Effect of tumour necrosis factor-α inhibitor on serum level of dickkopf-1 protein and bone morphogenetic protein-7 in ankylosing spondylitis patients with high disease activity

DKK-1 and Its Influences on Bone Destruction: A Comparative Study in Collagen-Induced Arthritis Mice and Rheumatoid Arthritis Patients

Dickkopf-1 (DKK-1) has been considered a master regulator of bone remodeling. As precursors of osteoclasts (OCs), myeloid-derived suppressor cells (MDSCs) were previously shown to participate in the process of bone destruction in rheumatoid arthritis (RA). However, the role of DKK-1 and MDSCs in RA is not yet fully understood. We investigated the relevance between the level of DKK-1 and the expression of MDSCs in different tissues and joint destruction in RA patients and collagen-induced arthritis (CIA) mouse models. Furthermore, the CIA mice were administered recombinant DKK-1 protein. The arthritis scores, bone destruction, and the percentage of MDSCs in the peripheral blood and spleen were monitored. In vitro, the differentiation of MDSCs into OCs was intervened with recombinant protein and inhibitor of DKK-1. The number of OCs differentiated and the protein expression of the Wnt/β-catenin signaling pathway were explored. The level of DKK-1 positively correlates with the frequency of MDSCs and bone erosion in RA patients and CIA mice. Strikingly, recombinant DKK-1 intervention significantly exacerbated arthritis scores and bone destruction, increasing the percentage of MDSCs in the peripheral blood and spleen in CIA mice. In vitro experiments showed that recombinant DKK-1 promoted the differentiation of MDSCs into OCs, reducing the expression of β-catenin and TCF4 and increasing the expression of CyclinD1. In contrast, the DKK-1 inhibitor had the opposite effect. Our findings highlight that DKK-1 promoted MDSCs expansion in RA and enhanced the differentiation of MDSCs into OCs via targeting the Wnt/β-catenin pathway, aggravating the bone destruction in RA.

Osteoimmunology of Spondyloarthritis

The mechanisms underlying the development of bone damage in the context of spondyloarthritis (SpA) are not completely understood. To date, a considerable amount of evidence indicates that several developmental pathways are crucially involved in osteoimmunology. The present review explores the biological mechanisms underlying the relationship between inflammatory dysregulation, structural progression, and osteoporosis in this diverse family of conditions. We summarize the current knowledge of bone biology and balance and the foundations of bone regulation, including bone morphogenetic protein, the Wnt pathway, and Hedgehog signaling, as well as the role of cytokines in the development of bone damage in SpA. Other areas surveyed include the pathobiology of bone damage and systemic bone loss (osteoporosis) in SpA and the effects of pharmacological treatment on focal bone damage. Lastly, we present data relative to a survey of bone metabolic assessment in SpA from Italian bone specialist rheumatology centers. The results confirm that most of the attention to bone health is given to postmenopausal subjects and that the aspect of metabolic bone health may still be underrepresented. In our opinion, it may be the time for a call to action to increase the interest in and focus on the diagnosis and management of SpA.

The Role of Sclerostin in Rheumatic Diseases: A Review

Systemic connective tissue disorders constitute a heterogenous group of autoimmune diseases with the potential to affect a range of organs. Rheumatoid arthritis (RA) is a chronic, progressive, autoimmune inflammatory disease affecting the joints. Systemic lupus erythematosus (SLE) may manifest with multiple system involvement as a result of inflammatory response to autoantibodies. Spondyloarthropathies (SpAs) such as ankylosing spondylitis (AS) or psoriatic arthritis (PsA) are diseases characterised by the inflammation of spinal joints, paraspinal tissues, peripheral joints and enthesitis as well as inflammatory changes in many other systems and organs. Physiologically, sclerostin helps to maintain balance in bone tissue metabolism through the Wnt/β-catenin pathway, which represents a major intracellular signalling pathway. This review article aims to present the current knowledge on the role of sclerostin in the Wnt/β-catenin pathway and its correlation with clinical data from RA, SLE, AS and PsA patients.

