Abstract Rationale Oxygen supplementation of preterm infants frequently leads to Bronchopulmonary Dysplasia (BPD), a neonatal chronic lung disease (CLD) with lung structural sequelae, resembling characteristics of age-related CLD. Aging is a complex process, with stem cell exhaustion and genomic instability representing key hallmarks. Prior studies showed that oxidative stress (OS) causes a loss of alveolar epithelial type 2 cell (AT2) in neonatal mice. Since effective treatments to prevent or cure BPD are lacking, we now investigated the mechanisms by which OS induces lung growth arrest and contributes to the pathogenesis of BPD across life span, ultimately driving the susceptibility to CLD. Methods (i) Experimental BPD: Neonatal mice were exposed to hyperoxia (85% O2) or normoxia (21% O2) for 14 days after birth. Lungs were harvested for proteomic profiling at postnatal days (P) 14, 28, 70 and 18 months. (ii) DNA damage response (DDR), cellular stress response and lung structure were studied. (iii) We employed a transgenic mouse line with a specific inducible ablation of the excision repair cross-complementation group 1 (Ercc1; AT2-Ercc1KO), central in DNA repair, in AT2 cells at P3. Lungs were studied at P21 and 9 months of age. Results (i) Proteomic profiling identified age-specific proteomic patterns: At the acute phase (P14), mitochondrial and genomic pathways were significantly altered, followed by downregulation of genes in DNA repair pathways and upregulated ECM components during recovery (P28 and 70). (ii) These temporo-specific changes (oxidative stress, DDR, matrix remodeling) across life span were confirmed with immunostaining or structural analysis. The findings indicate that early OS caused AT2 depletion, senescence, cell-specific DDR, and arrest of alveolarization with an emphysematous structure later in life. Similarly, we confirmed DDR in lungs of infants with BPD, with a senescence expression profile in AT2. (iii) Deletion of Ercc1 in AT2 increased both DDR (γH2AX, pATM) and senescence (CDKN1A) in AT2 at P21. At 9 months, the AT2-Ercc1KO exhibited AT2 depletion with alveolar simplification. Additionally, we identified a non-cell autonomous function of AT2 with DDR on lung vasculature with vascular remodeling. Conclusion Here, we identified a temporal cascade of pathological events in neonatal lungs exposed to OS, inducing genomic instability in AT2 and thereby impairing alveolar development and promoting emphysema-like remodeling later in life. These findings highlight the critical role of genomic stability in AT2 cells for maintaining lung homeostasis across the lifespan and suggest its potential as a therapeutic target to prevent CLD in patients with BPD. This abstract is funded by: DFG
Huang et al. (Fri,) studied this question.