Stem cells olfactory

The chemosensory stem cells give rise to several types of neuronal and non-neuronal cell lines under the influence of multiple organisers. From a ventro-lateral infolding, the olfactory pit is produced and this invagination soon becomes separated into two areas which will produce the main and accessory olfactory neurones [Figs. 4.2(a)-(d)]. 

FIGURE 29-5 In the adult rodent brain, dividing cells in the subventricular zone adjacent to the lateral ventricle migrate in the rostral migratory stream (RMS) and differentiate into olfactory neurons in the olfactory bulb (OB). This is one site of neuronal turnover in the adult that appears to result from persistent generation of neurons from adult CNS stem cells. CIS, cerebellum NC, neocortex. 

It seems that the cortex contains a crude "map" that relates position to the type of smell.912 The neural processing involved in the discrimination of odors is not yet clear.912 913 Intemeurons of the olfactory bulb are unusual, being continuously discarded and replaced by new neurons that arise from neural stem cells.908 914 This process seems to be essential for odor discrimination but not for the sensitivity of odor detection. 

Pagano SF, Impagnatiello F, Girelli M, Cova L, Grioni E, Onofri M, Cavallaro M, Etteri S, Vitello F, Giombini S, Solero CL, Parati EA (2000) Isolation and characterization of neural stem cells from the adult human olfactory bulb. Stem Cells 18 295-300 Parent JM (2003) Injury-induced neurogenesis in the adult mammalian brain. Neuroscientist... 

Today, with the exception of bone marrow for hematopoietic reconstitution, therapeutic cellular transplantation is an emerging technology. In recent years novel approaches in the potential restoration of function through cellular transplantation have included the use of fetal human or xenogeneic neural tissue for Parkinson s disease, ectopically implanted pancreatic islets for diabetes, Schwann cells and olfactory ensheathing glia for spinal cord injury, encapsulated chromaffin cells for pain, and various types of stem cells for the treatment of diabetes, cardiac disease, and central nervous system injuries or disease [2], There have also been trials of encapsulated cells to provide enzymes that either remove toxic products or provide activation of prodrugs to therapeutics, usually anticancer derivatives. 

Other cell sources have therefore been explored as alternatives. They include olfactory ensheathing cells, embryonic stem cells, mesenchymal stem cells [6,114], and even cell lines such as the immortalized SCTM41 Schwann cells [115]. Genetic modification has been considered for implanting cells as a constant source of growth factors. Most often, fibroblasts have been engineered with this intention, e.g., to produce neurotrophins, CNTF and FGF-2 [116, 117]. 

Previous studies in fetal tissue also contributed a great deal to the discovery of neural stem cells. Neural stem cells are derived from fetal and adult brain, and have the ability to divide and give rise to more stem cells or to several types of precursor cells, which can then become neurons and glia. Neural stem cells in the mammalian fetal brain have been located in the subventricular zone, ventricular zone, hippocampus, olfactory bulb, cerebellum, and cerebral cortex. 

Cell transplantation therapies examined for SCI repair include the use of olfactory ensheathing cells, Schwann cells, neural and embryonic stem cells, as described in the next several sections. 

Figure 2 Depiction of some components of the vertebrate olfactory epithelium in the nose. Odorants, e.g., carvone, deposit themselves in the mucous layer and interact with molecular receptors in the membrane of cilia of the olfactory receptor cells. Subsequent to intracellular signal transduction events, action potentials are sent via the olfactory axons to the olfactory bulbs in the brain. Supporting cells provide physical and physiological support for the olfactory neurons. Undifferentiated basal (stem) cells are the source of new supporting and olfactory receptor cells.

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