sRANKL and OPG in serum and synovial fluid of patients with rheumatoid arthritis in comparison to non-destructive chronic arthritis

A Clinical Study Evaluating the Effects of Fluvastatin on Serum Osteoprotegerin Levels in Rheumatoid Arthritis Patients

Osteoprotegerin (OPG), a member of the tumor necrosis factor receptor family, has been identified as a critical regulator of bone resorption. Considering the possible role of OPG in rheumatoid arthritis (RA) and in the osteoclastogenesis suppression effects of statins, the present study aims to investigate the effects of fluvastatin on serum levels OPG and disease activity score (DAS) in patients with RA. Forty patients with RA were randomized in a placebo-controlled trial to receive 40 mg fluvastatin or placebo as an adjunct to existing disease-modifying antirheumatic drug (DMARD) therapy (methotrexate, leflunomide, hydroxychloroquine). Patients were followed up over 12 weeks. OPG and disease activity variables were measured at baseline and after 12 weeks of treatment. After 12 weeks, the OPG level was significantly increased in the fluvastatin group compared to the placebo group. DAS-28 was significantly decreased in the fluvastatin group compared to the placebo group. C-reactive protein (CRP), morning stiffness, swollen joint count (SJC), and tender joint count (TJC) were significantly decreased in the fluvastatin group compared to the placebo group; however, erythrocyte sedimentation rate (ESR), modified health assessment questionnaire (MHAQ), and visual analogue screen (VAS) were not changed significantly. In conclusion, fluvastatin administration could increase the OPG levels and improve disease activity variables in patients with RA. Therefore, fluvastatin may serve a potential benefit in the treatment of RA patients.

Path Analysis Identifies Receptor Activator of Nuclear Factor-κB Ligand, Osteoprotegerin, and Sclerostin as Potential Mediators of the Tophus-bone Erosion Relationship in Gout

OBJECTIVE

To determine the relationship between tophus, erosion and bone remodeling factors in gout.

METHODS

Computed tomography bone erosion and circulating bone factors were measured in adults with tophaceous gout. Multiple regression modeling and path analysis were used to determine predictors of erosion.

RESULTS

Tophus number, Māori or Pacific ethnicity, creatinine, receptor activator of nuclear factor-κB ligand (RANKL), osteoprotegerin (OPG), and sclerostin were independently associated with erosion. Path analysis showed a direct effect of tophus number on erosion, partially mediated through OPG, RANKL, and sclerostin.

CONCLUSION

Tophus number is strongly associated with bone erosion in gout. Circulating RANKL, OPG, and sclerostin are potential mediators of tophus-related erosion.

Serum sclerostin in high-activity adult patients with juvenile idiopathic arthritis

Introduction

Juvenile idiopathic arthritis (JIA) is a disease associated with loss of bone mass, deterioration in bone mass quality and an increased risk of fractures. The objective of this study was to evaluate factors that predict bone mineral density (BMD) alterations in young adult patients with active JIA before and during therapy with tumour necrosis factor α (TNFα) inhibitors.

Methods

Thirty-one patients (twelve males and nineteen females; mean age =25.1 ± 6.1 years) with active JIA (mean Disease Activity Score in 28 joints (DAS28) =6.36 ± 0.64; mean high-sensitivity C-reactive protein (hsCRP) =18.36 ± 16.95 mg/L) were investigated. The control group consisted of 84 healthy individuals matched by sex and age. BMD, bone turnover markers and serum concentrations of soluble receptor activator of nuclear factor κB ligand, osteoprotegerin, dickkopf Wnt signalling pathway inhibitor 1 (Dkk1) and sclerostin were evaluated.

Results

Baseline BMD values in the lumbar spine, proximal femur, femoral neck and distal radius were significantly lower in patients with JIA compared to healthy control participants. Baseline sclerostin serum concentrations were significantly higher in patients with JIA compared to control participants. After 2 years of treatment with TNFα inhibitors, BMD was significantly increased in the lumbar spine. This increase correlated with a drop in DAS28 score. A statistically significant correlation between hsCRP and Dkk1 was found at baseline, as well as during the 2-year follow-up period. A significant reduction in serum sclerostin after 1 year of therapy was predictive of a drop in DAS28 score observed with a 1-year delay after reduction of serum sclerostin.

Conclusion

A significant correlation between the sclerostin serum concentration and the number of tender and swollen joints, but not BMD, supports the hypothesis that chondrocytes and cells of the subchondral bone may contribute to circulating sclerostin in JIA.

