title: Bone morphogenetic protein-4 inhibitor gremlin is overexpressed in idiopathic pulmonary fibrosis.
abstract: Idiopathic pulmonary fibrosis (IPF), ie, usual interstitial pneumonia in histopathology, is a disease characterized by tissue destruction and active areas of fibroproliferation in the lung. Gremlin (Drm), a member of the cysteine knot family of bone morphogenetic protein (BMP) inhibitors, functions to antagonize BMP-4-mediated signals during lung development. We describe here consistent overexpression of gremlin in the lung interstitium of IPF patients. Quantitative real-time reverse transcriptase-polymerase chain reaction analyses revealed considerably higher levels of gremlin mRNA in lung biopsies from IPF patients, the highest level being 35-fold higher compared to controls. Lung fibroblasts isolated from IPF patients also expressed elevated levels of gremlin, which was associated with impaired responsiveness to endogenous and exogenous BMP-4. Transforming growth factor-beta-induced epithelial-to-mesenchymal transition of A549 lung epithelial cells in culture was also associated with induction of gremlin mRNA expression. In addition, A549 cells transfected to overexpress gremlin were more susceptible to transforming growth factor-beta-induced epithelial-to-mesenchymal transition. Gremlin-mediated inhibition of BMP-4 signaling pathways is likely to enhance the fibrotic response and reduce epithelial regeneration in the lung. The overexpression of this developmental gene in IPF may be a key event in the persistence of myofibroblasts in the lung interstitium and provides a potential target for therapeutic intervention.
authors.affiliation: Department of Virology, Haartman Institute, University of Helsinki and Helsinki University Central Hospital, Helsinki, Finland. katri.koli@helsinki.fi
authors.forename: Katri
authors.initials: K
authors.lastname: Koli
authors.forename: Marjukka
authors.initials: M
authors.lastname: Myllärniemi
authors.forename: Kirsi
authors.initials: K
authors.lastname: Vuorinen
authors.forename: Kaisa
authors.initials: K
authors.lastname: Salmenkivi
authors.forename: Merja J
authors.initials: MJ
authors.lastname: Ryynänen
authors.forename: Vuokko L
authors.initials: VL
authors.lastname: Kinnula
authors.forename: Jorma
authors.initials: J
authors.lastname: Keski-Oja
mesh_terms: D015152:Blotting, Northern; D015153:Blotting, Western; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis*; D011658:Pulmonary Fibrosis / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism
chemical_list: C525809:BMP4 protein, human; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; C486399:GREM1 protein, human; D036341:Intercellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta