Endogenous neural precursor cells in health and disease.

• Neural precursor cells accomplish important functions for brain tissue homeostasis. • Neural precursor cells provide new cells for the olfactory bulb and hippocampus (neurogenic role). • Neural precursor cells regulate brain functions through the release of soluble factors (non-neurogenic role). • In pathological conditions, neural precursor cells contribute to restraining tissue damage. • Neurodegenerative diseases and physiological aging are accompanied by neural precursor cell dysfunctions. Neurogenesis persists in the adult brain of mammals in the subventricular zone (SVZ) of the lateral ventricles and in the subgranular zone (SGZ) of the dentate gyrus (DG). The complex interactions between intrinsic and extrinsic signals provided by cells in the niche but also from distant sources regulate the fate of neural stem/progenitor cells (NPCs) in these sites. This fine regulation is perturbed in aging and in pathological conditions leading to a different NPC behavior, tailored to the specific physio-pathological features. Indeed, NPCs exert in physiological and pathological conditions important neurogenic and non-neurogenic regulatory functions and participate in maintaining and protecting brain tissue homeostasis. In this review, we discuss intrinsic and extrinsic signals that regulate NPC activation and NPC functional role in various homeostatic and non-homeostatic conditions. [ABSTRACT FROM AUTHOR]