To assess the presence of fibroblast collagenase (MMP-1), neutrophil collagenase (MMP-8), and collagenase 3 (MMP-13) in osteoarthritic (OA) cartilage, with particular emphasis on areas of macroscopic cartilage erosion.
Messenger RNA (mRNA) levels were assessed by reverse transcriptase-polymerase chain reaction (RT-PCR), in situ hybridization, and Northern blot analysis.
MMP-1 and MMP-13 were expressed at higher levels by OA chondrocytes than by normal chondrocytes. In addition, mRNA for MMP-8 was present in OA cartilage but not normal cartilage by PCR and Northern blot analyses. Chondrocytes from areas surrounding the OA lesion expressed greater quantities of MMP-1 and MMP-13 compared with normal chondrocytes, suggesting local modulation by mechanical and inflammatory factors. Tumor necrosis factor alpha stimulated the expression of all 3 collagenases. Retinoic acid, an agent which induces autodigestion of cartilage in vitro, stimulated only the expression of MMP-13.
These findings suggest a key role of MMP-13 and MMP-8, as well as MMP-1 in osteoarthritis.