The dynamic blood–brain barrier

With the endothelium as its central unit, the blood-brain barrier (BBB) is a complex multicellular structure separating the central nervous system (CNS) from the systemic circulation. Disruption of the BBB has now been implicated in a multitude of acute and chronic CNS disorders indicating the potentially devastating effects of BBB breakdown on brain function. However, the healthy BBB is not an impermeable wall, but rather a communication 'centre', responding to and passing signals between the CNS and blood. New studies are identifying BBB-specific transport pathways that tightly regulate the entry and exit of molecules to and from the brain. They are revealing a highly plastic barrier in which dynamic changes in BBB components like paracellular tight junction complexes can contribute to BBB maintenance. Here, we provide a succinct overview of the current state-of-play in BBB research and summarize novel findings into BBB regulation in homeostatic regulation of the brain.