Optical Coherence Tomography as a Tool for Measuring Morphogenetic Deformation of the Looping Heart

Abstract

Optical coherence tomography (OCT) was used to investigate morphogenesis of the embryonic chick heart during the first phase of looping (c-looping), as the heart bends and twists into a c-shaped tube. The present study focuses on the morphomechanical effects of the splanchnopleure (SPL), a membrane that has been shown to play a major role in cardiac torsion by pressing against the ventral surface of the heart. Without the SPL, rightward torsion (rotation) is delayed. The images show that compressive forces exerted by the SPL alter the shapes of the heart tube and primitive atria, as well as their spatial relationships. The SPL normally holds the heart in the plane of the embryo and forces cardiac jelly (CJ) out of adjacent regions in the atria. When the SPL is removed, cross-sections become more circular, CJ is more uniformly distributed, and the heart displaces ventrally. In addition, OCT-based morphogenetic strain maps were measured during looping by tracking the three-dimensional motions of microspheres placed on the myocardium. The spatial-temporal patterns of the strains correlated well with the observed behavior of the heart, including delayed torsion that occurs in SPL-lacking embryos. These results illustrate the potential of OCT as a tool in studies of morphogenesis, as well as provide a better understanding of the mechanical forces that drive cardiac looping.

Mechanics of head fold formation: investigating tissue-level forces during early development

“…Cross-sectional image stacks were reconstructed into 3D volumes and optically sectioned using Volocity (Improvision, Waltham, MA, USA). Time-lapse experiments were conducted with the custom-built OCT system described previously (Filas et al, 2007;Filas et al, 2008).…”

“…As described by Filas et al (Filas et al, 2007), the MATLAB routine gridfit was used to fit 2D surfaces through the set of marker coordinates to generate x(X, Y) and y(X, Y), which give the strain components in image coordinates by equation (1). Standard equations (Taber, 2004) were then used to transform these strains into components relative to an embryo coordinate system (X, Y) (Fig.…”

Bimodal biophotonic imaging of the structure-function relationship in cardiac tissue

“…8 To date, the clinical applications for OCT in cardiology relate to coronary artery imaging. However in cardiac research, OCT has also been used to study the mechanical function of the embryonic mouse heart, 9 and the growth mechanics of the developing chick heart, 10 demonstrating that OCT can be used to investigate the relationship between cardiac structure and mechanical function. Also, two previous preliminary studies have shown that OCT can be used to recognize components of the cardiac conduction system, 4,11 which demonstrates that OCT can visualize distinct anatomical structures within the myocardium.…”

Comparison and combination of rotational imaging optical coherence tomography and selective plane illumination microscopy for embryonic study

“…In addition, the contrast in OCT images comes from the optical scattering properties of tissue, and thus OCT can capture valuable structural features by depicting tissue boundaries. For example, OCT has been frequently utilized to study embryonic heart morphogenesis during cardiac looping process to understand the etiology of congenital heart defects [19,20]. Recently OCT was used to image the neural tube closure which is a critical process in the development of neural tube defects [21].…”