Hippocampal neurodifferentiation studied in young and aged animals by in vivo mi

描述（由申请人提供）：海马齿状回（DG）是成人大脑中唯一持续显示神经发生的区域，即由干细胞和祖细胞形成新的神经元。尽管进行了广泛的研究，但对成年神经发生如何促进海马功能知之甚少。我们认为，通过加深对新生神经元如何发育并整合到现有脑回路中的理解，可以获得关于这一基本问题的见解。 目前缺乏技术可视化在完整的大脑中的新生海马神经元在他们的发展时间尺度的周阻碍了调查的基本问题，如：当，如果有的话，在他们的生命历程中新生神经元达到结构稳定性？作为成年神经发生的一部分，细胞增殖、迁移和细胞死亡等大规模事件在多大程度上影响了先前存在的神经元的回路组织？动物的年龄和体力活动水平，这两个成年神经发生的调节器，如何影响这些动态过程？ 在这项工作中，我们将解决这一迫切需要的方法能够成像成人海马神经发生在活脑。我们计划利用延时光学显微内窥镜的最新技术进步，这是一种用于在组织内部数周和数月内对细胞进行成像的新方法。因此，我们的研究目标是：（1）开发一种慢性小鼠制剂，用于在数周和数月内对DG中的成年海马神经发生进行延时体内显微内窥镜成像。我们的方法使用：（a）用于脑深部细胞成像的光学显微内窥镜;（B）用于DG中延时显微内窥镜检查的慢性小鼠制剂;（c）在神经祖细胞和新生神经元中表达荧光蛋白的转基因小鼠和病毒载体。总之，这些工具将允许纵向，高分辨率双光子成像的祖细胞的细胞的详细形态，和新的和成熟的神经元在活的成年DG。(2)描述成年DG神经元的发育和结构可塑性。我们将评估新生细胞的发育和结构动力学如何受到动物年龄和身体活动的影响，通过测量新生神经元树突分支尖端的生长或收缩，其树突树的分支复杂性作为发育时间的函数，以及从亚颗粒层到颗粒层的细胞迁移的距离和速率。我们将比较这些参数之间的年轻成年和老年小鼠，在基线条件下，并在小鼠允许自愿运动。我们还将评估在何种程度上结构动力学发生在成熟的DG神经元，并取决于动物的年龄和身体活动。因此，我们的研究将初步了解成年海马体中发育中的神经元，并解决一些关于新生神经元如何在成年和衰老过程中整合到DG网络中的关键问题。 公共卫生相关性：海马体是一种对学习和记忆很重要的大脑结构，是成年人大脑中唯一持续显示神经发生的区域，即干细胞和祖细胞形成新的神经元。成年海马神经发生在衰老过程中下降，神经发生的缺陷与许多神经精神疾病有关，包括癫痫、抑郁症、精神分裂症和阿尔茨海默病。我们工作的目标是开发一种新的成像技术，用于直接可视化活体小鼠中的成年海马神经发生，然后使用该技术来研究年轻成年人和小鼠的海马之间新生神经元发育的差异，以确定特定的发育阶段作为未来干预的潜在治疗靶点。

DESCRIPTION (provided by applicant): The hippocampal dentate gyrus (DG) is the only area in the adult human brain that continually exhibits neurogenesis, the formation of new neurons from stem and progenitor cells. In spite of extensive research, little is known about how adult neurogenesis contributes to hippocampal function. We contend that insight regarding this fundamental issue can be gained by deepening our understanding of how newborn neurons develop and integrate into existing brain circuitry. The present lack of techniques for visualizing in the intact brain the newborn hippocampal neurons over their developmental time scales of weeks has stymied the investigation of fundamental questions such as: When, if ever, in their life course do newborn neurons attain structural stability? To what extent do the massive events of cell proliferation, migration, and cell death that are part of adult neurogenesis impact the circuit organization of the previously existing neurons? How do an animal's age and physical activity level, both regulators of adult neurogenesis, influence these dynamic processes? In this work we will address this pressing need for a method capable of imaging adult hippocampal neurogenesis in the live brain. We plan to capitalize on recent technological advances in time-lapse optical microendoscopy, a novel methodology for imaging cells over weeks and months deep within tissue. The goals of our research are thus to: (1) Develop a chronic mouse preparation for time-lapse in vivo microendoscopy imaging of adult hippocampal neurogenesis in the DG over weeks and months. Our approach uses: (a) Optical microendoscopes for imaging cells deep in the brain; (b) A chronic mouse preparation for time-lapse microendoscopy in the DG; (c) Transgenic mice and viral vectors to express fluorescent proteins in neural progenitors and newborn neurons. Together, these tools will permit longitudinal, high-resolution two-photon imaging of cells' detailed morphologies for progenitor cells, and new and mature neurons in the live adult DG. (2) Characterize the development and structural plasticity of neurons in the adult DG. We will assess how newborn cells' development and structural dynamics are affected by an animal's age and physical activity, by measuring the growth or retraction of newborn neurons' dendritic branch tips, the branching complexity of their dendritic trees as a function of developmental time, and distances and rates of cell migration from the sub-granular to the granular layer. We will compare these parameters between young adult and aged mice, under baseline conditions and in mice permitted voluntary exercise. We will also assess to what extent structural dynamics occurs in mature DG neurons and depends on an animal's age and physical activity. Our study will thus yield initial glimpses of developing neurons in the live adult hippocampus and address some key unanswered questions about how newborn neurons integrate into the DG network in adulthood and aging. PUBLIC HEALTH RELEVANCE: The hippocampus, a brain structure important for learning and memory, is the only area in the human adult brain that continually exhibits neurogenesis, the formation of new neurons from stem and progenitor cells. Adult hippocampal neurogenesis declines during aging, and defects in neurogenesis have been implicated in many neuropsychiatric disorders, including epilepsy, depression, schizophrenia, and Alzheimer's disease. The goals of our work are to develop a novel imaging technology for directly visualizing adult hippocampal neurogenesis in living mice, and then to use this technology to examine how newborn neuron development differs between the hippocampi of young adult and mice, towards identifying specific developmental stages as potential therapeutic targets for future interventions.