MicroRNA expression in exhaled breath condensate differentiates between asthma and chronic obstructive pulmonary disease

Asthma and chronic obstructive pulmonary disease (COPD) have many common clinical characteristics, thus making reliable differentiation between these two challenging. The goal of this study is to determine the clinical value of exhaled breath condensate (EBC) derived miRNAs to discriminate between asthma and COPD. This cross-sectional study included 65 subjects each with asthma (mean/SD age: 39/13 years, Male<i>n</i>/%: 27/42%), COPD (mean/SD age: 61/9 years, Male<i>n</i>/%: 53/81%) and healthy controls (mean/SD age: 34.4/12 years, Male<i>n</i>/%: 50/77%). EBC was collected using R-tubes and 40 EBC samples from each group were used for miRNA profiling. Profiling data was curated and the most highly expressed miRNAs were shortlisted for further validation. Selected microRNAs were subsequently validated using quantitative-PCR in an independent set of 25 subjects from both disease groups. A total of 103 miRNAs were significantly upregulated in the EBC of asthma patients and 97 miRNAs were upregulated in the EBC of COPD patients compared to control group. However, miR-512-3p was downregulated and miR-517c was upregulated in COPD compared with asthma. The top unique miRNAs were shortlisted for further validation. Of these, miR-375 was upregulated in asthma, while miR-297, miR-367 and miR-539 were upregulated in COPD compared with healthy controls. Further, miR-512-3p was down-regulated and miR-517c was upregulated in COPD compared with asthma. The comparison exhibited excellent discriminatory power with 100% differential expression of miR-512-3p and miR-517c secreted by respiratory cells, they could be quantitated in EBC samples and used to differentiate between asthma and COPD.