Role of Endothelial Progenitor Cells in vascular Aging and Calcification

描述（由申请人提供）：骨质疏松症和血管疾病影响着大量的老年人，越来越多的证据表明这两种疾病密切相关。动物和人类的数据都表明骨质疏松症与血管疾病和钙化有关。此外，血管钙化的过程似乎与正常骨形成过程中使用的途径非常相似。循环内皮祖细胞（EPCs）在内皮损伤后的血管修复中发挥着重要作用。我们最近的研究表明，通过对骨相关蛋白骨钙素（OCN）的染色评估，血管疾病患者表达成骨表型的EPCs的比例要高5- 8倍，这使我们提出了一个整体的新概念，即通过循环EPCs表达成骨表型可能至少部分解释了随着年龄增长和动脉粥样硬化发生的血管钙化增加。目前，利用多种PI机制的多学科建议（Lerman博士[血管疾病，心脏病学]和Khosla博士[骨代谢，内分泌学]），以及血管生物学专家（Simari博士）作为合作研究者的帮助下，我们将在我们的三个具体目标的背景下检验这一假设：使用来自心导管插管患者的纯化EPCs，验证与正常对照受试者相比，来自已确定的CAD患者的循环EPCs表达成骨“转录体”（即多种骨相关基因/途径），并且在体外形成矿化结节和/或增强血管平滑肌细胞矿化的能力增加的假设。目的2：在使用小鼠模型的体内研究中，验证了与AP染色阴性的EPCs相比，表达成骨表型（通过成骨细胞标记物AP染色定义）的EPCs局部递送导致皮下骨形成（Aim 2a）和血管钙化（Aim 2b）增加的假设。目的3：在接受冠状动脉导管插管的非阻塞性CAD患者的临床研究中，验证通过全身循环EPCs表达成骨/间充质标志物（OCN、AP、Stro-1）与早期动脉粥样硬化（由内皮功能障碍定义）和血管钙化（通过血管内超声[IVUS]的敏感方法评估）相关的假设（目的3a）。这些成骨EPCs被冠状动脉循环消耗（Aim 3b）。因此，提出的研究使用多学科方法测试新的假设。此外，这些研究的结果可能对我们理解血管钙化的机制以及血管和骨代谢之间日益增加的病理生理联系具有重要意义。

DESCRIPTION (provided by applicant): Osteoporosis and vascular disease affect large numbers of aging individuals, and there is increasing evidence that the two disorders are closely related. Both animal and human data indicate that osteoporosis is associated with vascular disease and calcification. Moreover, the process of vascular calcification appears to involve pathways very similar to those utilized during normal bone formation. Circulating endothelial progenitor cells (EPCs) are now increasingly recognized as playing an important role in initiating vascular repair in response to endothelial injury. Our recent demonstration that patients with vascular disease have a 5- to 8-fold greater percentage of EPCs expressing an osteogenic phenotype, as assessed by staining for the bone- related protein, osteocalcin (OCN), has led us to propose the overall novel concept that expression of an osteogenic phenotype by circulating EPCs may explain, at least in part, the increase in vascular calcification that occurs with aging and in the setting of atherosclerosis. In the present, multi-disciplinary proposal utilizing the multiple PI mechanism (Dr. Lerman [Vascular Disease, Cardiology] and Dr. Khosla [Bone Metabolism, Endocrinology]), along with the help of an expert in Vascular Biology (Dr. Simari) as Co-Investigator, we will test this hypothesis within the context of our three Specific Aims: Aim 1: Using purified EPCs from patients undergoing cardiac catheterization, test the hypotheses that, as compared to normal control subjects, circulating EPCs from patients with established CAD express an osteogenic "transcriptosome" (i.e., multiple bone-related genes/pathways) and have an increased ability to form mineralized nodules and/or enhance mineralization of vascular smooth muscle cells in vitro. Aim 2: In in vivo studies using murine models, test the hypotheses that that local delivery of EPCs expressing an osteogenic phenotype (defined by staining for the osteoblastic marker, AP), as compared to EPCs negative for AP staining, leads to increases in both subcutaneous bone formation (Aim 2a) and vascular calcification (Aim 2b).and Aim 3:In clinical studies in patients with non-obstructive CAD undergoing coronary cardiac catheterization, test the hypotheses that the expression of osteogenic/mesenchymal markers (OCN, AP, Stro-1) by systemically circulating EPCs correlates with early atherosclerosis (as defined by endothelial dysfunction) and with vascular calcification (as assessed by the sensitive method of intravascular ultrasound [IVUS]) (Aim 3a), and that these osteogenic EPCs are being consumed by the coronary circulation (Aim 3b). The proposed studies thus test novel hypotheses using a multidisciplinary approach. Moreover, the results of these studies are likely to have significant implications for our understanding of the mechanisms initiating vascular calcification as well as the increasing pathophysiological link between the vasculature and bone metabolism. PUBLIC HEALTH RELEVANCE: Aging is associated with osteoporosis and with vascular (blood vessel) disease. In addition, patients with osteoporosis (who have reduced bone) have an increased risk of vascular calcification, which is associated with formation of bone-like structures in blood vessels and with heart attacks and strokes. The proposed work focuses on the role of circulating cells which likely arise from the bone marrow in initiating vascular calcification as opposed to normal repair. These studies should help us better understand how vascular calcification occurs, and perhaps ways of modifying the process into a more normal repair process, which would have important implications for the prevention and treatment of heart disease with aging.