Comparative study of tacrolimus and bevacizumab on corneal neovascularization in rabbits

Available Therapeutic Options for Corneal Neovascularization: A Review

Corneal neovascularization can impair vision and result in a poor quality of life. The pathogenesis involves a complex interplay of angiogenic factors, notably vascular endothelial growth factor (VEGF). This review provides a comprehensive overview of potential therapies for corneal neovascularization, covering tissue inhibitors of metalloproteinases (TIMPs), transforming growth factor beta (TGF-β) inhibitors, interleukin-1L receptor antagonist (IL-1 Ra), nitric oxide synthase (NOS) isoforms, galectin-3 inhibitors, retinal pigment epithelium-derived factor (PEDF), platelet-derived growth factor (PDGF) receptor inhibitors, and surgical treatments. Conventional treatments include anti-VEGF therapy and laser interventions, while emerging therapies such as immunosuppressive drugs (cyclosporine and rapamycin) have been explored. Losartan and decorin are potential antifibrotic agents that mitigate TGF-β-induced fibrosis. Ocular nanosystems are innovative drug-delivery platforms that facilitate the targeted release of therapeutic agents. Gene therapies, such as small interfering RNA and antisense oligonucleotides, are promising approaches for selectively inhibiting angiogenesis-related gene expression. Aganirsen is efficacious in reducing the corneal neovascularization area without significant adverse effects. These multifaceted approaches underscore the corneal neovascularization management complexity and highlight ideas for enhancing therapeutic outcomes. Furthermore, the importance of combination therapies and the need for further research to develop specific inhibitors while considering their therapeutic efficacy and potential adverse effects are discussed.

Up-to-date molecular medicine strategies for management of ocular surface neovascularization

Ocular surface neovascularization and its resulting pathological changes significantly alter corneal refraction and obstruct the light path to the retina, and hence is a major cause of vision loss. Various factors such as infection, irritation, trauma, dry eye, and ocular surface surgery trigger neovascularization via angiogenesis and lymphangiogenesis dependent on VEGF-related and alternative mechanisms. Recent advances in antiangiogenic drugs, nanotechnology, gene therapy, surgical equipment and techniques, animal models, and drug delivery strategies have provided a range of novel therapeutic options for the treatment of ocular surface neovascularization. In this review article, we comprehensively discuss the etiology and mechanisms of corneal neovascularization and other types of ocular surface neovascularization, as well as emerging animal models and drug delivery strategies that facilitate its management.

[Methods of diagnosis and treatment of corneal neovascularization]

Corneal neovascularization is one of the most common causes of decreased visual acuity and disability for vision loss, increase in the risk of corneal graft rejection, and appearance of opacifications on the cornea. This article reviews literature on etiological factors of the development of corneal neovascularization, as well as modern methods of diagnosis, conservative and surgical treatment of this pathology.

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.

Inhibition of Neovascularization and Inflammation in a Mouse Model of Corneal Alkali Burns Using Cationic Liposomal Tacrolimus

Eye drops account for more than 90% of commercialized ophthalmic drugs. However, eye drops have certain shortcomings, such as short precorneal retention time and weak corneal penetration. The requirement of frequent instillation of eye drops also causes poor patient compliance, which may lead to further aggravation of the disease. We aimed to develop a cationic liposome formulation to increase the bioavailability of the therapeutic agent and solve the aforementioned problems. In the present study, we prepared cationic liposomal tacrolimus (FK506) with a surface potential of approximately +30 mV, which could bind to the negatively charged mucin layer of the ocular surface. Our results showed that the content of FK506 in the cornea was increased by 93.77, 120.30, 14.24, and 20.36 times at 5, 30, 60, and 90 min, respectively, in the FK506 liposome group (0.2 mg/ml) compared with the free drug group (0.2 mg/ml). Moreover, FITC-labeled FK506 liposomes significantly prolonged the ocular surface retention time to 50 min after a single dose. In addition, the results of the Cell Counting Kit-8 assay, live and dead cell assay, sodium fluorescein staining, and hematoxylin and eosin staining all indicated that FK506 liposomes had good biological compatibility in both human corneal epithelial cells and mouse eyeballs. Compared with the free drug at the same concentration, FK506 liposomes effectively inhibited vascular endothelial growth factor-induced green fluorescent protein-transduced human umbilical vein endothelial cell migration and tube formation in vitro. In a mouse corneal neovascularization model induced by alkali burns, FK506 liposomes (0.2 mg/ml) enhanced corneal epithelial recovery, inhibited corneal neovascularization, and reduced corneal inflammation, and its therapeutic effect was better than those of the commercial FK506 eye drops (1 mg/ml) and the free drug (0.2 mg/ml). Collectively, these results indicate that cationic FK506 liposomes could increase the efficacy of FK506 in the corneal neovascularization model. Therefore, cationic FK506 liposomes can be considered as a promising ocular drug delivery system.

