Olfactory Ensheathing Cells and CNS Regeneration The Sweet Smell of Success?

with OECs. These are the cells that ensheath the axons within the olfactory nerve and constitute the major glial component of the superficially located nerve fiber layer of the olfactory bulb. This property of the OEC to provide a permissive boundary between the PNS and CNS is The OEC, originally described by the Spanish histologist Blanes Viale at the end of the nineteenth century, shares properties with both Schwann cells and astrocytes (reviewed by Doucette, 1990). They have therefore tradi-Elegant experiments are often based on the simplest of tionally been regarded as a cell type that straddles the propositions. Nowhere is this truer than in the litany of divide between the glia of the PNS and CNS. However, studies, spawned by Cajal and Tello's classic peripheral whether it is still reasonable to regard CNS and PNS glia nerve transplant experiment, which suggested that the as entirely separate and exclusive lineages is uncertain regeneration of damaged CNS axons can be promoted given recent reports of the differentiation of CNS pro-by replacing an environment that inhibits regeneration genitors into Schwann cells (Keirstead et al., 1999). Mor-with one that encourages it. For the most part, these phologically, OECs bear a close resemblance to nonmy-studies have involved providing damaged CNS axons elinating Schwann cells. Both cells ensheath small with Schwann cells, the glial cells of the PNS where diameter axons (Ͻ1 ␮m) without forming myelin sheaths, axon regeneration occurs with much greater efficiency although there is much greater separation of individual than in the CNS. However, in recent years there has axons by Schwann cell cytoplasmic processes in pe-been a gathering interest in using olfactory ensheathing ripheral nerve than by OECs in the olfactory nerve. Simi-cells (OECs), the principal glial cell of the peripheral larly, in tissue culture the OEC expresses a distinctive olfactory system where axon growth not only occurs in antigenic profile that is most similar to that of the nonmy-response to injury but also occurs as a normal physio-elinating Schwann cell (Barnett et al., 1993; Heredia et logical process throughout the lives of healthy individual ., 1998). als. In this short article, we review the remarkable regen-Within the olfactory nerve fiber layer, OECs occur eration-promoting properties of transplanted OECs and alongside other nonensheathing glial cells with astrocyte-how these results have triggered a demand for a deeper like features. It is still unresolved the extent to which understanding of the basic biology …