What cells form the blood-brain barrier?

The cells that form the blood-brain barrier are primarily endothelial cells, which line the blood vessels in the brain. Unlike other endothelial cells found in the body, those in the brain are tightly joined by tight junctions, restricting the passage of substances from the bloodstream into the central nervous system. This selective permeability is crucial for maintaining the brain's microenvironment and protecting it from potentially harmful substances while allowing essential nutrients to pass through.

While other cell types contribute to the function and maintenance of the blood-brain barrier, such as astrocytes and microglia, it is specifically the endothelial cells that physically create the barrier itself. Astrocytes, for example, provide support and help regulate blood flow and nutrient transport but do not form the barrier structure. Microglia serve as the resident immune cells of the brain and play a role in immune defense but are not involved in creating the blood-brain barrier. Understanding the unique role of endothelial cells in this context is crucial for grasping how the blood-brain barrier functions in neurobiology.