Effect of exogenous TNF-α on corneal neovascularization induced by alkali burn

Abstract

Objective To explore the effect and mechanism of exogenous TNF-α on corneal neovascularization (CNV) in BALB/c mice injured by alkali burn. Methods ①Fifteen BALB/c mice were burned on central comea of left eye by 1 mol/L NaOH for 40 s combine with epithelial denudation, then divided into 3 groups (5 mice each group): 0.2% sodium hyaluronate control group, 100 μg/ml TNF-α treated group, 500 μg/ml TNF-α treated group. The eye drops were applied twice daily for one week. CNV was observed by ophthalmic microscope. Corneal microvessel densities of each group were detected at day 14 after alkali injury by CD31 immunohistochemical analysis. The effect of recombinant murine TNF-α on alkali injury induced CNV was observed. ②After alkali injury, 20 BALB/c mice were divided into 2 groups (10 mice each group): 0.2% sodium hyaluronate control group, 100 μg/ml TNF-α treated group. The eye drops were applied twice daily. At day 2 and day 4 after injury, 5 randomly selected mice of each group were euthanized, vascular endothelial growth factor (VEGF) expressions in the comeal tissue were detected by RT-PCR. ③ Effect of exogenous TNF-α on macrophage depleted mice. Macrophages were depleted by Cl2MDP-lip. 10 BALB/c mice were divided into 2 groups (5 mice each group): Cl2MDP-lip treated group and PBS-lip control group. After alkali injury, all mice were given 100 μg/ml TNF-α eye drops twice daily for one week. Macroscopic CNV was observed by ophthalmic microscope, and the length and area of CNV on day 14 after injury were evaluated and compared between Cl2MDP-lip experimental and control group. Results ①Corneal microvessel density in 100 μg/ml TNF-α treated group were significantly greater than those in control group (P 0.05). ②The intra-comeal VEGF mRNA expression in the early phase (day 2, day 4) after alkali injury in 100 μg/ml TNF-α treated group were significantly higher compared to those in control group (P<0.05). ③Length and area of CNV in the Cl2MDP-lip group were significantly less than those in control group (P<0.01). Conclusion Exogenous TNF -α can promote the development of alkali injury induced CNV by enhancing intra-comeal VEGF mRNA expression. Macrophage play a critical role in the mechanism of TNF-α promote alkali injury induced CNV. Key words: Corneal neovascularization; Tumor necrosis factor α; Vascular endothelial growth factors; Macrophage; Burns, alkali