Immunohistochemical analysis of 3-B-(-) and 7-D-4 epitope expression in canine osteoarthritis

To examine the distribution of the 3-B-3(-) and 7-D-4 epitopes in proteoglycans from morphologically normal and osteoarthritic (OA) canine articular cartilage.

Cartilage samples from the femurs of stable and destabilized stifle joints of 9 dogs that had undergone transection of the cranial cruciate ligament were examined by immunohistochemistry.

The 3-B-3(-) and 7-D-4 epitopes were expressed in the superficial zone of cartilage from the destabilized femorotibial joints in the early stages of developing OA. The staining patterns with these two antibodies differed, with 3-B-3(-) reactivity confined to the superficial and upper middle zones of the articular cartilage, and 7-D-4 reactivity more prominent in the matrix, extending into the deeper zones and increasing with progression of the lesion. Both epitopes were also expressed in the superficial and upper middle zones of areas peripheral to the lesions and were detectable before the loss of matrix and proteoglycans could be identified by histochemical staining with toluidine blue.

In this study, the expression of atypical chondroitin sulfate proteoglycans was demonstrated in osteoarthritic canine cartilage, and the pattern of expression changed as the lesions progressed. The occurrence of 3-B-3(-) and 7-D-4 epitopes appears to be associated with changes in chondrocyte metabolism in the early stages of cartilage degeneration in experimental osteoarthritis.