Small Extracellular Vesicle Release Following Electrical Pulse Stimulation of C2C12 Myotubes: Effects on microRNA Cargo and Myoblast Migration and Differentiation

The skeletal muscle (SkM) secretome has been widely studied since the establishment of its endocrine function. Extracellular vesicles (EVs) are the most recently identified elements of the SkM secretome. These nano-sized lipid-bound vesicles carry molecular cargo and function as a means of intercellular communication. The effect of exercise on SkM EV micro-RNA cargo (miRNAs) remains a challenge to elucidate. Electrical pulse stimulation (EPS) was applied to C2C12 myotubes at high (30 Hz) and low (2 Hz) frequencies. EVs released during 10 h of stimulation were isolated and characterized and used to treat myoblasts. Their miRNA cargo was sequenced. EVs were used to treat myoblasts (2.19 × 108 EVs per mL) to determine the effects on myoblast migration and differentiation. Sequencing revealed over 300 known miRNAs packaged into myotube EVs. Many were differentially expressed after EPS, either positively or negatively. Muscle-important miRNAs were present (miR-206 was 4.8-fold more prevalent than any other miRNA). EV treatments improved myoblast migration and differentiation without a frequency-specific influence. Gene Ontology analysis based on differentially expressed miRNAs between control and EPS-EVs indicates an effect of EPS frequency on muscle EV signaling.