Brain Drain: In Vivo Optical Interrogation of Venular Function in Gray and White Matter

项目摘要 我们对脑血管疾病如何导致痴呆症的理解主要集中在脑血管疾病的病理学上。 脑小动脉然而，脑微静脉病变是否也有助于脑损害， 灌注仍然是高度不足的研究。临床前和临床研究表明， 小血管疾病中微静脉迂曲度和血管壁成分是血管对血管病变贡献的基础 认知障碍和痴呆症（VCID）和阿尔茨海默病。然而，大脑静脉如何运作的基本原理 网络是有组织的，它们的恶化如何导致痴呆症，仍然不清楚。这个目标 该项目是利用多光子成像的最新进展来研究与年龄相关的损伤， 在体小鼠脑深灰色和白色物质的静脉引流。大脑的白色物质位于 脑深部区域，并且对痴呆症早期阶段的血流不足特别敏感。是具有挑战性 以在体内接近该组织，从而可以更好地理解白色物质缺陷的病因。我们的方法 通过使用体内深度双光子成像与长波长成像的组合克服了这个问题 激发/发射和三光子成像研究皮质灰白质微血管 界面和更深的白色物质中。在初步研究中，我们发现血液从 更深的组织完全依赖于称为主皮质小静脉（PCV）的罕见的上行小静脉。PCV 通过延伸具有长而曲折的引流毛细血管的巨大分支网络来收集血液。关键是，深度 PCV的微血管网络选择性收缩，血管密度降低， 与成年小鼠（6-9个月）相比，在老年小鼠（18-24个月）中灌注。我们的过度假设是 PCV结构和功能的恶化是与年龄相关的深灰色血流障碍的基础 和白色物质。在本项目的目标1中，我们将测试PCV表现出脑区域特异性的假设， 老化过程中结构和功能的退化，因为白色物质距离区域中的小动脉输入更远 皮层更厚在目标2中，我们将检验毛细血管周细胞功能障碍有助于 PCV网络的恶化。在目标3中，我们将检验血管收缩和血流障碍 法舒地尔是一种临床使用的药物，可以降低毛细血管的收缩张力， 还有小动脉一种去除法舒地尔靶点rho激酶的遗传策略，特别是在脑毛细血管中 周细胞将补充药理学方法。该项目意义重大，因为它将：（1）促进 新的成像技术，以研究小鼠模型中白色物质变性的微血管基础， VCID和阿尔茨海默病。(2)深入了解PCV的结构和功能， 白色物质的无特征的和基本的排水系统。(3)提供关于年龄相关的周细胞 功能障碍导致血流障碍，以及它们是否是治疗靶点。(4)产量数据 白色物质中年龄相关的血流损伤是否适合治疗调节。

PROJECT SUMMARY Much of our understanding of how cerebrovascular disease contribute to dementia focuses on the pathology of brain arterioles. However, whether pathology of cerebral venules also contribute to impairment of cerebral perfusion remains highly understudied. Preclinical and clinical studies have demonstrated marked alterations in venule tortuosity and vascular wall composition in small vessel diseases that underlie Vascular contributions to Cognitive Impairment and Dementia (VCID) and Alzheimer’s disease. Yet, the fundamentals of how brain venous networks are organized, and how their deterioration contributes to dementia, remain obscure. The goal of this project is to leverage recent advances in multi-photon imaging to investigate age-related impairment of venous drainage in deep gray and white matter of mouse brain in vivo. Cerebral white matter resides in deep brain regions and is particularly sensitive to blood flow deficit in early stages of dementia. It is challenging to access this tissue in vivo such that the etiology of white matter deficits can be better understood. Our approach overcomes this issue by using a combination of in vivo deep two-photon imaging with long wavelength excitation/emission and three-photon imaging to study microvasculature at the cortical gray-white matter interface and in deeper white matter, respectively. In preliminary studies, we found that blood drainage from deeper tissues rely exclusively on rare ascending venules, termed principle cortical venules (PCVs). PCVs collect blood by extending massive branching networks with long, tortuous draining capillaries. Critically, deep microvascular networks of PCVs were selectively constricted, reduced in vascular density, and more poorly perfused in aged mice (18-24 months) compared to adult mice (6-9 months). Our over-arching hypothesis is that deterioration of PCV structure and function is the basis for age-related blood flow impairment in deep gray and white matter. In Aim 1 of this project, we will test the hypothesis that PCVs exhibit brain region-specific deterioration in structure and function during aging, as white matter is more distant from arteriolar input in regions with thicker cortex. In Aim 2, we will test the hypothesis that dysfunction of capillary pericytes contributes to deterioration of PCV networks. In Aim 3, we will test the hypothesis that vasoconstriction and flow impairment in PCV networks can be alleviated by fasudil, a clinically-used drug that can reduce contractile tone in capillaries in addition to arterioles. A genetic strategy to remove fasudil’s target, rho kinase, specifically in brain capillary pericytes will complement the pharmacological approach. This project is significant because it will: (1) Advance novel imaging technologies to study the microvascular basis of white matter degeneration in mouse models of VCID and Alzheimer’s disease. (2) Provide insight into the structure and function of PCVs, which are an uncharacterized and essential drainage system for white matter. (3) Provide insight on how age-related pericyte dysfunction contributes to blood flow impairment, and whether they are a therapeutic target. (4) Yield data on whether age-related flow impairment in white matter is amenable to therapeutic modulation.