DNA plasmid that codes for human Bcl-2 gene preserves axotomized Clarke's nucleus neurons and reduces atrophy after spinal cord hemisection in adult rats

Spinal cord injury in adult mammals causes atrophy or death of some axotomi zed neurons. The product of the antiapoptotic gene Bcl-2 prevents neuron de ath in vivo. We delivered Bcl-2 by intraspinal injection of a DNA plasmid e ncoding this gene to determine if axotomized neurons destined to undergo re trograde death could be rescued. Axons of the right side Clarke's Nucleus ( CN) were cut unilaterally in adult Sprague-Dawley rats by T8 hemisection, l eaving the contralateral (left) CN as an intact control. Two months postope ratively, there was similar to 35% loss of total CN neurons in the right L1 segment. Only 15% of large CN neurons (>400 mu m(2)), whose axons project to the cerebellum, survived-indicating atrophy and/or death of 85% of these cells. We injected a DNA plasmid encoding the human Bcl-2 gene and the bac terial reporter gene LacZ, which was complexed with cationic lipids, into t he right side of segment T8 of the normal spinal cord, or just caudal to th e hemisection site. The reporter gene was expressed in the perikarya of rig ht CN neurons at LI for up to 7 days, but not 14 days. Two months following T8 hemisection and Bcl-2/LacZ DNA injection, there was no significant loss of CN neurons ipsilateral to the lesion. Surprisingly, 61% of large neuron s survived, indicating partial protection from atrophy. In contrast, a DNA plasmid that codes for the LacZ reporter gene, but not Bcl-2, did not preve nt CN neuron death or atrophy. Administration of the Bcl-2 gene in adult ra ts and its expression in these CNS neurons prevents retrograde cell. death, and also minimizes atrophy. These results may serve as the basis for devel oping novel gene therapy strategies for patients with spinal cord injury. ( C) 1999 Wiley-Liss, Inc.