EXPRESSION OF TYPE-X COLLAGEN IN OSTEOARTHRITIS

The present study was undertaken to examine how osteoarthritis affects the expression of type-X collagen, a hypertrophic chondrocyte-specifi c collagen in articular cartilage. A well characterized sheep polyclon al antiserum, as well as three mouse monoclonal antibodies against can ine type-X collagen, was used to immunolocalize type-X collagen in hum an and canine joints. Its expression in osteoarthritic cartilage was a ltered in several locations. In the canine osteoarthritic joints, type -X collagen increased in and just above the zone of calcified cartilag e and was present diffusely throughout the calcified matrix. In both t he human and canine cartilage, type-X collagen was localized around ce ll clones in the transitional zone of cartilage. This is surprising, s ince that region of the cartilage does not calcify and one of the prop osed roles of type-X collagen is in mineralization, Thus, the osteoart hritic process may damage the matrix in the superficial layer and indu ce changes leading to the expression of the hypertrophic chondrocyte p henotype.