Transcutaneous carbon dioxide application accelerates muscle injury repair in rat models

Purpose: Skeletal muscle injuries are commonly observed in sports and traumatology medicine. Previously, we demonstrated that transcutaneous application of carbon dioxide (CO₂) to lower limbs increased the number of muscle mitochondria and promoted muscle endurance. Therefore, we aimed to investigate whether transcutaneous CO₂ application could enhance recovery from muscle injury.

Methods: Tibialis anterior muscle damage was induced in 27 Sprague Dawley rats via intramuscular injection of bupivacaine. After muscle injury, rats were randomly assigned to transcutaneous CO₂-treated or -untreated groups. From each group, three rats were sacrificed at weeks one, two, four and six. At each time point, histology and immunofluorescence analyses were performed, and changes in muscle weight, muscle weight/body weight ratio, muscle fibre circumference, gene expression levels and capillary density were measured.

Results: Injured muscle fibres were completely repaired at week six in the CO₂-treated group but only partially repaired in the untreated group. The repair of basement and plasma membranes did not differ significantly between groups. However, expression levels of genes and proteins related to muscle protein synthesis were significantly higher in the CO₂-treated group and significantly more capillaries four weeks after injury.

Conclusion: Transcutaneous CO₂ application can accelerate recovery after muscle injury in rats.