Targeting the Pial Collateral Circulation for Mitigation of Cerebral Ischemia

摘要 大血管闭塞后卒中严重程度的主要决定因素是闭塞部位和持续时间。 闭塞和侧支循环血流量。不幸的是，患者的软脑膜侧支循环变化很大。 急性缺血性卒中(AIS)后，与脑梗塞体积和出血性转移风险呈负相关 形成并直接与溶栓和取栓的疗效有关。在我们研究之前，原因的线索 这种广泛的变异在很大程度上是未知的。事实上，人们对血管生物学知之甚少。 侧支，与一般动静脉循环的血管相比。我们最近发现， 侧支在小鼠妊娠晚期通过一种独特的血管生成过程和信号通路形成，我们 称为“侧支生成”。侧支发生因遗传背景的不同而有很大差异， 结果，与人类一样，成人的侧枝循环范围和中风严重程度存在很大差异。使用遗传 作图中，我们确定了四个与侧枝循环程度变异有关的基因座，并确定了原因基因 其致病基因中最大的SNPs为新基因Rabepp2。中风遗传学的初步分析 数据集，我们发现人类RABEP2基因的多态性与急性缺血性中风的发病率有关 和AIS患者的脑梗塞面积。为了充分支持这些回顾研究和前瞻性研究， 正处于登记阶段，我们需要确定另外三个附属QTL的原因基因，如 以及其他可能存在于老鼠物种中的大效应基因座。我们也取得了初步的结果。 回答了一个长期存在的问题--能否在成人体内诱导形成额外的侧支？初步结果 表明全身缺氧和大脑中动脉闭塞都有这种作用。这两者都需要Rabep2，概括一下它的 在胚胎侧支发生中的关键作用。以下目标继续我们的总体目标，以提供更深层次的 了解这些独特而重要的侧支血管的生物学，并将发现转化为 人类和他们的临床护理。目的确定先前确定的QTL的候选基因， 利用最近开发的外交种多样性，利用Canq2、Canq3和Canq4以及额外的大效QTL 和协作性交叉参考种群。方法包括高分辨率血管造影和基因 作图、表达和电子计算机分析。AIM II将使用基因打靶来确定 在AIM I中确定的QTL评估结果的方法包括测定脑血流量、脑梗塞体积、脑功能恢复 神经功能和缺血性血管生成。AIM III将确定从头形成的机制 低氧诱导新侧支循环(NCF)后，吸入O2持续下降，大脑中动脉闭塞。 这些研究还将有助于识别驱动侧枝循环发生的关键基因，这些基因含有 这是成人侧支丰度差异很大的原因。他们还被要求支持研究 目前正在对人类的同源基因进行测试。此外，他们还将开辟一个新的基础领域 研究表明，缺血引起的NCF可能会导致治疗阻塞性疾病的新疗法。

ABSTRACT The major determinants of stroke severity after large-vessel occlusion are the location and duration of occlusion and the amount of collateral blood flow. Unfortunately, pial collateral flow varies widely in patients following acute ischemic stroke (AIS), correlating inversely with infarct volume and risk of hemorrhagic trans- formation and directly with efficacy of thrombolysis and thrombectomy. Prior to our studies, clues to the cause of this wide variation were largely unknown. In fact, much less is known about the vascular biology of collaterals, compared to vessels of the general arterio-venous circulation. We recently identified that collaterals form late in gestation in mice by a unique angiogenic process and signaling pathway, which we termed “collaterogenesis”. And that collaterogenesis varies widely due to differences in genetic background, resulting, as in humans, in large differences in collateral extent and stroke severity in the adult. Using genetic mapping, we identified four loci that link to variation in collateral extent, and determined that the causal gene and its causal SNPs at the largest locus is the novel gene, Rabep2. In preliminary analyses of stroke genetics datasets, we have found that polymorphisms in human RABEP2 link to the incidence of acute ischemic stroke and infarct size in AIS patients. To fully power these retrospective studies and also prospective studies that are in the enrollment phase, we need to identify the causal genes for the three additional collateral QTL, as well as other large-effect loci likely extant in the mouse species. We have also obtained preliminary results answering a long-standing question—can additional collaterals be induced to form in adults. Preliminary results show that systemic hypoxia and MCA occlusion both do so. And that both require Rabep2, recapitulating its critical role in collaterogenesis in the embryo. The following Aims continue our overall goal to provide a deeper understanding of the biology of these unique and important collateral vessels, and to translate the findings to humans and their clinical care. Aim I will identify the candidate genes underlying the previously identified QTL, Canq2, Canq3 and Canq4, and additional large-effect QTL, using the recently developed Diversity Outbred and Collaborative Cross reference populations. Methods include high-resolution angiography and genetic mapping, expression and in silico analyses. Aim II will use gene targeting to ascertain the causal genes at the QTL identified in Aim I. Methods to assess outcome include determination of CBF, infarct volume, recovery of neurological function and ischemic angiogenesis. Aim III will determine mechanisms of de novo formation of new collaterals (NCF) induced by hypoxia following sustained decrease in inspired O2 and by MCA occlusion. These studies will also aid identifying the key genes that drive collaterogenesis that harbor variants that underlie the wide variation in collateral abundance in the adult. They are also required to power studies currently underway to test the orthologous genes in humans. In addition, they will open up a new area of basic research, NCF induced by ischemia, which may lead to novel therapies to treat obstructive disease.