1. Department of Sports Medicine, China Medical University, Taichung City, Taiwan.
2. Department of Orthopedic Surgery, China Medical University Hospital, Taichung City, Taiwan.
3. School of Medicine, China Medical University, Taichung City, Taiwan.
4. Spine Center, China Medical University Hospital, China Medical University, Taichung City, Taiwan.
5. Program of Biotechnology and Biomedical Industry, China Medical University, Taichung, Taiwan.
6. Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan.
7. Department of Medical Research, Chung Shan Medical University Hospital, Taichung, Taiwan.
8. Department of Pharmacology, School of Medicine, China Medical University, Taichung City, Taiwan.
9. Chinese Medicine Research Center, China Medical University, Taichung City, Taiwan.
10. Department of Biotechnology, College of Health Science, Asia University, Taichung City, Taiwan.
A balance between muscle injury and regeneration is critical for sustaining muscle function during myogenesis. Melatonin is well recognized for its involvement in neuroprotective activities, immune system regulation and suppression of inflammatory responses. This study set out to provide evidence that melatonin improves muscle regeneration during skeletal muscle differentiation. We began with cloning a stable cell line expressing Pax7 knockdown C2C12 cells. We then investigated markers of muscle degradation and regeneration after treating growth medium and differentiated medium with melatonin. Bioinformatics analysis of RNA sequencing results revealed that melatonin regulates muscle differentiation and that Wnt cascades are involved in the mechanism of muscle differentiation. Screening of miRNA online databases revealed that miR-3475-3p is a specific binding site on Pax7 and acts as a negative regulator of Pax7, which is involved in melatonin-induced muscle differentiation. We then investigated the effects of melatonin treatment in the early stage of glycerol-induced skeletal muscle injury in mice. Rotarod performance, micro-computed tomography and immunohistochemistry findings showed that melatonin-induced increases in Pax7 expression rapidly rescue skeletal muscle differentiation and improve muscle fiber morphology in glycerol-induced muscle injury. Our data support the hypothesis that melatonin rapidly rescues skeletal muscle differentiation and the melatonin/Pax7 axis could therefore serve as an important therapeutic target to optimize muscle healing after injury.
Keywords: melatonin, Pax7, muscle injury, differentiation, miR-3475-3p