Lesions and loss of smooth muscle cells in brain underlies small vessel disease

为了回应FOA，PAR-22-026，我们提出了一种集成的和技术/概念创新的方法来 推进我们对小脑血管功能障碍如何对大脑产生长期影响的机械性理解 并导致认知障碍。脑部小血管疾病(CSVD)占脑缺血的25% 中风和90%以上的自发性脑出血(ICH)，因此是痴呆症的主要驱动因素。 最近的研究表明，至少有四种类型的壁细胞定义了四个主要的微血管区域： 小动脉上的平滑肌细胞(SMCs)，毛细血管床小动脉后区域的收缩周细胞(PC)(即， 移行区)、远端毛细血管上的非收缩PC和小静脉上的小静脉PC。人小动脉系膜细胞的缺失 死后大脑是多因素和遗传性cSVD的共同特征，无论是否与缺血有关 中风或ICH。我们已经提供了令人信服的证据，小动脉上的SMC的丢失伴随着功能的增强 过渡带上的收缩PC相互增强而导致ICH，最近发现 临床相关小鼠大脑和视网膜移行区的小动脉SMCs和收缩PC早期丢失 NOTCH3受体功能获得或丧失突变的缺血性cSVD模型。在此基础上， 其他观察结果表明，脑小动脉中SMC的丢失是导致脑微动脉硬化的共同因素。 小动脉后移行区CSVD的发生及收缩PC性质/密度的变化 修改疾病演示。为了测试这一点，我们将探索SMC/PC损失与cSVD之间的因果关系- 相关的大脑病理和认知症状(目标1)，并确定SMC/收缩PC的丢失如何影响 综合血管功能(目标2)。为此，我们将使用现有的和新的具有条件的鼠标模型 在特定的壁细胞群体中灭活Notch3，并采用一系列强大的新技术，包括1)a 新的基于坐标的物体分析方法，能够同时量化所有可成像的参数， 包括小血管病理，在来自整个高分辨率切片的海量4D(随时间变化的3D)成像数据集中 2)一种与标记红细胞和微球相结合的新型加压视网膜制剂，用于 定量评价小血管病变对血管内压和血流的影响 以及3)超快功能超声成像，这是一种新兴的技术，可以无创地 具有高时空分辨率的小鼠全脑冠状切面中活体脑血容量的变化 决议，以阐明小脑血管病变如何影响大脑深部的脑血流调节。 大脑。我们期望，拟议的研究将有助于更好地了解深部痛的机制基础。 CSVDS的脑损害和认知障碍，并建立微动脉SMC和收缩PC作为关键的新靶点。

In response to the FOA, PAR-22-026, we propose an integrated and technologically/conceptually innovative approach to advance our mechanistic understanding of how dysfunction of small brain vessels can have long-term impacts on the brain parenchyma and cause cognitive impairment. Cerebral small vessel disease (cSVD) accounts for up to 25% of ischemic strokes and more than 90% of spontaneous intracerebral hemorrhages (ICHs), and as such is a major driver of dementia. Recent studies have shown that there are at least four types of mural cells defining four major microvascular zones: smooth muscle cells (SMCs) on arterioles, contractile pericytes (PCs) on the post-arteriole region of the capillary bed (i.e., transition zone), non-contractile PCs on distal capillaries and venular PCs on venules. Loss of arteriolar SMCs in human post-mortem brains is a feature shared by both multifactorial and inherited cSVD, whether associated with ischemic strokes or ICHs. We have provided compelling evidence that loss of SMCs on arterioles coupled with enhanced function of contractile PCs on the transition zone mutually reinforce each other to cause ICHs, and recently discovered that arteriolar SMCs and contractile PCs in the transition zone are lost early in the brain and retina of clinically relevant mouse models of ischemic cSVDs with gain- or loss-of-function mutations in the NOTCH3 receptor. On the basis of these and other observations, we propose that loss of SMCs specifically in brain arterioles is a common factor underlying the development of cSVDs and that changes in the properties/density of contractile PCs in the post-arteriole transition zone modify disease presentation. To test this, we will explore the causal relationship between the loss of SMCs/PCs and cSVD- related brain pathologies and cognitive symptoms (Aim 1) and determine how loss of SMCs/contractile PCs compromises integrative vascular functions (Aim 2). To this end, we will employ existing and novel mouse models with conditional inactivation of Notch3 in specific mural cell populations and deploy a powerful array of new techniques, including 1) a novel coordinate-based object analysis methodology capable of simultaneously quantifying all imageable parameters, including small vessel pathology, in massive 4D (3D over time) imaging datasets from high-resolution sections of the entire brain; 2) a novel pressurized retina preparation in conjunction with labeled red blood cells and microspheres for quantitatively assessing the impact of small vessel pathology on intravascular pressure and flow across different microvascular segments; and 3) ultrafast functional ultrasound imaging, an emerging technology that can non-invasively sample cerebral blood volume changes in vivo in a complete coronal section of a mouse brain with a high spatiotemporal resolution, for elucidating how small brain vessel pathologies affect cerebral blood flow regulation in deep parts of the brain. We expect that the proposed studies will contribute to a better understanding of the mechanistic basis of deep brain lesions and cognitive impairment in cSVDs and establish arteriolar SMCs and contractile PCs as critical new targets.