Evidence of oncotic cell death and DNA fragmentation in human hypertrophic chondrocytes in chondro-osteophyte

Objective: To investigate the population and morphology of in situ terminal deoxynucleotidyle transferase (TdT)-mediated dUTP nick end-labeling (TUNEL) stain positive non-apoptotic chondrocytes in hypertrophic zone of human chondro-osteophytes. Materials and Methods: Chondro-osteophytes from osteoarthritic patients were obtained at joint replacement surgery. Apoptosis was verified by light microscopic examination of Safranin O stained sections and TUNEL stain. TUNEL staining was also performed on hydrophilic resin embedded semi-thin and ultra-thin sections combined with the treatment with streptavidin-gold conjugates, observed by light microscopy with silver enhancement technique (TUNEL-LM with SE) and transmission electron microscopy (TUNEL-TEM) respectively for the simultaneous evaluation of cellular structure and DNA fragmentation. Results: In paraffin embedded sections (N=18), 31.5 +/- 6.1% of cells in the hypertrophic zone were TUNEL positive, but only 3.8 +/- 1.2% cells in this zone showed apoptotic appearances with cell shrinkage and nuclear condensation. Both in TUNEL-TEM and TUNEL-LM with SE, gold particles, which indicate DNA fragmentation, were observed within the nucleus of morphologically apoptotic chondrocytes, as well as of disintegrated, swollen chondrocytes. Conclusions: In human chondro-osteophytes, hypertrophic chondrocytes might die by oncotic cell death with DNA fragmentation, as well as apoptosis. (C) 2002 OsteoArthritis Research Society International.