RAGE activation induces invasiveness of RA fibroblast-like synoviocytes in vitro.

Ligands for the receptor for advanced glycation endproducts (RAGE) are increased in RA synovial fluid (SF), serum and synovium. Since RAGE is present on fibroblast-like synoviocytes (FLS), the present study investigates whether the RAGE ligands HMGB-1 and AGEs are able to stimulate the characteristic, pathological invasive behaviour of these cells. FLS were obtained during joint replacement surgery. FLS were seeded in serum free medium with HMGB-1 or glycated albumin (BSA-AGE) on transwell filters coated with Matrigel. The lower compartment contained medium with serum as a chemoattractant. After three days, the percentage of invading cells was determined and compared to the control invasion. Stimulation with HMGB-1 increased invasiveness to 125% compared to the control (p = 0.001). Addition of anti-RAGE antibody reduced this back to baseline (98%, p = 0.002). Stimulation with BSA-AGE, another RAGE ligand, increased invasiveness to 150% compared to the control (p = 0.003). Addition of anti RAGE was again able to reduce the increased invasiveness back to baseline (95%, p = 0.008). HMGB-1 and BSA-AGE stimulated the invasiveness of RA-FLS by activation of RAGE. As such, RAGE may be an interesting target for therapy directed at the inhibition of synoviocyte activation.

Fibroblast-like synoviocyte-chondrocyte interaction in cartilage degradation.

OBJECTIVE: In vitro models for joint diseases often focus on a single cell type, such as chondrocytes in osteoarthritis (OA) or fibroblast-like synoviocytes (synoviocytes) in rheumatoid arthritis (RA). However, these joint diseases affect the whole joint and interaction between chondrocytes and synoviocytes may play an important role in disease pathology. The current study was designed to study the use of the alginate recovered chondrocyte method as a model for cartilage degradation and to study interaction between chondrocytes and synoviocytes. METHODS: Bovine chondrocytes were cultured in alginate beads for 1 week, subsequently chondrons were retrieved and seeded into transwells. Every two days cartilage-slices were analysed for proteoglycan content (colorimetric, Blyscan GAG kit), collagen content (HPLC) and collagen HP and LP crosslinking (HPLC). For degradation experiments, monocultures of cartilage-slices labelled with (35)S and cocultures with synoviocytes were stimulated with IL-1beta or TNF-alpha. After 7 days, (35)S release was measured taken as a measure of cartilage degradation. RESULTS: After biochemical analysis, three week old cartilage-like slices were chosen to perform cartilage-degradation experiments. Synoviocytes were able to induce cartilage degradation only in the presence of living chondrocytes. In addition, the cytokines interleukin 1 (IL-1beta) and tumor necrosis factor (TNF-alpha) were only able to induce cartilage degradation by chondrocytes, not by synoviocytes. CONCLUSION: These data indicate that the alginate recovered chondrocyte method provides a novel model for cartilage degradation in which the interaction between synoviocytes and chondrocytes can be studied.