The Expressions And Their Relationship Of VEGF And MMP-2 In A Rat Model Of Retinopathy Of Prematurity

Retinopathy of prematurity (ROP) is a retinal disease which takes place in premature delivery and the low weight babies and results in complications,such as vitreous hemorrhage and retinal detachment,and eventually leads to blindness,its pathologic characteristic is abnormal retina vascular proliferation.Study indicates retinal neovascularization has predominance function in the mechanism of Retinopathy of prematurity.It is believed that homeostasis of angiogenesis is regulated by two counterbalancing systems: angiogenic stimulators and angiogenic inhibitors. The balance is critical for the regulation of angiogenesis. It has been reported that the angiogenic factor (i.e.,VEGF) plays a major role in mediating intraocular neovascularization and is the most important and the most valid material priming retinal neovascularization.Neovascularization is the result of altered balance between positive and negative regulators of endothelial activation,which leads in turn to basement membrane degradation,endothelial cell migration and proliferation followed by capillary tube formation. Several matrix metalloproteinases (MMPs) are believed to be important in this process, but particular interest has been focused on MMP-2,because it preferentially degrades basement membrane components such as type IV collagen,which must be degraded to facilitate the migration of vascular endothelial cells.Currently, MMP-2 in the formation of retinal neovascularization in Retinopathy of Prematurity in whether to produce a effect,is still not quite explicit.Therefore,this research using Oxygen Induced Retinopathy model(OIR) to simulate the process of ROP and appling of immunohistochemical method examines the expressions of MMP-2,VEGF and inquiris into their contributions and their relationship in Retinopathy of Prematurity.Materials and MethodsNewborn C57BL/6J rats were raised in standardized incubator.Beginning on postnatal day 7 (P7) of life, ROP group was exposed to 75% oxygen concentration for 5 days,and returned to room air. In this process,the oxygen concentration was maintained 75%±2%.The room air controls feed under the normal air environment from postnatal day 7 of life to postnatal day 12 of life.ROP group and control group rats were sacrificed on day 17 of life.Retinas were dissected and stained by adenosine diphosphatase (ADPase) histochemistry for assessment of intraretinal vascular development and preretinal angiogenic vessel growth.The proliferative neovascularization response was quantified by counting the nuclei of new vessels extending from the retina into the vitreous in cross-sections.The expressions of VEGF and MMP-2 in the retinas of the pups were determined by immunohistochemical method.Protein expressions of PEDF and VEGF were studied immunohistochemically.Cross-sections could be analyzed with light microscopy using Metamorph/DP10/BXS1 image-analysis software and compared between groups. In all the experiments, the probability level P<0.05 was considered to indicate a statistically significant difference.ResultThere were large retinal neovascularization in the high concentration oxygen group compared with in the normal air condition group,and the density and shape of retinal neovascularization were disordered.This result indicated that the rat model of retinopathy of prematurity was successful.IOD of VEGF was significantly increased in the ROP group 60.85±24.55 verse 36.81±14.60 in the control group. There was significant difference (t=3.348, P<0.01) in the level of VEGF between ROP group and control group.IOD of MMP-2 was significantly increased in the ROP group 21.12 + 6.29 verse 16.33±4.13 in the control group.There was significant difference (t=3.160, P<0.01) in the level of MMP-2 between ROP group and control group.There was positive relationship between proteins of MMP-2 and protein of VEGF (r=0.633, P<0.01) .ConclusionIt suggests that the existences of VEGF and MMP-2 in a rat model of retinopathy of prematurity are correlated with retinal neovascularisation and provides a new theoretical foundation for pathogenesis of ROP. They may be essential in the regulation of retinal neovascularization.Pharmacologic intervention using VEGF and MMP-2 inhibitors may be a future therapeutic approach for angiogenic retinal diseases.