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

作为对FOA PAR-22-026的回应，我们提出了一种综合的技术/概念创新方法， 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理解 导致认知障碍脑小血管疾病（cSVD）占缺血性脑血管病的25%。 中风和超过90%的自发性脑内出血（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： 小动脉上的平滑肌细胞（SMC），毛细血管床的小动脉后区域上的收缩性周细胞（PC）（即， 过渡区），远端毛细血管上的非收缩性PC和小静脉上的小静脉PC。人小动脉平滑肌细胞的丢失 死后大脑是多因素和遗传性cSVD共同的特征，无论是否与缺血性 中风或ICH。我们已经提供了令人信服的证据表明，小动脉平滑肌细胞的损失与功能的增强相结合， 在过渡区的收缩PC相互加强，导致ICH，最近发现， 临床相关小鼠的脑和视网膜中移行区的小动脉SMC和收缩PC早期丢失 在NOTCH 3受体中具有获得或丧失功能突变的缺血性cSVD模型。在此基础上， 通过其他观察，我们提出，脑小动脉中SMC的丢失是导致脑缺血的一个共同因素。 cSVD的发展以及小动脉后移行区收缩性PC的性质/密度的变化 改变疾病表现。为了验证这一点，我们将探索SMC/PC丢失与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的损失如何影响 整合血管功能（目标2）。为此，我们将采用现有的和新的小鼠模型与条件 Notch 3在特定壁细胞群中的失活，并部署了一系列强大的新技术，包括1） 能够同时量化所有可成像参数的新颖的基于坐标的对象分析方法， 包括小血管病理学，在来自整个组织的高分辨率切片的大量4D（随时间变化的3D）成像数据集中， 脑; 2）与标记的红细胞和微球结合的新型加压视网膜制剂， 定量评估小血管病变对不同血管内压力和流量的影响， 微血管段;和3）超快功能超声成像，一种新兴的技术，可以非侵入性 在小鼠大脑的完整冠状切片中，在体内样本脑血容量变化具有高时空 分辨率，用于阐明小脑血管病变如何影响脑深部的脑血流调节， 个脑袋我们希望，拟议的研究将有助于更好地理解的机制基础，深 脑损伤和认知障碍，并建立小动脉SMC和收缩PC作为关键的新目标。

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.