Grafts of embryonic tissue into spinal cord: a possible strategy for treating neuromuscular disorders

The article describes various approaches used to bring about repair of damaged spinal cord by using embryonic grafts of neuronal tissue. One approach is to stimulate the host's neuronal elements to grow and regenerate. Indeed embryonic grafts have been found to reduce the effects of spinal cord injury, and promote regrowth of axons across a lesion site at least to a limited extent. Attempts have also been made to restore the loss of supraspinal influences with grafts from embryonic brain, and transplants of aminergic neurones have been shown to compensate for the loss of aminergic supraspinal inputs. Finally, it is possible to replace loss of highly specialised cells such as motoneurones by grafts of embryonic spinal cord. Grafted embryonic motoneurones are able to survive within adult host cord although both their chances of survival and maturation seem improved by prior depletion of the host motoneurones. They are able to innervate a skeletal muscle via its peripheral nerve if this is co-implanted at the site of grafting but no axon growth has yet been detected into the host ventral root. However, grafted embryonic neurones are able to migrate away from the graft to sites once occupied by missing motoneurones in the host anterior horn. Within the context of the treatment of neuromuscular disease, the research described suggests possible stratagems for the treatment of disorders such as amyotrophic lateral sclerosis, spinal muscular atrophies or poliomyelitis either by employing grafts that could release neuroactive substances which might prevent existing cells from dying, or even by replacing missing motoneurones with transplanted embryonic motoneurones.