Neural stem cells in the aging brain

描述（由申请人提供）：越来越多的证据表明，成人大脑中新神经元的产生对行为、大脑修复和对治疗的反应很重要。衰老与新神经元产生的深刻下降有关，神经发生的减少可能与衰老大脑的功能受损有关。这种减少可能是由于几个因素，包括干细胞和祖细胞分裂的变化，干细胞或其后代的存活以及干细胞后代的命运改变。为了了解成年神经发生中与年龄相关的衰退的机制，有必要确定衰老大脑中分裂/分化级联反应的主要参数的变化。我们开发了一个实验平台，结合了报告小鼠系，谱系追踪技术，精确定量和计算建模，以确定干细胞分裂和命运的变化。我们用这种方法来确定抗抑郁治疗和脑损伤的神经源性靶点。此外，我们将联合收割机遗传干细胞分析与一种具有无与伦比的灵敏度和准确性的新技术--多同位素成像质谱（MIMS）相结合，用于定量分析衰老大脑中干细胞的周转和命运。由于我们的报告小鼠系标记几个非神经元组织中的干细胞和祖细胞，我们能够分析相同的个体动物在几个干细胞区室中的平行变化。该提案的主要目标是将严格的定量方法应用于干细胞谱系的问题，并确定干细胞在老化、抗抑郁治疗和损伤中的周转率和谱系的变化。 在目标1中，我们将使用报告线，单，双标记脉冲追踪分析，计算建模和MIMS来确定海马齿状回神经干细胞和祖细胞的分裂/分化级联参数的年龄相关变化。在目标2中，我们将使用多等位基因报告细胞系、基于Cre的谱系追踪和MIMS来确定干细胞命运中与年龄相关的变化。在目标3中，我们将应用遗传命运图和MIMS来确定分裂/分化级联参数的年龄相关变化以及干细胞对不同形式的抗抑郁治疗（氟西汀，电休克和运动）和诱导抑郁行为的损伤（多巴胺能神经元消融）的命运。最后，在目标4中，我们将使用遗传命运作图和MIMS来确定在一系列非神经元组织中干细胞/祖细胞的周转和命运的变化，这些组织由我们的多等位基因报告细胞系中的报告基因表达标记。总之，我们的结果和遗传工具将为研究干细胞的分裂和分化以及组织周转提供一个框架，作为一个综合的定量奋进。 公共卫生相关性：衰老与组织和器官再生能力下降有关。由于干细胞在再生和修复中起着关键作用，因此了解干细胞在衰老过程中发生了什么，为什么它们经常产生较少的后代，以及它们的命运是否会随着年龄的增长而改变，这一点很重要。在我们的建议中，我们结合联合收割机遗传，计算和光谱方法来确定衰老如何改变干细胞分裂和产生分化后代的能力，以及它如何影响抗抑郁治疗的反应。

DESCRIPTION (provided by applicant): Increasing evidence indicates that production of new neurons in the adult brain is important for behavior, brain repair, and response to therapies. Aging is associated with a profound decline in production of new neurons and decreased neurogenesis may be related to the impaired functioning of the aging brain. This decrease may be due to several factors including changes in the division of stem and progenitor cells, survival of stem cells or their progeny and altered fate of the stem cell progeny. To understand the mechanism of age-related decline in adult neurogenesis it is necessary to identify the changes in the main parameters of the division/ differentiation cascade in the aging brain. We developed an experimental platform that combines reporter mouse lines, lineage tracing techniques, precise quantitation and computational modeling to determine changes in stem cells division and fate. We used this approach to determine the neurogenic targets of antidepressant treatments and of brain injury. Furthermore, we will combine genetic stem cell analysis with a new technology of unparalleled sensitivity and accuracy, Multi-Isotope Imaging Mass Spectroscopy (MIMS), for the quantitative analysis of stem cells turnover and fate in the aging brain. Since our reporter mouse lines mark stem and progenitor cells in several non-neuronal tissues, we are in a position to analyze the same individual animals for parallel changes in several stem cell compartments. The main goal of this proposal is to apply stringent quantitative methods to the problem of stem cell lineage and to determine the changes in the turnover rates and the lineages of stem cells in response to aging, antidepressant therapies and injury. In Aim 1 we will use reporter lines, single- and double-label pulse chase analysis, computational modeling and MIMS to determine age-related changes in the parameters of the division/differentiation cascade of neural stem and progenitor cells in the dentate gyrus of the hippocampus. In Aim 2 we will use multi-allelic reporter lines, Cre-based lineage tracing, and MIMS to determine age-related changes in the fate of stem cells. In Aim 3 we will apply genetic fate mapping and MIMS to determine the age-associated changes in the parameters of the division/differentiation cascade and in the fate of stem cells in response to antidepressant treatments of different modalities (fluoxetine, electroconvulsive shock and exercise) and to injury that induces depressive behavior (ablation of dopaminergic neurons). Finally, in Aim 4, we will use genetic fate mapping and MIMS to determine changes in the turnover and fate of stem/progenitor cells in a range of non-neuronal tissues that are marked by reporter gene expression in our multi-allelic reporter lines. Together, our results and genetic tools will provide a framework for studying division and differentiation of stem cells and tissue turnover as an integrated quantitative endeavor. PUBLIC HEALTH RELEVANCE: Aging is associated with diminished ability of tissues and organs to regenerate. Since stem cells play a key role in regeneration and repair, it is important to understand what happens to stem cells during aging, why they often produce less progeny, and whether their fate changes with age. In our proposal we combine genetic, computational, and spectroscopic approaches to determine how the aging changes capacity of stem cells to divide and produce differentiated progeny and how it affects the response to antidepressant therapies.