Objective To assess the effect of electrical stimulation and weight-supported treadmill gait simulation on apoptosis in the muscles of rats with spinal cord injury.

Method Twenty seven rats with a model of complete spinal cord injury were assigned to one of the following groups: control (n=9), electrical stimulation (n=10), and exercise (n=8) groups. After a 2-week intervention period, they were sacrificed, and the pattern of apoptosis was analyzed by in situ DNA nick-end labeling (TUNEL), by DNA fragmentation assay, and by Western blot for Bax and Bcl-2 using specimens from the right hamstring muscles for all groups.

Results The electrical stimulation group had increased apoptosis compared to the control group possibly due to overwork weakness, but there was no statistical significance between the groups. Apoptosis decreased in the exercise group compared with in the electrical stimulation and control group. The expression of Bcl-2 was most prominent in the exercise group, and it was significantly reduced in the electrical stimulation and control group.

Conclusion These findings suggest that exercise could play an important role in decreasing apoptosis by the up-regulation of Bcl-2 protein expression and that electrical stimulation might cause overwork weakness in rat models of spinal cord injury.

Objective
To investigate the changes of apoptosis related factors after denervation and disuse in skeletal muscles and to find out the role of apoptosis in atrophic process. Method: 30 male Sprague-Dawley rats, 8 weeks of age were treated with three different atrophy models (10 rats in each group); hind-limbs suspension (HS) as a disuse model, complete denervation by sciatic nerve transsection (CD) and partial denervation by sciatic nerve crushing (PD). At 2 weeks and 4 weeks after each experiment, both gastrocnemius were dissected and their weights were measured. Western blotting for BAX and Bcl-2 and TUNEL assay were used to assess the changes of apoptosis related factors in muscle cell. Results: The muscle weight of PD and CD group decreased 38.6%, 65.6%, respectively, of intact side at 4 weeks after injuries. The loss of muscle weight in HS group was smaller than that of denervated muscles. CD group showed high expression of BAX (3.45±0.32→2.87±0.48) and Bcl-2 (3.63±0.40→3.33±0.50) at 2 and 4 weeks after denervation, but in PD group, BAX at 2 weeks significantly decreased at 4 weeks (3.40±0.55→2.13±0.25). In HS group, their expressions were slightly increased only immediate after 14 days suspension (BAX: 1.30±0.38 and Bcl-2: 1.29±0.28). CD group showed higher number of positive nuclei (27.6±8.8%) than PD group (10.4±5.3%) and HS group (4.4±1.6%) in TUNEL assay. Conclusion: Unlike temporary increase of apoptosis related factors in disuse, increase of these factors are remarkable and persisted after denervation. Muscle apoptosis may be the major cause of muscle atrophy during degeneration process. (J Korean Acad Rehab Med 2009; 33: 514-519)

Objective
To investigate the effect of exercise and steroid to the muscle of animal model of Duchenne muscular dystrophy.

Method: We used 15 mdx and 15 control mice. To grade exercise loading, control and mdx mice were divided into free-living, exercise and immobilization groups. Free-living and exercise groups were further divided into steroid-treated and sham-treated groups to evaluate the effect of steroid administration. We measured the apoptotic changes using in situ DNA nick-end labling (TUNEL), DNA fragmentation assay and western blots for Bcl-2 and BAX.

Results: With TUNEL method, the largest number of myonuclei became positive in sham-treated exercise group while apoptosis was significantly reduced in steroid-treated exercise group in mdx mice. Steroid-treated free-living group showed higher rate of apoptotic change than sham-treated free-living group. With western blots for Bcl-2 and BAX, the value of BAX/Bcl-2 ratio was highest in sham-treated exercise group and among free living mdx mice, it was higher in steroid-treated group than sham-treated one.

Conclusion: Apoptosis can be minimized in free living condition while exercise loading or immobilization can cause apoptotic change in muscular dystrophy animal model. Steroid administration induces apoptosis in free living muscle and it alleviates apoptotic damage caused by exercise loading in mdx mice. (J Korean Acad Rehab Med 2003; 27: 232-239)

Objective
To determine the effect of functional electrical stimulation (FES) in the paralyzed muscles of rabbits with spinal cord injury (SCI). Method: Fifteen male New Zealand white rabbits were injured by spinal cord transection at the T6 level. We classified animals into a normal control group (n=3), and SCI without FES (n=3), SCI with 10 Hz FES (n=6) and SCI with 40 Hz FES (n=6) groups. FES was applied on both tibialis anterior (TA) muscles at two frequencies (10 Hz, 40 Hz) for 1 hour daily for 2 weeks. After treatment TA muscles were separated and apoptotic features were measured by in situ DNA nick-end labeling (TUNEL), DNA fragmentation assays and western blotting for Bcl-2 and Bax protein. Results: In TUNEL and DNA fragmentation assay results, the FES groups showed more fragmented myonuclei and DNA, and western blotting showed more Bax protein expression in FES groups than no FES group and control (higher in 40Hz group), whereas Bcl-2 protein expressions were similar in all groups. Conclusion: Apoptosis of paralyzed muscle was increased in FES group with higher Bax/Bcl-2 in 40 Hz than in 10 Hz. To evaluate the clinical significance of muscle apoptosis with FES in SCI, further study would be needed. (J Korean Acad Rehab Med 2007; 31: 85-91)