A microfluidic membrane device to mimic critical components of the vascular microenvironment

Abstract

Vascular function, homeostasis, and pathological development are regulated by the endothelial cells that line blood vessels. Endothelial function is influenced by the integrated effects of multiple factors, including hemodynamic conditions, soluble and insoluble biochemical signals, and interactions with other cell types. Here, we present a membrane microfluidic device that recapitulates key components of the vascular microenvironment, including hemodynamic shear stress, circulating cytokines, extracellular matrix proteins, and multiple interacting cells. The utility of the device was demonstrated by measuring monocyte adhesion to and transmigration through a porcine aortic endothelial cell monolayer. Endothelial cells grown in the membrane microchannels and subjected to 20 dynes/ cm 2 shear stress remained viable, attached, and confluent for several days. Consistent with the data from macroscale systems, 25 ng/ml tumor necrosis factor ͑TNF͒-␣ significantly increased RAW264.7 monocyte adhesion. Preconditioning endothelial cells for 24 h under static or 20 dynes/ cm 2 shear stress conditions did not influence TNF-␣-induced monocyte attachment. In contrast, simultaneous application of TNF-␣ and 20 dynes/ cm 2 shear stress caused increased monocyte adhesion compared with endothelial cells treated with TNF-␣ under static conditions. THP-1 monocytic cells migrated across an activated endothelium, with increased diapedesis in response to monocyte chemoattractant protein ͑MCP͒-1 in the lower channel of the device. This microfluidic platform can be used to study complex cell-matrix and cell-cell interactions in environments that mimic those in native and tissue engineered blood vessels, and offers the potential for parallelization and increased throughput over conventional macroscale systems.

A standalone perfusion platform for drug testing and target validation in micro-vessel networks

“…With stimulation, monocyte attachment on the micro-vessel network increased dramatically from the healthy control suggesting the microvessel network can capture the effect of the stimuli, promoting monocyte attachment ( Figure 3(d)). In addition, in both stimulated and non-stimulated micro-vessels, the density of the adherent monocytes (50 cells/mm 2 and 120 cells/mm 2 , respectively) was approximately 40% lower than previously reported on an endothelial cell monolayer under flow condition, 5 which may suggest that the presence of curvature wall and geometrical confinement could affect flow path and cell-cell binding. Therefore the circular micro-channels could be a more realistic and improved model compared to the overly simplified parallel plate bioreactor and rectangular micro-channels.…”

“…Previously developed systems relied on the use of rectangular channels with only one order of branching 9 or membrane microfluidic devices where monolayers of endothelial cells were cultivated. 5 Although more complex devices were envisioned in a mathematical modeling study focusing on designing networks that minimize vascular volume fraction, no designs were experimentally implemented and seeded with cells. 10 Although biologists may not be willing to fabricate the platform on their own, the platform contains all the components required for its operation.…”

“…Current microfluidic approaches either culture endothelial cells simply on the bottom of a micro-channel [5][6][7] or coat endothelial cells around a rectangular channel with sharp corners. [6][7][8][9][10] These approaches can establish a vasculature quickly in defined conditions but ignore the artifacts generated by the sharp corners on the endothelialized lumen.…”

A microfluidic-based device for study of transendothelial invasion of tumor aggregates in realtime

“…These models have been used to study the interactions between the endothelium and other cells, such as leukocytes or cancer cells. [30][31][32][33][34][35][36] However, most current microfluidic blood vessel models only provide a controlled environment for adhesion of individual cancer cells to the endothelium under stimuli. Limited information is available regarding the interaction of tumor aggregates and endothelium, as well as the subsequent events (such as transendothelial invasion or proliferation in situ) that follow adhesion.…”

Characterization of vascular permeability using a biomimetic microfluidic blood vessel model

“…17,18 Another work uses an endothelial cell layer to study monocyte adhesion and transmigration. 19 Blood vessel endothelium is constantly exposed to FSS at its apical side due to blood flow. The mechanical stress generated on the EC layer due to this flow is an important extrinsic factor capable of modifying vessel barrier properties through alteration of the inter-endothelial junctions and the EC-extracellular matrix interactions.…”