The neuronal stem cell of the olfactory epithelium

Abstract

The vertebrate olfactory epithelium neuronal progenitors-which are in close physical (OE) is a system in which behavior of neuronal proproximity to ORNs-can ''read'' the number of difgenitor cells can be observed and manipulated easily. ferentiated neurons in their environment and regulate It is morphologically and functionally similar to emproduction of new neurons accordingly. Putative neubryonic germinal neuroepithelia, but is simpler in that ronal stem cells of the OE have been identified in vitro, it produces large numbers of a single type of neuron, and studies of these cells indicate that ORNs produce the olfactory receptor neuron (ORN). The OE is amea signal that feeds back to inhibit neurogenesis. This nable to tissue culture, gene transfer, and in vivo surgiinhibitory signal may be exerted at the level of the cal approaches, and these have been exploited in exstem cell itself. Recent studies to identify this signal, periments aimed at understanding the characteristics as well as endogenous stimulatory signals that may of OE neuronal progenitor cells. This has led to the be important in regulating OE neurogenesis, are also realization that the ORN lineage contains at least discussed. ᭧ 1998 John Wiley & Sons, Inc. J Neurobiol 36: 190-three distinct stages of proliferating neuronal progeni-205, 1998 tor cells (including a stem cell), each of which repre-Keywords: neurogenesis; programmed cell death; neusents a point at which growth control can be exerted. ronal progenitor cells; stem cells; Mash1; fibroblast Neurogenesis proceeds continually in the OE, and growth factors; bone morphogenetic proteins; neurostudies in vivo have shown that this is a regulated trophins; Trk C; transgenic mouse process that serves to maintain the number of ORNs

Carnosine-related dipeptides in the mammalian brain

“…They are both part of the olfactory system and are characterized by striking structural plasticity, including neurogenesis, although a long term survival and incorporation of newly generated cells in the olfactory bulb neural circuits have not yet been demonstrated (Garcia-Verdugo et al, 1998;Peretto et al, 1999). Furthermore, both these sites are thought to contain a population of stem cells, although those isolated from the SEL appear to be multipotent (Weiss et al, 1996) whereas the putative stem cells of the olfactory neuroepithelium would be restricted to the neuronal lineage (Caggiano et al, 1994;Calof et al, 1998). On the other hand, remarkable differences also exist between these two populations of new formed cells.…”

“…This feature is linked to the existence of precursor cells in the basal layer of the olfactory neuroepithelium, which assure a continuous neurogenesis throughout life (Caggiano et al, 1994;Calof et al, 1998). However, among the different cell types existing in the olfactory mucosa (basal cells, supporting cells and receptor neurons at different maturation stages; Brunjes and Frazier, 1986;Calof et al, 1998; Fig. 1), the expression of carnosine is restricted to the mature olfactory receptor neurons, as confirmed by double labelling with specific immunocytochemical markers (Margolis, 1972).…”

“…For a long time these receptors were considered as a unique neuronal population capable of intense cell renewal, including a continuous growth of their axonal processes directed to the olfactory bulb (for review see Graziadei and Monti Graziadei, 1978;Brunjes and Frazier, 1986). This feature is linked to the existence of precursor cells in the basal layer of the olfactory neuroepithelium, which assure a continuous neurogenesis throughout life (Caggiano et al, 1994;Calof et al, 1998). However, among the different cell types existing in the olfactory mucosa (basal cells, supporting cells and receptor neurons at different maturation stages; Brunjes and Frazier, 1986;Calof et al, 1998; Fig.…”

Morphofunctional Adaptations of the Olfactory Mucosa in Postnatally Developing Rabbits

“…The supporting cells, which constitute a major population of OE-resident cells, act as glia to the epithelium (Vogalis et al, 2005) and serve other functions such as K þ transport and maintenance of water/salt balance in the neuroepithelium mucus layer (Menco et al, 1998;Rochelle et al, 2000;Vogalis et al, 2005). Previous reports indicate that the basal cells, which are situated deep within the OE, continually divide to replace the olfactory neurons (Graziadei and Monti Graziadei, 1978;Calof et al, 1998). However, it is not known whether the capacity of the basal cells changes with age.…”

Role of aquaporins in cell proliferation: What else beyond water permeability?

“…149,150 Likewise, it would not be surprising to find that other AQPs play a role in the differentiation/proliferation process of other stem-cell niches.…”