Effect of subconjunctival and intraocular bevacizumab injections on corneal neovascularization in a mouse model

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.

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.

The effects of subconjunctival bevacizumab, ranibizumab, and aflibercept on corneal neovascularization

PURPOSE

To investigate the effects of subconjunctival bevacizumab, ranibizumab, and aflibercept in an experimental corneal neovascularization model.

MATERIALS AND METHODS

The eyes of 24 rats were chemically cauterized and randomly divided into four groups: bevacizumab group (0.05 mL/1.25 mg bevacizumab), ranibizumab group (0.05 mL/0.5 mg ranibizumab), aflibercept group (0.05 mL/1.25 mg aflibercept), and control group (0.05 mL saline solution). Plasma vascular endothelial growth factor (VEGF) levels were among the major measurement outcomes to assess corneal neovascularization. The collected plasmas were analyzed using the SIGMA RAB0511 Rat VEGF Elisa kit. The PCR technique and VEGF amplification procedures were used for molecular analysis. Each cornea was removed and histologically examined on day 21. Corneal images were evaluated by image analyzer software.

RESULTS

In the post-injection period, the number of major corneal arteries decreased significantly in the injection groups when compared to the control group (p = 0.037), but no statistically significant differences were noted among the injection groups (p > 0.05). The aflibercept group had the lowest area of neovascularization. Immunohistochemical staining revealed substantially lower VEGF percentages in neovascularized arteries of the injection groups than the control group (p = 0.015). In TUNEL staining, the mean TUNEL value (number/1hpf) was substantially greater in the control group than in the injection groups, but the mean TUNEL values were similar between the injection groups (p = 0.019, p > 0.05, respectively). No statistically significant differences were observed between the groups in terms of corneal surface area with increased cellularity, edema, and inflammation (p = 0.263). The mean plasma VEGF concentration in the control group was statistically greater than those in the injection groups (p = 0.001).

CONCLUSION

Subconjunctival bevacizumab, ranibizumab, and aflibercept crossed the blood and seemed to be effective in inhibiting corneal neovascularization without causing epitheliopathy in an experimental rat model compared to the controls. However, no significant results were noted between these three anti-VEGF molecules.

Laquinimod Inhibits Inflammation-Induced Angiogenesis in the Cornea

Background: Inflammation-induced angiogenesis plays a critical role in many eye diseases, and abnormal angiogenesis inhibition is regarded as a therapeutic approach. Here, we examined the effects of laquinimod on inflammatory corneal angiogenesis.

Methods: Mouse model of corneal neovascularization was induced by NaOH. Laquinimod or control vehicle were topically applied to alkali-treated eyes twice a day for 10 days. Corneal neovascularization, infiltrating inflammatory cells, and the levels of chemokines, pro-inflammatory cytokines were assessed. RAW cells and human umbilical vein endothelial cells were used in vitro to further explore the underlying mechanisms of the effects of laquinimod on inflammation-induced angiogenesis.

Results: Topical administration of laquinimod to the injured corneas dramatically inhibited alkali-induced corneal neovascularization and decreased inflammatory cell (such as macrophage) infiltration in a corneal injury mouse model. Laquinimod significantly downregulated the expression of chemokines (monocyte chemotactic protein-1 and macrophage inflammatory protein-1), pro-inflammatory cytokines (interleukin-1β and tumor necrosis factor-alpha), vascular endothelial growth factor, nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 and apoptosis-associated speck-like protein containing C-terminal caspase-recruitment domain adaptor protein in both injured corneas and RAW cells. In vitro, laquinimod also dramatically inhibited the proliferation, migration and tube formation of human umbilical vein endothelial cells.

Conclusion: Laquinimod inhibits inflammation-induced angiogenesis in the cornea. These results suggest that laquinimod is a potential new therapeutic option for corneal neovascularization and other angiogenesis-associated diseases.

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.

