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

排列在肠道上的上皮是自我更新的，每隔5-7天就会不断更换一次。为了做到这一点，肠道干细胞位于每个指状绒毛的底部。这些干细胞产生高度增殖的子代细胞，可以分化为不同的肠道上皮细胞群，例如：杯状细胞、簇状细胞和潘氏细胞。分化的细胞沿绒毛上皮移动，并在顶端脱落之前执行其生理功能。一种被称为潘氏细胞的特殊细胞类型仍然存在于这些隐窝的底部，这些隐窝位于肠道干细胞之间。Paneth细胞的主要功能是释放抗微生物产物，如溶菌酶和防御素，帮助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损失，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，也有助于支持肠道上皮。我们已经证明，当这些巨噬细胞丢失时，这会导致随后的潘氏细胞和肠道干细胞的损失。我们的研究揭示了巨噬细胞在潘氏细胞和肠道干细胞的结构性维持中的一个以前未被认识到的重要作用。巨噬细胞耗尽对潘氏细胞和肠道干细胞造成的干扰也对随后肠上皮中其他类型上皮细胞的形成和功能产生了不利影响。特殊抗原采样的M细胞的分化和功能在小肠的Peyer‘s小结中受损。相反，分泌粘液的杯状细胞的分化程度和丰度均增强。这表明，肠壁巨噬细胞的表型或丰度的改变，例如在CSF1R阻断、病原体感染或炎症之后，可能会极大地影响肠道上皮细胞的发育和采集肠道抗原的能力。有小肠受累的克罗恩病患者存在明显的潘氏细胞功能障碍，这可能是单核细胞支持不足的结果。在这个项目中，我们将研究巨噬细胞在维持潘氏细胞和肠道干细胞中的作用。我们还将确定巨噬细胞耗尽对M细胞的影响是否会影响粘膜免疫系统对肠道中异物颗粒进行采样并对其进行特异性免疫反应的能力。我们还旨在确定一类特定的分子，即Wnts，是否是巨噬细胞产生的支持Paneth细胞和肠道干细胞的重要因素。最后，我们将确定巨噬细胞耗尽对潘氏细胞和肠道干细胞的不利影响是否可以通过一种名为R-Spindin1的分子治疗而恢复。药理学上的CSF1R阻断已被提议作为一种手段来调节某些癌症、炎症性疾病、自身免疫性疾病和骨骼疾病。然而，CSF1R-阻断也会耗尽巨噬细胞。因此，CSF1R的阻断可能间接损害Paneth细胞和肠道干细胞、肠上皮细胞的分化以及粘膜免疫系统从肠腔中提取抗原和病原体的能力。彻底分析巨噬细胞在维持潘氏细胞和肠道干细胞中的作用，对于帮助识别帮助支持这些细胞的巨噬细胞因子至关重要。来自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道隐窝功能障碍相关的肠道疾病。

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.