Olfactory Ensheathing Cells: Factors Influencing the Phenotype of These Glial Cells
The glial cells that provide ensheathment for olfactory axons in both the peripheral and central portions of the primary olfactory pathway are referred to as ensheathing cells (Doucette, 1984, 1990). When examined in cross-section, olfactory fascicles in both the PNS and CNS often contain several ensheathing cell perikarya, the cytoplasmic processes of which extend toward the centre of the fascicles enclosing variable numbers of axons within each mesaxon. Whereas the olfactory fascicles of the PNS are separated by fibroblasts and collagen fibres and are each enclosed within a basal lamina covering, the corresponding fascicles of the CNS are separated only by the perikarya and cytoplasmic processes of astrocytes, there being no intervening basal lamina (Doucette, 1992). In the PNS, the ensheathing cells within each olfactory fascicle collectively contribute to the assembly of the basal lamina that surrounds the entire fascicle (DeLorenzo, 1957; Frisch, 1967). This multicellular contribution to basal lamina formation in olfactory fascicles differs markedly from that of other peripheral nerves where each individual Schwann cell is enclosed within its own basal lamina (Eames and Gamble, 1970; Peters et al., 1990). It resembles more the manner in which astrocytes form a basal lamina at the glia limitans (Peters et al., 1990).
KeywordsGlial Fibrillary Acidic Protein Schwann Cell Olfactory Bulb Basal Lamina Olfactory System
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