Therapeutic targeting of bleomycin‐induced pulmonary fibrosis by human bone marrow mesenchymal stem cell‐derived extracellular vesicles and/or pirfenidone: Impact of sex in mature adult mice

BACKGROUND AND PURPOSE: Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with limited therapeutic options. This study compared the therapeutic effects of bone marrow mesenchymal stem cell-derived extracellular vesicles (BM-MSC-EVs) with an IPF treatment, pirfenidone (PFD), in mature adult mice with established pulmonary fibrosis. EXPERIMENTAL APPROACH: Nine to 10-month old male and female C57BL/6 mice received an intranasal instillation of bleomycin (BLM) or saline on Days 0 and 7. Sub-groups of BLM-injured mice (n = 10 per group) were left untreated until Day 21 (d21) or d28 post-injury, or received an intranasal administration of BM-MSC-EVs (d21), once-daily oral PFD treatment (d21 to d27), or both treatments combined. Measures of lung compliance, inflammation and fibrosis were assessed at d28. KEY RESULTS: BLM-injured male and female mice had increased lung inflammation and interstitial transforming growth factor (TGF-β1), myofibroblast and extracellular matrix (ECM) accumulation, but reduced matrix metalloproteinase (MMP 9) activity and MMP9:TIMP-1 ratios at d21. These end-points were maintained at d28 in male mice but were resolved in female mice. BM-MSC-EVs alone or combined with PFD attenuated or significantly reduced the lung inflammation and fibrosis-related end-points in male mice and promoted lung MMP-9 activity in both sexes. In comparison, PFD alone partially but significantly reduced fibrosis progression but did not affect MMP or TIMP levels. CONCLUSIONS AND IMPLICATIONS: BM-MSC-EVs exerted anti-fibrotic effects in male mice, which were maintained with PFD co-administration. Treatment outcomes remained inconclusive in female mice. These findings highlight how ageing and sex influence therapeutic responses of EV-based therapies for IPF.