High oxygen exposure's impact on newborn mice: Temporal changes observed via micro-computed tomography.

Introduction: Bronchopulmonary dysplasia (BPD) impacts life expectancy and long-term quality of life. Currently, BPD mouse models exposed to high oxygen are frequently used, but to reevaluate their relevance to human BPD, we attempted an assessment using micro-computed tomography (µCT).

Methods: Newborn wildtype male mice underwent either 21% or 95% oxygen exposure for 4 days, followed until 8 wk. Weekly µCT scans and lung histological evaluations were performed independently.

Results: Neonatal hyperoxia for 4 days hindered lung development, causing alveolar expansion and simplification. Histologically, during the first postnatal week, the exposed group showed a longer mean linear intercept, enlarged alveolar area, and a decrease in alveolar number, diminishing by week 4. Weekly µCT scans supported these findings, revealing initially lower lung density in newborn mice, increasing with age. However, the high-oxygen group displayed higher lung density initially. This difference diminished over time, with no significant contrast to controls at 3 wk. Although no significant difference in total lung volume was observed at week 1, the high-oxygen group exhibited a decrease by week 2, persisting until 8 wk.

Conclusion: This study highlights µCT-detected changes in mice exposed to high oxygen. BPD mouse models might follow a different recovery trajectory than humans, suggesting the need for further optimization.