipid nanoparticles for enhanced RNAi in CNV could be further extended to a promising clinical therapeutic approach to attenuate CNV formation.

Inhibition of corneal neovascularization by topical application of nintedanib in rabbit models

AIM

To evaluate the potential efficacy and mechanisms of nintedanib in corneal neovascularization (NV) in rabbit models.

METHODS

Corneal NV was induced using 1 mol/L NaOH. Rabbits (n=21) were randomized to 3 groups: Group 1 were treated with 0.9% NaCl, Group 2 with Avastin (5 mg/mL), and Group 3 with nintedanib (1 mg/mL). All treatments started 1d after alkaline burns and were topically performed 3 times a day for 2wk. Photographs were taken on a slit lamp microscope on day 7 and 14. The NV area, the length of the vascularization and angiogenesis index (AI) were used to evaluate the corneal NV. On day 14, the immunohistochemical (IHC) studies of the cornea were examined. Western blot was performed to test the expression levels of vascular endothelial growth factor (VEGF), Akt, p-Akt, P38, p-P38, MMP-2 and MMP-9.

RESULTS

The corneal NV area, vessel length and AI in Group 3 were significantly lower than Group 2, with both being lower than Group 1. IHC staining showed that VEGF was significantly overexpressed in the epithelium and stroma of cornea following alkaline burns. In contrast, the level of VEGF was significantly suppressed in both Group 2 and Group 3. Western blot results further confirmed that, compared with Group 1, Group 3 had significantly reduced expressions of VEGF, Akt, p-Akt, p-P38, MMP-2, and MMP-9 in corneal tissues. Trends of lower levels of MMP-2, AKT, and p-AKT in Group 3 than Group 2 were identified.

CONCLUSION

Nintedanib and Avastin can effectively inhibit corneal NV, with P38 MAPK and AKT signaling pathways being possibly involved. Nintedanib seems more effective than Avastin and has the potential to be a novel therapy for preventing corneal NV.

Subconjunctival Injection of Regulatory T Cells Potentiates Corneal Healing Via Orchestrating Inflammation and Tissue Repair After Acute Alkali Burn

Purpose

This study aimed to investigate the therapeutic effects and underlying mechanisms of locally delivered regulatory T cells (Tregs) on acute corneal wound healing after alkali burn.

Methods

After corneal alkali burn, the mice were injected subconjunctivally with regulatory T cells (Tregs) isolated from syngeneic mice. The wound healing process was monitored by clinical manifestation, flow cytometry, and enzyme-linked immunosorbent assay (ELISA). As amphiregulin (Areg) was significantly upregulated, its reparative function in injured corneas was suggested. The hypothesis was further verified via loss- and gain-of-function experiments by administrating the antibody of Areg (anti-Areg) and recombinant Areg (rmAreg).

Results

Subconjunctivally injected Tregs rapidly migrated to injured corneas. The mice treated with Tregs showed prominently reduced corneal opacity, alleviated edema, and faster re-epithelialization compared with the control group. Mechanistically, Treg treatment led to suppressed infiltration of inflammatory cells, along with improved proliferation and inhibited apoptosis of corneal epithelial cells. Tregs expressed upregulated functional markers, including Areg. Expectantly, the levels of Areg in corneas were dramatically higher in the Treg injection group, in line with better corneal restoration. Additional experiments showed that the administration of anti-Areg blunted the reparative effect of Tregs, while exogenous Areg enhanced it. Treg-treated corneas also exhibited less neovascularization and fibrosis at a later reconstruction stage of corneal repair.

Conclusions

The findings showed that the subconjunctival injection of Tregs effectively promoted corneal wound healing by inhibiting excessive inflammation and enhancing epithelial regeneration, with an indispensable reparative role of Areg. Subsequent complications of corneal vascularization and fibrosis were therefore reduced.

