Inhibition of experimental corneal neovascularization by using subconjunctival injection of bevacizumab (Avastin)

Effect of adalimumab on experimental corneal neovascularization model

PURPOSE

To evaluate the efficacy of adalimumab (ADA) on inhibition of experimental corneal neovascularization (CNV) and compare the outcomes with bevacizumab (BEVA).

METHODS

Twenty-four female Winstar rats (48 eyes) were used. Silver/Potassium Nitrate sticks were used for creating CNV. Forty-eight eyes of the rats were separated into 6 groups. The eyes which only NaCl was injected subconjunctivally (SC) formed Group-1. The eyes which CNV was created and NaCl, BEVA (2.5 mg/0.05 mL), ADA (2.5 mg/0.05 mL), respectively, were injected SC formed group-2, 3 and 4. The eyes which only BEVA and ADA, respectively, were injected SC formed group-5 and 6. Five days later the animals were sacrificed. Hematoxylin and eosin staining, Masson trichrome staining, Vascular endothelial growth factor (VEGF), and Platelet-derived growth factor (PDGF) antibodies were performed.

RESULTS

Histochemical results showed that there was no histopathological finding in group-1, 5, and 6. Collagen fiber irregularity was observed in group-2 and there was a significant improvement in collagen fiber irregularity in group-3 and 4. Collagen fiber proliferation was higher in group-2 than in group-3 and 4. VEGF and PDGF stainings were not observed in group-1, 5, and 6. VEGF and PDGF stainings were observed in group-2 and significantly decreased in group-3 and 4 compared to group-2. ADA was found to be superior to BEVA in terms of decreasing VEGF staining.

CONCLUSION

Both BEVA and ADA were effective in inhibiting CNV. Subconjunctival ADA seems to be more effective than BEVA in terms of inhibiting VEGF expression. Further experimental studies about ADA and BEVA are needed.

Pharmacological treatment strategies of pterygium: Drugs, biologics, and novel natural products

Pterygium is a fibrovascular tissue growth invading the cornea. Adjunctive treatment post-surgery includes conventional immunosuppressants as well as antiviral drugs. The use of large- and small-molecule antivascular endothelial growth factor (VEGF) agents remains an integral part of pterygium treatment as well as other neovascular conditions of the eye. Naturally occurring polyphenolic compounds have favorable characteristics for treating neovascular and inflammatory eye conditions, including good efficacy, stability, cost-effectiveness, and the versatility of their chemical synthesis. In this review, we discuss pharmacological treatments of pterygium. Natural products, such curcumin, ellagic acid, and chalcones, are reviewed, with emphasis on their potential as future pterygium treatments.

Corticosteroids in the Management of Infectious Keratitis: A Concise Review

Microbial keratitis is devastating corneal morbidity with a variable spectrum of clinical manifestations depending on the infective etiology. Irrespective of the varied presentation delayed treatment can lead to severe visual impairment resulting from corneal ulceration, possible perforation, and subsequent scarring. Corticosteroids with a potent anti-inflammatory activity reduce host inflammation, thus minimizing resultant scarring while improving ocular symptoms. These potential effects of corticosteroids have been applied widely to treat various corneal diseases ranging from vernal keratoconjunctivitis to dry eye disease. However, antimicrobial therapy remains the mainstay of treatment in microbial keratitis, whereas the use of adjunctive topical corticosteroid therapy remains a matter of debate. Understandably, the use of topical corticosteroids is a double-edged sword with pros and cons in the treatment of microbial keratitis. Herein we review the rationale for and against the use and safety of topical corticosteroids in the treatment of infective keratitis. Important considerations, including type, dose, efficacy, the timing of initiation of corticosteroids, use of concomitant antimicrobial agents, and duration of corticosteroid therapy while prescribing corticosteroids for microbial keratitis, have been discussed. This review intends to provide new insights into the therapeutic utility of steroids as adjunctive treatment of corneal ulcer.

Steroid-eluting contact lenses for corneal and intraocular inflammation

Ocular inflammation is one of the leading causes of blindness worldwide, and steroids in topical ophthalmic solutions (e.g. dexamethasone eye drops) are the mainstay of therapy for ocular inflammation. For many non-infectious ocular inflammatory diseases, such as uveitis, eye drops are administered as often as once every hour. The high frequency of administration coupled with the side effects of eye drops leads to poor adherence for patients. Drug-eluting contact lenses have long been sought as a potentially superior alternative for sustained ocular drug delivery; but loading sufficient drug into contact lenses and control the release of the drug is still a challenge. A dexamethasone releasing contact lens (Dex-Lens) was previously developed by encapsulating a dexamethasone-polymer film within the periphery of a hydrogel-based contact lens. Here, we demonstrate safety and efficacy of the Dex-Lens in rabbit models in the treatment of anterior ocular inflammation. The Dex-Lens delivered drug for 7 days in vivo (rabbit model). In an ocular irritation study (Draize test) with Dex-Lens extracts, no adverse events were observed in normal rabbit eyes. Dex-Lenses effectively inhibited suture-induced corneal neovascularization and inflammation for 7 days and lipopolysaccharide-induced anterior uveitis for 5 days. The efficacy of Dex-Lenses was similar to that of hourly-administered dexamethasone eye drops. In the corneal neovascularization study, substantial corneal edema was observed in rabbit eyes that received no treatment and those that wore a vehicle lens as compared to rabbit eyes that wore the Dex-Lens. Throughout these studies, Dex-Lenses were well tolerated and did not exhibit signs of toxicity. Dexamethasone-eluting contact lenses may be an option for the treatment of ocular inflammation and a platform for ocular drug delivery. STATEMENT OF SIGNIFICANCE: Inflammation of the eye can happen either on the ocular surface (i.e. the cornea) or inside the eye, both of which can result in loss of vision or even blindness. Ocular inflammation is normally treated by steroid eye drops. Depending on the type and severity of inflammation, patients may have to take drops every hour for days at a time. Such severe dosing regimen can lead to patients missing doses. Also, more than 95% drug in an eye drop never goes inside the eye. Here we present a contact lens that release a steroid (dexamethasone) for seven days at a time. It is much more efficient than eye drops and a significant improvement since once worn, the patient will avoid missing doses.

Local delivery of corticosteroids in clinical ophthalmology: A review

Locally administered steroids have a long history in ophthalmology for the treatment of inflammatory conditions. Anterior segment conditions tend to be treated with topical steroids whilst posterior segment conditions generally require periocular, intravitreal or systemic administration for penetration. Over recent decades, the clinical applications of periocular steroid delivery have expanded to a wide range of conditions including macular oedema from retino-vascular conditions. Formulations have been developed with the aim to provide practical, targeted, longer-term and more efficacious therapy whilst minimizing side effects. Herein, we provide a comprehensive overview of the types of periocular steroid delivery, their clinical applications in ophthalmology and their side effects.

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.

Corneal Collagen Cross-Linking With Riboflavin and UVA Regulates Hemangiogenesis and Lymphangiogenesis in Rats

Purpose

The purpose of this study was to determine whether corneal collagen crosslinking (CXL) inhibits hemangiogenesis and lymphangiogenesis during acute corneal inflammation in an in vivo rat model.

