Pulmonary Mechanics and Structural Lung Development after Neonatal Hyperoxia in Mice

BACKGROUND: Supplemental oxygen exposure administered to premature infants is associated with chronic lung disease and abnormal pulmonary function. This study used mild (40%), moderate (60%), and severe (80%) oxygen to determine how hyperoxia-induced changes in lung structure impact pulmonary mechanics in mice. METHODS: C57BL/6J mice were exposed to room air or hyperoxia from birth through postnatal day eight. Baseline pulmonary function and methacholine challenge was assessed at four and eight weeks of age, accompanied by immunohistochemical assessments of both airway (smooth muscle, tethering) and alveolar (simplification, elastin deposition) structure. RESULTS: Mild/moderate hyperoxia increased baseline airway resistance (40% only) and airway hyperreactivity (40% and 60%) at four weeks accompanied by increased airway smooth muscle deposition, which resolved at eight weeks. Severe hyperoxia increased baseline compliance, baseline resistance, and total elastin/surface area ratio without increasing airway hyperreactivity, and was accompanied by increased alveolar simplification, decreased airway tethering, and changes in elastin distribution at both time points. CONCLUSIONS: Mild to moderate hyperoxia causes changes in airway function and airway hyperreactivity with minimal parenchymal response. Severe hyperoxia drives its functional changes through alveolar simplification, airway tethering, and elastin redistribution. These differential responses can be leveraged to further develop hyperoxia mouse models.