Topical bevacizumab in the treatment of corneal neovascularization: results of a prospective, open-label, noncomparative study

Current trends in the management of corneal neovascularization

PURPOSE OF REVIEW

The aim of this study was to highlight recent developments in the medical and surgical management of corneal neovascularization (NV).

RECENT FINDINGS

Improved understanding and diagnostic criteria among clinicians have led to advancements in the characterization of corneal NV and objective assessment of treatment response through ancillary imaging devices. Developments in corneal NV treatments, such as antivascular endothelial growth factor, fine needle diathermy, and photodynamic therapy, have improved treatment success rates and visual outcomes. More recent surgical treatment advancements include corneal cross-linking, endothelial keratoplasty, and mitomycin intravascular chemoembolization. Finally, a greater appreciation of the molecular pathogenesis and angiogenic factors involved in corneal NV has identified numerous potential targeted therapies in the future.

SUMMARY

The management of corneal NV has evolved to include several standalone and combination medical and surgical options. Additionally, improvements in quantifying corneal NV and understanding its molecular basis have contributed to new management strategies with improved outcomes.

Clinical Outcomes of Topical Bevacizumab for the Treatment of Corneal Neovascularization

Background and objective In corneal neovascularization, the peri-corneal vascular structure grows into a normally avascular cornea. This is due to an imbalance between the angiogenic and anti-angiogenic factors that sustain corneal transparency. There are various etiologies of this condition, and they can be divided into infective or non-infective causes, such as inflammation, trauma, or surgical causes. Corneal neovascularization has been shown to improve with the current treatments using steroids and anti-vascular endothelial growth factors. This study aimed to evaluate the effectiveness of topical bevacizumab as an anti-angiogenic agent in patients with corneal neovascularization. Methods This retrospective study included patients who suffered corneal neovascularization of various etiologies and completed six months of topical bevacizumab therapy between 2020 and 2022 at the Universiti Kebangsaan Malaysia Medical Centre. Results A total of 16 patients received treatment with topical bevacizumab over the three-year study period. Based on specified inclusion and exclusion criteria, 12 patients were eligible for inclusion in this study. Eight patients (66%) showed improvement in terms of either 'clock hours' of improvement, morphology, or regression of corneal neovascularization. All infective causes of corneal neovascularization showed improvement on completion of bevacizumab compared to other causes. Conclusion Topical bevacizumab can be one of the treatment choices for corneal neovascularization. As the outcome varies depending on the severity and chronicity of the condition, the attending ophthalmologist should treat each case differently. Although topical bevacizumab is more effective in mild and moderate cases, the indications for its use in chronic cases remain debatable as the results are unfavorable in such cases.

Tissue-targeted and localized AAV5-DCN and AAV5-PEDF combination gene therapy abrogates corneal fibrosis and concurrent neovascularization in rabbit eyes in vivo

PURPOSE

Corneal fibrosis and neovascularization (CNV) after ocular trauma impairs vision. This study tested therapeutic potential of tissue-targeted adeno-associated virus5 (AAV5) mediated decorin (DCN) and pigment epithelium-derived factor (PEDF) combination genes in vivo.

METHODS

Corneal fibrosis and CNV were induced in New Zealand White rabbits via chemical trauma. Gene therapy in stroma was delivered 30-min after chemical-trauma via topical AAV5-DCN and AAV5-PEDF application using a cloning cylinder. Clinical eye examinations and multimodal imaging in live rabbits were performed periodically and corneal tissues were collected 9-day and 15-day post euthanasia. Histological, cellular, and molecular and apoptosis assays were used for efficacy, tolerability, and mechanistic studies.

RESULTS

The AAV5-DCN and AAV5-PEDF combination gene therapy significantly reduced corneal fibrosis (p < 0.01 or p < 0.001) and CNV (p < 0.001) in therapy-given (chemical-trauma and AAV5-DCN + AAV5-PEDF) rabbit eyes compared to the no-therapy given eyes (chemical-trauma and AAV5-naked vector). Histopathological analyses demonstrated significantly reduced fibrotic α-smooth muscle actin and endothelial lectin expression in therapy-given corneas compared to no-therapy corneas on day-9 (p < 0.001) and day-15 (p < 0.001). Further, therapy-given corneas showed significantly increased Fas-ligand mRNA levels (p < 0.001) and apoptotic cell death in neovessels (p < 0.001) compared to no-therapy corneas. AAV5 delivered 2.69 × 107 copies of DCN and 2.31 × 107 copies of PEDF genes per μg of DNA. AAV5 vector and delivered DCN and PEDF genes found tolerable to the rabbit eyes and caused no significant toxicity to the cornea.

CONCLUSION

The combination AAV5-DCN and AAV5-PEDF topical gene therapy effectively reduces corneal fibrosis and CNV with high tolerability in vivo in rabbits. Additional studies are warranted.

Ocular phenotype and therapeutic interventions in keratitis-ichthyosis-deafness (KID) syndrome

BACKGROUND

To report ocular manifestations, clinical course, and therapeutic management of patients with molecular genetically confirmed keratitis-ichthyosis-deafness syndrome.

METHODS

Four patients, aged 19 to 46, with keratitis-ichthyosis-deafness syndrome from across the UK were recruited for a general and ocular examination and GJB2 (Cx26) mutational analysis. The ocular examination included best-corrected visual acuity, slit-lamp bio-microscopy, and ocular surface assessment. Mutational analysis of the coding region of GJB2 (Cx26) was performed by bidirectional Sanger sequencing.

RESULTS

All four individuals had the characteristic systemic features of keratitis-ichthyosis-deafness syndrome. Each patient was found to have a missense mutation, resulting in the substitution of aspartic acid with asparagine at codon 50 (p.D50N). Main ophthalmic features were vascularizing keratopathy, ocular surface disease, hyperkeratotic lid lesions, recurrent epithelial defects, and corneal stromal scarring. One patient had multiple surgical procedures, including superficial keratectomies and lamellar keratoplasty, which failed to prevent severe visual loss. In contrast, oral therapy with ketoconazole stabilized the corneal and skin disease in two other patients with keratitis-ichthyosis-deafness syndrome. The patient who underwent intracorneal bevacizumab injection showed a marked reduction in corneal vascularization following a single application.

CONCLUSIONS

Keratitis-ichthyosis-deafness syndrome is a rare ectodermal dysplasia caused by heterozygous mutations in GJB2 (Cx26) with a severe, progressive vascularizing keratopathy. Oral ketoconazole therapy may offer benefit in stabilizing the corneal and skin disease.

A peptidic network antibody inhibits both angiogenesis and inflammatory response

Corneal neovascularization (CNV) is a global threat to human health. Traditional anti-angiogenesis agent may have therapy effect, while the inflammation in disease area remains unsolved. Herein, we reported two binding-induced fibrillogenesis (BIF) peptides as peptidic network antibodies for high-efficient and long-lasting anti-angiogenesis with reduced inflammatory response. BIF peptides could self-assemble into nanoparticles and further perform BIF behavior through binding Ca2+. In vitro, the migration of integrin αvβ3 highly expressed endothelial cells was inhibited by BIF peptides. In vivo, one BIF peptide (0.012 mg/Kg) exhibited higher anti-angiogenesis effect than monoclonal antibody bevacizumab (0.96 mg/Kg) in a CNV rabbit model on day 14, despite that the dose of BIF was only 1.3% of bevacizumab. Meanwhile, the inflammatory response, such as PI3 kinase/Akt pathway in CNV was successfully inhibited as well. The peptidic network antibody could block integrin αvβ3 via a long-term retention mode, which led to long-term therapeutic effect. The study provides BIF peptides as promising therapeutic agents for both anti-angiogenesis and reduced inflammatory response.

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.

Sustained Inhibition of VEGF and TNF-α Achieves Multi-Ocular Protection and Prevents Formation of Blood Vessels after Severe Ocular Trauma

PURPOSE

This study aimed to develop a clinically feasible and practical therapy for multi-ocular protection following ocular injury by using a thermosensitive drug delivery system (DDS) for sustained delivery of TNF-α and VEGF inhibitors to the eye.

