Evidence for uncoupling of inflammation and joint remodeling in a mouse model of spondylarthritis

Entheses and bones in spondyloarthritis: 2008 Annual Research and Education Meeting of the Spondyloarthritis Research and Therapy Network (SPARTAN)

The Spondyloarthritis Research and Therapy Network (SPARTAN), founded in 2003 to promote research, education, and treatment of ankylosing spondylitis (AS) and related forms of spondyloarthritis (SpA), held its 6th Annual Research and Education Meeting in July 2008 in Cleveland, Ohio, USA. The overall theme of the meeting was entheses and bones in SpA, which included presentations on the anatomy and physiology of the synovial-entheseal complex; bone formation and destruction, and the effect of inflammation on bone; the Th17 axis, HLA-B27, IL23R, and ARTS1; and breakout sessions on epidemiology and registries.

Assessment of radiographic progression in the spines of patients with ankylosing spondylitis treated with adalimumab for up to 2 years

Introduction

Ankylosing spondylitis (AS) is a chronic rheumatic disease associated with spinal inflammation that subsequently leads to progression of structural damage and loss of function. The fully human anti-tumor necrosis factor (anti-TNF) antibody adalimumab reduces the signs and symptoms and improves overall quality of life in patients with active AS; these benefits have been maintained through 2 years of treatment. Our objective was to compare the progression of structural damage in the spine in patients with AS treated with adalimumab for up to 2 years versus patients who had not received TNF antagonist therapy.

Methods

Radiographs from patients with AS who received adalimumab 40 mg every other week subcutaneously were pooled from the Adalimumab Trial Evaluating Long-Term Efficacy and Safety for Ankylosing Spondylitis (ATLAS) study and a Canadian AS study (M03-606). Radiographic progression from baseline to 2 years in the spine of adalimumab-treated patients from these two studies (adalimumab cohort, n = 307) was compared with an historic anti-TNF-naïve cohort (Outcome in AS International Study [OASIS], n = 169) using the modified Stoke AS Spine Score (mSASSS) method.

Results

mSASSS results were not significantly different between the adalimumab cohort and the OASIS cohort, based on baseline and 2-year radiographs. Mean changes in mSASSS from baseline to 2 years were 0.9 for the OASIS cohort and 0.8 for the adalimumab cohort (P = 0.771), indicating similar radiographic progression in both groups. When results for patients in the OASIS cohort who met the baseline disease activity criteria for the ATLAS and Canadian studies (OASIS-Eligible cohort) were analyzed, there was no significant difference in mean change in mSASSS from baseline to 2 years between OASIS-Eligible patients and adalimumab-treated patients; the mean changes in mSASSS were 0.9 for the OASIS-Eligible cohort and 0.8 for the adalimumab cohort (P = 0.744).

Conclusions

Two years of treatment with adalimumab did not slow radiographic progression in patients with AS, as assessed by the mSASSS scoring system, when compared with radiographic data from patients naïve to TNF antagonist therapy.

Trial registration

Canadian study (M03-606) ClinicalTrials.gov identifier: NCT00195819; ATLAS study (M03-607) ClinicalTrials.gov identifier: NCT00085644.

Unusual cervical spine involvement in psoriatic arthritis: a case series

Cervical spine involvement in psoriatic arthritis is not uncommon and can often mimic symptoms and signs of ankylosing spondylitis. However, some specific features may help to differentiate between patients with psoriatic arthritis and ankylosing spondylitis. Here, we present a series of three patients with psoriatic arthritis and increasing cervical pain and loss of mobility. Each of the cases shows specific radiographic characteristics. These cases therefore illustrate different aspects of the involvement of the cervical spine in axial forms of psoriatic arthritis and highlight the importance of proper evaluation and management of axial disease in psoriatic arthritis.

Clinical and imaging efficacy of infliximab in HLA-B27-Positive patients with magnetic resonance imaging-determined early sacroiliitis

OBJECTIVE

To evaluate the efficacy of infliximab in HLA-B27-positive patients with magnetic resonance imaging (MRI)-determined early sacroiliitis, using both clinical and MRI assessments.