Chronic low dose tumor necrosis factor-α (TNF) suppresses early bone accrual in young mice by inhibiting osteoblasts without affecting osteoclasts

The inflammatory cytokine tumor necrosis factor-α (TNF-α) is known to cause bone resorption and inhibit bone formation in arthritis and aging but less is known about TNF effects in the young growing skeleton. While investigating the mechanism of bone loss in TNF transgenic mice, we identified an early TNF-sensitive period marked by suppression of osteoblasts and bone accrual as the sole mechanism of TNF action, without an effect on osteoclasts or bone resorption. TgTNF mice express low concentrations of hTNFα (≤5 pg/ml). Osteoblasts cultured from TgTNF mice express reduced levels of RUNX2, Osx, alkaline phosphatase, bone sialoprotein, and osteocalcin and have delayed formation of mineralized nodules. Early accrual of bone in TgTNF mice is suppressed until 6 weeks of age, after which the rate of bone accrual normalizes without catch up. Histomorphometry revealed that TgTNF mice fail to generate a transient surge in osteoblast number that is seen in wild type (WT) mice at 4 weeks. Osteoclasts, TRAP staining, erosive surfaces, serum CTx, and OPG/RANKL expression did not differ between young TgTNF and WT mice. Canonical Wnts and signaling through β-catenin were reduced in TgTNF mice at 4 weeks and partially recovered by 12 weeks, associated with reduced cytoplasm to nuclear transfer of β-catenin and Wnt regulated genes. TgTNF mice were crossed with BatGal Wnt reporter mice. Active Wnt signaling in tibial trabecular lining cells was reduced in TgTNF mice at 4 weeks compared to control littermates. Our results demonstrate that a low dose inflammatory stimulus is sufficient to inhibit the early surge in osteoblasts and optimal bone formation of young mice independent of changes in osteoclasts. TNF inhibition of the Wnt pathway contributes to the suppression of osteoblasts.

A significant association exists between receptor tyrosine kinase-like orphan receptor 2 gene variants and the OPG/RANKL ratio in human plasma

SUMMARY

There is a paucity of studies investigating association between ROR2 gene variants and osteoporosis and osteoarthritis-related phenotypes. The published literature suggests that osteoprotegerin (OPG) and receptor activator of nuclear factor-kB ligand (RANKL) are essential for bone metabolism and correlate with osteoarthritis manifestation and progression. The present study provides evidence of the significant association between ROR2 variants and the OPG/RANKL ratio in human plasma. The present results also suggest significant association between ROR2 polymorphisms and severity of radiographic hand osteoarthritis.

INTRODUCTION

Despite the importance of the ROR-2 in skeletal physiology, there is a paucity of studies investigating the potential association of ROR2 gene variants with phenotypes relevant to osteoporosis and osteoarthritis. On the other hand, there is a considerable body of literature suggesting that OPG and RANKL and their ratio (OPG/RANKL) are essential for regulating bone resorption. This is also correlated with osteoarthritis manifestation and progression. The present study therefore examines whether ROR2 polymorphisms may be associated with the OPG/RANKL ratio and hand osteoarthritis (HOA).

METHODS

The study was conducted in a family-based sample of 1,515 Caucasian individuals, assessed for radiographic hand osteoarthritis, using the Kellgren/Lawrence score. Of these, 865 individuals were genotyped for 19 SNPs, relatively equally covering the ROR2 locus, and their plasma levels of OPG and RANKL were assayed. The association between the selected SNPs and OPG, along with the OPG/RANKL ratio and HOA, was explored using the pedigree disequilibrium test.

RESULTS

Of the total of 57 tests, 16 nominally significant results (p < 0.05) were obtained, which is considerably more than the three normally expected for type I error. The significant association signals for all three phenotypes were mapped to the intron 1 region. The most significant results were detected between OPG/RANKL and rs7048756 (p < 0.0005) and between adjacent rs4744107 and Kellgren/Lawrence score (p = 0.006).

CONCLUSIONS

The present study provides evidence of the significant association between ROR2 variants and the OPG/RANKL ratio in human plasma and also suggests ROR2 association with HOA.

A functional RANKL polymorphism associated with younger age at onset of rheumatoid arthritis

OBJECTIVE

We previously observed the association of the co-occurrence of the HLA-DRB1 shared epitope (SE) and RANKL single-nucleotide polymorphisms (SNPs) with younger age at the onset of rheumatoid arthritis (RA) in 182 rheumatoid factor (RF)-positive European American patients with early-onset RA. The aim of this study was to fine-map the 48-kb RANKL region in the extended cohort of 210 European American RF-positive patients with early RA, to seek replication of RA-associated SNPs in additional RA cohorts of 501 European Americans and 298 African Americans, and to explore the functional consequences of RA-associated SNPs.

METHODS

SNP genotyping was conducted using pyrosequencing or TaqMan polymerase chain reaction (PCR) assays. Associations of rs7984870 with RANKL expression in plasma, peripheral blood mononuclear cells, and isolated T cells were quantified using enzyme-linked immunosorbent assay and reverse transcription-PCR. Site-directed mutagenesis of rs7984870 within the 2-kb RANKL promoter was performed to drive the luciferase reporter gene in osteoblast and stromal cell lines. Interaction of DNA and protein was determined by electrophoretic mobility shift assay.

