Aim: miRNAs are potential biomarkers of several diseases. This review aimed to identify the miRNAs that could serve as biomarkers of COVID-19. Materials & methods: A literature search of nine databases was carried out for studies published before 13 June 2021 that described dysregulated miRNAs in cells or animals infected by SARS-CoV-2 or in patients with COVID-19. Two independent reviewers selected the studies and extracted data; disagreements were resolved by a third reviewer. Results: Twenty studies were included in this scoping review; results suggested that miR-21-5p, miR-146a, miR-126-3p, miR-144 and miR-155 are the most important dysregulated miRNAs that could serve as biomarkers for diagnosing and indicating the severity of COVID-19. miRNAs appear to play key roles in viral replication, proliferation of infected cells, immune response, inflammation and cardiovascular dysfunction. Conclusion: This review provides insights into the role of miRNAs as biomarkers in COVID-19 and the current status and future directions for research in this field.

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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.

Background. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel coronavirus which was identified as the infectious agent responsible for coronavirus disease 2019 (COVID-19). MicroRNAs (miRNAs) are small non-coding RNAs that can be potential biomarkers of several diseases. The aim of this scoping review was to identify which miRNAs could be biomarkers of COVID-19 and their roles. Methods. A literature search was performed based on PubMed, PubMed Central, BVS/BIREME, Web of Science, Scopus, EBSCOhost, ProQuest, Embase, and Cochrane Library for studies published until January 28th, 2021. Animal and human studies that described miRNAs as biomarkers of SARS-CoV-2 infection/COVID-19 were included. Studies with a purely computational approach were excluded. Results. A total of 1,797 records were identified, seven of which met the eligibility criteria. Six studies were conducted in humans (samples derived from blood) and one was performed in an animal model (lung tissue). The most important miRNAs identified were miR-195-5p, miR-618, miR-146a-5p, miR-21-5p, miR-15b-5p, miR-142-3p, miR-155, miR-208a, miR-499, miR-103a-2-5p, miR-200c-3p, miR-2115-3p, and members of the let-7 family. Among these miRNAs, miR-146a-5p, miR-21-5p, miR-15b-5p, and members of the let-7 family may be important as they were deregulated in more than one study. Dysregulated miRNAs appear to play key roles in viral replication, proliferation of infected cells, immune response, inflammation, or cardiovascular dysfunction. Conclusion. MiRNAs may be used as potential diagnostic or severity biomarkers, predictive biomarkers, biomarkers of T-cell immune response, and as therapeutic targets of COVID-19. Further studies are required to investigate and validate the role of miRNAs as biomarkers of COVID-19.