FTO regulates ocular angiogenesis via m6A-YTHDF2-dependent mechanism

Pathological ocular angiogenesis commonly results in visual impairment or even blindness. Unveiling the mechanisms of pathological angiogenesis is critical to identify the regulators and develop effective targeted therapies. Here, we used corneal neovascularization (CNV) model to investigate the mechanism of pathological ocular angiogenesis. We show that N⁶-methyladenosine (m⁶A) mRNA demethylation mediated by fat mass- and obesity-associated protein (FTO) could regulate endothelial cell (EC) function and pathological angiogenesis during CNV. FTO levels are increased in neovascularized corneas and ECs under pathological conditions. In vitro silencing of FTO in ECs results in reduced cellular proliferation, migration, and tube formation under both basal and pathological conditions. Furthermore, FTO silencing attenuates suture-induced CNV in vivo. Mechanically, FTO silencing in ECs could increase m⁶A methylation levels in critical pro-angiogenic genes, such as FAK, leading to decreased RNA stability and increased RNA decay through m⁶A reader YTHDF2. Our study demonstrates that FTO regulates pathological ocular angiogenesis by controlling EC function in an m⁶A-YTHDF2-dependent manner.

Comparison of Subconjunctival Aflibercept and Betamethasone for the Treatment of Formed Corneal Neovascularization in a Rabbit Model

AIM

To compare the efficacy of aflibercept (Eylea®), a potent antivascular endothelial growth factor (VEGF) agent, with betamethasone (Celestone®) and placebo for the treatment of formed corneal neovascularization in a rabbit model.

METHODS

A central corneal chemical burn was created in the right eye of 24 New Zealand albino rabbits. Four weeks later, the rabbits were randomly divided into 4 equal groups for subconjunctival injection of aflibercept, betamethasone, aflibercept+ betamethasone, or saline (control). Digital photographs taken at weekly intervals were rated by 2 masked observers for extent, centricity, and density of corneal neovascularization according to a predefined scale. The percentage of corneal surface involved by neovascularization was quantified by image analysis software (Fiji-J). The change in corneal neovascularization from treatment administration (4 weeks after injury) to 4 weeks later (8 weeks after injury) was assessed. The rabbits were then euthanized, and their eyes were enucleated and processed for histopathological and immunofluorescence studies.

RESULTS

There was no significant difference in the change in corneal neovascularization after treatment among the 4 groups according to the digital images (p > 0.15) or histological evaluation with hematoxylin and eosin (p > 0.08). On immunofluorescence assay, a lower VEGF concentration was observed in all treatment groups compared to the control group.

CONCLUSIONS

In this rabbit model, corneal neovascularization induced by chemical burn failed to regress with treatment with aflibercept, betamethasone, or their combination.

Epithelial Membrane Protein-2 (EMP2) Antibody Blockade Reduces Corneal Neovascularization in an In Vivo Model

Purpose

Pathologic corneal neovascularization is a major cause of blindness worldwide, and treatment options are currently limited. VEGF is one of the critical mediators of corneal neovascularization but current anti-VEGF therapies have produced limited results in the cornea. Thus, additional therapeutic agents are needed to enhance the antiangiogenic arsenal. Our group previously demonstrated epithelial membrane protein-2 (EMP2) involvement in pathologic angiogenesis in multiple cancer models including breast cancer and glioblastoma. In this paper, we investigate the efficacy of anti-EMP2 immunotherapy in the prevention of corneal neovascularization.

Methods

An in vivo murine cornea alkali burn model was used to study pathologic neovascularization. A unilateral corneal burn was induced using NaOH, and subconjunctival injection of either anti-EMP2 antibody, control antibody, or sterile saline was performed after corneal burn. Neovascularization was clinically scored at 7 days postalkali burn, and eyes were enucleated for histologic analysis and immunostaining including VEGF, CD31, and CD34 expression.

Results

Anti-EMP2 antibody, compared to control antibody or vehicle, significantly reduced neovascularization as measured by clinical score and central cornea thickness, as well as by histologic reduction of neovascularization, decreased CD34 staining, and decreased CD31 staining. Incubation of corneal limbal cells in vitro with anti-EMP2 blocking antibody significantly decreased EMP2 expression, VEGF expression and secretion, and cell migration.

Conclusions

This work demonstrates the effectiveness of EMP2 as a novel target in pathologic corneal neovascularization in an animal model and supports additional investigation into EMP2 antibody blockade as a potential new therapeutic option.

Therapeutic approaches for corneal neovascularization

Angiogenesis refers to new blood vessels that originate from pre-existing vascular structures. Corneal neovascularization which can lead to compromised visual acuity occurs in a wide variety of corneal pathologies. A large subset of measures has been advocated to prevent and/or treat corneal neovascularization with varying degrees of success. These approaches include topical corticosteroid administration, laser treatment, cautery, and fine needle diathermy. Since the imbalance between proangiogenic agents and antiangiogenic agents primarily mediate the process of corneal neovascularization, recent therapies are intended to disrupt the different steps in the synthesis and actions of proangiogenic factors. These approaches, however, are only partially effective and may lead to several side effects. The aim of this article is to review the most relevant treatments for corneal neovascularization available so far.

