肠淋巴系统功能障碍在克罗恩病中的作用及Prox1的调控机制

Lymph flow is a critical player of intestinal lipids proteins, and other particles transport. Lymphatic obstruction, and remodeled and impaired contraction may lead to lipids leakage and fat deposition. Through release of the adipokines and cytokines, accumulated fat mass exerts its effects in the initiation or aggravation of intestinal inflammation in Crohn's disease (CD). Enlarged or obstructed-lymphatic vessels are important pathological features in patients with CD, supporting the notion that intestinal lymphatics are important player in the pathogenesis of CD although the exact mechanism remains unknown. Prox1 (prospero homeobox protein 1), a homeobox transcription factor, is a critical regulator of lymphatic system development and is critical for lymphatic endothelial cells differentiation. In our recent work, changes of mesenteric lymphatic system were demonstrated to be correlated with recurrence of CD, and Prox1 was found to be expressed in the intestine for patients with CD. In mice with colitis, Prox1 knock out was associated with acceleration of colonic inflammation, implying the participation of Prox1 in the pathogenesis of CD. To further explore the role of intestinal lymphatics in the pathogenesis of CD, the therapeutic effects and the underlying mechanisms of Prox1 pathway in this process, we propose the current project based on a combination of in vivo and in vitro studies. In this propose study, molecular biology, histology, and electrophysiology will be applied for carrying out this experiment evaluate the morphological and functional changes of intestinal lymphatic system in CD, the therapeutic effects and the potential mechanisms of Prox1. Results from our study may provide evidence for the pathogenesis of CD and for the clinical utility in the management of CD.

肠道淋巴管功能障碍会引起脂质外漏、脂质沉积。脂肪组织通过释放脂肪因子及细胞因子参与克罗恩病(CD)的病理生理。肠淋巴管结构及功能异常是CD的重要病理特征，但其中的机制尚不明确。Prospero同源蛋白1(Prox1)具有促进淋巴管增生及维持淋巴管结构及功能的作用。我们前期研究发现肠淋巴系统的病理性改变与CD的疾病进程显著相关、CD肠道组织Prox1的表达显著异常、上调Prox1的表达能够显著减轻CD模型小鼠的结肠炎症。本课题在前期工作基础上，以CD患者组织标本及CD模型小鼠为研究对象，通过分子生物学及分子免疫学等技术，研究肠淋巴系统结构异常及功能障碍在CD病理生理中的作用及其机制，探讨Prox1对CD动物模型的作用、对肠淋巴系统结构及功能的调节作用，并以淋巴内皮细胞为切入点，探索Prox1对CD肠淋巴系统的作用机制，为揭示CD 病理生理、为CD防治提供依据及新的靶点。

肠道淋巴系统担负着引流肠道内大分子物质调节免疫细胞迁移和维持肠黏膜免疫稳态中起到重要的作用。肠淋巴管增生及淋巴组织肉芽肿形成是克罗恩病(CD)的重要病理学特征，肠淋巴系统结构及功能异常是CD肠道炎症的重要发病机制。Prospero同源蛋白1(prospero homeobox protein 1, Prox1)具有促进淋巴管增生及维持淋巴管功能的作用。本课题组研究发现肠道Prox1的表达与CD的术后复发存在显著相关性；Prox1基因高表达小鼠能够显著抵抗TNBS诱导的结肠炎症。.本课题研究发现，CD患者肠道Prox1的表达与疾病进程及预后显著相关；CD患者肠系膜淋巴组织菲薄、分支增多，肠淋巴管系统出现结构破坏、淋巴增生等异常现象。CD患者淋巴管结构不连续，淋巴管内皮细胞的微结构破裂且不完整。作为维系肠系膜淋巴管通透性功能的紧密连接蛋白表达显著降低，肠淋巴管系统通透性明显增加。CD患者肠淋巴管存在通透性增加与Prox1的表达降低有关。CD模型小鼠出现肠淋巴管引流障碍及淋巴外漏，肠淋巴管结构及功能出现异常。Prox1可以促进肠淋巴管增殖、增加结肠淋巴管密度、调控肠淋巴管引流功能。Prox1高表达可以维持淋巴管结构的完整性、减轻肠道炎症。动物模型研究进一步发现，Prox1缺失导致肠淋巴系统通透性增加，小鼠更易发结肠炎且肠道炎症加重，而外源性予以Prox1可以改善肠淋巴管的通透性并显著促进肠道炎症的缓解。其作用机制可能与Prox1能够调节淋巴内皮细胞的VEGF和VEGFR3的信号通路有关。.研究意义：通过本项目的系统研究，证实Prox1对CD动物模型肠道炎症的作用效果；得出CD肠淋巴系统结构及功能障碍的病理基础，揭示Prox1对CD肠淋巴系统的作用，并基于肠淋巴内皮细胞发现Prox1对CD肠淋巴系统的作用机制；为揭示CD病理生理、为临床防治CD提供新的依据。