Rheumatoid fibroblast‐like synoviocytes overexpress the chemokine stromal cell–derived factor 1 (CXCL12), which supports distinct patterns and rates of CD4+ and CD8+ T cell migration within synovial tissue

Objective

A characteristic feature of the inflammatory infiltrate in rheumatoid arthritis is the segregation of CD4 and CD8 T lymphocyte subsets into distinct microdomains within the inflamed synovium. The aim of this study was to test the hypothesis that chemokines in general and stromal cell–derived factor 1 (SDF‐1; CXCL12) in particular are responsible for generating this distinctive microcompartmentalization.

Methods

We examined how synovial CD4/CD8 T cell subsets interacted in coculture assays with fibroblasts derived from chronic inflammatory synovial lesions and normal synovial tissue as well as from fetal lung and adult skin. We used the ability of T cells to migrate beneath fibroblasts (a process called pseudoemperipolesis) as an in vitro marker of T cell accumulation within synovial tissue.

Results

Rheumatoid fibroblast‐like synoviocytes (FLS) displayed a unique ability to support high levels of CD4 and CD8 T cell pseudoemperipolesis. Nonrheumatoid FLS as well as fetal lung fibroblasts supported low levels of pseudoemperipolesis, while skin‐derived fibroblasts were unable to do so. CD8 T cells migrated under fibroblasts more efficiently and at a higher velocity than CD4 T cells, a feature that was intrinsic to CD8 T cells. Rheumatoid fibroblasts constitutively produced high levels of SDF‐1 (CXCL12), which was functionally important, since blocking studies showed reductions in T cell pseudoemperipolesis to levels seen in nonrheumatoid FLS. Rheumatoid fibroblasts also constitutively produced high levels of vascular cell adhesion molecule 1 (VCAM‐1; CD106), but this did not contribute to T cell pseudoemperipolesis, unlike the case for B cells, which require SDF‐1 (CXCL12)–CXCR4 and CD49d–VCAM‐1 (CD106) interactions. Importantly, only combinations of rheumatoid FLS and rheumatoid‐derived synovial fluid T cells supported pseudoemperipolesis when examined ex vivo, confirming the in vivo relevance of these findings.

Conclusion

These studies demonstrate that features intrinsic to both fibroblasts (the production of SDF‐1) and CD8/CD4 T cells (the expression of CXCR4) are responsible for the characteristic pattern of T lymphocyte accumulation seen in the rheumatoid synovium. These findings suggest that the SDF‐1/CXCR4 ligand/receptor pair is likely to play an important functional role in T lymphocyte accumulation and positioning within the rheumatoid synovium.

     

Up-regulation of stromal cell-derived factor 1 (CXCL12) production in rheumatoid synovial fibroblasts through interactions with T lymphocytes: role of interleukin-17 and CD40L-CD40 interaction

OBJECTIVE: Stromal cell-derived factor 1 (SDF-1) is a potent chemoattractant for memory T cells in inflamed rheumatoid arthritis (RA) synovium. This study was undertaken to investigate the effect of interleukin-17 (IL-17) and CD40-CD40L interaction on SDF-1 production in RA fibroblast-like synoviocytes (FLS). METHODS: Synovial fluid (SF) and serum levels of SDF-1 in RA patients were measured by enzyme-linked immunosorbent assay (ELISA). The SDF-1 produced by cultured RA FLS was evaluated by real-time polymerase chain reaction and ELISA after FLS were treated with IL-17 and inhibitors of intracellular signal molecules. The SDF-1 level was also determined after FLS were cocultured with T cells in the presence and absence of IL-17. RESULTS: Concentrations of SDF-1 in the sera and SF were higher in RA patients than in osteoarthritis patients, although the increase in the serum levels did not reach statistical significance. The production of SDF-1 in RA FLS was enhanced by IL-17 stimulation. This effect of IL-17 was blocked by inhibitors of phosphatidylinositol 3-kinase (PI 3-kinase), NF-kappaB, and activator protein 1 (AP-1). When FLS were cocultured with T cells, SDF-1 production was up-regulated, especially in the presence of IL-17, but FLS were inhibited by neutralizing anti-IL-17 and anti-CD40L antibodies. Addition of RA SF to cultured RA FLS significantly up-regulated SDF-1 messenger RNA expression, which was hampered by pretreatment with anti-IL-17 antibody. CONCLUSION: SDF-1 is overproduced in RA FLS, and IL-17 could up-regulate the expression of SDF-1 in RA FLS via pathways mediated by PI 3-kinase, NF-kappaB, and AP-1. Our findings suggest that inhibition of the interaction between IL-17 from T cells and SDF-1 in FLS may provide a new therapeutic approach in RA.     

Up‐regulation of stromal cell–derived factor 1 (CXCL12) production in rheumatoid synovial fibroblasts through interactions with T lymphocytes: Role of interleukin‐17 and CD40L–CD40 interaction

Objective

Stromal cell–derived factor 1 (SDF‐1) is a potent chemoattractant for memory T cells in inflamed rheumatoid arthritis (RA) synovium. This study was undertaken to investigate the effect of interleukin‐17 (IL‐17) and CD40–CD40L interaction on SDF‐1 production in RA fibroblast‐like synoviocytes (FLS).

Methods

Synovial fluid (SF) and serum levels of SDF‐1 in RA patients were measured by enzyme‐linked immunosorbent assay (ELISA). The SDF‐1 produced by cultured RA FLS was evaluated by real‐time polymerase chain reaction and ELISA after FLS were treated with IL‐17 and inhibitors of intracellular signal molecules. The SDF‐1 level was also determined after FLS were cocultured with T cells in the presence and absence of IL‐17.

Results

Concentrations of SDF‐1 in the sera and SF were higher in RA patients than in osteoarthritis patients, although the increase in the serum levels did not reach statistical significance. The production of SDF‐1 in RA FLS was enhanced by IL‐17 stimulation. This effect of IL‐17 was blocked by inhibitors of phosphatidylinositol 3‐kinase (PI 3‐kinase), NF‐κB, and activator protein 1 (AP‐1). When FLS were cocultured with T cells, SDF‐1 production was up‐regulated, especially in the presence of IL‐17, but FLS were inhibited by neutralizing anti–IL‐17 and anti‐CD40L antibodies. Addition of RA SF to cultured RA FLS significantly up‐regulated SDF‐1 messenger RNA expression, which was hampered by pretreatment with anti–IL‐17 antibody.

Conclusion

SDF‐1 is overproduced in RA FLS, and IL‐17 could up‐regulate the expression of SDF‐1 in RA FLS via pathways mediated by PI 3‐kinase, NF‐κB, and AP‐1. Our findings suggest that inhibition of the interaction between IL‐17 from T cells and SDF‐1 in FLS may provide a new therapeutic approach in RA.