Background and Purpose Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive interstitial lung disease, mainly affecting adult males. Although it exhibits a primarily fibrosing imprint, it serves as a model for understanding inflammation‐driven interstitial lung diseases that can evolve into PF. We analysed the interplay between inflammation and fibrosis, in relation to sex in a mouse model of PF. Experimental Approach Adult C57BL/6 mice of both sexes were treated with subcutaneous bleomycin injection (3 times a week for 1–4 weeks). We used RT‐PCR, western blotting and immunohistochemistry, along with ELISA, flow cytometry and mass spectrometry (UPLC‐MS/MS) to analyse our results. Key Results Male mice developed more severe fibrosis, with higher levels of collagen, and enhanced pulmonary epithelial–mesenchymal transition, compared with females. Males also showed early cell infiltration (neutrophils and macrophages) during the initial stages, followed by loss of lung architecture and an exacerbated development of fibrosis. In contrast, females exhibited physiological resolution of lung inflammation after 2 weeks of bleomycin treatment. In males, PF was associated with increased pro‐inflammatory/fibrotic mediators (TGF‐β and IL‐1β) and decreased anti‐inflammatory/anti‐fibrotic factors (IFN‐γ, miRNA‐214‐3p, miRNA‐96‐5p and PGE 2 ), particularly in the early phase of fibrosis. Pre‐treatment with pirfenidone reversed fibrosis features more effectively in males, impacting anti‐fibrotic miRNA‐214‐3p and miRNA‐96‐5p. Conclusions and Implications Our data suggest that while inflammation occurs in both males and females during the early stages of PF induction, exacerbated fibrosis is observed only in males. Additionally, pirfenidone demonstrated greater activity in male mice, highlighting the need to consider potential sex‐specific pharmacotherapy.
D’Avino et al. (Wed,) studied this question.