Characterization of hyperoxia-induced senescent lung macrophages in neonatal mice.

Bronchopulmonary dysplasia (BPD), a chronic lung disease in premature infants, results from mechanical ventilation and hyperoxia amongst other factors. We and others have shown that neonatal hyperoxia, known to lead to a BPD-like phenotype in rodent models, causes lung cellular senescence. In our 3-day hyperoxia model, the majority of senescent cells were lung macrophages, and these peaked at postnatal day (pnd) 7. The features of these senescent macrophages are not characterized. Here, we reanalyzed scRNA-seq datasets (GSE207866) of senescent lung cells from mice exposed to hyperoxia as neonates at pnd7 (SD7), and characterized their gene express profiling and compared them with air control (AirD7) and hyperoxia-exposed group without isolation of senescent cells at pnd7 (O2D7). We first classified the cells into epithelial, endothelial, immune, and mesenchymal cells to extract immune cells. By employing the workflow to the immune clusters, mixed populations of macrophages, monocytes, and dendritic cells and pure population of macrophages, we finally identified seven clusters of macrophages. In SD7 group, 65.9% senescent cells were macrophages, and comprised M1 (64%) and alveolar (62.8%) macrophages. Clusters 0 and 1 were M1 and alveolar macrophages, which were composed of 49.2% of senescent macrophages. These two clusters highly expressed genes involved in innate immunity, inflammation, DNA repair response and phagocytosis. Metabolic switch from mitochondrial respiration to glycolysis and pentose phosphate pathway was observed in these two clusters. Conclusively, senescent macrophages are heterogenous with distinct tissue compartments and metabolic dysregulation.