Complexity of enthesitis and new bone formation in ankylosing spondylitis: current understanding of the immunopathology and therapeutic approaches

Despite increasing availability of treatments for spondyloarthritis (SpA) including tumour necrosis factor (TNF) and interleukin-17 (IL-17) inhibitors, there is no established treatment that abates new bone formation (NBF) in ankylosing spondylitis (AS), a subset of SpA. Recent research on TNF has revealed the increased level of transmembrane TNF in the joint tissue of SpA patients compared to that of rheumatoid arthritis patients, which appears to facilitate TNF-driven osteo-proliferative changes in AS. In addition, there is considerable interest in the central role of IL-23/IL-17 axis in type 3 immunity and the therapeutic potential of blocking this axis to ameliorate enthesitis and NBF in AS. AS immunopathology involves a variety of immune cells, including both innate and adoptive immune cells, to orchestrate the immune response driving type 3 immunity. In response to external stimuli of inflammatory cytokines, local osteo-chondral progenitor cells activate intra-cellular anabolic molecules and signals involving hedgehog, bone morphogenetic proteins, receptor activator of nuclear factor kappa-B ligand, and Wnt pathways to promote NBF in AS. Here, we provide an overview of the current immunopathology and future directions for the treatment of enthesitis and NBF associated with AS.

Changes in bone formation regulator biomarkers in early axial spondyloarthritis

OBJECTIVE

The hallmark of advanced axial SpA (axSpA) is spine ankylosis due to excessive ectopic bone formation. This prospective study aimed to describe the changes in serum levels of different regulators [sclerostin, dickkopf-1 (DKK-1)] and markers of bone formation [bone morphogenetic protein 7 (BMP-7)] over 5 years in early axSpA patients and to assess determinants of such changes.

METHODS

The DEvenir des Spondyloarthropathies Indifférenciées Récentes cohort is a prospective, multicentre French study of 708 patients with early (>3 months-<3 years) inflammatory back pain suggestive of axSpA. Serum levels of BMP-7, sclerostin and DKK-1 were assessed at baseline and after 2 and 5 years. Changes in bone formation regulators over time were analysed using mixed linear models.

RESULTS

Serum BMP-7 significantly increased over time, with a median relative change of 223.7% [interquartile range (IQR) 0-10 700 (0.17 pg/ml/month), P < 0.001]. Serum sclerostin significantly increased over time, with a median relative change of 14.8% [IQR -7.9-41.4% (0.001 ng/ml/month), P < 0.001]. Serum DKK-1 did not significantly change over time. Serum BMP-7 increased over time in active disease (Ankylosing Spondylitis Disease Activity Score with CRP ≥1.3, P = 0.01), but the increase was less pronounced with TNF inhibitor (TNFi) use (P < 0.001). No determinant was associated with serum sclerostin change.

CONCLUSION

Serum BMP-7 change over 5 years was related with inflammation; it was increased in active disease, but the increase was low with TNFi use. Serum sclerostin levels significantly increased over time, but to a lesser degree than for serum BMP-7.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov/, NCT01648907.

The Influence of Pro-Inflammatory Factors on Sclerostin and Dickkopf-1 Production in Human Dental Pulp Cells Under Hypoxic Conditions

Sclerostin (Sost) and dickkopf (Dkk)-1 are inhibitors of the Wnt signaling pathway that plays a role in regenerative processes. Hypoxia-based strategies are used for regenerative approaches, but the influence of hypoxia on Sost and Dkk-1 production in a pro-inflammatory environment is unclear. The aim of this study was to assess if pro-inflammatory molecules have an influence on Sost and Dkk-1 production in dental pulp cells (DPC) under normoxia and hypoxia. Human DPC were treated with interleukin (IL)-1β, tumor necrosis factor (TNF)α or transforming growth factor (TGF)β, with L-mimosine (L-MIM) or hypoxia or a combination. Sost and Dkk-1 mRNA and protein levels were measured with qPCR and western blot, respectively. TNFα, TGFβ, L-MIM, or combined treatment did not modulate Sost and Dkk-1. IL-1β downregulated Sost at the mRNA level. Hypoxia alone and together with inflammatory markers downregulated Dkk-1 at the mRNA level. Sost and Dkk-1 protein production was below the detection limit. In conclusion, there is a differential effect of hypoxia and IL-1β on the mRNA production of Sost and Dkk-1. Pro-inflammatory molecules do not further modulate the effects of L-MIM or hypoxia on Sost and Dkk-1 production in DPC.

