Interaction of transplanted olfactory-ensheathing cells and host astrocytic processes provides a bridge for axons to regenerate across the dorsal root entry zone

A single fourth lumbar dorsal rootlet was transected at the entry point into the spinal cord. The nerve fibres were labelled with biotin dextran injected into the rootlet. An endogenous matrix containing olfactory-ensheathing cells (OECs) labelled with green fluorescent protein was applied to the opposing cut surfaces of the rootlet and the spinal cord, which were then brought into apposition and held in place by fibrin glue. Two weeks later, a ladderlike bridging structure has been formed by astrocytic processes growing out for about 200-300 microm from the spinal cord. The transplanted cells remained largely confined to this area. They were elongated along the nerve axis but did not enter the spinal cord itself. Labelled dorsal root axons crossed the repaired dorsal root entry zone in alignment with the bridging astrocytic processes and the transplanted cells and then proceeded beyond the transplant to enter the grey matter of the dorsal horn and send axons both rostrally and caudally for at least 10 mm in the white matter of the ascending dorsal columns.