MRI contrast for molecular and cellular imaging of the brain

用于大脑分子和细胞成像的 MRI 对比

• 批准号: 8557065
• 负责人: Alan Koretsky
• 金额: $ 269.07万
• 依托单位: NATIONAL INSTITUTE OF NEUROLOGICAL DISORDERS AND STROKE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8557065
• 关键词: Adult; Affect; Animals; Binding; Biological Assay; Biological Process; Blood - brain barrier anatomy; Brain; Calcium; Calcium Channel; Cell physiology; Cells; Clinical; Complex; Contrast Media; Cytoplasmic Granules; Detection; Development; Disease; Effectiveness; Endocytosis; Endosomes; Enzymes; Exposure to; Gene Expression; Generations; Goals; Gold; Hour; Human; Image; Imaging Techniques; Immune; Immunologic Surveillance; In Vitro; Inflammation; Injection of therapeutic agent; Interneurons; Ions; Iron; Isotopes; Label; Lead; Life; Ligands; Location; Lysosomes; Magnetic Resonance Imaging; Manganese; Measures; Metals; Microfabrication; Modeling; Molecular; Monitor; Neurons; Odors; Particle Size; Peripheral; Phase; Polymers; Population; Positron-Emission Tomography; Pre-Clinical Model; Process; Property; Rattus; Relaxation; Reporter; Reporting; Resolution; Rodent; Shapes; Silicon Dioxide; Solutions; Structure; Synapses; T-Lymphocyte; Techniques; Time; Tissues; Transferrin; Translating; Transplantation; Virus Diseases; Work; base; biomaterial compatibility; cell motility; deprivation; in vivo; interest; iron oxide; manganese chloride; migration; molecular imaging; molecular/cellular imaging; nanoparticle; nanosized; nerve stem cell; neuron development; novel; olfactory bulb; particle; receptor; response; sensor; subventricular zone; success; voltage

There is rapidly increasing interest in developing molecular imaging approaches that enable traditional radiological imaging techniques to obtain a wide range of information about molecular and cellular processes that occur in normal and diseased tissue. A range of information is considered important such as the ability to monitor cell migration, the development of reporters that enable imaging of gene expression, the development of robust strategies to image receptors, and the development of environmentally sensitive agents that can be used to detect the presence of specific enzymes or monitor changes in ion status. The long term goals of this work are to develop strategies that enable MRI contrast that is sensitive to a wide range of molecular and cellular processes. This work builds on over 15 years of work where we have demonstrated the first MRI strategy for detecting gene expression, the first MRI approach for monitoring a surrogate of calcium influx, the first MRI approach for performing neuronal track tracing, and the first MRI approach for monitoring the migration of single cells in vivo. These all represented initial reports by any radiological imaging technique which enabled these processes to be measured. These techniques are finding widespread application to imaging pre-clinical models of a broad range of diseases. Over the past year we have made progress in all of the specific aims. Aim 1: Develop iron oxide based contrast for labeling and imaging the migration of endogenous neural stem cells. Over the past few years we have demonstrated the unique advantages of micron sized iron oxide particles for MRI of specific cells. Single cells can be detected and indeed, single particles within single cells can be detected. The main paradigm for MRI of cell migration is to label cells ex vivo and monitor migration after transplantation into an animal. These studies have traditionally required very efficient labeling using nano sized particles. The ability to detect a single particle enables inefficient labeling strategies. In particular, over the past few years we have demonstrated that injection of particles into the ventricles of the rat brain enables particles to be taken up by neural precursors in the subventricular