Comparison of the effects of subconjunctival and topical anti-VEGF therapy (bevacizumab) on experimental corneal neovascularization

Abstract

Purpose: To compare the effects of bevacizumab applied either subconjunctivally or topically, in a rat model of corneal neovascularization induced by alkali burn. Methods: The right corneas of 24 Wistar-Albino rats were cauterized with silver nitrate sticks. The rats were divided randomly and equally into three groups: no treatment control (n=8), subconjunctival bevacizumab treatment (n=8), and topical bevacizumab treatment (n=8). Immediately following cauterization, the subconjunctival group was treated with a 0.05 ml (1.25 mg) bevacizumab subconjunctival injection. The topical group was treated with 10 mg/ml bevacizumab twice daily, and the control group received subconjunctival saline injections twice daily. The burn stimulus and neovascularization scores were evaluated using a technique previously described by Mahoney and Waterbury. Digital photographs were obtained before the eyes were enucleated and corneal sections were then analyzed by histopathology. Results: The mean burn stimulus score was 1.86 ± 0.6 and there was no statistical difference between the groups (p=0.730). The mean neovascularization scores in the subconjunctival and topical bevacizumab groups were statistically lower than the control group (p<0.05). The mean percentage area of corneal neovascularization was 82.5 ± 22.1 in the control group, 42.7 ± 15.0 in the subconjunctival group, and 55.8 ± 18.2 in the topical group. The differences between the control and treatment groups were statistically significant (p<0.05). Histopathology showed that the treatment groups presented less neovascularization, inflammation, and fibroblast activity than the control group (p<0.05). Conclusions: This study demonstrates that both subconjunctival and topical administrations of bevacizumab inhibit corneal neovascularization and decrease inflammation and fibroblast activity in a rat model of corneal neovascularization induced by alkali burn.

Corneal angiogenesis based on different protocols of alkaline cauterization in murine models

“…The alkaline cauterization produced in corneas in this study leads to a timely inflammatory response 8,[11][12][13][14][15][16] , where the release of chemokines recruits leukocytes that produce angiogenic factors, such as the vascular endothelial growth factor, the fibroblast growth factor 2 and the tumor necrosis factor, among others. These growth factors attract endothelial cells, smooth muscle cells, fibroblasts, leukocytes, and platelets, triggering the process of neovascularization 26 .…”

“…In the USA, some biomedical laboratories sell disposable sticks coated with silver nitrate and potassium nitrate, suitable for corneal cauterization 14,16 . In Brazil, these sticks are not easily found, and need to be imported.…”

“…In the literature, corneal cauterization times with alkali using a combination of 75% silver and 25% potassium nitrate range from 8 to 60 seconds 8,[11][12][13][14][15][16] . The cauterizing instrument is usually a stick or filter paper, whose diameter ranges from 1.8 mm to 5 mm 8,[11][12][13][14][15][16] .…”

Therapeutic Effects of Extracts from Spirulina platensis versus Bevacizumab on Inflammation-Associated Corneal Neovascularization

“…CorNVs, as assessed immunohistochemically for vascular endothelial growth factor, was significantly lower in treated groups compared to untreated one, as CorNV is a significant sight-threatening event that usually leads to loss of central vision or even results in blindness [19].…”

“…Preparation of polysaccharide extract from Spirulina platensis (PSP): PSP was prepared as described previously [19]. In brief, dry powder of was incubated with 95% (V/V) ethanol overnight, torrefied, and re-incubated in NaOH (pH 10.0) solution at 80 for 4-6 hours, then centrifuged and collected the supernatant, adjusted pH to 7.0, precipitated with 5% trichloracetic acid (TCA) at 4 overnight, centrifuged and collected the supernatant, then precipitated with 5% TCA for another 3 hours, centrifuged and the supernatant was precipitated with ethanol (1/5:V/V) at 4 overnight.…”