Natural killer cell TGF- signaling regulates senolytic activity and vascular patterning in the postnatal lung

Background: Bronchopulmonary dysplasia (BPD) is a disease of neonatal lung development that is linked to impaired pulmonary vascularization, dysregulated transforming growth factor- (TGF-) signaling and the accumulation of senescent cells. Despite the established role for TGF- signaling in promoting vascular remodeling and suppressing the senolytic activity of natural killer (NK) cells, the contribution of NK cell TGF- signaling to postnatal lung patterning and the pathogenesis of BPD remains unclear. Methods: Mice bearing an NK cell-selective deletion of the type-II TGF- receptor (Tgfbr2NK-/-) were analyzed for vascular and alveolar structure, lung NK cell infiltration, senescence markers and lung function testing across neonatal and adult timepoints. Single-cell RNA sequencing of lung tissue from both neonatal mice and human infants with BPD was performed. The effect of enhanced NK cell activity in a hyperoxia-induced model of BPD was assessed in Tgfbr2NK-/- neonates, as well as pharmacologically, using the TGF- ligand trap/IL-15 superagonist, HCW9218. Results: Neonatal Tgfbr2NK-/- mice exhibited a baseline reduction in distal arteriolar density, impaired alveolarization, and sex-specific deficits in long-term lung function. Single-cell RNA sequencing identified the excessive clearance of senescent endothelial cells by TGF- insensitive NK cells in the lungs of Tgfbr2NK-/- neonates, which served as a contributor of the BPD-like phenotype observed in nave animals. Tgfbr2NK-/- mice were protected from impaired lung development in the hyperoxia model. Sequencing from lung tissue from infants with BPD confirmed excessive TGF- signaling and cytotoxic impairment in NK cells. Treatment with HCW9218 prevented senescent cell accumulation and rescued lung development in the hyperoxia mouse model. Conclusions: These findings identify TGF- as a tunable regulator of NK cell senolytic activity that is essential to normal postnatal lung development. Excessive NK cell TGF- signaling contributes to impaired lung development following exposure to neonatal hyperoxia and may serve as a viable therapeutic target for human BPD.