METHODS

A thermosensitive, biodegradable hydrogel DDS (PLGA-PEG-PLGA triblock polymer) loaded with 0.7 mg of adalimumab and 1.4 mg of aflibercept was injected subconjunctivally into Dutch-belted pigmented rabbits after corneal alkali injury. Control rabbits received 2 mg of IgG-loaded DDS or 1.4 mg of aflibercept-loaded DDS. Animals were followed for 3 months and assessed for tolerability and prevention of corneal neovascularization (NV), improvement of corneal re-epithelialization, inhibition of retinal ganglion cell (RGC) and optic nerve axon loss, and inhibition of immune cell infiltration into the cornea. Drug-release kinetics was assessed in vivo using an aqueous humor protein analysis.

RESULTS

A single subconjunctival administration of dual anti-TNF-α/anti-VEGF DDS achieved a sustained 3-month delivery of antibodies to the anterior chamber, iris, ciliary body, and retina. Administration after corneal alkali burn suppressed CD45+ immune cell infiltration into the cornea, completely inhibited cornea NV for 3 months, accelerated corneal re-epithelialization and wound healing, and prevented RGC and optic nerve axon loss at 3 months. In contrast, anti-VEGF alone or IgG DDS treatment led to persistent corneal epithelial defect (combined: <1%; anti-VEGF: 15%; IgG: 10%, of cornea area), increased infiltration of CD45+ immune cells into the cornea (combined: 28 ± 20; anti-VEGF: 730 ± 178; anti-IgG: 360 ± 186, cells/section), and significant loss of RGCs (combined: 2.7%; anti-VEGF: 63%; IgG: 45%) and optic nerve axons at 3 months. The aqueous humor protein analysis showed first-order release kinetics without adverse effects at the injection site.

CONCLUSIONS

Concomitant inhibition of TNF-α and VEGF prevents corneal neovascularization and ameliorates subsequent irreversible damage to the retina and optic nerve after severe ocular injury. A single subconjunctival administration of this therapy, using a biodegradable, slow-release thermosensitive DDS, achieved the sustained elution of therapeutic levels of antibodies to all ocular tissues for 3 months. This therapeutic approach has the potential to dramatically improve the outcomes of severe ocular injuries in patients and improve the therapeutic outcomes in patients with retinal vascular diseases.

Successful regression of newly formed corneal neovascularization by subconjunctival injection of bevacizumab in patients with chemical burns

Purpose

To investigate the effect and timing of subconjunctival bevacizumab injection on inhibiting corneal neovascularization (CorNV) in patients after chemical burns.

Methods

Patients with CorNV secondary to chemical burns were involved. Two subconjunctival injections of bevacizumab (2.5 mg/0.1 mL per involved quadrant) with an interval of 4 weeks were administered, and followed up a year. The area occupied by neovascular vessels (NA), accumulative neovascular length (NL), mean neovascular diameter (ND), best-corrected visual acuity (BCVA) and intraocular pressure (IOP) were evaluated. Complication was also recorded.

Results

Eleven patients with CorNV were involved. Eight patients had a history of surgery (four had amniotic grafts, one had keratoplasty, and three had amniotic grafts and keratoplasty). Decreasing in NA, NL, and ND were statistically significant at each time point compared to the baseline (p < 0.01). CorNV that developed within 1 month was considerably regressed, and vessels with fibrovascular membranes were found to be narrower and shorter than pretreatment. BCVA improved in five patients (from one to five lines), remained unchanged in five patients, and decreased in one patient compared to pretreatment.

Conclusion

Subconjunctival bevacizumab injection has a particular potential for the regression of CorNV, especially newly formed within 1 month in patients after chemical burns.

The use of aflibercept (VEGF trap) in mitigating sulfur mustard-induced corneal neovascularization in a rabbit model

Sulfur mustard (SM)-induced ocular injury is characterized by an acute inflammatory response that may become chronic or enter a latent phase with delayed pathology. This study aimed to evaluate the efficacy of ziv-aflibercept and aflibercept in preventing and ameliorating corneal neovascularization (NV), respectively, following chemical eye exposure to SM vapor in a rabbit model. Chemical SM ocular insult was induced in the right eye of rabbits. A single application of ziv-aflibercept was administered 2 h or 9 days post-exposure. A single subconjunctival aflibercept treatment in an ocular formulation was administered 4 weeks after SM vapor exposure and subsequent to an initial 1-week treatment with 0.1 % dexamethasone. Clinical monitoring was performed 5-12 weeks post-exposure, and digital corneal pictures were taken to assess the extent of NV. The rabbits were euthanized and the corneas were processed for histological assessment. Treatment with ziv-aflibercept 2 h and 9 days post-exposure moderately reduced insult severity and partially delayed or prevented corneal NV. Aflibercept application 4 weeks post-exposure significantly reduced the extent of NV for 8 weeks. The substantial decrease in existing corneal NV in this group was confirmed by histology. These results reveal the powerful anti-angiogenic efficacy of the VEGF-trap for ameliorating existing NV as opposed to preventing NV development, revealing the ability of this treatment to mitigate corneal NV.

Bevacizumab in High-Risk Corneal Transplantation: A Pilot Multicenter Prospective Randomized Control Trial

PURPOSE

To determine the efficacy of local (subconjunctival and topical) bevacizumab (Avastin) treatment in patients undergoing vascularized high-risk corneal transplantation.

DESIGN

Pilot, prospective, randomized, double-blind, placebo-controlled clinical trial conducted at 5 clinical centers in the United States, India, and Brazil.

PARTICIPANTS

Patients aged > 18 years undergoing high-risk penetrating keratoplasty, defined as corneal neovascularization (NV) in 1 or more quadrants ≥2 mm from the limbus or extension of corneal NV to the graft-host junction in a previously failed graft.

METHODS

Patients were randomized to receive subconjunctival bevacizumab (2.5 mg/0.1 ml) or placebo at the time of surgery, followed by topical bevacizumab (10 mg/ml) or topical placebo, administered 4 times per day for 4 weeks.

MAIN OUTCOME MEASURE

The 52-week endothelial immune rejection rate.

RESULTS

Ninety-two patients were randomized to receive bevacizumab (n = 48) or control (n = 44). The 52-week endothelial rejection rate was 10% in the bevacizumab group and 19% in the control group (P = 0.20). Post hoc, extended follow-up at the lead study site showed an endothelial rejection rate of 3% in the bevacizumab group and 38% in the control group (P = 0.003). Treatment with bevacizumab was found to have a hazard ratio of 0.15 (95% confidence interval, 0.03-0.65, P = 0.01) in a post hoc Cox regression analysis.

CONCLUSIONS

In patients undergoing vascularized high-risk corneal transplantation, there was no statistically significant difference in the rate of endothelial rejection at 1 year in the bevacizumab treatment group compared with the control group. This study may have been underpowered to detect a difference between treatment groups, and taken together, our data suggest that, in the current trial design, bevacizumab has a positive but not (yet) significant effect on endothelial rejection.

Bevacizumab Eye Drops Vs. Intra-meibomian Gland Injection of Bevacizumab for Meibomian Gland Dysfunction-Associated Posterior Blepharitis

Aims

This study aimed to evaluate the efficacy and safety of bevacizumab eye drops compared with those of an intra-meibomian gland (MG) injection of bevacizumab when performed in conjunction with standard lid hygiene in patients with meibomian gland dysfunction (MGD)-associated posterior blepharitis.

Methods

This prospective, open-label, observer-blinded randomized controlled trial included 60 eyes of 30 patients with MGD-associated posterior blepharitis who exhibited lid margin telangiectasia, treated at the Chula Refractive Surgery Center of King Chulalongkorn Memorial Hospital. Patients were randomized to receive lid hygiene plus 0.05% bevacizumab eye drops or a single intra-MG injection of 2.5% bevacizumab. All patients were instructed to perform routine lid hygiene care as demonstrated in an instructional video. Primary outcomes included telangiectasia grading and the lid margin neovascularized area (LMNA). Secondary outcomes included the Ocular Surface Disease Index (OSDI) score, corneal staining, meibum quality, meiboscore, conjunctival redness, fluorescein break-up time (FBUT), lipid layer thickness, treatment compliance, and adverse events. All parameters were evaluated before and 3 months after treatment.