Methods

Inflammatory corneal neovascularization was induced by suture placement into a rat cornea. At day 3 after suture, a CXL protocol using riboflavin and UVA was administered after mechanical epithelial debridement. Hemangiogenesis and lymphangiogenesis were analyzed morphometrically. CD45 and CD68 immunostaining evaluated corneal leucocyte and macrophage immune cell infiltration, respectively. A TUNEL assay detected stromal cell apoptosis. Quantitative RT-PCR analysis identified angiogenic and lymphangiogenic genes as well as proinflammatory cytokine expression. Western blot analysis characterized vascular endothelial cell CD31 and lymphatic vessel endothelial hyaluronan receptor (LYVE-1) protein expression.

Results

CXL treatment significantly reduced corneal pathologic suture-induced hemangiogenesis and lymphangiogenesis 7 days after suture emplacement, but this procedure failed to affect hemangiogenesis and lymphangiogenesis 14 days after suture. Increased cell apoptosis and reduced CD45+ and CD68+ cell infiltration were evident in CXL-treated rats on days 7 and 14 after suture emplacement. CXL treatment significantly decreased angiogenic and lymphangiogenic mRNA expression levels and both CD31 and LYVE-1 protein expression levels, whereas it increased proinflammatory cytokine levels on day 7 after suture emplacement. However, on day 14 after corneal neovascularization, angiogenic and lymphangiogenic mRNA gene expression levels were upregulated along with hematic CD31 and lymphatic LYVE-1 protein expression.

Conclusions

CXL treatment only temporarily inhibits corneal inflammatory-associated hemangiogenesis and lymphangiogenesis in vivo. Such insight suggests that future studies are warranted to develop novel CXL strategies with longer-lasting effectiveness in attenuating hemantic- and lymphatic-related corneal diseases.

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.

Prevention of corneal neovascularization by subconjunctival injection of avastin® loaded thermosensitive hydrogels in rabbit model

The antibody avastin® (Ava) has been clinically to treat various intraocular neovascular diseases, but suffering from the rapid clearance and short shelf-life of Ava in the requirement of frequent administration. In the present study, we reports the sustained release of Ava from a thermosensitive hydrogel based on poly(ethylene glycol)-poly(ɛ-caprolactone)-poly(ethylene glycol) (PECE) copolymer for the control of corneal neovascularization in rabbit model. Ava were physically mixed with PECE aqueous solution at 4 °C, and resulting Ava-PECE solution showed a sol-gel transition at physiological temperature (37 °C). In vitro release study indicated that Ava-PECE hydrogel provided a sustained release of Ava up to 28 days and the drug release behavior could be finely modulated by the change of PECE concentration. A single subconjunctival injection of PECE hydrogel hardly caused the change of intraocular pressure and corneal endothelial morphology during the entire study period. Intraocular pharmacokinetic analysis suggested that the Ava-PECE hydrogel provided a relatively higher Ava concentration in cornea over Ava solution up to 14 days. In addition, anti-angiogenic effects of the Ava-PECE hydrogel in a suture-induced corneal neovascularization rabbit model indicated that the Ava-PECE hydrogel treatment exhibited superior anti-angiogenic efficacy over Ava solution treatment by decreasing the area ratio of neovascularization on 17 days. Overall, the proposed Ava-PECE hydrogel acting a sustained drug delivery system might be a promising vehicle for the treatment of corneal neovascularization.

Comparison of the inhibitory effect of different doses of subconjunctival bevacizumab application in an experimental model of corneal neovascularization

AIM

To evaluate the inhibitory effect of subconjunctival bevacizumab as single- and multiple-dose application, and compare their effects on corneal neovascularization in a rat model.

METHODS

Thirty adult Sprague-Dawley rats were used in this experimental study. The central cornea of the rats was cauterized chemically. The rats were randomly enrolled into three groups. All groups received subconjunctival injections. In Group 1 (control group, n=10), 0.05 mL 0.9% NaCl solution was injected on the first day. In Group 2 (single-dose group, n=10), 0.05 mL bevacizumab (1.25 mg) was injected on the first day. In Group 3 (multiple-dose group, n=10), four doses of 0.05 mL bevacizumab (1.25 mg) were injected on the first, third, fifth and seventh day. Slit-lamp examination of all rats was performed at the third and ninth day. Digital images of the corneas were taken and analyzed using image analysis software to calculate corneal neovascularization area. All rats were sacrificed on the tenth day. In corneal sections, the number of blood vessels, state of inflammation and collagen formation was evaluated histopathologically.

RESULTS

In Group 3, corneal edema grades were significantly lower than Group 1 and Group 2 (P=0.02, and P=0.035, respectively). The mean percentage of neovascularized corneal area in Group 3 was significantly lower than Group 2 (P=0.005). On histopathological examination, Group 2 and Group 3 showed significantly less number of blood vessels than Group 1 (P=0.005, and P=0.001, respectively). Additionally, Group 3 showed significantly less number of blood vessels compared to Group 2 (P=0.019). Inflammation and edema grades were significantly lower in Group 3 compared to Group 1 (P=0.001).

CONCLUSION

Subconjunctival bevacizumab injection is effective in inhibition of newly formed corneal neovascularization. The multiple-dose bevacizumab treatment seems to be more effective compared to single-dose treatment.

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.

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.

Comparison of different doses of subconjunctival sunitinib with bevacizumab in the treatment of corneal neovascularization in experimental rats

BACKGROUND

To compare the efficacy of subconjunctival administration of bevacizumab and different doses of sunitinib malate in reducing corneal neovascularization (CNV).

MATERIALS AND METHODS

In this experimental study, central corneal cauterization was created in the right eye of fifty male Sprague-Dawley rats. On day 1 (1 week after cauterization), rats were randomly assigned into five treatment groups. Group control (n = 10) received subconjunctival injection of 0.02 ml of base saline solution. Group 1 (n = 10) received 0.02 ml of bevacizumab (25 mg/ml). Group 2, 3, and 4 (n = 10 for each group) were treated with 0.02 ml of sunitinib malate (10, 20, and 50 μg/ml, respectively). On days 1, 7, and 14, digital photographs of the cornea were taken, and the area of CNV was measured.

RESULTS

During the 2-week follow-up, CNV area in treatment groups was less than in control group (P < 0.05). On day 7, corneal avascular area was highest in Group 3 at 63%. On day 14, the area of CNV in Groups 2 and 3 was less than in Group 1 (P = 0.031 and 0.011, respectively), but the difference between Groups 2 and 3 was not statistically significant (P = 0.552). The decreased CNV area on day 14 in Group 4 was significant in comparison to bevacizumab, but it was not significant on day 7 (P = 0.25 on day 7 and 0.002 on day 14).

CONCLUSION

Subconjunctival sunitinib malate is more effective than bevacizumab in regressing CNV. This effect is more prominent on day 14.

Evaluating the safety of intracameral bevacizumab application using oxidative stress and apoptotic parameters in corneal tissue

AIM

To investigate the possible effects of intracameral bevacizumab on oxidative stress parameters and apoptosis in corneal tissue.

