Muscle regeneration is undisturbed by repeated polytraumatic injury.

Introduction: Clinical observations suggest that repeated injury within a week after a traumatic event impairs the regeneration of tissues. Our aim was to investigate the effect of repeated trauma on the proliferation of satellite cells in skeletal muscle tissue.

Materials And Methods: Cold lesion injury was performed in the soleus muscle and in the motor cortex of anesthetized male Wistar rats 0, 1, or 2 times with 7 day intervals between the interventions. Following the last operation, 5-bromo-2'-deoxyuridine was injected i.p. for 6 or 12 days to label dividing cells. Gut epithelium was used as positive control. Immunohistochemistry was performed 1 and 5 weeks after the last injury and the sections were analyzed with confocal microscopy.

Results: In the case of repeated trauma, the percentage of proliferating cells remained the same compared to single hit animals after 1 week (28.0 ± 2.5% and 29.6 ± 3.0%) as well as after 5 weeks (13.9 ± 1.8% and 14.5 ± 2.2%).

Conclusion: The second hit phenomenon is probably due to systemic factors rather than to a diminished regenerating potential of injured soft tissues.