Wnt Signaling and Biological Therapy in Rheumatoid Arthritis and Spondyloarthritis

The Wnt signaling pathway plays a key role in several biological processes, such as cellular proliferation and tissue regeneration, and its dysregulation is involved in the pathogenesis of many autoimmune diseases. Several evidences support its role especially in bone complications of rheumatic diseases. In Rheumatoid Arthritis (RA), the Wnt signaling is implicated in systemic and localized bone loss, while available data of its role in Spondyloarthritis (SpA) are conflicting. In the last few decades, the quality of life of rheumatic patients has been dramatically improved by biological therapy, targeting cytokines involved in the pathogenesis of these diseases like tumor necrosis factor (TNF)α, interleukin (IL)-1, IL-6, IL-17. In this review, we reviewed the role of Wnt signaling in RA and SpA, focusing on the effect of biological therapy on this pathway and its possible clinical implications.

Correlation between magnetic resonance imaging (MRI) findings and the new bone formation factor Dkk-1 in patients with spondyloarthritis

In recent years, MRI has been regarded as a major diagnostic tool for spondyloarthritis (SpA), and anti-TNF therapy has been widely confirmed as an effective treatment strategy. This study was designed to investigate the correlation between the secreted protein dickkopf-1 (Dkk-1) and abnormal findings on magnetic resonance imaging (MRI) through a prospective study of 30 cases of SpA. Thirty patients with active SpA were included, all treated with recombinant human tumor necrosis factor (TNF) receptor-antibody fusion protein (YiSaiPu) injection at 50 mg/week for 6 months. All patients were also examined for their clinical, serological, and imaging manifestations of the condition before and after treatment. In patients receiving TNF inhibitor treatment, the erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and clinical activity indices BASDAI, BASFI, BASMI, ASDAS-CRP were significantly decreased (p < 0.01). Serum Dkk-1 concentration was also significantly decreased (p < 0.05), as were the scores of bone marrow edema of the sacroiliac joints and the spine (p < 0.05). The score of sacroiliac joint backfill was significantly increased (p < 0.05), and the baseline and changes in the serum Dkk-1 concentration were significantly correlated with the baseline and changes in spinal bone marrow edema levels. Inhibition of the level of serum Dkk-1 by TNF inhibitors may be the molecular basis for inhibiting the formation of new bone in SpA patients. In addition, spinal marrow edema may have significance for predicting new bone formation.

Results from Polish Spondyloarthritis Initiative registry (PolSPI) - methodology and data from - the first year of observation

OBJECTIVES

Report on one-year results from the Polish Spondyloarthritis Initiative registry (PolSPI), containing the cross-sectional analysis of clinical and imaging data as well as database methodology.

MATERIAL AND METHODS

The PolSPI registry includes patients with axial (axSpA) and peripheral (perSpA) spondyloarthritis according to ASAS classification criteria, and/or patients with ankylosing spondylitis according to modified New York criteria, psoriatic arthritis according to CASPAR criteria, arthropathy in inflammatory bowel disease, reactive arthritis, juvenile spondyloarthritis or undifferentiated spondyloarthritis. Epidemiologic data and history of signs, symptoms and treatment of spondyloarthritis are collected and assessment of disease activity is performed. Radiographic images of sacroiliac joint, cervical and lumbar spine, and results of bone densitometry are collected. Every 6 months blood samples for inflammatory markers, and for long-term storage are taken.

RESULTS

During a one-year period from September 2015 to August 2016, 63 patients were registered on an electronic database; 44 (69.8%) of patients were classified as axial spondyloarthritis (axSpA) and 19 (30.2%) as peripheral spondyloarthritis (perSpA) according to ASAS criteria. Statistically significant differences between axSpA and perSpA were discovered in the percentage of HLA-B27 antigen occurrence (92.6% and 50%, respectively), BASDAI (2.8% and 4.1%, respectively), DAS 28 (2.66% and 4.03%, respectively), percentage of peripheral arthritis (20% and 88.8%, respectively), enthesitis (26.7% and 70.6%, respectively), dactylitis (6.7% and 88.9%, respectively), as well as extra-articular symptoms: acute anterior uveitis (26.7% and 5.6%, respectively) and psoriasis (6.9% and 55.6%, respectively). Patients with axSpA had significantly higher mean grade of sacroiliac involvement according to New York criteria, higher mSASSS score, and lower T-score in femoral neck in bone densitometry.

