IL11 is linked to the pathogenesis of idiopathic pulmonary fibrosis (IPF), since IL11 induces myofibroblast differentiation and stimulates their excessive collagen deposition in the lung. The alveolar architecture is disrupted in IPF, yet the effect of IL11 on dysregulated alveolar repair associated with IPF remains to be elucidated. We hypothesized that epithelial-fibroblast communication associated with lung repair is disrupted by IL11. Thus, we studied whether IL11 affects the repair responses of alveolar lung epithelium using mouse lung organoids and precision cut lung slices (PCLS). Additionally, we assessed the anatomical distribution of IL11 and IL11 receptor in human control and IPF lungs using immunohistochemistry. IL11 protein was observed in human control lungs in airway epithelium, macrophages and in IPF lungs, in areas of AT2 cell hyperplasia. IL11R staining was predominantly present in smooth muscle and macrophages. In mouse organoid cocultures of epithelial cells with lung fibroblasts, IL11 decreased organoid number and reduced the fraction of pro-SPC expressing organoids, indicating dysfunctional regeneration initiated by epithelial progenitors. In mouse PCLS alveolar marker gene expression declined, whereas airway markers were increased. The response of primary human fibroblasts to IL11 on gene expression level was minimal, though bulk RNAsequencing revealed IL11 modulated a number of processes which may play a role in IPF, including unfolded protein response, glycolysis and Notch signaling. In conclusion, IL11 disrupts alveolar epithelial regeneration by inhibiting progenitor activation and suppressing the formation of mature alveolar epithelial cells. The contribution of dysregulated fibroblast epithelial communication to this process appears to be limited.

Background & aim: Recurring epithelial injury and aberrant repair are considered as a major driver of idiopathic pulmonary fibrosis (IPF) leading to chronic inflammation, fibroblast activation and ultimately to scarring and stiffening of the lung. As decline of lung function is the first reported symptom by IPF patients and occurs once fibrosis is firmly established, animal models are required to study early disease-driving mechanisms. Methods: We developed a novel and flexible mouse model of acute epithelial injury based on adeno-associated virus (AAV) variant 6.2 mediated expression of the human diphtheria toxin receptor (DTR). Following intratracheal administration of diphtheria toxin (DT), a cell-specific death of bronchial epithelial and alveolar epithelial type II cells can be observed. Results: Detailed characterization of the AAV-DTR/DT mouse model revealed increasing cell numbers in bronchoalveolar lavage (BAL; macrophages, neutrophils, and atypical cells) and elevation of apoptotic cells and infiltrated leukocytes in lung tissue, which were dependent of viral genome load and DT dose. Cytokine levels in BAL fluid showed different patterns dependent of viral genome load with IFNγ, TNFα, and IP-10 increasing and IL-5 and IL-6 decreasing, while lung function was not affected. Additionally, laser-capture microdissection-based proteomics of bronchial and alveolar epithelium showed upregulated immune and inflammatory response in all epithelial cell regions and extracellular matrix deposition in infiltrated alveoli, while proteins involved in pulmonary surfactant synthesis, alveolar fluid clearance and alveolar-capillary barrier were downregulated in the parenchyma. Conclusion: Our novel AAV-DTR/DT model resembles specific aspects of pulmonary diseases like IPF and acute respiratory distress syndrome.

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