Quantifying Changes in Neural Stem Cell Lineages in the Aging Niche

描述（由申请人提供）：本研究的目的是量化衰老对成体神经干细胞（NSCs）动力学和谱系的影响。虽然我们知道，随着年龄的增长，NSC的活动会减少，而且这种下降可能在衰老和与年龄有关的疾病中发挥作用，但仍然存在一些基本问题。随着年龄的增长，干细胞活性的哪些方面发生了变化？祖细胞群、它们在生态位内的运动和它们的增殖动力学是否有变化？祖细胞会随着衰老而改变命运，产生更多的神经胶质细胞而不是神经元，还是它们会经历衰老？另一个重要的未解决的问题是NSC活性的下降是细胞自主变化的结果还是由于干细胞生态位的老化。拟议的研究旨在解决这些重要的未解问题。我们将确定青年和老年小鼠大脑中NSCs的谱系和动态特性。这项涉及干细胞生物学家和计算机工程师的合作将集中在直接观察上——捕捉延时图像序列，显示神经干细胞在生态位内的动态及其确定的后代的产生。活细胞成像结果将用最先进的自动化软件工具进行量化和分析，用于跟踪干细胞和生成谱系树，使我们能够准确识别不同年龄的NSC行为差异。将用于胚胎NSC谱系分析的技术应用于成体系统，将使我们能够更全面地了解干细胞特性和祖细胞关系，成体谱系树的构建以及这些元素如何随年龄变化。具体而言，该研究将通过长期延时显微镜确定和比较年轻和老年小鼠心室下区（SVZ） NSCs的谱系和动态特性。它将通过将干细胞从年轻移植到老年，从老年移植到年轻SVZ，并测量移植细胞的整合、谱系和动态特性的变化，为随着年龄的增长而减少的神经发生是细胞自主的还是由于生态位的变化提供见解。此外，它将通过探索趋化因子SDF1和相应的CXCR4受体在衰老过程中的作用来研究NSC活性与年龄相关的下降的分子事件。大脑中SDF/CXCR4信号随着年龄的增长而下降；CXCR4表达的减少被认为会导致其他组织中干细胞活性的下降。在这里，我们将测量年轻人和老年人大脑中的SDF1和cxcr4水平。在年轻和老年小鼠的NSC谱系中，SDF1 /CXCR4信号通路将被特定拮抗剂或条件敲除CXCR4阻断，并分析谱系进展的变化。这项工作将有助于了解祖细胞行为的变化如何导致癌症和记忆丧失等衰老疾病，并开始确定分子靶标，以减轻成体干细胞生态位中与衰老相关的神经退行性变化。

DESCRIPTION (provided by applicant): The goal of this research is to quantify the effect of aging on the dynamics and lineage of adult neural stem cells (NSCs). While it is known that there is reduced NSC activity with aging and that this decline may play a role in aging and age-related diseases, a number of fundamental questions remain. Which aspects of stem cell activity change with aging? Are there changes in the progenitor cell population, their movements within the niche and their proliferation kinetics? Do progenitor cells switch fate with aging, making more glial cells rather than neurons or do they undergo senescence? Another important unresolved issue is whether the declines in NSC activity are the result of cell autonomous changes or due to aging of the stem cell niche. The proposed research is designed to address these important unanswered questions. We will determine the lineage and dynamic properties of NSCs in young adult and aged mouse brains. This collaborative effort involving stem cell biologists and computer engineers will focus on direct observation - capturing time-lapse image sequences showing the dynamics of NSCs within the niche and their production of identified progeny. The live cell imaging results will be quantified and analyzed with state-of-the-art automated software tools for tracking stem cells and generating lineage trees, enabling us to accurately identify differences in NSC behavior at different ages. Applying techniques developed for NSC lineage analysis in embryos to the adult system will allow a much more complete understanding of stem cell properties and progenitor relationships, of the construction of adult lineage trees and how these elements change with age. Specifically, the proposed research will determine and compare the lineage and dynamic properties of NSCs in the subventricular zone (SVZ) in young and aged mice by long-term time lapse microscopy. It will provide insight into the important question of whether decreased neurogenesis with aging is cell autonomous or is due to changes in the niche by transplanting stem cells from young to aged and from aged to young SVZ, and measuring changes in the integration, lineage and dynamic properties of the transplanted cells. Furthermore, it will investigate molecular events underlying age-related declines in NSC activity by exploring the role that the chemokine SDF1 and the corresponding CXCR4 receptor play in the aging process.SDF/CXCR4 signaling declines with age in the brain; reduced CXCR4 expression has been suggested to contribute to a decline in stem cell activity in other tissues. Here we will measure SDF1 andCXCR4 levels in young and aged brains. SDF1 /CXCR4 signaling will be blocked using a specific antagonist or conditional knockout of CXCR4 in the NSC lineage in young and aged mice and changes in lineage progression will be analyzed. This work will provide an understanding of how changes in progenitor behavior might contribute to diseases of aging such as cancer and memory loss and begin to identify molecular targets to alleviate aging- related neurodegenerative changes in the adult stem cell niche.