CONCLUSIONS

At the early stage of the disease patients with axSpA compared to those with perSpA, have more advanced structural damage of sacroiliac joints and spine, and lower bone mineral density in the femoral neck. In the upcoming years the PolSPI registry will prospectively follow-up patients with SpA, recording response to treatment and carrying out research on interaction of inflammation and bone remodelling.

A novel role of bone morphogenetic protein-7 in the regulation of adhesion and migration of human monocytic cells

BACKGROUND

Bone morphogenetic protein (BMP) 7 is abundant in atherosclerotic plaques and increases monocyte pro-coagulant activity by enhancing tissue factor (TF) expression. While several members of the BMP superfamily are able to serve as chemotactic agents for monocytes, the role of BMP-7 in regulation of monocyte motility is not known.

AIMS

To assess the effect of BMP-7 on adhesive and migratory properties of human monocytes.

METHODS

Chemokinesis, adhesion, and transendothelial migration of BMP-7-treated THP-1 cells and human monocytes were analysed using live-cell imaging, orbital shear, and Boyden chamber assays. Surface presentation of β2 integrins and phosphorylation status of Akt & focal adhesion kinase (FAK) were studied by flow cytometry and Western blot.

RESULTS

High levels of BMP-7 protein were detectable in intimal regions of atherosclerotic plaques; BMP-7 significantly enhanced THP-1 and monocyte chemokinetic properties in vitro (1.21+0.01 and 1.76+0.21 fold increase in crawling distance, respectively). Under orbital shear, adhesion of monocytic cells to microvascular endothelial cell (MVEC) monolayers was also significantly increased by BMP-7 (3.89+1.56 and 2.57+0.97 fold over vehicle). Moreover, BMP-7 accelerated transendothelial migration of THP-1 cells and monocytes towards MCP-1 (5.91+0.88 and 2.96±0.65 fold increase, respectively). BMP-7 enhanced cell surface presentation of β2 integrins in the active conformation. Observed effects were determined to be Akt and FAK dependent, as shown by pharmacological inhibition.

CONCLUSION

BMP-7 directly upregulates adhesion and migration of human monocytic cells via activation of β2 integrins, Akt, and FAK. Our findings suggest that BMP-7 may serve as a novel contributor to atherogenesis.

Serum levels of Dkk-1, sclerostin and VEGF in patients with ankylosing spondylitis and their association with smoking, and clinical, inflammatory and radiographic parameters

OBJECTIVE

To evaluate serum Dickkopf-1 (Dkk-1), sclerostin and vascular endothelial growth factor (VEGF) levels in patients with ankylosing spondylitis (AS) compared to healthy controls as well as their association with smoking, and clinical, inflammatory and radiographic parameters.

METHODS

Serum samples for total Dkk-1, sclerostin and VEGF were obtained from 57 tumour necrosis factor (TNF) inhibitor naïve patients with AS and 34 sex-, age- and body mass index (BMI)-matched controls. The erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), Bath AS Disease Activity Index (BASDAI), Bath AS Functional Index (BASFI), modified Stroke AS Spine Score (mSASSS) and smoking status were assessed for each patient.

RESULTS

There was no significant difference in serum bone metabolism markers between AS patients and controls. Dkk-1 levels were significantly (P<0.05) higher in AS patients with elevated ESR and CRP and no syndesmophytes, and were significantly (P<0.001) correlated with sclerostin levels (r=0.592). VEGF levels were significantly (P<0.05) higher in AS patients with current and ever smoking, elevated ESR and CRP, and high BASDAI and BASFI, and were significantly (P<0.05) correlated with ESR (r=0.284), CRP (r=0.285), BASDAI (r=0.349) and BASFI (r=0.275). In multivariate regression analyses, high Dkk-1 levels were significantly (P≤0.001) associated with elevated ESR and CRP, no syndesmophytes and high sclerostin levels, and high VEGF levels significantly (P<0.05) with ever smoking, and elevated ESR and CRP.

CONCLUSION

In AS, serum Dkk-1 concentrations appear to be related not only to syndesmophyte formation but also to systemic inflammation. Furthermore, high VEGF levels may be associated with smoking exposure.

