Figure 1.

The typical components of the neurovascular unit (NVU) in the central nervous system (CNS). The NVU comprises (1) vascular cells, including endothelial cells (ECs) and mural cells, such as pericytes on capillaries and venules, or smooth muscle cells (SMCs) on arterioles and small arteries; (2) neuroglial cells, such as astrocytes; and (3) neurons. ECs form the luminal layer of the vessel wall. The space between adjacent ECs is held by paracellular junctions. The expression of some junctional proteins (including claudin-11, ZO-1, occludin, catenin, and VE-cadherin) is lower in the BSCB than in the BBB. At the arteriolar level (left inset), the basement membrane (BM) and SMC envelope endothelium. Astrocytic endfeet insert into the BM to regulate SMCs through the pia and the glia limitans. The capillary and venule (right inset) lack SMCs, where pericytes embed in the BM and wrap around the ECs on the abluminal side. The astrocytic endfeet attach to the pericytes at both venules and capillaries. Pericyte coverage is less on the BSCB than on the BBB. SMCs, pericytes, and astrocytes all receive neuronal innervation to control their function. In addition, these conformations of cells are also the major cellular structure of the blood–central nervous system barrier.