Role of RPE-derived VEGF in Choroid Development and Stability

描述（由申请人提供）：尽管大量证据表明视网膜色素上皮在脉络膜脉管系统的发育和维持中起作用，但这种关系的机制尚不清楚。除了在正常视网膜中的重要功能外，RPE和脉络膜脉管系统之间的相互作用是许多视网膜病变的核心，包括年龄相关性黄斑疾病（ARMD），如地理萎缩。一些研究结果表明，血管内皮生长因子（VEGF）可能是脉络膜血管中RPE细胞存活效应的中介。来自实验模型的数据表明VEGF在血管稳定中具有生存功能，成人的RPE产生VEGF，脉络膜内皮细胞表达VEGF受体，我们发现VEGF受体在成人中是组成性激活的。因此，我们建议通过以下目的来验证rpe衍生的VEGF对于脉络膜血管的发展和维持是必要的假设。(1)测定VEGF家族成员及其受体（VEGFR1、VEGFR2、VEGFR3、neuropilins）在发育期间和成人脉络膜- rpe复合体中的表达模式和VEGF受体激活状态。(2)研究VEGF在脉络膜血管发育中的作用，使用仅表达VEGF188（一种通常不由RPE产生的同种异构体）的小鼠和RPE特异性缺失VEGF的小鼠。VEGF在维持成人脉络膜血管中的作用将通过使用SU5416（一种小分子VEGFR2选择性酪氨酸激酶抑制剂）抑制VEGFR2酪氨酸磷酸化来确定；并使用可诱导的DN-VEGFR2转基因小鼠模型干扰rpe来源的VEGF与脉络膜内皮VEGFR2之间的相互作用。(3)评估外源性添加VEGF对实验性RPE破坏引起的脉络膜损失的“拯救”能力。RPE会被全身碘酸钠（NalO3）破坏，VEGF在RPE对脉络膜营养效应中的作用将通过研究外源性添加VEGF挽救脉络膜损失的能力来评估。这些研究的结果将提供RPE支持正常脉络膜功能的机制，从而可能为黄斑变性致盲疾病的治疗干预提供靶点。

DESCRIPTION (provided by applicant): Although a significant body of evidence indicates a role for the retinal pigment epithelium in the development and maintenance of the choroidal vasculature, the mechanisms that underlie this relationship are unknown. In addition to an important function in the normal retina, the interactions between RPE and the choroidal vasculature are central to a number of retinal pathologies, including age-related macular diseases (ARMD) such as geographic atrophy. Several findings point to a possible role for vascular endothelial growth factor (VEGF) as a mediator of the RPE cell survival effect on choroidai vessels. Data from experimental models indicate a survival function for VEGF in vessel stabilization, RPE in the adult make VEGF, and choroidal endothelial cells express VEGF receptors, which we show are constitutively activated in the adult. We therefore propose to test the hypothesis that RPE-derived VEGF is necessary for the development and maintenance of the choroidal vasculature by the following aims. (1) To determine the expression pattern of VEGF family members and their receptors (VEGFR1, VEGFR2, VEGFR3, and the neuropilins), and VEGF receptor activation status in the choroid-RPE complex during development and in the adult. (2) To examine the role of VEGF in choroidal vascular development using mice that express only VEGF188, an isoform not normally made by RPE, and mice with an RPE-specific deletion of VEGF. The role of VEGF in the maintenance of the adult choroidal vasculature will be determined by inhibition of the VEGFR2 tyrosine phosphorylation using SU5416, a small molecule VEGFR2-selective tyrosine kinase inhibitor; and interference with the interaction between RPE-derived VEGF and choroidal endothelial VEGFR2 using an inducible DN-VEGFR2 transgenic mouse model. (3) To assess the ability of exogenously added VEGF to "rescue" choroidal loss due to experimentally induced RPE destruction. RPE will be destroyed by systemic administration of sodium iodate (NalO3) and the role of VEGF in trophic effects of RPE on the choroid will be assessed by investigating the ability of exogenously added VEGF to rescue the choroidal loss. Results of these studies will provide mechanistic insight into the means by which RPE support normal choroidal function, and thus may reveal targets for therapeutic intervention into the blinding diseases of macular degeneration.