zone and MRI can monitor the migration of cells to the oflactory bulb. Over the past year we have completed a study to determine if daily exposure to odor for two weeks affects the migration of these new cells. The only significant effect was an increase in number of new neurons in the mitral cell layer of the olfactory bulb. These cells have been shown to be simular to granule layer interneurons. We have begun to monitor the response to odor deprivation using naris occlusion. In addition, we are measuring the migratory rates of cells to determine if these rates are ever modulated. We are extending our ability to image the migration of single cells through the entire brain to study immune brain interactions in a model of virus infection. This work has required working out effective strategies to label T cells, a population of cell that has been very difficult to label. This offers the unique potential to follow the low level peripheral immune surveillance that occurs in the normal adult brain as well as any changes due to inflammation or degeneration. Aim 2: Apply microfabrication techniques to manufacture unique metal structures that may be valuable for MRI contrast. Iron oxide particles commonly used for MRI are very potent contrast agents enabling detection of single mciron sized particles. However, due to bulk phase manufacture of particles they are not very uniform and they do not contain very high content of metal. A solution to this problem is to use modern microfabrication techniques to manufacture metal based, micron sized contrast agents. To begin this work we have explored a variety of approachs to microfabrication oof MRI contrast agents. Over the past few years we have shown that double dougnut and cylinder structures offer unique advantages for distinguishing particles. Microfabriaction of simple iron discs lead to 10 times more potent contrast than presently available particles. Over the past year wein order to translate this work to tracking cells we have developed strategies to effectively gold coat the particles enbaling stability and biocompatibility in living cells. Furthermore, we have demonstrated that we can accurately locate these microfabricated particles to accuracy abotu a facotr of two higher than than the pixel resolution enabling very high determination of the location. This will enable tracking of particles or cell loaded particles to higher resolution than is available from standard MRI. Finally, we have explored new shapes that give interesting MRI properties. Aim 3: Develop novel delivery mechanisms to extend the applicability of manganese enhanced MRI. Over the past ten years we have demonstrated the remarkable utility of the manganese ion for MRI contrast. Manganese ion enters cells on ligand or voltage gated calcium channels and so can be used as an MRI agent to monitor calcium influx. Once inside of neurons, manganese will move in an anterograde direction and cross functional synapses enabling neuronal networks to be imaged with MRI. Finally, manganese given systemically gives cytoarchitectural information about the rodent brain. These successes have us interested in broadening the ways in which manganese ion can be delivered to cells. Over the past couple of years we have made transferrin-manganese complexes. When bound to transferrin manganese is a poor MRI contrast agent. However, when transferrin is taken up by cells it can release manganese which is then trapped intracellularly. Thus, transferrin manganese is an agent that monitors the successful endocytosis of the transferrin by its receptor. We have demonstrated the same effects with MnOxide based nanoparticles. At pH 7 MnO is insoluble and a very weak contrast agent. At low pH, as found in endosomes/lysosomes these particles dissolve greatly increasing MRI relaxation effects. We have completed studies that show that a silica