Transplants and neurotrophic factors prevent atrophy of mature CNS neurons after spinal cord injury.

Axotomy of mature rubrospinal neurons leads to a substantial atrophy of these neurons within days after surgery. In addition, these neurons do not successfully regenerate following axotomy. The relationship of atrophy to regenerative failure is not clear, and the signals which regulate these events have not been identified. However, it is possible that the atrophy of these neurons plays a role in preventing regeneration. In the present study, we evaluated the hypothesis that interventions which have been shown to promote growth of axotomized CNS neurons are also capable of reversing the axotomy-induced atrophy. To test this hypothesis, adults rats received thoracic spinal cord hemisection alone or in combination with transplants of fetal spinal cord tissue and/or neurotrophic factor support. Our data indicate that application of either transplants or neurotrophic factors partially reverse the axotomy-induced atrophy in rubrospinal neurons, but that both interventions together reverse the atrophy completely. These results suggest that the same pathways that are activated to enhance growth of rubrospinal neurons after axotomy may also be involved in the maintenance of cell morphology.