RESUMO
BACKGROUND@#Electrical stimulation has been recommended as an effective therapy to prevent muscle atrophy after nerve injury. However, the effect of electrical stimulation on the proliferation of satellite cells in denervated muscles has not yet been fully elucidated. This study was aimed to evaluate the changes in satellite cell proliferation after electrical stimulation in nerve injury and to determine whether these changes are related to the restoration of myofiber cross-section area (CSA).@*METHODS@#Sciatic nerve crush injury was performed in 48 male Sprague-Dawley rats. In half (24/48) of the rats, the gastrocnemius was electrically stimulated transcutaneously on a daily basis after injury, while the other half were not stimulated. Another group of 24 male Sprague-Dawley rats were used as sham operation controls without injury or stimulation. The rats were euthanized 2, 4, and 6 weeks later. After 5-bromo-2'-deoxyuridine (BrdU) labeling, the gastrocnemia were harvested for the detection of paired box protein 7 (Pax7), BrdU, myofiber CSA, and myonuclei number per fiber. All data were analyzed using two-way analysis of variance and Bonferroni post-hoc test.@*RESULTS@#The percentages of Pax7-positive nuclei (10.81 ± 0.56%) and BrdU-positive nuclei (34.29 ± 3.87%) in stimulated muscles were significantly higher compared to those in non-stimulated muscles (2.58 ± 0.33% and 1.30 ± 0.09%, respectively, Bonferroni t = 15.91 and 18.14, P < 0.05). The numbers of myonuclei per fiber (2.19 ± 0.24) and myofiber CSA (1906.86 ± 116.51 μm) were also increased in the stimulated muscles (Bonferroni t = 3.57 and 2.73, P < 0.05), and both were positively correlated with the Pax7-positive satellite cell content (R = 0.52 and 0.60, P < 0.01). There was no significant difference in the ratio of myofiber CSA/myonuclei number per fiber among the three groups.@*CONCLUSIONS@#Our results indicate that satellite cell proliferation is promoted by electrical stimulation after nerve injury, which may be correlated with an increase in myonuclei number and myofiber CSA.
RESUMO
<p><b>BACKGROUND</b>Proprioception plays an important role in knee movements. Since there are controversies surrounding the overall recovery time of proprioception following surgery, it is necessary to define the factors affecting proprioceptive recovery after anterior cruciate ligament (ACL) reconstruction and to investigate the relationship between proprioception and muscle strength.</p><p><b>METHODS</b>A total of 36 patients who had their ACL reconstructed with a semitendinosus/gracilis graft (reconstructed group: 6 months post-surgery) and 13 healthy adults without any knee injury (control group) were included in the study. Knee proprioception was evaluated with a passive reproduction test. Isokinetic strength was measured using the Biodex System. Statistical analysis was used to compare proprioception of the reconstructed group versus the control group, and to define causal factors, including sex, hamstring/quadriceps ratio, and the course of injury before reconstruction. We also investigated the correlation between the passive reproduction error and quadriceps index.</p><p><b>RESULTS</b>There was a significant difference in proprioception between the reconstructed and control groups (P < 0.05). When the course of injury before reconstruction was less than 4 months, there was a linear correlation with proprioception 6 months after the operation (r = 0.713, P < 0.05). There was a positive correlation between post-surgery proprioception and the quadriceps index at 6 months post-surgery.</p><p><b>CONCLUSIONS</b>Impaired knee proprioception is observed 6 months after ACL reconstruction. Within 4 months of injury, early undertaking of reconstruction is associated with better proprioception outcome. Patients with enhanced proprioception have a better quadriceps index.</p>