Matrix metalloproteinases levels in induced sputum in IPF and CTD-ILD.

BACKGROUND: The involvement of matrix metalloproteinases (MMPs) in the pathogenesis of interstitial lung disease (ILD) is well-supported, and circulating MMP-7 has been validated as a biomarker. Nonetheless, there is a lack of understanding regarding the local MMPs. METHODS: The consecutive cohort comprised 30 patients with idiopathic pulmonary fibrosis (IPF), 54 with connective tissue disease (CTD)-ILD, and 34 healthy subjects. Biomarker analysis of MMP-7, MMP-8, MMP-9, and pro-MMP-10 was conducted on both plasma and induced sputum (IS) samples. The correlation between IS MMP levels, pulmonary function, and sputum cell count in ILD patients was investigated. RESULTS: Significantly greater concentrations of MMPs were found in individuals with ILD compared to healthy participants. These markers were more abundant in induced sputum than plasma, with both IPF and CTD-ILD patients showing a higher median elevation in IS levels than those in the control group. The detection rate pro-MMP-10 in IS was significantly higher than in plasma (80.47% vs. 6.25%). In CTD-ILD patients, IS MMP-7 positively correlated with RV/TLC, total cell counts, and neutrophils%. IS MMP-9 showed positive correlations with total cell counts and neutrophils%. In IPF patients, IS MMP-7 levels correlated with RV/TLC, while IS MMP-9 levels correlated with FVC% pred, TLC%, and total cell counts. CONCLUSIONS: A notable increase of MMPs was observed in IS relative to plasma, correlated with inflammatory cells, lung function, and imaging features, implying that local MMPs evaluation could provide a more sensitive reflection of the pathophysiological changes in ILD.