IL-1 and TNFα Contribute to the Inflammatory Niche to Enhance Alveolar Regeneration

Abstract

Summary: Inflammatory responses are known to facilitate tissue recovery following injury. However, the precise mechanisms that enhance lung alveolar regeneration remain unclear. Here, using an organoid-based screening assay, we find that interleukin-1 (IL-1) and tumor necrosis factor α (TNFα) enhance the proliferation of AEC2s while maintaining their differentiation capacity. Furthermore, we find that expression of IL-1β and TNFα are induced in the AEC2 niche following influenza-induced injury in vivo, and lineage tracing analysis revealed that surviving AEC2s around the damaged area contribute to alveolar regeneration. Through genetic and pharmacological modulation of multiple components of the IL-1-nuclear factor κB (NF-κB) signaling axis, we show that cell-intrinsic as well as stromal mediated IL-1 signaling are essential for AEC2 mediated lung regeneration. Taken together, we propose that the IL-1/TNFα-NF-κB signaling axis functions as a component of an inflammation-associated niche to regulate proliferation of surviving AEC2s and promote lung regeneration. : The role of inflammatory responses in tissue repair and stem cell behavior is largely unexplored in the lung. Katsura et al. demonstrate that the cytokines interleukin-1 and tumor necrosis factor α, upregulated after influenza infection, enhance the proliferation of alveolar type 2 epithelial cells (AEC2s), endogenous lung stem cells. Moreover, these AEC2s generate AEC1s and contribute to alveolar regeneration. Keywords: lung regeneration, inflammatory niche, alveolar epithelium, influenza virus, alveolar organoids, alveolar damage, repair, IL-1, TNFα, NF-κB