Association between serum dickkopf-1 levels and disease duration in axial spondyloarthritis

BACKGROUND

Axial spondyloarthritis (axSpA) is characterized by new bone formation. The complex systems underlying this process involve Wnt-signaling pathway. It has been observed that serum levels of dickkopf-1 (DKK-1), an important inhibitor of Wnt-signaling, are decreased in patients with axSpA. However, these data are from studies including only patients with long-standing disease. The aim of this study is to investigate if symptom duration influences on serum DKK-1 levels in patients with axSpA.

MATERIAL AND METHODS

A cross-sectional study including consecutive patients with axSpA (ASAS criteria) naïve for anti-TNF therapy. Collected data included demographic and disease characteristics, time since first symptom onset, assessment of disease activity and function, and determination of DKK-1 serum levels. Patients were classified as early axSpA (symptom duration ≤5 years) and established axSpA (>5 years). Linear regression models were employed to investigate the variables related to DKK-1 serum levels.

RESULTS

In total, 90 patients were included. Sixty-eight patients had early axSpA and 22 had established disease. Serum levels of DKK-1 were significantly higher in patients with early axSpA compared with established axSpA (22.1±12.6 vs 16.4±10.7pM; p=0.04). Among all tested variables, only symptom duration was significantly and inversely correlated with DKK-1 serum levels (beta: -0.041; p=0.01).

CONCLUSION

Serum DKK-1 levels in axSpA depend on disease duration. As disease duration increases, DKK-1 serum levels decrease. Based on this, an intensive treatment at early stages of the disease could have a better outcome on inhibiting/slowing radiographic progression in patients with axSpA.

Serum Heme Oxygenase-1 and BMP-7 Are Potential Biomarkers for Bone Metabolism in Patients with Rheumatoid Arthritis and Ankylosing Spondylitis

Backgrounds. Heme oxygenase-1 (HO-1) has been reported to play a regulatory role in osteoclastogenesis. Bone morphogenetic protein (BMP) pathways induce osteoblastic differentiation and bone remodeling. Aims. To identify serum levels of HO-1, BMP-7, and Runt related-transcription factor 2 (Runx2) in patients with rheumatoid arthritis (RA) and ankylosing spondylitis (AS) and to investigate the relationships between HO-1, BMP-7, Runx2, and other common biomarkers for bone metabolism. Results. Serum levels of HO-1 and BMP-7 were revealed to be significantly higher in patients with RA or AS than in healthy controls (p < 0.01). In RA group, HO-1 was positively correlated with BMP-7, Runx2, and tartrate-resistant acid phosphatase-5b (TRAP-5b) (p < 0.05, resp.), BMP-7 was positively correlated with Runx2 and TRAP-5b (p < 0.05, resp.), and Runx2 was negatively correlated with N-terminal midfragment of osteocalcin (NMID) (p < 0.05). In AS group, we observed identical correlation between HO-1 and BMP-7, but opposite correlations between BMP-7 and TRAP-5b and between Runx2 and NMID, when comparing with the RA cohort. Conclusion. Our findings suggest that HO-1 and BMP-7 are potential biomarkers for bone metabolism in patients with RA and AS. The different correlations between the bone markers point to distinct differences in bone remodeling pathways in the two types of arthritis.

Alteration of Bone Turnover Markers in Canonical Wingless Pathway in Patients With Ankylosing Spondylitis

Objectives

This study aims to determine the levels of bone turnover markers in canonical wingless pathway in patients with ankylosing spondylitis (AS) and the correlation with disease activity indexes.

Patients and methods

We recruited a total of 43 AS patients (34 males, 8 females; mean age 36.8±9.3 years; range 22 to 62 years) and age- and sex-matched 42 healthy controls (32 males, 10 females; mean age 36.1±9.7; range 24 to 59 years). Serum levels of components of canonical wingless pathway including Dickkopf-1, glycogen synthase kinase-3β, β-catenin, alkaline phosphatase, and osteocalcin were detected using enzyme- linked immunosorbent assay method. All patients were assessed in terms of erythrocyte sedimentation rate, C-reactive protein, Bath Ankylosing Spondylitis Disease Activity Index, Bath Ankylosing Spondylitis Functional Index, Ankylosing Spondylitis Disease Activity Score, and the modified Stoke's Ankylosing Spondylitis Spine Score. Pearson's correlation test was used to analyze the correlation between serum bone turnover markers and clinical assessment indexes.

