Regulation of microglial function by blood-borne factors

项目摘要：阿尔茨海默病(AD)等与年龄相关的疾病是老年人面临的紧迫问题 人口。鉴于缺乏普遍有效的治疗方法，必须开发新的方法来减少 衰老的影响，是AD发生发展的最大危险因素。最近的工作显示了年龄的年轻化- 敏感器官，包括大脑，通过暴露在年轻的血液中。我们的实验室发现有组织丢失 金属蛋白酶抑制因子2(TIMP2)的表达与增龄有关，其修复是介导衰老的关键 年轻血液对老年动物的返老还童作用。尽管有这些发现，但确切的机制和细胞 TIMP2的靶点尚未确定。目前尚不清楚TIMP2在衰老过程中的积极作用 概括到AD病理学的背景。然而，老龄化和阿尔茨海默病带来了类似的环境挑战 大脑(例如，炎症、垂死细胞的细胞碎片、有毒蛋白质)。基于小胶质细胞在脑内的作用 对碎片(如死亡细胞、淀粉样蛋白等)的快速反应，我们假设TIMP2调节小胶质细胞 功能。与这一假设一致，我们发现用TIMP2治疗减少了小胶质细胞的激活 在衰老的大脑中。当暴露在衰老和AD的碎片中时，一群小胶质细胞会患上一种疾病-- 相关的小胶质细胞(DAM)表型来应对这些挑战。这种表型最初是由 允许小胶质细胞有效地应对环境挑战，但无节制的激活可能会导致 小胶质细胞功能障碍或衰老，对周围组织造成损害。恢复有效的反应 对于限制病理来说，碎片可能是至关重要的。已发现TIMP2是DAM转录的标志 我们的初步数据表明，细胞固有的TIMP2可以调节小胶质细胞的状态。这项建议 目的研究小胶质细胞对TIMP2处理的反应以及小胶质细胞TIMP2在细胞内的内在作用。 能够在不同的病理背景下对碎片做出有效的反应。目标1将评估形态 在老年和AD病理环境中TIMP2治疗后小胶质细胞的炎症反应 以确定小胶质细胞在治疗后对损伤的反应。此外，我们将检查小胶质细胞- 用超分辨显微镜和RNAScope研究海马区神经元的相互作用。为了探测细胞- 小胶质细胞TIMP2的内在作用，AIM 2将检验小胶质细胞TIMP2恢复对 衰老与阿尔茨海默病相关病理。我们开发了一种小鼠模型，允许我们有条件地删除TIMP2 在不同环境中的小胶质细胞内。删除后，我们将通过分析以下方面的变化来检查对碎片的响应 病理、形态、细胞因子释放和小胶质细胞与神经元的相互作用。所采用的创新方法 将为TIMP2作为一种胞外蛋白在血管紧张素转换酶功能中的作用提供深入的认识。 小胶质细胞，同时也探索其活动的细胞内在效应在与衰老和 广告。表征不同病理条件下碎片的神经免疫反应可能有助于 开发延缓衰老过程的疗法，以限制神经退行性疾病的发生。

Project Summary: Age-related disorders such as Alzheimer’s disease (AD) present urgent issues to the aging population. Given the lack of universally effective treatments, novel approaches must be developed to reduce the impact of aging, the greatest risk factor for development of AD. Recent work has shown rejuvenation of age- sensitive organs, including the brain, through exposure to young blood. Our lab identified a loss of tissue inhibitor of metalloproteinase 2 (TIMP2) expression with age, and its restoration is critical in mediating the rejuvenating effects of young blood in aged animals. Despite these findings, the precise mechanism and cellular targets of TIMP2 have yet to be identified. It is currently unknown whether the positive effects of TIMP2 in aging generalize to the context of AD pathology. However, aging and AD present similar environmental challenges to the brain (e.g., inflammation, cellular debris from dying cells, toxic proteins). Based on the role of microglia in rapidly responding to debris (e.g., dying cells, amyloid, etc), we hypothesize that TIMP2 modulates microglial function. Consistent with this hypothesis, we have found that treatment with TIMP2 reduces microglial activation in the aged brain. Upon exposure to the debris of aging and AD, a subset of microglia acquires a disease- associated microglia (DAM) phenotype to respond to these challenges. This phenotype is initially protective by allowing microglia to effectively respond to environmental challenges, but unbridled activation can cause dysfunction or senescence of microglia and damage to surrounding tissue. Restoration of an effective response to debris may be critical to limit pathology. TIMP2 has been found to be a marker of the DAM transcriptional profile, and our preliminary data indicate that cell-intrinsic TIMP2 can regulate microglial state. This proposal aims to characterize microglial response to TIMP2 treatment and the cell-intrinsic role of microglial TIMP2 in enabling an effective response to debris in differing pathological contexts. Aim 1 will assess the morphological and inflammatory responses of microglia following treatment with TIMP2 in aged and AD pathological contexts to determine how microglia respond to damage following treatment. Furthermore, we will examine microglial- neuronal interactions in hippocampus using super-resolution microscopy and RNAscope. To probe the cell- intrinsic role of microglial TIMP2, Aim 2 will test the hypothesis that microglial TIMP2 rejuvenates response to aging and AD-associated pathology. We developed a mouse model that allows us to conditionally delete TIMP2 within microglia in diverse contexts. Upon deletion, we will examine response to debris by analyzing changes in pathology, morphology, cytokine release, and microglia-neuron interactions. The innovative methods employed in this proposal will provide insights into the role of TIMP2 acting as an extracellular protein on the function of microglia, while also probing cell-intrinsic effects of its activity in the context of debris associated with aging and AD. Characterization of the neuroimmune response to debris in different pathological conditions may facilitate development of therapies that slow down the aging process to limit onset of neurodegenerative diseases.