title: Characterization of apoptosis in articular cartilage derived from the knee joints of patients with osteoarthritis.
abstract: OBJECTIVE
  the present study was conduced in order to analyse the molecular changes during the apoptotic cascade in knee articular cartilage of patients with OA.
  
  
  METHODS
  articular cartilage specimens were assessed by histology (Haematoxylin and Eosin), histochemistry (Masson's Trichromic and Alcian Blue), immunohistochemistry through TRAIL, DR5 and Caspase-3, TUNEL and Hoechst staining in fresh isolated chondrocytes.
  
  
  RESULTS
  histology results demonstrated the structural alterations in the articular knee cartilage with OA, and histochemistry results demonstrated the presence of matrix calcification and a proteoglycans reduction. Immunohistochemistry staining showed that structural alterations, matrix calcification and a proteoglycans reduction coincided with an increase in apoptotic cells when compared to normal cartilage; however, this cellular mechanism of death was demonstrated by TUNEL and Hoechst 33258 staining in fresh isolated chondrocytes.
  
  
  CONCLUSIONS
  in this study, we demonstrated an apoptosis activation by the extrinsic pathway in OA cartilage. The apoptosis-positive cells might be due to a protection mechanism after sublethal injury, in particular, represented by an increased survival of chondrocytes that are able to participate in the repair process.
authors.affiliation: Department of Anatomy, Diagnostic Pathology, Forensic Medicine, Hygienic and Public Health, University of Catania, Via S. Sofia 87, 95123 Catania, Italy. g.musumeci@unict.it
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Musumeci
authors.forename: Carla
authors.initials: C
authors.lastname: Loreto
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Carnazza
authors.forename: Giuseppa
authors.initials: G
authors.lastname: Martinez
mesh_terms: D017209:Apoptosis; D002358:Cartilage, Articular / Q000503:physiopathology*; D006801:Humans; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D007719:Knee Joint / Q000473:pathology*; D020370:Osteoarthritis, Knee / Q000503:physiopathology*