Development and validation of a microfluidic brain-on-a-chip model for examining cerebral microvascular barrier response to the tumor microenvironment

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Line, Stacey
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Introduction: The BBB is composed of specialized endothelial cells that limit permeability of solutes across the BBB. Microfluidic technology that allows formation of 3D tubular microvessels has been applied to in vitro BBB models, having advantages of fluid flow, cell-cell contact, and can provide a more robust and predictive model for assessing vascular permeability. Methods: Human brain microvessel endothelial cells (hCMEC/d3) were seeded (10,000 cells/µL) into the vascular channel and various human brain tumor cell lines (SF8628, U87, and U251) were seeded in the adjacent brain channel of the microfluidic unit. Additionally, endothelial cells were seeded in 0.4um Transwell inserts (40,000cells/cm2). Tumor-induced alterations in barrier function were examined using paracellular and transcellularly transported dyes and correlated to changes of expression of selected BBB specific genes and secretome. Modulation of permeability using cadherin peptides was examined to determine potential for improving drug delivery across the BBB. Results: The microfluidic BBB culture model showed reduced permeability compared to TranswellTM inserts and comparable values to in vivo studies. Compared to monoculture, no significant changes in permeability were observed with U251 co-culture model. However, SF8628 enhanced barrier properties, while U87 increased paracellular leakiness. Examination of the barrier enhancing microenvironment observed with the SF8628 co-culture model indicated a Sonic Hedgehog dependent process. Increased levels of fatty acids seemed responsible at least in part, for the barrier diminishing effects in U87 co-culturing. Cadherin peptides increases permeability and were BBB endothelial cell selective. Conclusion: DMF model can be used to identify tumor-driven changes in brain endothelial cells.
Microfluidics, brain-on-a-chip model, co-cutlure, glioblastoma