REGENERATION INTO THE SPINAL-CORD OF TRANSECTED DORSAL-ROOT AXONS IS PROMOTED BY ENSHEATHING GLIA TRANSPLANTS

The permissivity of adult olfactory bulb to the ingrowth of olfactory axons could be due to the unique properties of ensheathing glia. To te st whether these glial cells could be used to promote axonal regenerat ion in a spontaneously nonregenerating system, we transplanted suspens ions of pure ensheathing cells into a rhizotomized spinal cord segment . Ensheathing cells were purified away from other cell types by immuno affinity, using anti-p75 nerve growth factor receptor. After laminecto my at the lower thoracic level, the spinal cord was exposed and one do rsal root (T10) was completely transected at the cord entry point. The root stump was microsurgically anastomosed to the cord and a suspensi on of ensheathing cells was transplanted in the spinal cord at the dor sal root entry zone. Three weeks after transplantation, numerous regen erating dorsal root axons were observed reentering the spinal cord. In growth of dorsal root axons was observed using DiI and antibodies agai nst calcitonin gene-related peptide and growth-associated protein. Pri mary sensory afferents invaded laminae 1, 2, and 3, grew through lamin ae 4 and 5, and reached the dorsal grey commissure and lamina 4 of the contralateral side. We did not observe regenerating axons within the ipsilateral ventral horn and dorsal column. Transplanted ensheathing c ells reached the same laminae as axons. Neither ensheathing cells nor regenerating axons invaded those laminae they did not inervate under n ormal circumstances. In conclusion, the regeneration of injured dorsal root axons into the adult spinal cord was possible after ensheathing glia transplantation. The use of ensheathing cells as stimulators of a xonal growth might be generalized to other central nervous system inju ries. (C) 1994 Academic Press, Inc.