Results

After treatment, there were no significant differences in telangiectasia grade and LMNA between groups (mean difference, −0.14, 95% CI −0.42 to 0.15, p = 0.338, −0.1, 95% CI −1.1 to 0.8, p = 0.761, respectively); however, the injection group exhibited significant improvements in both telangiectasia grade and LMNA, while, in the eye drop group, only telangiectasia grade showed a significant improvement relative to baseline. The injection group also exhibited significant improvements in corneal staining (mean difference, −0.78, 95% CI −1.29 to −0.27, p = 0.003), meiboscores (mean difference, −0.37, 95% CI −0.52 to −0.21, p <0.001), and FBUT (mean difference, 1.25, 95% CI 0.21–2.29, p = 0.019) compared to the eye drop group. OSDI scores, corneal staining, meibum quality, meiboscores, and conjunctival redness significantly improved relative to baseline in both groups. No local and systemic adverse event was observed at month 3 in both groups.

Conclusion

When performed with regular lid hygiene, intra-MG injection and topical application of bevacizumab are safe and effective for improving lid margin telangiectasia and the signs and symptoms of MGD-associated posterior blepharitis. This therapy may represent an alternative or adjunctive treatment for patients with MGD-associated posterior blepharitis.

Customized cationic nanoemulsions loading triamcinolone acetonide for corneal neovascularization secondary to inflammatory processes

Customized cationic oil-in-water nanoemulsions (NEs) have been produced to improve the bioavailability of poorly water-soluble drugs, such as triamcinolone acetonide (TA). TA is a synthetic glucocorticoid with anti-inflammatory and antiangiogenic therapeutic properties and it is widely used as an effective treatment in ocular disorders. In this work, TA-NEs were characterized using two different custom-made cationic surfactants, showing a high positive surface charge favouring corneal penetration and a particle size below 300 nm. Both TA-NE formulations demonstrated to be stable at 4 °C during the first months of storage. Furthermore, TA-NEs were able to produce antiangiogenic effects in chicken membranes. The TA-NEs safety profile was evaluated using in vitro and in vivo ocular tolerance tests. Out of the two formulations, the one showing no irritant effects was screened in vivo demonstrating capacity to ameliorate ocular inflammation in New Zealand rabbits significantly, specially to reduce the risk of ocular inflammation processes, with antiangiogenic activity, and can therefore be exploited as a suitable formulation to avoid inflammatory reactions upon ocular surgical procedures, such as cataracts.

Epidemiology of Corneal Neovascularization and Its Impact on Visual Acuity and Sensitivity: A 14-Year Retrospective Study

Purpose: To quantify the severity and location of corneal neovascularization (cNV) and its impact on the visual acuity and corneal sensitivity in a cohort of the patients referred to a specialist cornea clinic and also to describe the etiology of cNV in the cohort.

Methods: We retrospectively evaluated the charts of 13,493 subjects referred to the San Raffaele Cornea Unit between January 2004 and December 2018 to search for cNV diagnosis. The corneal neovascularization severity was measured in the quadrants (range: 1–4) and location was defined as superficial, deep, or both. Best spectacle corrected visual acuity (BSCVA) was measured in logMar. We used the multiple regression analysis to identify the independent predictors of logMAR, after adjusting for age, gender, keratoconus, herpes keratitis, penetrating keratoplasty, trauma, and cataract surgery.

Results: Corneal neovascularization was diagnosed in 10.4% of the patients analyzed. The most prevalent etiology of cNV in our population was non-infectious corneal dystrophies/degenerations followed by herpes simplex virus infection. cNV affected OD, OS, or both eyes in 35.6, 40.2, and 24.2 of cases, respectively. Mean BSCVA (SD) was 0.59 (0.76), 0.74 (0.94), and 1.24 (1.08) in cNV one, two, and three or four of the quadrant groups. Superficial, deep, or mixed cNV occurred in 1,029, 348, and 205 eyes. Severe cNV (three or four of the quadrants) was a significant predictor of low visual acuity (p < 0.001) and reduced corneal sensitivity (p < 0.05). cNV location and its severity were associated (p < 0.05). In addition, corneal anesthesia was associated with lower BSCVA (p < 0.001).

Conclusion: Severe and deep cNV are associated with the reduced visual acuity and corneal sensitivity. Our data strongly support the relevance of appropriate follow-up as cNV is a major risk factor for graft rejection.

A Hypothalamic-Controlled Neural Reflex Promotes Corneal Inflammation

Purpose

To test whether an acute corneal injury activates a proinflammatory reflex, involving corneal sensory nerves expressing substance P (SP), the hypothalamus, and the sympathetic nervous system.

Methods

C57BL6/N (wild-type [WT]) and SP-depleted B6.Cg-Tac1tm1Bbm/J (TAC1-KO) mice underwent bilateral corneal alkali burn. One group of WT mice received oxybuprocaine before alkali burn. One hour later, hypothalamic neuronal activity was assessed in vivo by magnetic resonance imaging and ex vivo by cFOS staining. Some animals were followed up for 14 days to evaluate corneal transparency and inflammation. Tyrosine hydroxylase (TH), neurokinin 1 receptor (NK1R), and neuronal nitric oxide synthase (nNOS) expression was assessed in brain sections. Sympathetic neuron activation was evaluated in the superior cervical ganglion (SCG). CD45⁺ leukocytes were quantified in whole-mounted corneas. Noradrenaline (NA) was evaluated in the cornea and bone marrow.

Results

Alkali burn acutely induced neuronal activation in the trigeminal ganglion, paraventricular hypothalamus, and lateral hypothalamic area (PVH and LHA), which was significantly lower in TAC1-KO mice (P < 0.05). Oxybuprocaine application similarly reduced neuronal activation (P < 0.05). TAC1-KO mice showed a reduced number of cFOS⁺/NK1R⁺/TH⁺ presympathetic neurons (P < 0.05) paralleled by higher nNOS expression (P < 0.05) in both PVH and LHA. A decrease in activated sympathetic neurons in the SCG and NA levels in both cornea/bone marrow and reduced corneal leukocyte infiltration (P < 0.05) in TAC1-KO mice were found. Finally, 14 days after injury, TAC1-KO mice showed reduced corneal opacity and inflammation (P < 0.05).

Conclusions

Our findings suggest that stimulation of corneal sensory nerves containing SP activates presympathetic neurons located in the PVH and LHA, leading to sympathetic activation, peripheral release of NA, and corneal inflammation.

Efficacious, safe, and stable inhibition of corneal neovascularization by AAV-vectored anti-VEGF therapeutics

Corneal neovascularization (CoNV) leads to visual impairment, affecting over 1.4 million people in the United States per year. It is caused by a variety of pathologies, such as inflammation, hypoxia, and limbal barrier dysfunction. Injection of the anti-vascular endothelial growth factor (VEGF) drug KH902 (conbercept) can inhibit CoNV but requires repeated dosing that produces associated side effects, such as cornea scar. To explore more efficacious and long-lasting treatment of CoNV, we employed recombinant adeno-associated virus (rAAV)2 and rAAV8 vectors to mediate KH902 expression via a single intrastromal injection and investigated its anti-angiogenic effects and safety in both alkali-burn- and suture-induced CoNV mouse models. Our results showed that rAAV-mediated KH902 mRNA expression in the cornea was sustained for at least 3 months after a single intrastromal injection. Moreover, the expression level of rAAV8-KH902 far exceeded that of rAAV2-KH902. A single-dose rAAV8-KH902 treatment at 8 × 10⁸ genome copies (GCs) per cornea dramatically inhibited CoNV for an extended period of time in mouse CoNV models without adverse events, whereas the inhibition of CoNV by a single intrastromal administration of the conbercept drug lasted for only 10−14 days. Overall, our study demonstrated that the treatment of CoNV with a single dose of rAAV8-KH902 via intrastromal administration was safe, effective, and long lasting, representing a novel therapeutic strategy for CoNV.

