Role Of Notch-Dll4 In Laser-induced Choroidal Neovascularization In Rats

【Introduction】Choroidal neovascularization(CNV) reflect in many diseasesof retina and choroid such as age-related macular degeneration (AMD),chorioretinitis, presumed ocular histoplasmosis syndrome (POHS), angioidstreaks (AS), pathological myopia, and so on. Newly formed vessels generatedfrom the choriocapillaris infiltrate through Bruch's membrane, grow throughretinal pigment epithelium or neurepithelium. These vessels are immature,fragile and leaky, leading to the form of scar, which cause region injuery. Theseinjueries often develop in macular region and have influence over centralvision, so CNV is a significant reason of vision loss. The development of CNVis complicated and regulated by lots of factor. vascular endothelial growthfactor(VEGF) is known as a major pro-angiogenic growth factor, stimulates theproliferation of endothelial cells and increasing their permeability. Theanti-VEGF therapy is the main current therapy of CNV. Notch signal pathwayalso plays an important role in CNV. Delta-like ligand 4(Dll4) gene in Notchsignal pathway is known as another gene which deletion of half-value dose allelomorphic gene can induce the death of animals at embryonic period exceptVEGF gene. Dll4 plays an important role in angiogenesis. Investigate the roleof Dll4 in the development of CNV, can provid a new idea in the therapy ofCNV.【Objective】To investigate the mechanism of Dll4 in Notch signal pathway inexperimental CNV induced by photocoagulation in rats.【Methods】120 BN rats were randomly divided into four groups: Normalgroup(18 rats), group after photocoagulation(54 rats), medication administratedgroup(24 rats) and control group(24 rats). The experimental choroidalneovascularization was induced by 532 nm laser photocoagulation in BN rats.As soon as photocoagulation, Medication administrated group were treated byintravitreous injection with 10 l Avastin(25mg/ml) and control group weretreated by intravitreous injection with 10 l PBS(0.01M). The coexpression ofDll4 and vascular endothelial growth factor (VEGF) was detected by tripleimmunofluorescence in normal group(6 rats) and group at 7days afterphotocoagulation(6 rats). The protein and mRNA of Dll4 and VEGF wereexamined by Western-blotting and RT-PCR at normal group(12 rats), 1 day(12rats), 3 days(12 rats), 7 days(12 rats), 14days(12 rats) after photocoagulation.The expression of Dll4 and VEGF was examined by Western Blotting andRT-PCR at day 7 in medication administrated group(12 rats) and controlgroup(12 rats). The thickness and the area of CNV were qualified by HE andchoroidal flat mount at day 14 in medication administrated group(12 rats) andcontrol group(12 rats).【Results】The coexpression of Dll4 and VEGF existed in the area of CNV.The expression of Dll4 and VEGF were with one accord. The expression ofDll4 and VEGF increased at day 1, significantly increased at day 7 and then decreased at day 14. After the intravitreous injection with Avastin, in themedication administration group, the expression of Dll4 and VEGF wassignificantly decreased at day 7 compared to control group. The area of CNVin medication administration group(24202±2608 m2, n=8) were significantlydecreased at day 14 compared to control group(37226±3208 m2, n=10). Thethickness of CNV in medication administration group(53.68±5.89 m,n=9)were also significantly decreased at day 14 compared to controlgroup(82.86±7.46 m,n=11).【Conclusion】Dll4 plays an important role in the pathogenesis of CNV , themechanism may be concerned with the regulation of VEGF.