Deleting Suppressor of Cytokine Signaling-3 in chondrocytes reduces bone growth by disrupting mitogen-activated protein kinase signaling.

OBJECTIVE: To investigate the impact of deleting Suppressor of Cytokine Signaling (SOCS)-3 (SOCS3) in chondrocytes during murine skeletal development. METHOD: Mice with a conditional Socs3 allele (Socs3fl/fl) were crossed with a transgenic mouse expressing Cre recombinase under the control of the type II collagen promoter (Col2a1) to generate Socs3Δ/Δcol2 mice. Skeletal growth was analyzed over the lifespan of Socs3Δ/Δcol2 mice and controls by detailed histomorphology. Bone size and cortical bone development was evaluated by micro-computed tomography (micro-CT). Growth plate (GP) zone width, chondrocyte proliferation and apoptosis were assessed by immunofluorescence staining for Ki67 and TUNEL. Fibroblast growth factor receptor-3 (FGFR3) signaling in the GP was assessed by immunohistochemistry, while the effect of SOCS3 overexpression on FGFR3-driven pMAPK signaling in HEK293T cells was evaluated by Western blot. RESULTS: Socs3Δ/Δcol2 mice of both sexes were consistently smaller compared to littermate controls throughout life. This phenotype was due to reduced long bone size, poor cortical bone development, reduced Ki67+ proliferative chondrocytes and decreased proliferative zone (PZ) width in the GP. Expression of pMAPK, but not pSTAT3, was increased in the GPs of Socs3Δ/Δcol2 mice relative to littermate controls. Overexpression of FGFR3 in HEK293T cells increased Fibroblast Growth Factor 18 (FGF18)-dependent Mitogen-activated protein kinase (MAPK) phosphorylation, while concomitant expression of SOCS3 reduced FGFR3 expression and abrogated MAPK signaling. CONCLUSION: Our results suggest a potential role for SOCS3 in GP chondrocyte proliferation by regulating FGFR3-dependent MAPK signaling in response to FGF18.

Distinctive pro-inflammatory gene signatures induced in articular chondrocytes by oncostatin M and IL-6 are regulated by Suppressor of Cytokine Signaling-3.

OBJECTIVE: To describe gene expression in murine chondrocytes stimulated with IL-6 family cytokines and the impact of deleting Suppressor of Cytokine Signaling-3 (SOCS-3) in this cell type. METHOD: Primary chondrocytes were isolated from wild type and SOCS-3-deficient (Socs3(Δ/Δcol2)) mice and stimulated with oncostatin M (OSM), IL-6 plus the soluble IL-6 receptor (IL-6/sIL-6R), IL-11 or leukemia inhibitory factor (LIF) for 4 h. Total RNA was extracted and gene expression was evaluated by microarray analysis. Validation of the microarray results was performed using Taqman probes on RNA derived from chondrocytes stimulated for 1, 2, 4 or 8 h. Gene ontology was characterized using DAVID (database for annotation, visualization and integrated discovery). RESULTS: Multiple genes, including Bcl3, Junb, Tgm1, Angptl4 and Lrg1, were upregulated in chondrocytes stimulated with each gp130 cytokine. The gene transcription profile in response to OSM stimulation was pro-inflammatory and was highly correlated to IL-6/sIL-6R, rather than IL-11 or LIF. In the absence of SOCS-3, OSM and IL-6/sIL-6R stimulation induced an interferon (IFN)-like gene signature, including expression of IL-31ra and S100a9. CONCLUSION: While each gp130 cytokine induced a transcriptional response in chondrocytes, OSM- and IL-6/sIL-6R were the most potent members of this cytokine family. SOCS-3 plays an important regulatory role in this cell type, as it does in hematopoietic cells. Our results provide new insights into a hierarchy of gp130-induced transcriptional responses in chondrocytes that is normally restrained by SOCS-3 and suggest therapeutic inhibition of OSM may have benefit over and above antagonism of IL-6 during inflammatory arthritis.

