Optical Interrogation of Venular Function in Cerebral Gray and White Matter

项目摘要 我们对脑微循环的理解大多来自于对小动脉灌注的研究。血液流出 在确定通过大脑的血液流量方面起着同样重要的作用，因为所有血液 进入大脑必须通过小静脉排出脑微静脉的结构和功能可以发生改变 在脑血管疾病中的作用非常显著。临床前和临床研究已经证明， 阿尔茨海默病和阿尔茨海默病患者微静脉迂曲度和血管壁成分的改变 与疾病有关的痴呆与小动脉相比，小静脉的流速较慢， 使它们在疾病期间更容易止血、血栓形成和免疫细胞粘附。 总的来说，这些因素表明小静脉是脑灌注的脆弱部位， 替补演员这个项目的重点是主皮质小静脉（PCV），一个小静脉的子集，从 大脑表面进入最深层的皮层和下面的白色物质。虽然PCV较少 与较小的皮质小静脉相比，它们常见，在更深处延伸大量水平突出的分支。 组织，表明在深层皮质和邻近白色物质束的灌注中起关键作用。但 几乎没有关于PCV的结构、生理和灌注区域的信息。大脑白色 物质对血流不足特别敏感，并在阿尔茨海默病的早期阶段退化， 阿尔茨海默病相关的痴呆症。了解白色物质及其附近的灌注调节 在理解这种白色物质变性的基础上，纤维束将是至关重要的。我们的核心假设是 PCV是深层皮质层和下层白色物质的主要引流系统。目标1： 将通过使用体内双光子成像和三光子成像来测试这一假设， 测量小鼠脑中皮质层6及其相邻的白色物质束中毛细血管流是如何排出的， 分别这些活动将在成年（3-9个月）和老年小鼠（18-24个月）中进行，以测试 次要假设是年龄与PCV结构和功能的恶化相关。在目标2中，我们将 我们将通过测量光血栓形成的程度， 单个PCV的阻塞影响通过相邻的穿透性小动脉进入皮质的血流。我们将进一步 使用组织学来评估由单次闭塞产生的灰色和白色物质中的缺氧组织的体积 PCV。这个项目是有意义的，因为它解决了白色中小静脉灌注的未充分研究的主题 使用新的体内成像方法。它进一步奠定了必要的实验基础， 微静脉功能障碍作为脑血流和白色物质受损机制的未来研究 阿尔茨海默病和阿尔茨海默病相关痴呆的退化。

Project Summary Much of our understanding of brain microcirculation comes from studies on arteriolar perfusion. Blood efflux through venules plays an equally important role in determining blood flow through the brain, since all blood entering the brain must exit via venules. The structure and function of cerebral venules can change dramatically during cerebrovascular disease. Preclinical and clinical studies have demonstrated marked alterations in venule tortuosity and vascular wall composition during Alzheimer’s disease and Alzheimer’s disease-related dementias. Compared to arterioles, the slower flow and distinct endothelial biology of venules makes them more susceptible to hemostasis, thrombosis, and immune cell adhesion during disease. Collectively, these factors point to venules as a site of vulnerability in cerebral perfusion that remains highly understudied. This project focuses on principal cortical venules (PCVs), a subset of venules that descend from the brain surface into the deepest layers of cortex and underlying white matter. Although PCVs are less common compared to smaller cortical venules, they extend massive, horizontally projecting branches in deeper tissues, suggesting a critical role in perfusion of deep cortex and adjacent white matter tracts. However, there exists almost no information on the structure, physiology and perfusion territories of PCVs. Cerebral white matter is particularly sensitive to blood flow deficit and degenerates in early stages of Alzheimer’s disease and Alzheimer’s disease-related dementias. Understanding the regulation of perfusion in and near white matter tracts will be critical in understanding the basis of this white matter degeneration. Our central hypothesis is that PCVs are the main drainage system for deep cortical layers and the underlying white matter. In Aim 1, we will test this hypothesis by using emergent deep in vivo two-photon imaging and three-photon imaging to measure how capillary flow is drained in cortical layer 6 and its adjacent white matter tract in the mouse brain, respectively. These activities will be performed in adult (3-9 months) and aged mice (18-24 months) to test a secondary hypothesis that age is associated with deterioration in PCV structure and function. In Aim 2, we will we will quantify the radius of cortical tissue dependent upon PCV drainage by measuring how photothrombotic occlusion of a single PCV affects flow into the cortex through neighboring penetrating arterioles. We will further use histology to assess the volume of hypoxic tissue in gray and white matter created by occlusion of single PCVs. This project is significant because it addresses the understudied topic of venular perfusion in white matter using novel in vivo imaging approaches. It further establishes an experimental foundation needed for future research on venular dysfunction as a mechanism of impaired cerebral blood flow and white matter degeneration in Alzheimer’s disease and Alzheimer’s disease-related dementias.