Stem cell-based renewal and regeneration in the intestine of a model organism

描述(申请人提供)：成人干细胞补充因正常磨损而丢失的细胞，并修复器官和组织以应对损伤。这一现象的一个很好的例子是哺乳动物的消化上皮，在正常情况下，它每3-5天完全更新一次细胞，也可以取代因辐射或细胞毒性物质(如化疗)而受损的细胞。这种快速自我更新的能力非常令人感兴趣，因为它使胃肠道系统易于患癌症，而且在特定疾病背景下(例如短肠综合征)促进更新的能力将在临床上受益。此外，对胃肠道修复的了解可能会促进干细胞技术在再生医学中的更广泛应用。然而，尽管最近取得了进展，但调控胃肠道干细胞维持、增殖和分化的分子机制尚不清楚。由于其显著的再生能力和现代分子技术的大量应用进展，平面动物是研究组织更新和干细胞生物学的极具吸引力的模式生物。在浮游生物中，被称为新生细胞的成体干细胞在正常的细胞周转和损伤后的再生过程中补充组织。作为动物最重要的器官之一，浮游动物的肠道提供了一个很好的机会来探讨损伤和细胞周转与干细胞增殖和血统限制之间的分子机制。这些实验建议利用现有的技术来识别肠道更新和再生所需的浮游动物肠道上皮细胞表达的基因。该建议的具体目的是(1)通过监测BrdU标记的新成骨细胞的分化来表征肠道组织更新和再生的动力学；(2)通过流式分选这些细胞并进行基因表达的微阵列分析，找出肠上皮细胞差异表达的基因；以及(3)在小规模的靶向RNA干扰筛选中确定在新成骨细胞增殖和分化为肠上皮细胞过程中自主和非自主发挥作用的基因。公共卫生相关性：成体干细胞通常在一生中补充和修复消化道。为了有效治疗消化系统癌症和其他疾病，需要对这一现象有更深入的了解。在这项提议中，参与这一过程的基因将在一种能够更新并完全再生其肠道的模式生物中得到识别。

DESCRIPTION (provided by applicant): Adult stem cells replenish cells lost due to normal attrition, and repair organs and tissues in response to injury. An excellent example of this phenomenon is the mammalian digestive epithelium, which completely renews its cells every 3-5 days under normal conditions, and can also replace cells lost to damage by radiation or cytotoxic substances (e.g. chemotherapy). This ability to rapidly self- renew is of great interest both because it predisposes the gastrointestinal system to cancer, and because the ability to promote renewal in specific disease contexts (e.g. short bowel syndrome) would be clinically beneficial. Additionally, an understanding of gastrointestinal repair may advance the more general application of stem cell technology to regenerative medicine. Despite recent progress, however, the molecular mechanisms regulating gastrointestinal stem cell maintenance, proliferation, and differentiation are not well understood. Because of their remarkable regenerative abilities and numerous recent advances in the application of modern molecular techniques, planarians are an attractive model organism for investigating tissue renewal and stem cell biology. In planarians, adult stem cells called neoblasts replenish tissues during normal cell turnover and during regeneration after injury. As one of the most prominent organs in the animal, the intestine of planarians offers an excellent opportunity to approach the molecular mechanisms linking injury and cell turnover to stem cell proliferation and lineage restriction. The experiments proposed capitalize on established techniques to identify genes expressed by planarian intestinal epithelial cells required for intestinal renewal and regeneration. The specific aims of this proposal are (1) to characterize the dynamics of tissue renewal and regeneration in the intestine by monitoring the differentiation of BrdU-labeled neoblasts; (2) to identify genes that are differentially expressed by intestinal epithelial cells by flow sorting these cells and conducting microarray analysis of gene expression; and (3) to identify genes that function autonomously and non-autonomously during neoblast proliferation and differentiation into intestinal epithelial cells in a small-scale, targeted RNA interference screen. PUBLIC HEALTH RELEVANCE: Adult stem cells normally replenish and repair the digestive tract throughout life. Deeper understanding of this phenomenon is required for effective treatment of digestive cancers and other diseases. In this proposal genes involved in this process will be identified in a model organism that can renew and completely regenerate its intestine.