Reduced sensory neuron regeneration by C57BL/6J mice.

The tube repair method was used to study peripheral nerve regeneration in five different inbred mouse strains. The sciatic nerve of male adult mice of the C57BL/6J, DBA/1J, C3H/HeJ, BALB/cJ and A/J strains (N = 3) was cut and both proximal and distal nerve stumps were inserted into a polyethylene tube leaving a 4-mm nerve gap. After 6 weeks the tubes containing the regenerated nerve cables were processed for total myelinated axon counts. C57BL/6J mice regenerated significantly fewer myelinated axons (1024 +/- 178, mean +/- SEM) compared to the BALB/cJ (1618 +/- 64), A/J (1788 +/- 95), DBA/1J (2168 +/- 296) or C3H/HeJ (3468 +/- 36) strains. Horseradish peroxidase was applied 3 mm distal to the tube 4 and 40 weeks after tube implantation to further characterize the reduced regenerative response of C57BL/6J mice. Labeled sensory and somatic motor neurons were counted in the spinal cord and L4,5,6 dorsal root ganglia (DRG), respectively. Sciatic nerves from four intact C57BL/6J mice were processed in the same fashion and used as normal controls. No significant difference in the number of motor neurons was detected between the experimental (4 weeks = 663 +/- 74; 40 weeks = 770 +/- 35) and control non-operated (844 +/- 13) animals. However, there were fewer labeled neurons in the DRG of the operated group (4 weeks = 1163 +/- 167; 40 weeks = 2574 +/- 104) compared to the control group (4211 +/- 96). These results indicate that sensory neurons are responsible for the diminished regenerative response in C57BL/6J mice after peripheral nerve transection.(ABSTRACT TRUNCATED AT 250 WORDS)