Analysis of plasma-derived small extracellular vesicle characteristics and microRNA cargo following exercise-induced skeletal muscle damage in men.

Extracellular vesicle (EV) cargo is known to change in response to stimuli such as muscle damage. This study aimed to assess particle size, concentration and microRNA (miR) content within small EV-enriched separations prepared from human blood taken before and after unaccustomed eccentric-biased exercise-induced muscle damage. Nine male volunteers underwent plyometric jumping and downhill running, with blood samples taken at baseline, 2, and 24 h post-exercise. EVs were separated using size exclusion chromatography (SEC) and their characteristics evaluated by nanoparticle tracking. No changes in EV size or concentration were seen following the muscle-damaging exercise. Small RNA sequencing identified 240 miRs to be consistently present within the EVs. RT-qPCR analysis was performed: specifically, for known muscle-enriched/important miRs, including miR-1, -206, -133a, -133b, -31, -208b, -451a, -486 and - 499 and the immune-important miR-21, -146a and - 155. Notably, none of the immune-important miRs within the EVs tested changed in response to the muscle damage. Of the muscle-associated miRs tested, only the levels of miR-31-5p were seen to change with decreased levels at 24 h compared to baseline and 2 h, indicating involvement in the damage response. These findings shed light on the dynamic role of EV miRs in response to exercise-induced muscle damage.