ADAMTS-1, a gene product of articular chondrocytes in vivo and in vitro, is downregulated by interleukin 1beta.

OBJECTIVE

Osteoarthritic (OA) cartilage degeneration and cartilage destruction in rheumatoid arthritis depends significantly on enzymatic degradation of cartilage proteoglycan aggrecan. A member of the ADAMTS family of proteases, ADAMTS-1 was described to have "aggrecanase" activity. We investigated the quantitative expression and distribution of ADAMTS-1 in healthy and OA cartilage and in cultured articular chondrocytes with and without stimulation by interleukin 1beta (IL-1beta) and insulin-like growth factor-I (IGF-I).

METHODS

Conventional and online polymerase chain reaction (PCR) technology was used to determine ADAMTS-1 mRNA expression levels of ADAMTS-1. Protein was localized using immunostaining with different polyclonal antibodies.

RESULTS

Conventional and online semiquantitative PCR showed significant levels of ADAMTS-1 mRNA expression in normal and OA chondrocytes in vivo and in vitro. Only a slight increase was observed in OA cartilage. After stimulation with IL-1beta a downregulation of ADAMTS-1 was observed, whereas IGF did not appear to change mRNA expression levels in vitro. The in vivo mRNA expression results were confirmed by the presence of significant protein staining with antibodies for ADAMTS-1 in normal and OA chondrocytes as well as Western blotting analysis. Whereas a significantly stronger stain was seen in normal articular cartilage in the upper zones, in OA cartilage as well the middle zone showed enhanced staining.

CONCLUSION

Our results confirm the expression and presence of ADAMTS-1 in articular cartilage. However, they also point out that ADAMTS-1 appears to be constitutively expressed by adult articular chondrocytes and overall is not strongly upregulated in OA. Thus our data suggest that ADAMTS-1 is the first matrix-degrading enzyme downregulated by the catabolic factor IL-1beta in vitro.