Molecular UBM and MRI of Vascular Development

描述（由申请人提供）：在过去的十年中，利用基因工程小鼠进行的研究使我们对胚胎血管发育的遗传控制有了新的认识，这也对我们对许多人类疾病（包括癌症、动脉粥样硬化和糖尿病）中新血管形成的理解产生了重大影响。超声生物显微镜（UBM）和磁共振微成像（micro-MRI）等微成像方法可以在该研究中发挥重要作用，可以直接在子宫内观察发育中的小鼠胚胎。迄今为止，在超声和核磁共振分子成像领域，特别是在血管发育领域，进展相对较少。UBM是一种实时成像方法，可以无创地在体内分析小鼠胚胎心血管解剖和血流动力学，也可以应用于图像引导下血管内注射造影剂。Micro-MRI在操纵细胞/组织造影剂方面比UBM提供更好的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有效地用于小鼠胚胎的子宫成像。最近有几篇报道表明，细胞表面的生物素化可以实现，从而允许使用亲和素偶联造影剂进行细胞靶向成像，这种造影剂现在可用于超声和MRI。这是成像血管内皮细胞（VECs）的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，甚至在胚胎发育阶段。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，这应该使标记血管细胞成为可能，即使面对与动脉血流相关的高壁剪切率。该项目的具体目标是：1)优化子宫内心血管发育分析所需的微mri方案；2)制备转基因小鼠，用于UBM和微mri靶向成像VECs；3)建立针对vec的微mri方法，以改进胚胎血管的分析。本项目开发的方法将为直接分析活体小鼠胚胎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在正常和基因工程小鼠子宫内检测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.