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Variation in wall shear stress in channel networks of zebrafish models
Choi, Woorak,Kim, Hye Mi,Park, Sungho,Yeom, Eunseop,Doh, Junsang,Lee, Sang Joon Royal Society 2017 Journal of the Royal Society, Interface Vol.14 No.127
<P>Physiological functions of vascular endothelial cells (ECs) vary depending on wall shear stress (WSS) magnitude, and the functional change affects the pathologies of various cardiovascular systems. Several in vitro and in vivo models have been used to investigate the functions of ECs under different WSS conditions. However, these models have technical limitations in precisely mimicking the physiological environments of ECs and monitoring temporal variations of ECs in detail. Although zebrafish (Danio rerio) has several strategies to overcome these technical limitations, zebrafish cannot be used as a perfect animal model because applying various WSS conditions on blood vessels of zebrafish is difficult. This study proposes a new zebrafish model in which various WSS can be applied to the caudal vein. The WSS magnitude is controlled by blocking some parts of blood-vessel networks. The accuracy and reproducibility of the proposed method are validated using an equivalent circuit model of blood vessels in zebrafish. The proposed method is applied to lipopolysaccharide (LPS)-stimulated zebrafish as a typical application. The proposed zebrafish model can be used as an in vivo animal model to investigate the relationship between WSS and EC physiology or WSS-induced cardiovascular diseases.</P>
Flow characteristics around a deformable stenosis under pulsatile flow condition
Choi, Woorak,Park, Jun Hong,Byeon, Hyeokjun,Lee, Sang Joon American Institute of Physics 2018 Physics of fluids Vol.30 No.1
<P>A specific portion of a vulnerable stenosis is deformed periodically under a pulsatile blood flow condition. Detailed analysis of such deformable stenosis is important because stenotic deformation can increase the likelihood of rupture, which may lead to sudden cardiac death or stroke. Various diagnostic indices have been developed for a nondeformable stenosis by using flow characteristics and resultant pressure drop across the stenosis. However, the effects of the stenotic deformation on the flow characteristics remain poorly understood. In this study, the flows around a deformable stenosis model and two different rigid stenosis models were investigated under a pulsatile flow condition. Particle image velocimetry was employed to measure flow structures around the three stenosis models. The deformable stenosis model was deformed to achieve high geometrical slope and height when the flow rate was increased. The deformation of the stenotic shape enhanced jet deflection toward the opposite vessel wall of the stenosis. The jet deflection in the deformable model increased the rate of jet velocity and turbulent kinetic energy (TKE) production as compared with those in the rigid models. The effect of stenotic deformation on the pulsating waveform related with the pressure drop was analyzed using the TKE production rate. The deformable stenosis model exhibited a phase delay of the peak point in the waveform. These results revealed the potential use of pressure drop waveform as a diagnostic index for deformable stenosis. Published by AIP Publishing.</P>