Abstract A048: Development and validation of a microfluidic cell culture model for examining cerebral microvascular barrier responses to the tumor microenvironment
Authors: Line Stacey , Vanan Magimairajan Issai , Miller Donald W. 
Published: March 2024

Abstract
Introduction: The blood-brain barrier (BBB) is composed of specialized endothelial cells that limit the passage of solutes from the blood to the brain. Microfluidic technology that allows formation of 3D tubular microvessels has been applied to in vitro BBB models, and having advantages of fluid flow, cell-cell contact, provide a more robust and predictive model for assessing vascular permeability. Use of the microfluidic model to examine the effects of the tumor microenvironment on brain endothelial cell permeability would provide mechanistic fundamental knowledge that could be used to more effectively deliver therapeutic agents to the treatment site. Methods: Human brain microvessel endothelial cells (hCMEC/d3) were seeded (10,000 cells/µL) into the vascular channel and following vascular capillary tube formation, various human brain tumor cell lines (SF8628, U87, and U251) were seeded in the adjacent brain channel of the Mimeta 3-channel microfluidic unit. Tumor-induced alterations in barrier function were examined over a 72-hour period using paracellular (fluorescein-labeled detran-FDX70kD; IRdye 800; sodium fluorescein - NaF) and transcellularly transported dyes (rhodamine 800-R800). Tumor induced changes in permeability of various marker molecules were correlated to changes in the expression of selected BBB specific genes and the tumor secretome. Results: The microfluidic BBB culture model showed reduced permeability to all the permeability markers examined compared to TranswellTM inserts with values similar to those previously reported in vivo. 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 that stimulates the release of Angiopoietin 1 (Ang1) and Platelet derived growth factor (PDGF-BB) release from the SF8628 tumor cells as the likely factors driving the permeability effects observed. With regards to the increased permeability observed with the U87 co-culture, increased cytokines (ie. IL-6 and IL-8) and altered fatty acid secretion appear to play a significant role in the reduced barrier properties of brain endothelial cells. Conclusion: The brain tumor microenvironment can have either barrier enhancing (SF8628 co-culture) or barrier reducing (U87-co culture) effects based on tumor cell induced changes in secreted factors. The dynamic microfluidic blood-brain barrier - brain tumor co-culture model provides a robust system with which to mechanistically identify tumor-driven changes in brain endothelial cell permeability.
Citation Format: Stacey Line, Magimairajan Issai Vanan, Donald W. Miller. Development and validation of a microfluidic cell culture model for examining cerebral microvascular barrier responses to the tumor microenvironment [abstract]. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_1):Abstract nr A048.