title: Endogenous Semaphorin-7A Impedes Human Lung Fibroblast Differentiation.
abstract: Semaphorin-7A is a glycosylphosphatidylinositol-anchored protein, initially characterized as an axon guidance protein. Semaphorin-7A also contributes to immune cell regulation and may be an essential pro-fibrotic factor when expressed by non-fibroblast cell types (exogenous). In mouse models, semaphorin-7A was shown to be important for TGF-ß1-induced pulmonary fibrosis characterized by myofibroblast accumulation and extracellular matrix deposition, but the cell-specific role of semaphorin-7A was not examined in fibroblasts. The purpose of this study is to determine semaphorin-7A expression by fibroblasts and to investigate the function of endogenously expressed semaphorin-7A in primary human lung fibroblasts (HLF). Herein, we show that non-fibrotic HLF expressed high levels of cell surface semaphorin-7A with little dependence on the percentage of serum or recombinant TGF-ß1. Semaphorin-7A siRNA strongly decreased semaphorin-7A mRNA expression and reduced cell surface semaphorin-7A. Reduction of semaphorin-7A induced increased proliferation and migration of non-fibrotic HLF. Also, independent of the presence of TGF-ß1, the decline of semaphorin-7A by siRNA was associated with increased α-smooth muscle actin production and gene expression of periostin, fibronectin, laminin, and serum response factor (SRF), indicating differentiation into a myofibroblast. Conversely, overexpression of semaphorin-7A in the NIH3T3 fibroblast cell line reduced the production of pro-fibrotic markers. The inverse association between semaphorin-7A and pro-fibrotic fibroblast markers was further analyzed using HLF from idiopathic pulmonary fibrosis (IPF) (n = 6) and non-fibrotic (n = 7) lungs. Using these 13 fibroblast lines, we observed that semaphorin-7A and periostin expression were inversely correlated. In conclusion, our study indicates that endogenous semaphorin-7A in HLF plays a role in maintaining fibroblast homeostasis by preventing up-regulation of pro-fibrotic genes. Therefore, endogenous and exogenous semaphorin-7A may have opposite effects on the fibroblast phenotype.
authors.affiliation: Department of Medicine, Division of Allergy, Pulmonary and Critical Care Medicine, the University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Stephane
authors.initials: S
authors.lastname: Esnault
authors.affiliation: Department of Medicine, Division of Allergy, Pulmonary and Critical Care Medicine, the University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Torr
authors.affiliation: Department of Medicine, Division of Allergy, Pulmonary and Critical Care Medicine, the University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Ksenija
authors.initials: K
authors.lastname: Bernau
authors.affiliation: Department of Biomolecular Chemistry, the University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Mats W
authors.initials: MW
authors.lastname: Johansson
authors.affiliation: Department of Medicine, Division of Allergy, Pulmonary and Critical Care Medicine, the University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Kelly
authors.affiliation: Department of Medicine, Division of Allergy, Pulmonary and Critical Care Medicine, the University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Nathan
authors.initials: N
authors.lastname: Sandbo
authors.affiliation: Department of Medicine, Division of Allergy, Pulmonary and Critical Care Medicine, the University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, United States of America.
authors.forename: Nizar N
authors.initials: NN
authors.lastname: Jarjour
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D005109:Extracellular Matrix / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism; D005353:Fibronectins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D054990:Idiopathic Pulmonary Fibrosis / Q000378:metabolism / Q000473:pathology*; D008168:Lung / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D011658:Pulmonary Fibrosis / Q000378:metabolism / Q000473:pathology*; D039961:Semaphorins / Q000235:genetics / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism*
chemical_list: D005353:Fibronectins; D039961:Semaphorins; D053773:Transforming Growth Factor beta1