Maintenance and Rarefaction of the Native Collateral Circulation

描述（由申请人提供）：心脏、大脑和周围肢体的闭塞性血管疾病是美国发病率和死亡率的主要原因。原生（预先存在的）侧支（COLs）连接邻近的动脉树，并在发生血管阻塞时作为旁路血管发挥重要作用。在过去的25年里，研究者们一直致力于研究在缺血性疾病中介导COLs向外重塑的机制。然而，在我们的工作之前，我们对控制健康组织中这些独特血管的数量和直径（范围）的因素一无所知。我们已经表明，由于遗传多态性，小鼠脑和后肢的COL程度差异很大。此外，程度的变化比重塑的变化对缺血性组织损伤的严重程度的影响更大。因此，我们的发现将注意力集中在理解控制天然冷循环程度的遗传机制的重要性上。本提案的一个主要目标是确定环境因素，即心血管危险因素和疾病（CVRFs）是否也对COL程度产生不利影响。虽然对患者的观察表明这可能是正确的，但我们对小鼠的初步研究强烈支持这一新的假设：衰老导致COL密度和直径（稀薄）的年龄剂量依赖性下降，这与内皮细胞/eNOS功能障碍（ECdys）有机制联系，因此确定eNOS- NO是COL的必要维持因子。在其他初步研究中，我们发现，与一般循环中的小动脉相比，COLs具有显著的结构和功能特化，例如，流动导向的EC排列，丰富的初级纤毛（PRC），增加的基础增殖和独特的基因表达谱。我们假设这种新的COL表型反映了COLs所处的受干扰剪切应力（DSS）环境，并对其持续存在至关重要。此外，我们假设这种DSS环境导致增殖性EC衰老加速，因此COLs对CVRFs的过早稀薄具有高易感性。目的：确定CVRFs基因小鼠模型是否会引起脑和后肢的冷变性，从而导致更严重的缺血性组织损伤。AIM II将通过深入的细胞和分子分析以及有条件的细胞特异性基因靶向，测试COL ECs表达独特表型的假设，这对于它们在DSS环境中的持久性和对CVRFs的敏感性很重要。第三项目标将设法防止或制止在非洲的毒品走私

DESCRIPTION (provided by applicant): Occlusive vascular disease of the heart, brain and peripheral limbs is the primary cause of morbidity and mortality in the US. Native (pre-existing) collaterals (COLs) interconnect adjacent arterial trees and function critically as bypass vessels i vascular obstruction occurs. Over the past 25 years investigators have focused on mechanisms mediating outward remodeling of COLs in ischemic disease. However, until our work nothing was known about what controls the number and diameter (extent) of these unique vessels in healthy tissue. We have shown that COL extent in murine brain and hindlimb varies widely due to genetic polymorphisms. Moreover, variation in extent has a greater impact on the severity of ischemic tissue injury than does variation in remodeling. Our findings have thus focused attention on the importance of under-standing the genetic mechanisms controlling extent of the native COL circulation. A major goal of the present proposal is to determine if environmental factors, ie, cardiovascular risk factors and disease (CVRFs), also adversely affect COL extent. While observations in patients suggest this could be true, our preliminary studies in mice strongly support this novel hypothesis: Aging causes an age-dose-dependent decline in COL density and diameter (rarefaction) that mechanistically links to endothelial cell/eNOS dysfunction (ECdys)-thus identifying eNOS- NO as an essential maintenance factor for COLs. In other preliminary studies we have found that COLs have remarkable structural and functional specializations, compared to arterioles in the general circulation, e.g., a flow-oriented EC alignment, abundant primary cilia (PRC), increased basal proliferation, and a unique gene expression profile. We hypothesize that this novel COL phenotype reflects the disturbed shear stress (DSS) environment in which COLs reside and is essential for their persistence. Furthermore, we postulate that this DSS environment causes accelerated proliferative EC senescence, and thus high susceptibility of COLs to premature rarefaction by CVRFs. Aim I will determine if genetic mouse models of CVRFs cause COL rarefac- tion in brain and hindlimb, leading to more severe ischemic tissue injury. AIM II will test the hypothesis that COL ECs express a unique phenotype, important for their persistence in a DSS environment and sensitivity to rarefaction by CVRFs, using in-depth cellular and molecular analyses, and conditional cell-specific gene targeting. Aim III will seek to prevent or arrest COL rarefaction in CVRF models using therapies that target EC/eNOS-dysfunction and vascular inflammation that are already in use patients or in clinical trials for other indications. Successful outcome of thes studies will define a new risk factor for ischemic disease-severity, ie, COL rarefaction, and therapeutic approaches to prevent it, and identify a novel structural/gene expression phenotype or marker that distinguishes collaterals from other vessels and which is essential for their persistence and function.