Effects Of Ex-vivo Coculture Of Human Serum Following Acute Exercise On C2c12 Differentiation Potential

PURPOSE: Exercise is known to provide various benefits for skeletal muscle such as mitigating sarcopenia and healthy aging. However, the identification of the circulating molecules responsible for these health benefits is in its early stages. As a proof-of-concept study, here, we tested the effect of post-exercise serum on myoblast cell differentiation. The purpose of this study was to determine if ex-vivo co-culture of serum from exercised individuals would improve the differentiation of C2C12 myotubes. METHODS: Blood was collected before and after the exercise session of a recreationally trained male who cycled at ~80% VO2 max for 1 hour. Serum was isolated from the blood and stored at -80 °C for future cell culture experiments. When C2C12 myoblasts reached 80% confluency (day 0), the growth media was replaced and cultured in four serum conditions during differentiation to myotubes for 5 days. Myotube differentiation was measured by fusion index (number of nuclei per myofiber). The serum conditions were basal media with either no serum (NS), 2% horse serum (HS), 2% pre-exercise human serum (PRES), and 2% post-exercise human serum (POSTS). Participants were informed of all procedures and risks before signing an Institutional Review Board approved consent document that conformed to the Declaration of Helsinki. Two independent experiments were performed (n = 6). Student t-test was used to compare the mean values. RESULTS: Fusion index was ~33% higher on day 4 in the C2C12 cells in HS (0.045) than in NS (0.015, p < 0.001). Fusion index was ~110% higher on day 4 in the C2C12 cells incubated compared to human serum (0.41) than HS (0.045, p < 0.001). Fusion index was ~44% higher on day 4 in the C2C12 cells co-cultured with post-exercise serum (0.56) than those with pre-exercise serum (0.24, p < 0.001). CONCLUSIONS: Data showed a tendency for serum from individuals who exercised acutely to improve differentiation in C2C12 myoblasts more than serum from the same individual before exercise. Further research is warranted to 1) identify the specific molecules responsible for this phenomenon and 2) address whether these molecules are responsible for other health benefits of exercise. CLINICAL RELEVANCE: The present data suggest that the serum conditions after an acute endurance exercise session promote muscle regenerative potential.