Genome-wide expression differences in anti-Vegf and dexamethasone treatment of inflammatory angiogenesis in the rat cornea

Angiogenesis as a pathological process in the eye can lead to blindness. In the cornea, suppression of angiogenesis by anti-VEGF treatment is only partially effective while steroids, although effective in treating inflammation and angiogenesis, have broad activity leading to undesirable side effects. In this study, genome-wide expression was investigated in a suture-induced corneal neovascularization model in rats, to investigate factors differentially targeted by dexamethasone and anti-Vegf. Topical treatment with either rat-specific anti-Vegf, dexamethasone, or normal goat IgG (sham) was given to sutured corneas for 48 hours, after which in vivo imaging, tissue processing for RNA microarray, and immunofluorescence were performed. Dexamethasone suppressed limbal vasodilation (P < 0.01) and genes in PI3K-Akt, focal adhesion, and chemokine signaling pathways more effectively than anti-Vegf. The most differentially expressed genes were confirmed by immunofluorescence, qRTPCR and Western blot. Strong suppression of Reg3g and the inflammatory chemokines Ccl2 and Cxcl5 and activation of classical complement pathway factors C1r, C1s, C2, and C3 occurred with dexamethasone treatment, effects absent with anti-Vegf treatment. The genome-wide results obtained in this study provide numerous potential targets for specific blockade of inflammation and angiogenesis in the cornea not addressed by anti-Vegf treatment, as possible alternatives to broad-acting immunosuppressive therapy.

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.

Efficacy of Subconjunctival Aflibercept Versus Bevacizumab for Prevention of Corneal Neovascularization in a Rat Model

PURPOSE

We aimed to evaluate the efficacy of subconjunctival aflibercept, a vascular endothelial growth factor trap compound, for the treatment of corneal neovascularization in a rat model.

METHODS

Chemical burn was produced in the central cornea of 31 male Sprague-Dawley rats. Animals were randomized to receive treatment with subconjunctival injection of 0.08 mL aflibercept (25 mg/mL), 0.05 mL bevacizumab (25 mg/mL), or 0.05 mL physiologic saline. Corneal neovascularization was evaluated on postinjury days 1, 3, 7, 9, and 13 by corneal photographs. The rats were killed on day 21 and samples were collected for histological and flat-mount immunofluorescence analyses.

RESULTS

In all rats, vascular sprouting began on day 3, reached maximum density on days 7-9, and spontaneously regressed thereafter. Mean burn area in the central cornea comprised ∼15% of the total corneal area. The aflibercept group had a significantly smaller relative area of neovascularization than both control group (P < 0.05, 12.27 ± 9.91, 29.66 ± 9.96 days 7) and bevacizumab group (P < 0.05, 12.27 ± 9.91, 21.27 ± 8.19 days 7 and 15.5 ± 10.25, 32.38 ± 9.44 days 9; Mann-Whitney test). On histological study, hematoxylin and eosin staining revealed blood vessels extending to the central cornea in the control and bevacizumab groups and limited to the periphery in the aflibercept group. Immunofluorescence study with an endothelial marker revealed a smaller area of staining in the aflibercept group.

CONCLUSIONS

Aflibercept effectively inhibits corneal neovascularization in a rat model of chemical burn-induced neovascularization and warrants further study for potential use in humans.

Human IgG1 antibodies suppress angiogenesis in a target-independent manner

Aberrant angiogenesis is implicated in diseases affecting nearly 10% of the world’s population. The most widely used anti-angiogenic drug is bevacizumab, a humanized IgG1 monoclonal antibody that targets human VEGFA. Although bevacizumab does not recognize mouse Vegfa, it inhibits angiogenesis in mice. Here we show bevacizumab suppressed angiogenesis in three mouse models not via Vegfa blockade but rather Fc-mediated signaling through FcγRI (CD64) and c-Cbl, impairing macrophage migration. Other approved humanized or human IgG1 antibodies without mouse targets (adalimumab, alemtuzumab, ofatumumab, omalizumab, palivizumab and tocilizumab), mouse IgG2a, and overexpression of human IgG1-Fc or mouse IgG2a-Fc, also inhibited angiogenesis in wild-type and FcγR humanized mice. This anti-angiogenic effect was abolished by Fcgr1 ablation or knockdown, Fc cleavage, IgG-Fc inhibition, disruption of Fc-FcγR interaction, or elimination of FcRγ-initated signaling. Furthermore, bevacizumab’s Fc region potentiated its anti-angiogenic activity in humanized VEGFA mice. Finally, mice deficient in FcγRI exhibited increased developmental and pathological angiogenesis. These findings reveal an unexpected anti-angiogenic function for FcγRI and a potentially concerning off-target effect of hIgG1 therapies.

