How extracellular vesicles contribute to pulmonary fibrosis: miRNA-mediated mechanisms, diagnostic potential, and emerging therapeutic strategies.

Pulmonary fibrosis (PF) is a progressive interstitial lung disease driven by excessive fibroblast activation and extracellular matrix (ECM) deposition, for which pirfenidone and nintedanib slow but do not halt disease progression. Extracellular vesicles (EVs)-lipid bilayer-enclosed nanoparticles that shuttle microRNAs (miRNAs), proteins, and lipids between cells-are increasingly recognized as important mediators and potential modulators of fibrotic remodeling. On the pathogenic side, epithelial- and immune-cell-derived EVs can deliver pro-fibrotic miRNAs (e.g., miR-494-3p) that regulate transforming growth factor beta (TGF-β)/Smad and Wnt/β-catenin signaling, promoting fibroblast-to-myofibroblast transition and ECM accumulation. Conversely, selected mesenchymal stem cell-derived EV (MSC-EV) preparations have demonstrated anti-fibrotic effects in preclinical models through modulation of TGF-β/Smad signaling, M2 macrophage polarization, mitochondrial function, and epithelial-mesenchymal transition; a phase I clinical study has provided initial safety evidence for nebulized administration, although therapeutic efficacy in PF has not yet been established. Beyond MSC-EVs, plant-derived and milk-derived EVs have emerged as potential delivery platforms, although their applications remain largely preclinical. Meanwhile, EVs isolated from plasma, bronchoalveolar lavage fluid, sputum, and urine carry disease-associated molecular signatures that may serve as candidate biomarkers for PF detection or monitoring, but require further clinical validation. This review synthesizes recent evidence on the dual roles of EVs in PF pathogenesis and therapy, evaluates their potential diagnostic utility, and discusses translational hurdles-including cargo standardization, targeted delivery, and scalable manufacturing-that must be overcome for clinical adoption.