Interleukin-11 causes alveolar type 2 cell dysfunction and prevents alveolar regeneration [scRNA-Seq]

Following lung injury, alveolar regeneration is characterized by the transformation of alveolar type 2 (AT2) cells, via a transitional KRT8+ state, into alveolar type 1 (AT1) cells. In lung disease, dysfunctional intermediate cells accumulate, AT2 and AT1 cells are diminished and fibrosis occurs. Using single cell RNA sequencing (scRNA-seq) datasets of human interstitial lung disease, we found that Interleukin-11 (IL11) is specifically expressed in aberrant KRT8 expressing KRT5-/KRT17+ epithelial cells and basaloid cells. Stimulation of AT2 cells and distal airway epithelial cells with IL11 or TGFβ1 caused epithelial-to-mesenchymal transition (EMT), induced extracellular matrix (ECM) production, increased KRT8 expression and stalled AT2-to-AT1 differentiation, with TGFβ1 effects being partially IL11 dependent. In bleomycin injured mouse lung, IL11 was increased in AT2-derived Krt8+ transitional cells and deletion of Il11ra1 in AT2 lineage cells prevented the accumulation of Krt8+ transitional cells, enhanced AT1 differentiation and promoted alveolar regeneration, which was replicated in therapeutic studies using anti-IL11 antibodies. scRNA-seq analysis of lung epithelial cells from mice with deletion of Il11ra1 in AT2 lineage cells further identified the importance of IL11 signaling for the potentiation and polarization of a disease-causing, ECM producing KRT8+ transitional cells that contributes to pathological lung remodeling. Overall, our data show that IL11 maintains damaged AT2 cells in a transitional state, impairs reparative AT1 differentiation and impairs endogenous alveolar regeneration to cause fibrotic lung disease.