Imaging mouse embryonic cardiovascular development

Early development of the mammalian cardiovascular system is a highly dynamic process. Live imaging is an essential tool for analyzing normal and abnormal cardiovascular development and dynamics. This article describes two optical approaches for live dynamic imaging of mouse embryonic cardiovascular development: confocal microscopy and optical coherence tomography (OCT). Confocal microscopy, used in combination with fluorescent protein reporter lines, enables visualization of the developing and remodeling cardiovascular system with submicron resolution and even allows visualization of subcellular details of labeled structures. We describe mouse transgenic lines that can be used to image the developing vasculature and characterize hemodynamics by tracking individual blood cells. Confocal microscopy of vital fluorescent markers reveals unique details about cell morphogenesis and movement; however, the imaging depth of this method is limited to ∼200 µm. This limitation can be addressed by using OCT, which allows three-dimensional (3D) imaging millimeters into tissue, although this is achieved at the expense of lower spatial resolution (2-10 µm). We describe here how OCT can be applied to the structural analysis of developing mouse embryos and hemodynamic analysis in deep embryonic vessels. These complementary approaches can be used to analyze cardiovascular defects in mutant animals to understand genetic signaling pathways regulating human development.