Modeling the Blood–Brain Barrier to Understand Drug Delivery in Alzheimer’s Disease

ABSTRACT The blood–brain barrier is a semipermeable barrier structure that lines the walls of brain microvessels. Although the blood–brain barrier plays a key role in protecting the brain from unwanted molecules, it simultaneously challenges the delivery of drugs into the brain. In addition, the blood–brain barrier has been shown to be dysfunctional in Alzheimer’s disease, the most common cause of dementia for which there is no cure. Mouse models of Alzheimer’s disease have played a central role in investigating disease-specific changes in the blood–brain barrier, but the translation of findings from mouse models into the human system is hindered by interspecies differences. In an effort to develop new drug delivery techniques and/or understand changes in the human blood–brain barrier in Alzheimer’s disease, several human blood–brain barrier in vitro models have been developed. These comprise primary and immortalized human endothelial cell-based models as well as human induced pluripotent stem cell-derived brain microvascular endothelial cell models. Both two and three-dimensional (2D and 3D) culture platforms have been established to better mimic the complexity of the brain. This chapter discusses the current blood–brain barrier models, their advantages and disadvantages as well as their potential to understand drug delivery in Alzheimer’s disease.