coat on these particles delays dissolution for up to four hours both in vitro and in vivo. Particles injected into the brain had slower rates of contrast development and neuronal tracing then did injection of MnCl2. This opens the possibility of making coatings that can be enzymatically degraded enabling specific in vivo assay of these enzymes. We have demonstrated another approach to makin Mn nanoparticles using block co-polymer synthesis. The first generation of these agents have very high relaxivities and the relaxivity can be modulated. Finally, we have begun to explore ways to translate the advantages of Manganese enhanced MRI to human use one makes use of manganese postiron emitting isotopes that will enable PET to obtain similar information that can be obtained with manganese enhanced MRI. Aim 4: Develop strategies that enable cellular processes to alter the relaxivity of MRI contrast agents. In specific aim 3 we demonstrated a way in which a normal biological process (endocytosis of transferrin-Mn or MnO particles) can alter the effectiveness of an MRI contrast agent. It would be very exciting to find ways in which this can occur which are sensitive to other biological processes. To this end we have begun to explore ways in which the microfabricated particles produced under Aim 2 can be modulated. Over the past year we have confirmed that the microfabricated particles can be made into a pH sensor . The strategy used is generalizable to sense many other processes. The block co-polymer agents offer many possibilities for making environmentally sensitive MRI agents and these will be explored over the next year.

人们对开发分子成像方法的兴趣迅速增加，这些方法使传统的放射学成像技术能够获得有关正常组织和患病组织中发生的分子和细胞过程的广泛信息。 一系列信息被认为是重要的，例如监测细胞迁移的能力，能够成像化基因表达的记者的发展，可用于形象受体的强大策略的发展以及可用于检测特定酶的存在或监测离子状态变化的环境敏感药物的发展。 这项工作的长期目标是制定策略，以使MRI对比对广泛的分子和细胞过程敏感。 这项工作建立在超过15年的工作基础上，我们证明了第一种检测基因表达的MRI策略，这是监测钙涌入的替代物的第一种MRI方法，这是执行神经元跟踪的第一种MRI方法，也是监测VIVO中单细胞迁移的第一种MRI方法。 所有这些都代表了任何放射成像技术的初始报告，该技术使这些过程得以测量。 这些技术正在发现广泛应用多种疾病的临床前模型。 在过去的一年中，我们在所有具体目标方面取得了进步。 目标1：开发基于氧化铁的对比度，用于标记和成像内源性神经干细胞的迁移。 在过去的几年中，我们证明了特定细胞MRI的微米大小氧化铁颗粒的独特优势。 可以检测到单个细胞，实际上，可以检测到单个细胞内的单个颗粒。 细胞迁移MRI的主要范式是将细胞在体内标记并监测移植到动物后的迁移。 传统上，这些研究需要使用纳米尺寸颗粒进行非常有效的标记。 检测单个粒子的能力可实现效率低下的标记策略。特别是，在过去的几年中，我们已经证明，将颗粒注射到大鼠脑的心室中，使脑室中的神经前体可以吸收颗粒，而MRI可以监测细胞向肠道鳞茎的迁移。在过去的一年中，我们已经完成了一项研究，以确定每天暴露于两周的气味是否会影响这些新细胞的迁移。唯一的显着影响是嗅球二尖瓣细胞层中新神经元的数量增加。 这些细胞已被证明与颗粒层中间神经元相似。我们已经开始使用Naris闭塞来监测对气味剥夺的反应。 此外，我们正在测量细胞的迁移率，以确定这些速率是否曾经调制过。 我们正在扩展我们对单个细胞在整个大脑中迁移的迁移的能力，以研究病毒感染模型中的免疫脑相互作用。 这项工作需要制定有效的策略来标记T细胞，T细胞是一个很难标记的细胞群。 这提供了遵循正常成人大脑以及由于炎症或变性引起的任何变化的低水平外周免疫监测的独特潜力。 AIM 2：应用微型制造技术来制造可能对MRI对比有价值的独特金属结构。 通常用于MRI的氧化铁颗粒是非常有效的对比剂，可检测单个McIron尺寸颗粒。 但是，由于粒子的散装相生产，它们不是很均匀，并且不包含很高的金属含量。 解决此问题的一种解决方案是使用现代的微加工技术来生产基于金属的微米大小对比剂。 为了开始这项工作，我们探讨了多种微生物MRI对比剂的方法。在过去的几年中，我们已经证明双道齿和圆柱体结构为区分颗粒提供了独特的优势。 简单铁盘的小纤维导致比目前可用的颗粒高10倍。 在过去的一年中，Wein命令将这项工作转化为跟踪细胞，我们已经开发了有效金涂层活细胞中颗粒的颗粒和生物相容性的策略。此外，我们已经证明，我们可以准确地定位这些微生物颗粒，以准确地abotu A facotr高于比像素分辨率，从而可以非常高的位置确定位置。 与标准MRI相比，这将使颗粒或细胞负载颗粒的分辨率更高。 最后，我们探索了具有有趣的MRI属性的新形状。 AIM 3：开发新型的输送机制，以扩展锰增强MRI的适用性。 在过去的十年中，我们证明了MRI对比度的锰离子具有出色的效用。 锰离子进入配体或电压门控钙通道上的细胞，因此可以用作MRI剂来监测钙涌入。 一旦进入神经元，锰将沿顺行向移动，并交叉功能突触，使神经元网络能够使用MRI成像。 最后，锰从系统地提供有关啮齿动物大脑的细胞结构信息。 这些成功使我们有兴趣扩大可以将锰离子传递到细胞的方式。在过去的几年中，我们制作了转铁蛋白 - 曼加尼群。 当绑定到转铁蛋白时，MRI对比剂较差。 但是，当细胞吸收转铁蛋白时，它会释放锰，然后将其细胞内捕获。 因此，转铁蛋白锰是一种通过其受体成功的转铁蛋白内吞作用的药物。 我们已经证明了基于MNOXIDE的纳米颗粒相同的影响。 在pH 7时，mno是不溶性的，并且是非常弱的对比剂。 在低pH值下，在内体/溶酶体中发现，这些颗粒可大大增加MRI弛豫效应。 我们已经完成了研究，这些研究表明，这些颗粒上的二氧化硅涂层在体外和体内延迟了四个小时的溶解。 注射到大脑的颗粒的对比发育速率较慢，而神经元跟踪则进行了MNCL2注射。这打开了制造涂层的可能性，可以在酶上降解，从而使这些酶在体内特异性测定中。 我们已经使用块共聚物合成来证明了Makin Mn纳米颗粒的另一种方法。这些药物的第一代具有很高的放松性，可以调节放松性。 最后，我们开始探索将锰增强MRI的优势转化为人类使用的方法，它利用锰后铁发射同位素，这些同位素将使PET能够获得可以通过锰增强的MRI获得的类似信息。 目标4：制定使细胞过程改变MRI对比剂的松弛性的策略。 在特定目标3中，我们证明了一种正常的生物学过程（转铁蛋白-MN或MNO颗粒的内吞作用）可以改变MRI对比剂的有效性。 找到可能发生对其他生物学过程敏感的方法将非常令人兴奋。 为此，我们已经开始探索可以调节AIM 2下生产的微生物颗粒的方式。 在过去的一年中，我们已经确认可以将微生物颗粒制成pH传感器。使用的策略可以概括地感知许多其他过程。 Block共同聚合物代理提供了使环境敏感的MRI代理的许多可能性，这些可能会在明年进行探索。