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A2461 - Effect of IL-22 on Lung Progenitor Cells
Author Block: K. Hebert1, N. McLaughlin2, D. A. Pociask1; 1Department of Medicine, Tulane School of Medicine, New Orleans, LA, United States, 2Medicine, Section of Pulmonology, Tulane University Health Science Center, New Orleans, LA, United States.
RATIONALE: Severe influenza pneumonia can lead to acute respiratory distress syndrome (ARDS) and diffuse alveolar damage (DAD). While great effort is put into trying to reduce and prevent influenza infection, there is little understanding of how to reduce the extreme pathology seen during ARDS. It is generally understood that lung progenitor (Ngfr+, Krt5+ P63+) cells are vital for restoring lung epithelial architecture. Our lab is focused on the role of IL-10 family members during influenza infection. We are specifically focused on the cytokine IL-22, which has migratory and proliferative properties on epithelial cells. We have found that the IL-22 receptor (Il22ra1) is expressed on a number of epithelial cells after influenza infection, including Krt5+ Ngfr+ cells. Given our published findings that show IL-22KO mice have delayed epithelial repair in both the airways and lung parenchyma after infection, we hypothesize that IL-22 signals through the IL-22Ra1 on basal cells in the lung to help promote repair.
METHODS: For in vivo studies, IL-22KO mice were oropharyngeally instilled with influenza A/PR8 (100PFU) and Krt5 + pods were analyzed in the lungs at 10 and 21 days after infection. For in vitro experiments, we used a bronchosphere model. Lung epithelial cells were grown from epithelial specific cre recombinase strains (K18CreIL-22Rα1fl/fl, Sox2CreIL-22Rα1fl/fl), one global cre recombinase strain (EllaCreIL-22Rα1fl/fl), IL-22KO and C57Bl/6 mice. Lungs and trachea were harvested from pups of each strain. Single cell suspensions were made from digested specimen and plated at 200,000 cell/ml. After seven days bronchospheres were formed in all cultures. Media was refreshed on seventh day and treatment groups received human IL-22 for the following seven days. Groups from each strain were then combined, spun down, trypsinized and fixed in 0.5% PFA. These samples were stained for markers of interest and used for flow cytometry analysis. EdU incorporation assay was used to determine if IL-22 had a proliferative effect on progenitor cells. Histology and FACS analysis were also performed to understand differentiation of progenitor cells.
RESULTS: Our results demonstrate IL-22 has a role in repairing the lung by acting upon epithelial progenitor cells. Specifically, in vivo we found IL-22KO mice demonstrated reduced Krt5+ fields after pulmonary infection. Moreover, our in vitro bronchosphere model demonstrated that IL-22 treatment led to greater cell proliferation and larger spheres. This was not seen in mice lacking the IL-22 receptor.
CONCLUSIONS: IL-22 plays a role in proliferation of progenitor cells in the lung.