Inhibitory effect of RGDRGD-endostatin on the expression of vascular endothelial growth factor and its receptor in corneal neovascularization / 中华实验眼科杂志

ABSTRACT

BackgroundEndostatin (ES) is currently the strongest endogenous angiognesis inhibitor,and it can inhibit the occurrence of neovascularization.Various studies demonstrated that the poly RGD sequence can enhance the function of the ES gene.ObjectiveThis study was to evaluate the use of gene therapy of modified ES for alkaline burn-induced corneal neovascularization (CNV).MethodsOne hundred and two clean SD rats were randomly divided into the normal control group,the pCI empty vector group,the pCI-ES group,and the pCI-RGDRGDES group.Corneal neovascularization models were established by placing a piece of 3 mm filter paper with 1 mol/L NaOH at the central cornea for 40 seconds.3 μg of the pCI blank vector,ES-tranfected pCI blank vector,or RGDRGD-ES-transfected pCI vector was injected into the superior bulbar conjunctiva after the alkali burn twice at 1-week intervals.Area of CNV and edema of the cornea in the various groups of rats were examined daily under the slit lamp biomicroscope.1,4,7 and 14 days after operation,the rats were sacrificed by the excessive anesthesia method and corneal tissues were obtained to evaluate pathological changes.The expression of CD34 in vascular endothelial cells was detected by immunochemistry to calculate the corneal neovascular density.The expressions of VEGF mRNA and Flk-1 protein in the corneas were detected by reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis.The use and maintenance of animals followed the Statement of ARVO.Results Seven to fourteen days after corneal alkali-burning,the corneal neovascular area was smaller in the pCI-ES group and pCI-RGDRGD-ES group compared with the normal control group and pCI blank vector group (P＜0.05,P＜0.01 ),and nevascular area in the pCI-RGDRGD-ES group was smaller than that in the pCI-ES group (P＜0.05).The expression level of CD34 was significantly lower in the pCI-ES group and pCI-RGDRGD-ES group than that in the normal control group and pCI blank vector group (P＜0.05,P＜0.01 ),and the expression level of CD34 was further declined in the pCI-RGDRGD-ES group compared with the pCI-ES group (P＜0.05 ).Compared with the normal control group and pCI vector group,the expressions of the Flk-1 protein and VEGF mRNA were decreased in the pCI-ES group and pCI-RGDRGD-ES group on the fourth day after corneal alkali-burning (P＜0.01,P＜0.05 ),and those in the pCI-RGDRGD-ES group were less than the pCI-ES group (P＜ 0.05,P＜ 0.05 ).Conclusions Subconjunctival injection of both ES and modified RGDRGD-ES genes result in significant suppression of CNV in vivo,and modified RGDRGD-ES appears to be more effective than native ES.The main mechanism of ES in inhibiting neovascularization is to downregulate the expression of VEGF and Flk-1.