Circulating Exosomal MicroRNAs as Potential Biomarkers for Pulmonary Embolism

Pulmonary embolism (PE) is difficult to diagnose due to nonspecific symptomatology and lack of accurate diagnostic tools. PE can be categorized into low-risk, submassive, and massive based on severity. Changes in several plasma and serum microRNAs (miRNA) are associated with PE, but most lack appropriate specificity for diagnostic utility. Given the emerging role of small extracellular vesicles (sEVs) in PE pathogenesis, we hypothesized that the microRNAs (miRs) circulating within these sEVs can be sampled to gain new information for biomarker studies and disease mechanisms. To address current technical limitations, we developed a novel high-yield size-exclusion chromatography (SEC) method for sEV isolation from small clinical plasma samples, and employed a non-biased method, RNA-Seq, to gain new information for RNA markers that have not been previously studied in the disease. Our goal was to establish the feasibility of the approach in a pilot study with pooled samples from a stratified (AHA criteria) patient population. We present information from sEV characterization studies of individual patient samples, and RNA-Seq data from the pools. PE patients had larger sEVs than healthy subjects. Small RNA sequencing of the sEV samples revealed differential miRNA expression patterns that correlated with PE severity and were predicted to be involved in PE pathology-related processes. Our data offer a first step toward identifying miRNA targets that may have utility in a miRNA biomarker panel for PE diagnosis, prediction of severity, treatment responses and adverse outcomes. This strategy can be extended to the detection of adverse effects and drug-drug interactions as well.