Molecular UBM and MRI of Vascular Development

描述(申请人提供)：在过去的十年里，使用基因工程小鼠的研究使人们对胚胎血管发育的基因控制有了新的见解，这也对我们理解许多人类疾病中的新生血管产生了重大影响，包括癌症、动脉粥样硬化和糖尿病。超声生物显微镜(UBM)和磁共振显微成像(Micro-MRI)等微成像方法可以在这项研究中发挥重要作用，使发育中的小鼠胚胎能够在宫内直接可视化。到目前为止，超声和核磁共振在分子成像领域的进展相对较少，特别是在血管发育领域。UBM是一种实时成像方法，可以对小鼠胚胎心血管解剖和血流动力学进行无创的活体分析，也可以用于图像引导的血管内注射造影剂。在操纵细胞/组织对比度方面，Micro-MRI提供了比UBM更好的3D分辨率和更大的灵活性，包括更多可用的造影剂和细胞靶向成像方法，但需要更长的采集时间，并且直到最近才被证明在小鼠胚胎的宫内成像是有效的。最近的几份报告表明，可以实现细胞表面的生物素化，允许使用亲和素标记的造影剂进行细胞靶向成像，这种造影剂现在可以用于超声和核磁共振。这对于血管内皮细胞(VECs)成像是一个有吸引力的选择，因为造影剂可以通过血管内注射传递到感兴趣的细胞，即使在胚胎发育阶段也是如此。此外，亲和素和生物素之间的结合是自然界中发现的最强的结合，这应该使它能够标记血管细胞，即使面对与动脉血流相关的高壁切率。该项目的具体目标是：1)优化心血管发育的宫内分析所需的Micro-MRI方案；2)生产用于利用UBM和Micro-MRI对血管内皮细胞进行靶向成像的转基因小鼠；以及3)建立针对VEC的Micro-MRI方法，以改进胚胎血管系统的分析。该项目开发的方法将为直接分析活鼠胚胎的血管发育提供强大的新工具。值得注意的是，这些新的分子成像方法将首次提供检测正常和基因工程小鼠子宫内血管基因表达的能力。 公共卫生相关性：该项目旨在将超声和核磁共振血管显微成像方法从解剖学和功能的测量方法转移到多种心血管疾病的基因工程小鼠模型中的体内分子成像水平。这些新的分子成像方法将使小鼠遗传学发生革命性变化，使新的研究能够将人类发育和疾病的最佳哺乳动物模型中的基因表达与血管形态和生理功能联系起来。

DESCRIPTION (provided by applicant): Over the past decade, investigations using genetically-engineered mice have led to new insights into the genetic control of embryonic vascular development, which has also had a major impact on our understanding of neovascularization in many human diseases including cancer, atherosclerosis and diabetes. Micro-imaging methods such as ultrasound biomicroscopy (UBM) and magnetic resonance micro-imaging (micro-MRI) can play an important role in this research, enabling direct in utero visualization of the developing mouse embryo. To date, there has been relatively little progress in the area of molecular imaging with ultrasound and MRI, especially in the area of vascular development. UBM is a real time imaging method enabling noninvasive in vivo analysis of mouse embryonic cardiovascular anatomy and hemodynamics, and can also be applied for image-guided intravascular injection of contrast agents. Micro-MRI provides better 3D resolution and more flexibility than UBM in manipulating cellular/tissue contrast, including more available contrast agents and approaches for cell-targeted imaging, but requires longer acquisition times, and has only recently been demonstrated for effective in utero imaging of mouse embryos. Several reports have recently demonstrated that biotinylation of cell surfaces can be achieved, allowing cell-targeted imaging with avidin-conjugated contrast agents, which are now available for both ultrasound and MRI. This is an attractive option for imaging vascular endothelial cells (VECs), since contrast agents can be delivered to the cells of interest via intravascular injection, even at embryonic stages of development. Moreover, the binding between avidin and biotin is the strongest found in nature, which should make it possible to label vascular cells even in the face of high wall shear rates associated with arterial blood flow. The specific aims of this project are: 1) To optimize the micro-MRI protocols required for in utero analysis of cardiovascular development; 2) To produce transgenic mice designed for targeted imaging of VECs with UBM and micro-MRI; and 3) To establish VEC-targeted micro-MRI approaches for improved analyses of embryonic vasculature. The approaches developed in this project will provide powerful new tools for direct analysis of vascular development in living mouse embryos. Significantly, these new molecular imaging methods will provide, for the first time, the ability to detect vascular gene expression in utero in normal and genetically-engineered mice. PUBLIC HEALTH RELEVANCE: This project aims to move ultrasound and MRI vascular micro-imaging methods beyond measures of anatomy and function, to the level of in vivo molecular imaging in genetically-engineered mouse models of a wide range of cardiovascular disease. These new molecular imaging approaches will revolutionize mouse genetics, enabling new studies linking gene expression to vascular morphology and physiological function in the best characterized mammalian model of human development and disease.