Preclinical characterisation of the GM-CSF receptor as a therapeutic target in rheumatoid arthritis.

OBJECTIVE: Previous work has suggested that the granulocyte macrophage colony stimulating factor (GM-CSF)-GM-CSF receptor α axis (GM-CSFRα) may provide a new therapeutic target for the treatment of rheumatoid arthritis (RA). Therefore, we investigated the cellular expression of GM-CSFRα in RA synovial tissue and investigated the effects of anti-GM-CSFRα antibody treatment in vitro and in vivo in a preclinical model of RA. METHODS: We compared GM-CSFRα expression on macrophages positive for CD68 or CD163 on synovial biopsy samples from patients with RA or psoriatic arthritis (PsA) to disease controls. In addition, we studied the effects of CAM-3003, an anti-GM-CSFR antibody in a collagen induced arthritis model of RA in DBA/1 mice. The pharmacokinetic profile of CAM-3003 was studied in naïve CD1(ICR) mice (see online supplement) and used to interpret the results of the pharmacodynamic studies in BALB/c mice. RESULTS: GM-CSFRα was expressed by CD68 positive and CD163 positive macrophages in the synovium, and there was a significant increase in GM-CSFRα positive cells in patients in patients with RA as well as patients with PsA compared with patients with osteoarthritis and healthy controls. In the collagen induced arthritis model there was a dose dependent reduction of clinical arthritis scores and the number of F4/80 positive macrophages in the inflamed synovium after CAM-3003 treatment. In BALB/c mice CAM-3003 inhibited recombinant GM-CSF mediated margination of peripheral blood monocytes and neutrophils. CONCLUSIONS: The findings support the ongoing development of therapies aimed at interfering with GM-CSF or its receptor in various forms of arthritis, such as RA and PsA.

Arterial stiffness is increased in systemic sclerosis: a cross-sectional comparison with matched controls.

OBJECTIVES: Increased arterial stiffness is a predictor of cardiovascular and all-cause mortality. Atherosclerosis may be increased in systemic sclerosis (SSc). Our aims were to determine if arterial stiffness is elevated and to evaluate correlates of arterial stiffness in SSc. METHODS: We carried out two studies: 1. a comparison of arterial stiffness in 40 SSc patients free from cardiovascular disease or significant vascular manifestations of SSc and 40 healthy controls (HC), and 2. an analysis of determinants of arterial stiffness in 80 SSc patients free from cardiovascular disease. RESULTS: In Study 1, the groups were well-matched for age (52.2 vs. 50.0 years, p=0.432) and sex (80% female in both). SSc patients had higher augmentation index (AIx) than HC (31.0% [IQR 25.7-38.7] vs. 23.8% [IQR 13.5- 30.1], p<0.001). Pulse wave velocity (PWV) was also higher, however this did not reach statistical significance (6.9 m/s [IQR 6.0-8.3] vs. 6.5 m/s [IQR 6.1-7.4], p=0.275). In Study 2, age (p<0.001) and calcium channel blocker (CCB) therapy (p=0.016) were independently associated with higher AIx; and age (p<0.001), disease duration (p=0.042) and systolic blood pressure (p=0.001) with higher PWV. CONCLUSIONS: SSc patients had higher AIx than HC. The paradoxical association between CCB therapy and higher AIx could reflect generalised vasculopathy rather than atherosclerotic disease. Prospective studies in larger cohorts are warranted to clarify this point and elucidate other determinants of arterial stiffness in SSc.

Tumour necrosis factor antagonists improve disease activity but not arterial stiffness in rheumatoid arthritis.