Topical bevacizumab for the treatment of corneal vascularization in dogs: A case series

Objective

To evaluate the effect and safety of topical anti‐human vascular endothelial growth factor bevacizumab in dogs with persistent corneal vascularization.

Animals studied

Prospective case series of 15 adult dogs (20 eyes).

Procedures

Dogs received 0.25% bevacizumab eye drops BID for 28 days. Follow‐ups were scheduled 28 days and 6–7 months after treatment start. Macroscopic findings were scored for conjunctival hyperemia, chemosis, ocular discharge, corneal edema, vascularization, and pigmentation. Vascularized area was assessed by analyzing photographs using an imaging software.

Results

The treatment response was variable. Some cases showed a marked reduction in vascularized area and edema, while other eyes had subtle signs of improvement. Vascularization score decreased from 1.5 to 1.1 and vascularized area was reduced by 48.8% after 28 days. A thinning of vessels, consolidation of areal bleedings into fine vascular networks, decrease in distal vessel branching, and a change from blurry vascularized beds into demarcated thin vessels were observed. One dog developed a SCCED 6 months after the last bevacizumab administration. Two dogs died 4 and 4.5 months after the last bevacizumab administration, aged 16 and 12 years, respectively. In all events, a causal relationship is unlikely but cannot be ruled out with certainty.

Conclusions

Our findings suggest that topical 0.25% bevacizumab may be an effective treatment option for corneal vascularization in dogs. Further long‐term placebo‐controlled studies with larger patient cohorts are recommended to provide scientific evidence of efficacy and to investigate dosage, safety, possible use as a single treatment, and routes of administration.

Regulatory T Cells in Angiogenesis

Regulatory T cells (Tregs) are crucial mediators of immune homeostasis. They regulate immune response by suppressing inflammation and promoting self-tolerance. In addition to their immunoregulatory role, a growing body of evidence highlights the dynamic role of Tregs in angiogenesis, the process of forming new blood vessels. Although angiogenesis is critically important for normal tissue regeneration, it is also a hallmark of pathological processes, including malignancy and chronic inflammation. Interestingly, the role of Tregs in angiogenesis has been shown to be highly tissue- and context-specific and as a result can yield either pro- or antiangiogenic effects. For these reasons, there is considerable interest in determining the molecular underpinnings of Treg-mediated modulation of angiogenesis in different disease states. The present review summarizes the role of Tregs in angiogenesis and mechanisms by which Tregs regulate angiogenesis and discusses how these mechanisms differ in homeostatic and pathological settings.

Subconjunctival Aflibercept for the Treatment of Formed Corneal Neovascularization

PURPOSE

To evaluate the effect of a single subconjunctival aflibercept injection on formed corneal neovascularization.

METHODS

A prospective clinical trial, conducted at a single tertiary medical center. Included were consecutive patients with corneal pathologies complicated by corneal neovascularization, who were candidates for anti-vascular endothelial growth factor treatment at the discretion of a cornea specialist. A single subconjunctival injection of 0.08 mL of Aflibercept (Eylea 25 mg/mL) was administered near the limbus in proximity to the areas of maximal pathological neovascularization. Follow-up visits were scheduled on days 7, 30, 60, and 90 following injection. Best-corrected visual acuity (BCVA), intraocular pressure, slitlamp examination, digital cornea photography, specular microscopy, and anterior-segment optical coherence tomography were documented at each visit. The images were graded by a masked observer for density, extent, and centricity of corneal vascularization.

RESULTS

Six eyes of six patients were analyzed. No clinically significant ocular or systemic adverse events were documented. No change was noted in extent, density, or centricity of corneal blood vessels at seven, 30, and 90 days after injection (P>0.1 for all time point comparisons, Friedman test). Best-corrected visual acuity fluctuated insignificantly in 5/6 patients during follow-up time, and objective but not subjective improvement of BCVA was noted in one patient with no concurrent change of neovascularization. The recruitment has therefore halted prematurely.

CONCLUSIONS

A single subconjunctival aflibercept injection seems to be well tolerated. However, it is ineffective for regressing formed corneal neovascularization.

Assessment of In-Situ Gelling Microemulsion Systems upon Temperature and Dilution Condition for Corneal Delivery of Bevacizumab

Bevacizumab (BVZ), a recombinant humanized monoclonal antibody, has recently been proposed as a topical application in the treatment of anterior segment neovascularization; however, as there are some disadvantages in the administration of common eye-drops, ophthalmic topical drug delivery systems are under study to improve the precorneal residence time, reducing the frequency of administration. In this work, oil-in-water and water-in-oil BVZ-loaded microemulsions are developed, able to increase their viscosity, either by the formation of a liquid-crystalline structure upon aqueous dilution, thanks to the presence of Epikuron® 200 and polysorbate 80, or by body-temperature-induced jellification for the presence of Pluronic® F127 aqueous solution as an external phase. In oil-in-water microemulsion, hydrophobic ion pairs of BVZ were also prepared, and their incorporation was determined by release studies. Microemulsions were characterized for rheological behavior, corneal opacity, in vitro corneal permeation, and adhesion properties. The studied microemulsions were able to incorporate BVZ (from 1.25 to 1.6 mg/mL), which maintained dose-dependent activity on retinal pigment epithelial ARPE-19 cell lines. BVZ loaded in microemulsions permeated the excised cornea easier (0.76-1.56% BVZ diffused, 4-20% BVZ accumulated) than BVZ commercial solution (0.4% BVZ diffused, 5% accumulated) and only a mild irritation effect on the excised cornea was observed. The good adhesion properties as well the increased viscosity after application, under conditions that mimic the corneal environment (from 1 × 103 to more than 100 × 103 mPa·s), might prolong precorneal residence time, proving these systems could be excellent topical BVZ release systems.

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.

Lipid Keratopathy: A Review of Pathophysiology, Differential Diagnosis, and Management

Lipid keratopathy is a disease in which fat deposits accumulate in the cornea, leading to opacification and decrease of visual acuity. This condition can be idiopathic without signs of previous corneal disease or secondary to ocular or systemic diseases. Lipid keratopathy is usually associated with abnormal vascularization of the cornea, and the lipid classically deposits adjacent to these vessels. Treatment of this condition usually aims to eliminate or prevent abnormal vessel formation, and several modalities have been described. In this review we summarize the etiology, pathophysiology, and clinical presentation of lipid keratopathy and describe current and emerging treatment regimens.

Corneal Recovery Following Rabbit Peripheral Blood Mononuclear Cell-Amniotic Membrane Transplantation with Antivascular Endothelial Growth Factor in Limbal Stem Cell Deficiency Rabbits

Background: Limbal stem cell deficiency (LSCD) is a refractory ocular surface disorder characterized by progressive corneal epithelial degeneration, conjunctivalization, and neovascularization, potentially leading to blindness. There are currently no effective therapeutic options for patients experiencing routine symptomatic treatment failure. Transplantation of amniotic membrane (AM) with adherent stem cells (but not bare AM transplantation alone) has shown promise in preclinical studies for ocular surface restoration. A major limitation, however, is finding a reliable stem cell source. Stem cells can be isolated from the peripheral blood mononuclear cell (PBMC) population, and these PBMC-derived stem cells have numerous advantages over allogeneic and other autologous stem cell types for therapeutic application, including relative ease of acquisition, nonimmunogenicity, and the absence of ethical issues associated with embryonic stem cells. Experiment: We examined the efficacy of autologous PBMC-AM sheet cultures combined with postoperative antiangiogenesis treatment for corneal restoration in LSCD model rabbits. Rabbit PBMCs (rPBMCs) were isolated, labeled with EdU for in vivo tracing, and then cultured on AMs in conditioned medium before transplantation. Rabbits were transplanted with bare AMs (group 1), rPBMC-AM sheets (group 2), or rPBMC-AM sheets plus postoperative treatment with the vascular endothelial growth factor antagonist bevacizumab (group 3). Corneal opacity and neovascularization were monitored by slit-lamp imaging for 8 weeks and corneas were examined histologically at 1 and 2 months. Results: Corneal opacity decreased in all three groups over 8 weeks, but was significantly lower in group 2 and even lower in group 3. Corneal neovascularization was significantly higher in group 1 throughout the observation period, and significantly lower in group 3 than group 1 and 2 by 8 weeks post-transplant. At 4 weeks, the corneal surface completed epithelialization (although thinner than normal) in group 3 but still patchy in groups 1 and 2. By 8 weeks, the epithelium in group 3 was complete and smooth, resembling a normal epithelium. Integrin β1 as a progenitor marker was also generally higher in groups 2 and 3. Conclusions: Autologous rPBMC-AM sheets with post-transplant topical bevacizumab can effectively facilitate corneal epithelium recovery in a LSCD model, suggesting clinical utility for LSCD-related ocular surface diseases. Impact statement Limbal stem cell deficiency (LSCD) increases corneal opacity and vascularization, resulting in severe visual impairment or even blindness. Traditional surgical limbal transplant is currently the main treatment option for LSCD, but carries the risks of rejection and immunosuppressant side effects. Autologous stem cell-based therapy is a promising alternative approach, but a reliable stem cell source is a major limitation. We report that transplantation of autologous rabbit peripheral blood mononuclear cell-amniotic membrane sheets plus antivascular endothelial growth factor restored avascular transparent cornea in a rabbit LSCD model. These results demonstrate a potentially effective approach for ocular surface reconstruction in bilateral LSCD.

Inhibitory Effect of Topical Cartilage Acellular Matrix Suspension Treatment on Neovascularization in a Rabbit Corneal Model

BACKGROUND

The extracellular matrix (ECM) of articular cartilage has an inhibitory effect on vascularization, yet clinical utilization has been technically challenging. In this study, we aimed to fabricate a biologically functional ECM powder suspension from porcine articular cartilage that inhibits neovascularization (NV).

METHODS

The digested-cartilage acellular matrix (dg-CAM) was prepared by sequential processes of decellularization, enzymatic digestion and pulverization. Physicochemical properties of dg-CAM were compared with that of native cartilage tissue (NCT). Cellular interactions between human umbilical vein endothelial cells (HUVECs) and dg-CAM was evaluated with proliferation, migration and tube formation assays compared with that of type I collagen (COL) and bevacizumab, an anti-angiogenic drug. We then investigated the therapeutic potential of topical administration of dg-CAM suspension on the experimentally induced rabbit corneal NV model.

RESULTS

The dg-CAM released a significantly larger amount of soluble proteins than that of the NCT and showed an improved hydrophilic and dispersion properties. In contrast, the dg-CAM contained a large amount of collagen, glycosaminoglycans and anti-angiogenic molecules as much as the NCT. The inhibitory effect on NV of the dg-CAM was more prominent than that of COL and even comparable to that of bevacizumab in inhibiting the HUVECs. The therapeutic potential of the dg-CAM was comparable to that of bevacizumab in the rabbit corneal NV model by efficiently inhibiting neovessel formation of the injured cornea.

CONCLUSION

The current study developed a dg-CAM having anti-angiogenic properties, together with water-dispersible properties suitable for topical or minimally invasive application for prevention of vessel invasion.

Carbon Dots Fabrication: Ocular Imaging and Therapeutic Potential

Vision loss is a major complication in common ocular infections and diseases such as bacterial keratitis, age-related macular degeneration (AMD) and diabetic retinopathy (DR). The prevalence of such ophthalmic diseases represents an urgent need to develop safe, effective, and long-term treatments. Current therapies are riddled with drawbacks and limitations which calls for the exploration of alternative drug delivery mechanisms. Toxicity of the inorganic metals and metal oxides used for drug delivery raise safety concerns that are alleviated with the alternate use of, a natural and organic polymer which is both biocompatible and environmentally friendly. Carbon dots (CDs) represent a great potential in novel biomedical applications due to their tunable fluorescence, biocompatibility, and ability to be conjugated with diverse therapeutic materials. There is a growing interest on the exploitation of these properties for drug delivery with enhanced bio-imaging. However, there are limited reports of CD applications for ophthalmic indications. In this review, we focus on the CD potential and the development of translational therapies for ophthalmic diseases. The current review presents better understanding of fabrication of CDs and how it may be useful in delivering anti-bacterial agents, anti-VEGF molecules as well as imaging for ophthalmic applications.

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.

Sunitinib malate-loaded biodegradable microspheres for the prevention of corneal neovascularization in rats

Corneal neovascularization (NV) predisposes patients to compromised corneal transparency and visional acuity. Sunitinib malate (Sunb-malate) targeting against multiple receptor tyrosine kinases, exerts potent antiangiogenesis. However, the rapid clearance of Sunb-malate eye drops administered through topical instillation limits its therapeutic efficacy and poses a challenge for potential patient compliance. Sunb-malate, the water-soluble form of sunitinib, was shown to have higher intraocular penetration through transscleral diffusion following subconjunctival (SCT) injection in comparison to its sunitinib free base formulation. However, it is difficult to load highly water-soluble drugs and achieve sustained drug release. We developed Sunb-malate loaded poly(D,L-lactic-co-glycolic acid) (PLGA) microspheres (Sunb-malate MS) with a particle size of approximately 15 μm and a drug loading of 7 wt%. Sunb-malate MS sustained the drug release for 30 days under the in vitro infinite sink condition. Subconjunctival (SCT) injection of Sunb-malate MS provided a prolonged ocular drug retention and did not cause ocular toxicity at a dose of 150 μg of active agent. Sunb-malate MS following SCT injection more effectively suppressed the suture-induced corneal NV than either Sunb-malate free drug or the placebo MS. Local sustained release of Sunb-malate through the SCT injection of Sunb-malate MS mitigated the proliferation of vascular endothelial cells and the recruitment of mural cells into the cornea. Moreover, the gene upregulation of proangiogenic factors induced by the pathological process was greatly neutralized by SCT injection of Sunb-malate MS. Our findings provide a sustained release platform for local delivery of tyrosine kinase inhibitors to treat corneal NV.

Effects of VEGF Inhibitor Conbercept on Corneal Neovascularization Following Penetrating Keratoplasty in Rabbit Model

Purpose

To evaluate the effects of the vascular endothelial growth factor inhibitor conbercept (KH902) on corneal neovascularization and wound healing following penetrating keratoplasty in rabbits.

Methods

Conbercept was administered to New Zealand white rabbits through topical and subconjunctival routes. Corneal neovascularization and wound healing were examined by slit-lamp photography and histological analyses. The expressions of vascular endothelial growth factor inhibitor, α-smooth muscle actin, and keratocan in the corneal grafts were measured by real-time quantitative polymerase chain reaction (RT-qPCR).

Results

The anterior segment photographs demonstrated that corneal neovascularization started in the 2nd week. In the 4th week, histologically, the superficial corneal stroma layer showed disordered arrangement, and there were large numbers of dense inflammatory cells and blood vessels in the stroma layer. Vascular endothelial growth factor in the experimental groups was significantly decreased at all time points compared with the control group (both P = 0.001). Expression of α-smooth muscle actin in corneal grafts demonstrated an increase in time even it was lower in experimental groups, but the difference was not statistically significant (P equaled to 0.507 and 0.723, respectively). There were no significant differences with the expression of keratocan in all groups except that it significantly declined at the 4th week as to the second week in all groups and P values were 0.022, 0.020 and 0.014 in control (C), topical (E1), and subconjunctival (E2) group, respectively.

Conclusion

The study found that conbercept inhibited the formation of corneal neovascularization without affecting keratocan-mediated corneal wound healing and there were no significant differences between topical administration of different doses of conbercept on the rabbit corneal neovascularization after penetrating keratoplasty in this study.

Long-term topical bevacizumab for prevention of corneal graft rejections

Purpose:

To evaluate the safety and efficacy of 1% topical bevacizumab (10 mg/mL) on newly formed corneal neovascularization (NV) after penetrating keratoplasty (PK).

Methods:

This is a retrospective case series reporting three eyes (three patients) of with newly formed corneal NV after corneal transplantation. All eyes had pre-existing corneal NVs and were high risk corneal graft rejection cases. One percent topical bevacizumab was started immediately after corneal NV formation post-PK. Topical bevacizumab was kept at twice weekly throughout the follow-up period.