METHODS

Forty patients with recent-onset inflammatory back pain, as assessed by the Calin criteria, HLA-B27 positivity, clinical disease activity as measured by the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), pain and morning stiffness, and magnetic resonance imaging (MRI)-determined sacroiliac joint bone edema were randomized in a double-blind manner to receive infliximab 5 mg/kg or placebo at 0, 2, 6, and 12 weeks. MRI scans were performed at baseline and 16 weeks and scored by 2 observers (blinded to both the order of the scans and to treatment group), using the Leeds scoring system. Clinical assessments included the BASDAI, the Bath Ankylosing Spondylitis Functional Index (BASFI), the Ankylosing Spondylitis Quality of Life (ASQoL) instrument, the ASsessment in Ankylosing Spondylitis International Working Group criteria (ASAS) for improvement, and markers of inflammation.

RESULTS

The mean reduction in the total MRI score from week 0 to week 16 was significantly greater in infliximab-treated patients compared with placebo-treated patients (P = 0.033). On average, significantly more lesions resolved in the infliximab group (P < 0.001), while significantly more new lesions developed in the placebo group (P = 0.004). Significantly greater improvement in the infliximab group versus the placebo group was also observed for changes from week 0 to week 16 in the BASDAI (P = 0.002), BASFI (P = 0.004), and ASQoL (P = 0.007) scores. Responses according to the ASAS criteria for 40% improvement, the ASAS criteria for 20% improvement in 5 of 6 domains, and ASAS partial remission were achieved by 61%, 44%, and 56% of infliximab-treated patients, respectively. Infliximab was well tolerated, and no serious adverse events were observed.

CONCLUSION

Infliximab was an effective therapy for early sacroiliitis, providing a reduction in disease activity by week 16. This study is the first to show that infliximab is effective for reducing clinical and imaging evidence of disease activity in patients with MRI-determined early axial spondylarthritis.

Progress in spondylarthritis. Mechanisms of new bone formation in spondyloarthritis

Targeted therapies that neutralize tumour necrosis factor are often able to control the signs and symptoms of spondyloarthritis. However, recent animal model data and clinical observations indicate that control of inflammation may not be sufficient to impede disease progression toward ankylosis in these patients. Bone morphogenetic proteins and WNTs (wingless-type like) are likely to play an important role in ankylosis and could be therapeutic targets. The relationship between inflammation and new bone formation is still unclear. This review summarizes progress made in our understanding of ankylosis and offers an alternative view of the relationship between inflammation and ankylosis.

Developments in the scientific and clinical understanding of the spondyloarthritides

Major advances have been achieved over the last 10 years both in the clinical and scientific understanding of the spondyloarthritides (SpA), which can be separated in predominantly axial and predominantly peripheral SpA. The clinical progress includes the development of classification criteria, strategies for early diagnosis, definition of outcome criteria for clinical studies, and the conduction of a series of clinical studies with a focus on tumor necrosis factor (TNF) blockers. The proven high efficacy of TNF blocker treatment has meant a breakthrough for SpA patients, who until recently had only quite limited treatment options. More and more data have accumulated over recent years in regard to long-term efficacy and safety, prediction of response, and the relevance of extrarheumatic manifestations such as uveitis, psoriasis, and inflammatory bowel disease for treatment decisions with TNF blockers. A better understanding of the interaction of the immune system and inflammation with bone degradation/new bone formation is crucial for the development of optimal treatment strategies to prevent structural damage. Recent results from genetic studies could show that, besides HLA-B27, the interleukin-23 receptor and the ARTS1 enzyme are associated with ankylosing spondylitis. Only when the exact pathogenesis is clarified will a curative treatment be possible.

What do biomarkers tell us about the pathogenesis of ankylosing spondylitis?

