title: Grainyhead-like 2 (GRHL2) distribution reveals novel pathophysiological differences between human idiopathic pulmonary fibrosis and mouse models of pulmonary fibrosis.
abstract: Chronic injury of alveolar lung epithelium leads to epithelial disintegrity in idiopathic pulmonary fibrosis (IPF). We had reported earlier that Grhl2, a transcriptional factor, maintains alveolar epithelial cell integrity by directly regulating components of adherens and tight junctions and thus hypothesized an important role of GRHL2 in pathogenesis of IPF. Comparison of GRHL2 distribution at different stages of human lung development showed its abundance in developing lung epithelium and in adult lung epithelium. However, GRHL2 is detected in normal human lung mesenchyme only at early fetal stage (week 9). Similar mesenchymal reexpression of GRHL2 was also observed in IPF. Immunofluorescence analysis in serial sections from three IPF patients revealed at least two subsets of alveolar epithelial cells (AEC), based on differential GRHL2 expression and the converse fluorescence intensities for epithelial vs. mesenchymal markers. Grhl2 was not detected in mesenchyme in intraperitoneal bleomycin-induced injury as well as in spontaneously occurring fibrosis in double-mutant HPS1 and HPS2 mice, whereas in contrast in a radiation-induced fibrosis model, with forced Forkhead box M1 (Foxm1) expression, an overlap of Grhl2 with a mesenchymal marker was observed in fibrotic regions. Grhl2's role in alveolar epithelial cell plasticity was confirmed by altered Grhl2 gene expression analysis in IPF and further validated by in vitro manipulation of its expression in alveolar epithelial cell lines. Our findings reveal important pathophysiological differences between human IPF and specific mouse models of fibrosis and support a crucial role of GRHL2 in epithelial activation in lung fibrosis and perhaps also in epithelial plasticity.
authors.affiliation: Saban Research Institute, Children's Hospital Los Angeles, 4650 Sunset Blvd., MS35, Los Angeles, CA 90027. saaket.varma@gmail.com.
authors.forename: Saaket
authors.initials: S
authors.lastname: Varma
authors.forename: Poornima
authors.initials: P
authors.lastname: Mahavadi
authors.forename: Satish
authors.initials: S
authors.lastname: Sasikumar
authors.forename: Leah
authors.initials: L
authors.lastname: Cushing
authors.forename: Tessa
authors.initials: T
authors.lastname: Hyland
authors.forename: Ann E
authors.initials: AE
authors.lastname: Rosser
authors.forename: Daniela
authors.initials: D
authors.lastname: Riccardi
authors.forename: Jining
authors.initials: J
authors.lastname: Lu
authors.forename: Tanya V
authors.initials: TV
authors.lastname: Kalin
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Kalinichenko
authors.forename: Andreas
authors.initials: A
authors.lastname: Guenther
authors.forename: Maria I
authors.initials: MI
authors.lastname: Ramirez
authors.forename: Annie
authors.initials: A
authors.lastname: Pardo
authors.forename: Moisés
authors.initials: M
authors.lastname: Selman
authors.forename: David
authors.initials: D
authors.lastname: Warburton
mesh_terms: D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D005333:Fetus / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D006801:Humans; D054990:Idiopathic Pulmonary Fibrosis / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D008648:Mesoderm / Q000378:metabolism / Q000502:physiology; D051379:Mice; D008817:Mice, Mutant Strains; D008875:Middle Aged; D011247:Pregnancy; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D020545:Respiratory Mucosa / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D013045:Species Specificity; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; C470830:GRHL2 protein, human; D014157:Transcription Factors; C552738:grainy head-like 2 protein, mouse
keywords: GRHL2; cell flattening; epithelial integrity; epithelial plasticity; idiopathic pulmonary fibrosis