Maintenance and Rarefaction of the Native Collateral Circulation

描述(申请人提供)：心脏、大脑和外周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。天然(预先存在的)侧支(COL)相互连接相邻的动脉树，在发生血管阻塞时发挥关键作用。在过去的25年里，研究人员一直专注于缺血性疾病中COLS外向重塑的调节机制。然而，在我们的工作之前，我们对是什么控制了健康组织中这些独特血管的数量和直径(范围)一无所知。我们已经证明，由于遗传多态性，小鼠脑和后肢的COL程度有很大的不同。此外，范围的变化对缺血组织损伤的严重程度的影响比重构的变化更大。因此，我们的发现将注意力集中在了解控制天然COL循环程度的遗传机制的重要性上。本建议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(CVRF)是否也对COL范围产生不利影响。虽然在患者中的观察表明这可能是真的，但我们在小鼠身上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(稀疏性)随年龄增加而下降，这与内皮细胞/eNOS功能障碍(ECdys)有机械联系-因此确定eNOS-NO是COLS的基本维持因素。在其他的初步研究中，我们发现COL具有显著的结构和功能特化，与一般循环中的小动脉相比，例如，面向流动的EC排列，丰富的初级纤毛(PRC)，增强的基础增殖，以及独特的基因表达谱。我们假设这种新的COL表型反映了COL所处的扰动切应力(DSS)环境，并且对于COL的持久性是必不可少的。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CVRF过早稀化的敏感性很高。目的研究遗传性脑血管紧张素转换酶(CVRF)小鼠模型是否导致脑和后肢颜色稀少，导致更严重的缺血性组织损伤。目的II将利用深入的细胞和分子分析以及有条件的细胞特异性基因打靶，验证COL ECs表达独特表型的假设，该表型对于它们在DSS环境中的持久性和对CVRF稀疏的敏感性很重要。AIM III将寻求防止或逮捕科尔稀有派别 CVRF模型使用针对EC/eNOS功能障碍和血管炎症的疗法，这些疗法已经在患者中使用，或正在进行其他适应症的临床试验。这些研究的成功结果将确定一个新的缺血性疾病的危险因素--严重程度，即胶原稀少，以及预防它的治疗方法，并确定一个新的结构/基因表达表型或标记，以区分侧支与其他血管，这是其持续性和功能所必需的。

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.