To determine the steady-state of messenger RNA (mRNA) levels of syndecan-1 and syndecan-4 in cartilage samples and chondrocytes derived from human osteoarthritic knee joints.
Steady-state levels of gene-specific mRNA (relative to beta-actin) were measured by semiquantitative polymerase chain reaction (PCR).
RT-PCR allowed detection of syndecan-1 (for the first time) and syndecan-4 in both cartilage samples and articular chondrocytes cultured as primary monolayers. The mRNA levels of syndecan-1 were reduced in cartilage tissue from heavily damaged compared to normal-looking areas whereas those of syndecan-4 were significantly increased. In contrast, the expression of syndecan-1 was higher in cultured chondrocytes derived from the fibrillated osteoarthritic cartilage than in cells obtained from intact cartilage, while the syndecan-4 message levels did not differ between the two sites.
The expression of the cell-surface syndecans 1 and 4 is altered during the osteoarthritic degradative process of the knee joint. The discoordinate syndecan gene expression, which is probably related to the chondrocyte proliferation and clustering, may contribute to the disorganization of the cartilage and the development of OA processes. Isolation and culturing the chondrocytes as monolayers dramatically change the expression of these genes and cannot reflect the in situ condition.