Differential expression levels of miR-125a, miR-125b, and miR-let-7f in sputum and plasma as biomarkers for tuberculosis

Tuberculosis (TB) has long presented significant epidemiological challenges, and its control remains a complex issue. In recent years, the critical role of small RNAs , particularly microRNAs (miRNAs), in TB infection has gained considerable attention. These small RNAs are known for their stability in biological fluids, which underscores their potential as reliable biomarkers for disease diagnosis and monitoring. This study specifically evaluated the differential expression levels of key miRNAs—miR-125b, miR-125a, and miR-let-7—in TB patients. By examining their expression profiles, we aimed to assess the diagnostic efficiency of these small RNAs, highlighting their significance in the context of TB management. Eighty cases of active pulmonary TB and eighty matched controls (matched by age, race, and sex) were recruited from the Pulmonary Department of the Pasteur Institute of Iran. Sputum and serum samples were collected simultaneously from all participants. Total RNA was extracted for the analysis of differentially expressed miRNAs using reverse transcription-PCR (RT-PCR). The expression levels of each microRNA were compared between individuals, and binary logistic regression , along with receiver operating characteristic (ROC) curve analysis, was employed to assess their diagnostic potential. During TB infection, these miRNAs influence immune responses. miR-125b was overexpressed in both sputum and serum samples from TB patients ( P = 0.08; P < 0.0001). In contrast, both sputum and serum samples showed downregulation of miR-125a ( P < 0.0001; P < 0.0001) and miR-let-7f ( P < 0.0001; P = 0.008). Serum levels of miR-let-7f (sensitivity = 85 %; AUC = 0.886) and miR-125a (sensitivity = 83 %; AUC = 0.894) effectively predicted TB infection. However, sputum levels of miR-let-7f and miR-125a did not significantly differ between TB cases and controls, rendering them ineffective as biomarkers. Serum miR-125b levels were significantly higher in TB cases (sensitivity = 70 %; AUC = 0.791), while sputum levels exhibited minimal elevation and poor performance indices. Overexpression of miR-125b was observed in tuberculosis samples, while downregulation of miR-125a and miR-let-7f was confirmed. Significant differences in miR-let-7f and miR-125a expression were found in patients, underscoring their diagnostic potential. Serum samples proved to be more effective than sputum samples for biomarker assessment, suggesting that miRNAs could serve as valuable tools for rapid tuberculosis detection based on their diagnostic performance . Overall, identifying miRNA profiles under different conditions could pave the way for novel biomarkers in tuberculosis diagnosis , monitoring, and therapy.