Experimental Study Of The Inhibitory Effect Of Octreotide On The Iris Neovascularization In Mice

PART ONE: DEVELOP THE C57BL/6J MOUSE'S MODEL OF OXYGEN-INDUCED IRIS NEOVASCULARIZATIONObjective: To develop proliferative neovascularization in the mice model of C57BL/6J for researching pathogenesis and therapeutic intervene- tion of iris neovascularization in the iris.Methods: Twenty seven-day-old mice were exposed to 75% oxygen for 5 days and then back to normal air.Age matched twenty mice without high oxygen exposure were used as controls.The iris of each 17-day-old mice was dissected.HE staining and the proliferative neovascular response was quantified by counting the vascularization of new vessels in and exten- ding from iris. Transmission electron microscope (TEM) were used to ob- serve changes of iris vessels on postnatal the 17th day. Immunohistochemi- cal expressions of VEGF was used to observe changes of new vessels in iris of both groups.Results: The increased density of iris blood vessels in eyes in the hyperoxia group were found in iris tissue-slices. The number of the neovascularizations in iris was significantly less in the iris of the normoxia control group (4.88±3.07) (P<0.01) than in hyperoxia group (9.12±4.26). The number of immunohistochemical expressions to antigen VEGF were significantly less in the iris in the normal group (25.37±7.85) than in hyperoxia group (37.12±11.99) respectively (P<0.01).Conclusion: The reproducible and quantifiable mice model of oxygen-induced iris neovascularization may facilitate the further researches of pathogenesis and medical intervention of iris neovascularization and neovascular glaucoma.PART TWO: EXPERIMENTAL STUDY OF THE INHIBITORY EFFECT OF OCTREOTIDE ON IRIS NEOVACULARIZATION IN MICEObjective: To explore the inhibitory effect of Octreotide on iris neovascularization. And to explore a new method of the tharepy of iris neovascularization and neovascular glaucoma.Methods: Hyperoxia was induced in ischemic irisopathy model in 80 mice. Twenty mice received an intraperitoneal injections of 50μg/kg Octreotide twice daily for 5 days as small-dosage treatment group and other 20 mice received an intraperitoneal injections of 100μg/kg as the large one, while the same number of mice received an intraperitoneal injection of same volume of BSS injection as contro1.In addition 20 untreated mice served as the normal group. Light microscope (LM) and transmission electron microscope (TEM) were used to observe changes of iris vessels on postnatal the 17th day. The effect of Octreotide on neovascularization of iris was evaluated by counting the new vessels in iris in the tissue-slices and immunohistochemical expressions of VEGF and MMP-2 in iris.Reversal transcription-polymerase chain reaction (RT-PCR) was used to observe expressions of VEGF mRNA in the tissue of iris in each group.Results: The reduced density of iris blood vessels in the eyes of treatment group were found in iris tissue-slices.The number of new vessels in iris was significantly less in the eyes of the small-dosage group (6.68±3.62) and large-dosage group (4.38±2.46) than in control group (9.82±3.89) respectively (P<0.01).The number of new blood vessels in the large-dosage group was significantly less than that in the small-dosage group (P<0.01).The density of immunohistochemical expressions to antigen VEGF were significantly less in the iris of the treatment group than that in the control group (38.26±13.50) respectively (P<0.01).The number of immunohistochemical expressions to MMP-2 in the treated group was significantly less than that in the control (29.73±11.14) (P<0.01). The immunohistochemical expressions to VEGF and MMP-2 in the large-dosage group was less than that in the small-dosage group respectively (P<0.01). The results of RT-PCR showed space-time corresponding relation between expression of VEGF and neovasculari- zation, which meant that the transcription of VEGF mRNA decreased in hyperoxia condition and increased in relative hypoxia condition. The expression of VEGF decreased.Conclusion: Intraperitoneal injections of Octreotide can effectively inhibit iris neovascularization, depending on dosage. And Octreotide may be used a new method of the tharepy to neovascularization of iris and neovascular glaucoma in the future.