Development and Function of Biliary Tuft Cells

项目摘要 胆汁系统储存、修饰和提供胆汁的调节排泄，需要暴露于潜在的 破坏性强酸性管腔内容物维持强大的上皮屏障，有限的免疫反应 正常胆汁扰动，并区分致病性和非致病性变化的管腔 内容物对体内平衡的胆道功能至关重要。屏障失效或异常的免疫调节可导致 炎症是称为胆管病的胆道疾病中疾病进展的关键组成部分。尽管 胆汁静止在肝胆系统功能中起着关键作用，我们对体内平衡的理解 胆道系统中的免疫调节是有限的。一个线索可能是胆管中簇状细胞的惊人丰富 上皮簇状细胞，具有化学感受机制的分泌性上皮细胞，使免疫细胞“回路”成核 在小肠中，簇细胞IL-25促进先天淋巴细胞产生IL-13。是否 簇状细胞在其它组织中的类似免疫或组织调节作用现在才被探索。我们有 发现胆管细胞表达核心簇细胞基因程序，一种组织特异性基因标记， 对胆汁酸产生的扰动敏感。胆囊管和肝外胆管的丛状细胞分析 缺陷型小鼠表明在不存在簇细胞的情况下，该组织中异常的免疫细胞积累。已知 小肠中簇状细胞的作用表明胆管簇状细胞可以起到整合胆管上皮的作用 与小肠相反，我们的数据表明，胆管细胞可以抑制免疫系统， 炎症反应。总之，这表明胆管细胞可能在胆汁酸中发挥未被重视的作用， 传感或适应性反应扰动胆汁酸丰度，并可能调节胆汁免疫反应。 这项提议将检验胆丛细胞丰度受胆汁含量控制的假设， 簇状细胞在体内平衡时抑制胆汁免疫反应。我们将利用敏感的IL-25 基于体内工具来表征整个过程中簇状细胞的丰度、位置和发育调节， 胆道系统我们将试图了解胆汁酸处理影响胆丛的机制， 使用体外和体内方法测定细胞丰度。我们将评估簇状细胞如何调节免疫 胆道系统的“音调”，以及在感染期间可能产生的后果。分泌和 归因于簇状细胞的化学感受功能使这些细胞成为胆汁内容物与组织的有吸引力的整合者 或免疫细胞反应，而独特的基因表达谱的胆管细胞表明治疗 延展性除了确定胆管细胞的新的、组织特异性作用的可能性外，我们的工作将 增加了对胆汁免疫应答的现有知识，以及对胆汁免疫应答之间异质性的理解。 胆管上皮细胞、基质细胞和免疫细胞。未来的研究将调查簇状细胞功能， 肝胆炎症和疾病的模型，并探讨簇状细胞丰度与人类 胆道疾病状态，具有巨大的潜力，以推进新的治疗目标，在胆道病理学。

PROJECT SUMMARY The biliary system stores, modifies, and provides regulated excretion of bile, necessitating exposure to potentially damaging, highly acidic luminal contents. Maintenance of a robust epithelial barrier, limited immune responses to normal bile perturbations, and discrimination between pathogenic and non-pathogenic changes in luminal contents are critical to homeostatic biliary function. Barrier failure or aberrant immune regulation can lead to inflammation, a key component of disease progression in biliary diseases known as cholangiopathies. Despite the critical role biliary quiescence plays in function of the hepatobiliary system, our understanding of homeostatic immune regulation in the biliary tree is limited. One clue may be the striking abundance of tuft cells in the biliary epithelium. Tuft cells, secretory epithelial cells with chemosensory machinery, nucleate an immune cell “circuit” in the small intestine in which tuft cell IL-25 promotes the production of IL-13 from innate lymphoid cells. Whether similar immune or tissue-modulating roles for tuft cells exist in other tissues is only now being explored. We have found that biliary tuft cells express the core tuft cell gene program, a tissue-specific gene signature, and are sensitive to perturbations in bile acid production. Analysis of gallbladder and extrahepatic ducts from tuft cell deficient mice indicates aberrant immune cell accumulation in this tissue in the absence of tuft cells. The known roles of tuft cells in the small intestine suggests that biliary tuft cells could serve to integrate the biliary epithelium with the immune system; in contrast to the small intestine, our data indicate biliary tuft cells could inhibit inflammatory responses. Together, this suggests that biliary tuft cells could play unappreciated roles in bile acid sensing or the adaptive response to perturbed bile acid abundance, and may regulate biliary immune responses. This proposal will test the hypothesis that biliary tuft cell abundance is controlled by bile content, and that tuft cells repress biliary immune responses at homeostasis. We will take advantage of sensitive, IL-25 based in vivo tools to characterize the abundance, position, and developmental regulation of tuft cells throughout the biliary tree. We will seek to understand the mechanism whereby bile acid manipulation impacts biliary tuft cell abundance using in vitro and in vivo approaches. We will assess how tuft cells might regulate the immune “tone” of the biliary tree, and what consequences this may have during infection. The secretory and chemosensory functions attributed to tuft cells make these cells attractive integrators of bile content with tissue or immune cell responses, while the unique gene expression profile of biliary tuft cells suggests therapeutic malleability. In addition to the potential for defining novel, tissue-specific roles for biliary tuft cells, our work will add to the existing knowledge on biliary immune responses, as well as the understanding of heterogeneity among biliary epithelial, stromal, and immune cells. Future studies will investigate tuft cell function in more complex models of hepatobiliary inflammation and disease and explore the correlation of tuft cell abundance with human biliary disease states, with great potential to advance new therapeutic targets in biliary pathologies.