NADPH oxidase 2 plays a role in experimental corneal neovascularization

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

Mechanisms of glioma formation: iterative perivascular glioma growth and invasion leads to tumor progression, VEGF-independent vascularization, and resistance to antiangiogenic therapy

As glioma cells infiltrate the brain they become associated with various microanatomic brain structures such as blood vessels, white matter tracts, and brain parenchyma. How these distinct invasion patterns coordinate tumor growth and influence clinical outcomes remain poorly understood. We have investigated how perivascular growth affects glioma growth patterning and response to antiangiogenic therapy within the highly vascularized brain. Orthotopically implanted rodent and human glioma cells are shown to commonly invade and proliferate within brain perivascular space. This form of brain tumor growth and invasion is also shown to characterize de novo generated endogenous mouse brain tumors, biopsies of primary human glioblastoma (GBM), and peripheral cancer metastasis to the human brain. Perivascularly invading brain tumors become vascularized by normal brain microvessels as individual glioma cells use perivascular space as a conduit for tumor invasion. Agent-based computational modeling recapitulated biological perivascular glioma growth without the need for neoangiogenesis. We tested the requirement for neoangiogenesis in perivascular glioma by treating animals with angiogenesis inhibitors bevacizumab and DC101. These inhibitors induced the expected vessel normalization, yet failed to reduce tumor growth or improve survival of mice bearing orthotopic or endogenous gliomas while exacerbating brain tumor invasion. Our results provide compelling experimental evidence in support of the recently described failure of clinically used antiangiogenics to extend the overall survival of human GBM patients.

Ocular delivery of macromolecules

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

Early effects of dexamethasone and anti-VEGF therapy in an inflammatory corneal neovascularization model

Inflammatory angiogenesis is the pathogenic mechanism of various sight-threatening eye diseases, among them corneal neovascularization. Current treatment options include steroids which have undesirable side effects, or anti-VEGF which has only limited efficacy. In an inflammatory environment, however, angiogenesis can be stimulated by numerous factors not directly targeted by anti-VEGF therapy. The aim of this study was to induce corneal inflammation leading to angiogenesis, and investigate the early, differential effects of steroid and anti-VEGF therapy at the cellular, tissue, and gene expression levels. Fifty-two Wistar rats received a single intrastromal corneal suture to induce a controlled inflammatory angiogenic response. Rats were subsequently treated with dexamethasone, rat specific anti-VEGF, or goat IgG (control), topically 4 times daily for 7 days. In vivo confocal microscopy of the cornea was performed longitudinally from 5 h up to 7 d to investigate morphology at the cellular and tissue-level. In vivo photographic vessel analysis and immunohistochemistry were also performed. RT-PCR for VEGF-A, FGF-2, IL-6, TNF-α, CXCL2, CCL2, CCL3 and DLL4 was performed at 24 h, and for VEGF-A, IL-6, TNF-α, FGF-2, CXCL2, CCL2, and CCL3 at 7 days. Early infiltration of CD11b + myeloid cells into the cornea at 5 h post-suture was delayed by both treatments relative to controls; however neither treatment was able to suppress accumulation of myeloid cells at day 2 or 7. Limbal vessel dilation was inhibited at 5 h by both treatments, but only dexamethasone showed sustained effect until day 2. Early macrophage recruitment was also suppressed by dexamethasone (but not by anti-VEGF) until day 2. Dexamethasone furthermore suppressed corneal neovascularization at day 7 by over 90%, whereas suppression by anti-VEGF was 14%. Despite differential suppression of vessel dilation, macrophage recruitment, and vascular invasion, anti-VEGF and dexamethasone both down-regulated VEGF-A and IL-6 expression at 24 h with sustained effect to 7 d. They also both down regulated FGF-2 and TNF-α at 24 h and CCL2 at 7 d. In conclusion, anti-angiogenic treatments influence early, pre-angiogenic tissue activity such as limbal vessel dilation, inflammatory cell infiltration of the stroma, and macrophage recruitment. Importantly, the differential effects of steroids and anti-VEGF treatment in suppressing neovascular growth could not be attributed to differential inhibition of several major angiogenic and inflammatory factors in the early pre-sprouting phase, including IL-6, VEGF-A, FGF-2, TNF-α, CCL2, CCL3, CXCL2, or DLL4.

