The neurovascular unit and its growth factors: coordinated response in the vascular and nervous systems.

The nervous and vascular systems contain many common organizational features and develop similarly in terms of anatomical patterning. During embryogenesis and in regions of the brain undergoing postnatal neurogenesis, neural stem cells and endothelial cells are found in close proximity, or within a so-called vascular niche. The similarities in patterning and proximity may reflect coordinated development based on responsiveness to similar growth factors such as vascular endothelial growth factor, semaphorin, and ephrins/Ephs: molecules involved in the development and maintenance of both the nervous and vascular systems. Despite the blatant similarities between the vascular and nervous systems, little is still known about the co-dependence and/or interactions between the two systems during development and following alterations in metabolic demand as seen during aging, exercise, and disease processes. The interactions between the two systems involving common growth factors suggest these two systems have evolved in an interconnected way.