METHODS

In total, 30 rats were assigned randomly into the following three groups of 10 rats each: a sham group (Group 1; n=10), a control group [Group 2; balanced salt solution (BSS) was administered at 0.01 mL; n=10], and a treatment group (Group 3; bevacizumab was administered at 0.25 mg/0.01 mL; n=10). The total antioxidant status (TAS) and the total oxidant status (TOS) in the corneal tissue and blood samples were measured, and the oxidative stress index (OSI) was calculated. Additionally, corneal tissue histopathology was evaluated for caspase-3 and -8 staining and apoptotic activity.

RESULTS

In the blood samples, the TAS, TOS, and OSI levels were not significantly different (all P>0.05). Compared with the sham and control groups, the TOS and OSI levels in the corneal tissues were significantly different in the bevacizumab group (all P<0.05). No statistically significant differences were observed between the sham and control groups (all P>0.05). However, compared with the sham and control groups, greater immunohistochemical staining for caspases-3 and -8 and an elevated level of apoptotic activity were observed in the bevacizumab group.

CONCLUSION

This study revealed that intracameral bevacizumab injections seemed to be systemically safe but may have elicited local toxic effects in the corneal tissue, as indicated by the oxidative stress parameters and histopathological evaluations.

Intrastromal delivery of bevacizumab using microneedles to treat corneal neovascularization

PURPOSE

This study tested the hypothesis that highly targeted intrastromal delivery of bevacizumab using coated microneedles allows dramatic dose sparing compared with subconjunctival and topical delivery for treatment of corneal neovascularization.

METHODS

Stainless steel microneedles 400 μm in length were coated with bevacizumab. A silk suture was placed in the cornea approximately 1 mm from the limbus to induce corneal neovascularization in the eyes of New Zealand white rabbits that were divided into different groups: untreated, microneedle delivery, topical eye drop, and subconjunctival injection of bevacizumab. All drug treatments were initiated 4 days after suture placement and area of neovascularization was measured daily by digital photography for 18 days.

RESULTS

Eyes treated once with 4.4 μg bevacizumab using microneedles reduced neovascularization compared with untreated eyes by 44% (day 18). Eyes treated once with 2500 μg bevacizumab using subconjunctival injection gave similar results to microneedle-treated eyes. Eyes treated once with 4.4 μg subconjunctival bevacizumab showed no significant effect compared with untreated eyes. Eyes treated with 52,500 μg bevacizumab by eye drops three times per day for 14 days reduced the neovascularization area compared with untreated eyes by 6% (day 18), which was significantly less effective than the single microneedle treatment. Visual exam and histological analysis showed no observable effect of microneedle treatment on corneal transparency or microanatomical structure.

CONCLUSIONS

This study shows that microneedles can target drug delivery to corneal stroma in a minimally invasive way and demonstrates effective suppression of corneal neovascularization after suture-induced injury using a much lower dose compared with conventional methods.

Comparative study of ranibizumab and bevacizumab on corneal neovascularization in rabbits

PURPOSE

The aim was to compare the effect of subconjunctival injections of ranibizumab and bevacizumab on corneal neovascularization (NV) in rabbits.

METHODS

NV was induced by placing a suture at the corneal periphery of rabbits (n = 30 eyes). Immediately after suturing, the rabbits were divided into 3 groups and 7 days later administered subconjunctival injections of ranibizumab (Lucentis; 0.5 mg/0.05 mL), bevacizumab (Avastin; 5 mg/0.05 mL), or normal saline (control), respectively. The time-course photographs to measure the area of the corneal NV were obtained on days 7, 10, and 14 after suture placement. Histological examination and immunohistochemical analysis for the vascular endothelial growth factor and CD34 were performed.

RESULTS

Analysis of digital photographs showed that there was less corneal NV in the ranibizumab- and bevacizumab-treated eyes than in the control eyes (P = 0.012, 1-way analysis of variance); however, no significant differences between the ranibizumab- and bevacizumab-treated eyes were seen. In addition, there was less staining for vascular endothelial growth factor and CD34 in the corneas from the ranibizumab-treated eyes and bevacizumab-treated eyes than in the control eyes, and there were no significant differences in the staining intensity between the ranibizumab- and bevacizumab-treated eyes. Subconjunctival ranibizumab and bevacizumab injections were not associated with any complications during observations.

CONCLUSIONS

Subconjunctival administrations of ranibizumab or bevacizumab inhibit corneal NV in rabbits and have equivalent effects on it.

Mechanisms controlling the effects of bevacizumab (avastin) on the inhibition of early but not late formed corneal neovascularization

Purpose

To evaluate the effects and underlying mechanisms of early and late subconjunctival injection of bevacizumab on the inhibition of corneal neovascularization (NV).

Methods

Corneal NV was induced by closed eye contact lens wear followed by a silk suture tarsorrhaphy in rabbits. Weekly subconjunctival injections of bevacizumab (5.0 mg) for 1 month were started immediately (early treatment group) or 1 month after induction of corneal NV with continuous induction (late treatment group). The severity of corneal NV was evaluated. Immunostaining was used to evaluate the intracorneal diffusion of bevacizumab, and the existence of pericytes and smooth muscle cells around the NV. The expression of AM-3K, an anti-macrophage antibody, vascular endothelial growth factor (VEGF) with its receptors (VEGFR1 and VEGFR2), and vascular endothelial apoptosis were also evaluated. Western blot analysis was performed to quantify the expression level of VEGF, VEGFR1 and VEGFR2 on corneal epithelium and stroma in different groups.

Results

Early treatment with bevacizumab inhibited corneal NV more significantly than late treatment. Intracorneal diffusion of bevacizumab was not different among different groups. Immunostaining showed pericytes and smooth muscle cells around newly formed vessels as early as 2 weeks after induction. Immunostaining and Western blot analysis showed that VEGF, VEGFR1, and VEGFR2 on corneal stroma increased significantly in no treatment groups and late treatment groups, but not in early treatment group. Bevacizumab significantly inhibited macrophage infiltration in the early but not late treatment group. Sporadic vascular endothelial apoptosis was found at 4 weeks in the late but not early treatment group.

Conclusions

Early but not late injection of bevacizumab inhibited corneal NV. Late injection of bevacizumab did not alter macrophage infiltration, and can't inhibit the expression of VEGF, VEGFR1, and VEGFR2 on corneal vessels. The inhibition of corneal NV in early treatment group does not occur via vascular endothelial apoptosis.

The effect of subconjunctival ranibizumab on corneal and anterior segment neovascularization: study on an animal model

PURPOSE

To evaluate the effect of subconjunctival anti-vascular endothelial growth factor (VEGF) ranibizumab on corneal and anterior segment neovascularization.

METHODS

In this experimental study and laboratory investigation, chemical cauterization was utilized to induce corneal neovascularization in 16 rabbits randomly divided in 2 equal groups. Cauterized eyes were either treated with 0.1 mL (1 mg) of subconjunctival ranibizumab or administered a sham injection. A third group of 4 rabbits served as control for side effects after ranibizumab administration. All animals were monitored daily for 14 days and the extent of corneal scarring and neovascularization was measured on days 1, 7, and 14. After enucleation, ocular tissues were separated under a surgical microscope and VEGF levels were measured with ELISA. Statistical analysis was performed to compare the extent of corneal neovascularization and VEGF levels between treated and untreated eyes.