Biomarkers may provide information that promotes understanding of prognosis, disease activity, and pathogenesis in ankylosing spondylitis. Biomarkers reflecting disease activity (metallo-proteinase-3) and inflammatory lesions on magnetic resonance imaging predict new bone formation and are ameliorated by anti-tumor necrosis factor therapy, yet this treatment may not prevent new bone formation. Moreover, elevated levels of biomarkers reflecting tissue repair (bone-specific alkaline phosphatase) post-treatment together with magnetic resonance imaging indicates such treatment may even promote repair through new bone formation. Tumor necrosis factor regulation of Dickkopf-1 may constitute a molecular brake that controls osteoblastogenesis through wingless and bone morphogenetic proteins in an established inflammatory lesion in ankylosing spondylitis.

Animal models of spondyloarthritis

Animal models are available for the study of several different aspects of spondyloarthritis. The models include naturally occurring spontaneous disorders in primates and rodents, spontaneous disorders in transgenic or gene-deleted rodents and induced disorders in rodents. Areas of investigation to which these models contribute include the role HLA-B27, processes of spinal and peripheral joint inflammation and calcification, immune responses to candidate antigens and the role of TNF.

Bone formation versus bone resorption in ankylosing spondylitis

Ankylosing spondylitis (AS) and other forms of seronegative spondylarthritis (SpA) are characterized by two major processes in joints-the first is chronic inflammation and the second is progressive ankylosis. Both features go hand-in-hand and determine the clinical picture of disease, which is joint pain, progressive stiffness and, in case ofperipheral joint involvement also joint swelling. The interplay between inflammation and ankylosis is best illustrated in AS, where chronic inflammation of the spine leads to progressive stiffness, reduced spinal mobility and kyphosis. AS may thus be considered as a synthesis of inflammatory disease and bone disease.

The role of Wnt proteins in arthritis

Wnt proteins regulate organ development, tumorigenesis and bone homeostasis, among other functions. The binding of Wnt proteins to plasma membrane receptors on mesenchymal cells induces the differentiation of these cells into the osteoblast lineage and thereby supports bone formation. Wnts are also key signaling proteins in joint remodeling processes. Active Wnt signaling contributes to osteophyte formation and might have an essential role in the anabolic pattern of joint remodeling that is observed in ankylosing spondylitis and osteoarthritis. By contrast, blockade of Wnt signaling facilitates bone erosion and contributes to catabolic joint remodeling, a process that is observed in rheumatoid arthritis. This Review summarizes current knowledge of the molecular regulation of joint remodeling associated with chronic arthritis, focusing on the role of the Wnt proteins and their inhibitors. It also addresses the role of Wnt in determining the differences in clinical presentation of inflammatory arthropathies and discusses implications for future therapy.

Altered bone remodeling in psoriatic arthritis

Bone is a highly dynamic organ that interacts with a wide array of cells and tissues. Recent studies have unveiled unanticipated connections between the immune and skeletal systems, and this relationship led to the development of a new field called osteoimmunology. This field will enable investigators to translate basic science findings in bone biology to clinical applications for inflammatory joint diseases such as psoriatic arthritis (PsA). This review examines the disruption of bone homeostasis in PsA and discusses the pivotal role of osteoclasts, osteoblasts, and signaling pathways in the altered remodeling observed in this inflammatory arthritis. It also discusses the effects of tumor necrosis factor inhibition on bone resorption and new bone formation in PsA.

Bone morphogenetic proteins in tissue engineering: the road from the laboratory to the clinic, part I (basic concepts)

Discovered in 1965, bone morphogenetic proteins (BMPs) are a group of cytokines from the transforming growth factor-beta (TGFbeta) superfamily with significant roles in bone and cartilage formation. BMPs are used as powerful osteoinductive components of diverse tissue-engineering products for the healing of bone. Several BMPs with different physiological roles have been identified in humans. The purpose of this review is to cover the biological function of the main members of BMP family, the latest research on BMPs signalling pathways and advances in the production of recombinant BMPs for tissue engineering purposes.

The relationship between inflammation and new bone formation in patients with ankylosing spondylitis

INTRODUCTION

Spinal inflammation as detected by magnetic resonance imaging and new bone formation as identified by conventional radiographs are characteristic of ankylosing spondylitis. Whether and how spondylitis and syndesmophyte formation are linked are unclear. Our objective was to investigate whether and how spinal inflammation are associated with new bone formation in ankylosing spondylitis.

