title: Pathogenesis of osteoarthritis: chondrocyte replicative senescence or apoptosis?
abstract: BACKGROUND
  The aim of this study was to investigate by flow cytometry cellular viability and apoptosis of human chondrocytes isolated from osteoarthritic cartilage and to correlate replicative senescence with apoptosis of these cells.
  
  
  METHODS
  To understand the mechanisms underlying the process of cell death in cartilage destruction, we investigated by flow cytometry cellular viability (Cell viability calcein-AM assay) and apoptosis (Light scattering properties of chondrocytes, study of chondrocyte death using Annexin-V-FITC and propidium iodide double-labeling, caspase-3 activity determination) of human chondrocytes isolated from osteoarthritic and nonosteoarthritic cartilage. Senescent cells were characterized using the senescence-associated-beta-galactosidase marker (SA-beta-Gal marker) by staining with chromogenic substrate (X-Gal) to produce blue coloration of SA-beta-Gal-positive cells and microscopy analysis.
  
  
  RESULTS
  The results we obtained show that between 25 and 40% of chondrocytes were in apoptosis and all of them were SA-beta-Gal-positive.
  
  
  CONCLUSIONS
  These results demonstrate that the death of osteoarthritic chondrocytes is an apoptotic phenomenon which is preceded by an accelerated mechanism of replicative senescence.
authors.affiliation: Institutul National de Cercetare Dezvoltare pentru Stiinte Biologice, Bucuresti, Romania.
authors.forename: Luminita
authors.initials: L
authors.lastname: Takács-Buia
authors.forename: Catalin
authors.initials: C
authors.lastname: Iordachel
authors.forename: Nicolae
authors.initials: N
authors.lastname: Efimov
authors.forename: Maria
authors.initials: M
authors.lastname: Caloianu
authors.forename: Jean
authors.initials: J
authors.lastname: Montreuil
authors.forename: Daniela
authors.initials: D
authors.lastname: Bratosin
mesh_terms: D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology*; D015415:Biomarkers / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D048430:Cell Shape; D002470:Cell Survival; D016922:Cellular Senescence / Q000502:physiology*; D019902:Chondrocytes / Q000166:cytology* / Q000473:pathology / Q000502:physiology*; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D005452:Fluoresceins / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D006801:Humans; D007202:Indicators and Reagents / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000473:pathology / Q000503:physiopathology*; D011419:Propidium / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D017304:Annexin A5; D015415:Biomarkers; D005452:Fluoresceins; D005456:Fluorescent Dyes; D007202:Indicators and Reagents; C085925:calcein AM; D011419:Propidium; D001616:beta-Galactosidase; D053148:Caspase 3