Primary olfactory mucosal cells promote axonal outgrowth in a three-dimensional assay

Among the possible sources of autologous cells and tissues for use in spinal cord injury grafts, one promising source is the olfactory mucosa containing olfactory ensheathing cells and neural progenitor cells. Olfactory mucosa transplantation for spinal cord injury has been effective in animal models and in pilot clinical trials. However, the contributions of olfactory ensheathing cells and neurons in olfactory mucosa are unclear. For the present study, we prepared primary olfactory mucosal cells and used a cortex-Matrigel coculture assay system to examine the axonal outgrowth of olfactory mucosa. Axonal outgrowth from cortical slices was significantly enhanced in olfactory mucosal cells compared with noncell controls and respiratory mucosal cells, which have few olfactory ensheathing cells and neurons. Axonal outgrowth was severely reduced after treatment with an antineurotrophin cocktail. A conditioned medium in the olfactory mucosa-derived cell group contained neurotrophin-3. Some olfactory ensheathing cells and almost all neurons were immunopositive for neurotrophin-3. Axons originating from cortical slices targeted mainly the astrocyte-like olfactory ensheathing cells. Our findings demonstrate that the axonal outgrowth effect of olfactory mucosa is supported by both olfactory ensheathing cells and neurons in olfactory mucosa.