METHODS

Spinal magnetic resonance images and conventional radiographs from 39 ankylosing spondylitis patients treated with anti-tumour necrosis factor (anti-TNF) agents at baseline and after 2 years were analysed for syndesmophyte formation at vertebral edges with or without inflammatory lesions at baseline.

RESULTS

Overall, 922 vertebral edges at the cervical and lumbar spine were analysed. At baseline, the proportion of vertebral edges with and without inflammation (magnetic resonance imaging) that showed structural changes (conventional radiographs) was similar (in total, 16.6% of all vertebral edges in 71.4% of patients). From the perspective of syndesmophyte formation (n = 26, 2.9%) after 2 years, there were more vertebral edges without (62%) than with (38%) inflammation at baseline (P = 0.03). From the perspective of spinal inflammation at baseline (n = 153 vertebral edges), more syndesmophytes developed at vertebral edges with (6.5%) than without (2.1%) inflammation (P = 0.002, odds ratio 3.3, 95% confidence interval 1.5 to 7.4). Inflammation persisted in 31% of the initially inflamed vertebral edges (n = 132), and new lesions developed in 8% of the vertebral edges without inflammation at baseline (n = 410). From the perspective of spinal inflammation after 2 years (n = 72 vertebral edges), 5.6% of the vertebral edges showed syndesmophyte development in contrast to 1.9% of the vertebral edges with new syndesmophytes without inflammation (P = 0.06).

CONCLUSIONS

These findings obtained in patients treated with anti-TNF agents suggest linkage and some dissociation of inflammation and new bone formation in ankylosing spondylitis. Although syndesmophytes were also found to develop at sites where no inflammation had been seen by magnetic resonance imaging at baseline, it was more likely that syndesmophytes developed in inflamed vertebral edges. More effective suppression of spinal inflammation may be required to inhibit structural damage in ankylosing spondylitis.

Th17 development and autoimmune arthritis in the absence of reactive oxygen species

Dendritic cells (DC) express a functional NADPH oxidase and produce reactive oxygen species (ROS) upon interaction with microbes and T cells. Exposure to ROS leads to DC activation and maturation, as evidenced by phenotypic and functional changes. We have evaluated how endogenous ROS production affects the cytokine secretion pattern and T cell-activating capacity of bone marrow-derived murine DC. DC treated with ROS scavengers, as well as DC from mice that lack a functional NADPH oxidase (and thereby inherently deficient in ROS production) produced significantly increased levels of IL-1beta, IL-6, TNF-alpha and TGF-beta in response to microbial activation. DC deficient in ROS production induced high levels of IFN-gamma and IL-17 in responding T cells after Ag-specific or superantigen-induced activation. Finally, we show that ROS deficiency affected the induction of a T cell-dependent inflammatory condition, collagen-induced arthritis (CIA). C57BL/6 mice that lack a functional NADPH oxidase developed a severe and erosive CD4-dependent CIA, whereas the majority of the congenic wild-type animals remained healthy. These data suggest that ROS act as immunomodulators in DC-driven T cell activation and perhaps also in T cell-dependent immunopathology.

Psoriatic disease--from skin to bone

Psoriatic arthritis is an inflammatory joint disease that is heterogeneous in presentation and clinical course. Evidence that this disease is distinct from rheumatoid arthritis and other spondyloarthropathies is based on data derived from characteristic clinical features, histopathologic analyses, immunogenetic associations and musculoskeletal imaging. Emphasis has centered previously on a dominant role for the T lymphocyte in the inflammatory process; however, studies provide support for a major contribution from monocyte-macrophages in the initiation and perpetuation of joint and skin inflammation. The occurrence of arthritis in the absence of psoriasis in a minority of patients with psoriatic arthritis, coupled with divergent genetic risk factors, indicates that psoriatic arthritis is distinct from psoriatic skin inflammation. A new terminology, psoriatic disease, has emerged that encompasses the various manifestations of tissue and organ involvement observed in many psoriasis patients, including inflammation in the joint, eye and gut. Moreover, adverse cardiovascular and metabolic outcomes in patients with psoriasis or psoriatic arthritis might be directly linked to the cutaneous and musculoskeletal manifestations of these diseases via subsets of circulating monocytes and tissue macrophages activated by inflammatory cytokine networks that arise in the skin and possibly the joint.

