Articular cartilage and changes in Arthritis: Cell biology of osteoarthritis
1 Department of Orthopaedic Surgery, Washington University School of Medicine, St Louis, MO, USA
2 Cartilage Research - Department of Pathology, University of Erlangen-Nurnberg, Erlangen, Germany
Arthritis Res 2001, 3:107-113 doi:10.1186/ar148Published: 22 January 2001
The reaction patterns of chondrocytes in osteoarthritis can be summarized in five categories: (1) proliferation and cell death (apoptosis); changes in (2) synthetic activity and (3) degradation; (4) phenotypic modulation of the articular chondrocytes; and (5) formation of osteophytes. In osteoarthritis, the primary responses are reinitiation of synthesis of cartilage macromolecules, the initiation of synthesis of types IIA and III procollagens as markers of a more primitive phenotype, and synthesis of active proteolytic enzymes. Reversion to a fibroblast-like phenotype, known as 'dedifferentiation', does not appear to be an important component. Proliferation plays a role in forming characteristic chondrocyte clusters near the surface, while apoptosis probably occurs primarily in the calcified cartilage.