Dynamic Imaging of Mouse Embryos and Cardiac Development in Static Culture

Dynamic imaging is a powerful approach to assess the function of a developing organ system. The heart is a dynamic organ that undergoes quick morphological and mechanical changes through early embryonic development. Defining the embyonic mouse heart's normal function is important for our own understanding of human heart development and will inform us on treatments and prevention of congenital heart defects (CHD). Traditional methods such as ultrasound or fluorescence-based microscopy are suitable for live dynamic imaging, are excellent to visualize structure and connect gene expression to phenotypes, but can be of low quality in resolving fine features and lack imaging depth and scale to fully appreciate organ morphogenesis. Additionally, previous methods can be limited in accommodating a live imaging apparatus capable of sustaining whole embryo development for extended periods time. Optical coherence tomography (OCT) is unique in this circumstance because acquisition of three-dimensional images without contrast reagents, at single cell resolution make it a suitable modality to visualize fine structures in the developing embryo. OCT setups are highly customizable for live imaging because of the tethered imaging arm, due to its setup as a fiber-based interferometer. OCT allows for 4D (3D + time) functional imaging of living mouse embryos and can provide functional and mechanical information to ascertain how the heart's pump function changes through development. In this chapter, we will focus on how we use OCT to visualize live heart dynamics at different stages of development and provide mechanical information to reveal functional properties of the developing heart.