Molecular hallmarks of lung cellular senescence in the bleomycin-induced and spirometry-confirmed mouse model of IPF

<bold>Aims and objectives:</bold> There is increasing evidence for senescent cells to play a contributory role in the pathogenesis of idiopathic pulmonary fibrosis (IPF). This study aimed to characterize key markers of pulmonary senescence across the disease spectrum in the bleomycin-induced and spirometry-confirmed mouse model of IPF. <bold>Methods:</bold> 12-week-old male C57BL/6JRj mice received a single intratracheal instillation of bleomycin (BLEO, 1.5 mg/kg) or saline (CTRL) on study day 1. BLEO-IPF animals were randomized into study groups based on % body weight loss on day 6 post-BLEO administration and terminated after 1, 2, 3, 4, or 5 weeks post-BLEO administration. Terminal endpoints included spirometry, hydroxyproline (HP), Ashcroft score, quantitative histological markers of fibrosis and cellular senescence as well as transcriptome signatures. <bold>Results:</bold> BLEO-IPF mice developed functional, histological, and biochemical hallmarks of IPF. RNA sequencing analysis indicated significant upregulation of key gene expression markers of the senescence-associated secretory phenotype (SASP), cell cycle arrest and DNA damage, being manifested from week 1 and sustained throughout the study. Molecular regulation of cellular senescence markers in BLEO-IPF mice were confirmed by quantitative histology for p21. Molecular hallmarks of lung cellular senescence in BLEO-IPF mice were in good agreement with data reported in IPF patients. <bold>Conclusions:</bold> The BLEO-IPF mouse model of IPF displays molecular signatures of lung senescence accompanied by impaired lung function and fibrosis, thus making it suitable for profiling potential senotherapeutics in preclinical drug discovery for IPF.