AIP1介导VEGFR2/3复合体调控角膜微环境淋巴管增生的分子机制

We have recently demonstrated that AIP1 blocks vscular angiogenesis as an endogenous inhibitor of VEGFR2. Further, AIP1 negatively regulates TLR4 signaling in vitro,and might suppresses inflammation in vivo. However, the role of AIP1 in lymphangiogenesis has not been investigated. A rationale for the hypothesis that AIP1 plays a critical role in cornea limbus niche lymphangiogenesis based on an observation of blood and lymphatic vessels angiogenesis coupled during inflammation/cornea graft reject reaction. In our preliminary data, increased macrophages infiltration and lymphangiogenesis will be shown in AIP1 deficient mice, which indicates both macrophages and LECs regulated by AIP1. In WT cornea model, AIP1 is down-regulated in response to vascular endothelial growth factor (VEGF-A). AIP1-deficient mice mount remarkable stronger lymphangiogenic responses to VEGF-A and VEGF-C. We propose that AIP1 plays a critical role in corneal limbus niche lymphangiogenesis by regulating maturation and mobilization of bone marrow progenitors, which differentiate into endothelial cells, lymphatic endothelial cells, and monocytes/macrophages. To test our hypothesis, we propose the following specific aims: 1. define the functional significance of AIP1 in lymphagiogenesis in vivo by human samples and genetic deletion mice(AIP1-/- or AIP1 Cre Prox-1 loxlox, an LEC-specific Prox-1 deleter, leading to LEC-specific deletion of AIP1). Further, if macrophages play critical role as described, we determine the role of AIP1 in macrophages. 2. Define the function of AIP1 in lymphatic endothelial cells in vitro using isolated mouse and human LEC cells Line. Finally, mechanistically, we dissect AIP1 mediates VEGF-dependent lymphangiogenic signaling. We propose that AIP1 regulates VEGF-C induced signaling and associates with VEGFR2/3 complex heterodimerization. A better insight into the mechanism of of AIP1 on cornea lymphangiogenesis may provide therapeutic interventions to treat lymphangiogenesis-related disorders, such as cornea inflammation, transplantation rejection and cancers.

前期研究证明 AIP1作为VEGFR2内源性抑制因子抑制血管增生，并且破坏TLR4-TIRAP-MyD88复合体形成抑制炎症信号，说明AIP1在炎症反应中有重要的作用，但迄今对其在淋巴管系统的调控仍然未知。炎症介导血管和淋巴管增生相伴行，我们设想AIP1同时调控两个脉管系统。AIP1敲除增加角膜和肿瘤巨噬细胞浸润及淋巴管增生，表明AIP1对淋巴管内皮细胞和巨噬细胞都有重要调控。我们假设 AIP1调控VEGF-C介导的VEGFR2/VEGFR3复合体形成和协同，抑制骨髓源性祖细胞动员活化，抑制巨噬细胞生物功能。为进一步揭示这些问题，我们以感染性角膜炎标本及AIP1基因敲除鼠为研究对象，阐释AIP1对淋巴管增生功能性影响，明确AIP1介导的信号转导机制。研究成果可为感染性角膜炎和角膜移植排斥的免疫治疗提供一个新思路。

我们前期研究证明 AIP1作为VEGFR2内源性抑制因子抑制血管增生，并且破坏TLR4-TIRAP-MyD88复合体抑制炎症信号通路，说明AIP1在炎症反应中有重要的作用，但迄今对其在淋巴管系统的调控仍然未知。炎症介导血管和淋巴管增生相伴行，我们设想AIP1同时调控两个脉管系统。AIP1敲除增加角膜和肿瘤巨噬细胞浸润及淋巴管增生，表明AIP1对淋巴管内皮细胞和巨噬细胞都有重要调控。本研究中，我们首先研究了AIP1缺乏的小鼠的血管发育。我们发现AIP1全身敲除或血管内皮特异性缺失减少了同时表达VEGFR-2和VEGFR-3的视网膜血管的萌发和出芽。与之相反，神经细胞特定的AIP1缺失对视网膜血管生成没有不良影响。减少的VEGFR-3信号与AIP1-KO小鼠的视网膜表型相关联。在皮肤和肠系膜模型，AIP1-KO的幼崽表现出了VEGFR-3依赖的发育性淋巴管生成缺陷。此外，VEGFR-3-特异性配体突变VEGF-C (C156Ser)诱导的体内淋巴管生成(角膜淋巴血管生成试验)和体外(人类淋巴管内皮细胞迁移实验)均减少或减慢。综合起来，这些结果支持AIP1在与VEGFR-3相关的血管生成和淋巴血管生成方面的重要作用。我们的结论是炎症早期AIP1通过抑制VEGF-A/VEGFR-2介导的血管渗漏抑制炎症反应，炎症后期通过增强VEGF-C/VEGFR-3 介导淋巴管增生。因此，AIP1作为炎症和淋巴管增生的联系环节，为炎症和淋巴管增生疾病治疗提供了一个新靶点。