Stability of exosomes in the postmortem serum and preliminary study on exosomal miRNA expression profiling in serum from myocardial infarction cadavers

Exosome-encapsulated miRNAs could potentially be sensitive biomarkers of human diseases. Since a lipid bilayer membrane surrounds exosomes, the exosomal miRNA may stably exist in body fluids with diseases as well as biological fluids. Therefore, exosomal miRNA may be helpful for autopsy diagnosis. Assuming cadaver blood would be most useful, we initially examined serum exosome stability with regard to storage temperatures and periods. Characteristic analyses of the exosome revealed that exosomes and the content, miRNA, were stably preserved until at least three days when stored at below 20 °C. Subsequently, exosomal miRNA expression profiling was performed on the serum of acute myocardial infarction (AMI, 4 cases) autopsy bodies and on hemorrhagic shock bodies used as the control (CT, 3 cases). Results showed that significant twofold up- and downregulations of expression of 18 and 16 miRNAs were detectable in AMI as compared to the CT, respectively. miR-126-3p, which has been reported to be increased in serum of AMI patients and a mouse model, was one of the significantly upregulated miRNAs. Furthermore, dysregulation of exosomal miRNAs, such as miR-145-5p, miR-143-3p, and miR-222-3p, which are involved in cardioprotection, may be associated with AMI pathogenesis. These findings provide a novel perspective on the potential role of exosomal miRNA in determining the cause of death.