Immunohistochemical Localization of Cartilage-Specific and Non-Cartilage-Specific Proteoglycans in Experimental Osteoarthritic Articular Cartilage in Rats

To demonstrate the localization of cartilage-specific or abnormal proteoglycans in normal and osteoarthritic joints, chondroitin-4-sulfate, keratan sulfate, and dermatan sulfate were examined immunohistochemically using monoclonal antibodies in control and mechanically induced osteoarthritic rat knee joints. Chondroitin-4-sulfate (CS-4) was observed both pericellularly and intracellularly, and keratan sulfate (KS) was observed mainly pericellularly, in normal cartilage. In early osteoarthritic joints, these immunohistochemical reactions were enhanced. In contrast, dermatan sulfate (DS) was not observed in control cartilage but appeared only in osteoarthritic knees intracellularly and extracellularly. Increased production of cartilage-specific proteoglycans is suspected to be a protective reaction of mechanically stressed chondrocytes, although it was not clear whether production of abnormal small proteoglycan DS represented a chondroprotective reaction or initiated destructive changes of the articular cartilage.