RESULTS

Subconjunctival ranibizumab inhibited corneal neovascularization significantly both in the first and the second week compared to untreated controls (p = 0.006 and p = 0.001, respectively). The VEGF levels were significantly lower in all anterior segment tissues like the cornea, iris, aqueous humor, and conjunctiva of the treated eyes (p<0.01). The reduction of VEGF levels ranged from 19% to 73% in different ocular tissues. Corneal scarring was not significantly affected by anti-VEGF treatment (p = 0.7). No side effects were noticed.

CONCLUSIONS

Early subconjunctival administration of ranibizumab may successfully inhibit alkali-induced corneal neovascularization in an animal model. Subconjunctival ranibizumab reduces VEGF levels significantly not only in the cornea and the bulbar conjunctiva but also in the aqueous humor and the iris.

Topically administered bevacizumab had longer standing anti-angiogenic effect than subconjunctivally injected bevacizumab in rat corneal neovacularization

AIM

To compare the effect of topically administered and subconjunctivally injected bevacizumab on experimental corneal neovascularization in rats for two weeks after treatment.

METHODS

Twenty-eight Sprague-Dawley rats were divided into four groups of 7 animals. Each corneal center of right eye was cauterized with silver/potassium nitrate for 8s. After corneal burning, bevacizumab (12.5mg/mL) was topically administered three times per day (TB group) for two weeks or subconjunctivally injected on days 2 and 4 after cauterization (0.02mL; SB group). As negative controls, rats received 0.9% saline topically three times per day (TS group) or subconjunctivally on days 2 and 4 (0.02mL; SS group). Digital photographs of the cornea were taken 1 and 2 weeks after treatment and analyzed to determine the area of cornea covered by neovascularization as the percentage of corneal neovascularization.

RESULTS

One week after treatment, the percentage of corneal neovascularization was significantly lower in the TB and SB groups than in the TS and SS groups (all P<0.05). Two weeks after treatment, the percentage of corneal neovascularization was significantly lower in the TB group than in the TS group (P<0.05). In all groups, the percentage of neovascularization was decreasing as time passed (all P<0.05).

CONCLUSION

Topically administered bevacizumab has longer standing anti-angiogenic effect than subconjunctivally injected bevacizumab in corneal neovascularization following chemical injury in rats.

Cytotoxic properties of sunitinib and sorafenib on human corneal epithelial cells

PURPOSE

To generate toxicology profiles of individual drugs on human corneal epithelial cells (HCEC) and compare their in vitro cytotoxicity.

METHODS

Monolayer cultures of HCEC were harvested from two human donor eyes. Sunitinib (0.3-10 µg/mL) and Sorafenib (0.3-100 µg/mL), diluted in culture medium (CnT-BM.1, CELLnTEC Advanced Cell Systems AG, Bern, Switzerland), 1% Penicillin and 1% Streptomycin were added to cells that were being grown in cell culture dishes. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) was performed 24 hours, three days and five days after incubation. Live/dead viability/cytotoxicity assay (Live/dead assay) was performed and analyzed using fluorescence microscopy after 24 hours of incubation. The expression of p63, ABCG2 and PDGFRβ was evaluated by immunocytochemistry prior to exposure. Cell morphology was assessed with a phase contrast microscope after 24 hours of exposure.

RESULTS

Significant toxicity of Sunitinib was seen at concentrations of >3.3 µg/mL and of Sorafenib at concentrations of >1.0 µg/mL after 24 hours of incubation. Both drugs exhibited increasing toxicities over time. HCEC stained positively for p63, ABCG2 and PDGFRβ. In comparison, the IC50 (inhibitory concentration 50) of Sorafenib was 2.26 times the IC50 of Sunitinib using Live/dead assay after 24 hours and 2.39, 1.29 and 0.78 times the IC50 of Sunitinib using the MTT test after 24 hours, three days and five days, respectively.

CONCLUSIONS

These in vitro experimental findings support the safety of Sunitinib and Sorafenib on HCEC when used at a concentration of <3.3 µg/mL and <1.0 µg/mL, respectively, after 24 hours of exposure. The in vitro cytotoxicity of Sorafenib on HCEC was higher than Sunitinib.

Subconjunctival bevacizumab in the impending recurrent pterygia

The aim of this study is to evaluate the efficacy and safety of subconjunctival bevacizumab injection(s) in the treatment of impending recurrent pterygia. Twenty-three eyes of 23 patients who developed impending recurrence after pterygium surgery with conjunctival autografting and were treated with subconjunctival bevacizumab injection(s) (2.5 mg/0.1 mL) were included in the study. Anterior segment photographs were taken prior to and at 1 week, 1, 3 and 6 months after the injection, and at the end of the follow-up period. Image analysis was performed using an image processing and analysis software program. Recurrence rate and complications were recorded. The mean age and follow-up time of the patients were 51.2 ± 6.2 (31-60 years) and 16.8 ± 3.1 (12-22 months), respectively. The average number of injections was 2 ± 0.78 (1-3). Sixteen eyes required re-injection (two injections in nine eyes, three injections in seven eyes), due to progression of vascularization. There were significant differences between size percentage of lesions before injection and at 1 week, 1, 3 and 6 months after the injection (p < 0.05 for all). Corneal recurrence developed in only one patient and no ocular or systemic side-effects of bevacizumab were observed. Repeated injections of bevacizumab may help to prevent the high recurrence rate of residual impending pterygium, due to its adjuvant role in decreasing lesion size, especially in the first year after surgery.

[Imaging and quantification of corneal neovascularization]

Corneal neovascularization is defined as the invasion of vessels into the normally avascular clear corneal stroma, secondary to acute or chronic tissue injury. In addition to decreasing visual acuity, vascularity introduces circulating immune cells, reducing corneal immune privilege and the graft survival of subsequent keratoplasty. Thus, reducing neovascularization has become a recent therapeutic target in order to increase the success of corneal transplantation. Comparing the effects of antiangiogenic drugs assumes that we are able to quantify corneal neovascularization before and after treatment. In the first part of this literature review, we present the various methods to document neovessels (color photos, fluorescein and indocyanine green anterior segment angiography, in vivo confocal microscopy). Next, we report methods to classify and quantify corneal neovascularization.

Effects of subconjunctivally injected bevacizumab, etanercept, and the combination of both drugs on experimental corneal neovascularization

OBJECTIVE

To compare the effect of subconjunctivally injected bevacizumab, etanercept and the combination of both drugs on experimental corneal neovascularization in rats.

DESIGN

Experimental study.

PARTICIPANTS

28 male Wistar-Albino rats.

METHODS

Right corneas of rats were cauterized by silver nitrate sticks. Rats were divided randomly and equally into 4 groups so that each group contained 7 subjects. Immediately after the cauterization, 0.05 ml normal saline was injected subconjunctivally in group 1 (control group); 0.05 ml (1.25 mg) bevacizumab was injected subconjunctivally in group 2; 0.05 ml (1.25 mg) etanercept was injected subconjunctivally in group 3; 0.05 ml (1.25 mg) bevacizumab and 0.05 ml (1.25 mg) etanercept was injected subconjunctivally in group 4. The rats were euthanized on the 8th day, and digital photographs were obtained before the eyes were enucleated. The area of corneal neovascularization was calculated from digital photographs. Corneal sections were analyzed by histopathologically.

