Interaction of olfactory ensheathing cells with astrocytes may be the key to repair of tract injuries in the spinal cord: The 'pathway hypothesis'

Spinal Repair Unit, Institute of Neurology, UCL, Queen Square, London, WC1N 3BG, UK.
Journal of Neurocytology (Impact Factor: 1.94). 10/2005; 34(3-5):343-51. DOI: 10.1007/s11068-005-8361-1
Source: PubMed

ABSTRACT Transplantation of cultured adult olfactory ensheathing cells has been shown to induce anatomical and functional repair of lesions of the adult rat spinal cord and spinal roots. Histological analysis of olfactory ensheathing cells, both in their normal location in the olfactory nerves and also after transplantation into spinal cord lesions, shows that they provide channels for the growth of regenerating nerve fibres. These channels have an outer, basal lamina-lined surface apposed by fibroblasts, and an inner, naked surface in contact with the nerve fibres. A crucial property of olfactory ensheathing cells, in which they differ from Schwann cells, is their superior ability to interact with astrocytes. When confronted with olfactory ensheathing cells the superficial astrocytic processes, which form the glial scar after lesions, change their configuration so that their outer pial surfaces are reflected in continuity with the outer surfaces of the olfactory ensheathing cells. The effect is to open a door into the central nervous system. We propose that this formation of a bridging pathway may be the crucial event by which transplanted olfactory ensheathing cells allow the innate growth capacity of severed adult axons to be translated into regeneration across a lesion so that functionally valuable connections can be established.

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Available from: Geoffrey Raisman, Apr 23, 2015
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    • "During the development of the olfactory pathway, cytoplasmic processes of OECs form conduits expressing cell adhesion and extracellular molecules, including Gal-1 (Puche et al. 1996; St John & Key, 1999; Vincent et al. 2005). The growth-promoting pathways created by OECs are thought to facilitate fasciculation and elongation of new axons towards their bulbar targets (Key & St John, 2002; Li et al. 2005a,b; Vincent et al. 2005). Cell surface carbohydrates on primary olfactory axons act as ligands for bivalent carbohydrate-binding proteins, such as Gal-1 (Puche & Key, 1996; Puche et al. 1996; St John & Key, 1999). "
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    ABSTRACT: Continuous lifelong neurogenesis is typical of the vertebrate olfactory system. The regenerative ability of olfactory receptor neurons is dependent on the glial cell type specific to the olfactory pathway, designated 'olfactory ensheathing cells'. Several studies to date have focused on mammalian olfactory ensheathing cells, owing to their potential roles in cell-based therapy for spinal cord injury repair. However, limited information is available regarding this glial cell type in non-mammalian vertebrates, particularly anamniotes. In the current immunocytochemical study, we analysed the features of olfactory ensheathing cells in the zebrafish, Danio rerio. Fish provide a good model for studying glial cells associated with the olfactory pathway of non-mammalian vertebrates. In particular, zebrafish has numerous valuable features that enable its use as a prime model organism for genetic, neurobiological and developmental studies, as well as toxicology and genomics research. Paraffin sections from decalcified heads of zebrafish were processed immunocytochemically to detect proteins used in the research on mammalian olfactory ensheathing cells, including glial fibrillary acid protein (GFAP), S100, neural cell adhesion molecule (NCAM), polysialylated NCAM (PSA-NCAM), vimentin (VIM), p75NTR and galactin (Gal)-1. Notably, GFAP, S100, NCAM and Gal-1 were clearly observed, whereas no vimentin staining was detected. Weak immunostaining for PSA-NCAM and p75NTR was evident. Moreover the degree of marker expression was not uniform in various tracts of the zebrafish olfactory pathway. The immunostaining patterns of the zebrafish olfactory system are distinct from those of other fish to some extent, suggesting interspecific differences. We also showed that the olfactory pathway of zebrafish expresses markers of mammalian olfactory ensheathing cells. The olfactory systems of vertebrates have similarities but there are also marked variations between them. The issue of whether regional and interspecific differences in immunostaining patterns of olfactory pathway markers have functional significance requires further investigation.
    Journal of Anatomy 02/2014; 224(2):192-206. DOI:10.1111/joa.12129 · 2.23 Impact Factor
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    • "which in turn lead to the loss of axonal connections [27] [28] [29] [30] [31] [32] [33] [34]. Hence, according to the above mentioned reasons, regeneration and recovery of damaged CNS may be much more difficult than PNS. "
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    ABSTRACT: As the field of nerve tissue engineering advances, new biomaterials and structures are required to improve the regeneration of damaged nerves. Carbon nanostructures have been recognized as potential candidates to develop neural prostheses due to their one-dimensional nanostructures and similar nanoscale dimensions to neuritis as well as their unique electrical and mechanical properties when being used as a scaffold. This review addresses the promising application of carbon nanostructures in the repair of injured nerves. As a new viewpoint, the possibility of utilizing carbon nanostructures to repair a long gap in a severed nerve will be discussed as well.
    Ceramics International 04/2012; 38(8):6075-6090. DOI:10.1016/j.ceramint.2012.05.038 · 2.09 Impact Factor
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    • "During development, the pathways of olfactory nerves are formed by conduits of OEC cytoplasmic processes expressing cell adhesion and extracellular molecules, among which Gal-1 is found (Puche et al. 1996; St John and Key 1999; Vincent et al. 2005). These growth-allowing pathways created by OECs are thought to facilitate fasciculation and elongation of new axons toward their bulbar targets (Key and St John 2002; Li et al. 2005a, b; Vincent et al. 2005). Cell surface carbohydrates present on primary olfactory axons are considered ligands for bivalent carbohydrate-binding proteins such as Gal-1 (Puche and Key 1996; St John and Key 1999). "
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    ABSTRACT: In the olfactory system of vertebrates, neurogenesis occurs throughout life. The regenerating activities of the olfactory receptor neurons are connected to particular glial cells in the olfactory pathway: the olfactory ensheathing cells. A considerable number of studies are available in literature regarding mammalian olfactory ensheathing cells; this is due to their potential role in cell-based therapy for spinal cord injury repair. But very little is known about these cells in non-mammalian vertebrates. In this study we examined the immunocytochemical characteristics of the olfactory ensheathing cells in fish, which provide a good model for the study of glial cells in the olfactory pathway of non-mammalian vertebrates. Paraffin sections from decalcified heads of Poecilia reticulata (microsmatic fish) and Carassius auratus (macrosmatic fish) were processed to immunocytochemically detect ensheathing cell markers used in research on mammals: GFAP, S100, NCAM, PSA-NCAM, vimentin, p75NTR and galectin-1. GFAP, S100 and NCAM were clearly detected in both fish, though the intracranial tract of the primary olfactory pathway of Carassius appears more S100 stained than the extracranial tract. P75NTR staining is more evident in Poecilia, PSA-NCAM positivity in Carassius. A slight vimentin immunostaining was detected only in Carassius. No galectin-1 staining appeared in the olfactory pathways of either fish. This study shows that some markers for mammalian olfactory ensheathing cells also stain the olfactory pathway in fish. Immunocytochemical staining differs in the two fish under examination, even along the various tracts of the olfactory pathway in the same species.
    Brain Structure and Function 04/2012; 218(2). DOI:10.1007/s00429-012-0414-5 · 4.57 Impact Factor
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