Effect of Exercise on Intermediate Filament Expression in the Skeletal Muscles of Rats with Sciatic Nerve Injury

[Purpose] This study examined the effect of exercise on intermediate filament expression in rat gastrocnemius muscles. [Subjects] After administering a crush injury to the sciatic nerve of male Sprague-Dawley rats, the rats were divided into experiment and control groups. [Methods] The experiment and control groups were made to exercise for 60 minutes daily for 5 days per week. Rats were sacrificed at 12 days, 19 days, 26 days and 61 days after sciatic nerve crush injury. Frozen sections of the gastrocnemius muscle were prepared. Immunohistochemical staining for desmin and vimentin, and enzyme histochemistry for nicotinamide adenine dinucleotide-tetrazolium reductase (NADH-TR) were used to visualize degeneration of skeletal muscles. [Results] Desmin was expressed during muscle degeneration and regeneration, whereas vimentin was expressed only during muscle regeneration. Muscle fibers in the experimental group were normal at 61 days after injury. In the NADH-TR reaction, the control group showed aggregated diformazan but the experimental group showed normal evenly distributed diformazan granules. At reinnervation, target fibers were found by the NADH-TR reaction in animals sacrificed 26 days after injury. [Conclusion] Our results indicate that running is an effective exercise for inducing the expression of intermediate filaments during regeneration of skeletal muscles.