Molecular pathogenesis and treatment of brain arteriovenous malformation

描述（由申请人提供）：脑动静脉畸形（BAVM）可导致卒中和癫痫，目前尚无有效治疗方法。BAVM是异常动静脉（AV）分流，不认为会自发消退，但容易发生危险的破裂。BAVM发病机制的细胞和分子基础仍然是个谜。我们的长期目标是阐明BAVM的发病机制，并确定新的治疗靶点，以改善这种疾病。我们的总体策略是采取跨学科方法，融合尖端的小鼠遗传学和成像技术，以确定在BAVM发病机制中通常调节AV分化的关键分子途径（如Notch信号传导）的功能。我们已经报道了一个可靠的BAVM转基因小鼠模型，其中组成型活性Notch 4（Notch 4 *）特异性地在内皮中表达，从而在未成熟小鼠中增强BAVM的标志。此外，发育中大脑中生长最快的区域，可能是血管生成最多的区域，最容易受到Notch 4 * 效应的影响，这表明血管生成是BAVM形成的基础。在严重受影响的小鼠中抑制Notch4* 表达导致神经系统症状逆转和疾病恢复，这表明当分子原因被去除时，BAVM样病变可以在动物中消退。我们还报道了Notch活性在人BAVM的内皮中增加，表明Notch信号传导可能在人类疾病中充当分子介导剂。在此，我们假设Notch4* 在血管生成过程中抑制毛细血管数量增加，从而促进毛细血管直径的扩大，这启动并维持催化BAVM形成的AV分流。我们的具体目标是阐明Notch4* 介导的小鼠BAVM样病变的发病、进展和消退的机制。我们将联合收割机将我们的BAVM小鼠模型与先进的双光子成像相结合，以获得活脑中细胞分辨率的4D血管形态和血液速度数据。我们定制的双光子显微镜是脑血管成像的最佳选择，使这项创新研究成为可能。目的1研究Notch4* 诱导小鼠BAVM样病变的血管生成机制。目的2检查作为Notch4* 在脑内皮中传播Notch信号传导的潜在机制的侧向诱导。目的3确定Notch4* 抑制后AV分流消退的细胞机制。本研究的成功完成将在概念上推进我们对BAVM发病机制的细胞和分子机制的理解，并有助于建立BAVM知识和治疗的新范式。我们建立的双光子高分辨率成像研究活体动物中BAVM的发展将是BAVM研究的一项重大技术创新。 公共卫生相关性：脑动静脉畸形（BAVM）是动脉和静脉之间的异常连接，可导致中风和癫痫。目前还没有有效的治疗BAVM的方法，传统上认为BAVM不会消退，尽管最近的证据表明消退是可能的。该提案旨在确定BAVM形成和消退的分子途径，希望确定治疗这种疾病的新治疗靶点。

DESCRIPTION (provided by applicant): Brain arteriovenous malformations (BAVMs) can cause stroke and epilepsy and have no effective treatment. BAVMs are abnormal arteriovenous (AV) shunts that are not believed to regress spontaneously, but rather are prone to dangerous rupture. The cellular and molecular basis of BAVM pathogenesis remains enigmatic. Our long-term objectives are to elucidate the mechanisms of BAVM pathogenesis and to identify novel therapeutic targets to ameliorate this disease. Our general strategy is to take a cross-disciplinary approach fusing cutting-edge mouse genetics and imaging technologies to determine the function of critical molecular pathways that normally regulate AV differentiation, such as Notch signaling, in the pathogenesis of BAVM. We have reported a faithful transgenic mouse model of BAVMs, in which expression of constitutively-active Notch4 (Notch4*) specifically in endothelium elicits hallmarks of BAVMs in immature mice. Furthermore, the areas within the developing brain which grow most rapidly, likely the most angiogenic, were most susceptible to Notch4* effects, suggesting that angiogenesis underlies BAVM formation. Repression of Notch4* expression in severely affected mice resulted in a reversal of neurologic symptoms and recovery from the illness, suggesting that BAVM-like lesions can regress in animals when the molecular cause is removed. We have also reported that Notch activity is increased in the endothelium of human BAVMs, suggesting that Notch signaling may act as a molecular mediator in the human disease. Here we hypothesize that Notch4* during angiogenesis inhibits a capillary number increase, thus promoting the enlargement of capillary diameter, which initiates and sustains AV shunts that catalyze BAVM formation. Our specific aims are designed to elucidate the mechanisms of Notch4*-mediated onset, progression, and regression of BAVM-like lesions in mice. We will combine our mouse model of BAVM with advanced 2-photon imaging to obtain 4D vascular morphology at cellular resolution and blood velocity data in living brains. Our custom-built 2-photon microscope, optimal for cerebral vascular imaging, makes this innovative study possible. Aim1 Examine the angiogenic mechanism by which Notch4* elicits BAVM-like lesions in mice. Aim2 Examine lateral induction as a potential mechanism by which Notch4* propagates Notch signaling in cerebral endothelium. Aim3 Determine the cellular mechanism underlying the regression of AV shunting upon Notch4* repression. Successful completion of this study will conceptually advance our understanding of the cellular and molecular mechanisms of BAVM pathogenesis and help establish new paradigms in the knowledge and treatment of BAVMs. Our establishment of 2-photon high resolution imaging to study BAVM development in living animals will be a major technological innovation for BAVM research at large. PUBLIC HEALTH RELEVANCE: Brain arteriovenous malformations (BAVMs) are abnormal connections between arteries and veins that can cause stroke and epilepsy. There is currently no effective treatment for BAVMs, which are conventionally believed to not regress, although recent evidence suggests regression is possible. This proposal is designed to determine the molecular pathways underlying BAVM formation and regression, with the hope of identifying novel therapeutic targets to treat this disease.