ABSTRACT
Background: Coronavirus disease 2019 (COVID-19) is caused by a novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It is known that host microRNAs (miRNAs) can be modulated to favor viral infection or to protect the host. Objective: The aim of this study was to identify differentially expressed circulating miRNAs in Brazilian patients with COVID-19 as potential biomarkers for diagnosis and severity. Methods: miRNAs were extracted from the blood plasma of eight patients with COVID-19 (four patients with mild/moderate COVID-19 and four patients with severe/critical COVID-19) and four healthy controls. The patients and controls were matched for sex and age. miRNA expression levels were detected using high-throughput sequencing. Differential miRNA expression and enrichment analyses were further evaluated. Results: A total of 18 human miRNAs were differentially expressed between patients with COVID-19 (n = 8) and controls (n = 4), with 13 significantly upregulated and five significantly downregulated miRNAs. miR-4433b-5p, miR-6780b-3p, miR-6883-3p, miR-320b, miR-7111-3p, miR-4755-3p, miR-320c, and miR-6511a-3p were the most important miRNAs found significantly involved in the PI3K/AKT, Wnt/β-catenin, and STAT3 signaling pathways, which have a crucial role in viral infections. Moreover, 42 miRNAs were differentially expressed between severe/critical patients with COVID-19 (n = 4) and mild/moderate patients with COVID-19 (n = 4). miR-451a, miR-101-3p, miR-185-5p, miR-30d-5p, miR-25-3p, miR-342-3p, miR-30e-5p, miR-150-5p, miR-15b-5p, and miR-29c-3p were the most important miRNAs found to be significantly involved in the Wnt/β-catenin, NF-κβ, and STAT3 signaling pathways, which play crucial roles in immune response and inflammation. Conclusions: Differentially expressed miRNAs found in this study may be used as potential biomarkers for the diagnosis and severity of COVID-19. Larger studies are needed to validate these miRNAs as biomarkers of COVID-19.