Understanding the impact of capillary obstructions on brain angio-architecture and function

了解毛细血管阻塞对脑血管结构和功能的影响

• 批准号: RGPIN-2019-06399
• 负责人: Brown, Craig
• 金额: $ 3.42万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=738889
• 关键词: Understanding; impact; capillary; obstructions; brain

Background. Capillaries are the primary site of nutrient and gas exchange and the brain contains kilometers of capillaries to meet its energetically demanding needs. Capillary networks are assumed to be critical for maintaining brain function since decrements in cognition that occur with aging and certain neurodegenerative diseases correlate with the loss of brain capillaries. One underappreciated aspect of the brain's capillary network is that it is prone to obstruction, even in healthy animals. Recent studies have shown that at any given moment, a small fraction of capillaries are obstructed. This is not surprising since capillaries are inherently narrow, low pressure tubes that must pass relatively large blood cells. While the majority of these obstructions clear within seconds to minutes, a fraction of capillaries remain obstructed for much longer. We have recently shown that 30% of capillaries with persistent obstructions are pruned over 21 day period and are not compensated for by sprouting new capillaries. This led to a prolonged perturbation in local flow blood. Using this information, we were able to model and predict capillary loss with aging in healthy mice which fell closely in line with empirical data. In light of these new findings, we still do not have a good mechanistic understanding of how these capillary obstructions are cleared, or even what impact they have on brain function. Preliminary findings and general hypothesis. Pilot data from my lab indicate that increasing neural activity through environmental enrichment or pharmacology enhances obstruction clearance and reduces capillary loss. Based on these findings, we hypothesize that bouts of increased neural activity, through an as of yet understood circuit or molecular mechanism, is critical for clearing obstructions and maintaining capillary blood flow in the brain. Methodological approach. We will image naturally occurring capillary obstructions or induce them with injection of fluorescent microspheres, which blocks a small fraction of capillaries and do not lead to detectable cell death. The mouse brain will be imaged in vivo or post-mortem in brain sections to assess obstruction clearance and capillary pruning rates. We will use pharmacological, genetic (viruses, Cre-Lox mice), optical and chemo-genetic approaches to test our 3 broad aims: Aim 1: Define the role of neuronal activity in clearing capillary obstructions and what specific neural circuits are involved. Aim 2: Understand how neural activity dislodges obstructions by influencing capillary tone and blood flow. Aim 3: Determine the impact/significance of capillary obstructions on brain function. Significance. This research will provide fundamental knowledge regarding the impact of micro-circulatory obstructions on brain function and the mechanisms that regulate their removal, so that new strategies can be devised to maintain a healthy microcirculatory system and preserve brain function throughout life.

背景毛细血管是营养和气体交换的主要场所，大脑包含数公里长的毛细血管，以满足其能量需求。毛细血管网络被认为是维持大脑功能的关键，因为随着年龄的增长和某些神经退行性疾病发生的认知能力下降与大脑毛细血管的损失有关。大脑毛细血管网络的一个未被充分认识的方面是，即使在健康的动物中，它也容易阻塞。最近的研究表明，在任何给定的时刻，一小部分毛细血管被阻塞。这并不奇怪，因为毛细血管本质上是狭窄的低压管，必须通过相对较大的血细胞。虽然大多数这些障碍物在几秒钟到几分钟内清除，但一小部分毛细血管仍然阻塞更长时间。我们最近发现，30%的毛细血管在21天内被修剪，并且没有通过发芽新的毛细血管来补偿。这导致局部血流的长期扰动。利用这些信息，我们能够模拟和预测健康小鼠中毛细血管损失随年龄的变化，这与经验数据非常一致。根据这些新发现，我们仍然没有很好的机制来理解这些毛细血管阻塞是如何被清除的，甚至它们对大脑功能有什么影响。 初步调查结果和一般假设。我实验室的试验数据表明，通过环境富集或药理学增加神经活动可以增强阻塞清除率并减少毛细血管损失。基于这些发现，我们假设，通过一个尚未理解的电路或分子机制，增加神经活动的发作对于清除阻塞和维持大脑中的毛细血管血流至关重要。 方法论方针。我们将对自然发生的毛细血管阻塞进行成像，或者通过注射荧光微球来诱导它们，荧光微球会阻塞一小部分毛细血管，不会导致可检测到的细胞死亡。小鼠脑将在体内或死后在脑切片中成像，以评估阻塞清除率和毛细血管修剪率。我们将使用药理学，遗传学（病毒，Cre-Lox小鼠），光学和化学遗传学方法来测试我们的3大目标：目标1：定义神经元活动在清除毛细血管阻塞中的作用以及涉及哪些特定的神经回路。 目的2：了解神经活动如何通过影响毛细血管张力和血流来清除阻塞物。 目的3：确定毛细血管阻塞对脑功能的影响/意义。 意义这项研究将提供有关微循环障碍对大脑功能的影响以及调节其清除机制的基础知识，以便制定新的策略来维持健康的微循环系统并在整个生命中保持大脑功能。