TRANSPLANTED OLFACTORY ENSHEATHING CELLS REMYELINATE AND ENHANCE AXONAL CONDUCTION IN THE DEMYELINATED DORSAL COLUMNS OF THE RAT SPINAL-CORD

Olfactory ensheathing cells (OECs), which have properties of both astr ocytes and Schwann cells, can remyelinate axons with a Schwann cell-li ke pattern of myelin. In this study the pattern and extent of remyelin ation and the electrophysiological properties of dorsal column axons w ere characterized after transplantation of OECs into a demyelinated ra t spinal cord lesion. Dorsal columns of adult rat spinal cords were de myelinated by x-ray irradiation and focal injections of ethidium bromi de. Cell suspensions of acutely dissociated OECs from neonatal rats we re injected into the lesion 6 d after x-ray irradiation. At 21-25 d af ter transplantation of OECs, the spinal cords were maintained in an in vitro recording chamber to study the conduction properties of the axo ns. The remyelinated axons displayed improved conduction velocity and frequency-response properties, and action potentials were conducted a greater distance into the lesion, suggesting that conduction block was overcome. Quantitative histological analysis revealed remyelinated ax ons near and remote from the cell injection site, indicating extensive migration of OECs within the lesion. These data support the conclusio n that transplantation of neonatal OECs results in quantitatively exte nsive and functional remyelination of demyelinated dorsal column axons .