Circulating miRNAs as Biomarkers of Acute Muscle Damage in Rats.

Skeletal muscle damage is an often-occurring event. Diagnosis using the classic blood marker creatine kinase sometimes yields unsatisfactory results due to great interindividual variability. Therefore, the identification of reliable biomarkers is important. Our aim was to detect and characterize circulating miRNAs in plasma in response to acute notexin-induced muscle damage in rats. Real-time quantitative RT-PCR profiling led to the identification of miRNAs that were highly increased in plasma in response to notexin injection into several muscles, namely miR-1-3p, -133a-3p, -133b-3p, -206-3p, -208b-3p, and -499-5p, as well as miR-378a-3p and miR-434-3p. Peak values of miRNAs appeared 12 hours after injury, and were contained both in the vesicular and nonvesicular fractions of plasma. Receiver operating characteristic curve analysis showed that circulating miRNAs could accurately discriminate between damaged and nondamaged tissues. Furthermore, we tested the robustness of expression profiles in slow- and fast-type fibers. Upon inducing damage in slow- or fast-type muscle, we found that the damaged-muscle phenotype had a very limited impact on the miRNA response. Similarly, the circulating miRNAs selected were not affected by hemolysis or platelets, two pre-analytical factors known to affect plasma miRNA profiles. Taken together, our results show that circulating muscle-specific miRNAs, miR-378a-3p and miR-434-3p, are robust and promising biomarkers of acute muscle damage in rats.