Cycling exercise and fetal spinal cord transplantation act synergistically on atrophied muscle following chronic spinal cord injury in rats

The potential of two interventions, alone or in combination, to restore chronic spinal cord transection-induced chang es in skeletal muscles of adult Sprague-Dawley rats was studied, l-iind limb skeletal muscles were examined in the following groups of animals: rats with a complete spinal cord transection (Tx) for 8 weeks; Tx with a dr-week delay before initiation of a 4-week motor-assisted cycling exercise (Ex) program; Tx with a il week delay before transplantation (Tp) of fetal spinal cord tissue into the lesion cavity; Tx with a dr-week delay before Tp and Ex; and uninjured control animals. Muscle mass, muscle to body mass ratios, and mean myofiber cross-sectional areas were significantly reduced 8 weeks after transection, Whereas transplantation of fetal spinal cord tissue dill not reverse this atrophy and exercise alone had. only a modest effect in restoring lost muscle mass, the combination of exercise and. transplantation significantly increased. muscle mass, muscle to body mass ratios, and mean myofiber cross-sectional areas in both soleus and plantaris muscles. Spinal cord injury (SCI) also caused changes in myosin heavy chain (MyHC) expression toward faster isoforms in both sulcus and plantaris and increased soleus myofiber succinate dehydrogenase (SDI-I) activity. Combined exercise and transplantation led to a change in the expression of the fastest MyHC isoform in soleus but bad no effect in the plantaris. Exercise alone and ill combination with transplantation reduced SDH activity to control levels in the sulcus. These results suggest a synergistic action of exercise and transplantation of fetal spinal cord tissue on skeletal muscle properties following SCI, even after an extended pr,st injury period before intervention.