RESULTS

The burn stimulus score was +1 or higher in all eyes. The difference of the neovascularization score between groups was found to be statistically significant (p = 0.001). The area of corneal neovascularization was 79.8% in group 1, 43.2% in group 2, 54.5% in group 3, and 34.8% in group 4. In group 4, corneal neovascularization was inhibited more than in the other groups. Histologic examination showed that the treatment groups had less neovascularization, inflammation, and fibroblast activity than the control group (p< 0.05).

CONCLUSIONS

Our study has shown that etanercept does have some antiangiogenic and anti-inflammatory effects in treatment of corneal neovascularization. The combination of bevacizumab and etanercept may be a promising approach in the treatment of corneal neovascularization.

Inhibition of corneal neovascularization with the combination of bevacizumab and plasmid pigment epithelium-derived factor-synthetic amphiphile INTeraction-18 (p-PEDF-SAINT-18) vector in a rat corneal experimental angiogenesis model

Bevacizumab, a 149-kDa protein, is a recombinant humanized monoclonal antibody to VEGF. PEDF, a 50-kDa glycoprotein, has demonstrated anti-vasopermeability properties. In this study, we demonstrated that the combination of bevacizumab and plasmid pigment epithelium-derived factor-synthetic amphiphile INTeraction-18 (p-PEDF-SAINT-18) has a favorable antiangiogenic effect on corneal NV. Four groups (Group A: 0 μg + 0 μg, B: 0.1 μg + 0.1 μg, C: 1 μg + 1 μg, and D: 10 μg + 10 μg) of bevacizumab + p-PEDF-SAINT-18 were prepared and implanted into the rat subconjunctival substantia propria 1.5 mm from the limbus on the temporal side. Then, 1 μg of p-bFGF-SAINT-18 was prepared and implanted into the rat corneal stroma 1.5 mm from the limbus on the same side. The inhibition of NV was observed and quantified from days 1 to 60. Biomicroscopic examination, western blot analysis and immunohistochemistry were used to analyze the 18-kDa bFGF, 50-kDa PEDF and VEGF protein expression. No inhibition activity for normal limbal vessels was noted. Subconjunctival injection with the combination of bevacizumab and p-PEDF-SAINT-18 successfully inhibited corneal NV. The bFGF and PEDF genes were successfully expressed as shown by western blot analysis, and a mild immune response to HLA-DR was shown by immunohistochemistry. We concluded that the combination of bevacizumab and p-PEDF-SAINT-18 may have more potent and prolonged antiangiogenic effects, making it possible to reduce the frequency of subconjunctival bevacizumab administration combined with a relatively safe profile and low toxicity.

Treatment of pterygium by ligation and bevacizumab injection

PURPOSE

To describe a technique for treating pterygium by combining a subpterygial injection of bevacizumab followed by pterygial ligation.

METHODS

Bevacizumab (1.25 mg/0.05 mL) was injected into the base of pterygia in 4 patients, and the pterygial necks were ligated.

RESULTS

The heads of the pterygia regressed and disappeared within 7 days after treatment. The bodies also partially regressed and well-defined vessels were not seen on the bodies; however, the concentration of microvessels was higher on the pterygial bodies than in the normal conjunctiva after 1 month. A recurrence was defined as fibrovascular growth of conjunctival tissue that extended beyond the limbus. No complications or recurrences were noted during the follow-up period.

CONCLUSIONS

Although only 4 cases were studied, the uniform finding demonstrated that combined subpterygial bevacizumab injection and pterygial ligation is a potential effective procedure for removing pterygium.

The effect of different doses of subconjunctival bevacizumab injection on corneal neovascularization

To evaluate the effects of various doses of subconjunctival bevacizumab injections in the treatment of patients with corneal neovascularization. During the 6-month-follow-up, no significant ocular or systemic adverse events were observed related to the subconjunctival bevacizumab injection. In Group 1, the total area of corneal neovascularization before injection was 14.8 ± 3.2 % of the corneal surface and 10.2 ± 2.8 % 6 months after injection (p < 0.01). The mean decrease in Group 1 was 32.0 ± 3.0 %. In Group 2, the total area of corneal neovascularization before and 6 months after the injection was 14.2 ± 2.5 and 9.8 ± 2.3 %, respectively (p < 0.01). The mean decrease in Group 2 was 31.0 ± 2.3 %. The difference between the two groups was not statistically significant (p > 0.05). Twenty-four eyes of 24 patients with corneal neovascularization who were treated with a subconjunctival injection of bevacizumab were included in this retrospective study. Fourteen eyes were treated with 2.5 mg/0.1 ml (Group 1), and 10 eyes were treated with 5.0 mg/0.2 ml (Group 2) of subconjunctival bevacizumab. Digital photographs of the cornea were used to determine the area of corneal neovascularization before injection and at 1 month, 3 months, and 6 months after treatment. Subconjunctival injection of bevacizumab is well tolerated and associated with a partial regression of corneal neovascularization. The efficacy of this treatment is not correlated to the injection dose.

Effects of subconjunctival ranibizumab in a presensitized rat model of corneal graft

We evaluated whether corneal graft survival in presensitized corneal transplantation was affected by subconjunctival ranibizumab in a rat model. The effect of ranibizumab in the presensitized corneal transplantation has not been previously reported, although anti-VEGF was attempted on a non-presensitized model in other studies. Corneas were transplanted from Brown Norway to Spraque Dawley rats. The recipient rats were randomly assigned to three groups: Group 1, skin autograft and subconjunctival injection of PBS; Group 2, skin allograft and injection of PBS; and Group 3, skin allograft and injection of ranibizumab (vascular endothelial growth factor antibody). A skin graft was performed 2 weeks before corneal transplantation. On days 3, 7, 11, and 14 after transplantation, the grafts were scored. The number of corneas with graft rejection on day 14 was significantly higher in Group 2 than in Group 1 or 3 (6/15 [40.0%] in Group 1, 13/15 [86.7%] in Group 2, and 4/15 [26.7%] in Group 3). The mean clinical scores for edema, opacity, and new vessels in Group 3 were significantly lower than those in Group 2, while the edema score in Group 1 was significantly lower than that in Group 2 on day 14. Before corneal allotransplantation, presensitization by skin grafting accelerated the graft rejection process. In a short-term presensitized rat model of keratoplasty, application of subconjunctival ranibizumab prevented graft rejection.

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.

