The Expression Of VEGF And TNF–α In Neonatal Rats With High Oxygen–induced Retinopathy And The Intervention Effect Of Dexamethasone

As one of the important reasons of blindness in children around the world,retinopathy of prematurity (ROP) has been the focus of attention, which occur inpremature infants and low birth weight infants, is a proliferative retinopathy. Thecause of ROP is imcompleted development of premature retinal vascular, whichappears to retinal ischemia, further leading to neovascularization accompanied byfibrosis, even resulting in proliferative retinopathy or retinal detachment. Thereforethe study of pathogenesis of neovascularization become hotspots in recent years, Thepattern through the inhibition of the formation of new blood vessels become a newresearch field in the prevention and treatment of ROP.Recently studies demonstrated that retinal vascular hyperplasia is seriouscomplications of ischemic retinal disease, proliferation of the endothelial cell ismainly composed of the Balance control between angiogenesis stimulating factor andinhibiting factor, once the balance is broken, the growth of new blood vessels will beinduce. Study found that upregulation of promoting factor can occurneovascularization, and downregulation of inhibiting factor is also the key for thegrowth of new blood vessels. These factors mainly include vascular endothelialgrowth factor (VEGF), tumor necrosis factor alpha (TNF-alpha), pigment epitheliumderived factor (PEDF), fibroblast growth factor (FGF) etc.VEGF is important for theformation of blood vessel whether in normal or abnormal state,which play a crucialrole on the normal development and maturation process of retinal vessels.The changesbetween qualitative and quantitative of retinal vascular in ROP are due to the changesof expression level of VEGF. In addition to VEGF, as an important vascular induction factor, TNF-alpha may play an important role in inflammation, apoptosis andangiogenesis processes.Therefore retinal angiogenesis inhibitor therapy has become aquite big research prospect of neovascular treatment with larger research prospect.In recent years research at home and abroad have reported treatment ofdexamethasone on some retinal diseases such as acute anterior uveitis, retinal blastinjury, proliferative diabetic retinopathy and corneal alkali burn.Clinicallyglucocorticoid dexamethasone promoting fetal lung maturation widely use inantenatal period.It is still lack of still lack whether dexamethasone has its effect andmechanism for the formation of ROP.ObjectiveThrough Simulating the pathological characteristics of retinopathy of prematurity,to establish an optimal animal model of oxygen induced retinopathy suitable forexamining pathogenesis and therapeutic intervention for ROP.To observe effect ofdexamethasone on retinal neovascularization in mouse of high oxygen inducedretinopathy, discuss whether it has inhibitory effect on neovascularization and itspossible mechanism.Furthermore.Furthemore,to investigate different doses ofdexamethasone will have different effects in order to find the optimum dose.Methods一．Establishment of mouse model with high oxygen induced retino-pathy：Fifty-eight7-day-oId C57BL/6J mice were divided into two groups. Twenty-nine mice in high-oxygen induced group(group2) were exp-osed to75%oxygen for5days and then to room air for another5days．Twenty-nine mice in normal controlgroup(group1) were exposed to room air for10days．In this two groups each eightmice were condemned to death in P12and P14,the rest of mice were killed in P17.Each mice to be put to death could be weighed.The proliferative neovascutarresponse was estimated by observing the vascular pattern in adenosine diphosphate—ase(ADPase) stained retina fiat—mounts and quantitated by counting thenumber of new vascular cell nuclei extending into the internal limiting membrane in cross-sections．二． The expression of VEGF and TNF—α in neonatal rats with highoxygen-induced retinopathy and the intervention effect of Dexamethasone:Sixty micewere divided into four group:high-oxygen high-dose dexamethasone group(group3),high-oxygen low-dose dexamethasone group(group4), high-oxygen controlgroup(group5) and safety evaluation group(group6). Every mice were weighed inP12、P14and P17in each group,then were condemned to death in P17. Theproliferative neovascutar response was estimated by observing the vascular pattern inadenosine diphosphate—ase(ADPase) stained retina fiat—mounts and quantitatedby counting the number of new vascular cell nuclei extending into the internallimiting membrane in cross-sections．The expression of VEGF protein and TNF-alphaprotein in the retina including intensity and distribution in newborn rats.Results一．Establishment of mouse model with high oxygen induced retino-pathy：1. Hyperoxia－induced neovascularization occurred at the junction between thevascularized and avascular retina in the mid-periphery in all mice exposed tohyperoxia.2. The number of vascular endothelial cell nuclei dramatically increased inhigh-oxygen induced group,and there existed statistically significant betweenhigh-oxygen induced group and normal control group.3. At P17,no difference between the right and left eyes was found in high-oxygeninduced group.二． The expression of VEGF and TNF—α in neonatal rats with highoxygen-induced retinopathy and the intervention effect of Dexamethasone:1.ADP enzyme staining: nonperfusion area is apparently contractible andneovascularization is not obvious in high-oxygen high-dose dexamethasone group andhigh-oxygen low-dose dexamethasone group,each of which was significantly closer tonormal control group. There was no difference between safety evaluation group and. high-oxygen induced group.2. HE staining:At P17, the number of vascular endothelial cell nuclei inhigh-oxygen high-dose dexamethasone group or high-oxygen low-dosedexamethasone group was fewer than that in high－oxygen induced group andhigh-oxygen control group（P<0.01）.There was no statistical difference betweenhigh-oxygen high-dose dexamethasone group and high-oxygen low-dosedexamethasone group.3. Immunohistochemical results: the expression of VEGF or TNF—α wasenhanced in high-oxygen induced group and high-oxygen control group．But it wasweakened in high-oxygen high-dose dexamethasone group and high-oxygen low-dosedexamethasone group. There was statistical difference between high-oxygen inducedgroup and high-oxygen either-dose dexamethasone group (P<0.01)．4. At P12and P17，weight of mice in high-oxygen either-dose dexamethasonegroup showed significant differences on that in normal control group.Conclusions1. The successful establishment of an optimal mouse model of oxygen inducedretinopathy suitable for examining pathogenesis and therapeutic intervention for ROP.2. The expression of VEGF protein and TNF-a protein in the retina enhanced inmouse models with ROP,.As important vascular factors, their expression have closerelationship to retinal neovascularization.3. Dexamethasone may inhibit retinal neovascularization so that could have aprotective effect on ROP.4. It was one of the mechanism that dexamethasone suppressed the expression ofVEGF protei and TNF–a.