Local IFNγ signaling contributes to the regenerative decline of aged alveolar progenitor cells.

The lungs are highly susceptible to chronic disease in advanced age, likely due to the uniquely compromised repair function of alveolar type II (AT2) cells, facultative progenitor cells that maintain the gas exchange surface. Using aging mouse models, single-cell sequencing, and ex vivo organoid assays, we found that homeostatic aged AT2 cells exhibited an Interferon γ (IFNγ) response associated with IFNγ+ CD8+ T cells in tertiary lymphoid structures (TLS). Aged AT2 cells exhibit impaired regeneration in organoid assays and lost markers of an IFNγ response outside the lung microenvironment, demonstrating that elevated local IFNγ influences the state of AT2 cells. Neutralization of IFNγ signaling and immunoproteasome knockout mice with attenuated IFNγ levels partially rescued aged AT2 cell regeneration. Our findings demonstrate that local IFN γ signaling in aging lungs actively represses alveolar regeneration, establishing chronic inflammatory signaling as a cause of age-related decline in the lung. Halting chronic inflammatory processes restored alveolar regeneration and may provide a means to improve lung health in old age.