OBJECTIVES: Systemic inflammation may play an important role in the accelerated atherosclerosis and increased cardiovascular mortality of rheumatoid arthritis (RA). Atorvastatin reduced arterial stiffness in RA patients after only 6 weeks, an effect that may be partially mediated by the immunomodulatory effects of this drug. Suppression of inflammation with tumour necrosis factor (TNF) antagonists may therefore also improve vascular function in RA; however, TNF antagonists have also been shown to cause or exacerbate congestive heart failure in patients with RA and heart failure. The aim of the present study was to examine the effect of treatment with TNF antagonists on arterial stiffness in RA patients with active disease. METHODS: Fourteen RA patients (age 55.1 +/- 3.8 yr; disease duration 7.9 +/- 1.3 yr) with high disease activity [disease activity score (DAS28) 7.1 +/- 0.3] commencing treatment with TNF antagonists for the first time were studied. Clinical status and arterial stiffness were measured before and after 6 weeks of TNF antagonist therapy (etanercept, adalimumab or infliximab). RESULTS: Arterial stiffness did not change during the study period (the mean augmentation index was 29.1 +/- 2.2% at baseline vs 30.1 +/- 1.8% at week 6; P = 0.504). The DAS28 improved significantly from 7.1 +/- 0.3 to 4.3 +/- 0.4 (P < 0.0001). The erythrocyte sedimentation rate and C-reactive protein [median (range)] were reduced from 44 (12-85) to 15 (3-82) mm/h (P = 0.02) and from 34 (3-95) to 10 (2-61) mg/l (P = 0.007), respectively. CONCLUSIONS: Despite significant reductions in synovitis and inflammatory markers in these RA patients, arterial stiffness was not improved by 6 weeks of treatment with TNF antagonists. This result is of relevance given recent reports of potential adverse cardiovascular effects of TNF antagonists in some RA patients.

Atorvastatin reduces arterial stiffness in patients with rheumatoid arthritis.

BACKGROUND: Chronic systemic inflammation may contribute to accelerated atherosclerosis and increased arterial stiffness in patients with rheumatoid arthritis (RA). In addition to lowering cholesterol, statins have immunomodulatory effects which may be especially beneficial in patients with RA who have systemic immune activation. OBJECTIVE: To investigate the effect of atorvastatin on the augmentation index (AIx: a measure of arterial stiffness) and systemic inflammation in RA. METHODS: 29 patients with RA (mean (SD) age 55 (13) years) with moderately active disease of long duration were studied. AIx, lipid levels, serum inflammatory markers, and disease activity score were measured before and after 12 weeks of atorvastatin 20 mg daily. RESULTS: AIx improved significantly from 34.1 (11.6)% to 29.9 (11)% (p = 0.0002), with the greatest improvements in AIx occurring in those subjects with the highest disease activity scores (r = -0.5, p = 0.007). Total and LDL cholesterol were reduced from 5.5 (0.9) to 3.9 (0.7) mmol/l and 3.3 (0.8) to 1.9 (0.6) mmol/l, respectively (p = 0.0001). Serum inflammatory markers remained unchanged during the study. CONCLUSIONS: Atorvastatin significantly reduced arterial stiffness in patients with RA. The greatest improvements were seen in patients with more active disease, suggesting that, in addition to the beneficial effects of cholesterol reduction, immune modulation may contribute to the cardioprotective effect of statins.

Screening for atherosclerosis in patients with rheumatoid arthritis: comparison of two in vivo tests of vascular function.

OBJECTIVE: Inflammation appears to play a central role in atherosclerosis, and endothelial damage mediated by systemic inflammation may contribute to the increased cardiovascular mortality in rheumatoid arthritis (RA). Brachial artery flow-mediated dilatation (FMD) and pulse wave analysis (PWA) are measures of vascular function. The aim of this study was to determine if FMD and PWA are abnormal in patients with RA. METHODS: Twenty-five RA patients and 25 matched healthy controls were studied. All were free of traditional cardiovascular risk factors. FMD was measured in all subjects. PWA was performed in 18 RA patients and 18 controls, with results expressed as large and small artery compliance (C1 and C2). Modified Sharp scores were calculated in 13 RA patients. RESULTS: Results (mean +/- SD) in RA patients and controls, respectively, were as follows: FMD 107.6 +/- 4.6% versus 108.5 +/- 4.1% (P = 0.49), C1 14.8 +/- 2.8 ml/mm Hg x 10 versus 17.9 +/- 3.1 ml/mm Hg x 10 (P = 0.0033), C2 4.5 +/- 2.3 ml/mm Hg x 100 versus 7.7 +/- 3.7 ml/mm Hg x 100 (P = 0.0039). There was an inverse correlation between C2 and modified Sharp scores in the RA patients (Spearman's rho -0.69, P = 0.0085). CONCLUSION: FMD was normal in these RA patients, whereas arterial compliance was markedly reduced. PWA appears to be a more sensitive measure of vascular dysfunction than FMD in RA and may be the preferred surrogate marker of vascular dysfunction in longitudinal studies of RA patients. The inverse correlation between C2 and the modified Sharp score, a measure that reflects disease activity over time, supports the notion that chronic inflammation plays a role in RA-associated atherosclerosis.