RESULTS

A single promoter SNP, rs7984870, was consistently significantly associated with earlier age at the onset of RA in 3 independent seropositive (RF or anti-cyclic citrullinated peptide antibody) RA cohorts but not in seronegative RA patients. The C risk allele of rs7984870 conferred 2-fold higher plasma RANKL levels in RF-positive patients with RA, significantly elevated RANKL messenger RNA expression in activated normal T cells, and increased promoter activity after stimulation in vitro via differential binding to the transcription factor SOX5.

CONCLUSION

The RANKL promoter allele that increased transcription levels upon stimulation might promote interaction between activated T cells and dendritic cells, predisposing to a younger age at the onset of RA in seropositive European American and African American patients.

Dickkopf-1 as potential biomarker to evaluate bone erosion in systemic lupus erythematosus

OBJECTIVE

This study aims to explore the potential role of circulating Dickkopf-1 (Dkk-1) and osteoprotegerin (OPG) in evaluating erosive arthritis in systemic lupus erythematosus (SLE).

METHODS

Serum Dkk-1 and OPG levels were examined in 130 SLE patients including eight with erosive arthritis, 100 rheumatoid arthritis (RA) patients and 50 healthy individuals by ELISA. Comparison of serum Dkk-1 levels with presence of anti-cyclic citrullinated peptides (CCP) antibodies in evaluating erosive arthritis in SLE was carried out. Associations of Dkk-1 and OPG levels with results of clinical examination were also noted.

RESULTS

Dkk-1 levels were significantly increased in eight SLE patients with erosive arthritis, compared to 58 SLE patients with non-erosive arthritis, 64 SLE patients without arthritis, and healthy controls, while similar with RA. In contrast, no significant changes of OPG levels were found except for higher levels in RA. No differences were found in Dkk-1 levels of SLE patients with erosive arthritis subdivided according to presence or absence of anti-CCP antibodies. Moreover, higher levels of Dkk-1 were identified in anti-CCP positive SLE patients with erosive arthritis compared to those with non-erosive arthritis or without arthritis. However, no significant correlations between Dkk-1 and OPG levels or between Dkk-1 levels and other laboratory and clinical manifestations were observed.

CONCLUSIONS

High levels of circulating Dkk-1 were associated with bone erosion in patients with SLE, even when anti-CCP antibodies were absent.

Baseline Serum Concentrations of TRAIL in Early Rheumatoid Arthritis: Relationship with Response to Disease-modifying Antirheumatic Drugs

Objective.

To assess the relationship between serum concentrations of tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and osteoprotegerin (OPG) and the therapeutic response to disease-modifying antirheumatic drugs (DMARD) in patients with early rheumatoid arthritis (RA).

Methods.

Circulating levels of TRAIL and its soluble receptor OPG were measured by ELISA in paired serum samples obtained from 66 patients with early RA at their first visit (baseline) and after 1 year of therapy. Levels of TRAIL and OPG were analyzed in relation to the clinical response, defined by the 28-joint count Disease Activity Score (DAS28).

Results.

Both serum TRAIL and OPG increased after DMARD therapy. Baseline levels of TRAIL, but not OPG, were significantly higher (p < 0.05) in the patients that achieved a clinical response by DAS28 after 1 year of therapy, versus patients without clinical response to DMARD. Baseline serum levels of TRAIL were higher (p < 0.01) in rheumatoid factor-negative patients.

Conclusion.

Our data suggest that the basal level of circulating TRAIL is an important determinant in the therapeutic response to DMARD in patients with early RA.

Relationships among serum receptor of nuclear factor-kappaB ligand, osteoprotegerin, high-sensitivity C-reactive protein, and bone mineral density in postmenopausal women: osteoimmunity versus osteoinflammatory

OBJECTIVE

The aim of this study was to investigate the correlations among circulating osteoprotegerin (OPG), the receptor activator of nuclear factor-kappaB ligand (RANKL), high-sensitivity C-reactive protein (hsCRP), and bone mineral density (BMD) in healthy postmenopausal women.

METHODS

In a population-based study, highly specific enzyme-linked immunosorbent assay methods were used to evaluate the sera of 382 healthy Iranian postmenopausal women (mean age +/- SD, 58.7 +/- 7.5 y) for RANKL, OPG, hsCRP, degradation products of C-terminal telopeptides of type I collagen, and osteocalcin. BMD was determined for the lumbar spine (L2-L4) and the proximal femur using dual-energy x-ray absorptiometry.

