MRI Contrast Agents for In vivo Monitoring of Stem Cell Differentiation

用于干细胞分化体内监测的 MRI 造影剂

• 批准号: 8768980
• 负责人: Erik Shapiro
• 金额: $ 23.7万
• 依托单位: MICHIGAN STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8768980
• 关键词: Activities of Daily Living; Animals; Biochemical Reaction; Biocompatible; Biological Assay; Biopolymers; Cell Differentiation process; Cell Therapy; Cell Transplantation; Cells; Chemicals; Cleaved cell; Computer Simulation; Contrast Media; Detection; Dextrans; Encapsulated; Endosomes; Engineering; Environment; Enzymes; Excision; Future; Gene Expression; Gene Expression Profiling; Goals; Gold; Hour; Imagery; Imaging technology; In Vitro; Ions; Label; Life; Location; Lysosomes; Magnetic Resonance Imaging; Magnetism; Manganese; Mediating; Methodology; Methods; Modeling; Modification; Monitor; New Agents; Non-Invasive Cancer Detection; Nucleosome Core Particle; Organism; Play; Property; Publishing; Reporter; Research; Research Personnel; Resistance; Resolution; Role; Signal Transduction; Spottings; Stem cell transplant; Stem cells; Structure; Subcellular structure; System; Testing; Thick; Transgenes; Translating; Transplantation; Vision; Water; Work; base; bench to bedside; cell motility; cell type; clinical application; design; dextran; in vivo; innovation; iron oxide; nanocrystal; nanoparticle; non-invasive imaging; novel; particle; public health relevance; simulation; stem cell differentiation; stem cell therapy; water solubility

DESCRIPTION (provided by applicant): Key to the promise of stem cells for therapy is a method for non-invasively detecting cellular migration and differentiation. MRI-based cell tracking using magnetic particles has been utilized to detect cell migration in vivo, however, it i currently incapable of detecting cell differentiation. This is because the magnetic particles currently used for cell tracking create the same MRI contrast whether they are inside a stem cell or mature cell. Here we propose to design, synthesize and characterize novel classes of biopolymer encapsulated metallic nanoparticles which will enable the use of MRI to non-invasively detect stem cell differentiation, in vivo. The underlying principal of these new particls is the ability of these particles to achieve large enhancements in molar relaxivity based upon enzyme-triggered modification of the biopolymer coat. Briefly, the MRI properties of magnetic particles vary greatly depending on the coating thickness over the magnetic cores and their aggregated state, even though the amount of magnetic material remains constant. Additionally, MRI contrast agents have vastly different properties based on water solubility. We will synthesize different classes of biopolymer coated metallic core particles whose coating will be able to be enzymatically cleaved and removed. The biopolymer coatings will be biocompatible, yet highly resistant to passive degradation in the cells. Furthermore, for some particles, the metallic core will be able to dissolve. Dynamic manipulations of these phenomena will result in large enhancements of relaxivity and hence, of the MRI signal. Computer simulations predicting relaxivity changes as a function of coating thickness will guide the nanoparticle fabrication. We will then test whether enzyme-mediated removal of the biopolymer coating indeed results in modulation of the MRI properties. Simulations predict a 10-fold increase in r2, a 4-fold increase in r2* for iron oxide based particles, and a 50-fold increase in r1 for manganese based particles. These new classes of particles will form the technological core for non-invasive visualization of stem cell differentiation in intact organisms by MRI and can be further generalized to monitoring gene expression. Upon internalization into cells, nano- and microparticles are sequestered in endosomes and lysosomes. While it has been known that dextran coated magnetic particles slowly degrade within these structures, no study has yet purposely harnessed this phenomenon. The innovation of this proposed work is that we are utilizing the chemical environment within these subcellular structures as a medium for enzymatic reactions that will modulate water accessibility to the metallic cores, and in some cases, to dissolve them. Future implementation of these particles will utilize reporter enzymes to react with particles, engineered as transgenes, which will be expressed during the transition from stem cell to mature cell. So, rather than particles slowly degrading over several weeks, we will force the decomposition of these constructs to occur within hours once triggered, thus providing a relatively rapid, non-invasive, high resolution, three dimensional readout of stem cell differentiation.

描述（由申请人提供）：干细胞进行治疗承诺的关键是一种非侵入性检测细胞迁移和分化的方法。使用磁性颗粒的基于MRI的细胞跟踪已被用来检测体内细胞迁移，但是，我目前无法检测到细胞分化。这是因为当前用于细胞跟踪的磁颗粒无论是在干细胞内还是成熟细胞内都会产生相同的MRI对比度。在这里，我们建议设计，合成和表征新型的生物聚合物封装的金属纳米颗粒，这些金属纳米颗粒将使MRI在体内使用MRI进行非侵入性检测干细胞分化。这些新颗粒的基本原理是这些颗粒基于生物聚合物涂层的酶触发的修饰，在摩尔松弛度中实现大大增强的能力。简而言之，磁性颗粒的MRI特性差异很大，具体取决于磁芯上的涂层厚度及其聚集状态，即使磁性材料的量保持恒定。此外，基于水溶解度，MRI对比剂具有截然不同的特性。我们将综合不同类别的生物聚合物涂层的金属核心颗粒，其涂层将能够酶上切割和去除。生物聚合物涂层将具有生物相容性，但对细胞中的被动降解具有高度耐药性。此外，对于某些粒子，金属芯将能够溶解。对这些现象的动态操作将导致大量增强的松弛性，因此MRI信号的动态操纵。计算机模拟预测松弛性随涂层厚度的函数的变化将指导纳米颗粒制造。然后，我们将测试酶介导的去除生物聚合物涂层是否确实会导致MRI特性的调节。模拟预测R2增加了10倍，基于氧化铁的颗粒的R2*增加了4倍，而基于锰的颗粒的R1增加了50倍。这些新类别的颗粒将构成通过MRI完整生物中干细胞分化的非侵入性可视化的技术核心，并可以进一步推广到监测基因表达。内部化到细胞中后，将纳米和微粒在内体和溶酶体中隔离。尽管众所周知，葡聚糖涂层的磁性颗粒在这些结构内慢慢降解，但尚未有目的地利用这种现象。这项拟议工作的创新是，我们利用这些亚细胞结构中的化学环境作为酶促反应的一种介质，可以调节对金属核的水可及性，在某些情况下可以溶解它们。这些颗粒的未来实施将利用报告酶与粒子反应，以转基因为工程， 这将在从干细胞到成熟细胞的过渡期间表达。因此，我们将迫使这些构建体的分解在几个小时内发生，而不是在触发的几个小时内进行分解，从而提供了相对较快，无创，高分辨率，高分辨率，三维干细胞分化的三维读数。