Vascular cell adhesion molecule-1 (VCAM-1) blockade in collagen-induced arthritis reduces joint involvement and alters B cell trafficking.

Vascular cell adhesion molecule-1 (VCAM-1 or CD106) is important in leucocyte trafficking and its increased expression is associated with a number of chronic inflammatory diseases, including rheumatoid arthritis (RA). We used a neutralizing monoclonal antibody (M/K-2.7) to investigate the role of VCAM-1 in collagen-induced arthritis (CIA), an autoimmune model of RA. A single injection of M/K-2.7 (0.5 mg) into naive mice caused leucocytosis within 20 h, due to increased numbers of circulating B cells and macrophages, as well as neutrophils. The most marked effect was on the numbers of immature B cells (B220loIgM+) which were increased approximately fourfold. CIA was elicited in DBA/1 mice by immunization with chick type II collagen (CII) in Freund's complete adjuvant, followed by a repeat injection 21 days later. Repeated M/K-2.7 administration from the time of primary CII immunization reduced the clinical severity, but not the incidence, of CIA compared to isotype-control monoclonal antibody-treated mice. Histological assessment showed fewer arthritic joints in M/K-2.7-treated mice; however, affected joints showed the same range of severity as those of control mice. Anti-CII IgG1 levels were reduced in anti-VCAM-1-treated mice but the cellular immune response to CII was unaffected. In contrast, VCAM-1 blockade from the onset of clinical features of CIA did not prevent disease progression. These results establish a role for VCAM-1 in promoting polyarticular involvement in CIA, most probably via an effect on B cells.

Characterization of a human synovial cell antigen: VCAM-1 and inflammatory arthritis.

The contribution of synovial cells to the pathogenesis of rheumatoid arthritis (RA) is only partly understood. Monoclonal antibody (mAb) 1D5 is one of very few mAb ever raised against RA synovial cells in order to study the biology of these cells. Studies on the expression pattern and structural features of the 1D5 Ag suggest that 1D5 recognizes human vascular cell adhesion molecule-1 (VCAM-1), which is an intercellular adhesion molecule. Vascular cell adhesion molecule-1 may be involved in a number of crucial intercellular interactions in RA.

Defective gp130-mediated signal transducer and activator of transcription (STAT) signaling results in degenerative joint disease, gastrointestinal ulceration, and failure of uterine implantation.

The receptor subunit gp130 transduces multiple cell type-specific activities of the leukemia inhibitory factor (LIF)/interleukin (IL)-6 family of cytokines through the signal transducer and activator of transcription (STAT) and src homology 2 domain-bearing protein tyrosine phosphatase (SHP)-2/ras/Erk pathways. To define STAT-dependent physiological responses, we generated mice with a COOH-terminal gp130(DeltaSTAT) "knock-in" mutation which deleted all STAT-binding sites. gp130(DeltaSTAT) mice phenocopyed mice deficient for IL-6 (impaired humoral and mucosal immune and hepatic acute phase responses) and LIF (failure of blastocyst implantation). However, unlike mice with null mutations in any of the components in the gp130 signaling pathway, gp130(DeltaSTAT) mice also displayed gastrointestinal ulceration and a severe joint disease with features of chronic synovitis, cartilaginous metaplasia, and degradation of the articular cartilage. Mitogenic hyperresponsiveness of synovial cells to the LIF/IL-6 family of cyto-kines was caused by sustained gp130-mediated SHP-2/ras/Erk activation due to impaired STAT-mediated induction of suppressor of cytokine signaling (SOCS) proteins which normally limits gp130 signaling. Therefore, the joint pathology in gp130(DeltaSTAT) mice is likely to arise from the disturbance of the otherwise balanced activation of the SHP-2/ras/Erk and STAT signaling cascades emanating from gp130.

