Diagnostic potential of MMP-9, IL-8, and MPO in bronchoalveolar lavage fluid as combined biomarkers for pediatric post-infectious bronchiolitis obliterans

Abstract This study investigates the diagnostic potential of matrix metalloproteinase-9 (MMP-9), IL-8, and myeloperoxidase (MPO) in bronchoalveolar lavage fluid (BALF) as combined biomarkers for post-infectious bronchiolitis obliterans (PIBO) in children. BALF samples from children with PIBO were analyzed using ELISA to quantify MMP-9, IL-8, and MPO levels. Receiver operating characteristic (ROC) curves were used to assess their diagnostic values, while Pearson correlation analysis examined their associations with lung function and inflammation markers. A PIBO mouse model was established via nebulized nitric acid inhalation, and targeted inhibition of MMP-9, IL-8, and MPO using small interfering RNAs (siRNAs) was performed given via intratracheal administration. The effects on airway inflammation and pathological lung changes were evaluated. Bioinformatics analysis identified upstream microRNAs (miRNAs) regulating MMP-9, IL-8, and MPO, which were validated using dual-luciferase assay and Western blotting. Results revealed significant upregulation of MMP-9, IL-8, and MPO in the BALF of children with PIBO. Combined detection of these biomarkers demonstrated high diagnostic accuracy. MMP-9, IL-8, and MPO levels in BALF were negatively correlated with lung function indicators but positively correlated with inflammatory factors. Targeted inhibition of these molecules reduced airway hyperresponsiveness and inflammation in PIBO mice. miR-766-3p was downregulated in the lung tissues of PIBO mice and in the BALF of affected children, showing a negative correlation with MMP-9, IL-8, and MPO. Functional assays confirmed that miR-766-3p directly targeted MMP-9, IL-8, and MPO. In conclusion, MMP-9, IL-8, and MPO serve as reliable combined biomarkers for PIBO diagnosis and may aid in early clinical identification. miR-766-3p is an upstream miRNA for MMP-9, IL-8, and MPO.