Osteoarthritis Synovial Fibroblasts Research Articles

Synoviocytes from osteoarthritis and rheumatoid arthritis produce plasminogen activators and plasminogen activator inhibitor-1 and display u-PA receptors on their surface

The production of plasminogen activators and their inhibitors was studied in vitro in osteoarthritic (OA) and rheumatoid arthritic (RA) synovial fibroblasts (SF), obtained from RA and OA patients undergoing joint surgery. Subcultured SF were cultivated for 2,4, 6, 8, 10 and 13 days and the medium assayed for the presence of both plasminogen activators (PAs) and plasminogen activator inhibitor-1 (PAI-1). The presence of urokinase-Plasminogen Activator (u-PA) receptors (u-PAR) on the surface of synovial cells was investigated by radio-ligand binding assay and crosslinking and by transmission electron microscopy (TEM) of a gold-u-PA complex. Our results showed a low production of tissue-type- Plasminogen Activator (t-PA) in both OA and RA SF, but relatively high levels of u-PA, untill confluence, both in OA and in RA. SF were also able to produce plasminogen activator inhibitor in large amounts, in particular in RA since the very beginning of the culture. Receptors for u-PA were evident on both RA and OA SF. Our data show that SF in vitro produce mainly u-PA, the most important plasminogen activator involved in tissue modifications. The demonstration of u-PA receptors on the surface of OA and RA SF represents a step forward in the understanding of the possible role of fibrinolytic and tissue destructive proteinase cascade in joint inflammation.

Effect of IL-13 on cytokines, cytokine receptors and inhibitors on human osteoarthritis synovium and synovial fibroblasts

Objective: In this study we investigated the effect of interleukin-13 (IL-13), an anti-inflammatory cytokine, for potential therapeutic use in osteoarthritis (OA).Design: We examined the effect of IL-13 on the synthesis and expression of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), IL-1 receptor antagonist (IL-1Ra) and stromelysin-1 on human OA synovial membrane inex vivocultures. In addition, we explored the effect of IL-13 on both the IL-1 receptor (IL-1R) and TNF-receptor (TNF-R) systems on OA synovial fibroblasts. This included determination of the levels of IL-1β and TNF-α receptor binding, IL-1Ra and TNF-soluble receptors 55 and 75 (TNF-sR55 and TNF-sR75).Results: In OA synovial membrane treated with LPS, IL-13 inhibited the synthesis of IL-1β, TNF-α and stromelysin-1, but increased IL-1Ra production. In addition, IL-13 reduced the level of IL-1β mRNA and stimulated the level of IL-1Ra mRNA. In synovial fibroblasts, IL-13 decreased the level of IL-1 binding, an effect related to the increased production of IL-1Ra. Although IL-13 had no effect on the TNF-R level, this cytokine markedly decreased the shedding of TNF-R75.Conclusion: These experiments suggest that IL-13 is potentially useful in the therapeutic treatment of OA, as it could regulate the major pathological process of this disease by reducing the production of proinflammatory cytokines and metalloproteases, and favoring the production of IL-1Ra.

Macrophage Inflammatory Protein-Iβ: A C-C Chemokine in Osteoarthritis

The aim of this study was to determine whether the cytokine macrophage inflammatory protein-1β (MIP1β) is present and functionally active in the arthritic joint. We used immunoassays and bioassays to assess the presence and function of MIP-1β using samples obtained from 62 arthritic patients. MIP-1β levels were increased in synovial fluids (SFs) from patients with osteoarthritis (OA) (18.0 ± 8.9 ng/ml) (SD) compared to patients with rheumatoid arthritis (RA) (6.1 ± 2.9 ng/ml) or other forms of arthritis (10.4 ± 7.0 ng/ml) ( P < 0.05). Levels of OA SF MIP-1β were significantly greater than OA or normal serum levels of MIP-1β. Anti-MIP-1β neutralized 28% of the chemotactic activity for monocytes found in OA SFs. Isolated OA synovial tissue fibroblasts did not constitutively produce MIP-1β but could be induced to express this chemokine upon exposure to tumor necrosis factor-α, interleukin-1β, or lipopolysaccharide. Synovial tissue immunohistochemical staining revealed that the main immunopositive cells in OA were the lining cells as well as vascular smooth muscle and endothelial cells. A minority of macrophages were immunopositive as well. In this study, we identify MIP-1β as a unique cytokine increased in OA compared to RA SF. We conclude that MIP-1β may play a role in the ingress of monocytes into the OA joint.

