AbstractsBiology & Animal Science

The identity of cells generating the first blood cells in the mammalian embryo was unknown until recently. The formation of blood from embryonic endothelium was recently observed by live cell imaging. It was hypothesized that pulsatile shear stress was responsible for induction of blood production in the developing embryo. The aims of this thesis were to develop a microfluidic chip to mimic the embryonic heart and circulation and examine the response of endothelial cell to pulsatile shear flow. The chip was manufactured in PDMS consisting of a peristaltic pump with pneumatic actuated microvalves and ‘ventricle’ connected to parallel-plate flow-cells with recirculation. In addition, cell loading, media and reagent replacement was also controlled by three parallel micro-pneumatic valves. The timing of the cardiac cycle was controlled by a microprocessor which actuated solenoid valves driving microvalve closure and ventricular contractions. The pulse rate could be varied between 50-200 cycles/min. The temporal flow profile in circulatory system was characterised by micro particle image velocimetry (Micro-PIV), and could be adjusted by varying valve duty cycle and ventricle ejection fraction. The waveform was adjusted to mimic the embryonic aortic temporal flow profile with a maximal shear stress of 35 dyne/cm2. Bovine artery endothelial cells (BAEC) were cultured and tracked by phase contrast video microscopy over a 7-day period. The microfluidic platform can mimic the micromechanical environment of endothelial cells. Furthermore, these studies provide an in vitro model system for vascular biology research, leading to a deeper understanding of vascular endothelial mechanism.