Stromal cell markers are differentially expressed in the synovial tissue of patients with early arthritis.

INTRODUCTION: Previous studies have shown increased expression of stromal markers in synovial tissue (ST) of patients with established rheumatoid arthritis (RA). Here, ST expression of stromal markers in early arthritis in relationship to diagnosis and prognostic outcome was studied. METHODS: ST from 56 patients included in two different early arthritis cohorts and 7 non-inflammatory controls was analysed using immunofluorescence to detect stromal markers CD55, CD248, fibroblast activation protein (FAP) and podoplanin. Diagnostic classification (gout, psoriatic arthritis, unclassified arthritis (UA), parvovirus associated arthritis, reactive arthritis and RA), disease outcome (resolving vs persistent) and clinical variables were determined at baseline and after follow-up, and related to the expression of stromal markers. RESULTS: We observed expression of all stromal markers in ST of early arthritis patients, independent of diagnosis or prognostic outcome. Synovial expression of FAP was significantly higher in patients developing early RA compared to other diagnostic groups and non-inflammatory controls. In RA FAP protein was expressed in both lining and sublining layers. Podoplanin expression was higher in all early inflammatory arthritis patients than controls, but did not differentiate diagnostic outcomes. Stromal marker expression was not associated with prognostic outcomes of disease persistence or resolution. There was no association with clinical or sonographic variables. CONCLUSIONS: Stromal cell markers CD55, CD248, FAP and podoplanin are expressed in ST in the earliest stage of arthritis. Baseline expression of FAP is higher in early synovitis patients who fulfil classification criteria for RA over time. These results suggest that significant fibroblast activation occurs in RA in the early window of disease.

Triggering of the dsRNA sensors TLR3, MDA5, and RIG-I induces CD55 expression in synovial fibroblasts.

BACKGROUND: CD55 (decay-accelerating factor) is a complement-regulatory protein highly expressed on fibroblast-like synoviocytes (FLS). CD55 is also a ligand for CD97, an adhesion-type G protein-coupled receptor abundantly present on leukocytes. Little is known regarding the regulation of CD55 expression in FLS. METHODS: FLS isolated from arthritis patients were stimulated with pro-inflammatory cytokines and Toll-like receptor (TLR) ligands. Transfection with polyinosinic-polycytidylic acid (poly(I:C)) and 5'-triphosphate RNA were used to activate the cytoplasmic double-stranded (ds)RNA sensors melanoma differentiation-associated gene 5 (MDA5) and retinoic acid-inducible gene-I (RIG-I). CD55 expression, cell viability, and binding of CD97-loaded beads were quantified by flow cytometry. RESULTS: CD55 was expressed at equal levels on FLS isolated from patients with rheumatoid arthritis (RA), osteoarthritis, psoriatic arthritis and spondyloarthritis. CD55 expression in RA FLS was significantly induced by IL-1ß and especially by the TLR3 ligand poly(I:C). Activation of MDA5 and RIG-I also enhanced CD55 expression. Notably, activation of MDA5 dose-dependently induced cell death, while triggering of TLR3 or RIG-I had a minor effect on viability. Upregulation of CD55 enhanced the binding capacity of FLS to CD97-loaded beads, which could be blocked by antibodies against CD55. CONCLUSIONS: Activation of dsRNA sensors enhances the expression of CD55 in cultured FLS, which increases the binding to CD97. Our findings suggest that dsRNA promotes the interaction between FLS and CD97-expressing leukocytes.

Mycophenolate mofetil but not atorvastatin attenuates atherosclerosis in lupus-prone LDLr(-/-) mice.

RATIONALE: Recent clinical and preclinical studies have demonstrated that systemic lupus erythematosus (SLE) is associated with an increased risk for cardiovascular disease (CVD). However, unlike in the general population, little is known regarding the efficacy of atheroprotective interventions in patients with SLE. The current study aims to determine the benefit of lymphocyte inhibition on reducing the atherosclerotic burden in SLE-susceptible LDLr-deficient mice. METHODS: Female LDLr(-/-) mice were lethally irradiated and reconstituted with bone marrow from C57Bl/6 mice (LDLr.B6) or the SLE-susceptible B6.Sle1.2.3 mice (LDLr.Sle). At 16 weeks post transplant, mice were treated with atorvastatin (10 mg/kg), mycophenolate mofetil (MMF; 40 mg/kg), or both (MMF-A) for 8 weeks, after which the extent of atherosclerosis and the presence of SLE were assessed. RESULTS: Following 8 weeks of treatment, we observed that atorvastatin-mediated reduction in cholesterol levels attenuated atherogenesis in LDLr.B6 mice but failed to significantly reduce atherosclerotic lesion size in LDLr.Sle mice, in spite of a significant reduction in serum cholesterol levels. Treatment with MMF and MMF-A attenuated atherogenesis in LDLr.B6 and LDLr.Sle mice. In addition, MMF-containing regimens inhibited recruitment of CD4+ T cells to atherosclerotic lesions in LDLr.Sle mice. In these mice, MMF also reduced the proportion of activated splenic T cells, as well as interleukin 10 secretion by T cells. With regard to lupus activity, MMF had no overt effect on anti-double-stranded DNA (dsDNA) antibody titres or kidney function and pathology. CONCLUSIONS: The current study demonstrates that reduction of cholesterol levels alone is not atheroprotective in lupus-mediated atherogenesis. This is the first study to demonstrate that MMF reduces the atherosclerotic burden in a model of lupus-accelerated atherosclerosis. Our results suggest that MMF treatment may prove beneficial in preventing CVD in patients with SLE.

