title: Extracellular matrix proteins: a positive feedback loop in lung fibrosis?
abstract: Lung fibrosis is characterized by excessive deposition of extracellular matrix. This not only affects tissue architecture and function, but it also influences fibroblast behavior and thus disease progression. Here we describe the expression of elastin, type V collagen and tenascin C during the development of bleomycin-induced lung fibrosis. We further report in vitro experiments clarifying both the effect of myofibroblast differentiation on this expression and the effect of extracellular elastin on myofibroblast differentiation. Lung fibrosis was induced in female C57Bl/6 mice by bleomycin instillation. Animals were sacrificed at zero to five weeks after fibrosis induction. Collagen synthesized during the week prior to sacrifice was labeled with deuterium. After sacrifice, lung tissue was collected for determination of new collagen formation, microarray analysis, and histology. Human lung fibroblasts were grown on tissue culture plastic or BioFlex culture plates coated with type I collagen or elastin, and stimulated to undergo myofibroblast differentiation by 0-10 ng/ml transforming growth factor (TGF)β1. mRNA expression was analyzed by quantitative real-time PCR. New collagen formation during bleomycin-induced fibrosis was highly correlated to gene expression of elastin, type V collagen and tenascin C. At the protein level, elastin, type V collagen and tenascin C were highly expressed in fibrotic areas as seen in histological sections of the lung. Type V collagen and tenascin C were transiently increased. Human lung fibroblasts stimulated with TGFβ1 strongly increased gene expression of elastin, type V collagen and tenascin C. The extracellular presence of elastin increased gene expression of the myofibroblastic markers α smooth muscle actin and type I collagen. The extracellular matrix composition changes dramatically during the development of lung fibrosis. The increased levels of elastin, type V collagen and tenascin C are probably the result of increased expression by fibroblastic cells; reversely, elastin influences myofibroblast differentiation. This suggests a reciprocal interaction between fibroblasts and the extracellular matrix composition that could enhance the development of lung fibrosis.
authors.affiliation: Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute Amsterdam, The Netherlands; TNO Metabolic Health Research, Leiden, The Netherlands. Electronic address: me.blaauboer@acta.nl.
authors.forename: Marjolein E
authors.initials: ME
authors.lastname: Blaauboer
authors.affiliation: Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute Amsterdam, The Netherlands.
authors.forename: Fee R
authors.initials: FR
authors.lastname: Boeijen
authors.affiliation: Kinemed Inc., Emeryville, CA, USA.
authors.forename: Claire L
authors.initials: CL
authors.lastname: Emson
authors.affiliation: Kinemed Inc., Emeryville, CA, USA.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Turner
authors.affiliation: Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute Amsterdam, The Netherlands.
authors.forename: Behrouz
authors.initials: B
authors.lastname: Zandieh-Doulabi
authors.affiliation: TNO Metabolic Health Research, Leiden, The Netherlands.
authors.forename: Roeland
authors.initials: R
authors.lastname: Hanemaaijer
authors.affiliation: Department of Orthopaedics, VU Medical Center, MOVE Research Institute Amsterdam, The Netherlands.
authors.forename: Theo H
authors.initials: TH
authors.lastname: Smit
authors.affiliation: TNO Metabolic Health Research, Leiden, The Netherlands.
authors.forename: Reinout
authors.initials: R
authors.lastname: Stoop
authors.affiliation: Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute Amsterdam, The Netherlands.
authors.forename: Vincent
authors.initials: V
authors.lastname: Everts
mesh_terms: D000818:Animals; D001761:Bleomycin / Q000633:toxicity; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics*; D024062:Collagen Type V / Q000378:metabolism*; D004549:Elastin / Q000096:biosynthesis*; D005260:Female; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008168:Lung / Q000378:metabolism / Q000473:pathology; D051379:Mice; D058628:Myofibroblasts / Q000378:metabolism; D011658:Pulmonary Fibrosis / Q000139:chemically induced / Q000235:genetics* / Q000473:pathology; D019063:Tenascin / Q000096:biosynthesis*
chemical_list: D024062:Collagen Type V; D019063:Tenascin; D001761:Bleomycin; D004549:Elastin
keywords: Elastin; Extracellular matrix; Lung fibrosis; Myofibroblast differentiation; Tenascin C; Type V collagen