Results:

Regression of corneal NV without donor graft invasion was noted in all three patients (100%). Duration of topical bevacizumab use was 13 to 36 months. All three corneal grafts (100%) remained clear and no signs of graft rejection were noted for the period of observation. There were no associated systemic or ocular adverse effects.

Conclusion:

Long-term use of topical 1% bevacizumab may be a safe and efficient treatment for corneal NVs and prevention of graft rejections after corneal transplantation.

Microporous Drug Delivery System for Sustained Anti-VEGF Delivery to the Eye

Purpose

To describe a novel microporous drug delivery system (DDS) for sustained anti- vascular endothelial growth factor (VEGF) delivery to the eye and to evaluate its efficacy in a corneal injury model.

Methods

A macro-porous DDS (1.5 × 1.5 × 4 mm) loaded with 2 mg of bevacizumab was implanted subconjunctivally in three Dutch-belted pigmented rabbits after corneal alkali injury (2N NaOH). Three rabbits received sham DDS. Animals were followed for three months and assessed in vivo and ex vivo for corneal neovascularization (NV), epithelial defect, stromal scarring, endothelial cell loss, and expression of angiogenic and inflammatory markers in the cornea and retina.

Results

Anti-VEGF DDS treatment led to complete inhibition of superior cornea NV and complete corneal re-epithelialization by day 58 whereas sham DDS resulted in severe cornea NV and persistent epithelial defect (9%∼12% of total cornea area) through the end of the study. Histologically, anti-VEGF DDS significantly reduced CD45⁺ and F4/80 CD11b⁺ cell accumulation (79%, P < 0.05) in the cornea, ameliorated tumor necrosis factor–α expression (90%, P < 0.05), reduced corneal stromal scarring and prevented corneal endothelial cell loss, as compared to sham DDS. Moreover, anti-VEGF DDS achieved retinal penetration and reduction in retinal VEGF levels at 3 months.

Conclusions

Use of subconjunctival anti-VEGF DDS suppresses cornea NV, inflammation, stromal scarring, prevents endothelial cell loss, and abrogates retinal VEGF upregulation in a rabbit corneal alkali burn model. Moreover, it delivers anti-VEGF antibodies to the retina for three months. This delivery platform could enable antibody therapy of other corneal and retinal vascular pathologies.

Translational Relevance

We describe a method for sustained anti-VEGF delivery to the eye for the treatment of ocular injuries.

Topical VEGF-C/D Inhibition Prevents Lymphatic Vessel Ingrowth into Cornea but Does Not Improve Corneal Graft Survival

Vascular endothelial growth factor-C/D (VEGF-C/D) regulates lymphangiogenesis. Ingrowth of lymphatic vessels is negatively associated with corneal transplantation success. In this study, we therefore analyzed the effect local blockade of VEGF-C/D has on inflamed corneas. We used the murine model of suture-induced neovascularization and subsequent high-risk corneal transplantation. Mice were treated with a VEGF-C/D trap prior to transplantation. Topical inhibition of VEGF-C/D significantly reduced lymphatic vessel ingrowth, but increased Macrophage numbers in the cornea. Furthermore, corneal transplantation success was not improved by the topical application of the compound. This study demonstrates that local VEGF-C/D inhibition is insufficient to increases corneal transplantation success, likely due to interaction with immune cells.

Prevention of Corneal Neovascularization; a Preliminary Experimental Study in Rabbits

The purpose of this study was to compare the effects of propranolol, timolol and bevacizumab with betamethasone to prevent corneal neovascularization (CNV) in rabbits. This study was performed on 28 male rabbits. CNV was induced by three 7-0 silk sutures 2 mm long and 1 mm distal to the limbus. Animals were randomly divided into 4 groups of propranolol + betamethasone, timolol + betamethasone and bevacizumab + betamethasone and betamethasone alone. Eye drops were started from the first day of study. On 7^th, 14^th, 21^st, 28^th, 35^th and 42^nd days, vascular progression, time of neovascularization and vascular area were evaluated and compared with the control group (betamethasone alone). There was a significant reduction in the area of ​​neovascularization in the timolol and bevacizumab groups compared to the control group (P-value = 0.05, P=0.047, respectively). Also, regarding vascular progression, there was a significant decrease in the timolol and bevacizumab groups (P-value = 0.014, P=0.002, respectively). Regarding delayed onset of neovascularization, there was a significant difference in the timolol and bevacizumab group in rabbits (P-value = 0.04, P=0.00, respectively). In conclusion, the use of timolol and bevacizumab drops besides betamethasone can delay neovascularization and decrease the length of corneal vascularization in rabbits.

Development of Kaempferol-Loaded Gelatin Nanoparticles for the Treatment of Corneal Neovascularization in Mice

Cornea is the transparent layer in front of the eye that does not contain blood vessels. Among eye diseases, corneal neovascularization (NV) is one of the major causes of vision loss, since it can also lead to blindness. An herbal extraction containing flavonoid, kaempferol (KA), with antiangiogenic effect was chosen as a candidate drug for inhibited vessel formation. The use of nanomedicine has led to higher drug bioavailability and slow release of the drug as an effective therapeutic formulation in ocular drug delivery. In this study, we prepared gelatin nanoparticles (GNP) with kaempferol encapsulation (GNP-KA) for corneal NV treatment by topical delivery, i.e., eye drops. We found that GNP with/without KA loading was in the size of 85-150 nm, and its zeta potential was around 22-26 mV. The KA entrapment rate of GNP-KA was around 90-98%, and the loading rate was about 4.6%. The TEM results clearly indicated the GNP-KA NPs to be round spheres. The in vitro test involved the adoption of human umbilical vein endothelial cells (HUVECs) for coculture with these nanoparticles. From WST-8 assay, and cell migration examinations, it was evident that GNP-KA had the capacity to inhibit the cell viability and function of HUVECs. The results from in vivo tests such as ocular vessels observation, hematoxylin & eosin (H&E) stain, and metalloproteinases (MMP)/vascular endothelial growth factor (VEGF) quantification revealed the mice's eyes with corneal NV treated by eye drops containing GNP-KA once daily for 7 days had better therapeutic effects with less vessels in-growths in the cornea, compared to the KA solution group by reducing the production of MMP and VEGF in the cornea. Therefore, we expected to achieve a comfortable treatment with a simple method using nanomedicine (GNP-KA) as ophthalmological agent delivered as eye drops.

Optical Coherence Tomography Angiography Imaging to monitor Anti-VEGF treatment of Corneal Vascularization in a Rabbit Model

Optical coherence tomography angiography (OCTA) is a well-established non-invasive retinal vascular imaging technique. It has been recently adapted to image the anterior segment and has shown good potential to image corneal vascularisation. The purpose of the study is to evaluate the usefulness of OCTA to monitor regression of corneal vessels following anti-VEGF (vascular endothelial growth factor) treatment using a previously established corneal vascularisation rabbit model. The regression of vessels following the treatment with aflibercept and ranibizumab anti-VEGFs using both topical instillation and sub-conjunctival injection was quantified using OCTA and compared with ICGA (indocyanine green angiography). Overall vessel density measurements using OCTA showed good correlation (r = 0.988, p < 0.001) with ICGA, with no significant difference between the two treatment groups (p = 0.795). It was also shown that OCTA provided good repeatability outcomes of the quantitative measurements. Using Bland-Altman plots, vessel growth density values between anti-VEGF treatments were compared to control saline group. It was observed that aflibercept provided longer lasting effect than ranibizumab. We also observed that in both drugs, the topical route of administration topical provided longer regression outcomes compared to one-time sub-conjunctival injection. Thereby, with this pilot study, it was demonstrated that OCTA is a reliable imaging technique to follow-up and monitor corneal vascularisation and its treatment quantitatively.

Intrastromal bevacizumab in the management of corneal neovascularization: a retrospective review

PURPOSE

To evaluate the long-term safety and efficacy of intrastromal bevacizumab for treatment of deep corneal neovascularization in candidates for high-risk cornea grafting.

