The present work was performed to determine the ability of neurotrophic factors to allow axonal regeneration across a 15-mm-long gap in the rat sciatic nerve. Synthetic nerve guidance channels slowly releasing NGF and GDNF were fabricated and sutured to the cut ends of the nerve to bridge the gap. After 7 weeks, nerve cables had formed in nine out of ten channels in both the NGF and GDNF groups, while no neuronal cables were present in the control group. The average number of myelinated axons at the midpoint of the regenerated nerves was significantly greater in the presence of GDNF than NGF (4942 +/-1627 vs. 1199 +/-431, P < or = 0.04). A significantly greater number of neuronal cells in the GDNF group, when compared to the NGF group, retrogradely transported FluoroGold injected distal to the injury site before explantation. The total number of labelled motoneurons observed in the ventral horn of the spinal cord was 98.1 +/-23.4 vs. 20.0 +/-8.5 (P < or = 0.001) in the presence of GDNF and NGF, respectively. In the dorsal root ganglia, 22.7% +/- 4.9% vs. 3.2% +/-1.9% (P +/-0.005) of sensory neurons were labelled retrogradely in the GDNF and NGF treatment groups, respectively. The present study demonstrates that, sustained delivery of GDNF and NGF to the injury site, by synthetic nerve guidance channels, allows regeneration of both sensory and motor axons over long gaps; GDNF leads to better overall regeneration in the sciatic nerve.

A subpopulation of familial cases of amyotrophic lateral sclerosis has been linked to mutations in the gene encoding Cu/Zn superoxide dismutase (SOD1). There is in vitro evidence that certain SOD1 mutants, in addition to their normal dismutation function, show increased ability of the enzyme to act as a peroxidase. This reaction is sensitive to inhibition by copper chelators. To test this hypothesis in vivo, we administered the copper chelator d-penicillamine to a transgenic mouse model of familial amyotrophic lateral sclerosis overexpressing a mutated form of human SOD1. We demonstrate that oral administration of d-penicillamine is able to delay the onset of the disease and extend the survival of these mice. Histological studies also showed a decreased loss of facial motor neurons in d-penicillamine-treated transgenic mice, corroborating the slower evolution of the disease in these animals. These results suggest that copper chelators may benefit patients with familial amyotrophic lateral sclerosis linked to mutations in the SOD1 gene.

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