Date Published: March 6, 2019
Publisher: Public Library of Science
Author(s): Daisuke Ito, Darren Carwardine, Jon Prager, Liang Fong Wong, Masato Kitagawa, Nick Jeffery, Nicolas Granger, Carlos E. Ambrósio.
Olfactory ensheathing cells are thought to support regeneration and remyelination of damaged axons when transplanted into spinal cord injuries. Following transplantation, improved locomotion has been detected in many laboratory models and in dogs with naturally-occurring spinal cord injury; safety trials in humans have also been completed. For widespread clinical implementation, it will be necessary to derive large numbers of these cells from an accessible and, preferably, autologous, source making olfactory mucosa a good candidate. Here, we compared the yield of olfactory ensheathing cells from the olfactory mucosa using 3 different techniques: rhinotomy, frontal sinus keyhole approach and rhinoscopy. From canine clinical cases with spinal cord injury, 27 biopsies were obtained by rhinotomy, 7 by a keyhole approach and 1 with rhinoscopy. Biopsy via rhinoscopy was also tested in 13 cadavers and 7 living normal dogs. After 21 days of cell culture, the proportions and populations of p75-positive (presumed to be olfactory ensheathing) cells obtained by the keyhole approach and rhinoscopy were similar (~4.5 x 106 p75-positive cells; ~70% of the total cell population), but fewer were obtained by frontal sinus rhinotomy. Cerebrospinal fluid rhinorrhea was observed in one dog and emphysema in 3 dogs following rhinotomy. Blepharitis occurred in one dog after the keyhole approach. All three biopsy methods appear to be safe for harvesting a suitable number of olfactory ensheathing cells from the olfactory mucosa for transplantation within the spinal cord but each technique has specific advantages and drawbacks.
Olfactory ensheathing cells, also known as olfactory glial cells, are found in the olfactory mucosa and olfactory bulb of mammals, and support axonal regeneration of olfactory sensory neurons throughout life [1–6]. In the normal olfactory system, olfactory ensheathing cells are able to guide newly growing olfactory nerve axons from the olfactory mucosa to the olfactory bulb, and interact with astrocytes at the level of the boundary with the olfactory bulb in the central nervous system (CNS). When transplanted, they can ensheath and myelinate regenerating axons in the spinal cord [7–9].
All three biopsy methods appear to be safe for harvesting mucosal olfactory ensheathing cells from dogs. Each provides a sufficiently large population of appropriate purity p75-positive cells for transplantation, but there are specific advantages and drawbacks associated with each technique.
The olfactory mucosa obtained from dogs using the three different methods described here can each yield sufficiently large populations of olfactory ensheathing cells without severe adverse effects for the animal. These methods are directly applicable to clinical trials using the naturally-occurring canine SCI model  and mucosal olfactory ensheathing cells as part of the treatment strategies for spinal cord repair.