Severe inflammatory arthritis and lymphadenopathy in the absence of TNF.

It has been postulated that TNF has a pivotal role in a cytokine cascade that results in joint inflammation and destruction in rheumatoid arthritis (RA). To evaluate this, we examined the response of TNF-deficient (Tnf(-/-)) mice in two models of RA. Collagen-induced arthritis (CIA) was induced by injection of chick type II collagen (CII) in CFA. Tnf(-/-) mice had some reduction in the clinical parameters of CIA and, on histology, significantly more normal joints. However, severe disease was evident in 54% of arthritic Tnf(-/-) joints. Tnf(-/-) mice had impaired Ig class switching, but preserved T cell proliferative responses to CII and enhanced IFN-gamma production. Interestingly, CII-immunized Tnf(-/-) mice developed lymphadenopathy and splenomegaly associated with increased memory CD4(+) T cells and activated lymph node B cells. Acute inflammatory arthritis was also reduced in Tnf(-/-) mice, although again some mice exhibited severe disease. We conclude that TNF is important but not essential for inflammatory arthritis; in each model, severe arthritis could proceed even in the complete absence of TNF. These results call into doubt the concept that TNF is obligatory for chronic autoimmune and acute inflammatory arthritis and provide a rationale for further studies into TNF-independent cytokine pathways in arthritis.

Molecular and cellular mediators of interleukin-1-dependent acute inflammatory arthritis.

OBJECTIVE: To examine the molecular and cellular mechanisms in a model of acute inflammatory monarticular arthritis induced by methylated bovine serum albumin (mBSA) and interleukin-1 (IL-1). METHODS: Mice were injected intraarticularly with mBSA on day 0 and subcutaneously with recombinant human IL-1beta on days 0-2. At day 7, knee joints were removed and assessed histologically. Flow cytometry and RNase protection were used to analyze IL-1-dependent events. RESULTS: C57BL/6 (B6), 129/Sv, and (B6 x 129/ Sv)F1 hybrid mice, all H-2b strains, were susceptible to mBSA/IL-1-induced arthritis, whereas C3H/HeJ (H-2k) mice were not. B6 mice lacking T and B cells (RAG1-/-) or major histocompatibility complex (MHC) class II antigens (MHCII-/-), and B6 mice treated with a CD4+ T cell-depleting monoclonal antibody, were resistant to disease. In contrast, B cell-deficient (muMT/ muMT) mice developed arthritis at an incidence and severity similar to that of controls. RelB-deficient (RelB-/-) bone marrow chimeric mice had arthritis that was significantly reduced in incidence and severity. In B6 mice, flow cytometry demonstrated an IL-1-dependent leukocyte infiltration into the synovial compartment and RNase protection assays revealed induction of messenger RNA (mRNA) for the chemokines monocyte chemoattractant protein 1, macrophage inhibitory protein 2 (MIP-2), RANTES, MIP-1alpha, and MIP-1beta, in vivo and in vitro. CONCLUSION: Arthritis induced by mBSA/IL-1 is strain specific and dependent on CD4+ T lymphocytes and at least partially on RelB, but not on B lymphocytes or antibody. IL-1 contributes to leukocyte recruitment to the synovium and directly induces chemokine mRNA production by synovial cells. This model of acute monarticular arthritis is particularly suitable for further investigations into cell-mediated immunity in arthritis and the role of IL-1.