The functional role of decorin in corneal neovascularization in vivo

Our earlier decorin (Dcn) gene overexpression studies found that the targeted Dcn gene transfer into the cornea inhibited corneal angiogenesis in vivo using a rabbit model. In this study, we tested the hypothesis that anti-angiogenic effects of decorin in the cornea are mediated by alterations in a normal physiologic balance of pro- and anti-angiogenic factors using decorin deficient (Dcn^-/-) and wild type (Dcn^+/+) mice. Corneal neovascularization (CNV) in Dcn^-/- and Dcn^+/+ mice was produced with a standard chemical injury technique. The clinical progression of CNV in mice was monitored with stereo- and slit-lamp microscopes, and histopathological hematoxylin and eosin (H&E) staining. Protein and mRNA expression of pro- and anti-angiogenic factors in the cornea were evaluated using immunofluorescence and quantitative real-time PCR, respectively. Slit-lamp clinical eye examinations revealed significantly more CNV in Dcn^-/- mice than the Dcn^+/+ mice post-injury (p < 0.05) and AAV5-Dcn gene therapy significantly reduced CNV in Dcn^-/- mice compered to no AAV5-Dcn gene therapy controls (p < 0.001). H&E-stained corneal sections exhibited morphology with several neovessels in injured corneas of the Dcn^-/- mice than the Dcn^+/+ mice. Immunofluorescence of corneal sections displayed significantly higher expression of α-smooth muscle actin (α-SMA) and endoglin proteins in Dcn^-/- mice than Dcn^+/+ mice (p < 0.05). Quantitative real-time PCR found significantly increased mRNA levels of pro-angiogenic factors endoglin (2.53-fold; p < 0.05), Vegf (2.47-fold; p < 0.05), and Pecam (2.14-fold; p < 0.05) and anti-angiogenic factor Vegfr2 (1.56-fold; p < 0.05) in the normal cornea of the Dcn^-/- mice than the Dcn^+/+ mice. Furthermore, neovascularized Dcn^-/- mice corneas showed greater increase in mRNA expression of pro-angiogenic factors endoglin (4.58-fold; p < 0.0001), Vegf (4.16-fold; p < 0.0001), and Pdgf (2.15-fold; p < 0.0001) and reduced expression of anti-angiogenic factors Ang2 (0.12-fold; p < 0.05), Timp1 (0.22-fold; p < 0.05), and Vegfr2 (0.67-fold; p > 0.05) compared to neovascularized Dcn^+/+ mice corneas. These gene deficience studies carried with transgenic Dcn^-/- mice revealed decorin's role in influencing a physiologic balance between pro-and anti-angiogenic factors in the normal and injured cornea. We infer that the functional deletion of Dcn promotes irregular corneal repair and aggravates CNV.

Gold nanoparticles to enhance ophthalmic imaging

The use of gold nanoparticles as diagnostic tools is burgeoning, especially in the cancer community with a focus on theranostic applications to both cancer diagnosis and treatment. Gold nanoparticles have also demonstrated great potential for use in diagnostic and therapeutic approaches in ophthalmology. Although many ophthalmic imaging modalities are available, there is still a considerable unmet need, in particular for ophthalmic molecular imaging for the early detection of eye disease before morphological changes are more grossly visible. An understanding of how gold nanoparticles are leveraged in other fields could inform new ways they could be utilized in ophthalmology. In this paper, we review current ophthalmic imaging techniques and then identify optical coherence tomography (OCT) and photoacoustic imaging (PAI) as the most promising technologies amenable to the use of gold nanoparticles for molecular imaging. Within this context, the development of gold nanoparticles as OCT and PAI contrast agents are reviewed, with the most recent developments described in detail.

Multimodal Photoacoustic Imaging-Guided Regression of Corneal Neovascularization: A Non-Invasive and Safe Strategy

Corneal neovascularization (CNV) is one of the main factors that induce blindness worldwide. However, current medical treatments cannot achieve non-invasive and safe inhibition of CNV. A noninvasive photoacoustic imaging (PAI)-guided method is purposed for the regression of CNV. PAI can monitor the oxygen saturation of cornea blood vessels through the endogenous contrast of hemoglobin and trace administrated drugs by themselves as exogenous contrast agents. An indocyanine green (ICG)-based nanocomposite (R-s-ICG) is prepared for CNV treatment via eye drops and subconjunctival injections. It is demonstrated that R-s-ICG can enrich corneal tissues and pathological blood vessels rapidly with minor residua in normal eyeball tissues. Anti-CNV treatment-driven changes in the blood vessels are assessed by real-time multimodal PAI in vivo, and then a safe laser irradiation strategy through the canthus is developed for phototherapy and gene therapy synergistic treatment. The treatment leads to the efficient inhibition of CNV with faint damages to normal tissues.

