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

Preparation and in vivo and ex vivo studies of sirolimus nano-in-situ gel ophthalmic formulation

Sirolimus (SR) is a macrolide with antifungal and antitumor immunosuppressant properties, classified as a selective inhibitor of mammalian target of rapamycin (mTOR). In this study, an ionic in situ gel of SR (SR-SUS-ISG) was formulated using gellan gum, exhibiting stability regardless of temperature and pH variations, causing minimal irritation. Harnessing the physiological conditions of the eye, SR-SUS-ISG underwent gelation upon contact with ions, increasing drug viscosity and prolonging retention on the ocular surface. Concurrently, SR-SUS-ISG displayed favorable shear dilution properties, reducing viscosity at ambient temperature, enhancing fluidity, and facilitating convenient packaging and transport. Biocompatibility assessments on both human corneal epithelial cells and rabbit eyes demonstrated that SR-SUS-ISG could well be tolerated. Pharmacokinetic investigations in rabbit ocular aqueous humor revealed sustained release, improved corneal penetration, and enhanced bioavailability. Additionally, in a rat corneal alkali burn model, SR-SUS-ISG exhibited inhibitory effects on corneal neovascularization, associated with decreased levels of the inflammatory factors VEGF and MMPs. These findings suggested that SR-SUS-ISG held promise as an effective ocular drug delivery system.

Management of corneal neovascularization: Current and emerging therapeutic approaches

Corneal neovascularization (CoNV) is a sight-threatening condition affecting an estimated 1.4 million people per year, and the incidence is expected to rise. It is a complication of corneal pathological diseases such as infective keratitis, chemical burn, corneal limbal stem cell deficiency, mechanical trauma, and immunological rejection after keratoplasties. CoNV occurs due to a disequilibrium in proangiogenic and antiangiogenic mediators, involving a complex system of molecular interactions. Treatment of CoNV is challenging, and no therapy thus far has been curative. Anti-inflammatory agents such as corticosteroids are the mainstay of treatment due to their accessibility and well-studied safety profile. However, they have limited effectiveness and are unable to regress more mature neovascularization. With the advent of advanced imaging modalities and an expanding understanding of its pathogenesis, contemporary treatments targeting a wide array of molecular mechanisms and surgical options are gaining traction. This review aims to summarize evidence regarding conventional and emerging therapeutic options for CoNV.

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.

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.

Inhibiting corneal neovascularization by sustainably releasing anti-VEGF and anti-inflammation drugs from silica-thermogel nanohybrids

Corneal neovascularization (CNV) is one of the main factors that induce blindness worldwide. To effectively inhibit CNV, a novel nanohybrid has been developed by incorporating anti-VEGF bevacizumab (BEV)-loaded mesoporous silica nanoparticles (BEV@MSN) into the thermogel matrix with anti-inflammation cyclosporine A (CsA) (BEV@MSN-CsA@Thermogel). This nanohybrid regulates the in vitro release of both bevacizumab and cyclosporine A in a sustainable way for up to four weeks to enhance CNV inhibition through the synergistic anti-VEGF and anti-inflammation. The carrier materials (i.e. silica and thermogel) in this nanohybrid do not show any cytotoxicity to human Tenon's fibroblasts, corneal epithelial cells and corneal endothelial cells. BEV@MSN-CsA@Thermogel effectively prevents proliferation, migration, and tube-like structure formation of human umbilical vein endothelial cells. Moreover, subconjunctival injection of BEV@MSN-CsA@Thermogel significantly inhibits corneal neovascularization in terms of the CNV area, the new vessel length, the corneal opaque area, the corneal inflammation and abnormal fibrosis in a rabbit model. This nanohybrid is thus a promising alternative for effective CNV treatment.

Novel Parameters to Assess the Severity of Corneal Neovascularization Using Anterior Segment Optical Coherence Tomography Angiography

PURPOSE

Assessment of anterior segment-optical coherence tomography angiography (AS-OCTA) to determine severity of corneal neovascularization (CoNV).

DESIGN

Retrospective, cross-sectional, single-center study.

METHODS

Patients of various CoNV etiologies were selected and classified into mild, moderate, and severe. Their AS-OCTA images were measured for CoNV anterior limit, CoNV posterior limit, CoNV thickness, CoNV depth%, CoNV vessel density, CoNV area, and CoNV volume. Further, AS-OCTA parameters were correlated to clinical parameters, such as classification, a numerical severity scale, vascular clock hours, and best-corrected visual acuity (BCVA).

