Human bone marrow mesenchymal stem cell-derived extracellular vesicles induce inverse dose-dependent anti-fibrotic effects in human myofibroblast cultures and bleomycin-injured mice with pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal condition associated with excessive interstitial collagen accumulation and irreversible lung function decline, for which there is no effective cure. Hence, this study evaluated the dose-dependent anti-fibrotic effects of bone marrow mesenchymal stem cell-derived extracellular vesicles (BM-MSC-EVs) in transforming growth factor (TGF)-β1-stimulated human dermal myofibroblasts (1 ×10⁷-1 ×10¹⁰ BM-MSC-EVs) and TGF-β1-stimulated lung myofibroblasts isolated from non-IPF versus and IPF patients (1 ×10⁶-1 ×10⁸ BM-MSC-EVs) after 72 h in culture; and when intranasally-administered therapeutically (from days 21-28 post-injury) to bleomycin (BLM)-injured mice (2.5 ×10⁸-2.5 ×10¹⁰ BM-MSC-EVs). In each case, changes in myofibroblast differentiation, collagen I deposition, matrix metalloproteinase (MMP)-2, MMP-9, tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 levels, and MMP-2:TIMP-2 and MMP-9:TIMP-1 ratios were assessed. BM-MSC-EVs significantly attenuated human dermal and non-IPF patient-derived lung myofibroblast differentiation and collagen I deposition in an inverse dose-dependent manner after 72 h, with the lowest doses evaluated inducing the strongest inhibitory effects. Similarly, BM-MSC-EVs therapeutically reduced the BLM-induced lung TGF-β1 expression and signal transduction, myofibroblast differentiation and collagen I deposition, and restored the BLM-induced loss of dynamic lung compliance in an inverse dose-dependent manner in vivo, after 7-days of treatment. BM-MSC-EVs promoted the MMP-2:TIMP-2 ratio in human dermal myofibroblasts or the MMP-9:TIMP-1 ratio in human lung myofibroblasts and the murine lung as part of their anti-fibrotic effects. Notably, BM-MSC-EVs failed to exert any anti-fibrotic effects in TGF-β1-stimulated lung myofibroblasts isolated from IPF patients. These findings suggested that BM-MSC-EVs may provide an anti-fibrotic treatment option for early-to-moderate IPF, but may not be effective against advanced IPF.