The olfactory mucosa contains unmyelinated olfactory nerves with olfactory ensheathing cells (OECs) and sheet-like processes of olfactory nerve fibroblasts (ONFs). The OECs guide growing axons from the neurons of the nasal cavity olfactory mucosa to the olfactory bulb, to form synapses in the brain. Owing to their strong ability to guide axon outgrowth, OECs have been found to assist neuroregeneration in animal models of spinal cord injury and Parkinson's disease. Furthermore, OECs are pluripotent cells that can show Schwann cell–like properties. When transplanted into the demyelinated spinal cord, OECs can repair the defective myelin and restore conductance in remyelinated axons.
Human nasal polyp (hNP) samples (5 mm3, 0.5 g in weight) were collected in sterile boxes containing HBSS, for primary culture within 24 hours. The donated tissue was dissected into small pieces, under a dissecting microscope, and placed in a phosphate-buffered solution at room temperature. The tissue was then ground with a dissection scalpel and transferred into 10 ml DMEM/F12 medium containing trypsin and EDTA and shaken at 37°C in a water bath for 5 minutes. It was then rinsed with DMEM/F12 solution and triturated with a fire-polished Pasteur pipette. The ground tissue explants were collected by centrifugation at 600 g for 10 minutes. The resulting pellet was resuspended in DMEM/F12 medium containing B27 medium supplement, FCS (10%), and penicillin/streptomycin (1% (100 U/ml)) at 3 × 100,000 cells per ml culture medium. The tissue was placed in a flat 75-cm2 flask and incubated in 5% CO2 at 37°C. The tissue was left undisturbed for 5–7 days to allow for migration of the cells from the explants. These primary cells were passaged again once a week for 3–4 weeks.