Molecular UBM and MRI of Vascular Development

描述（由申请人提供）：在过去的十年中，使用基因工程小鼠的研究已经导致对胚胎血管发育的遗传控制的新见解，这也对我们理解许多人类疾病（包括癌症，动脉粥样硬化和糖尿病）中的新血管形成产生了重大影响。显微成像方法，如超声生物显微镜（UBM）和磁共振显微成像（micro-MRI）可以在这项研究中发挥重要作用，使发育中的小鼠胚胎在子宫内直接可视化。迄今为止，在超声和MRI分子成像领域，特别是在血管发育领域，进展相对较小。UBM是一种真实的时间成像方法，能够对小鼠胚胎心血管解剖结构和血流动力学进行无创体内分析，并且还可以应用于图像引导的血管内注射造影剂。Micro-MRI在操纵细胞/组织对比度方面提供了比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，并且最近才被证明可用于小鼠胚胎的子宫内成像。最近有几份报告表明，可以实现细胞表面的生物素化，允许用抗生物素蛋白缀合的造影剂进行细胞靶向成像，现在可用于超声和MRI。这是一个有吸引力的选择成像血管内皮细胞（VEC），因为造影剂可以通过血管内注射，甚至在胚胎发育阶段的目标细胞。此外，抗生物素蛋白和生物素之间的结合是自然界中发现的最强的，这应该使得即使面对与动脉血流相关的高壁剪切率也可以标记血管细胞。本项目的具体目标是：1）优化子宫内心血管发育分析所需的micro-MRI方案; 2）生产转基因小鼠，设计用于UBM和micro-MRI对VEC进行靶向成像; 3）建立VEC靶向micro-MRI方法，以改善胚胎血管系统的分析。该项目开发的方法将为直接分析活小鼠胚胎中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。

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.