Characterization of Telomerase Expressing Intestinal Stem Cells

描述(申请人提供)：长期以来，人们一直认为，像骨髓这样的自我更新组织是通过缓慢循环(基本上处于静止状态)的干细胞维持的，一旦激活，就会产生快速循环的祖细胞。最近，人们已经证实，也存在一个休眠干细胞亚群(很少循环)，它们似乎主要作为组织损伤后的强大干细胞发挥作用。相比之下，在正常情况下，休眠的干细胞被认为对组织稳态的贡献微乎其微。相比之下，持续自我更新的肠道上皮似乎在基础条件下至少由两个独立的干细胞群体维持，这两个干细胞要么快速循环，要么缓慢循环。使用两个品系的报告小鼠，我们现在表明，表达端粒酶的细胞代表了一种罕见的休眠干细胞群体，它们对肠道损伤具有高度的抵抗力。因此，端粒酶并不代表ISCs的通用标记物，而是标记具有强大再生能力的ISCs亚群。有趣的是，我们的初步数据表明，表达端粒酶的ISCs能够快速循环Lgr5+细胞，这表明了肠隐窝内的谱系等级以及损伤后干细胞可能被替换的潜在机制。这一建议试图进一步确定mTert表达细胞在肠道内稳态和损伤反应中的作用，并研究静止和自我更新的分子基础。这些目标的成功完成将有助于深入了解ISCs所利用的关键调控途径，并可能为患有炎症性肠病、短肠综合征和肠癌等胃肠道疾病的患者带来新的治疗策略。 公共卫生相关性：缓慢循环的组织干细胞为再生医学和组织修复带来了巨大的希望，尽管由于缺乏明确的生物标志物，在包括肠道在内的许多组织中仍然难以捉摸。我们采用了一种创新的策略，使用转基因小鼠来识别、分离和遗传操作肠道干细胞。这项工作可能会为小肠综合征、炎症性肠病和肠癌等肠道疾病带来新的治疗策略。

DESCRIPTION (provided by applicant): It has long been held that self-renewing tissues such as bone marrow are maintained by slowly cycling (largely quiescent) stem cells, which upon activation give rise to rapidly cycling progenitor cells. Recently, it has been established that a subpopulation of dormant stem cells (that rarely cycle) are also present, which seem to function primarily as potent stem cells following tissue injury. Under normal conditions, by comparison, dormant stem cells are thought to contribute only minimally to tissue homeostasis. The continuously self-renewing intestinal epithelium, in contrast, appears to be maintained by at least two separate stem cell populations under basal conditions, which are either rapidly cycling or slowly cycling. Using two strains of reporter mice, we now show that telomerase-expressing cells represent a rare population of dormant stem cells that are highly resistant to intestinal injury. As such, telomerase does not represent a universal marker for ISCs but rather marks a subpopulation of ISCs with potent regenerative capacity. Intriguingly, our preliminary data indicate that telomerase-expressing ISCs give rise to rapidly cycling Lgr5+ cells suggesting a lineage hierarchy within the intestinal crypt as well as a potential mechanism by which stem cells may be replaced following injury. This proposal seeks to further define the role of mTert-expressing cell in intestinal homeostasis and in response to injury as well as to examine the molecular basis for quiescence and self-renewal. The successful completion of these goals will provide an in depth understanding of the key regulatory pathways utilized by ISCs and potentially lead to novel therapeutic strategies for patients with gastrointestinal conditions such as inflammatory bowel disease, short bowel syndrome and intestinal cancer. PUBLIC HEALTH RELEVANCE: Slowly cycling tissue stem cells hold great promise for regenerative medicine and tissue repair, though have remained elusive in many tissues including intestine due to a lack of definitive biomarkers. We have employed an innovative strategy using transgenic mice that allows for the identification, isolate and genetic manipulate of intestinal stem cells. This work may give rise to novel therapeutic treatment strategies for intestinal diseases such as small bowel syndrome, inflammatory bowel disease and intestinal cancers.