Ocular distribution, spectrum of activity, and in vivo viral neutralization of a fully humanized anti-herpes simplex virus IgG Fab fragment following topical application

Herpes simplex ocular infection is a major cause of corneal blindness. Local antiviral treatments exist but are associated with corneal toxicity, and resistance has become an issue. We evaluated the biodistribution and efficacy of a humanized anti-herpes simplex virus (anti-HSV) IgG FAb fragment (AC-8; 53 kDa) following repeated topical administration. AC-8 was found in the corneal epithelium, anterior stroma, subepithelial stromal cells, and retinal glial cells, with preferential entry through the ocular limbus. AC-8 was active against 13 different strains of HSV-1, with 50% and 90% mean effective concentrations (MEC(50) and MEC(90), respectively) ranging from 0.03 to 0.13 μg/ml, indicating broad-spectrum activity. The in vivo efficacy of AC-8 was evaluated in a mouse model of herpes-induced ocular disease. Treatment with low-dose AC-8 (1 mg/ml) slightly reduced the ocular disease scores. A greater reduction of the disease scores was observed in the 10-mg/ml AC-8-treated group, but not as much as with trifluridine (TFT). AC-8 treatment reduced viral titers but less than trifluridine. AC-8 did not display any toxicity to the cornea or other structures in the eye. In summary, topical instillation of an anti-HSV FAb can be used on both intact and ulcerated corneas. It is well tolerated and does not alter reepithelialization. Further studies to improve the antiviral effect are needed for AC-8 to be considered for therapeutic use.

Corneal penetration of topical and subconjunctival bevacizumab

PURPOSE

To investigate the ability of bevacizumab to penetrate the cornea after topical application or subconjunctival injection.

METHODS

Bevacizumab 1% was topically applied three times a day to the corneas of mice (BALB/c) with intact corneas (n = 14), and with corneal neovascularization (n = 14). Animals were euthanized at 1, 6, 12, and 24 hours, and 2, 4, and 7 days for immunohistochemical analyses. Donkey anti-human IgG labeled with Cy3 was used for bevacizumab immunoreactivity detection. Additionally, one-time topical bevacizumab 1% was tested in corneas with denuded epithelium (n = 16). In another group (n = 16), a single dose of 0.5 mg bevacizumab was injected subconjunctivally. Animals were euthanized at 1, 6, and 24 hours, and 2, 4, 7, 14, and 21 days for immunohistochemical studies.

RESULTS

Bevacizumab was barely detected beyond the very superficial layer of the corneal epithelium in mice with intact corneas even after 7 days of topical administration. Application of bevacizumab in mice with corneal neovascularization; however, showed variable penetration into the corneal stroma. Experimentation with single application of topical bevacizumab in corneas with denuded epithelium or subconjunctivally injected bevacizumab showed intense staining for bevacizumab.

CONCLUSIONS

Topically applied bevacizumab has limited capacity to penetrate the corneas with intact epithelium. However, bevacizumab can penetrate the neovascularized cornea after topical application. This study demonstrates that subconjunctivally injected bevacizumab in eyes with an intact cornea penetrates well into the corneal stroma.

Treatments for corneal neovascularization: a review

Corneal neovascularization (CNV) may be a physiological response to various stimuli, but a chronic and persistent upregulation of neoangiogenesis can result in pathological CNV. Pathological blood vessels are immature and lack structural integrity, predisposing the cornea to lipid exudation, inflammation, and scarring. CNV can therefore become a potentially blinding condition. In this review, we frame CNV in an epidemiological perspective, consider risk factors for CNV, provide an overview of CNV pathogenesis, and consider the impact of CNV on corneal transplantation. We consider treatments that are of largely historical interest, before reviewing contemporary medical and surgical treatments. Within medical treatments, we report on steroids, nonsteroidal anti-inflammatory agents, antivascular endothelial growth factor agents, and cyclosporine. Within surgical treatments, we report on the use of lasers, photodynamic therapy, superficial keratectomy, and diathermy/cautery-based treatments.

Topical dihydroartemisinin inhibits suture-induced neovascularization in rat corneas through ERK1/2 and p38 pathways

AIM

To determine if topical instillation of dihydroartemisinin (DHA) inhibits corneal neovascularization (NV) in rats and to investigate the role of the extracellular regulated kinases (ERK) 1/2 and p38 pathways in this process.

METHODS

Suture-induced corneal NV was produced in rats and the eyes were topically treated with different concentrations of DHA (20mg/L, 10mg/L or 5mg/L) or normal saline 4 times a day for 7 days. The corneal NV was quantified as the proportion of NV area to the whole cornea. Western blot was used to determine the expressions of vascular endothelial growth factor (VEGF) and the phosphorylation status of VEGF receptor-2, ERK1/2 and p38 in the corneas. Immunofluorescent staining was used to determine the expressions of phospho-ERK1/2 and phospho-p38 in the corneal tissues from the eyes treated with 20 mg/L DHA (DHA group) or normal saline (control group).

RESULTS

The proportion of corneal NV area in the eyes treated with normal saline or DHA at dosages of 20mg/L, 10mg/L or 5mg/L was (23.74±3.00)%, (15.73±2.88)%, (19.53±2.42)%, and (23.38±2.79)%, respectively. In the eyes treated with 20mg/L or 10mg/L DHA, the corneal NV area was significantly reduced when compared to that in eyes with normal saline (P<0.05). Western blot analyses revealed that 20mg/L DHA significantly inhibited the expressions of VEGF and phospho-VEGFR-2. Both 20mg/L and 10mg/L DHA inhibited the expressions of phospho-ERK1/2 and phospho-p38. Immunofluorescent staining further demonstrated that 20mg/L DHA lowered the expression levels of phospho-ERK1/2 and phospho-p38 in the corneas with suture-induced NV.

CONCLUSION

Suture-induced NV in rat corneas was significantly inhibited by topical treatment with 20mg/L and 10mg/L DHA. The results suggest that the effects could be partially dependent on the DHA-mediated inhibitions of the ERK1/2 and p38 pathways.

Prevention of corneal neovascularization: comparison of different doses of subconjunctival bevacizumab with its topical form in experimental rats

BACKGROUND

To compare the effect of different dosages of subconjunctival bevacizumab with its topical administration on preventing the development of corneal neovascularization (CNV) in a rat model of corneal chemical injury.

METHODS

Neovascularization was induced by pressing a 2-mm diameter alkaline-coated applicator on the central cornea of the right eye of 50 anesthetized male rats. Immediately after cauterization, rats were divided randomly into 5 groups. Groups 1-4 received a subconjunctival injection of 0.02 ml of normal saline (control) or 1, 5 and 25 mg/ml of bevacizumab, respectively. In the fifth group, topical bevacizumab was instilled daily for 7 consecutive days. After 7 days, digital photographs of the cornea were taken and the area of the neovascularized cornea was calculated.

RESULTS

Analysis of digital photographs showed that, compared with the controls, a single subconjunctival injection of at least 0.1 mg of bevacizumab (5 mg/ml) - immediately after corneal cauterization - effectively decreased CNV after 7 days. Injection of 25 mg/ml of bevacizumab in the fourth group increased the avascular area more than twofold, compared with the saline-treated group (32.2% compared with 15%, p < 0.001). This difference between groups 4 and 2 was statistically significant (p = 0.04). Although topical delivery of 25 mg/ml bevacizumab was effective to inhibit CNV (p = 0.004), the results were similar to those of the third group. Qualitative microscopic evaluation of the cornea was compatible with the gross findings, as bevacizumab-treated groups had less intense corneal vessel channels and inflammation.

CONCLUSION

Both subconjunctival and topical bevacizumab can prevent CNV in rats.

The inhibitory effect of different concentrations of topical bevacizumab on corneal neovascularization

PURPOSE

This study aimed to evaluate the effects of different concentrations of topically administered bevacizumab (Avastin) on experimental corneal neovascularization (NV) in rats.

