Regulation of the Intestinal Stem Cell Niche in Aging

描述（由申请人提供）：衰老领域的一个基本问题是，与年龄相关的组织特异性成体干细胞功能下降是否可逆。针对肠道，我们的初步研究表明，老年小鼠和人类的肠道干细胞（ISC）数量减少，并且从老年小鼠中分离的肠隐窝在体外ISC功能类器官试验中功能较差。我们还发现，卡路里限制（CR）逆转了衰老对ISCs的影响。在哺乳动物肠道中，大多数ISCs表达Lgr5并与Paneth细胞相邻，构成干细胞邻域或“生态位”的一个组成部分。我们最近证明，年轻小鼠的CR通过降低Paneth细胞中雷帕霉素复合物1 （mTORC1）信号传导的机制靶点来增强ISC功能，并且CR的这些作用可以被雷帕霉素（一种mTORC1抑制剂）模仿。Paneth细胞和ISCs之间的相互作用是通过Paneth细胞中骨基质抗原1 （Bst-1）的表达介导的，Bst-1是一种产生旁分泌因子环ADP核糖（cADPR）的外酶。通过本提案的三个目标确定这一过程中的机制步骤将增加我们对CR如何保护生物体免受与年龄相关的组织功能下降的理解。具体来说，我们将验证CR和雷帕霉素诱导小生境Bst-1促进老年小鼠ISC功能的假设（Aim 1）；转录因子ppar - γ介导Paneth细胞的这种反应（Aim 2）；cadpr激活的信号在ISCs中介导这种反应（Aim 3）。

DESCRIPTION (provided by applicant): A fundamental question in the aging field is whether the age-related decline in tissue-specific adult stem cell function is reversible. Focused on the gut, our preliminary studies suggest that intestinal stem cell (ISC) numbers are reduced in old mice and humans and that intestinal crypts isolated from old mice are less functional in an in vitro organoid assay of ISC function. We also find that calorie restriction (CR) reverses the effects of aging on ISCs. In the mammalian intestine, a majority of ISCs express Lgr5 and are adjacent to Paneth cells, which constitute a component of the stem cell cellular neighborhood or "niche". We have recently demonstrated that CR in young mice augments ISC function by reducing mechanistic target of rapamycin complex 1 (mTORC1) signaling in Paneth cells, and that these effects of CR can be mimicked by rapamycin (an mTORC1 inhibitor). This interaction between Paneth cells and ISCs is mediated by expression in Paneth cells of bone stromal antigen 1 (Bst-1), an ectoenzyme that produces the paracrine factor cyclic ADP ribose (cADPR). Identification of the mechanistic steps in this process through the three aims of this proposal wil increase our understanding of how CR protects an organism against the age-related decline in tissue function. Specifically, we will test the hypotheses that induction of niche Bst-1 by CR and rapamycin boosts ISC function in old mice (Aim 1); that the transcription factor PPAR-gamma mediates this response in Paneth cells (Aim 2); and that cADPR-activated signaling mediates this response in ISCs (Aim 3).