p53 maintains lineage fidelity during lung capillary injury-repair in neonatal hyperoxia.

Bronchopulmonary dysplasia (BPD), a prevalent and chronic lung disease affecting premature newborns, results in vascular rarefaction and alveolar simplification. Although the vasculature has been recognized as a main player in this disease, the recently found capillary heterogeneity and cellular dynamics of endothelial subpopulations in BPD remain unclear. Here, we showed that Cap2 cells were damaged during neonatal hyperoxic injury, leading to their replacement by Cap1 cells, which, in turn, significantly declined. Single-cell RNA-Seq identified the activation of numerous p53 target genes in endothelial cells (ECs), including Cdkn1a (p21). While global deletion of p53 resulted in worsened vasculature, EC-specific deletion of p53 reversed the vascular phenotype and improved alveolar simplification during hyperoxia. This recovery was associated with the emergence of a transitional EC state, enriched for oxidative stress response genes and growth factors. Notably, this transitional EC gene signature was conserved in an aberrant capillary population identified in human BPD with pulmonary hypertension, underscoring the biological and clinical relevance of our findings. These results reveal a key role for p53 in maintaining endothelial lineage fidelity during pulmonary capillary repair following hyperoxic injury and highlight the critical contribution of the endothelium to BPD pathogenesis.