METHODS

  Corneal NV was induced by chemical cauterization with silver nitrate sticks applied to the centre of the corneas of 37 Wistar rats. The rats were then randomized to four topical treatment groups: group 1 (n = 10) received 4 mg/ml bevacizumab; group 2 (n = 9) received 2 mg/ml bevacizumab; group 3 (n = 10) received 1 mg/ml bevacizumab, and group 4 (n=8) represented a control group and received saline. All drops were initiated immediately after cauterization and applied twice per day for 7 days. Corneal NV was assessed 8 days after cauterization in a masked fashion, both qualitatively by clinical evaluation and quantitatively by blood vessel count in photographs of histological sections.

RESULTS

 On clinical evaluation, groups 1 and 2 showed significantly less NV compared with the saline-treated control group (p = 0.006 and p = 0.024, respectively). Histopathological evaluation showed that only group 1 differed significantly from controls (5% significance level) and normal corneal epithelium was seen in all groups.

CONCLUSIONS

  Topically administered bevacizumab at a concentration of 4 mg/ml significantly reduces corneal NV according to both clinical and histopathological evaluations; lower concentrations were less effective on both parameters. No corneal epitheliopathy was found using these concentrations.

Inhibition of corneal neovascularization by topical bevacizumab (Anti-VEGF) and Sunitinib (Anti-VEGF and Anti-PDGF) in an animal model

PURPOSE

To evaluate the effects of topically applied bevacizumab and sunitinib on experimentally induced corneal neovascularization.

DESIGN

Experimental animal study.

METHODS

Thirty-six New Zealand rabbits were involved. One eye per rabbit was used. Corneal neovascularization was induced by placing 5 silk sutures in the upper cornea. Rabbits were randomized to 1 of 3 groups (12 rabbits each): Group 1 received saline 0.9%, Group 2 bevacizumab 5 mg/mL, and Group 3 sunitinib 0.5 mg/mL. All treatments were administered 3 times daily for 14 days. Photographs were taken on a slit lamp on days 7 and 14, and angiographic photographs were taken on day 14. The area of neovascularization was measured in mm(2), percentage of the total corneal area, and percentage of the corneal surface covered by sutures.

RESULTS

On day 14, corneal neovascularization area in Group 1 (25.92 ± 5.08 mm(2), 18.78% ± 3.5% of corneal surface, 105.59% ± 18.9% of corneal surface with sutures) was larger than in Groups 2 (18.52 ± 7.94 mm(2), 13.67% ± 5.8%, 76.35% ± 33.2%) (1-way analysis of variance, P = .041) and 3 (4.57 ± 2.32 mm(2), 3.40% ± 1.7%, 18.94% ± 9.2%)(P < .001). Neovascularization in Group 2 was larger than in Group 3 (P < .001). Compared to saline, corneal neovascularization was inhibited 28.5% by bevacizumab and 82.3% by sunitinib. Sunitinib settled on the iris.

CONCLUSIONS

Topical administration of both bevacizumab and sunitinib inhibits corneal neovascularization in rabbits. But vascular endothelial growth factor (VEGF) pathway blockade by bevacizumab was not sufficient for a profound inhibition. Blocking both VEGF and platelet-derived growth factor pathways using sunitinib was 3-fold more effective.

Corneal graft surgery combined with subconjunctival bevacizumab (avastin)

PURPOSE

To describe the use of subconjunctival bevacizumab (Avastin) as an adjunctive treatment in a vascularized cornea at the time of lamellar keratoplasty to reduce the risk of graft rejection.

MATERIALS AND METHODS

After a significant ocular high-velocity thermal injury, a patient developed extensive corneal scarring and a traumatic cataract. To improve vision, a corneal graft was indicated, but the presence of extensive neovascularization increased the risk of early graft rejection.

RESULTS

Bevacizumab was injected subconjunctivally before surgery to reduce the corneal vessel load. There was a dramatic response in terms of vessel regression, but this was short lived and the vessels quickly regrew. The subconjunctival bevacizumab injection was repeated at the time of combined cataract extraction and lamellar corneal graft surgery, and the feeder vessels were cauterized at the limbus. After 6 months, the graft remained clear of vessels.

CONCLUSIONS

This case is of interest because the eye was treated twice with subconjunctival bevacizumab with good short-term results in both instances but different longer-term outcomes in terms of vessel regrowth. This case suggests that the antiangiogenic effects of bevacizumab may be effectively harnessed at the time of a definitive surgical procedure, which reduces the stimulus for vessel regrowth.

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

PURPOSE

This study sought to evaluate the efficacy of bevacizumab (Avastin), an anti-VEGF agent, in the reduction of corneal neovascularization in a rodent model, and compare between the effect of intraocular and subconjunctival injection.

METHODS

Corneal neovascularization was induced by application of a mixture of 75% silver nitrate and 25% potassium nitrate to the corneal center of the right eye of 125 mice. Immediately thereafter, 75 eyes were treated with subconjunctival, anterior chamber, or intravitreal injection of bevacizumab. The remaining mice served as a control. The groups were compared at different postoperative time points for percentage area of neovascularization evaluated by digital photos, the presence of corneal stromal vascular endothelial cells studied by immunohistochemical staining, and VEGF levels measured by real-time PCR.

RESULTS

In the untreated eyes, percentage area of neovascularization increased from 11.3 +/- 7% on day 2 to 20 +/- 8.9% on day 4, 47 +/- 25.4% on day 8, and 51 +/- 24.7% on day 10. The percentage area of neovascularization following subconjunctival injection was 7 +/- 2.9% on day 2, 15.7 +/- 6% on day 4, 32.2 +/- 15.2% on day 8, and 39.7 +/- 14.5% on day 10. The percentage area of neovascularization following anterior chamber injection was 14.4 +/- 3% on day 2, 16.5 +/- 6.3% on day 4, 26.3 +/- 6.5% on day 8, and 19.8 +/- 1.2% on day 10. The percentage area of neovascularization following intravitreal injection was 11 +/- 2.5% on day 2, 14.7 +/- 5% on day 4, 23.5 +/- 6.5% on day 8, and 24.2 +/- 14.9% on day 10.

CONCLUSIONS

Bevacizumab injections partially inhibit the growth of corneal neovascularization induced by acute chemical injury in a mouse model. The intraocular routes of injection were found to be the most effective, and the subconjunctival route of injection yielded the earliest peak response.

Secreted frizzled-related protein 4: an angiogenesis inhibitor

Wnt signaling is involved in developmental processes, cell proliferation, and cell migration. Secreted frizzled-related protein 4 (sFRP4) has been demonstrated to be a Wnt antagonist; however, its effects on endothelial cell migration and angiogenesis have not yet been reported. Using various in vitro assays, we show that sFRP4 inhibits endothelial cell migration and the development of sprouts and pseudopodia as well as disrupts the stability of endothelial rings in addition to inhibiting proliferation. sFRP4 interfered with endothelial cell functions by antagonizing the canonical Wnt/beta-catenin signaling pathway and the Wnt/planar cell polarity pathway. Furthermore, sFRP4 blocked the effect of vascular endothelial growth factor on endothelial cells. sFRP4 also selectively induced apoptotic events in endothelial cells by increasing cellular levels of reactive oxygen species. In vivo assays demonstrated a reduction in vascularity after sFRP4 treatment. Most importantly, sFRP4 restricted tumor growth in mice by interfering with endothelial cell function. The data demonstrate sFRP4 to be a potent angiogenesis inhibitor that warrants further investigation as a therapeutic agent in the control of angiogenesis-associated pathology.

