The roles of regional specialization, mechanical forces and epigenetic memory after perturbation and injury of the intestinal stem cell microenvironment

项目摘要/摘要 小肠上皮每2至5天更新一次，使其成为再生能力最强的哺乳动物之一。 纸巾。了解推动这种更新的肠道干细胞(ISCs)既是一门重要的基础科学 这是一个问题，也是再生医学中转化方法的一个重要起点。遗传 可诱导命运图(GIFM)研究已经确定了肠道中两个主要的上皮干细胞池。 一个池由柱状Lgr5表达细胞组成，这些细胞周期很快，主要存在于 另一个由表达Bmi1或其他标记的细胞组成，这些细胞主要位于隐窝上方 基地。我们最近证明(Tian等人，《自然》，2011)，表达Bmi1的ISCs可以产生Lgr5- 在正常生理条件下表达ISCs。重要的是，当我们专门消融LGR5时- 表达ISCs和表达Bmi1的ISCs能够维持近端小鼠上皮细胞的动态平衡 肠子。这些结果已经被其他几个小组证实，表明Lgr5-和Bmi1- 表达ISCs构成两个截然不同但可能部分重叠的群体。一个重要的 问题是，哪些信号通路调节这些不同的干细胞群体，以及越来越多的 有证据表明，Wnt和Notch信号引导表达Lgr5和Bmi1的干细胞自我更新。 在这个应用中，我们建议使用通路特异性阻断抗体来理解这种差异。 以及Wnt和Notch信号在ISCs自我更新和谱系命运决定中的联合作用。这 独特的方法-结合抗体阻断和基因命运图谱-打开了有趣的新 超越传统的纯基因方法的途径。这些研究的结果将给我们带来重要的启示。 关于ISCs自我更新和分化的机制，这将有助于理解这些角色 ISCS在动态平衡和疾病方面的研究，将有助于为未来器官再生的尝试奠定基础。

PROJECT SUMMARY/ABSTRACT The small intestine epithelium renews every 2 to 5 days, making it one of the most regenerative mammalian tissues. Understanding the intestinal stem cells (ISCs) that fuel this renewal is both an important basic science question and an essential starting point for translational approaches in regenerative medicine. Genetic inducible fate mapping (GIFM) studies have identified two principal epithelial stem cell pools in the intestine. One pool consists of columnar Lgr5-expressing cells that cycle rapidly and are present predominantly at the crypt base, and the other consists of cells expressing Bmi1 or other markers that largely reside above the crypt base. We have recently demonstrated (Tian et al, Nature, 2011) that Bmi1-expressing ISCs give rise to Lgr5- expressing ISCs under normal physiological conditions. Importantly, when we specifically ablated Lgr5- expressing ISCs, Bmi1-expressing ISCs were able to maintain epithelial homeostasis in the proximal small intestine. These results, which have been confirmed by several other groups, indicated that Lgr5- and Bmi1- expressing ISCs constitute two distinct, although possibly partially overlapping, populations. An important question is which signaling pathways regulate these different stem cell populations, and a growing body of evidence indicates that Wnt and Notch signaling guide both Lgr5- and Bmi1-expressing stem cell self-renewal. In this application, we propose to employ pathway-specific blocking antibodies to understand the differential and combinatorial effects of Wnt and Notch signaling on self-renewal and lineage fate decisions in ISCs. This unique approach – combining antibody blockade and genetic fate mapping – opens up interesting new avenues beyond the traditional purely genetic approaches. The results of these studies will shed important light on the mechanisms by which ISCs self-renew and differentiate, which will help to understand the roles of these ISCs in homeostasis and disease and will help to lay the groundwork for future attempts at organ regeneration.