Regulation of the Intestinal Stem Cell Niche in Aging

描述(由申请人提供)：老龄化领域的一个基本问题是，与年龄相关的组织特异性成人干细胞功能的下降是否可逆。我们的初步研究集中在肠道，初步研究表明，老年小鼠和人类的肠道干细胞(ISC)数量减少，从老年小鼠分离的肠腺在体外器官类ISC功能测试中功能较差。我们还发现，卡路里限制(CR)可以逆转衰老对ISCs的影响。在哺乳动物的肠道中，大多数ISCs表达Lgr5，并与Paneth细胞相邻，Paneth细胞构成干细胞邻域或“小生境”的组成部分。我们最近在幼鼠身上证明了CR通过减少Paneth细胞中雷帕霉素复合体1(MTORC1)信号的机械靶点来增强ISC的功能，并且这种作用可以被雷帕霉素(mTORC1抑制剂)所模拟。Paneth细胞和ISCs之间的这种相互作用是通过在Paneth细胞中表达骨基质抗原1(BST-1)来实现的，BST-1是一种产生旁分泌因子环腺苷二磷酸核糖(CADPR)的胞外酶。通过这项提议的三个目标确定这一过程中的机械性步骤将增加我们对CR如何保护有机体免受与年龄相关的组织功能下降的理解。具体地说，我们将测试以下假设：CR和雷帕霉素诱导的NICE BST-1增强老年小鼠的ISC功能(Aim 1)；转录因子PPAR-Gamma在Paneth细胞中介导这一反应(Aim 2)；以及cADPR激活的信号在ISCs中介导这一反应(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).