Objective. The continuous presence of bacteria or their degraded antigens in the synovium may be involved in the pathogenesis of rheumatoid arthritis (RA). The aim of this study was to determine the presence of bacterial nucleic acids and bacterial cell wall constituents in the joints of patients with RA and other forms of arthritis.Methods. Joint samples were obtained from patients with RA (n ‫؍‬ 26), septic arthritis (n ‫؍‬ 2), inflammatory osteoarthritis (n ‫؍‬ 5), and gout (n ‫؍‬ 6), and joint trauma (n ‫؍‬ 1). Universal 16S-ribosomal RNA primers were used to detect the presence of bacterial DNA in these samples, using stringent regimens for sample collection and molecular microbiologic analysis. Automated sequencing and comparative data analysis were performed to identify the species. The presence of bacterial peptidoglycan-polysaccharide complexes in synovial tissue was detected by immunohistologic analysis with a specific antibody.Results. The bacterial species cultured from the synovium could be identified in both of the patients with septic arthritis. DNA amplicons were also detected in the synovial fluid and/or tissue samples from 5 patients with RA and 2 patients with crystal-induced arthritis; these originated from multiple bacterial species. Staining for peptidoglycan-polysaccharide complexes was positive in the synovial tissue of both patients with septic arthritis, 16 with RA, 4 with inflammatory osteoarthritis, 4 with crystal-induced arthropathy, and 1 with joint trauma. The staining was mainly found in cells in the synovial sublining, including macrophages.Conclusion. The results indicate that bacterial DNA and bacterial cell wall constituents are retained in the joints of some patients with arthritis, where they might enhance synovial inflammation.

Objective: To determine protein and activity levels of matrix metalloproteinases 1 and 3 (MMP-1 and MMP-3) in synovial fluid of patients with knee joint injury, primary osteoarthritis, and acute pyrophosphate arthritis (pseudogout). Methods: Measurements were done on knee synovial fluid obtained in a cross sectional study of cases of injury (n = 283), osteoarthritis (n = 105), and pseudogout (n = 65), and in healthy controls (n = 35). Activity of MMP-1 and MMP-3 in a 2 macroglobulin complexes was measured using specific low molecular weight fluorogenic substrates. ProMMP-1, proMMP-3, and TIMP-1 (tissue inhibitor of metalloproteinase 1) were quantified by immunoassay. Results: Mean levels of proMMP-1, proMMP-3, and TIMP-1 were increased in injury, osteoarthritis, and pseudogout compared with controls. MMP-1 activity was increased in pseudogout and injury groups over control levels, whereas MMP-3 activity was increased only in the pseudogout group. The increase in MMP-1 activity coincided with a decrease in TIMP-1 levels in the injury group. Conclusions: Patients with joint injury have a persistent increase in proMMP-1 and proMMP-3 in synovial fluid and an increase in activated MMPs, which are not inhibited by TIMP. The differences in activation and inhibition patterns between the study groups are consistent with disease specific patterns of MMP activation and/or inhibition in joint pathology.

Objective: To analyse matrix metalloproteinases (MMPs) and tissue inhibitor-1 of MMPs (TIMP-1) levels in the systemic circulation and synovial fluid (SF) of patients with RA and to compare these levels with inflammatory and collagen degradation markers. Methods: ProMMP-1, -2, -3, -8, -9, TIMP-1, levels of MMP/ a 2 -macroglobulin complexes, and collagen degradation products were measured by sandwich ELISA, activity assays, and HPLC in paired SF and serum samples from 15 patients with RA and 13 with OA. Results: MMPs were higher in SF of patients with RA than in OA or controls. MMP levels in SF of patients with OA were higher than in controls. In serum, levels of proMMP-3, -8 and -9 were higher in patients with RA than in OA or controls, whereas only proMMP-8 and -9 were higher in serum of patients with OA than in controls. A strong correlation was seen between serum and SF levels of MMP-8 and -9 in RA. Increased levels of MMP/a 2 -macroglobulin complexes indicated an MMP/TIMP imbalance in serum and SF in RA. SF hydroxyproline correlated significantly with SF levels of proMMP-9 in RA. Conclusions: Systemic MMP-8 and -9 levels represent the situation in the inflamed joint; MMP-9 is likely to be involved in degradation of joint collagen. The hypothesis of MMP/ TIMP imbalance in RA is strengthened.

Objective: To analyse the relation between systemic levels of pro-MMP-3, -8, and -9 matrix metalloproteinase (MMP) activity in a 2 macroglobulin (a 2 M)/MMP complexes and the progression of joint destruction in patients with recent onset rheumatoid arthritis (RA). Methods: 109 patients with RA of recent onset were entered into this longitudinal study. Patients were followed up for two years; clinical data, blood samples, and radiographs were obtained at baseline and at 1 and 2 years. Serum levels of MMPs were measured by sandwich ELISA and MMP activity assays. Results: During the two years joint damage progressed from 0 to 10 (median Sharp score, p,0.001). Stable levels of pro-MMP-3 and a significant decrease in the levels of pro-MMP-8 and -9 and a 2 M/MMP complexes were seen throughout the two years. Regression analysis showed that serum pro-MMP-3 levels at disease onset were independently associated with the progression of joint damage (B = 0.7, 95% CI 0.3 to 1

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