Neural stem cells in the aging brain

描述(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都很重要。衰老与新神经元的产生严重减少有关，神经发生减少可能与老化大脑的功能受损有关。这一下降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，以及干细胞后代命运的改变。为了了解与年龄相关的成人神经发生衰退的机制，有必要确定衰老脑中分裂/分化级联的主要参数的变化。我们开发了一个结合了报告鼠系、谱系追踪技术、精确定量和计算建模的实验平台，以确定干细胞分裂和命运的变化。我们使用这种方法来确定抗抑郁药物治疗和脑损伤的神经源性靶点。此外，我们将把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--多同位素成像质谱仪(MIMS)相结合，用于定量分析衰老大脑中干细胞的周转和命运。由于我们的报道鼠系标记了几个非神经性组织中的干细胞和祖细胞，我们能够分析同一个体动物几个干细胞室中的平行变化。这项建议的主要目标是应用严格的定量方法来解决干细胞谱系问题，并确定干细胞的周转率和谱系在应对衰老、抗抑郁治疗和损伤时的变化。在目标1中，我们将使用报告线、单标记和双标记脉冲追逐分析、计算建模和MIMS来确定海马齿状回神经干祖细胞分裂/分化级联的参数随年龄的变化。在目标2中，我们将使用多等位基因报告系、基于CRE的谱系追踪和MIMS来确定干细胞命运的年龄相关变化。在目标3中，我们将应用遗传命运图谱和MIMS来确定在不同方式的抗抑郁治疗(氟西汀、电惊厥和运动)以及导致抑郁行为的损伤(多巴胺能神经元消融)下，干细胞分裂/分化级联参数和干细胞命运的年龄相关变化。最后，在目标4中，我们将使用遗传命运图谱和MIMS来确定干/祖细胞在一系列非神经元组织中的周转和命运的变化，这些组织以报告基因在我们的多等位报告系中的表达为标志。总而言之，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更新提供一个框架，作为一个综合的量化努力。

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.