Effect Of Collagen Cross-linking On Alkali Burn-induced Corneal Neovascularization In Rabbit

Objective: The aim of this study is to explore the effects and mechanism of CXL on alkali burn-induced corneal neovascularization(CRNV)in rabbit models.Methods: Sixty healthy rabbits were randomly divided into 6 groups and the right eyes were treated.Group A(alkali burn),group B(standard CXL,immediately after alkali burn),group C(CXL,UV exposure for 15 minutes,immediately after alkali burn),group D(CXL,UV exposure for 45 minutes,immediately after alkali burn),group E(standard CXL l,1 days after alkali burn),F group(standard CXL,3 days after alkali burn CXL).The corneal stromal edema,infection,ulcer,corneal neovascularization area were recorded at 4d,7d,10 d,and 14 d after crosslinking.Western-Blotting was used to analyze the expression of VEGF,MMP-2,MMP-9,TIMP-1.Results: 1.Observation of slit lamp after operation:all rabbits were killed on 14 th day,Group A(alkali burn)has 5 eyes(50%)which corneal stromalwere dissolved and the posterior elastic layer were expanded;In experimental group,7 eyes(14%)showed thinning of the central cornea,and 3 eyes(6%)showed corneal dissolution.Corneal perforation was not found in all groups.2.The comparison of corneal neovascularization(CRNV)area:there was no significant difference between all groups(all P>0.05)on 14 th day and a significant difference between the groups on 7th day(all P < 0.05),among which group A was the largest.On the 10 th day,there was a significant difference between group A and group D/E(P < 0.05),the corneal neovascularizationarea area of group D/E are significantly less than group A.On the 14 th day,there were significant differences between group A /B/F and group D(all P < 0.05),among which group D was the smallest.3.The comparison of the expression of VEGF,MMP-2,MMP-9,TIMP-1 which detected by Western-Blotting : on the 7th day after injury,there was no significant difference in the expression of VEGF,MMP-2 between the control group and the experimental group(all P > 0.05),the expression of MMP-9 in group A was significantly lower than the experimental group;meanwhile,the expression of TIMP-1 in group A was significantly lower than that in group D/F.On the 14 th day after injury,the expression of VEGF,MMP-2,MMP-9,and TIMP-1 of the control group all incresed,while the experimental group was the opposite.In this study,the expression of VEGF in group A was significantly higher than the experimental group(all P < 0.05),and the MMP-2 expression in the group A was significantly higher than that of group B/ D/E(all P < 0.05).The expression of MMP-9 and TIMP-1 in group A were higher than the groups,but no significant difference was achieved(all P > 0.05).Conclusion:1.This study further demonstrated that CXL plays a importang role in resisting the dissolution of corneal substrate.2.CXL for 45 minutes can alleviate the formation of CRNV,which may inhibit the growth of CRNV by reducing the expression of VEGF,MMP-2 and MMP-9.