Hemodynamics of Cerebral Arteriovenous Malformations

描述(申请人提供)：脑动静脉畸形(BAVM)患者有颅内出血(ICH)的风险。大约20%的患者因为侵入性治疗的风险过高而得不到治疗，而对未破裂病变的治疗也变得有争议。目前还没有治疗脑动静脉畸形的特效药物。我们利用激活素样激酶(Alk1)和endoglin(Eng)的纯合子条件性缺失开发了新的成年型小鼠模型，这两个基因是一种家族性bAVM(遗传性出血性毛细血管扩张)的致病基因。这些模型的表型模仿了人类bAVM的关键方面。AIMS 1和AIMS 2将解决这两个基因的功能丧失如何导致基本相同的人类bAVM表型，这一点目前尚不清楚，而AIMS 3将开发急需的bAVM治疗方法。目的1研究Alk1或Eng基因功能的丧失如何改变对血管壁结构完整性至关重要的信号。对于Aim 1a(体外)和im 1b(体内)，最主要的假设是：(1)ALK1或ENG缺失并伴随着血管内皮生长因子刺激导致脑微血管内皮细胞Notch配体Delta-like Ligand-4(DLL4)的表达减少；(2)DLL4的减少导致血小板衍生生长因子-B(PDGFB)信号的缺失；(3)因此，壁细胞募集受到损害。目的2着重于基因功能丧失所起作用的细胞基因座。我们假设Alk1或Eng缺陷的骨髓(BM)来源的内皮细胞(EC)和/或巨噬细胞(Mo)足以诱导异型增生(bAVM表型)。我们将测试BM来源的EC(Aim 2a)或BM来源的Mo(Aim 2b)是否足以诱导不典型增生。在目标2c中，我们将测试两种细胞类型之间的协同作用，在目标2d中，我们将使用细胞特异性的Notch信号的过表达(在Mo中的Notch1或在EC中的DLL4)来挽救Alk1或Eng缺失的影响。AIM 3将提供一种有前景的药物的临床前数据，该药物的选择部分基于我们在AIM 1中的假设。我们的数据表明，沙利度胺降低了异型增生的严重程度，并稳定了血管壁。由于沙利度胺的不良反应众所周知，我们将测试来那度胺，一种新的、毒性较低的类似物。在目标3a中，我们假设来那度胺优于沙利度胺。在目标3b中，我们将通过在我们的Alk1缺失模型中构建剂量-抑制曲线来确定来那度胺的疗效。在Aim 3c中，为了确保更广泛的适用性，我们将使用接近最大有效剂量的来那度胺在Eng缺失模型中进行测试。这些临床前数据可用于支持早期临床试验。这项拟议的工作将继续努力阐明bAVM的发病机制，并改善对bAVM患者的护理。

DESCRIPTION (provided by applicant): Brain arteriovenous malformation (bAVM) patients are at risk of intracranial hemorrhage (ICH). Roughly 20% of patients are not offered treatment because of excessive risk of invasive therapy, and treatment of unruptured lesions has become controversial. There are no specific medical therapies to treat bAVMs. We have developed novel adult-onset mouse models using homozygous conditional deletion of Activin-like kinase (Alk1) and Endoglin (Eng), the causative genes for a familial form of bAVM (Hereditary Hemorrhagic Telangiectasia). The models have phenotypes mimicking key aspects of human bAVM. Aims 1 and 2 will address how loss of function of these two genes results in essentially the same human bAVM phenotype, which is not currently understood, while Aim 3 will develop much-needed therapy for bAVM. Aim 1 examines how loss of Alk1 or Eng gene function alters signaling that is crucial for structural integrity of the vascular wall. For Aim 1a (in vitro) and im 1b (in vivo), the overarching hypothesis is that: (1) ALK1 or ENG deletion with VEGF stimulation leads to reduced expression of the Notch ligand, Delta-like ligand-4 (DLL4), in brain microvascular endothelial cells; (2) decreased DLL4 results in deficient platelet-derived growth factor-B (PDGFB) signaling; (3) consequently, mural cell recruitment is impaired. Aim 2 focuses on the cellular loci where the loss of gene function acts. We hypothesize that Alk1 or Eng-deficient bone marrow (BM)-derived endothelial cells (EC) and/or macrophages (Mo) are sufficient to induce dysplasia (bAVM phenotype). We will test whether BM-derived EC (Aim 2a) or BM-derived Mo (Aim 2b) are sufficient to induce dysplasia. In Aim 2c, we will test for synergism between the two cells types, and in Aim 2d, we will use cell-specific overexpression of Notch signaling (Notch1 in Mo or Dll4 in EC) to rescue the effects of Alk1 or Eng deletion. Aim 3 will provide pre-clinical data on one promising drug that was selected, in part, based on our hypotheses in Aim 1. Our data suggest that thalidomide decreases the severity of dysplasia and stabilizes the vascular wall. Because of thalidomide's well-known adverse effect profile, we will test lenalidomide, a new, less toxic analogue. In Aim 3a, we hypothesize that lenalidomide is superior to thalidomide. In Aim 3b, we will determine efficacy of lenalidomide by constructing dose-inhibitory curves in our Alk1 deletion model. In Aim 3c, to insure broader applicability, we will test lenalidomide in our Eng deletion model using a near-maximally effective dose. These pre-clinical data can be used to support early-phase clinical trials. The proposed work will underpin continued efforts to elucidate the mechanisms of bAVM pathogenesis and improve care for bAVM patients.