Anti-VEGF Treatment in Corneal Diseases

BACKGROUND

Corneal neovascularization (CN) is a clue feature of different ocular pathological conditions and can lead to corneal edema and opacification with subsequent vision loss. Vascular endothelial growth factor (VEGF), which plays a key role in new vessels formation, proliferation and migration, was found to be up-regulated in these conditions. Nowadays, it is possible to downregulate the angiogenic process by using anti-VEGF agents administered by different routes.

OBJECTIVE

To evaluate the efficacy, safety and possible future directions of anti-VEGF agents used for the treatment of CNV owing to different aetiologies.

METHODS

A computerized search of articles dealing with the topic of anti-VEGF therapy in CN was conducted in PubMed, Scopus and Medline electronic databases. The following key phrases were used: anti-VEGF agents, corneal neovascularization, bevacizumab, ranibizumab, vascular endothelial growth factor, angiogenesis.

RESULTS

The use of anti-VEGF therapy in the treatment of CN reduced pathological vessel density without causing significant side effects. Various administration routes such as topical, subconjunctival and intrastromal ones are available, and the choice depends on patient and disease characteristics. Much more effectiveness is achieved in case of early administration before mature and wellestablished vessels take place. A combined approach between various drugs including anti-VEGF agents should be adopted in those cases at higher risk of neovascularization recurrence such as chronic long-standing diseases where ischemic and inflammatory stimuli are not definitively reversed.

CONCLUSION

The efficacy and safety of anti-VEGF agents support their adoption into the daily clinical practice for the management of CN.

Pharmacological Potential of Small Molecules for Treating Corneal Neovascularization

Under healthy conditions, the cornea is an avascular structure which allows for transparency and optimal visual acuity. Its avascular nature is maintained by a balance of proangiogenic and antiangiogenic factors. An imbalance of these factors can result in abnormal blood vessel proliferation into the cornea. This corneal neovascularization (CoNV) can stem from a variety of insults including hypoxia and ocular surface inflammation caused by trauma, infection, chemical burns, and immunological diseases. CoNV threatens corneal transparency, resulting in permanent vision loss. Mainstay treatments of CoNV have partial efficacy and associated side effects, revealing the need for novel treatments. Numerous natural products and synthetic small molecules have shown potential in preclinical studies in vivo as antiangiogenic therapies for CoNV. Such small molecules include synthetic inhibitors of the vascular endothelial growth factor (VEGF) receptor and other tyrosine kinases, plus repurposed antimicrobials, as well as natural source-derived flavonoid and non-flavonoid phytochemicals, immunosuppressants, vitamins, and histone deacetylase inhibitors. They induce antiangiogenic and anti-inflammatory effects through inhibition of VEGF, NF-κB, and other growth factor receptor pathways. Here, we review the potential of small molecules, both synthetics and natural products, targeting these and other molecular mechanisms, as antiangiogenic agents in the treatment of CoNV.

Topical Tacrolimus as an adjunct to Conventional Therapy for Stromal Herpetic Keratitis: a Randomized Clinical Trial

Purpose

This study investigates the effects of 0.05% topical tacrolimus as an adjunct therapy for patients with non-necrotizing herpetic stromal keratitis (HSK).

