Determining the role of CSF1R-dependent macrophages in of Paneth cells and the intestinal stem cell niche

肠上皮细胞是自我更新的，每5-7天不断更换。为了做到这一点，肠干细胞位于每个手指状绒毛的基部。这些干细胞产生高度增殖的子细胞，其可以分化成不同的肠上皮细胞群，例如：杯状细胞、簇状细胞和潘氏细胞。分化的细胞沿着绒毛上皮移动，并在尖端脱落之前执行其生理功能。一种特殊的细胞类型称为潘氏细胞，仍然位于这些隐窝的底部，位于肠道干细胞之间。潘氏细胞的主要功能是释放抗微生物产物，如溶菌酶和防御素，其有助于保护隐窝免受细菌感染。潘氏细胞还产生维持肠道干细胞所必需的分子。当潘氏细胞丢失时，这也会导致肠道干细胞的丢失，最终影响肠道上皮。巨噬细胞大量分布在整个肠壁，这些吞噬细胞有助于保护肠道免受感染，但也有助于支持肠上皮细胞。我们已经表明，当这些巨噬细胞丢失时，这会导致随后的潘氏细胞和肠干细胞的丢失。我们的研究揭示了巨噬细胞在潘氏细胞和肠干细胞的组成性维持中的一个以前未被认识到的重要作用。巨噬细胞耗竭对潘氏细胞和肠干细胞的干扰也对肠上皮中其他类型上皮细胞的后续形成和功能产生不利影响。在小肠派伊尔集合淋巴结中，专门的抗原取样M细胞的分化和功能受损。与此相反，分泌粘液的杯状细胞的分化和丰富性增强。这表明，肠壁中巨噬细胞的表型或丰度的改变，例如在CSF 1 R阻断、病原体感染或炎症后，可显著影响肠上皮的发育和对肠抗原取样的能力。潘氏细胞功能障碍是明显的克罗恩病患者小肠受累，可能是一个结果，从单核细胞提供的支持不足。在这个项目中，我们将研究巨噬细胞在维持潘氏细胞和肠干细胞中的作用。我们还将确定巨噬细胞耗竭对M细胞的影响是否影响粘膜免疫系统对肠道中的外来颗粒进行采样并对其产生特异性免疫应答的能力。我们还旨在确定一种称为Wnts的特定分子是否是巨噬细胞产生的支持潘氏细胞和肠干细胞的重要因子。最后，我们将确定巨噬细胞耗竭对潘氏细胞和肠干细胞的不良影响是否可以通过R-spondin 1分子治疗来恢复。药理学CSF 1 R-阻断已被提出作为调节某些癌症、炎症、自身免疫和骨疾病的手段。然而，CSF 1 R阻断也消耗巨噬细胞。因此，CSF 1 R阻断可间接损害潘氏细胞和肠干细胞、肠上皮细胞分化以及粘膜免疫系统从肠腔采样Ag和病原体的能力。彻底分析巨噬细胞在维持潘氏细胞和肠干细胞中的作用对于帮助识别有助于支持这些细胞的巨噬细胞因子至关重要。该项目的信息将有助于开发新的疗法来治疗某些与潘氏细胞和肠隐窝紊乱相关的肠道疾病。

The epithelium which lines the intestine is self-renewing and is continually replaced every 5-7 d. In order to do this, intestinal stem cells are situated at the base of each finger-like villous. These stem cells produce highly proliferative daughter cells which can differentiate into distinct intestinal epithelial cell populations, eg: goblet cells, tuft cells and Paneth cells. The differentiated cells travel along the villus epithelium and perform their physiological functions before being shed at the tip. A particular cell type known as the Paneth cell, remains at the base of these crypts nestled between the intestinal stem cells. A primary function of the Paneth cells is release antimicrobial products such as lysozymes and defensins which help to protect the crypt from bacterial infection. Paneth cells also produce molecules which are essential to maintain the intestinal stem cells. When Paneth cells are lost, this also leads to a loss of the intestinal stem cells, ultimately affecting the gut epithelium. Macrophages are abundantly positioned throughout the gut wall, These phagocytic cells help to protect the intestine against infection, but also help support the gut epithelium. We have shown that when these macrophages are lost, this leads to the subsequent loss of Paneth cells and intestinal stem cells. Our studies reveal a previously-unrecognised, essential role for macrophages in the constitutive maintenance of Paneth cells and intestinal stem cells. The disturbances to the Paneth cells and intestinal stem cells caused by macrophage-depletion also adversely affected the subsequent formation and function of other types of epithelial cells in the gut epithelium. The differentiation and function of specialised antigen sampling M cells was impaired in the Peyer's patches of the small intestine. In contrast, the differentiation and abundance of the mucous-secreting goblet cells was enhanced. This suggests that modification of the phenotype or abundance of macrophages in the gut wall, for example after CSF1R-blockade, pathogen infection or inflammation, could dramatically affect the development of the intestinal epithelium and the ability to sample gut antigens. Paneth cell-dysfunction is evident in Crohn's disease patients with small intestinal involvement, and may be a consequence of inadequate provision of support from monocytes. In this project we will study the role of macrophages in the maintenance of Paneth cells and intestinal stem cells. We will also determine whether the effects of macrophage-depletion on M cells affect the ability of the mucosal immune system to sample foreign particles in the intestine and mount a specific immune response to them. We also aim to determine whether a specific class of molecules known as Wnts are the important factors which the macrophages produce to support the Paneth cells and intestinal stem cells. Finally, we will determine whether the adverse effects of macrophage-depletion on Paneth cells and intestinal stem cells can be restored by treatment with a molecule known as R-spondin1. Pharmacological CSF1R-blockade has been proposed as a means to modulate certain cancers, and inflammatory, autoimmune and bone diseases. However, CSF1R-blockade also depletes macrophages. Therefore, CSF1R-blockade could indirectly compromise Paneth cells and intestinal stem cells, cell differentiation in the gut epithelium and the ability of the mucosal immune system to sample Ag and pathogens from the gut lumen. A thorough analysis of the role of macrophages in the maintenance of Paneth cells and intestinal stem cells is essential to help identify the macrophage factors which help support these cells. The information from this project will help develop new therapeutics to treat certain intestinal diseases associated with disturbances to Paneth cells and intestinal crypts.