title: Fibroblasts in Hypoxic Conditions Mimic Laryngotracheal Stenosis.
abstract: Objective To elucidate the role of hypoxia and inflammatory pathways in the pathogenesis of iatrogenic laryngotracheal stenosis (iLTS). Study Design (1) Examination of mucosal surface gene expression in human iLTS. (2) In vitro comparison of normal and scar laryngotracheal fibroblasts under normoxic and hypoxic conditions. Setting Tertiary care hospital in a research university (2012-2016). Subjects and Methods Brush biopsies were obtained from normal laryngotracheal tissue and scar in iLTS patients; gene expression was compared. Fibroblasts were isolated from normal and scarred trachea and grown in vitro in either a 1% O2or normoxic environment. Cell growth and gene and protein expression were compared. Statistical analysis utilized a multilevel mixed effects model. Results Expression of IL-6 (fold change = 2.8, P < .01), myofibroblast marker αSMA (fold change = 3.0, P = .01), and MMP13 (fold change = 5.4, P = .02) was significantly increased in scar biopsy samples as compared to normal. Under hypoxic conditions in vitro, normal laryngotracheal fibroblasts proliferated significantly faster (n = 8, P < .01 each day). Expression of IL-6 (n = 8, fold change = 2.6, P < .01) increased significantly after 12 hours under hypoxia. Expression of αSMA (n = 8, fold change= 2.0, P = .03), COL1 (n = 8, fold change = 1.1, P = .03), and MMP13 (n = 8, fold change = 1.6, P = .01) increased significantly after 48 hours under hypoxia. Scar fibroblasts also proliferated significantly faster under hypoxic conditions but did not display the same expression profile. Conclusion Human iLTS scar has a myofibroblast phenotype. Under hypoxic conditions in vitro, normal laryngotracheal fibroblasts can transdifferentiate into a similar phenotype. These changes may be mediated by IL-6, a fibrosis-related cytokine.
authors.affiliation: 1 Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Linda X
authors.initials: LX
authors.lastname: Yin
authors.affiliation: 2 Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins, Baltimore, Maryland, USA.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Motz
authors.affiliation: 3 Department of Otolaryngology-Head and Neck Surgery, University of Ottawa, Ontario, Canada.
authors.forename: Idris
authors.initials: I
authors.lastname: Samad
authors.affiliation: 1 Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Madhavi
authors.initials: M
authors.lastname: Duvvuri
authors.affiliation: 2 Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins, Baltimore, Maryland, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Murphy
authors.affiliation: 2 Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins, Baltimore, Maryland, USA.
authors.forename: Dacheng
authors.initials: D
authors.lastname: Ding
authors.affiliation: 2 Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins, Baltimore, Maryland, USA.
authors.forename: Alexander T
authors.initials: AT
authors.lastname: Hillel
mesh_terms: D000199:Actins / Q000235:genetics; D001706:Biopsy / Q000379:methods; D049109:Cell Proliferation / Q000235:genetics; D002478:Cells, Cultured; D002921:Cicatrix / Q000235:genetics / Q000473:pathology; D015331:Cohort Studies; D003937:Diagnosis, Differential; D005260:Female; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology*; D005786:Gene Expression Regulation; D006801:Humans; D000860:Hypoxia / Q000150:complications*; D007049:Iatrogenic Disease; D015850:Interleukin-6 / Q000235:genetics; D007829:Laryngostenosis / Q000378:metabolism / Q000473:pathology*; D008297:Male; D053509:Matrix Metalloproteinase 13 / Q000235:genetics; D012016:Reference Values; D012189:Retrospective Studies; D062606:Tertiary Care Centers; D014135:Tracheal Stenosis / Q000378:metabolism / Q000473:pathology*
chemical_list: C541116:ACTA2 protein, human; D000199:Actins; D015850:Interleukin-6; D053509:Matrix Metalloproteinase 13
keywords: fibrosis; hypoxia; iatrogenic; laryngotracheal stenosis; scar; subglottic stenosis