title: Cartilage rings contribute to the proper embryonic tracheal epithelial differentiation, metabolism, and expression of inflammatory genes.
abstract: The signaling cross talk between the tracheal mesenchyme and epithelium has not been researched extensively, leaving a substantial gap of knowledge in the mechanisms dictating embryonic development of the proximal airways by the adjacent mesenchyme. Recently, we reported that embryos lacking mesenchymal expression of Sox9 did not develop tracheal cartilage rings and showed aberrant differentiation of the tracheal epithelium. Here, we propose that tracheal cartilage provides local inductive signals responsible for the proper differentiation, metabolism, and inflammatory status regulation of the tracheal epithelium. The tracheal epithelium of mesenchyme-specific Sox9Δ/Δmutant embryos showed altered mRNA expression of various epithelial markers such as Pb1fa1, surfactant protein B (Sftpb), secretoglobulin, family 1A, member 1 (Scgb1a1), and trefoil factor 1 (Tff1). In vitro tracheal epithelial cell cultures confirmed that tracheal chondrocytes secrete factors that inhibit club cell differentiation. Whole gene expression profiling and ingenuity pathway analysis showed that the tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), and transforming growth factor-β (TGF-β) signaling pathways were significantly altered in the Sox9 mutant trachea. TNF-α and IFN-γ interfered with the differentiation of tracheal epithelial progenitor cells into mature epithelial cell types in vitro. Mesenchymal knockout of Tgf-β1 in vivo resulted in altered differentiation of the tracheal epithelium. Finally, mitochondrial enzymes involved in fat and glycogen metabolism, cytochrome c oxidase subunit VIIIb (Cox8b) and cytochrome c oxidase subunit VIIa polypeptide 1 (Cox7a1), were strongly upregulated in the Sox9 mutant trachea, resulting in increases in the number and size of glycogen storage vacuoles. Our results support a role for tracheal cartilage in modulation of the differentiation and metabolism and the expression of inflammatory-related genes in the tracheal epithelium by feeding into the TNF-α, IFN-γ, and TGF-β signaling pathways.
authors.affiliation: Developmental Biology and Regenerative Medicine Program, The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, California; gturcatel@chla.usc.edu.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Turcatel
authors.affiliation: Developmental Biology and Regenerative Medicine Program, The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, California.
authors.forename: Katelyn
authors.initials: K
authors.lastname: Millette
authors.affiliation: Keck School of Medicine, University of Southern California, Department of Obstetrics and Gynecology, Maternal-Fetal Medicine Division, Los Angeles, California.
authors.forename: Matthew
authors.initials: M
authors.lastname: Thornton
authors.affiliation: Keck Graduate Institute, Claremont, California; and.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Leguizamon
authors.affiliation: Keck School of Medicine, University of Southern California, Department of Obstetrics and Gynecology, Maternal-Fetal Medicine Division, Los Angeles, California.
authors.forename: Brendan
authors.initials: B
authors.lastname: Grubbs
authors.affiliation: Developmental Biology and Regenerative Medicine Program, The Saban Research Institute, Children's Hospital Los Angeles, and Keck School of Medicine, Ostrow School of Dentistry, University of Southern California, Los Angeles, California.
authors.forename: Wei
authors.initials: W
authors.lastname: Shi
authors.affiliation: Developmental Biology and Regenerative Medicine Program, The Saban Research Institute, Children's Hospital Los Angeles, and Keck School of Medicine, Ostrow School of Dentistry, University of Southern California, Los Angeles, California.
authors.forename: David
authors.initials: D
authors.lastname: Warburton
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002356:Cartilage / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004622:Embryo, Mammalian / Q000187:drug effects / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism*; D004848:Epithelium / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D006003:Glycogen / Q000378:metabolism; D007249:Inflammation / Q000235:genetics*; D007371:Interferon-gamma / Q000378:metabolism; D008297:Male; D008648:Mesoderm / Q000187:drug effects / Q000196:embryology; D018345:Mice, Knockout; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010084:Oxidation-Reduction / Q000187:drug effects; D055758:SOX9 Transcription Factor / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014132:Trachea / Q000166:cytology* / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D015415:Biomarkers; D017077:Culture Media, Conditioned; D055758:SOX9 Transcription Factor; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D006003:Glycogen
keywords: Sox9; Tgf-β; basal cell; club cells; embryonic trachea