METHODS

A single-center retrospective study involving 14 eyes of 14 patients with chronic deep corneal neovascularization, treated with intrastromal bevacizumab by a single provider from 2011 to present. Intrastromal bevacizumab (0.05-0.1 mL of 2.5 mg/0.1 mL) was administered every 4-8 weeks. On average 1-3 intrastromal injections were performed prior to corneal grafting (penetrating keratoplasty or deep anterior lamellar keratoplasty).

RESULTS

64.2% patients had neurotrophic keratitis secondary to herpes zoster or simplex. Neovascularization was encroaching the visual axis in 50% and was paracentral in 42.8%. After intrastromal bevacizumab injection, 14.2% had complete regression of neovascularization, avoiding the need of future corneal transplant. Persistent neovascularization was noticed in 21.4%. Successful penetrating keratoplasty was performed in 57% of patients. Minimal adverse effects were noted; temporary epithelial defect was seen in two eyes and self-limited intrastromal hemorrhage in one. There was no evidence of recurrence of neovascularization or graft rejection in the transplant group (mean follow-up 3 years).

CONCLUSION

Intrastromal bevacizumab appears to be a safe and effective modality in the treatment of chronic corneal neovascularization, producing durable regression of corneal neovascularization and allowing for durable success of subsequent corneal transplants in high-risk patients.

Revascularization after angiogenesis inhibition favors new sprouting over abandoned vessel reuse

Inhibiting pathologic angiogenesis can halt disease progression, but such inhibition may offer only a temporary benefit, followed by tissue revascularization after treatment stoppage. This revascularization, however, occurs by largely unknown phenotypic changes in pathologic vessels. To investigate the dynamics of vessel reconfiguration during revascularization, we developed a model of reversible murine corneal angiogenesis permitting longitudinal examination of the same vasculature. Following 30 days of angiogenesis inhibition, two types of vascular structure were evident: partially regressed persistent vessels that were degenerate and barely functional, and fully regressed, non-functional empty basement membrane sleeves (ebms). While persistent vessels maintained a limited flow and retained collagen IV+ basement membrane, CD31+ endothelial cells (EC), and α-SMA+ pericytes, ebms were acellular and expressed only collagen IV. Upon terminating angiogenesis inhibition, transmission electron microscopy and live imaging revealed that revascularization ensued by a rapid reversal of EC degeneracy in persistent vessels, facilitating their phenotypic normalization, vasodilation, increased flow, and subsequent new angiogenic sprouting. Conversely, ebms were irreversibly sealed from the circulation by excess collagen IV deposition that inhibited EC migration and prevented their reuse. Fully and partially regressed vessels therefore have opposing roles during revascularization, where fully regressed vessels inhibit new sprouting while partially regressed persistent vessels rapidly reactivate and serve as the source of continued pathologic angiogenesis.

Regression of corneal neovascularization: Adiponectin versus bevacizumab eye drops

PURPOSE

Comparing the effect of adiponectin versus bevacizumab in decreasing corneal neovascularization.

METHODS

This study was conducted on 30 eyes of 30 New Zealand Albino male rabbits. Corneal neovascularization was induced by a single 7-0 silk suture 2 mm long and 1 mm in front of the limbus for 2 weeks. Rabbits were randomly divided into three groups of adiponectin (20 µg/mL), bevacizumab (5 mg/mL) and artificial tears. The treatments continued up to 14 days.

RESULTS

At the end of 14 days, the average length of vessels in rabbits treated with adiponectin, bevacizumab and control groups decreased from 2.12 ± 0.32 mm to 0.89 ± 0.46 mm (57.68% ± 19.98%) (P < 0.001), 2.30 ± 0.41 mm to 1.30 ± 0.58 mm (42.49% ± 27.17%) (P = 0.048) and from 2.12 ± 0.44 mm to 1.81 ± 0.42 mm (14.81% ± 5.64%) (P = 0.112), respectively. The length of vessels decreased 57.68% ± 19.98% and 42.49% ± 27.17% in adiponectin versus bevacizumab groups, respectively (P = 0.527). The average surface area of vessels in rabbits treated with adiponectin, bevacizumab and control groups reduced from 5.02 ± 1.50 mm² to 1.40 ± 0.75 mm² (70.64% ± 17.76%) (P < 0.001) 0.34 ± 1.1 mm² to 2.80 ± 1.04 mm² (48.24% ± 19.23%) (P = 0.039) and 5.12 ± 2.92 mm² to 4.4 ± 2.55 mm² (14.68% ± 4.19%) (P = 0.117). Mean surface area of vascularization decreased 70.64% ± 17.76% and 48.24% ± 19.23% in adiponectin versus bevacizumab, respectively (P = 0.013).

CONCLUSIONS

The results of this study suggest that topical adiponectin can decrease recent corneal neovascularization.

Serum vascular endothelial growth factor changes and safety after topical anti-human VEGF antibody bevacizumab in healthy dogs

OBJECTIVE

To evaluate ocular and general safety of topical anti-human VEGF bevacizumab and the effect on serum vascular endothelial growth factor (VEGF) values in healthy dogs.

PROCEDURES

Nine university-owned beagles received 0.05 mL of 0.25% bevacizumab eyedrops (Avastin® , Roche) in one eye and 0.05 mL of 0.9% saline solution in the other eye as a control, administered at 12 hours intervals over a period of 28 days. Continuous monitoring for vital parameters and ocular examinations were conducted. Complete blood counts including hematology and coagulation parameters were performed before trial start as well as 24 hours, 7 days, and 28 days after trial start. Measurements of serum VEGF values were obtained using an ELISA-based approach at days 0, 7, and 28. The experiment was designed as a masked placebo-controlled study.

RESULTS

No clinical signs of ocular toxicity or systemic incompatibility were noted in any dog at any time point of the study. No signs of pain were present in any dog at any time point. All blood count values remained in normal clinical ranges without relevant variation. There was no significant change in mean serum VEGF values between day 0 and day 7 and between day 0 and day 28.

CONCLUSIONS

The results indicate that topical bevacizumab treatment is safe in healthy dogs. However, further studies are needed to assess safety and efficacy in diseased dogs with naturally occurring corneal neovascularization.

In vivo effect of bevacizumab-loaded albumin nanoparticles in the treatment of corneal neovascularization

Corneal neovascularization (CNV) is associated with different ocular pathologies, including infectious keratitis, trachoma or corneal trauma. Pharmacological treatments based on the topical application of anti-VEGF therapies have been shown to be effective in the treatment and prevention of CNV. The aim of this work was to evaluate the effect of bevacizumab-loaded albumin nanoparticles in a rat model of CNV. Bevacizumab-loaded nanoparticles, either "naked" (B-NP) or coated with PEG 35,000 (B-NP-PEG), were administered once a day in the eyes of animals (10 μL, 4 mg/mL every 24 h) during 7 days. Bevacizumab and dexamethasone were employed as controls and administered at the same dose every 12 h. At the end of the study, the area of the eye affected by neovascularization was about 2-times lower for animals treated with B-NP than with free bevacizumab. In the study, dexamethasone did not demonstrate an inhibitory effect on CNV at the employed dose. All of these results were confirmed by histopathological analysis, which clearly showed that eyes treated with nanoparticles displayed lower levels of fibrosis, inflammation and edema. In summary, the encapsulation of bevacizumab in human serum albumin nanoparticles improved its efficacy in an animal model of CNV.

Limiting angiogenesis to modulate scar formation

Angiogenesis, the process of new blood vessel formation from existing blood vessels, is a key aspect of virtually every repair process. During wound healing an extensive, but immature and leaky vascular plexus forms which is subsequently reduced by regression of non-functional vessels. More recent studies indicate that uncontrolled vessel growth or impaired vessel regression as a consequence of an excessive inflammatory response can impair wound healing, resulting in scarring and dysfunction. However, in order to elucidate targetable factors to promote functional tissue regeneration we need to understand the molecular and cellular underpinnings of physiological angiogenesis, ranging from induction to resolution of blood vessels. Especially for avascular tissues (e.g. cornea, tendon, ligament, cartilage, etc.), limiting rather than boosting vessel growth during wound repair potentially is beneficial to restore full tissue function and may result in favourable long-term healing outcomes.

