Inhaled vitamin A mitigates hyperoxia-induced acute and chronic lung damage in a neonatal rat model of bronchopulmonary dysplasia

Rationale Prevention of bronchopulmonary dysplasia (BPD) remains a critical unmet need. Objectives We continued evaluating aerosolized vitamin A in a neonatal rat hyperoxia-injury model of BPD, testing whether lung-targeted inhalation yields superior outcomes compared to enteral or intramuscular (IM) delivery. Methods Rat pups were exposed to continuous 95% hyperoxia for seven days to induce lung damage. Vitamin A was administered from post-natal day (PD) 1-7 by inhalation, enteral or IM dosing. Persisting effectiveness of inhaled vitamin A was examined at PD 21, dwelling in normoxia after all interventions were discontinued at PD 7. Measurements and Main Results Comprehensive analyses include alveolar morphometrics, in vivo pulmonary function testing, assessment of hepatic vitamin A level, and quantitating gene and protein expression of relevant biomarkers of lung maturation, inflammation and damage/repair, employing singlex and multiplexed assays and whole-genome gene expression. Conclusions Inhaled vitamin A suppressed hyperoxia-induced lung damage, with key hallmarks of BPD, including lung morphometrics and biomarkers associated with lung damage and inflammation, being effectively indistinguishable from healthy controls at both PD 7 and 21, Natural reparative processes were enhanced, with normal alveolarization and pulmonary function at PD 21. Despite raising hepatic vitamin A levels, enteral dosing was ineffective in restoring alveolar morphology at PD 7. Consistent with previous reporting, IM dosing yielded modest effect at PD 7 but with little evidence of benefit to pulmonary function at PD 21. Observation of dose-dependent effects with aerosolized vitamin A strengthens the evidence of the benefits of lung-targeted delivery, supporting further development of inhaled vitamin A as a BPD preventive strategy.