CD44 expression on chondrocytes in knees of DBA/1 mice with type II collagen-induced arthritis

To investigate aspects of CD44 expression in the cartilage destruction of the knees of mice with collagen-induced arthritis.

DBA/1 mice were immunized with bovine type II collagen emulsified with Freund's incomplete adjuvant. Histological changes in the knees were evaluated in sections stained with hematoxylin and eosin, toluidine blue, and immunostaining using anti-CD44 monoclonal antibodies.

CD44 expression was observed in the synovial lining and articular chondrocytes. A total of 10/10 knees had CD44-positive synovial lining cells at 6 weeks after immunization, which was higher than that at 4 weeks (7 of 10 knees, p < 0.05). At 4 weeks 3 of 10 knees with CD44-positive chondrocytes were observed, and 7 of 10 knees at 6 weeks after immunization. The number of knees at 6 weeks was higher than that at 4 weeks (p < 0.01). Nine of 10 knees showed loss of metachromasia on toluidine blue staining at 6 weeks after immunization, which was higher than the number at 4 weeks. The grade of metachromasia loss and the length of time after immunization were significantly correlated (p < 0.05, Spearman rank correlation; p = 0.46).

These findings suggest that CD44 may play some role in the early stage of cartilage destruction in DBA/1 mice immunized with type II collagen.