The effect of bevacizumab versus ranibizumab in the treatment of corneal neovascularization: a preliminary study

Purpose

To compare the short term effects of bevacizumab and ranibizumab injections on the regression of corneal neovascularization (NV).

Methods

Sixteen eyes of 16 patients with corneal NV were randomly assigned for an injection with 2.5 mg of bevacizumab (group 1, n = 8) or 1 mg of ranibizumab (group 2, n = 8) through subconjunctival and intrastromal routes. The patients were prospectively followed-up for one month after the injections. Corneal NV areas, as shown on corneal slit-lamp photographs stored in JPEG format, were calculated using Image J software before the injection, one week after the injection, and one month after the injection. The corneal NV areas were compared before and after the injections.

Results

Seven women and nine men, with an average age of 51 years, presented with corneal NV secondary to herpetic keratitis (7 cases), graft rejection (6), chemical burn (1), pemphigoid (1), and recurrent ulcer (1). In group I, the preoperative corneal NV area (8.75 ± 4.33%) was significantly decreased to 5.62 ± 3.86% one week after the injection and to 6.35 ± 3.02% one month after the injection (p = 0.012, 0.012, respectively). The corneal NV area in group 2 also exhibited a significant change, from 7.37 ± 4.33% to 6.72 ± 4.16% one week after the injection (p = 0.012). However, no significant change was observed one month after the injection. The mean decrease in corneal NV area one month after injection in group 1 (28.4 ± 9.01%) was significantly higher than in group 2 (4.51 ± 11.64%, p = 0.001).

Conclusions

Bevacizumab injection resulted in a more effective and stable regression of corneal NV compared to the ranibizumab injection. The potency and dose of these two drugs for the regression of corneal NV require further investigation.

Anterior segment uses of bevacizumab

PURPOSE OF REVIEW

A significant recent advancement in the treatment of neovascularization of the anterior segment of the eye is the development of antivascular endothelial growth factor (anti-VEGF) therapeutic agents.We present a review of the current knowledge on anti-VEGF therapy with bevacizumab for anterior segment neovascularization.

RECENT FINDINGS

A review of the recent peer-reviewed literature reveals an increasing number of experimental and clinical studies on the use of Avastin in both human and animal eye models. Although the numbers are still relatively small, the evidence suggests that bevacizumab may be effective in the treatment of corneal and iris neovascularization. Its effect on primary and recurrent pterygium is more controversial. In general, achievement of vessels regression is usually partial, and recurrence may occur after cessation of treatment. Response to treatment is affected by the chronicity of vessels, their extent, the cause for blood vessels formation, and the route of administration.

SUMMARY

Effective short-term response together with high patient tolerance to local bevacizumab therapy offer encouraging results for the management of anterior segment neovascular disorders. Although statistically significant regression of vessels has been documented in many studies, the clinical significance of this finding is still a subject of debate.

Bevacizumab diminishes experimental autoimmune encephalomyelitis by inhibiting spinal cord angiogenesis and reducing peripheral T-cell responses

Angiogenesis in the animal model of multiple sclerosis experimental autoimmune encephalomyelitis (EAE) is regulated by vascular endothelial growth factor (VEGF) and angiopoietin-2. We determined whether VEGF blockade with the anti-VEGF monoclonal antibody bevacizumab could inhibit angiogenesis and affect peripheral pathogenic immune responses in EAE. Mice treated with bevacizumab from the time of onset of clinical signs showed reduced clinical and pathologic scores. Bevacizumab suppressed angiogenesis and reduced angiopoietin-2 expression at Day 21 but had no effect on VEGF upregulation at Day 14. Messenger RNA levels for the angiogenesis-related protein CD105 were increased at Day 14. Bevacizumab reduced vascular permeability in the spinal cord at Day 14 and Day 21. In peripheral lymph nodes, it induced retention of CD4-positive T cells and inhibited T-cell proliferation. It also reduced mononuclear cell infiltration into spinal cord and the relative proportion of T cells. Isolated lymphoid cells showed reduced secretion of the T-helper 17 (Th-17) cell cytokine interleukin 17 and the Th-1 cytokine interferon-γ. When bevacizumab was added to naive T cells or to antigen-stimulated T cells from mice with untreated EAE in vitro, it had no effect on proliferation or the secretion of interleukin 17 or interferon-γ. These data indicate that bevacizumab ameliorates vascular and T-cell responses during EAE, but its effects on T cells may be indirect, possibly by suppressing angiogenesis.

