The Blood–Brain Barrier: Composition, Properties, and Roles in Brain Health

Blood vessels are critical to deliver oxygen and nutrients to tissues and organs throughout the body. The blood vessels that vascularize the central nervous system (CNS) possess unique properties, termed the blood-brain barrier (BBB), which allow these vessels to tightly regulate the movement of ions, molecules, and cells between the blood and the brain. This precise control of CNS homeostasis allows for proper neuronal function and protects the neural tissue from toxins and pathogens, and alterations of this barrier are important components of the pathogenesis and progression of various neurological diseases. The physiological barrier is coordinated by a series of physical, transport, and metabolic properties possessed by the brain endothelial cells (ECs) that form the walls of the blood vessels. These properties are regulated by interactions between different vascular, perivascular, immune, and neural cells. Understanding how these cell populations interact to regulate barrier properties is essential for understanding how the brain functions in both health and disease contexts.