Maintenance and Rarefaction of the Native Collateral Circulation

描述（由申请方提供）：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。原生（预先存在的）侧支（COL）互连相邻的动脉树，并在血管阻塞发生时作为旁路血管发挥关键作用。在过去的25年里，研究人员一直专注于缺血性疾病中调节COL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，小鼠大脑和后肢的COL程度变化很大。此外，程度的变化比重塑的变化对缺血性组织损伤的严重性有更大的影响。因此，我们的研究结果集中注意力的重要性，了解的遗传机制控制程度的本地COL循环。本提案的一个主要目标是确定环境因素，即心血管风险因素和疾病（CVRF）是否也对COL程度产生不利影响。虽然在患者中的观察表明这可能是真的，但我们在小鼠中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）的年龄-剂量依赖性下降，其机械地与内皮细胞/eNOS功能障碍（ECdys）联系在一起-因此将eNOS- NO鉴定为COL的基本维持因子。在其他初步研究中，我们发现与一般循环中的小动脉相比，COL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），增加的基底增殖和独特的基因表达谱。我们推测，这种新的COL表型反映了干扰的剪切应力（DSS）的环境中，COL居住，是必不可少的持久性。此外，我们假设，这种DSS环境导致加速增殖EC衰老，因此高敏感性的COL过早稀疏CVRF。目的研究CVRF基因小鼠模型是否会导致大脑和后肢COL的减少，从而导致更严重的缺血性组织损伤。AIM II将使用深入的细胞和分子分析以及条件性细胞特异性基因靶向来检验COL EC表达独特表型的假设，该表型对于COL EC在DSS环境中的持久性和对CVRF稀疏的敏感性很重要。目标III将寻求防止或阻止COL稀疏化， CVRF模型使用靶向EC/eNOS功能障碍和血管炎症的疗法，这些疗法已经用于患者或用于其他适应症的临床试验。这些研究的成功结果将定义缺血性疾病严重程度的新风险因素，即COL稀疏，以及预防它的治疗方法，并确定一种新的结构/基因表达表型或标记物，将侧枝血管与其他血管区分开来，这对侧枝血管的持续性和功能至关重要。 公共卫生相关性：虽然心脏、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，但当闭塞性疾病发作时，互连相邻动脉树的天然（预先存在的）侧支通过充当内源性旁路血管提供了第一道防线。我们的研究发现，健康小鼠的侧支血管丰富程度差异很大，导致“低程度”个体缺血性组织损伤的严重性风险大大增加，这在最近的人体研究中得到了支持。虽然我们已经确定了对这种变异有很大贡献的遗传多态性，但我们的初步研究表明，心血管危险因素，如衰老和高血压，也大大减少了侧支血管的范围，从而提出了以下建议：1）验证这一假设，2）定义负责机制，3）确定潜在的预防治疗。

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. PUBLIC HEALTH RELEVANCE: While 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 that interconnect adjacent arterial trees provide the first line of defense by acting a endogenous bypass vessels when occlusive disease strikes. Our work, which has discovered that the abundance of collaterals varies widely in healthy mice-resulting in a greatly increased risk-severity for ischemic tissue injury in "low-extent" individuals-has found support in recent human studies. While we have identified genetic polymorphisms that contribute strongly to this variation, our preliminary studies suggest that cardiovascular risk factors, such as aging and hypertension, also greatly diminish collateral extent-leading to this proposal to: 1) test this hypothesis, 2) define the responsible mechanisms, and 3) identify potential preventive therapies.