Methods

Patients with non-necrotizing HSK, referred to the Cornea Clinic at Hospital in Rasht, Iran, between September 2016 and February 2018, were randomly assigned to two groups. The case group (N = 25) and the control group (N = 25) received conventional treatment with systemic acyclovir and topical prednisolone. The case group (N = 25) additionally received 0.05% tacrolimus eye drops four times a day for one month. Complete ocular examinations, including best-corrected visual acuity (BCVA) assessment, intraocular pressure (IOP) measurement, slit lamp biomicroscopy, and photo slit lamp imaging, were performed before treatment, and 3, 7, 14, 21, and 28 days after the intervention.

Results

The mean age of the patients was 46.2 ± 12.9 years, and 70% of the patients were male. There was no difference between the groups in terms of age, sex, and baseline ocular measurements (P> 0.05). The case group had a lower mean logarithm of the minimum angle of resolution (LogMAR) for BCVA, lower grading scores, and steeper decreasing trends for corneal haziness, edema, neovascularization, and epitheliopathy compared to the control group after the second week (P< 0.05), while IOP remained unchanged between groups (P> 0.05).

Conclusion

The addition of 0.05% topical tacrolimus enhances visual acuity and reduces corneal inflammation, neovascularization, and scarring; thus, it can used as an appropriate adjunct treatment for patients with HSK.

Micelle-solubilized axitinib for ocular administration in anti-neovascularization

The development of new blood vessels is directly related to the occurrence of eye diseases. Anti-angiogenic drugs can theoretically be extended to the treatment of ophthalmic diseases. In this study, axitinib, a class of tyrosine kinase inhibitors, was loaded via the amphiphilic copolymer MPEG-PCL, improving its dispersibility in water. Axitinib-loaded micelles showed low toxicity in concentration gradient assays. Additionally, multiple doses by scratch assay confirmed that axitinib had no significant effect on normal cell migration, and biosafety test results showed good cell compatibility. After we established the corneal neovascularization model after an alkali burn in rats, the anti-angiogenic efficacy was tested, with dexamethasone as a positive control. The results showed that axitinib-loaded micelles had anti-angiogenic effects without obvious tissue toxicity. As a class of targeted tyrosine kinase inhibitors, axitinib can be used in the treatment of ocular neovascular diseases through nanocrystallization.

Tetramethylpyrazine (TMP) ameliorates corneal neovascularization via regulating cell infiltration into cornea after alkali burn

In the present study, we investigated the underlying mechanism of tetramethylpyrazine (TMP)-medicated inhibition of corneal neovascularization (CNV). Our data showed that TMP could effectively downregulate the expression levels of CXCR4 mRNA and protein, as well as inhibit HUVECs, endothelial cells, tubule formation in vitro. In vivo, alkali burn (1 M NaOH) could remarkably upregulate CXCR4 expression and increase the migration of TNF-α-positive cells to corneal stroma. TMP drops could significantly downregulate CXCR4 expression in cornea, compared to the control. However, there was no difference in the downregulation of CXCR4 between TMP and FK506, an immunosuppressive drug. Moreover, the immunofluorescent staining of CD45 showed TMP and FK506 could significantly restrain the bone marrow (BM)-derived infiltration while the F4/80 staining reflects the suppression of macrophage aggregation. Meanwhile TMP could regulate the Interleukin 10 (IL-10) and FK506 could restrain the Interleukin 2 (IL-2). Furthermore, TMP and FK506 significantly ameliorate corneal opacity and neovascularization. Clinical assessment detected an obvious improvement in TMP and FK506 treatment groups, compared to controls in vivo. Thus, TMP had similar effects in inhibition of immune response and CNV by suppressing BM-infiltrating cells into cornea as FK506. TMP could be a potential agent in eye-drop therapy for cornea damaged by Alkali Burn.

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.

