Figure 3. Regulation of blood-brain barrier (BBB) establishment and maturation by neural signals.
Neural progenitor cells secrete Wnt and Sonic hedgehog (Shh) ligands that activate formation of tight junctions and expression of BBB specific transporters (such as Glut1) within endothelial cells. Pericytes are important for maintaining endothelial tight junction and other BBB properties, but unlikely to be responsible for inducing BBB. Perictye-endothelial cell interaction is mediated by N-Cadherin, which is positively regulated by TGFβ/BMP/Smad4 signaling within endothelial cells.