Effects of topical and subconjunctival bevacizumab in high-risk corneal transplant survival

PURPOSE

To investigate whether corneal graft survival could be improved by topical or subconjunctival bevacizumab in a murine model of vascularized high-risk corneal transplantation.

METHODS

Before corneal transplantation, intrastromal sutures were placed for 2 weeks in the corneas of BALB/c mice, inducing intense angiogenesis. Allogeneic corneal transplantation was performed using C57BL/6 donor mice. Topical bevacizumab (2.5%) was delivered 3 times a day for 3 weeks in one treatment group, and 0.02 mL (0.5 mg) bevacizumab was injected subconjunctivally at days 0, 4, 8, and 15 after transplantation in the other treatment group. The control group received no treatment. Grafts were examined twice a week for 8 weeks by slit-lamp microscopy and were photographed once a week by slit-lamp digital camera and scored for opacity. For assessment of corneal neovascularization (NV), a quantitative method was used to measure three primary metrics including neovascular area, vessel caliber, and neovessel invasion area.

RESULTS

Both topical and subconjunctival bevacizumab treatment reduced neovascular area and vessel caliber; however, the regression of corneal NV was more profound when treated subconjunctivally. The mean percentage reduction of neovascular area was 55% (P < 0.05) by week 8 in the subconjunctival treatment group and 33% (P = 0.15) in the topical group. Only subconjunctival bevacizumab treatment resulted in significant regression of neovessel invasion area (P < 0.05). All corneal transplants in both the control and the topical groups were rejected by 4 weeks after transplantation. However, in the subconjunctival treatment group, 33% of corneal grafts survived (P < 0.01).

CONCLUSIONS

Subconjunctival bevacizumab may offer an adjunctive measure to conventional therapies in preventing graft rejection in high-risk corneal transplantation.

Anti-VEGF monoclonal antibody-induced regression of corneal neovascularization and inflammation in a rabbit model of herpetic stromal keratitis

BACKGROUND

To determine the efficacy of bevacizumab (Avastin), an anti-VEGF monoclonal antibody, administrated via subconjunctival injection as a corneal anti-angiogenic treatment.

METHODS

Right corneas of rabbits were infected with herpes simplex virus type 1, KOS strain. On day 13 post-infection (p.i.), animals were treated subconjunctivally (sc) with a single 10-microl dose (25 microg/microl) of bevacizumab (group A) or with the same volume of an isotype monoclonal antibody, as negative control (group B). All animals were observed clinically on days 2, 5, 7, 14, 21, and 28 p.i., and two corneas each day were obtained for histological assessment and viral titration.

RESULTS

Viral replication was observed no longer than 5 days after infection. By day 7 a dense neutrophil invasion of the cornea was detected, which significantly increased while herpetic stromal keratitis progressed in severity. Positive outcomes observed following the treatment with bevacizumab, compared to control, included: (1) Total involution of neovascularization, (2) reduction in disease severity, (3) improved corneal translucency, (4) absence of scarring, (5) preservation of corneal thickness, (6) no neutrophil infiltration of the cornea.

CONCLUSIONS

Subconjunctival administration of bevacizumab induced involution of new vessels, abolished inflammatory response, and resulted in return of corneal function. Furthermore, bevacizumab is a novel approach for the treatment of herpetic stromal keratitis.

The Boston Ocular Surface Prosthesis as a novel drug delivery system for bevacizumab

Corneal neovascularization causes deterioration of visual acuity and increases surface irregularities. Various techniques have been employed to help control the progression of corneal neovascularization; bevacizumab is a medication that targets the specific pathway of corneal neovascularization. The Boston Ocular Surface Prosthesis (BOSP) is a large diameter contact lens that aids in maintaining corneal surface integrity and may serve as a delivery system for topical bevacizumab. This paper reviews five patients who were treated with topical bevacizumab in their BOSP. All patients demonstrated improvement in their visual acuity and clinical exam. No adverse reactions were noted.

Subconjunctival gene delivery of the transcription factor GA-binding protein delays corneal neovascularization in a mouse model

Corneal neovascularization can reduce visual acuity. GA-binding protein (GABP) is a transcription factor that regulates the expression of target genes including vascular endothelial growth factor (VEGF) and roundabout4 (Robo4), which participate in pathologic angiogenesis. We assessed whether intraocular injection of the GABP gene affects the growth of new corneal blood vessels in a mouse ocular neovascularization model. Transfection of human GABPalpha and GABPbeta gene (GABPalpha/beta) into human conjunctival epithelial cells resulted in decreased VEGF and Robo4 expression. Three groups of mice underwent chemical and mechanical denudation of the corneal epithelium. Subsequently, two groups were administered subconjunctival injection of lipoplexes carrying plasmid DNA encoding for human GABPalpha/beta or an empty plasmid DNA at 1-week intervals. The third group served as an experimental control. In vivo delivery of human GABPalpha/beta into mouse neovascularized cornea reduced VEGF and Robo4 gene expression. Biomicroscopic examination showed that, at 1 week after one or two injections, GABPalpha/beta-treated eyes had significantly less neovascularized corneal area than did eyes treated with the empty vector. Histologic examination showed significantly less vascularized area and fewer blood vessels in the GABP-treated group at 1 week after injections. However, these angiosuppressive effects were weakened at 2 weeks after injections. Our results indicate that subconjunctival GABP gene delivery delays corneal neovascularization for up to 2 weeks in a mouse model of deliberate corneal injury.

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

OBJECTIVE

To study the safety and efficacy of topical bevacizumab in the treatment of corneal neovascularization (NV).

DESIGN

In a prospective, open-label, noncomparative study, 10 eyes from 10 patients with stable corneal NV were treated with topical bevacizumab, 1.0%, for 3 weeks and followed up for up to 24 weeks.

MAIN OUTCOME MEASURES

The primary safety variables were the occurrence of ocular and systemic adverse events throughout the course of the study. The primary efficacy variables were neovascular area, the area of the corneal vessels themselves; vessel caliber, the mean diameter of the corneal vessels; and invasion area, the fraction of the total corneal area covered by the vessels.

RESULTS

From baseline visit to the last follow-up visit, mean reductions were 47.1% (standard deviation [SD], 36.7%) for neovascular area, 54.1% (SD, 28.1%) for vessel caliber, and 12.2% (SD, 42.0%) for invasion area. The decreases in neovascular area and vessel caliber were statistically significant (P= .001 and P< .001, respectively). However, changes in invasion area did not achieve statistical significance (P= .19). Visual acuity and central corneal thickness showed no significant changes. Topical bevacizumab was well tolerated with no adverse events.

CONCLUSIONS

Short-term topical bevacizumab therapy reduces the severity of corneal NV without local or systemic adverse effects.

APPLICATION TO CLINICAL PRACTICE

Topical bevacizumab provides an alternative therapy in the treatment of stable corneal NV.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00559936.