Evolocumab, a proprotein convertase subtilisin/kexin type 9 inhibitor, promotes angiogenesis in vitro

The proprotein convertases family is involved in several physiological processes such as cell growth, migration, and angiogenesis, and also in different pathological conditions. Evolocumab, an inhibitor of proprotein convertase subtilisin/kexin type 9 (PCSK9), has recently been approved for treatment of hypercholesterolemia. This study aimed to investigate the effect of evolocumab on angiogenesis in human umbilical vein endothelial cells (HUVECs). Cell proliferation and migration were evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and Transwell methods. In vitro angiogenesis was assessed by tube formation assay. Vascular endothelial growth factor (VEGF) secretion by HUVECs was also determined using an enzyme-linked immunosorbent assay kit. Evolocumab significantly increased HUVECs viability at 100 μg/mL. Significant enhancement in cell migration, and mean tubules length and size was observed at the concentrations of 10 and 100 μg/mL and also in mean number of junctions at the concentration of 100 μg/mL. Administration of evolocumab at the concentration of 10 μg/mL increased VEGF release into supernatants of HUVECs. Findings of this investigation provided in vitro evidence for pro-angiogenic activity of evolocumab through promoting cell proliferation, migration, tubulogenesis, and VEGF secretion in HUVECs.

MicroRNAs in the cornea: Role and implications for treatment of corneal neovascularization

With no safe and efficient approved therapy available for treating corneal neovascularization, the search for alternative and effective treatments is of great importance. Since the discovery of miRNAs as key regulators of gene expression, knowledge of their function in the eye has expanded continuously, facilitated by high throughput genomic tools such as microarrays and RNA sequencing. Recently, reports have emerged implicating miRNAs in pathological and developmental angiogenesis. This has led to the idea of targeting these regulatory molecules as a therapeutic approach for treating corneal neovascularization. With the growing volume of data generated from high throughput tools applied to study corneal neovascularization, we provide here a focused review of the known miRNAs related to corneal neovascularization, while presenting new experimental data and insights for future research and therapy development.

In-vitro binding analysis of anti-human vascular endothelial growth factor antibodies bevacizumab and aflibercept with canine, feline, and equine vascular endothelial growth factor

PURPOSE

Promising results have been described for antibodies binding vascular endothelial growth factor (VEGF) in patients with corneal neovascularization. Whether veterinary patients would also benefit from this therapeutic approach has not been investigated yet. We examined binding properties of anti-human VEGF antibodies bevacizumab (Avastin®) and aflibercept (Zaltrap®) for canine, feline, and equine VEGF.

METHODS

Human, equine, feline, and canine VEGF were analyzed for sequence similarity using the "Basic Local Alignment Search Tool" (BLAST). Western-blot analysis and ELISA were used to assess binding properties.

RESULTS

BLAST analysis revealed a sequence homology of canine, feline, and equine VEGF to human VEGF-A of 93%, 92%, and 89%, respectively. Western-blot analysis showed immunoreactivity of bevacizumab with human, canine, and feline VEGF, but not with equine VEGF. Aflibercept recognized VEGF of all tested species. ELISA data indicated that bevacizumab and aflibercept bind canine VEGF in a dose-dependent manner. Feline VEGF was bound by bevacizumab and aflibercept in a dose-independent manner. ELISA study further confirmed the lack of bevacizumab binding to equine VEGF, and yielded also a dose-independent binding by aflibercept.

CONCLUSIONS

Bevacizumab and aflibercept turned out to bind VEGF with species-specific differences. Further studies are required to investigate their efficacy and safety under clinical conditions.

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.

Functional Staging of Corneal Neovascularization Using Fluorescein and Indocyanine Green Angiography

Purpose

Corneal neovascularization (CoNV) is a major risk factor for corneal graft rejection and other corneal conditions. The maturity of CoNV is important to guide treatment. This study investigated associations between clinical and angiographic characteristics of CoNV.

Methods

In a prospective cross-sectional study patients with CoNV of variable but known duration and etiology were included. All cases were clinically staged according to a simplified three-grade scale as active, inactive, and regressed and assessed using color photography, anterior-segment optical coherence tomography, and fluorescein and indocyanine green (ICG) angiography. Outcome parameters included age and depth of CoNV, perfusion times and time to leakage of fluorescein and ICG.

Results

Forty eyes of 39 patients with CoNV were included, active (14), inactive (22), and regressed CoNV (4). There were significant associations between the time to fluorescein or ICG leakage and clinical staging of CoNV (R² = 0.24; P = 0.0011, and R² = 0.3; P = 0.0001). In addition, there was a significant association between the time to fluorescein leakage and the age of CoNV (R² = 0.32; P = 0.0002). ICG leakage within 10 minutes was observed significantly more frequently in active than the inactive group and was not observed in regressed cases (P < 0.0001).

Conclusions

Simplification of the staging of CoNV to active, inactive, and regressed to is significantly associated with the time to extravascular leakage of fluorescein and indocyanine and may be useful to guide the selection of appropriate treatments.

Translational Relevance

The association between clinical and angiographic characteristics of CoNV may provide guidance to the treatment approaches.

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 Repeated Intravitreal Aflibercept Injection on the Corneal Endothelium in Patients With Age-Related Macular Degeneration: Outcomes From the RE-VIEW Study

PURPOSE

The effects of repeated intravitreal aflibercept injection (IAI) on the corneal endothelium were studied in patients with unilateral neovascular age-related macular degeneration.

METHODS

RE-VIEW was a phase 4, open-label, single-arm, multicenter study. Patients received IAI every 8 weeks after 3 monthly doses. Slit-lamp biomicroscopy was performed at all study visits. The central corneal endothelial health was evaluated by specular microscopy in the treated versus untreated fellow eyes at baseline and weeks 24 and 52.

RESULTS

No slit-lamp abnormalities were noted in 154 enrolled patients (eyes). Baseline versus 52-week mean (±SD) endothelial morphometric values (n = 118) for the treated versus untreated fellow eyes were respectively as follows: endothelial cell density was 2410 ± 364 versus 2388 ± 384 cells/mm at baseline and remained unchanged at 2401 ± 353 versus 2376 ± 364 cells/mm at 52 weeks (P = 0.87); the coefficient of variation was 33.5 ± 4.4% versus 34.0 ± 5.0% at baseline and remained unchanged at 34.2 ± 4.7% versus 34.1 ± 4.9% at 52 weeks (P = 0.18); the percentage of hexagonal cells was 59.5 ± 5.8% versus 59.6 ± 6.4% at baseline and remained unchanged at 59.5 ± 6.0% versus 59.5 ± 5.8% at 52 weeks (P = 0.96).

CONCLUSIONS

Repeated IAI for 52 weeks had no apparent corneal endothelial toxicity noted on specular microscopy in patients treated for neovascular age-related macular degeneration.

Photokinetic Drug Delivery: Near infrared (NIR) Induced Permeation Enhancement of Bevacizumab, Ranibizumab and Aflibercept through Human Sclera

PURPOSE

Permeation studies, with near infrared (NIR) light and anti-aggregation antibody formulation, were used to investigate the in vitro permeation of bevacizumab, ranibizumab and aflibercept through human sclera.

METHODS

A vertical, spherical Franz cell diffusion apparatus was used for this scleral tissue permeation model. A photokinetic ocular drug delivery (PODD) testing device accommodated the placement of NIR LEDs above the donor chambers. An adjustable LED driver/square wave generator provided electrical energy with a variable pulse rate and pulse width modulation (duty cycle).

RESULTS

Exposure to non-thermal NIR light had no effect on mAbs with regard to monomer concentration or antibody binding potential, as determined by SE-HPLC and ELISA. The optimal LED wavelength was found to be 950 nm. Duty cycle power of 5% vs 20% showed no difference in permeation. When compared to controls, the combination of non-aggregating antibody formulation and NIR illumination provided an average transscleral drug flux enhancement factor of 3X.

CONCLUSION

Narrow wavelength incoherent (non-laser) light from an NIR LED source is not harmful to mAbs and can be used to enhance drug permeation through scleral tissue. The topical formulation, combined with pulsed NIR light irradiation, significantly improved scleral permeation of three anti-VEGF antibody drugs.