Mechanisms of Intestinal Stem Cell Injury and Repair

项目摘要 这项新的R 01申请旨在确定干细胞损伤后肠粘膜修复的机制， 研究两个关键信号通路Dll 1/4-Notch信号和IGF 1-mTORC 1信号在 促进隐窝修复成体干细胞为肠上皮细胞的持续更新提供燃料。现行 理论表明，存在两种干细胞群：活性干细胞（也称为隐窝基底柱状细胞 (CBC)细胞）对于维持上皮细胞稳态和兼性干细胞（也 称为静止干细胞或储备干细胞）对于在损伤后的隐窝恢复期间补充CBC是重要的- 导致干细胞丢失。肠隐窝具有显著的可塑性，隐窝内有各种上皮细胞 能够重新编程以填充未被占据的小生境点以补充CBC干细胞库。机制 隐窝修复和兼性干细胞动员目前知之甚少。该项目旨在定义 驱动再生反应的关键生态位信号。将研究两种干细胞损伤的小鼠模型， 包括已建立的12戈伊γ-照射模型和由以下原因引起的CBC损失的新模型： 急性Notch抑制，我们在这个建议中定义。我们的初步调查结果显示这两处伤口 导致快速CBC损失，随后是过度增殖的再生反应， Notch信号通路。我们的初步研究还表明，IGF-1的表达是由损伤诱导的， mTORC 1信号传导是隐窝修复所必需的。拟开展的研究将：（1）鉴定特异性Notch配体 再生反应所需的，（2）测试潘氏细胞在再生反应中的作用，和（3） 测试IGF-1和mTORC 1信号传导对隐窝修复和兼性干细胞动员的作用。 此外，这些研究将扩大我们对肠道干细胞生态位的了解，包括关键的 上皮和间充质中的小生境细胞，对损伤作出反应以调节干细胞功能。研究 利用现有的遗传小鼠模型和药理学工具来操纵信号传导 正在研究的途径，以探测它们在成年小鼠中的功能。了解调节肠道的机制 干细胞扩增和隐窝再生对于鉴定繁殖成体干细胞关键策略是重要的 培养再生疗法以及开发肠道疾病的治疗策略 与粘膜损伤有关。

PROJECT SUMMARY This new R01 application seeks to define mechanisms of intestinal mucosal repair after stem cell injury, investigating the role of two key signaling pathways Dll1/4-Notch signaling and IGF1-mTORC1 signaling for promoting crypt repair. Adult stem cells fuel the continuous renewal of the intestinal epithelium. Prevailing theory suggests that there are two stem cell populations: active stem cells (also termed crypt base columnar (CBC) cells) important for epithelial cell maintenance during homeostasis and facultative stem cells (also termed quiescent or reserve stem cells) important for replenishing CBCs during crypt recovery after injury- induced stem cell loss. Intestinal crypts exhibit remarkable plasticity, with various epithelial cells in the crypt capable of reprogramming to fill unoccupied niche spots to replenish the CBC stem cell pool. Mechanisms of crypt repair and facultative stem cell mobilization are currently poorly understood. This project aims to define key niche signals that drive the regenerative response. Two mouse models of stem cell injury will be studied, including the well-established 12 Gy gamma-irradiation model and a new model of CBC loss resulting from acute Notch inhibition that we define in this proposal. Our preliminary findings show that these two injuries both result in rapid CBC loss followed by a hyperproliferative regenerative response associated with a surge of Notch pathway signaling. Our preliminary studies also show that IGF-1 expression is induced by injury and that mTORC1 signaling is required for crypt repair. The proposed studies will: (1) identify specific Notch ligands required for the regenerative response, (2) test the role of Paneth cells in the regeneration response, and (3) test the role of IGF-1 and mTORC1 signaling for crypt repair and facultative stem cell mobilization. Furthermore, the studies will expand our knowledge of the intestinal stem cell niche, including definition of key niche cells in the epithelium and mesenchyme that respond to injury to regulate stem cell function. The studies take advantage of available genetic mouse models and pharmacologic tools to manipulate the signaling pathways under study to probe their function in adult mice. Understanding mechanisms regulating intestinal stem cell expansion and crypt regeneration is important to identify key strategies to propagate adult stem cells in culture for regenerative therapies as well as to develop treatment strategies for intestinal diseases associated with mucosal injury.