In Vivo Wall Shear Measurements within the Developing Zebrafish Heart

Abstract

Physical forces can influence the embryonic development of many tissues. Within the cardiovascular system shear forces resulting from blood flow are known to be one of the regulatory signals that shape the developing heart. A key challenge in investigating the role of shear forces in cardiac development is the ability to obtain shear force measurements in vivo. Utilising the zebrafish model system we have developed a methodology that allows the shear force within the developing embryonic heart to be determined. Accurate wall shear measurement requires two essential pieces of information; high-resolution velocity measurements near the heart wall and the location and orientation of the heart wall itself. We have applied high-speed brightfield imaging to capture time-lapse series of blood flow within the beating heart between 3 and 6 days post-fertilization. Cardiac-phase filtering is applied to these time-lapse images to remove the heart wall and other slow moving structures leaving only the red blood cell movement. Using particle image velocimetry to calculate the velocity of red blood cells in different regions within the heart, and using the signal-to-noise ratio of the cardiac-phase filtered images to determine the boundary of blood flow, and therefore the position of the heart wall, we have been able to generate the necessary information to measure wall shear in vivo. We describe the methodology required to measure shear in vivo and the application of this technique to the developing zebrafish heart. We identify a reduction in shear at the ventricular-bulbar valve between 3 and 6 days post-fertilization and demonstrate that the shear environment of the ventricle during systole is constantly developing towards a more uniform level.

Contractile and hemodynamic forces coordinate Notch1b-mediated outflow tract valve formation

“…Although the use of 2D moving-domain CFD modeling linked 3D hemodynamic forces (time and 2D plane) with mechanotransduction underlying AV valve morphogenesis, further increases in our computing capacity would enhance the use of 4D CFD (time and 3D space) to evaluate the hemodynamic microenvironment in the developing OFT. Nonetheless, the OFT WSS values obtained in our moving-domain CFD model system are consistent with previous studies (9).…”

“…These valves are structurally similar to mammalian valves, and the developmental cellular events of valvulogenesis are largely conserved among species (1). Previous studies have focused on the role of fluid shear stress in valve development; however, there remains a paucity of data elucidating the relative importance of contractile and hemodynamic shear forces in the outflow tract (OFT) of the developing zebrafish embryo (5,9), and the downstream signaling pathways and effects on VB valve development remain largely unknown.…”

A Hybrid of Light-Field and Light-Sheet Imaging to Decouple Myocardial Biomechanics from Intracardiac Flow Dynamics

“…Unlike the conventional Particle Image Velocimetry (PIV) (Hove, 2006;Hove et al, 2003;Jamison et al, 2013), PTV has been demonstrated to capture the intracardiac blood flow (Yalcin et al, 2017), allowing for mapping the trajectories of individual dsRed-labeled blood cells from AVC to outflow track (OFT). While PIV provides high spatial resolution and detailed velocity profiles, PTV enables time-dependent tracking of each individual signal in a dynamic space.…”

Valveless pumping mechanics of the embryonic heart during cardiac looping: Pressure and flow through micro-PIV

“…Embryos are imaged ventral-side up in a low gelling temperature agarose (Sigma Aldrich, Type VII-A, A0701), as previously described with an attempt to image along a crosssection aligned with the orientation of the heart (Johnson et al, 2015). The setup is illustrated in the each point in the cardiac cycle, a technique different from the sliding average previously used (Jamison et al, 2013;Johnson et al, 2013a). Therefore, the heart wall is removed, but slow moving red blood cells (RBCs) are not filtered from the images when performing flow calculations.…”