Diagnostic potential of bronchoalveolar lavage fluid exosomal microRNAs for pneumonia in the intensive care unit

Abstract Early and appropriate antibiotic treatment reduces morbidity and mortality of pneumonia. However, early prediction of pulmonary infection remains a challenge for clinicians. Current clinical needs require the development and use of rapid and effective diagnostic indicators to accelerate the identification of pneumonia and process of microbiological diagnosis. MicroRNAs (miRNAs) in exosomes (EXOs) have become attractive candidates for novel biomarkers to evaluate the presence and progress of many diseases. We assessed their performance as biomarkers of pneumonia. Patients were divided into pneumonia group (with pneumonia) and control group (without pneumonia). We identified and compared two upregulated miRNAs in EXOs derived from bronchoalveolar lavage fluid (BALF) between the pneumonia and control groups (miR-17-5p, p=0.009; miR-193a-5p, p=0.031). Interestingly, miR-17-5p and miR-193a-5p in BALF-cell-debris pellets, BALF-EXO-free supernatants, total plasma, and plasma-EXOs did not differ significantly between both groups. In vitro experiments revealed that miR-17-5p and miR-193a-5p were strikingly upregulated in EXOs derived from macrophages stimulated by LPS. Receiver operator characteristic (ROC) curve analysis indicated that exosomal miR-17-5p (area under the curve, AUC: 0.753) and exosomal miR-193a-5p (AUC: 0.629) have acceptable diagnostic value. This study is one of the few studies on BALF-EXO-miRNAs in patients with pneumonia, providing potential diagnostic biomarkers and therapeutic targets for pneumonia.