Screening for differentially expressed microRNAs in BALF and blood samples of infected COVID‐19 ARDS patients by small RNA deep sequencing

BACKGROUND: The pandemic COVID‐19 has caused a high mortality rate and poses a significant threat to the population of the entire world. Due to the novelty of this disease, the pathogenic mechanism of the disease and the host cell's response are not yet fully known, so lack of evidence prevents a definitive conclusion about treatment strategies. The current study employed a small RNA deep‐sequencing approach for screening differentially expressed microRNA (miRNA) in blood and bronchoalveolar fluid (BALF) samples of acute respiratory distress syndrome (ARDS) patients. METHODS: In this study, BALF and blood samples were taken from patients with ARDS (n = 5). Control samples were those with suspected lung cancer candidates for lung biopsy (n = 3). Illumina high‐throughput (HiSeq 2000) sequencing was performed to identify known and novel miRNAs differentially expressed in the blood and BALFs of ARDS patients compared with controls. RESULTS: Results showed 2234 and 8324 miRNAs were differentially expressed in blood and BALF samples, respectively. In BALF samples, miR‐282, miR‐15‐5p, miR‐4485‐3p, miR‐483‐3p, miR‐6891‐5p, miR‐200c, miR‐4463, miR‐483‐5p, and miR‐98‐5p were upregulated and miR‐15a‐5p, miR‐548c‐5p, miR‐548d‐3p, miR‐365a‐3p, miR‐3939, miR‐514‐b‐5p, miR‐513a‐3p, miR‐513a‐5p, miR‐664a‐3p, and miR‐766‐3p were downregulated. On the contrary, in blood samples miR‐15b‐5p, miR‐18a‐3p, miR‐486‐3p, miR‐486‐5p, miR‐146a‐5p, miR‐16‐2‐3p, miR‐6501‐5p, miR‐365‐3p, miR‐618, and miR‐623 were top upregulated miRNAs and miR‐21‐5p, miR‐142a‐3p, miR‐181‐a, miR‐31‐5p, miR‐99‐5p, miR‐342‐5p, miR‐183‐5p, miR‐627‐5p, and miR‐144‐3p were downregulated miRNAs. Network functional analysis for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG), in ARDS patients' blood and BALF samples, showed that the target genes were more involved in activating inflammatory and apoptosis process. CONCLUSION: Based on our results, the transcriptome profile of ARDS patients would be a valuable source for understanding molecular mechanisms of host response and developing clinical guidance on anti‐inflammatory medication.