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Introduction. Olfactory mucosa is considered a potential source of neural stem cells, since supported by peculiar glial cells, Olfactory Ensheathing Cells (OECs). Studies have shown that OECs share some common features with astrocytes and Schwann Cells (Ramon-Cueto and Avila 1998). The finding that OECs are a source of multiple Growth Factors (GFs) is very important as they play a decisive role in regeneration, promoting functional restoration in lesioned area (Raisman and Li 2007). Immunocytochemical investigations have reported that OECs express different markers and adhesion molecules (Pellitteri et. al., 2010). Therefore, OECs have attracted attention because of their remarkable neural plasticity. Materials and Methods. Primary OECs were prepared from neonatal rat olfactory bulbs. In some experiments were used GFs. Cells were identified by immunocytochemical procedures, using different antibodies and the results were highlighted by fluorescent microscopy. Results. Our in vitro studies have reported the ability of OECs to stimulate neuronal survival and neurite sprouting mediated through secretion of GFs; moreover, OECs have shown the capability to exert a protective effect on neurons exposed to stressed condition, such as hypoxia, simulating secondary events during spinal cord injury. Conclusion. These data suggest that OECs might be a suitable tool in cellular therapy for their exceptional ability to promote axonal regeneration and functional restoration making them attractive candidates for neurogenesis, in different neurological disorders or injured CNS.

Trigeminal proprioception related to rodent macrovibrissae movements is believed to involve skin receptors on the whisker pad because pad muscles operate without muscle spindles. This study was aimed to investigate in rats whether the trigeminal mesencephalic nucleus (TMnu), which provides proprioceptive feedback for chewing muscles, may be also involved in whisker pad proprioception. Two retrograde tracers, Dil and True Blue Chloride, were injected into the mystacial pad and the masseter muscle on the same side of deeply anesthetized rats to label the respective projecting sensory neurons. This double-labeling technique was used to assess the co-innervation of both structures by the trigeminal mesencephalic nucleus (TMnu). In a separate group of anesthetized animals, the spontaneous electrical activities of TMnu neurons were analyzed by extracellular recordings during spontaneous movements of the macrovibrissae. Mesencephalic neurons (TMne) were previously identified by their responses to masseter muscle stretching. Changes in TMne spontaneous electrical activities, analyzed under baseline conditions and during whisking movements, were statistically evaluated using Student's t-test for paired observations. Neuroanatomical experiments revealed different subpopulations of trigeminal mesencephalic neurons: i) those innervating the neuromuscular spindles of the masseter muscle, ii) those innervating the mystacial pad, and iii) those innervating both structures. Extracellular recordings made during spontaneous movements of the macrovibrisae showed that whisking neurons similar to those observed in the trigeminal ganglion were located in the TMnu. These neurons had different patterns of activation, which were dependent on the type of spontaneous macrovibrissae movement. In particular, their spiking activity tonically increased during fan-like movements of the vibrissae and showed phasic bursting during rhythmic whisking. Furthermore, the same neurons may also respond to masseter muscle stretch. Results strongly support the hypothesis that the TMnu also contains first-order neurons specialized for relaying spatial information related to whisker movement and location to trigeminal-cortical pathways. In fact, the TMnu projects to second-order trigeminal neurons, thus allowing the rat brain to deduce higher-order information regarding executed movements of the vibrissae by combining touch information carried by trigeminal ganglion neurons with proprioceptive information carried by mesencephalic neurons.

Italian Journal of Anatomy and Embryology, Vol 115, No 1/2 (Supplement) 2010