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This study examined in an arthritis animal model whether elderly onset rheumatoid arthritis (EORA) is a more severe disease than younger onset rheumatoid arthritis. Arthritis was induced by injecting 5% kaolin/carrageenan into the left tibiotarsal ankles of 18-month-old and 4-week-old rats. Various parameters were measured to evaluate the arthritic progression of kaolin/carrageenan-induced arthritis in the rats. Immunohistochemical staining of arthritic joints was performed to determine the degree of inflammation in old and young rats. Measurements of ankle volume and thickness, arthritic index, number of squeaks, and the paw pressure test showed the 18-month-old rats had more severe disease than the young rats in a kaolin/carrageenan-induced arthritis model. The degree of inflammation and MMP-1 expression of arthritic joints in old rats was significantly higher than that of young rats based on histological evaluation with hematoxylin and eosin (H&E) staining and immunochemistry. More severe disease symptoms were found in old rats with EORA, but the molecular mechanisms still remain to be elucidated. Understanding the molecular mechanisms will be helpful to develop clinical protocols to efficiently treat patients with EORA, which is difficult to control with current protocols.

We examined whether the expression and activation of pro-matrix metalloproteinase (MMP)-1 varies from that of pro-MMP-13 in the joint fluid of osteoarthritis (OA) and rheumatoid arthritis (RA) patients. To do this, joint fluid was collected from 34 RA and 34 OA patients. The collagenase (pro-MMP-1 and MMP-13, total MMP-1, and MMP-13), gelatinase (total MMP-2 and MMP-9), stromelysin (total MMP-3), matrilysin (total MMP-7), uPA, and tissue inhibitor of MMP (TIMP) levels were measured by ELISA. The level of total MMP-1 in RA joint fluids was similar to that of the OA joint fluid. In contrast, the level of total MMP-13 in the RA group was significantly higher than that of the OA group. Among various MMPs (MMP-2, MMP-3, MMP-7, and MMP-9), only MMP-9 was strongly associated with total MMP-13 in both RA and OA. The level of uPA was also strongly associated with MMP-13 in RA but not OA, while the level of TIMP-1 and TIMP-2 was not significantly different between RA and OA. In conclusion, MMP-9 and uPA might be involved in the activation of pro-MMP-13 through unknown mechanisms in arthritic diseases.

Primary synovial cells with high passage number demonstrate increased production of proinflammatory mediators in response to inflammatory stimuli compared with cells with low passage number. This study used synovial cells to learn how different numbers of serial subculture passages affect the production of proinflammatory mediators in response to interleukin (IL)-1β. Synovial cells were serially subcultured in flasks until passage 7. During cell passage, synovial cells were treated with IL-1β for 24 h. Levels of proinflammatory mediators were analyzed by ELISA, real-time PCR, and Western blot. Synovial cells at passage 7 had elongated morphology and higher activity of β-galactosidase, a marker of senescence, than those at passage 3. Production of IL-6, IL-8, vascular endothelial growth factor (VEGF), and prostaglandin E2 (PGE(2)) in response to IL-1β was significantly increased in cells at passage 7 compared with passage 3. To evaluate the mechanism of this different response, IL-1 receptor expression was studied in cells stimulated with IL-1β. Compared with cells at passage 3, cells at passage 7 had stronger expression of IL-1 receptors 1 and 2, as well as significantly increased expression of both receptors, in response to IL-1β. This finding suggests that differential production in response to inflammatory stimuli associated with cell passages should be considered when in vitro experiments are used to evaluate the production levels of proinflammatory mediators.