Prolonged prodrome, systemic vasculitis, and deafness in Cogan's syndrome.

Cogan's syndrome is a rare, multisystem disease which occurs predominantly in children and young adults. It was originally described as the combination of interstitial keratitis and audiovestibular disturbance, but other forms of ocular disease, as well as systemic vasculitis, have since been recognised as part of the syndrome. Diagnosis can be difficult if the various manifestations occur separately, but early recognition is important because prompt treatment may prevent deafness. Two cases are presented here illustrating the features of this disease, and providing histological evidence of systemic vasculitis in both.

Collagen-induced arthritis in C57BL/6 (H-2b) mice: new insights into an important disease model of rheumatoid arthritis.

Collagen-induced arthritis (CIA) is a widely used model of rheumatoid arthritis (RA) and has been important for understanding autoimmunity. CIA is purportedly restricted to mice bearing the MHC class II H-2q or H-2r haplotypes. In this study, we re-examined established concepts regarding susceptibility to CIA. We found mice derived from the C57BU6 (B6) (H-2b) background can develop CIA with high incidence (60-70%), and sustained severity by using an immunization procedure modified for optimum response in DBA/1 (D1) (H-2q) mice. Clinically and histologically the B6 disease resembles that of D1 mice and is dependent on immunization with type II collagen, as well as on B and CD4+ T cells. In contrast, 129/Sv mice, which share H-2b, are resistant to CIA. We conclude that susceptibility to CIA may reflect immunization conditions and/or important contributions from non-MHC genes, revealed by different immunization protocols. A practical outcome is that CIA can be directly applied to gene knockout mice generated from B6 embryonic stem cells without need for backcross onto the D1 background. This model may lead to improved understanding of autoimmunity in CIA and RA and may provide a platform for analysis of the contribution of non-MHC genes to CIA.

Distinct roles for the NF-kappaB1 (p50) and c-Rel transcription factors in inflammatory arthritis.

Rheumatoid arthritis (RA) is a complex disease, with contributions from systemic autoimmunity and local inflammation. Persistent synovial joint inflammation and invasive synovial pannus tissue lead to joint destruction. RA is characterized by the production of inflammatory mediators, many of which are regulated by the Rel/NF-kappaB transcription factors. Although an attractive target for therapeutic intervention in inflammatory diseases, Rel/NF-kappaB is involved in normal physiology, thus global inhibition could be harmful. An alternate approach is to identify and target the Rel/NF-kappaB subunits critical for components of disease. To assess this, mice with null mutations in c-rel or nfkb1 were used to examine directly the roles of c-Rel and p50 in models of acute and chronic inflammatory arthritis. We found c-Rel-deficient mice were resistant to collagen-induced arthritis but had a normal response in an acute, destructive arthritis model (methylated BSA/IL-1 induced arthritis) suggesting c-Rel is required for systemic but not local joint disease. In contrast, p50-deficient mice were refractory to induction of both the chronic and acute arthritis models, showing this subunit is essential for local joint inflammation and destruction. Our data suggest Rel/NF-kappaB subunits play distinct roles in the pathogenesis of inflammatory arthritis and may provide a rationale for more specific therapeutic blockade of Rel/NF-kappaB in RA.

Targeted insertion of a lacZ reporter gene into the mouse Cer1 locus reveals complex and dynamic expression during embryogenesis.

The mouse Cer1 (mCer1, Cer-l, Cerr1) gene encodes one member of a family of cytokines structurally and functionally related to the Xenopus head-inducing factor, Cerberus (xCer). We generated a mouse line in which the Cer1 gene was inactivated by replacing the first coding exon with a lacZ reporter gene. Mice homozygous for this allele (Cer1(lacZ)) showed no apparent perturbation of embryogenesis or later development. However, the lacZ reporter revealed a number of hitherto uncharacterised sites of Cer1 expression in late fetal and adult tissues. Preliminary analysis suggests that Cer1 is not essential for their morphogenesis, differentiation, or homeostasis.