Hemodynamics of Cerebral Arteriovenous Malformations

描述（由申请人提供）：脑动静脉畸形（AVM）患者有破裂和颅内出血（ICH）的风险。其发病机制尚不清楚，由于缺乏动物模型，研究进展严重受阻。目前还没有药物可以直接治疗房颤或降低自发性破裂的风险。唯一的选择是切除、栓塞和放疗，所有这些都可能带来很大的风险。为了研究AVM的潜在发病机制，需要病变表型的替代模型。为此，我们开发了一种可量化的替代表型，可以代表AVM形成的早期阶段，我们称之为血管发育不良（血管扩张，畸形）。我们使用病毒介导的局灶性脑VEGF刺激内啡肽（ENG）或激活素样激酶1 （ALK1）单倍不足的小鼠。这些动物显示畸形和扩大的微血管结构。该方法的基础是人类观察到病变组织中VEGF表达增加，以及散发性AVM与ENG或ALK1突变患者相似。目的1：血流动力学改变有助于发育不良反应。静脉高压和高血管内流速是临床疾病中血管环境的重要组成部分，但这种变化如何导致病变形成或进展尚不清楚。我们将测试增加流量和静脉压力的影响，以及它们之间产生发育不良的相互作用。在VEGF刺激的大脑中，我们假设杂合的ENG或ALK1小鼠会对血流增加和/或静脉压力增加表现出增加的发育不良反应。目的2:ENG缺乏引起的血管发育不良取决于骨髓源性细胞（BMDC）。根据初步数据，我们假设是ENG单倍体BMDC不足驱动了VEGF刺激后的发育不良反应。亚目标将使用ICAM-1缺陷（-/-）小鼠作为受体，干扰ENG BMDC向血管生成病灶的募集，以证明BMDC募集的减少减轻了发育不良反应；并研究ENG骨髓中的造血干细胞是否是该反应的主要组成部分。目的3：使用ENG和ALK1细胞外结构域的下游信号的局灶性缺失导致血管发育不良。与对照组相比，切除的AVM组织显示可溶性ENG （sENG）的数量增加。我们假设局灶性过表达sENG或可溶性ALK1 (sALK1)，与VEGF一起，将模拟局灶性脑VEGF刺激后ENG和ALK1小鼠的脑表型。这些研究将提供更好的理解替代血管表型的决定因素。这项工作将允许开发一种动物模型来测试与新疗法开发相关的机制假设，这些新疗法可以有益地改变avm的自然史。

DESCRIPTION (provided by applicant): Brain arteriovenous malformation (AVM) patients are at risk of rupture and intracranial hemorrhage (ICH). The etiopathogenesis is unknown and research progress is critically hampered by the lack of animal models. There is no medical therapy available to directly treat AVMs or decrease the spontaneous rupture risk. The only options are resection, embolization and radiotherapy, all of which may pose significant risk. To study potential mechanisms for AVM pathogenesis, surrogate models of the lesion phenotype are needed. To that end, we have developed a quantifiable surrogate phenotype that may represent early stages of AVM formation, which we term vascular dysplasia (dilated, dysmorphic vessels). We use viral-mediated focal brain VEGF stimulation of mice with either endoglin (ENG) or activin-like kinase 1 (ALK1) haploinsufficiency. These animals display dysmorphic and enlarged microvascular structure. The approach is grounded on human observations of increased VEGF expression in lesional tissue and the similarity of sporadic AVM to those seen in patients with ENG or ALK1 mutations. Aim 1: Altered hemodynamics contributes to the dysplastic response. Venous hypertension and high intravascular flow rates are a prominent part of the vascular environment in clinical disease but how such changes contribute to lesion formation or progression is poorly understood. We will test the effect of increased flow and venous pressure, and their interaction to produce dysplasia. In the VEGF- stimulated brain, we hypothesize that mice heterozygous for either ENG or ALK1 mice will show an increased dysplastic response to increased flow and/or increased venous pressure. Aim 2: Vascular dysplasia from ENG deficiency is contingent on bone marrow derived cells (BMDC). Based on preliminary data, we hypothesize that it is the ENG haploinsufficient BMDC driving the dysplastic response after VEGF stimulation. Sub-aims will use ICAM-1 deficient (-/-) mice as recipients to interfere with ENG BMDC recruitment to the angiogenic focus, to demonstrate that reduction of BMDC recruitment mitigates the dysplastic response; and to investigate whether the hematopoietic stem cells in ENG bone marrow are the primary component of the response. Aim 3: Focal abrogation of downstream signaling using extracellular domains of ENG and ALK1 results in vascular dysplasia. Resected AVM tissue displays an increased amount of soluble ENG (sENG), compared to control brain. We hypothesize that focal overexpression of sENG or soluble ALK1 (sALK1), in tandem with VEGF, will mimic the brain phenotype observed in ENG and ALK1 mice after focal brain VEGF stimulation. These studies will provide better understanding of the determinants of the surrogate vascular phenotype. The work will allow development of an animal model to test mechanistic hypotheses that are pertinent to development of novel therapeutics that can beneficially alter the natural history of AVMs.