(69b) Stem Cell-Based Microfluidic Model of the Blood-Brain Barrier

The blood-brain barrier (BBB) is a term used to describe the highly selective interface between the microvasculature and brain tissue that is formed due to the expression of continuous tight junction proteins between the endothelial cells of the brain microvessels. Due to its unique properties, the BBB has been studied extensively by researchers using both in vivo and in vitro models. The in vivo models suffer from poor imaging capability and difficulties in studying individual factors due to the high complexity of these systems. On the other hand, the conventional in vitro assays cannot fully recapitulate the key physiological characteristics of the BBB such as three-dimensionality, the presence of flow, and high surface to volume ratio. Here we sought to use human induced pluripotent stem cell (hiPSC)-derived cells to develop a microfluidic BBB on a chip platform that mimics essential features of the human BBB. The hiPSC-derived brain microvascular endothelial cells (BMECs) used in our device to separate the apical (“blood”) and basolateral (“brain”) channels possess superior barrier properties compared to other primary and immortalized cells that are commonly used to model the BBB in vitro. The brain-mimicking environment on the basolateral side of the device contains hiPSC-derived astrocytes cultured in a 3-D hydrogel consisting of collagen and hyaluronic acid, which is critical for preserving the astrocytes in quiescent state. Using fluorescence microscopy, we confirmed the formation of a confluent BMEC monolayer and expression of requisite tight junction proteins. In addition, the BMECs in the device were able to form a tight barrier, reaching a transendothelial electrical resistance (TEER) value of 913.4±114.7 Ωxcm², as determined by impedance spectroscopy, and a sodium fluorescein permeability value of (7.2±0.7)x10^-7 cm/s after one day of culture in the device. The capacitance of the semipermeable cell membrane could also be determined using an equivalent electrical circuit model of the device. Current efforts are focused on utilizing this physiologically relevant platform to evaluate the effects of various molecules on fidelity of the barrier as well as adhesion and transmigration of circulating cancer cells across the BBB. In addition, the use of hiPSC-derived cells in our device will enable its use for applications such as modeling genetic diseases and fabricating patient-specific BBB on a chip devices.