Suppression of pathological ocular neovascularization by a small molecule, SU1498

Selective inhibition of vascular endothelial growth factor receptor (VEGFR), particularly VEGFR-2, is an efficient method for the treatment of ocular neovascularization. SU1498 is a specific inhibitor of VEGFR-2. In this study, we investigated the role of SU1498 in ocular neovascularization. Administration of SU1498 did not show any cytotoxicity and tissue toxicity at the tested concentrations. Administration of SU1498 reduced the size and thickness of choroidal neovascularization and decreased the mean length and mean number of corneal neovascular vessels induced by alkali burn. Pretreatment of SU1498 significantly reduced the proliferation, migration, and tube formation ability of HUVECs. SU1498 played the anti-angiogenic role through the regulation of p38-MAPK signaling. Taken together, inhibition of VEGFR-2 by SU1498 provides a novel therapeutic approach for ocular neovascularization.

Regulation of matrix metalloproteinases 2 and 9 in corneal neovascularization

Corneal neovascularization (CNV), a pathological process of angiogenesis, can lead to serious consequences in the cornea. CNV is generally proved to associate with inflammation in the cornea closely, which is mainly elicited by the disruption of equilibrium between angiogenic and antiangiogenic factors. Angiogenic factors including vascular endothelial growth factors (VEGFs), basic fibroblast growth factors (bFGFs), and matrix metalloproteinases (MMPs) are vital factors in the formation of CNV. Especially VEGFs are convinced to be the core angiogenic factors in CNV, and MMPs are proved to exert dual effects on the process. Strikingly, matrix metalloproteinase 2 (MMP-2) and matrix metalloproteinase 9 (MMP-9) are determined to play key roles in the formation of CNV, while the mechanism is still vague. In this review, the latest researches are reviewed to discuss the role of MMP-2 and MMP-9 in CNV, respectively, and some inhibitors of them are presented. We hope to provide a new direction of drug research for CNV.

LncRNAs in ocular neovascularizations

The prevalence of eye diseases worldwide is dramatically increasing and represents a major concern in underdeveloped and developed regions. Ocular diseases, previously associated with a higher depression risk, also impose a substantial economic burden on affected families, thus early detection and/or accurate treatment in order to avoid and prevent blindness should be emphasized. Ocular neovascularization (NV), the leading cause of blindness in a variety of eye diseases, is a pathologic process characterized by the formation, proliferation and infiltration of anomalous, tiny and leaky fragile blood vessels within the eye. Genetics have been suspected to play an important role in the occurrence of eye diseases, with the detection of a numbers of specific gene mutations. Long non-coding RNA (lncRNAs) are novel class of regulatory molecules previously associated with various biological processes and diseases, however the nature of the relation and pathways by which they might contribute to the development of corneal, choroidal and retinal NV have not yet been completely elucidated. In this review, we focus on the regulation and characteristics of lncRNAs, summarize results from ocular NV-related studies and discuss the implication of lncRNAs in ocular NV development.

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.

Vascular Endothelial Growth Factor (VEGF) Induced Downstream Responses to Transient Receptor Potential Vanilloid 1 (TRPV1) and 3-Iodothyronamine (3-T1AM) in Human Corneal Keratocytes

This study was undertaken to determine if crosstalk among the transient receptor potential (TRP) melastatin 8 (TRPM8), TRP vanilloid 1 (TRPV1), and vascular endothelial growth factor (VEGF) receptor triad modulates VEGF-induced Ca²⁺ signaling in human corneal keratocytes. Using RT-PCR, qPCR and immunohistochemistry, we determined TRPV1 and TRPM8 gene and protein coexpression in a human corneal keratocyte cell line (HCK) and human corneal cross sections. Fluorescence Ca²⁺ imaging using both a photomultiplier and a single cell digital imaging system as well as planar patch-clamping measured relative intracellular Ca²⁺ levels and underlying whole-cell currents. The TRPV1 agonist capsaicin increased both intracellular Ca²⁺ levels and whole-cell currents, while the antagonist capsazepine (CPZ) inhibited them. VEGF-induced Ca²⁺ transients and rises in whole-cell currents were suppressed by CPZ, whereas a selective TRPM8 antagonist, AMTB, increased VEGF signaling. In contrast, an endogenous thyroid hormone-derived metabolite 3-Iodothyronamine (3-T₁AM) suppressed increases in the VEGF-induced current. The TRPM8 agonist menthol increased the currents, while AMTB suppressed this response. The VEGF-induced increases in Ca²⁺ influx and their underlying ionic currents stem from crosstalk between VEGFR and TRPV1, which can be impeded by 3-T₁AM-induced TRPM8 activation. Such suppression in turn blocks VEGF-induced TRPV1 activation. Therefore, crosstalk between TRPM8 and TRPV1 inhibits VEGFR-induced activation of TRPV1.