The Effect of Misoprostol on Arachidonic Acid Mobilization, Prostaglandin E(2), Production, and IL-1beta Signaling.

The effect of misoprostol on interleukin-1beta (IL-1beta)-mediated phospholipid metabolism, arachidonic acid release, and prostaglandin E(2) (PGE(2)) production was examined using normal skin fibroblasts and synovial fibroblasts from patients with osteoarthritis. We found that both IL-1beta and misoprostol induced arachidonic acid release, suggesting enhanced phospholipase A(2) activation. Both Il-1beta and IL-1beta/misoprostol, but not misoprostol alone, induced a significant increase in PGE(2) levels compared with controls. Even though PGE(2) production was not significantly increased by misoprostol alone, misoprostol synergistically enhanced IL-1beta-mediated cyclooxygenase activity (sixfold to eightfold) and PGE(2) synthesis in normal fibroblasts but not in OA synovial fibroblasts. Additionally, misoprostol dramatically affected the arachidonate-labeling of triglyceride and cholesterol ester pools; the significance of this is as yet unclear. Together, the results suggest that misoprostol may upregulate the conversion of arachidonic acid to PGE(2) by enhancing the IL-1beta-induced activation/synthesis of cyclooxygenase.

Epithelial neutrophil activating peptide-78: a novel chemotactic cytokine for neutrophils in arthritis.

We and others have shown that cells obtained from inflamed joints of rheumatoid arthritis (RA) patients produce interleukin-8, a potent chemotactic cytokine for neutrophils (PMNs). However, IL-8 accounted for only 40% of the chemotactic activity for PMNs found in these synovial fluids. Currently, we have examined the production of the novel PMN chemotactic cytokine, epithelial neutrophil activating peptide-78 (ENA-78), using peripheral blood, synovial fluid, and synovial tissue from 70 arthritic patients. RA ENA-78 levels were greater in RA synovial fluid (239 +/- 63 ng/ml) compared with synovial fluid from other forms of arthritis (130 +/- 118 ng/ml) or osteoarthritis (2.6 +/- 1.8 ng/ml) (P < 0.05). RA peripheral blood ENA-78 levels (70 +/- 26 ng/ml) were greater than normal peripheral blood levels (0.12 +/- 0.04 ng/ml) (P < 0.05). Anti-ENA-78 antibodies neutralized 42 +/- 9% (mean +/- SE) of the chemotactic activity for PMNs found in RA synovial fluids. Isolated RA synovial tissue fibroblasts in vitro constitutively produced significant levels of ENA-78, and this production was further augmented when stimulated with tumor necrosis factor-alpha (TNF-alpha). In addition RA and osteoarthritis synovial tissue fibroblasts as well as RA synovial tissue macrophages were found to constitutively produce ENA-78. RA synovial fluid mononuclear cells spontaneously produced ENA-78, which was augmented in the presence of lipopolysaccharide. Immunohistochemical localization of ENA-78 from the synovial tissue of patients with arthritis or normal subjects showed that the predominant cellular source of this chemokine was synovial lining cells, followed by macrophages, endothelial cells, and fibroblasts. Synovial tissue macrophages and fibroblasts were more ENA-78 immunopositive in RA than in normal synovial tissue (P < 0.05). These results, which are the first demonstration of ENA-78 in a human disease state, suggest that ENA-78 may play an important role in the recruitment of PMNs in the milieu of the inflamed joint of RA patients.

Effects of hydrogen peroxide on the metabolism of human rheumatoid and osteoarthritic synovial fibroblasts in vitro.

The effects of hydrogen peroxide (H2O2) on the metabolism of cultured human synovial fibroblasts derived from joints of four patients with rheumatoid arthritis and three with osteoarthritis have been investigated. The exposure of rheumatoid cell cultures to this oxygen derived species at sublethal concentrations (1-100 mumol/l) induced a dose related inhibition of both hyaluronic acid (HA) and DNA synthesis. In contrast, in osteoarthritic cell lines a biphasic response was shown. At low concentrations of H2O2 (less than 10 mumol/l) a stimulatory effect on HA synthesis was noted, whereas in the presence of higher concentrations (greater than 10 mumol/l) a significant inhibition of synthesis occurred. These deleterious effects of H2O2 were partially reduced by the addition of catalase to the culture media. The finding that both HA and DNA synthesis were inhibited at concentrations of H2O2 less than those which caused loss of cell integrity (greater than 200 mumol/l) suggests oxidation of intracellular components, such as glyceraldehyde-3-phosphate dehydrogenase, and subsequent depletion of ATP concentrations.