Unconventional Neurogenic Niches and Neurogenesis Modulation by Vitamins

Abstract

Although the generation of new neurons occurs in adult mammals, it has been classically described in two defined regions of the brain denominated neurogenic niches: the subventricular zone of the lateral ventricles and the subgranular zone of the dentate gyrus. In these regions, neural stem cells give rise to new neurons and glia, which functionally integrate into the existing circuits under physiological conditions. However, accumulating evidence indicates the presence of neurogenic potential in other brain regions, from which multipotent precursors can be isolated and differentiated in vitro. In some of these regions, neuron generation occurs at low levels; however, the addition of growth factors, hormones or other signaling molecules increases the proliferation and differentiation of precursor cells. In addition, vitamins, which are micronutrients necessary for normal brain development, and whose deficiency produces neurological impairments, have a regulatory effect on neural stem cells in vitro and in vivo. In the present review, we will describe the progress that has been achieved in determining the neurogenic potential in other regions, known as unconventional niches, as well as the characteristics of the neural stem cells described for each region. Finally, we will revisit the roles of commonly known vitamins as modulators of precursor cell proliferation and differentiation, and their role in the complex and tight molecular signaling that impacts these neurogenic niches.

Keywords: Differentiation; Neural stem cell; Neurogenesis; Niche; Vitamins.

Figure 1. Classical and unconventional neurogenic niches

A: longitudinal view of a rat brain and part of the spinal cord, indicating cross sections. B: Cross sections of spinal cord (a), cerebellum (b) and rat brain (c, d) at different levels. Regions where neurogenic potential or NSC presence has been demonstrated are highlighted in green. Spinal cord central canal (1), Purkinje cell layer (2), substantia nigra (3), SVZ of the lateral ventricles (4), SGZ of the dentate gyrus (5), amygdala (6) and hypothalamus (7). C: Cellular composition of the newly described neurogenic niches: central canal (left panel) and hypothalamus (right panel).