Results

No significant difference was observed between AS patients and healthy controls for the levels of glycogen synthase kinase-3β, β-catenin, alkaline phosphatase, and osteocalcin, respectively (p>0.05). The level of Dickkopf-1 was significantly higher in AS patients (1914.5±407.8 pg/mL) than in healthy controls (1729.1±352.9 pg/mL) (p<0.05). There was no correlation between high Dickkopf-1 level and any of the clinical parameters contributing to inflammation or bone formation. However, the correlation between osteocalcin and disease duration was significant in AS patients (r=0.323, p=0.034).

Conclusion

Alteration of bone turnover markers in canonical wingless pathway was observed in AS. This might partially explain the complicated mechanism of bone formation in the disease.

Bone morphogenetic proteins in inflammation, glucose homeostasis and adipose tissue energy metabolism

Bore morphogenetic proteins (BMPs) are members of the transforming growth factor (TGF)-β superfamily, a group of secreted proteins that regulate embryonic development. This review summarizes the effects of BMPs on physiological processes not exclusively linked to the musculoskeletal system. Specifically, we focus on the involvement of BMPs in inflammatory disorders, e.g. fibrosis, inflammatory bowel disease, anchylosing spondylitis, rheumatoid arthritis. Moreover, we discuss the role of BMPs in the context of vascular disorders, and explore the role of these signalling proteins in iron homeostasis (anaemia, hemochromatosis) and oxidative damage. The second and third parts of this review focus on BMPs in the development of metabolic pathologies such as type-2 diabetes mellitus and obesity. The pancreatic beta cells are the sole source of the hormone insulin and BMPs have recently been implicated in pancreas development as well as control of adult glucose homeostasis. Lastly, we review the recently recognized role of BMPs in brown adipose tissue formation and their consequences for energy expenditure and adiposity. In summary, BMPs play a pivotal role in metabolism beyond their role in skeletal homeostasis. However, increased understanding of these pleiotropic functions also highlights the necessity of tissue-specific strategies when harnessing BMP action as a therapeutic target.

Effects of tumor necrosis factor-α inhibitors on new bone formation in ankylosing spondylitis

OBJECTIVES

To better understand the effect of TNF-α inhibitors (TNFi) on new bone formation in ankylosing spondylitis (AS) patients.

METHODS

We systematically searched the articles in EMBASE and PubMed.

RESULTS

Fifteen articles were enrolled. In all the 9 TNFi-treated cohorts, the vertebral corners with inflammatory lesions at baseline were at higher risk to develop new syndesmophytes than those without inflammatory lesions, although a few syndesmophytes also developed at the vertebral corners without inflammatory lesions at baseline. The advanced inflammatory lesions including fat deposition on baseline MRI showed a higher risk for syndesmophyte formation than the acute inflammatory lesions. Because the number of analyzed vertebral corners were too small, it might not be true that new syndesmophytes developed more frequently at the corners with inflammatory lesions completely resolved than those with persistent inflammation after TNFi treatment. Four studies with 2-year follow-up revealed null effect of TNFi on radiographic progression compared with historical controls with lower disease activity, and 3 studies with ≥4-year follow-up proved inhibitory effect of TNFi on new bone formation in AS patients. Patients with a delay of >10 years in starting TNFi therapy were more likely to experience radiographic progression as compared to those who started earlier.

CONCLUSIONS

In TNFi treated AS patients, baseline inflammation is linked with syndesmophyte development. An earlier initiation of TNFi therapy may slow the radiographic progression in AS, and TNFi may lose its benefit of retarding new bone formation at advanced stage of AS especially after the focal fat infiltration or syndesmophyte formation.

High level of interleukin-32 gamma in the joint of ankylosing spondylitis is associated with osteoblast differentiation

Backgound

The formation of bony spurs and ankylosis is a key pathognomic feature in ankylosing spondylitis (AS) and results in functional impairment. The aim of this study was to investigate the role of IL-32γ in osteoblast (OB) differentiation and its association with the pathogenesis of AS.

Methods

The concentration and expression of IL-32γ were evaluated in synovial fluid and tissue from patients with AS, rheumatoid arthritis (RA) and osteoarthritis (OA), using enzyme-linked immunosorbent assay and immunohistochemistry. To establish whether IL-32γ affects OB differentiation, we used calvarial cells of IL-32γ transgenic (TG) mice or wild-type (WT) mice. To elucidate the mechanism of osteoblastogenesis, levels of regulators were assayed in IL-32γ TG mice and in primary OBs after IL-32γ stimulation.

