The objective of this study was to detail the topographical and zonal distribution of the cell adhesion molecule CD44 in normal and osteoarthritic cartilage.
Immunohistochemistry utilizing well characterized anti-CD44 antibodies (clones A3D8, Bric 235, 2C5) was performed on cryostat and paraffin sections of human articular cartilage from macroscopically normal (n = 18) and osteoarthritic (n = 11) femoral heads. Samples for cryostat sections were obtained from 12 topographically different sites. Sections were divided into zones (superficial, middle, deep) and the CD44 staining scored. Chondrocytes in normal articular cartilage and cartilage from osteoarthritic femoral heads stained positive for CD44 in both cryostat and paraffin sections. Normal cartilage showed a significant decrease in CD44 staining in the deep zone as compared to the superficial zone (P < 0.05). However, cryostat sections of residual cartilage from osteoarthritic femoral heads showed increased CD44 staining in the deep zone as compared to normal articular cartilage. The CD44 staining showed no topographical variation in either the normal cartilage or the osteoarthritic residual cartilage.
CD44 expression displays a distinct zonal variation in normal articular cartilage which is lost in osteoarthritic cartilage due to an up-regulated expression in the deep zone. CD44 expression does not exhibit topographical variation.