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A Microfluidic System for Studying the Effects of Disturbed Flow on Endothelial Cells - PubMed

  • ️Tue Jan 01 2019

A Microfluidic System for Studying the Effects of Disturbed Flow on Endothelial Cells

Francisco Tovar-Lopez et al. Front Bioeng Biotechnol. 2019.

Abstract

Arterial endothelium experience physical stress associated with blood flow and play a central role in maintaining vascular integrity and homeostasis in response to hemodynamic forces. Blood flow within vessels is generally laminar and streamlined. However, abrupt changes in the vessel geometry due to branching, sharp turns or stenosis can disturb the laminar blood flow, causing secondary flows in the form of vortices. Such disturbed flow patterns activate pro-inflammatory phenotypes in endothelial cells, damaging the endothelial layer and can lead to atherosclerosis and thrombosis. Here, we report a microfluidic system with integrated ridge-shaped obstacles for generating controllable disturbed flow patterns. This system is used to study the effect of disturbed flow on the cytoskeleton remodeling and nuclear shape and size of cultured human aortic endothelial cells. Our results demonstrate that the generated disturbed flow changes the orientation angle of actin stress fibers and reduces the nuclear size while increases the nuclear circularity.

Keywords: actin stress fiber; disturbed flow; endothelial cells (EC); microfluidics; shear stress.

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Figures

Figure 1
Figure 1

A microfluidic system with ridge-shaped obstacles for culturing HAECs under disturbed flow. (ai−ii) The process of fabricating the main block involving a microfluidic channel with a rectangular cross-section of 5 mm × 600 μm forming the side and top walls of the system, (bi−ii) The process of fabricating the PDMS substrate with ridge-shaped obstacles patterned on its surface forming the bottom surface of the system, (c) The process of assembling the main block and the PDMS substrate with ridge obstacles, with the inset showing the zoomed-in PDMS substrate, (di−iv) Flow streamlines at various flow rates of the cell culture medium applied through the microfluidic system, showing the formation and expansion of two vortices at the cavity region located between the neighboring ridges, (e) Variation of flow shear stress along the cavity region, (f) Variation of shear stress magnitude against the flow rate of the cell culture medium for the channel with ridges (disturbed flow) and the control channel without ridges (laminar flow).

Figure 2
Figure 2

Effect of disturbed flow on cytoskeleton remodeling, nucleus circularity and nucleus size of HAECs. (Ai−iii) A confluent layer of HAECs cultured under laminar flow, disturbed flow and static condition, following which the actin cytoskeleton was labeled with Atto 565-phalloidin after fixation. (Bi−iii) The contour of the orientation angle of stress fibers, and (Ci−iii) Histogram of the frequency of the orientation angle of stress fibers, (D) Summary graph of the frequency of the orientation angle of stress fibers cultured under laminar flow, disturbed flow and static condition. The graph is obtained from five independent experiments. ***Indicates P < 0.001, (E) Circularity, and (F) area of the nucleus of HAECs. Data are representative of five independent experiments, and error bars shown in (D-F) represent 95% confidence interval. 70 nuclei have been analyzed for each group. **Indicates P < 0.01 and ***P < 0.001.

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