Differentiating Radio-sensitivities Among Intestinal Stem Cell Pools

描述(申请人提供)：肠道上皮每3-5天迅速更新一次，既有活跃的循环干细胞，也有静止的干细胞。辐射诱导的胃肠道综合征(RIGS)是由辐射对肠道干细胞的剂量依赖性杀伤效应引起的。本课题组的初步工作证明，使用可诱导的CRE依赖的谱系追踪，角蛋白-19(Krt19)标记的肠干细胞不同于Lgr5 CBCs，位于4区域以上。与Lgr5细胞相比，Krt19干细胞具有抗辐射能力，可以在12Gy射线照射后再生小肠。此外，来自我们小组的数据表明，间充质细胞和神经在调节干细胞和促进再生方面都很重要。因此，我们推测Krt19标记的4个肠道干细胞(ISC)在辐射损伤反应中起关键作用，并且可能受不同于Lgr5干细胞的基质因素的调节。我们将通过三个具体目标来探讨这一假设。(1)区分Lgr5和Krt19干细胞的等级关系和特征是什么？我们将使用体内谱系追踪、体外器官和基因表达研究来探索这些不同的干细胞群体。(2)神经因素在辐射损伤后ISC扩张中的作用是什么？我们将使用5-羟色胺和胆碱能信号改变的小鼠模型来评估ISCs对辐射损伤的反应。(3)肠道生长因子是如何调节辐射后小鼠ISC再生的？我们将研究已定义的肠道生长因子(如R-Spindin1和KGF)，以及其他候选利基因子，以保护和缓解钻机。目前还没有批准的医疗对策来减轻钻井平台的压力。总体而言，这项提案将调查不同ISC种群的等级、细胞命运和在再生中的作用 辐射。

DESCRIPTION (provided by applicant): The intestinal epithelium is rapidly renewed every 3-5 days from both active cycling stem cells, as well as, more quiescent stem cells. The radiation-induced gastrointestinal syndrome (RIGS) results from dose-dependent, cytocidal effects of radiation on intestinal stem cells. Preliminary work from our group has demonstrated using inducible Cre-dependent lineage tracing that Keratin-19 (Krt19) labels intestinal stem cells distinct from Lgr5+ CBCs and located above the +4 region. In contrast to Lgr5+ cells, Krt19+ stem cells are radioresistant and can regenerate the small intestine following 12Gy radiation. In addition, data from our group has shown that both mesenchymal cells and nerves are important in modulating stem cells and contributing to regeneration. Thus, it is our hypothesis that the +4 intestinal stem cell (ISC) marked by Krt19 is critical to the response to radiation injury, and maybe regulated by stromal factors distinct from that for Lgr5+ stem cells. We will explore this hypothesis through three specific aims. (1) What is the hierarchical relationship and characteristics that distinguish Lgr5+ and Krt19+ stem cells. We will use in vivo lineage tracing, in vitro organoids and gene expression studies to explore these distinct stem cell populations. (2) What is the role of neural factors in ISC expansion in response to radiation injury? We will use murine models with altered serotonin and cholinergic signaling to assess the response of ISCs to radiation injury. (3) How do intestinal growth factors regulate ISC regeneration in mice after radiation? We will examine defined intestinal growth factors (such as R-spondin1 and KGF), as well as other candidate niche factors, in the protection and mitigation of RIGS. There are currently no approved medical countermeasures to alleviate the RIGS. Overall, this proposal will investigate the hierarchy, cell fate, and role in regeneration of various ISC populations post radiation.