Abstract 221: Exosomal MicroRNAs Drive Tromboembolism in Covid-19

Abstract

Introduction: Thromboembolic complications play a crucial role in the clinical outcome of COVID-19. Emerging evidence has shown that exosomal microRNAs (miRNAs) are functionally involved in several pathologic processes. Methods: To test the hypothesis that exosomal miRNAs are a key determinant of thrombosis in COVID-19, we enrolled 26 COVID-19 patients. The study was approved by the local Ethical Committees. Circulating exosomes were isolated as we previously described and validated by our group and levels of exosomal miRNAs, from a custom panel of miRNAs, were quantified by RT-qPCR and normalized to the expression of U18. Results: We divided our population in two groups based on serum D-dimer level on admission, using a previously published cut-off of 3 μg/ml. No significant differences in the main clinical characteristics were noted comparing patients with low (n=11) vs high (n=15) D-Dimer. Strikingly, we found that exosomal miR-424 was significantly upregulated whereas exosomal miR-103a, miR-145, and miR-885 were significantly downregulated in patients in the high D-dimer group compared to patients in the low D-Dimer group ( p<0.0001 ). Regression analysis confirmed these findings. Mechanistically, Tissue Factor (TF) was identified as a direct target of miR-145, while miR-885 targets the von Willebrand Factor (vWF). Equally important, miR-424 has been associated with hyper-coagulability whereas low levels of miR-103a have been observed in deep vein thrombosis, although precise mechanisms have not been defined for these miRNAs. Using a stepwise multiple regression analysis, exosomal miR-424 was an independent predictor of thromboembolic events ( i.e. pulmonary embolism and acute myocardial infarction ) in COVID-19 patients (Wald: 4.180; P<0.05 ), whereas miR-103a independently regulated D-dimer levels ( P<0.001 ). Conclusions: To our knowledge, this is the first study showing a significant contribution of exosomal non-coding RNAs in COVID19. Limitations of our study include the relatively small population and the fact that we did not determine the exact source of exosomes; nevertheless, we speculate that a main source could be represented by platelets and/or endothelial cells, which express these miRNAs in normal conditions.