title: p16INK4a and its regulator miR-24 link senescence and chondrocyte terminal differentiation-associated matrix remodeling in osteoarthritis.
abstract: BACKGROUND
  Recent evidence suggests that tissue accumulation of senescent p16INK4a-positive cells during the life span would be deleterious for tissue functions and could be the consequence of inherent age-associated disorders. Osteoarthritis (OA) is characterized by the accumulation of chondrocytes expressing p16INK4a and markers of the senescence-associated secretory phenotype (SASP), including the matrix remodeling metalloproteases MMP1/MMP13 and pro-inflammatory cytokines interleukin-8 (IL-8) and IL-6. Here, we evaluated the role of p16INK4a in the OA-induced SASP and its regulation by microRNAs (miRs).
  
  
  METHODS
  We used IL-1-beta-treated primary OA chondrocytes cultured in three-dimensional setting or mesenchymal stem cells differentiated into chondrocyte to follow p16INK4a expression. By transient transfection experiments and the use of knockout mice, we validate p16INK4a function in chondrocytes and its regulation by one miR identified by means of a genome-wide miR-array analysis.
  
  
  RESULTS
  p16INK4a is induced upon IL-1-beta treatment and also during in vitro chondrogenesis. In the mouse model, Ink4a locus favors in vivo the proportion of terminally differentiated chondrocytes. When overexpressed in chondrocytes, p16INK4a is sufficient to induce the production of the two matrix remodeling enzymes, MMP1 and MMP13, thus linking senescence with OA pathogenesis and bone development. We identified miR-24 as a negative regulator of p16INK4a. Accordingly, p16INK4a expression increased while miR-24 level was repressed upon IL-1-beta addition, in OA cartilage and during in vitro terminal chondrogenesis.
  
  
  CONCLUSIONS
  We disclosed herein a new role of the senescence marker p16INK4a and its regulation by miR-24 during OA and terminal chondrogenesis.
authors.forename: Didier
authors.initials: D
authors.lastname: Philipot
authors.forename: David
authors.initials: D
authors.lastname: Guérit
authors.forename: Daniela
authors.initials: D
authors.lastname: Platano
authors.forename: Paul
authors.initials: P
authors.lastname: Chuchana
authors.forename: Eleonora
authors.initials: E
authors.lastname: Olivotto
authors.forename: Francisco
authors.initials: F
authors.lastname: Espinoza
authors.forename: Anne
authors.initials: A
authors.lastname: Dorandeu
authors.forename: Yves-Marie
authors.initials: YM
authors.lastname: Pers
authors.forename: Jacques
authors.initials: J
authors.lastname: Piette
authors.forename: Rosa Maria
authors.initials: RM
authors.lastname: Borzi
authors.forename: Christian
authors.initials: C
authors.lastname: Jorgensen
authors.forename: Danièle
authors.initials: D
authors.lastname: Noel
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Brondello
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000378:metabolism / Q000473:pathology; D015153:Blotting, Western; D002454:Cell Differentiation / Q000502:physiology; D016922:Cellular Senescence / Q000502:physiology; D019902:Chondrocytes / Q000378:metabolism / Q000473:pathology*; D020219:Chondrogenesis / Q000502:physiology*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007150:Immunohistochemistry; D020781:Matrix Metalloproteinase 1 / Q000378:metabolism; D053509:Matrix Metalloproteinase 13 / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology; D051379:Mice; D018345:Mice, Knockout; D035683:MicroRNAs / Q000378:metabolism*; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D010003:Osteoarthritis / Q000378:metabolism* / Q000473:pathology; D060888:Real-Time Polymerase Chain Reaction; D014162:Transfection
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; C543845:MIRN24 microRNA, human; D035683:MicroRNAs; C507079:MMP13 protein, human; D053509:Matrix Metalloproteinase 13; C522360:MMP1 protein, human; D020781:Matrix Metalloproteinase 1