结膜下注射Avastin抑制角膜新生血管的实验研究

目的:观察结膜下注射Avastin对实验性兔眼角膜新生血管(neovascularization,NV)的抑制作用,初步探讨作用机制。方法:应用5mm直径的加样器(末端附有棉片)吸入1mol/LNaOH接触新西兰兔右眼(20眼)中央角膜区烧灼30s,制作碱烧伤兔眼角膜NV模型。将实验兔随机分成2组,10眼(A组)碱烧伤后立即结膜下注射Avastin 2.5mg;其余10眼为对照组(B组),结膜下注射等量生理盐水。烧灼后次日每天裂隙灯观察角膜NV、角膜水肿情况,分别于3,7,14,21,28d裂隙灯照相并计算NV面积及NV抑制率。伤后7,28d各组随即处死5只实验兔,取角膜组织做石蜡切片行组织病理学检查及VEGF免疫组织化学检测。结果:两组兔眼伤后第1d角膜缘血管网明显扩张充血,3d时血管开始侵入角膜,7～14d时NV达到高峰,14～21d后NV稳定并逐渐回退。两组角膜NV长度、NV面积及角膜水肿程度存在差异(P<0.05);A组各时间点角膜NV抑制率为44.2%～55%。A组角膜上皮及实质层水肿较轻,NV较少,后弹力层基本完整,VEGF表达明显弱于B组。结论:结膜下注射Avastin对碱烧伤诱导的兔眼角膜NV形成及生长具有明显的抑制作用,可能通过下调VEGF表达发挥作用。

Study on the inhibitory effect of avastin by subconjunctival injection on corneal neovascularization and its mechanisms

AIM: To test whether subconjunctival injection of avastin could suppress corneal neovascularization induced by alkali injury and study its mechanisms.

METHODS: Alkali injury was induced by application of 1mol/L NaOH to right eyes of New Zealand white rabbits for 30 seconds(n=20). All animals were randomly assigned to A, B groups, each consisting of 10 eyes. Group A received subjunctival injection of avastin after alkali injury immediately in 2.5mg dosage. Group B received subconjuctival injection of normal salt. Biomicroscopic neovascularization was observed on 3, 7, 14, 21 and 28 days. The average length, area and inhibitory rate of corneal neovascularization(CNV)were calculated respectively. Five rabbits were randomly killed in each group on 7 and 28 days and the corneas were taken for histopathological examination.Immunohistochemical studies on the expression of VEGF in corneal paraffin sections were also carried out.

RESULTS:The vessel meshworks of corneal limb were dilated and congested on the 1^st day, then neovascularization(NV)began to invade cornea on 3^rd day, and reached to its developmental peaks between 7 and 14 days, lastly, NV started to regress on 14-21 days after alkali injury. Significant difference(P<0.05)in the area of NV, average length of NV and corneal edema were found respectively between group A and B(P<0.05); the inhibitory rate of CNV ranges from 44.2% to 55% in group A. There were slight epithelium and fiber edema in group A,and disappeared in the late, the fiber arranged straightly and less NV intruded into the central cornea. Immunohistochemical studies indicated that the expression of vascular endothelial growth factor(VEGF)in group A was obvious lower compared to group B on 7 and 28 days.

CONCLUSION:Avastin suppresses corneal neovascu- larization induced by alkali injury on rabbit eyes with subconjunctival injection through decreasing expression of VEGF.