RESULTS

A total of 19 mild, 10 moderate, and 6 severe CoNV eyes were included with no significant age-gender differences. CoNV depth% and volume increased from mild to moderate (9.3 ± 1.1% to 17.7 ± 3.3%, P = .030, and 0.2 ± 0.1 mm³ to 1.0 ± 0.3 mm³, P = .025, respectively) and from moderate to severe CoNV (44.6 ± 5.3%, P < .001, and 2.0 ± 0.3 mm³, P = .014, respectively). CoNV area and posterior limit increased from mild to moderate (1.7 ± 0.3 mm² to 4.6 ± 0.7 mm², P = .001, and 217.7 ± 16.8 μm to 349.1 ± 54.9 μm, P = .048, respectively), not from moderate to severe (P = .999 and P = .403, respectively). CoNV thickness increased from moderate to severe (218.2 ± 46.6 μm to 340.2 ± 8.7 μm, P = .020), but not from mild to moderate. CoNV area and volume showed good correlations to CoNV staging (r = 0.703 and r = 0.771, respectively; P < .001) and severity scale (r = 0.794 and r = 0.712, respectively; P < .001). CoNV area showed good correlation to clock hours (r = 0.749, P < .001). CoNV depth and volume showed good correlation to BCVA (r = 0.744 and r = 0.722, respectively; P < .001). CoNV anterior limit and vessel density showed no significant correlations (P ≥ .05).

CONCLUSIONS

Severe CoNV shows greater CoNV posterior limit, thickness, depth%, area, and volume on AS-OCTA compared to mild. CoNV volume and depth strongly correlate to BCVA. AS-OCTA provides novel, quantitative, and noninvasive parameters for assessing CoNV severity.

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.

Investigation the effect of Hypericum perforatum on corneal alkali burns

Purpose: To investigate the effect of Hypericum perforatum on corneal alkali burn. Methods: We studied 45 250 g weighing, 4 months old Wistar albino rats. Alkaline burns were performed in the corneas of all experimental animals with 2 mol/L NaOH after general anaesthesia. Rats were divided into five groups according to the subsequent process applied to them: group 1 was the topical Hypericum perforatum group, group 2 was the topical pure olive oil group, group 3 was the oral Hypericum perforatum group, group 4 was the oral pure olive oil group, and group 5 was the control untreated group. Rats were sacrificed under general anaesthesia on the 14 day. The rate of corneal inflammation, neovascularization, fibroblastic activity, and cluster of differentiation 31 (CD31) staining was investigated. Result: There were 45 rats at the beginning of the study. One rat in groups 1, 2, and 3 died during the study; therefore, 42 rats could be evaluated. There were 8 rats in group 1, 8 rats in group 2, 8 rats in group 3, and 9 rats in group 4. We found less corneal neovascularization (CNV), inflammation, and fibroblastic activity in group 1 and group 2 than in the other groups (p ˂ 0.001 for all parameters). CNV, inflammation, fibroblastic activity, and CD31 staining rates were lower in group 1 than in group 2 (p ˂ 0.001 for all parameters). There was no difference between groups 3, 4, and 5 (respectively, p = 0.436, 0.634, and 0.750). Conclusions: We found that both topical Hypericum perforatum oily extract and olive oil have anti-inflammatory, anti-angiogenic, and anti-fibroblastic effects when applied after corneal alkali burns in rat corneas. Further studies should be conducted in this field.

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.

Effects of dexamethasone on C6 cell proliferation, migration and invasion through the upregulation of AQP1

Dexamethasone (Dex) is commonly used to treat glioma; however, the mechanism underlying the action of Dex remains unclear. In the present study, the hypothesis that aquaporin-1 (AQP1) may participate in tumor cell proliferation, apoptosis, migration and invasion was tested using small interfering RNA (siRNA). The results of the current study indicated that Dex could inhibit the proliferation, in addition to promoting the migration, of C6 cells. Dex was indicated to promote the expression of AQP1. Downregulation of AQP1, achieved using siRNAs, demonstrated the inhibition of cell proliferation, promotion of cell migration and suppression of invasion; therefore, Dex was indicated to serve a role in these effects in the C6 cells, via the upregulation of AQP1. This demonstrated that AQP1 could be utilized as a novel therapeutic target, with the aim of inhibiting the proliferation and metastasis of gliomas.

Effect of Histone Deacetylase Inhibitor, Butyroyloxymethyl-Diethyl Phosphate (AN-7), on Corneal Neovascularization in a Mouse Model

PURPOSE

To examine whether butyroyloxymethyl-diethyl phosphate (AN-7), a histone deacetylase inhibitor, inhibits chemically induced corneal neovascularization (NV) in mice.

METHODS

Corneal NV was induced in the right eye of male C57BL mice by application of a mixture of 75% silver nitrate and 25% potassium nitrate to the corneal center. Immediately thereafter, the mice were randomized into 2 groups, receiving an intraperitoneal injection of AN-7 or saline, which served as control. Corneal NV was evaluated at constant time intervals from the corneal injury by corneal photographs and the area of corneal NV was measured. Centricity and density of the corneal vascularization were graded. Corneal flat mounts blood vessels staining and histological studies were performed on day 10. Unpaired t-test was used for group comparisons.

RESULTS

The corneal neovascular area was statistically significantly reduced by AN-7 treatment on days 10 and 14 postinjury and compared with the untreated group. The centricity and density of the corneal NV between treated and untreated groups showed no significant difference at any time point.

