title: Gene expression in whole lung and pulmonary macrophages reflects the dynamic pathology associated with airway surface dehydration.
abstract: BACKGROUND
  Defects in airway mucosal defense, including decreased mucus clearance, contribute to the pathogenesis of human chronic obstructive pulmonary diseases. Scnn1b-Tg mice, which exhibit chronic airway surface dehydration from birth, can be used as a model to study the pathogenesis of muco-obstructive lung disease across developmental stages. To identify molecular signatures associated with obstructive lung disease in this model, gene expression analyses were performed on whole lung and purified lung macrophages collected from Scnn1b-Tg and wild-type (WT) littermates at four pathologically relevant time points. Macrophage gene expression at 6 weeks was evaluated in mice from a germ-free environment to understand the contribution of microbes to disease development.
  
  
  RESULTS
  Development- and disease-specific shifts in gene expression related to Scnn1b over-expression were revealed in longitudinal analyses. While the total number of transgene-related differentially expressed genes producing robust signals was relatively small in whole lung (n = 84), Gene Set Enrichment Analysis (GSEA) revealed significantly perturbed biological pathways and interactions between normal lung development and disease initiation/progression. Purified lung macrophages from Scnn1b-Tg mice exhibited numerous robust and dynamic gene expression changes. The expression levels of Classically-activated (M1) macrophage signatures were significantly altered at post-natal day (PND) 3 when Scnn1b-Tg mice lung exhibit spontaneous bacterial infections, while alternatively-activated (M2) macrophage signatures were more prominent by PND 42, producing a mixed M1-M2 activation profile. While differentially-regulated, inflammation-related genes were consistently identified in both tissues in Scnn1b-Tg mice, there was little overlap between tissues or across time, highlighting time- and tissue-specific responses. Macrophages purified from adult germ-free Scnn1b-Tg mice exhibited signatures remarkably similar to non-germ-free counterparts, indicating that the late-phase macrophage activation profile was not microbe-dependent.
  
  
  CONCLUSIONS
  Whole lung and pulmonary macrophages respond independently and dynamically to local stresses associated with airway mucus stasis. Disease-specific responses interact with normal developmental processes, influencing the final state of disease in this model. The robust signatures observed in Scnn1b-Tg lung macrophages highlight their critical role in disease pathogenesis. These studies emphasize the importance of region-, cell-type-, and time-dependent analyses to fully dissect the natural history of disease and the consequences of disease on normal lung development.
authors.affiliation: Marsico Lung Institute/University of North Carolina Cystic Fibrosis Center, School of Medicine, University of North Carolina at Chapel Hill, 7011 Thurston Bowles Building, Chapel Hill, NC 27599-7248, USA. yogesh_saini@med.unc.edu.
authors.forename: Yogesh
authors.initials: Y
authors.lastname: Saini
authors.forename: Hong
authors.initials: H
authors.lastname: Dang
authors.forename: Alessandra
authors.initials: A
authors.lastname: Livraghi-Butrico
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Kelly
authors.forename: Lisa C
authors.initials: LC
authors.lastname: Jones
authors.forename: Wanda K
authors.initials: WK
authors.lastname: O'Neal
authors.forename: Richard C
authors.initials: RC
authors.lastname: Boucher
mesh_terms: D000818:Animals; D003681:Dehydration; D015536:Down-Regulation; D053503:Epithelial Sodium Channels / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D006801:Humans; D007249:Inflammation / Q000235:genetics; D008137:Longitudinal Studies; D008168:Lung / Q000378:metabolism*; D008262:Macrophage Activation; D016676:Macrophages, Alveolar / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009093:Mucus / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D025341:Principal Component Analysis; D015854:Up-Regulation
chemical_list: D053503:Epithelial Sodium Channels; C507048:SCNN1B protein, human