A specialized vascular niche for adult neural stem cells.

Stem cells reside in specialized niches that regulate their self-renewal and differentiation. The vasculature is emerging as an important component of stem cell niches. Here, we show that the adult subventricular zone (SVZ) neural stem cell niche contains an extensive planar vascular plexus that has specialized properties. Dividing stem cells and their transit-amplifying progeny are tightly apposed to SVZ blood vessels both during homeostasis and regeneration. They frequently contact the vasculature at sites that lack astrocyte endfeet and pericyte coverage, a modification of the blood-brain barrier unique to the SVZ. Moreover, regeneration often occurs at these sites. Finally, we find that circulating small molecules in the blood enter the SVZ. Thus, the vasculature is a key component of the adult SVZ neural stem cell niche, with SVZ stem cells and transit-amplifying cells uniquely poised to receive spatial cues and regulatory signals from diverse elements of the vascular system.