Joint remodelling in inflammatory disease

Bone and the immune system share multiple interactions. The skeleton harbours the bone marrow and provides the niche for development of haematopoietic cells including the immune system. The immune system provides cells as well as molecular signals, which regulate bone homeostasis. Understanding the cellular and molecular regulation of the tight interaction between bone and the immune system is crucial for understanding the changes of skeletal architecture during inflammation. Whereas a short and self-limited activation of the immune system has no clinically meaningful effect on bone, prolonged immune activation as found in chronic inflammatory disease inevitably leads to bone wasting.

Bone morphogenetic proteins in destructive and remodeling arthritis

Joint destruction and tissue responses determine the outcome of chronic arthritis. Joint inflammation and damage are often the dominant clinical presentation. However, in some arthritic diseases, in particular the spondyloarthritides, joint remodeling is a prominent feature, with new cartilage and bone formation leading to ankylosis and contributing to loss of function. A role for bone morphogenetic proteins in joint remodeling has been demonstrated in the formation of both enthesophytes and osteophytes. Data from genetic models support a role for bone morphogenetic protein signaling in cartilage homeostasis. Finally, this signaling pathway is likely to play a steering role in the synovium.

Mesenchymal stem cells in rheumatology: a regenerative approach to joint repair

The advent of biologics in rheumatology has considerably changed the evolution and prognosis of chronic inflammatory arthritis. The success of these new treatments has contributed to steering more attention to research focussed on repair and remodelling of joint tissues. Indeed, when the tissue damage is established, treatment options are very limited and the risk of progression towards joint destruction and failure remains high. Increasing evidence indicates that mesenchymal stem cells persist postnatally within joint tissues. It is postulated that they would function to safeguard joint homoeostasis and guarantee tissue remodelling and repair throughout life. Alterations in mesenchymal stem cell biology in arthritis have indeed been reported but a causal relationship has not been demonstrated, mainly because our current knowledge of mesenchymal stem cell niches and functions within the joint in health and disease is very limited. Nonetheless, mesenchymal stem cell technologies have attracted the attention of the biomedical research community as very promising tools to achieve the repair of joint tissues such as articular cartilage, subchondral bone, menisci and tendons. This review will outline stem-cell-mediated strategies for the repair of joint tissues, spanning from the use of expanded mesenchymal stem cell populations to therapeutic targeting of endogenous stem cells, resident in their native tissues, and related reparative signals in traumatic, degenerative and inflammatory joint disorders.

Osteochondral repair in synovial joints

PURPOSE OF REVIEW

One of the major challenges in rheumatology remains the induction of osteochondral repair in synovial joints. Remarkable progress has been made in controlling the inflammatory pathways of chronic synovitis and tissue damage in rheumatoid arthritis and spondyloarthropathy. Here, we provide an overview of the current knowledge on the mechanisms involved in osteochondral repair in degenerative joint diseases, as well as in immune mediated inflammatory arthritides, with special emphasis on tumor necrosis factor alpha and IL-1.

RECENT FINDINGS

Homeostasis of articular cartilage and subchondral bone are essential for maintaining the integrity of osteochondral structures within synovial joints. This is achieved by the regulation of a delicate balance between anabolic and catabolic signals. In articular cartilage one cell type, the chondrocyte, is responsible for regulation of homeostasis. In bone, however, two distinct cell types, osteoblasts and osteoclasts, are responsible for anabolic and catabolic pathways, respectively. In inflammatory joint disorders, this tight regulation is profoundly dysregulated, with tumor necrosis factor alpha acting as an important catalyst of a disturbed homeostasis, together with IL-1. Targeting these cytokines may restore the intrinsic repair capacity of osteochondral structures.

SUMMARY

To restore catabolic cytokine balances appears to be a suitable strategy to promote osteochondral repair.