Figure 1.

Representative architecture of hematopoietic and neurogenic niches. (A) Hematopoietic niches are microenvironments into bone marrow stroma which support HSC quiescence and self-renewal. Endosteal niche is mainly composed of osteoblasts, osteoclasts, adipocytes, CAR cells, stromal cells, nestin⁺ MSC, altogether maintaining HSC in a quiescent state. In comparison, vascular niche located near to BM sinusoid vessels is composed of perivascular (nestin⁺) stromal cells and CAR cells favoring HSC activation and recruitment. Non-myelinating Schwann cells were also described to be involved in HSC maintenance. (B) The subventricular zone (SVZ) is one of the neurogenic niches in the adult brain. This neurogenic niche is in contact with ependymal cells that line the cerebrospinal fluid (CSF) circulating in the lateral ventricles. Neural stem cells (NSC) are localized in contact with this ependymal cell layer and with blood vessels. Type B cells or SVZ astrocytes proliferates thanks to asymmetric division giving rise to type C cells, or transit amplifying cells, which will further differentiate into type A cells or neuroblasts. During adult neurogenesis, these neuroblasts will proliferate and migrate toward the olfactory bulb or the striatum.