Development of New Molecular Probes for Diagnostic Imaging of Atherosclerosis

描述（由申请人提供）：需要改进的成像策略和靶向分子成像造影剂来识别、表征和监测动脉粥样硬化斑块。目前研究的主要目的是开发敏感的生物相容性分子成像探针，能够通过磁共振成像（MRI）识别和监测动脉粥样硬化斑块的进展。氧化低密度脂蛋白（oxLDL）已被确定为动脉粥样硬化斑块的发生，发展和不稳定的一个关键因素。由于OxLDL是免疫原性的，特异性结合氧化特异性表位的自身抗体已从小鼠（MDA 2和E06）和人（IK 17）中分离出来。我们最近假设，选择性靶向氧化特异性表位的分子成像探针，目前oxLDL，可能使早期在体内检测斑块容易破裂。我们已经报道，氧化低密度脂蛋白靶向钆（Gd）胶束可用于在体内MR检测小鼠动脉粥样硬化模型中的氧化丰富的斑块。然而，研究表明，存在高度的Gd生物转化和保留，这可能限制该技术的临床可转化性。目前的提案计划通过生产含有生物相容性MR标签的纳米颗粒来解决这些安全问题。由于FDA已经批准使用锰（Mn（II））螯合物和氧化铁颗粒用于MR肝脏适应症，我们假设oxLDL靶向Mn（II）胶束和oxLDL靶向脂质包被的氧化铁颗粒可以为动脉粥样硬化斑块的体内检测提供临床上可转化的生物相容性平台。目标1将集中在合成，表征，和磁共振成像的MDA 2标记的锰（II）胶束和脂质涂层的氧化铁颗粒在动脉粥样硬化小鼠的疗效。比较靶向Mn（II）胶束和氧化铁颗粒的基本原理与这两种平台相关的MR信号调节和细胞代谢/排泄的差异有关。由于可用性，选择MDA 2作为靶向部分。在目标2中，将在目标3中使用的小鼠品系中检测各种oxLDL靶向部分（MDA 2、EO 6和IK 17）的药代动力学、生物分布和MR成像功效。由于以前的放射性示踪剂研究显示抗体摄取和oxLDL沉积在动脉血管壁之间的相关性，我们假设动脉MR信号将与oxLDL含量（通过免疫组织化学测定）后，管理oxLDL靶向Mn（II）胶束和/或脂质包被的氧化铁颗粒。将基于生物分布和MR信号与oxLDL沉积的相关性来选择最佳制剂（靶向部分和Mn（II）或铁颗粒）。目的3是在动脉粥样硬化斑块进展的小鼠模型中测试最佳制剂。本研究的目的是评估这种方法检测动脉壁oxLDL沉积在饮食干预下的体内变化的能力。如果成功的话，这些MR探头可能为易损动脉粥样硬化斑块的检测和监测提供一个强大的临床可转换平台。公共卫生相关性：心血管疾病仍然是美国死亡的主要原因，动脉粥样硬化引起的心肌梗死和脑梗死是这些死亡的原因。随着对心血管疾病分子通路的深入了解，近年来心血管疾病的细胞和分子机制的研究越来越受到重视，尤其是高分辨率无创性活体分子成像技术的研究。靶向分子特异性造影剂与磁共振成像（MRI）功能的结合可以在早期斑块检测中带来最佳结果，了解疾病的分子机制并监测对治疗的反应。

DESCRIPTION (provided by applicant): Improved imaging strategies and targeted molecular imaging contrast agents are needed to allow for the identification, characterization, and monitoring of atherosclerotic plaque. The main objective of the current research proposal is to develop sensitive biocompatible molecular imaging probes that are capable of identifying and monitoring atherosclerotic plaque progression by magnetic resonance imaging (MRI). Oxidation of low-density lipoprotein (oxLDL) has been identified as a critical factor in atherosclerotic plaque initiation, progression and de-stabilization. Since OxLDL is immunogenic, autoantibodies that specifically bind oxidation-specific epitopes have been isolated from mice (MDA2 and E06) and humans (IK17). We recently hypothesized that molecular imaging probes that selectively target oxidization-specific epitopes, present on oxLDL, may enable early in vivo detection of plaque prone to rupture. We have reported that oxLDL targeted gadolinium (Gd) micelles may be used for in vivo MR detection of oxidation-rich plaques in murine models of atherosclerosis. However, it was shown that there is a high degree of Gd biotransformation and retention that may limit the clinical translatability of this technology. The current proposal plans to solve these safety issues by producing nanoparticles containing biocompatible MR labels. Since the FDA has already approved the use manganese (Mn(II)) chelates and iron oxide particles for MR liver indications, we hypothesize that oxLDL targeted Mn(II) micelles and oxLDL targeted lipid coated iron oxide particles may provide clinically translatable biocompatible platforms for in vivo detection of atherosclerotic plaque. Aim1 will focus on the synthesis, characterization, and MR efficacy of MDA2 labeled Mn(II) micelles and lipid coated iron oxide particles in atherosclerotic mice. The rationale for comparing targeted Mn(II) micelles and iron oxide particles is related to differences in the MR signal modulation and cellular metabolism/excretion associated with these two platforms. MDA2 was chosen as the targeting moiety due to availability. In Aim 2 the pharmacokinetics, biodistribution, and MR imaging efficacy of the various oxLDL targeting moieties (MDA2, EO6, and IK17) will be tested in the mouse strain to be used in Aim 3. Since previous radiotracer studies show a correlation between antibody uptake and oxLDL deposition in the arterial vessel wall, we hypothesize that the arterial MR signal will correlate to oxLDL content (as determined by immunohistochemistry) following administration of oxLDL targeted Mn(II) micelles and/or lipid coated iron oxide particles. The optimal formulation (targeting moiety and Mn(II) or iron particle) will be chosen based upon biodistribution and the correlation of the MR signal to oxLDL deposition. Aim 3 is designed to test the optimal formulation in murine models of atherosclerotic plaque progression. The goal of this aim is to evaluate the ability of this methodology to detect in vivo changes in arterial wall oxLDL deposition in response to dietary intervention. If successful, these MR probes may provide a powerful clinically translatable platform for the detection and monitoring of vulnerable atherosclerotic plaque. PUBLIC HEALTH RELEVANCE: Cardiovascular disease remains the primary cause of mortality in the United States with myocardial and cerebral infarction caused by atherosclerosis accounting for these deaths. With better understanding of molecular pathways of numerous cardiovascular diseases, the latest research has focused on cellular and molecular mechanism of the disease, more particularly to high resolution non-invasive in vivo molecular imaging. The combination of targeted molecule- specific contrast agents and the capabilities of magnetic resonance imaging (MRI) can bring optimal results in early plaque detection, understand the molecular mechanism of the disease and monitor response to treatment.