CONCLUSIONS

Systemic treatment with AN-7 had a significant inhibitory effect on chemical burn-induced corneal NV in mice. These results suggest that AN-7 should be further evaluated for its therapeutic potential for the treatment of corneal NV.

Attenuation of corneal neovascularization by topical low-molecular-weight heparin-taurocholate 7 without bleeding complication

AIM

To investigate the antiangiogenic effects and safety of topically administered low-molecular-weight heparin-taurocholate 7 (LHT7) on corneal neovascularization (CoNV).

METHODS

Twenty-four Sprague-Dawley rats were randomly distributed into four groups of six rats each. The central corneas were cauterized using a silver/potassium nitrate solution. From 2d after cauterization, 12.5 mg/mL (low LHT7 group) or 25 mg/mL (high LHT7 group) LHT7 was topically administered three times daily; 12.5 mg/mL bevacizumab was topically administered as positive control (bevacizumab) group, with normal saline (NS) administered as negative control (NS group). The corneas were digitally photographed to calculate the CoNV percentage from the neovascularized corneal area at 1 and 2wk.

RESULTS

The 4 study groups did not have different CoNV percentages at 1wk after injury (P>0.05). However, the low LHT, high LHT, and bevacizumab groups had significantly lower CoNV percentages than the NS group at 2wk (all P<0.05). No significant differences in CoNV percentage were found among the low LHT, high LHT, and bevacizumab groups (all P>0.05). All groups except the NS group had lower CoNV percentages at 2wk post-injury than the levels observed at 1wk (all P<0.05).

CONCLUSION

Topically-administered LHT7 inhibited CoNV without complication after chemical cauterization in the rat.

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

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

Clinical Findings, Follow-up and Treatment Results in Patients with Ocular Rosacea

Objectives:

To report the clinical features, treatment options and complications in patients with ocular rosacea.

Materials and Methods:

The records of 48 eyes of 24 patients with ocular rosacea were retrospectively reviewed. Patients’ ocular signs and symptoms were scored between 1 and 4 points according to disease severity; tear film break-up time (BUT) and Schirmer’s test results were recorded before and after the treatment. Preservative-free artificial tears, topical antibiotic eye drops/ointments, short-term topical corticosteroids, topical 0.05% cyclosporine and oral doxycycline treatment were applied as a standard therapy to all patients. Additional treatments were given as needed. Complications were recorded.

Results:

Twenty-four patients with a mean age of 48.5±35.4 (32-54) years were followed for a mean 15±9.4 (8-36) months. Ocular findings included meibomitis in 100% of cases, anterior blepharitis in 83% (40 eyes), punctate keratopathy in 67% (32 eyes), chalazia in 50% (24 eyes), corneal neovascularization in 50% (24 eyes) and subepithelial infiltrates in 16.6% (8 eyes). Significant improvement of symptoms and clinical findings were achieved in all patients with treatment. The increases in Schirmer’s test and BUT were 3.3±1.5 and 4.5±2.8, respectively (p<0.05). Descemetocele and small corneal perforation occurred in 2 eyes; re-epithelialization was achieved in both eyes with tissue adhesive application (1 eye) and additional amniotic membrane transplantation (1 eye). Four eyes of three patients showed significant regression of corneal neovascularization with topical bevacizumab therapy.

Conclusion:

Ocular rosacea may present with a variety of ophthalmic signs. It is possible to control the ophthalmic disease with appropriate therapeutic modalities including topical corticosteroids, topical cyclosporine and systemic doxycycline.

The effects of topical everolimus and sunitinib on corneal neovascularization

PURPOSE

To evaluate the effects of topical everolimus and sunitinib on corneal neovascularization (CNV).

METHODS

CNV was induced by application of silver nitrate to the cornea for all groups. Rats were divided into four groups of 10 rats each, and two corneas were obtained from each rat. Group I received 1 mg/ml everolimus, Group II received 0.5 mg/ml sunitinib, Group IV received no treatment (control group) and Group IV received 1% Dimethylsulfoxide (DMSO). All treatments were administrated twice daily for 2 weeks. The right corneas were used for extracellular signal-regulated kinase 1/2 (ERK 1/2) protein analysis by western blot analysis and the left corneas were used for ERK 1/2 and vascular endothelial growth factor-receptor (VEGFR-2) gene expression analysis by quantitative real-time PCR.

RESULTS

VEGFR-2 mRNA expression levels (ΔCt, median, min-max) were reduced in the everolimus 1.0 (0.25-1.81) and sunitinib 1.06 (0.24-2.68) treated groups compared with the control 4.74 (1.02-14.74) and DMSO groups 7.41 (0.72-13.10). The expression of ERK 1/2 protein and mRNA levels were reduced in everolimus group compared with the control group (p < 0.05). These differences were not seen between the sunitinib and control groups.

CONCLUSION

Topical administration of both everolimus and sunitinib reduced VEGFR-2 levels and inhibited CNV. In additon, everolimus reduced ERK 1/2 levels and seems to be more effective than sunitinib on CNV.