Haemodynamic dependence of mechano-genetic evolution of the cardiovascular system in Japanese medaka.

Abstract

The progression of cardiac gene expression-wall shear stress (WSS) interplay is critical to identifying developmental defects during cardiovascular morphogenesis. However, mechano-genetics from the embryonic to larval stages are poorly understood in vertebrates. We quantified peak WSS in the heart and tail vessels of Japanese medaka from 3 days post fertilization (dpf) to 14 dpf using <i>in vivo</i> micro-particle image velocimetry flow measurements, and in parallel analysed the expression of five cardiac genes (<i>fgf8</i>, <i>hoxb6b</i>, <i>bmp4</i>, <i>nkx2.5</i>, <i>smyd1</i>). Here, we report that WSS in the atrioventricular canal (AVC), ventricular outflow tract (OFT), and the caudal vessels in medaka peak with inflection points at 6 dpf and 10-11 dpf instead of a monotonic trend. Retrograde flows are captured at the AVC and OFT of the medaka heart for the first time. In addition, all genes were upregulated at 3 dpf and 7 dpf, indicating a possible correlation between the two, with the cardiac gene upregulation preceding WSS increase in order to facilitate cardiac wall remodelling.