Experimental Studies On Corneal Neovascularization Following Corneal Burns With Alkali

Several corneal disorders including corneal chemical burns, thermal burns, infections and immunologic diseases can induce corneal neovascularization(CNV). Although CNV have some effects on infection removal, wound healing and suppression of corneal solve, it can destroy corneal normal microenvironment. lead to the loss of the immunologic privilege of the cornea and is the high-risk factor for corneal graft rejection. Besides, the structure of new vessels is fragile and more easily leak. CNV remains a severely disabling condition and results in visual impairment because of hemorrhage, exudation and secondary fibrosis. Recently there are many hypothesis about the pathogenesis of CNV such as corneal edema, hypoxia. disbalance between angiogenesis factor and antiangiogenesis factor, infiltration of inflammatory cells. Although there are so many hypothesis, its actual pathogenesis is still unknown.So the study on pathogenesis of CNV is significant. Based on the current study on CNV, we make a systemic research on its histopathology and pathogenesis, which is divided into three parts.Part â…  Changes of rat corneal histopathology at different stages after alkali burnsObjective: To observe the changes of rat corneal histopathology at different stages after alkali burns. Methods: Thirty Wistar rats with alkali burned eyes were randomly divided into six groups.The corneal structure at different stages after alkali burns is observed by light microscopy after HE staining. Results: At 6 hours after alkali burns an obvious acute inflammatory response as evidenced by infiltration of neutrophils had already occurred in the pericorneal limbal area. The vascular sprouts appeared 2 days after alkali burns.At 4 days after alkali burns infiltration of inflammatory cells was more serious and vascular sprouts were observed in the corneal stroma. At 7 days after alkali burns infiltration of inflammatory cells was also serious;ripe and functional new vessels increased in the corneal stroma. At 14 days after alkali burns infiltration of inflammatory cells lightened;ripe and functional new vessels decreased in the corneal stroma.Conclusions: CNV induced by rat corneal burns with alkali is the ideal model for study of the pathogenesis and treatment of inflammatory CNV.There is the participation and aninductive action of inflammatory cells,especially neutrophils, in the pathogenesis of CNV.Part II The immunohistochemical study on hepatocyte growth factor and vascular endothelial growth factor in rat cornea after alkali burnsObjective: To observe the expression of hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) in rat normal cornea and in rat cornea after alkali burns. Methods: HGF and VEGF were detected in rat normal cornea and in rat corneas after alkali burns by immunohistochemistry method. Results: Immunohisto-chemistry showed HGF was observed in the epithelium,stroma and endothelium of rat normal corneas;VEGF was observed in the epithelium of rat normal corneas. After alkali burns, the rat corneas were infiltrated by massive inflammatory cells which showed staining for HGF and VEGF.Besides,endothelial cells of new vessels also showed staining for HGF and VEGF. The expression of HGF and VEGF increased at 6 hours after cautery. HGF and VEGF protein peaked at 4 days after cautery , decreaced after 7 days , and significant decreased to near base line after 14 days . The expression of HGF had a positive correlation with VEGF. Conclusions: Both HGF and VEGF play a very important role in CNV following comeal burns with alkali. They promote CNV synergistically.Part III The expression of heparanase in rat corneas after alkali burnsObjective: To observe the expression of heparanase (HPA) in rat normal cornea and in rat cornea after alkali burns, and discuss the effects of HPA on CNV. Methods: Semi-quantitative RT-PCR method was used to investigate the expression of HPA mRNA in rat normal cornea and in rat corneas after alkali burns. Results: There was trace HPA mRNA expression in rat normal corneas. The expression of HPA mRNA was initially increased at 6 hours after corneal burns with alkali.HPA mRNA peaked at 4 days after cautery , decreaced after 7 days , and significant decreased to near base line after 14 days . Conclusions: HPA production correlates with cautery induced angiogenesis in the rat cornea and plays a very important role in CNV following corneal burns with alkali.Postgraduate student:Qian Li (Ophthalmology) Directed by Prof. Gui-Qiu Zhao...