Results

The IL-32γ levels were higher in the synovial fluid of AS patients compared with RA or OA patients and the expression of IL-32 was higher in AS synovia than in RA or OA synovia. Additional IL-32γ stimulation in precursor cells enhanced OB differentiation potentially and IL-32γ TG mice showed higher rates of OB differentiation than WT mice. IL-32γ reduced the expression of DKK-1, a negative regulator, in both WT precursor cells and human OBs and the constitutive expression of DKK-1 was suppressed in calvarial cells from IL-32γ TG mice.

Conclusions

The elevated level of IL-32γ in AS joint could enhance OB differentiation via DKK-1 suppression. Therefore, IL-32γ might be a putative molecular target to prevent the abnormal bone formation in AS.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0870-4) contains supplementary material, which is available to authorized users.

Circulating miRNAs as potential biomarkers of therapy effectiveness in rheumatoid arthritis patients treated with anti-TNFα

Introduction

The advent of anti-tumor necrosis factor alpha (anti-TNFα) drugs has considerably improved medical management in rheumatoid arthritis (RA) patients, although it has been reported to be ineffective in a fraction of them. MicroRNAs (miRNAs) are small, non-coding RNAs that act as fine-tuning regulators of gene expression. Targeting miRNAs by gain or loss of function approaches have brought therapeutic effects in various disease models. The aim of this study was to investigate serum miRNA levels as predictive biomarkers of response to anti-TNFα therapy in RA patients.

Methods

In total, 95 RA patients undergoing anti-TNFα/disease-modifying antirheumatic drugs (anti-TNFα/DMARDs) combined treatments were enrolled. Serum samples were obtained at 0 and 6 months and therapeutic efficacy was assessed. miRNAs were isolated from the serum of 10 patients before and after anti-TNFα/DMARDs combination therapy, cDNA transcribed and pooled, and human serum miRNA polymerase chain reaction (PCR) arrays were performed. Subsequently, selected miRNAs were analyzed in a validation cohort consisting of 85 RA patients. Correlation studies with clinical and serological variables were also performed.

Results

Ninety percent of RA patients responded to anti-TNFα/DMARDs combination therapy according to European League Against Rheumatism (EULAR) criteria. Array analysis showed that 91% of miRNAS were overexpressed and 9% downregulated after therapy. Functional classification revealed a preponderance of target mRNAs involved in reduction of cells maturation - especially on chondrocytes - as well as in immune and inflammatory response, cardiovascular disease, connective tissue and musculoskeletal system. Six out of ten miRNAs selected for validation were found significantly upregulated by anti-TNFα/DMARDs combination therapy (miR-16-5p, miR-23-3p, miR125b-5p, miR-126-3p, miRN-146a-5p, miR-223-3p). Only responder patients showed an increase in those miRNAs after therapy, and paralleled the reduction of TNFα, interleukin (IL)-6, IL-17, rheumatoid factor (RF), and C-reactive protein (CRP). Correlation studies demonstrated associations between validated miRNAs and clinical and inflammatory parameters. Further, we identified a specific plasma miRNA signature (miR-23 and miR-223) that may serve both as predictor and biomarker of response to anti-TNFα/DMARDs combination therapy.

Conclusions

miRNA levels in the serum of RA patients before and after anti-TNFα/DMARDs combination therapy are potential novel biomarkers for predicting and monitoring therapy outcome.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0555-z) contains supplementary material, which is available to authorized users.

Secondary osteoporosis: pathophysiology & diagnosis

Osteoporosis is a skeletal disease characterized by decreased bone mass and microarchitectural changes in bone tissue that increase the susceptibility to fracture. Secondary osteoporosis is loosely defined as low bone mineral density or increased risk of fragility fracture caused by any factor other than aging or postmenopausal status. The purpose of this review is to discuss the current understanding of the pathophysiology and contribution to fracture risk of many of the more common causes of secondary osteoporosis, as well as diagnostic considerations, outlined by organ system. While not comprehensive, included are a wide array of diseases, conditions, and medications that have been associated with bone loss and susceptibility to fractures. The hope is to highlight the importance to the general clinician of screening for and treating the osteoporosis in these patients, so to limit the resultant increased morbidity associated with fractures.