Transplanted embryonic stem cells survive, differentiate and promote recovery in injured rat spinal cord

Transplantation approaches using cellular bridges(1-2), fetal central nervo us system cells(3-5), fibroblasts expressing neurotrophin-3 (ref. 6), hybri doma cells expressing inhibitory protein-blocking antibodies: or olfactory nerves ensheathing glial cells(8) transplanted into the acutely injured spi nal cord have produced axonal regrowth or functional benefits. Transplants of rat or cat fetal spinal cord tissue into the chronically injured cord su rvive and integrate with the host cord, and may be associated with some fun ctional improvements(9). In addition, rats transplanted with fetal spinal c ord cells have shown improvements in some gait parameters(10) and the delay ed transplantation of fetal raphe cells can enhance reflexes(11). We transp lanted neural differentiated mouse embryonic stem cells into a rat spinal c ord 9 days after traumatic injury. Histological analysis 2-5 weeks later sh owed that transplant-derived cells survived and differentiated into astrocy tes, oligodendrocytes and neurons, and migrated as far as 8 mm away from th e lesion edge. Furthermore, gait analysis demonstrated that transplanted ra ts showed hindlimb weight support and partial hindlimb coordination not fou nd in 'sham-operated' controls or control rats transplanted with adult mous e neocortical cells.