MicroRNA-296 mediated corneal neovascularization in an animal model of corneal burns after alkali exposures

Alkali burns of the cornea may lead to permanent visual impairment or complete blindness. In the current study, the role of microRNA 296 (miR-296) was explored in mouse corneal neovascularization induced by alkali burns. An alkali burn model in Balb/c mice was developed to study chemical corneal injuries. The expression of the miR-296 gene was measured by reverse-transcription-quantitative polymerase chain reaction. Fibroblast growth factor 23 (FGF23) protein expression was measured by western blot analysis. Possible impacted pathways were analyzed by Kyoto Encyclopedia of Genes and Genomes pathway analysis. miR-296 gene expression was examined following chemical corneal injury and it was demonstrated that different topical eye medications decreased miR-296 gene expression. miR-296 may participate in cytokine-cytokine receptor interaction pathways to influence corneal inflammatory responses. It was also revealed that FGF23 was expressed following chemical corneal injury and that different treatments with topical eye drops decreased its expression. miR-296 is a novel molecular modulator for alkali burns in the mouse cornea.

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.

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.

Tacrolimus downregulates inflammation by regulating pro‑/anti‑inflammatory responses in LPS‑induced keratitis

Lipopolysaccharide (LPS)-induced keratitis is a progressive infectious ocular disease in which innate inflammatory responses often cause clinical tissue damage and vision loss. The present study aimed to investigate the effects of tacrolimus, an effective immunomodulator, on LPS-induced innate immune responses. The effects of tacrolimus on the apoptotic rate and viability of human corneal epithelial cells (HCECs), polymorphonuclear neutrophils (PMNs) and monocytes (THP-1 cells) were examined using flow cytometry and MTT assays. Subsequently, the role of tacrolimus on LPS-induced inflammation in HCECs, PMNs and THP-1 cells was evaluated by detecting the expression levels of pro-inflammatory cytokines, including interleukin (IL)-1β, IL-6 and matrix metallopeptidase 9; anti-inflammatory cytokines, including IL-10 and transforming growth factor-β; and proangiogenic factors, including vascular endothelial growth factor and tumor necrosis factor-α using quantitative polymerase chain reaction. The results demonstrated that tacrolimus had good biocompatibility with HCECs, while promoting apoptosis and decreasing the viability of PMNs and THP-1 cells. Furthermore, tacrolimus effectively reduced the expression levels of pro-inflammatory cytokines and increased anti-inflammatory cytokines in LPS-induced keratitis in vitro. Notably, tacrolimus decreased the levels of proangiogenic factors, which are highly increased following LPS stimulation. Conclusively, tacrolimus appears to be a safe and effective treatment to suppress neutrophil and monocyte activity, modulate the balance of pro-/anti-inflammatory cytokines, and reduce the inflammatory response and angiogenic activity in LPS-induced bacterial keratitis.

Synthetic stigmasterol derivatives inhibit capillary tube formation, herpetic corneal neovascularization and tumor induced angiogenesis: Antiangiogenic stigmasterol derivatives

Angiogenesis plays a critical role in initiating and promoting several diseases, such as cancer and herpetic stromal keratitis (HSK). Herein, we studied the inhibitory effect of two synthetic stigmasterol derivatives on capillary tube-like structures and on cell migration in human umbilical vein endothelial cells (HUVEC): (22S,23S)-22,23-dihydroxystigmast-4-en-3-one (compound 1) and (22S,23S)-3β-bromo-5α,22,23-trihydroxystigmastan-6-one (compound 2). We also studied their effect on VEGF expression in IL-6 stimulated macrophages and in LMM3 breast cancer cells. Furthermore, we investigated the antiangiogenic activity of the compounds on corneal neovascularization in the murine model of HSK and in an experimental model of tumor-induced angiogenesis in mice. Both compounds inhibited capillary tube-like formation, but only compound 1 restrained cell migration. Compound 1, unlike compound 2, was able to reduce VEGF expression. Only compound 1 not only reduced the incidence and severity of corneal neovascularization, when administered at the onset of HSK, but it also restrained the development of neovascular response induced by tumor cells in mice skin. Our results show that compound 1 inhibits angiogenesis in vitro and in vivo. Therefore, compound 1 would be a promising drug in the treatment of those diseases where angiogenesis represents one of the main pathogenic events.