Differentiating Radio-sensitivities Among Intestinal Stem Cell Pools

描述（由申请人提供）：肠上皮每3-5天从活跃的循环干细胞和更安静的干细胞中快速更新一次。辐射诱发的胃肠道综合征（RIGS）是由于辐射对肠道干细胞的剂量依赖性、细胞杀伤作用所致。我们小组的初步工作已经证明，使用可诱导的cre依赖性谱系追踪，Keratin-19 （Krt19）标记肠干细胞与Lgr5+ CBCs不同，位于+4区域上方。与Lgr5+细胞相比，Krt19+干细胞具有放射抗性，并能在12Gy辐射后再生小肠。此外，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，我们假设Krt19标记的+4肠干细胞（ISC）对辐射损伤应答至关重要，并且可能受不同于Lgr5+干细胞的基质因子调控。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、体外类器官和基因表达研究来探索这些不同的干细胞群体。(2)神经因子在辐射损伤后ISC扩张中的作用？我们将使用血清素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)肠道生长因子如何调控辐射后小鼠ISC再生？我们将研究确定的肠道生长因子（如R-spondin1和KGF）以及其他候选生态位因子在保护和缓解rig中的作用。目前还没有批准的医疗对策来减轻rig。综上所述，本研究将探讨不同ISC群体的等级、细胞命运及其在再生中的作用

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.