Poster AA17 - In Vitro Blood Brain Barrier Model for Studying Ischemic Stroke

Introduction: The blood brain barrier (BBB) is a selectively permeable membrane that regulates the movement of ions, molecules, and cells between the blood and the brain, interconnected by tight and adherens junctions, resulting in high electrical resistance and low paracellular permeability. Ischemic stroke, one of the leading causes of long term disability in the United States, severely compromises the BBB. Following the stroke, the BBB exhibits heightened paracellular permeability, along with altered expression of barrier transporters and tight junction proteins, which are thought to increase brain injury. After the dissolution of the initial clot, therapeutic options become limited, despite over 7 million Americans over the age of 20 having experienced its debilitating effects. Part of the difficulty in the development of new therapeutics is limited ability to model how changes in BBB phenotype modulate the ability to deliver therapeutics. Using induced pluripotent stem cell derived brain microvascular endothelial-like cells (BMECs) we aim to develop an accurate predictive human model of the BBB following an ischemic stroke.

Materials and

Methods: A 3D microvessel platform is used consisting of a PDMS-based mold bonded to a glass coverslip, containing a 127 µm cylindrical channel embedded within a collagen I extracellular matrix. BMECs are then seeded within this channel creating a vascular lumen. The vessel is then maintained under constant shear flow. To model ischemia, the device is exposed to hypoxia in glucose reduced media (OGD) with no shear flow for 6 hours with a subsequent 24 hour recovery period. Barrier cell phenotype and barrier integrity are then assessed.

Results, Conclusions, and Discussions: This microvessel displays continuous tight junctions, a robust glycocalyx, and limited paracellular transport. Following OGD we see a breakdown of tight junctions and an increase in vascular permeability. Our findings align closely with in vivo observations, revealing a discernible breakdown of the BBB characterized by alterations in junction proteins and heightened permeability. Our model demonstrates a biphasic opening of the BBB, with an initial increase in permeability followed by a restoration of some barrier integrity before further break down occurs after reperfusion. This model fills a critical gap in the field by providing an accurate, human derived platform for studying ischemic stroke that could be used in future studies to explore how different central nervous system diseases impact ischemic stroke.

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