To address this challenge, we developed a 3D microfluidics-based brain-tissue model derived from human induced pluripotent stem cells (iPSCs). This approach leverages iPSCs to create a well-controlled system in which specific risk genes can be systematically studied. Key brain cell types—including endothelial cells, astrocytes, pericytes, microglia, neurons, and oligodendrocytes—are differentiated separately from iPSCs, encapsulated in a hydrogel, and self-assemble into 3D cellular architectures. This results in a fully integrated BBB with perfusable microvasculature in close proximity to neuronal cell types, resembling the organization of the human brain. Morphological characterization confirms vessel parameters consistent with human brain physiology, including junctional protein expression and neurovascular coupling. Functional assays demonstrate selective permeability that mirrors the in vivo BBB. As a case study, we apply this model to explore how capillary endothelial cells comprising the BBB respond to Alzheimer's associated insults on the peripheral side and alterations in glial support on the brain side. We identify transcriptomic and cellular alterations in the BBB in the context of Alzheimer’s disease and APOE4 risk-gene carriers.
In summary, this brain-on-chip model is uniquely suited to capture emergent tissue behaviors within the context of healthy vs. diseased states. By bridging molecular insights with mechanistic understanding, this platform offers a transformative tool for investigating neurodegenerative mechanisms and informing the development of brain-targeted therapeutic interventions.