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

项目总结 我们对脑血管疾病如何导致痴呆症的了解主要集中在脑血管疾病的病理学上。 脑小动脉。然而，脑微静脉的病理是否也有助于脑损伤？ 血流灌注仍未得到充分的研究。临床前和临床研究表明， 小血管疾病的小静脉曲折和血管壁组成是导致血管病变的基础 认知障碍和痴呆症(VCID)和阿尔茨海默病。然而，大脑静脉的基本原理是 网络是有组织的，它们的恶化是如何导致痴呆症的，仍然不清楚。这样做的目的是 该项目利用多光子成像的最新进展来研究与年龄相关的脑功能损害 活体小鼠脑深部灰白质静脉引流。大脑白质驻留在 大脑深部区域，对痴呆症早期的血液流动障碍特别敏感。这是具有挑战性的 在体内获取这些组织，以便更好地了解白质缺陷的病因。我们的方法 通过使用体内深度双光子成像和长波长的组合来克服这个问题 激发/发射和三光子成像研究皮质灰白质微血管构筑 分别位于界面和更深的白质中。在初步研究中，我们发现血液从 深层组织完全依靠罕见的上升小静脉，称为主要皮质小静脉(PCV)。PCV 通过长而曲折的引流毛细血管延伸巨大的分支网络来收集血液。关键的，深刻的 PCV的微血管网络选择性收缩，血管密度减少，更差。 在老年小鼠(18-24个月)和成年小鼠(6-9个月)中灌流。我们最重要的假设是 PCV结构和功能的恶化是老年性深灰色血流障碍的基础 和白质。在这个项目的目标1中，我们将测试PCV显示大脑区域特异性的假设 衰老过程中结构和功能的恶化，因为白质在某些区域离小动脉输入更远 皮质较厚。在目标2中，我们将检验毛细血管周细胞功能障碍对 PCV网络的恶化。在目标3中，我们将检验以下假设：血管收缩和血流障碍 在PCV网络中，法舒地尔可以缓解，法舒地尔是一种临床使用的药物，可以减少毛细血管的收缩张力 除了小动脉。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。这个项目意义重大，因为它将：(1)推进 新的成像技术研究白质变性小鼠模型的微血管基础 VCID和阿尔茨海默病。(2)深入了解PCV的结构和功能，这是一种 白质的无特征和必要的引流系统。(3)洞察与年龄相关的周细胞 功能障碍会导致血流障碍，以及它们是否是治疗的靶点。(4)产量数据 年龄相关性脑白质血流障碍是否可接受治疗调节。

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.