Role of the cholinergic nervous system in rheumatoid arthritis: aggravation of arthritis in nicotinic acetylcholine receptor α7 subunit gene knockout mice.

BACKGROUND: The alpha7 subunit of nicotinic acetylcholine receptors (alpha7nAChR) can negatively regulate the synthesis and release of proinflammatory cytokines by macrophages and fibroblast-like synoviocytes in vitro. In addition, stimulation of the alpha7nAChR can reduce the severity of arthritis in murine collagen-induced arthritis (CIA). OBJECTIVE: To provide more insight into the role of the alpha7nAChR in the pathogenesis of arthritis by investigating the effect of the absence of alpha7nAChR in CIA in alpha7-deficient (alpha7nAChR(-/-)) compared with wild-type (WT) mice. METHODS: CIA was induced in alpha7nAChR(-/-) and WT littermate mice at day 0 by immunisation with chicken collagen type II (cCII) followed by a booster injection with cCII on day 20. Mice were killed on day 44 or day 63 and arthritis activity as well as radiological and histological damage were scored. The effects on the immune response were evaluated by measurement of antigen-specific antibodies and cytokines, and evaluation of the effects on antigen-specific stimulated spleen cells. RESULTS: In alpha7nAChR(-/-) mice a significant increase in the incidence and severity of arthritis as well as increased synovial inflammation and joint destruction were seen. Exacerbation of CIA was associated with elevated systemic proinflammatory cytokines and enhanced T-helper cell 1 (Th1)-cytokine and tumour necrosis factor alpha production by spleen cells. Moreover, a specific decrease in the collagen-specific 'Th1-associated' IgG2a response was seen, whereas IgG1 titres were unaffected. CONCLUSIONS: The results presented here indicate that immune cell function in a model of rheumatoid arthritis is regulated by the cholinergic system and, at least in part, mediated by the alpha7nAChR.

How to perform and analyse synovial biopsies.

Although most of the rheumatologic diseases can be diagnosed based on clinical examination combined with additional laboratory and radiographic tests, histological examination of synovial tissue may lead to the correct diagnosis and adjustment of therapy when neoplastic or granulomatous disease, deposition disease, or infection in spite of negative synovial fluid culture is suspected. For research purposes synovial tissue analysis is used to investigate the pathological changes of the synovium in studies aimed at elucidating the etiology and pathogenetic mechanisms involved in arthritis. In addition, the use of synovial biomarkers has been shown to be instrumental in the developmental process of new therapeutics. In this chapter, several minimally invasive techniques for acquiring synovial tissue samples, handling of the tissue, and the analysis thereof are described.

In vitro spontaneous osteoclastogenesis of human peripheral blood mononuclear cells is not crucially dependent on T lymphocytes.

OBJECTIVE: In vitro spontaneous osteoclastogenesis from peripheral blood mononuclear cells (PBMCs) is increased in diseases with excessive bone loss. The purpose of this study was to reassess the role of T lymphocytes in this process. METHODS: Fresh or cryopreserved PBMCs obtained from healthy subjects and from patients with rheumatoid arthritis, psoriatic arthritis, and non-psoriatic spondylarthritis were cultured at high density and stained for tartrate-resistant acid phosphatase (TRAP). Resorption of mineralized matrix was assessed by a dentin disc assay. CD14+ monocytes and CD3+ T cells were selected using magnetically labeled antibodies. RESULTS: Numerous multinucleated, TRAP+, dentin-resorbing osteoclasts developed spontaneously from fresh PBMCs from healthy individuals. This process was abrogated by T cell depletion and was restored by exogenous macrophage colony-stimulating factor (M-CSF) and RANKL, indicating the important role of T cells in spontaneous osteoclastogenesis in vitro. Using physiologic freezing and thawing as a model for the activation of PBMCs, spontaneous osteoclastogenesis was significantly increased in cryopreserved versus fresh cells. Under these conditions, spontaneous osteoclastogenesis was not dependent on T lymphocytes, since it was not influenced by T cell depletion and persisted in purified CD14+ cell cultures supplemented with M-CSF and RANKL. In contrast to studies with fresh PBMCs, spontaneous osteoclastogenesis under these conditions did not appear to be clearly different between healthy subjects and patients with arthritis. CONCLUSION: Spontaneous osteoclastogenesis in vitro is dependent on T lymphocytes or on the direct activation of monocytic cells, depending on the test conditions. This variability warrants better validation of the relevance of this functional test for in vivo osteoclastogenesis.

Preclinical models of arthritic disease in non-human primates.

The costs for the development of new drugs have increased dramatically over the past 30 years. One of the main reasons for this increase is the low success rate of new drugs being approved for patient use, which is, in part, a consequence of the common use of rodent models for preclinical validation of efficacy. Especially in the development of biologicals, which are now successfully used in the treatment of rheumatoid arthritis, the selection of the right animal model is pivotal. Non-human primates could help to bridge the evolutionary gap between rodent models and human patients.