Cultures of rat olfactory ensheathing cells are contaminated with Schwann cells.

Implantation of cultured olfactory ensheathing cells into the damaged spinal cord of adult rats has been reported to remyelinate central axons. This observation is curious because olfactory ensheathing cells do not myelinate axons in their native environment. We have recently determined that calponin is the first definitive phenotypic marker for olfactory ensheathing cells. Primary cultures of adult rat olfactory mucosa and olfactory bulb were immunostained for p75 neurotrophin receptor and calponin. Our results reveal that two populations of p75 neurotrophin receptor-positive cells exist in primary cultures of the olfactory mucosa and bulb: calponin-positive olfactory ensheathing cells and calponin-negative Schwann cells. As olfactory tissues likely yield a mixed glial population, the idea that olfactory ensheathing cells are capable of de novo myelin synthesis after intraspinal implantation should be re-evaluated.