Transcutaneous application of carbon dioxide improves contractures after immobilization of rat knee joint

Transcutaneous carbon dioxide suppresses skeletal muscle atrophy in a mouse model of oral squamous cell carcinoma

Cancer cachexia causes skeletal muscle atrophy, impacting the treatment and prognosis of patients with advanced cancer, but no treatment has yet been established to control cancer cachexia. We demonstrated that transcutaneous application of carbon dioxide (CO2) could improve local blood flow and reduce skeletal muscle atrophy in a fracture model. However, the effects of transcutaneous application of CO2 in cancer-bearing conditions are not yet known. In this study, we calculated fat-free body mass (FFM), defined as the skeletal muscle mass, and evaluated the expression of muscle atrophy markers and uncoupling protein markers as well as the cross-sectional area (CSA) to investigate whether transcutaneous application of CO2 to skeletal muscle could suppress skeletal muscle atrophy in cancer-bearing mice. Human oral squamous cell carcinoma was transplanted subcutaneously into the upper dorsal region of nude mice, and 1 week later, CO2 gas was applied to the legs twice a week for 4 weeks and FFM was calculated by bioimpedance spectroscopy. After the experiment concluded, the quadriceps were extracted, and muscle atrophy markers (muscle atrophy F-box protein (MAFbx), muscle RING-finger protein 1 (MuRF-1)) and uncoupling protein markers (uncoupling protein 2 (UCP2) and uncoupling protein 3 (UCP3)) were evaluated by real-time polymerase chain reaction and immunohistochemical staining, and CSA by hematoxylin and eosin staining. The CO2-treated group exhibited significant mRNA and protein expression inhibition of the four markers. Furthermore, immunohistochemical staining showed decreased MAFbx, MuRF-1, UCP2, and UCP3 in the CO2-treated group. In fact, the CSA in hematoxylin and eosin staining and the FFM revealed significant suppression of skeletal muscle atrophy in the CO2-treated group. We suggest that transcutaneous application of CO2 to skeletal muscle suppresses skeletal muscle atrophy in a mouse model of oral squamous cell carcinoma.

Local application of a transcutaneous carbon dioxide paste prevents excessive scarring and promotes muscle regeneration in a bupivacaine-induced rat model of muscle injury

In postoperative patients with head and neck cancer, scar tissue formation may interfere with the healing process, resulting in incomplete functional recovery and a reduced quality of life. Percutaneous application of carbon dioxide (CO₂ ) has been reported to improve hypoxia, stimulate angiogenesis, and promote fracture repair and muscle damage. However, gaseous CO₂ cannot be applied to the head and neck regions. Previously, we developed a paste that holds non-gaseous CO₂ in a carrier and can be administered transdermally. Here, we investigated whether this paste could prevent excessive scarring and promote muscle regeneration using a bupivacaine-induced rat model of muscle injury. Forty-eight Sprague Dawley rats were randomly assigned to either a control group or a CO₂ group. Both groups underwent surgery to induce muscle injury, but the control group received no treatment, whereas the CO₂ group received the CO₂ paste daily after surgery. Then, samples of the experimental sites were taken on days 3, 7, 14, and 21 post-surgery to examine the following: (1) inflammatory (interleukin [IL]-1β, IL-6), and transforming growth factor (TGF)-β and myogenic (MyoD and myogenin) gene expression by polymerase chain reaction, (2) muscle regeneration with haematoxylin and eosin staining, and (3) MyoD and myogenin protein expression using immunohistochemical staining. Rats in the CO₂ group showed higher MyoD and myogenin expression and lower IL-1β, IL-6, and TGF-β expression than the control rats. In addition, treated rats showed evidence of accelerated muscle regeneration. Our study demonstrated that the CO₂ paste prevents excessive scarring and accelerates muscle regeneration. This action may be exerted through the induction of an artificial Bohr effect, which leads to the upregulation of MyoD and myogenin, and the downregulation of IL-1β, IL-6, and TGF-β. The paste is inexpensive and non-invasive. Thus, it may be the treatment of choice for patients with muscle damage.