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Transplantation of olfactory ensheathing cells (OECs) into photochemically damaged rat spinal cord diminished astrocyte reactivity and parenchyma cavitation. The photochemical lesion performed at T12--L1 resulted in severe damage to the spinal cord, so that during the first 15 days postoperation all rats dragged their hindlimbs and did not respond to pinprick. The maximal area and volume of the cystic cavities were lower in transplanted than in non-transplanted rats, not significantly at the T12--L1 lesion site, but significantly at T9--T10 and L4--L6 cord levels. The density of astrocytes in the grey matter was similar at T12--L1 and L4--L6 in non-transplanted and trans- planted rats, but lower in the latter at T9--T10 level. However, in non-transplanted rats all astrocytes showed a hypertrophied appearance, with long and robust processes heavily GFAP-positive, and overexpression of proteoglycan inhibitor of neuritogenesis, whereas in transplanted rats only a few astrocytes showed hypertrophy and the majority had short, thin processes. These results indicate that OECs transplanted into damaged adult rat spinal cord exert a neuroprotective role by reducing astrocytic gliosis and cystic cavitation.

Olfactory bulb ensheathing cell (OBEC) transplants promoted axonal regeneration in the spinal cord dorsal root entry zone and in the corticospinal tract. However, OBECs failed to promote abducens internuclear neuron axon regeneration when transplanted at the site of nerve fibre transection. In experiments performed in both cats and rats, OBECs survived for up to 2 months, lining themselves up along the portion of the regrowing axons proximal to the interneuron cell body. However, OBECs migrated preferentially towards abducens somata, in the direction opposite to the oculomotor nucleus target. OBECs seem to promote nerve fibre regeneration only where preferred direction of glial migration coincides with the direction of axonal growth towards its target.

Sciatic nerve resection leaving a 15 mm gap could not be repaired by bridging the stumps with a silicone tube prefilled with a laminin gel. However, when purified olfactory ensheathing cells (EC) were added to the gel filling the tube, successful axonal regeneration was observed in 50% of rats. With 12 mm gaps, regeneration occurred in 79% of rats with transplanted EC compared with 60% of those receiving collagen gel alone. Therefore, ECs help repair severe peripheral nerve injuries, in addition to their ability to promote axonal regeneration within the central nervous system.