A multiple-channel, multiple-assay platform for characterization of full-range shear stress effects on vascular endothelial cells

Abstract

Vascular endothelial cells (VECs), which line blood vessels and are key to understanding pathologies and treatments of various diseases, experience highly variable wall shear stress (WSS) in vivo (1-60 dyn cm(-2)), imposing numerous effects on physiological and morphological functions. Previous flow-based systems for studying these effects have been limited in range, and comprehensive information on VEC functions at the full spectrum of WSS has not been available yet. To allow rapid characterization of WSS effects, we developed the first multiple channel microfluidic platform that enables a wide range (~15×) of homogeneous WSS conditions while simultaneously allowing trans-monolayer assays, such as permeability and trans-endothelial electrical resistance (TEER) assays, as well as cell morphometry and protein expression assays. Flow velocity/WSS distributions between channels were predicted with COMSOL simulations and verified by measurement using an integrated microflow sensor array. Biomechanical responses of the brain microvascular endothelial cell line bEnd.3 to the full natural spectrum of WSS were investigated with the platform. Under increasing WSS conditions ranging from 0 to 86 dyn cm(-2), (1) permeabilities of FITC-conjugated dextran and propidium iodide decreased, respectively, at rates of 4.06 × 10(-8) and 6.04 × 10(-8) cm s(-1) per dyn cm(-2); (2) TEER increased at a rate of 0.8 Ω cm(2) per dyn cm(-2); (3) increased alignment of cells along the flow direction under increasing WSS conditions; and finally (4) increased protein expression of both the tight junction component ZO-1 (~5×) and the efflux transporter P-gp (~6×) was observed at 86 dyn cm(-2) compared to static controls via western blot. We conclude that the presented microfluidic platform is a valid approach for comprehensively assaying cell responses to fluidic WSS.

A versatile lab-on-a-chip tool for modeling biological barriers

“…There are several setups built for similar purposes. Most of them consist of two channels, either parallel [30] or perpendicular to each other [19,31], with a relatively small overlapping area. The arrangement of our channels enables a much larger overlapping area (ca.…”

“…Such a feature is missing in other model systems using nontransparent electrodes that allow visual observation limited to the narrow slits between the electrodes [16,19], therefore a full microscopic screening of the sample can only be done on the disassembled chip. This is a critical point for such assays that include monitoring of TEER or paracellular permeability of the barrier membrane, since local faults in the confluence of the cell layer, occurring usually at its perimeter and invisible for other methods, might seriously tamper the results.…”

“…In contrast to the static culture inserts, the cells can be exposed to fluid flow and shear stress, which are especially important for the vascular endothelium [18][19][20]. Although a dynamic BBB model on a 3-dimensional tube structure with a continuous flow of culture medium has been published, the real-time visualization of the cells is not possible with the hollow fiber system [18,21].…”

Reproducibility in biological models of the blood-brain barrier

“…These devices are based on a similar concept as Transwell ™ systems, i.e. they consist of an apical and a basolateral compartments, which are separated by a porous membrane (62, 63,65) or small gaps (64). Most of these systems are based on a so-called sandwich concept; however, Prabhakarpandian et al (64) have recently presented a different design, synthetic microvasculature model of the BBB (SyM-BBB), in which the position of apical compartment is side-by side with the basolateral compartment, enabling real-time optical monitoring.…”

3D Anastomosed Microvascular Network Model with Living Capillary Networks and Endothelial Cell-Lined Microfluidic Channels

“…One strategy is to create microfabricated vessel scaffolds with specific geometries and dimensions, and line their inner surface with endothelial cells (ECs). The advantage of this method is that the vessel diameter can be precisely controlled, and the tightness of EC junctions can be flexibly adjusted by imposing different shear stress parameters on these lined ECs [4][5][6]. The other strategy is to seed cells in 3D extracellular matrices (ECMs) to allow spontaneous formation and remodeling of vascular networks through vasculogenesis and angiogenesis, which can closely mimic vascular development in vivo [7][8][9][10][11][12].…”