Olfactory ensheathing cells for spinal cord repair: crucial differences between subpopulations of the glia

OECs for spinal cord repair: Is repairing the injured spinal cord by olfactory ensheathing cell (OEC) transplantation possible? A recent human trial in which a paralysed man regained some function after transplantation of partially purified OECs suggests that this therapy may be a successful approach (Tabakow et al., 2014). In another human trial in which olfactory mucosa lamina propria was transplanted, patients recovered some motor and sensory function (Wang et al., 2015). While these results show promise, it is clear that improvements are needed to provide patients with increased functional output. Strategies to improve the therapeutic use of OECs may include improving the purification of the OECs used for transplantation, using them in combination with growth factors to combat the inhibitory environment and improve axon growth, the use of nerve bridges, advanced physiotherapy and the use of exoskeleton robotics to reinforce functional connections. Of all these approaches, it is probably crucial that the purity of OECs is primarily addressed to ensure consistency in outcomes.

Uniform population of OECs for consistent results: The therapeutic potential for OECs to repair the injured spinal cord is encouraging, however to clarify the efficacy of the therapy it is important that uniform and consistent purity of OECs are obtained. Considering that OECs from the peripheral nerve and from the olfactory bulb have distinctly different behavioural characteristics (Windus et al., 2010) it is clear that the different subpopulations can exert varying effects. When the potential inclusion of accessory OECs is also considered in animal models of spinal cord repair, their differing capacity for phagocytosis of axon debris will introduce another variable that will likely produce variable outcomes and confound the analysis of the therapeutic effect of OECs. Therefore, in order to achieve a more thorough understanding of the therapeutic potential of OECs and to achieve consistent outcomes in spinal injury models, it is crucial that strategies are developed to optimize the purification of the different subpopulations of OECs. As the accessory olfactory nerve bundles project along the septum and medial surfaces of the olfactory bulb, one simple strategy to minimise the potential contamination by the accessory OECs is to avoid harvesting cells from the septum/medial nerve fibre layer and instead harvest cells from the turbinates and lateral margins of the olfactory bulb. By improving the purity of the OEC preparations, we are likely to achieve more consistent outcomes in animal spinal injury models.

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Ekberg JA, St John JA. Olfactory ensheathing cells for spinal cord repair: crucial differences between subpopulations of the glia. Neural Regen Res [serial online] 2015 [cited 2015 Oct 7];10:1395-6. Available from: http://www.nrronline.org/text.asp?2015/10/9/1395/165504

This work was supported by a Perry Cross Spinal Research Foundation grant to JSJ and an Australian Research Council Discovery Grant DP150104495 to JE and JSJ.