RESULTS

Circulating levels of OPG (r = 0.30, P < 0.001) and the RANKL/OPG ratio (r = -0.17, P < 0.001) were significantly associated with age. The geometric mean of hsCRP was 1.89 mg/L (SE, 1.05) in the population studied. There was a significant correlation between log(hsCRP) levels and body mass index (BMI; r = 0.36, P < 0.001). Multivariate linear analyses revealed that age (beta = -0.295, P < 0.001), BMI (beta = 0.464, P < 0.001), RANKL (beta = -0.105, P = 0.014), and OPG (beta = 0.098, P = 0.029) were the independent determinants for lumbar BMD (R(2) = 0.35). Age (beta = -0.250, P < 0.001), BMI (beta = 0.486, P < 0.001), and RANKL (beta = -0.110, P = 0.009) were independently correlated with femoral neck BMD (R(2) = 0.36). Age- and BMI-adjusted analysis by quartiles of log-transformed hsCRP did not reveal an association with BMD, serum levels of biochemical markers of bone turnover, RANKL, or OPG.

CONCLUSIONS

The circulating levels of the RANKL/OPG osteoimmunity system have an association with BMD, but subclinical systemic inflammation may not be involved in bone mass in healthy postmenopausal women.

The soluble terminal complement complex (SC5b-9) up-regulates osteoprotegerin expression and release by endothelial cells: implications in rheumatoid arthritis

OBJECTIVE

Complement activation products contribute to a large number of inflammatory diseases, including RA. We have investigated whether osteoprotegerin (OPG) may concur with the soluble terminal complement complex (SC5b-9) to the inflammatory cascade characterizing RA.

METHODS

Levels of SC5b-9 and OPG in the plasma and SF of patients with active RA were determined by ELISA. The presence of SC5b-9 and OPG in RA synovial lesions was analysed by immunohistochemistry. Cultured endothelial cells were used for in vitro leucocyte/endothelial cell adhesion assays. In addition, endothelial cells were exposed to SC5b-9 in order to evaluate the effects on the production of OPG protein, as well as the activation of the OPG promoter.

RESULTS

Patients affected by active RA are characterized by elevated levels of both SC5b-9 and OPG in plasma and/or SF. Of note, we have observed a co-localization of SC5b-9 and OPG in endothelial cells of post-capillary venules of RA synovial lesions. Data on endothelial cell cultures showed that exposure to SC5b-9 induced the up-regulation of OPG expression/release, stimulating the transcriptional activity of the OPG promoter, and synergized with TNF-alpha in up-regulating OPG production.

CONCLUSIONS

Our findings demonstrate that SC5b-9 induces OPG production by endothelial cells and we propose that the SC5b-9-mediated up-regulation of OPG may be an important mechanism whereby complement contributes in promoting and/or enhancing the inflammation in RA.

Cytokine-controlled RANKL and osteoprotegerin expression by human and mouse synovial fibroblasts: fibroblast-mediated pathologic bone resorption

OBJECTIVE

To determine whether proinflammatory cytokine treatment or the complete absence of select cytokines modulates the expression of RANKL and osteoprotegerin (OPG) in synovial fibroblasts.

METHODS

Fibroblasts were isolated from normal and rheumatoid human synovium and from normal or arthritic joints of wild-type and cytokine gene-deficient (interleukin-4-knockout [IL-4 (-/-)] and interferon-gamma-knockout [IFNgamma (-/-)]) mice. Fibroblasts were stimulated with proinflammatory cytokines (tumor necrosis factor alpha [TNFalpha], IL-1beta, and IL-17) or antiosteoclastogenic cytokines (IL-4 and IFNgamma), alone or in combination, and the expression of RANKL and OPG was measured.

RESULTS

Proinflammatory cytokine-stimulated fibroblasts from rheumatoid and arthritic mouse joints expressed higher levels of RANKL and OPG than those from normal joints. IL-4 suppressed RANKL expression and increased OPG expression, IFNgamma reduced the production of both RANKL and OPG, and IL-17 had only a modest effect on the expression of RANKL or OPG. Additive effects of combination treatment (TNFalpha/IL-17 or IL-1beta/IL-17) were observed only in the human system. Extensive destruction was observed in the arthritic joints of IL-4 (-/-) mice, with a corresponding upward shift of the RANKL:OPG ratios. However, an IL-17 deficiency did not attenuate arthritis or reduce bone resorption.

CONCLUSION

Proinflammatory cytokines induce the expression of RANKL and OPG in both human and murine synovial fibroblasts. The RANKL:OPG ratios are shifted in favor of bone protection by IL-4 treatment, and, to a lesser extent, by IFNgamma treatment. Unexpectedly, an IL-17 deficiency alone does not induce reduced inflammatory bone destruction. Our results suggest that synovial fibroblasts may significantly contribute to bone resorption through modulation of RANKL and OPG production in a cytokine-rich milieu of inflamed joints.