Neurogenesis in the Olfactory Epithelium

The olfactory sensory neurons in the olfactory epithelium generally live for only about 30–60 days. In addition, they are constantly killed by environmental insults such as pathogens and toxic substances and therefore need to be replaced throughout adult life. This unique capability of neuronal regeneration is due to the presence of olfactory stem cells localized in the basal layer of the olfactory epithelium which proliferate and differentiate into new olfactory sensory neurons. The newly generated neurons are able to extend their axons to the olfactory bulb, where they form synapses with the mitral cells. The olfactory ensheating cells, which are specialized olfactory glial cells, enclose the newly formed axons and help to direct them through the cribriform plate to the olfactory bulb. Because the olfactory epithelium is readily accessible from its location in the nasal cavity, it has been considered to be a potential source of basal stem cells and olfactory ensheating cells which could be used in therapeutic applications for the treatment of neurodegenerative diseases or to induce regeneration of injured axons.