Corneal neovascularization: an anti-VEGF therapy review

Corneal neovascularization is a serious condition that can lead to a profound decline in vision. The abnormal vessels block light, cause corneal scarring, compromise visual acuity, and may lead to inflammation and edema. Corneal neovascularization occurs when the balance between angiogenic and antiangiogenic factors is tipped toward angiogenic molecules. Vascular endothelial growth factor (VEGF), one of the most important mediators of angiogenesis, is upregulated during neovascularization. In fact, anti-VEGF agents have efficacy in the treatment of neovascular age-related macular degeneration, diabetic retinopathy, macular edema, neovascular glaucoma, and other neovascular diseases. These same agents have great potential for the treatment of corneal neovascularization. We review some of the most promising anti-VEGF therapies, including bevacizumab, VEGF trap, siRNA, and tyrosine kinase inhibitors.

Anti-VEGF therapy with bevacizumab for anterior segment eye disease

PURPOSE

To review the current literature concerning the use of bevacizumab in treating neovascular disorders affecting the anterior segment ocular structures.

METHODS

The authors reviewed the literature on anti-vascular endothelial growth factor (VEGF) therapy with bevacizumab for various anterior segment neovascular disorders that was indexed in MEDLINE (up to January 2011).

RESULTS

Response to bevacizumab anti-VEGF therapy is variable, based on the amount of scarring, the chronicity and extent of corneal neovascularization, the disease process, and the medication formulation and its route of administration. Anti-VEGF agents are especially effective when administered early, before anatomical changes, such as corneal neovascularization and/or angle closure, are established. Neovascularization can recur if the ischemic or inflammatory process is not reversed, so eyes with long-standing diseases, such as autoimmune disorders that involve ongoing inflammation and VEGF production, seem to be less responsive to bevacizumab anti-VEGF therapy. For established neovascularization, combining anti-VEGF agents with the removal of established vessels may be more effective than anti-VEGF therapy alone. Subconjunctival bevacizumab may be more appropriate for focal, deep, and peripheral neovascularization, whereas diffuse superficial neovascularization with central corneal involvement may be best treated via topical application.

CONCLUSIONS

Besides the widely accepted use of bevacizumab in cancer therapy and chorioretinal neovascularization, the initial, striking, short-term response and patients' high tolerance of local bevacizumab therapy offer encouraging results for the potential role of anti-VEGF agents in treating anterior segment neovascular disorders. Controlled prospective trials are needed to establish the long-term safety, efficacy, and dosing guidelines for the use of anti-VEGF agents in anterior segment neovascularization.

Cellular level characterization of capillary regression in inflammatory angiogenesis using an in vivo corneal model

In this study, we introduce a technique for repeated, microscopic observation of single regressing capillaries in vivo in inflamed murine corneas. Natural capillary regression was initiated by removal of inflammatory stimulus during an active pro-angiogenic phase, while the additional impact of anti-angiogenic treatment with triamcinolone or bevazicumab was investigated. Capillaries regressed naturally within 1 week and treatments did not further enhance the natural regression. Morphologically, early-phase regression was characterized by significant lumen narrowing and a significant reduction in CD11b+ myeloid cell infiltration of the extracellular matrix. By 1 week, vascular remodeling occurred concomitant with CD11b+CD68+KiM2R+ mature macrophage localization on capillary walls. Empty conduits without blood flow, positive for collagen IV and devoid of vascular endothelium and pericytes, were apparent in vivo and by 3 weeks were more numerous than perfused capillaries. By 3 weeks, macrophages aggregated around remaining perfused capillaries and were observed in apposition with degrading capillary segments. Abrupt termination of capillary sprouting in our regression model further revealed vascular endothelial abandonment of sprout tips and perfused capillary loop formation within a single angiogenic sprout, possibly as an intussusceptive response to cessation of the stimulus. Finally, we observed lumen constriction and macrophage localization on capillary walls in vivo in a clinical case of corneal capillary regression that paralleled findings in our murine model.