Expression of early and late differentiation markers (proliferating cell nuclear antigen, syndecan-3, annexin VI, and alkaline phosphatase) by human osteoarthritic chondrocytes

Although osteoarthritis is characterized by a progressive loss of the extra cellular cartilage matrix, very little is known about the fate of articular chondrocytes during the progression of the disease. In this study we exami ned the expression of syndecan-3, a marker of early chondrocyte differentia tion, and annexin VI, a marker of late chondrocyte differentiation, in mamm alian embryonic growth plate cartilage and normal and osteoarthritic human articular cartilage. Whereas syndecan-3 was expressed in the proliferative and hypertrophic zones of growth plate cartilage, immunostaining for annexi n VI was predominately found in the hypertrophic and mineralizing zones of fetal bovine growth plate cartilage. Approximately 20% of chondrocytes were immunopositive for syndecan-3 in normal human articular cartilage, the num ber of syndecan-3-expressing chondrocytes significantly increased during th e progression of osteoarthritis with more than 80% syndecan-3-positive cell s in the upper zone of severely affected osteoarthritic cartilage. Similarl y, the number of annexin VI-expressing cells significantly increased in the upper cartilage zones during the progression of osteoarthritis. Furthermor e, immunostaining for proliferating cell nuclear antigen, a marker for cell proliferation, was detected in chondrocytes; in the upper zone of osteoart hritic cartilage. Double-labeling experiments with antibodies against synde can-3 and annexin VI revealed chondrocytes; that expressed only syndecan-3, and cells that expressed both syndecan-3 and annexin VL These results sugg est that the expression of early (proliferating cell nuclear antigen, synde can-3) and late differentiation markers (annexin VI, alkaline phosphatase) is activated in chondrocytes of osteoarthritic cartilage.