Pathogenesis of osteoarthritis: chondrocyte replicative senescence or apoptosis?
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.
Takács-Buia
Luminita
L
Institutul National de Cercetare Dezvoltare pentru Stiinte Biologice, Bucuresti, Romania.
Iordachel
Catalin
C
Efimov
Nicolae
N
Caloianu
Maria
M
Montreuil
Jean
J
Bratosin
Daniela
D
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
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