Sex-Specific Pathophysiological Signatures in Allometric Dosing-Controlled Bleomycin Acute Lung Injury Model.

Introduction: In acute lung injury (ALI), clinical data show that while mortality rates are similar between sexes, women require shorter ventilation times and intensive care unit stays than men, yet preclinical studies show conflicting sex-specific vulnerabilities. We reasoned that a hidden dosing bias may explain the inconsistency, as intratracheal bleomycin is scaled to body weight, even though lung mass grows more slowly than total body mass, so age-matched males, whose body mass outpaces lung growth, inevitably receive more drug per gram of lung than females. Methods: We compared age-matched (12-week) and body-weight-matched (~300g) Sprague-Dawley rats receiving intratracheal bleomycin (2.5mg/kg) or saline. Both cohorts underwent functional assessments (plethysmography, lung mechanics, arterial gases, histology) at day 7; weight-matched animals exclusively underwent mechanistic profiling (BALF analysis, cytokine multiplex, paired mRNA/miRNA-sequencing, immunoblotting). Results: Males developed worse hypoxemia (PaO Conclusions: Body-weight matching corrects unrecognized allometric bias affecting preclinical ALI sex-difference studies. Both cohorts demonstrated male vulnerability with worse hypoxemia and increased respiratory rates. Weight-matched molecular analyses revealed distinct responses: males showed significant miR-672-3p suppression with concurrent inflammatory mediator upregulation, including higher SERPINA3, IL-1β, and TNF-α. In contrast, females maintained higher miR-672-3p levels alongside elevated BMPR2/IL-10, suggesting that divergent post-transcriptional regulation contributes to functional differences and may inform sex-specific therapeutic strategies.