Cardiac-like flow generator for long-term imaging of endothelial cell responses to circulatory pulsatile flow at microscale

Abstract

In vitro models of circulatory hemodynamics are required to mimic the microcirculation for study of endothelial cell responses to pulsatile shear stress by live cell imaging. This study reports the design, fabrication and characterisation of a microfluidic device that generates cardiac-like flow in a continuous culture system with a circulatory volume of only 2-3 μL. The device mimics a single chamber heart, with the following cardiac phases: (1) closure of the ventricle inlet valve, (2) contraction of the ventricle (systole) followed by opening of the outlet valve and (3) relaxation of the ventricle (diastole) with opening of the inlet valve whilst the outlet valve remains closed. Periodic valve states and ventricular contractions were actuated by microprocessor controlled pneumatics. The time-dependent velocity-field was characterised by micro-particle image velocimetry (μ-PIV). μ-PIV observations were used to help tune electronic timing of valve states and ventricular contractions for synthesis of an arterial pulse waveform to study the effect of pulsatile shear stress on bovine artery endothelial cells (BAECs). BAECs elongated and aligned with the direction of shear stress after 48 h of exposure to a pulsatile waveform with a maximum shear stress of 0.42 Pa. The threshold for BAECs alignment and elongation under steady (non-pulsatile) flow reported by Kadohama et al. (2006) is 0.7-1.4 Pa. These cells respond to transient shear stress because the time average shear stress of the pulse waveform to generate this morphological response was only 0.09 Pa, well below the steady flow threshold. The microfluidic pulse generator can simulate circulatory hemodynamics for live cell imaging of shear-induced signalling pathways.

Organoids, organs-on-chips and other systems, and microbiota

“…In addition, this system can be exploited to complement animal studies and also more accurately predict pharmacological effects in patients and, in the future, could be used to bypass the use of animal testing completely [110]. Organ-on-a-chip has been developed for several organs, including the lung [111,112], heart [113,114], liver [115], neuron [116], kidney [117,118], gut [14,43,119], blood vessel [120,121], tumour-on-a-chip [122], bone marrow-on-a-chip [123], liver-tumour-bone marrow-on-a-chip [124], and liver-skin-intestine-kidney-on-a-chip [125]. These systems can be extended to disease modelling, pharmaceutical analysis, drug development strategies [6, 118,122], and understanding host-microbe interactions [14,111,122].…”

A microfluidic device towards shear stress analysis of clonal expanded endothelial cells

“…There have been several recent publications exhibiting alignment of ECs in microfluidic channels (van der Meer, et al, 2010;Song, et al, 2005;Chen, et al, 2013;Sasaki, et al, 2012 andRossi, et al, 2009). Furthermore, some researchers have attempted to simulate the pulsatile and oscillatory shear stress that ECs experience in vivo (Chen, et al, 2013 andShao, et al, 2009).…”

“…Furthermore, some researchers have attempted to simulate the pulsatile and oscillatory shear stress that ECs experience in vivo (Chen, et al, 2013 andShao, et al, 2009). However, to date, only a few examples of microfluidic devices that allow screening of several shear stress conditions simultaneously have been published (Song, et al, 2005;Rossi, et al, 2009;Lu, et al, 2004 andConant, et al, 2011), and none of those designs have multiple isolated culture chambers for each condition, and can therefore not be used for clonal heterogeneity analysis.…”

“…Microfluidic-based devices also require smaller volumes of reagents, which could reduce the cost of the assay and save precious samples. For example, a microfluidic device proposed by Chen et al only consumes a volume of 2-3 µl (Chen, et al, 2013), whereas a typical macro system would consume tens of milliliters. Microfluidic systems also decrease the risk of contaminants because they provide a closed environment, in contrast to open macro systems.…”

Biomimetic Cardiac Microsystems for Pathophysiological Studies and Drug Screens

“…28,30,32 To increase throughput and controllability of CMS platforms, parallel microfluidic pumps and valves have been introduced. 25,29 Such platforms have eventually heightened interest in the integration of pulsatile flow and structure of the cardiac system within the microfluidic cell culture. Further development of these in vitro CMS platforms has significant roles to find the mechanism of various cardiac diseases with tunable static and dynamic culture environments and improve drug development by generating an engineered disease model.…”