This study was performed to provide evidence, albeit indirectly, as to which matrix metalloproteinases (MMPs), among the gelatinases MMP-2 and MMP-9 and the collagenases MMP-1 and MMP-13, play a more proactive role in the angiogenic process in arthritic joint. Joint fluid was collected from 33 patients with rhuematoid arthritis (RA) and osteoarthritis (OA), and protein (MMPs and vascular endothelial growth factor (VEGF)) levels were measured by ELISA, and the association of MMPs with VEGF was evaluated in joint fluid of patients with RA or OA. The levels of collagenases (total MMP-1 and total MMP-13) and gelatinases (total MMP-2 and total MMP-9) in RA joint fluid were significantly higher than those in OA fluid. Total MMP-9 levels were significantly associated with VEGF levels in RA fluids, but not in OA fluid, while total MMP-13 levels were strongly associated with VEGF levels in both RA and OA fluid. However, total MMP-2 and total MMP-1 levels were not associated with VEGF levels in either RA or OA joint fluid. Our results indirectly suggest that in RA and OA, MMP-9 and MMP-13 may play a more important role in angiogenesis than MMP-2 and MMP-1.

This study was performed to investigate the frequency of human leukocyte antigen (HLA)-B27 subtypes in the Korean population with spondyloarthropathy (SpA). We determined the HLA subtypes of 267 SpA patients who were positive for the B27 antigen (as determined by serology) by using a PEL-FREEZ kit (Dynal Biotech, Wisconsin, USA). Clinical features, including sex, peripheral joint involvement, and the presence of uveitis, were analyzed in a retrospective cohort study. Among 267 patients, 244 were B*2705-positive and 22 were B*2704-positive. One patient was positive for B*2704/2705. No other subtype was observed among the analyzed patients. We found that HLA-B*2705 was the predominant subtype in Koreans with SpA; this finding is remarkable because other Asians such as the Han or the Japanese exclusively have the B*2704 subtype. This result suggests that the clinical features and prevalence of SpA in Koreans may be similar to those observed in Europeans.

Primary synovial cells with high passage number demonstrate increased production of proinflammatory mediators in response to inflammatory stimuli compared with cells with low passage number. This study used synovial cells to learn how different numbers of serial subculture passages affect the production of proinflammatory mediators in response to interleukin (IL)-1β. Synovial cells were serially subcultured in flasks until passage 7. During cell passage, synovial cells were treated with IL-1β for 24 h. Levels of proinflammatory mediators were analyzed by ELISA, real-time PCR, and Western blot. Synovial cells at passage 7 had elongated morphology and higher activity of β-galactosidase, a marker of senescence, than those at passage 3. Production of IL-6, IL-8, vascular endothelial growth factor (VEGF), and prostaglandin E2 (PGE(2)) in response to IL-1β was significantly increased in cells at passage 7 compared with passage 3. To evaluate the mechanism of this different response, IL-1 receptor expression was studied in cells stimulated with IL-1β. Compared with cells at passage 3, cells at passage 7 had stronger expression of IL-1 receptors 1 and 2, as well as significantly increased expression of both receptors, in response to IL-1β. This finding suggests that differential production in response to inflammatory stimuli associated with cell passages should be considered when in vitro experiments are used to evaluate the production levels of proinflammatory mediators.

Inflammation in the joint of rheumatoid arthritis is a complex immune reaction facilitated by various factors, such as cytokines, cells and hypoxia. Thus, we evaluated their relative capacity to produce proinflammatory mediators in response to IL-1beta, TNF-alpha or IL-17 under hypoxia or normoxia in fibroblast-like synoviocytes (FLSs) and macrophages. The level of IL-6 expression was strongly increased in both FLSs and THP-1 macrophages in response to IL-1beta and TNF-alpha, but the level by TNF-alpha was less than that by IL-1beta. In contrast, the expression of IL-8 in both cell types was strongly stimulated by both IL-1beta and TNF-alpha. In FLSs, PGE(2) production increased only in response to IL-1beta; and no effect was observed in THP-1 cells and TNF-alpha-stimulated FLSs. In addition, the production by IL-17 was extremely low when compared with those induced by IL-1beta or TNF-alpha in FLSs and THP-1 cells. Hypoxia (2% O(2)) decreased IL-1beta-stimulated production of PGE(2), even though it increased the expression of mRNA and protein of COX-2. These results suggest that IL-1beta and TNF-alpha differentially regulate gene expression in FLSs and macrophages under hypoxia or normoxia.