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组织特异性成体干细胞功能的年龄相关性下降是否可逆。专注于肠道，我们的初步研究表明，肠干细胞（ISC）的数量减少，在老年小鼠和人类和肠隐窝分离出老年小鼠在体外类器官测定ISC功能的功能较低。我们还发现，热量限制（CR）逆转了衰老对ISCs的影响。在哺乳动物肠道中，大多数ISC表达Lgr 5并且与潘氏细胞相邻，潘氏细胞构成干细胞细胞邻近区或"小生境"的组分。我们最近已经证明，CR在年轻的小鼠增加ISC功能，通过减少机制的雷帕霉素复合物1（mTORC1）信号传导的潘氏细胞的目标，这些影响CR可以模仿雷帕霉素（mTORC1抑制剂）。潘氏细胞和ISCs之间的这种相互作用由潘氏细胞中骨基质抗原1（Bst-1）的表达介导，Bst-1是一种产生旁分泌因子环ADP核糖（cADPR）的胞外酶。通过本建议的三个目标来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，我们将测试的假设，诱导的生态位Bst-1 CR和雷帕霉素提高ISC功能在老年小鼠（目标1），转录因子PPAR-gamma介导的潘氏细胞（目标2），和cADPR激活的信号转导介导的这种反应在ISC（目标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).