title: Senescent mesenchymal cells accumulate in human fibrosis by a telomere-independent mechanism and ameliorate fibrosis through matrix metalloproteinases.
abstract: Fibrosis can occur in many organs, where it is a debilitating and preneoplastic condition. The senescence of activated fibroblasts has been proposed to ameliorate fibrosis via the innate immune system but its role in humans has not been investigated. The availability of oral submucous fibrosis (OSMF) biopsies at different stages of disease progression allowed us to test the hypothesis that senescent fibroblasts accumulate with the progression of human fibrosis in vivo, and also to examine the mechanism of senescence. We tested the hypothesis that senescent cells may ameliorate fibrosis by increasing the secretion of matrix metalloproteinases (MMPs). We have used a combination of in situ immunodetection techniques, drug treatments, fluorescence-activated cell sorting and enzyme-linked absorbance assays on tissue samples and fibroblast cultures. We report a novel panning technique, based on fibronectin adhesion rates, to enrich and deplete senescent cells from fibroblast populations. Senescent fibroblasts, as determined by the presence of senescence-associated heterochromatic foci, accumulated with OSMF progression (R(2) = 0.98) and possessed a reduced replicative lifespan in vitro. Unlike wounds, however, OSMF fibroblasts were quiescent in vivo and consistent with this observation, possessed functional telomeres of normal length. Senescence was associated in vivo and in vitro with oxidative damage, DNA damage foci and p16(INK4A) accumulation and required the production of reactive oxygen species (ROS), perhaps from damaged mitochondria, but not the continuous presence of the disease stimulus (areca nut and tobacco), the tissue environment or other cell types. Depletion of OSMF fibroblasts of senescent cells showed that these cells accounted for 25-83 times more MMP-1 and -2 than their pre-senescent counterparts. The results show that the accumulation of senescent fibroblasts in human fibrosis occurs by a telomere-independent mechanism involving ROS and may locally ameliorate the condition by the increased expression of MMPs prior to clearance by the immune system.
authors.affiliation: Centre for Clinical and Diagnostic Oral Sciences, Institute of Dentistry, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Turner Street, London, UK.
authors.forename: Gayani Nadika
authors.initials: GN
authors.lastname: Pitiyage
authors.forename: Predrag
authors.initials: P
authors.lastname: Slijepcevic
authors.forename: Aliya
authors.initials: A
authors.lastname: Gabrani
authors.forename: Yaghoub Gozaly
authors.initials: YG
authors.lastname: Chianea
authors.forename: Kue Peng
authors.initials: KP
authors.lastname: Lim
authors.forename: Stephen Stewart
authors.initials: SS
authors.lastname: Prime
authors.forename: Wanninayake Mudiyanselage
authors.initials: WM
authors.lastname: Tilakaratne
authors.forename: Farida
authors.initials: F
authors.lastname: Fortune
authors.forename: Eric Kenneth
authors.initials: EK
authors.lastname: Parkinson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D049109:Cell Proliferation; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000235:genetics / Q000502:physiology; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D004249:DNA Damage; D018450:Disease Progression; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology; D006801:Humans; D020781:Matrix Metalloproteinase 1 / Q000378:metabolism; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020782:Matrix Metalloproteinases / Q000502:physiology*; D059630:Mesenchymal Stem Cells / Q000378:metabolism / Q000473:pathology* / Q000502:physiology; D008875:Middle Aged; D008928:Mitochondria / Q000502:physiology; D009914:Oral Submucous Fibrosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D018384:Oxidative Stress / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D016615:Telomere / Q000502:physiology; D055815:Young Adult
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; D017382:Reactive Oxygen Species; D020782:Matrix Metalloproteinases; D020778:Matrix Metalloproteinase 2; D020781:Matrix Metalloproteinase 1