title: TGF-β signalling and reactive oxygen species drive fibrosis and matrix remodelling in myxomatous mitral valves.
abstract: OBJECTIVE
  Myxomatous mitral valve disease (MMVD) is associated with leaflet thickening, fibrosis, matrix remodelling, and leaflet prolapse. Molecular mechanisms contributing to MMVD, however, remain poorly understood. We tested the hypothesis that increased transforming growth factor-β (TGF-β) signalling and reactive oxygen species (ROS) are major contributors to pro-fibrotic gene expression in human and mouse mitral valves.
  
  
  RESULTS
  Using qRT-PCR, we found that increased expression of TGF-β1 in mitral valves from humans with MMVD (n = 24) was associated with increased expression of connective tissue growth factor (CTGF) and matrix metalloproteinase 2 (MMP2). Increased levels of phospho-SMAD2/3 (western blotting) and expression of SMAD-specific E3 ubiquitin-protein ligases (SMURF) 1 and 2 (qRT-PCR) suggested that TGF-β1 signalling occurred through canonical signalling cascades. Oxidative stress (dihydroethidium staining) was increased in human MMVD tissue and associated with increases in NAD(P)H oxidase catalytic subunits (Nox) 2 and 4, occurring despite increases in superoxide dismutase 1 (SOD1). In mitral valves from SOD1-deficient mice, expression of CTGF, MMP2, Nox2, and Nox4 was significantly increased, suggesting that ROS can independently activate pro-fibrotic and matrix remodelling gene expression patterns. Furthermore, treatment of mouse mitral valve interstitial cells with cell permeable antioxidants attenuated TGF-β1-induced pro-fibrotic and matrix remodelling gene expression in vitro.
  
  
  CONCLUSIONS
  Activation of canonical TGF-β signalling is a major contributor to fibrosis and matrix remodelling in MMVD, and is amplified by increases in oxidative stress. Treatments aimed at reducing TGF-β activation and oxidative stress in early MMVD may slow progression of MMVD.
authors.affiliation: Division of Cardiovascular Surgery, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Hagler
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Hadley
authors.forename: Heyu
authors.initials: H
authors.lastname: Zhang
authors.forename: Kashish
authors.initials: K
authors.lastname: Mehra
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Roos
authors.forename: Hartzell V
authors.initials: HV
authors.lastname: Schaff
authors.forename: Rakesh M
authors.initials: RM
authors.lastname: Suri
authors.forename: Jordan D
authors.initials: JD
authors.lastname: Miller
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002478:Cells, Cultured; D055513:Connective Tissue Growth Factor / Q000235:genetics / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism*; D005355:Fibrosis; D005786:Gene Expression Regulation; D006349:Heart Valve Diseases / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008943:Mitral Valve / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D000074662:NADPH Oxidase 2; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D010766:Phosphorylation; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D000072105:Superoxide Dismutase-1; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
chemical_list: D000975:Antioxidants; C526317:CCN2 protein, human; C526318:CCN2 protein, mouse; D008562:Membrane Glycoproteins; D017382:Reactive Oxygen Species; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; C000606290:SOD1 protein, human; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D051900:Smad3 Protein; C508960:TGFB1 protein, human; C508961:Tgfb1 protein, mouse; D053773:Transforming Growth Factor beta1; D055513:Connective Tissue Growth Factor; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; C056558:CYBB protein, human; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human; C422943:Nox4 protein, mouse; C492381:Smurf1 protein, mouse; C533325:Smurf2 protein, mouse; D044767:Ubiquitin-Protein Ligases; C522361:MMP2 protein, human; D020778:Matrix Metalloproteinase 2; C522362:Mmp2 protein, mouse
keywords: Antioxidants; Cardiovascular surgery; Mitral valve; Regurgitation; Valves
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