Embryonic Mouse Cardiodynamic OCT Imaging

Abstract

The embryonic heart is an active and developing organ. Genetic studies in mouse models have generated great insight into normal heart development and congenital heart defects, and suggest mechanical forces such as heart contraction and blood flow to be implicated in cardiogenesis and disease. To explore this relationship and investigate the interplay between biomechanical forces and cardiac development, live dynamic cardiac imaging is essential. Cardiodynamic imaging with optical coherence tomography (OCT) is proving to be a unique approach to functional analysis of the embryonic mouse heart. Its compatibility with live culture systems, reagent-free contrast, cellular level resolution, and millimeter scale imaging depth make it capable of imaging the heart volumetrically and providing spatially resolved information on heart wall dynamics and blood flow. Here, we review the progress made in mouse embryonic cardiodynamic imaging with OCT, highlighting leaps in technology to overcome limitations in resolution and acquisition speed. We describe state-of-the-art functional OCT methods such as Doppler OCT and OCT angiography for blood flow imaging and quantification in the beating heart. As OCT is a continuously developing technology, we provide insight into the future developments of this area, toward the investigation of normal cardiogenesis and congenital heart defects.

In Vivo Imaging of Mammalian Embryos by NIR-I Photoacoustic Tomography and NIR-II Optical Coherence Tomography Using Gold Nanostars as Multifunctional Contrast Agents

“…The edges and details of different structures (e.g., the heart, green arrow) [Figure 6e] were also clearer in OCT images with GNS injection. 52 At greater depths (e.g., 825.552 μm), the OCT images of the control case had lost certain information around the center of the embryo, whereas the OCT images of both IV and IVG GNS injections still conserved distinct structural details. Furthermore, we quantified the mean signal amplitudes within the red-dashed line regions of different depths, and the result is displayed [Figure 6g].…”

Mouse embryo phenotyping with optical coherence tomography

“…By E7.5 in mice, aggregates of cells called blood islands emerge in the developing yolk sac, which give rise to endothelial cell precursors and primitive erythroblasts (Shalaby et al, 1997;Larin et al, 2009;Garcia and Larina, 2014). A distinct feature of cardiac embryonic development is that the heart begins to contract before the advent of blood circulation, pointing towards a role for hemodynamic forces in cardiovascular development (Lopez et al, 2020a). In mice, the primitive heart tube begins to contract at E8.0, but primarily pumps plasma throughout the vascular network and embryo (Larin et al, 2009).…”

“…With a spatial resolution of 2-10 µm and millimeter-level imaging depth (1-3 mm), the imaging capabilities of OCT are positioned between confocal microscopy and high-frequency ultrasound. Due to these specifications, OCT is uniquely suitable for mouse embryonic imaging and is capable of assessing structural dynamics in embryonic organs including the developing heart, which is only a few hundred microns in size during the early developmental stages (reviewed by (Lopez et al, 2020a)). To capture the dynamics of the embryonic hearts in 4D (3D + time), multiple approaches for direct volumetric as well as sequential data acquisition, retrospective gating, and post-acquisition synchronization have been developed (Larina et al, 2012b;Bhat et al, 2013;Wang et al, 2015b;Wang et al, 2016), which provide enhanced sampling rate and accuracy of the heartbeat reconstruction toward a time-resolved mechanistic investigation of cardiogenesis.…”

Lightsheet Microscopy

“…Other forms of tomographic imaging (Fig. 1 in Follain et al, 2017;Norris et al, 2013;Singh et al, 2016;Tsien, 2003;Wang, Larina, & Larin, 2020), which include MRI (Mandino et al, 2020;Zhang, Wu, & Turnbull, 2018), micro-CT (Cole et al, 2018;Holdsworth & Thornton, 2002;Rawson et al, 2020), OCT (Burwood, Fridberger, Wang, & Nuttall, 2019;Drexler et al, 2014;Lopez, Wang, & Larina, 2020;Wu et al, 2017), OPT (Bassi, Schmid, & Huisken, 2015;Gualda, Moreno, Tomancak, & Martins, 2014;Sharpe, 2004;Watson et al, 2017;Wong, Dazai, Walls, Gale, & Henkelman, 2013), and SLOT (Tinne et al, 2017), were developed to image macroscopic specimens, but a large volume capability comes at the expense of limited resolving power and limited depth of tissue penetration. Huisken and Stainier (2009) and Hutson et al (2021) provide comparative reviews of these tomographic methods with lightsheet microscopy, but Hutson et al conclude that confocal microscopy is still dominant for studying cochlea (e.g., MacDonald & Rubel, 2008).…”