osteoprotegerin and Spondylarthropathies

With the growing awareness of the impact of chronic back pain and axial spondyloarthritis and recent breakthroughs in genetics and the development of novel treatments which may impact best on early disease, the need for markers that can facilitate early diagnosis and profiling those individuals at the highest risk for a bad outcome has never been greater. The genetic basis of ankylosing spondylitis has been considerably advanced, and HLA-B27 testing has a role in the diagnosis. Knowledge is still incomplete of the rest of the genetic contribution to disease susceptibility, and it is likely premature to use extensive genetic testing (other than HLA-B27) for diagnosis. Serum and plasma biomarkers have been examined extensively in assessing disease activity, treatment response, and as predictors or radiographic severity. For assessing disease activity, other than C-reactive protein and erythrocyte sedimentation rate, the most work has been in examining cytokines (particularly interleukin 17 and 23), matrix metalloproteinase (MMP) markers (particularly MMP3). For assessing those at the highest risk for radiographic progression, biomarkers of bony metabolism, cartilage and connective tissue degradation products, and adipokines have been most extensively assessed. The problem is that no individual biomarkers has been reproducibly shown to assess disease activity or predict outcome, and this area still remains an unmet need, of relevance to industry stakeholders, to regulatory bodies, to the healthcare system, to academic investigators, and finally to patients and providers.

Topics: Adipokines; Aggrecans; Biomarkers; Bone and Bones; Cartilage; Cartilage Oligomeric Matrix Protein; Chitinase-3-Like Protein 1; Connective Tissue; Cytokines; Disease Progression; Genetic Markers; HLA-B27 Antigen; Humans; Lectins; Leukocyte L1 Antigen Complex; Matrix Metalloproteinases; Osteoprotegerin; Spondylarthropathies; Spondylitis, Ankylosing; Treatment Outcome

Bone loss is a common finding in the spondyloarthropathies. It may be localized and present as erosions or be generalized and cause osteoporosis. The pathogenesis of bone loss in the spondyloarthropathies is yet to be fully understood. There is however increasing evidence to support a role for the osteoclasts in bone erosions. Similarly a balance between the receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG) levels is thought to regulate osteoclastic activity and therefore bone loss in the inflammatory arthritides. In this chapter we will review the recent literature on the role of osteoclasts and the RANKL/OPG system in the various spondyloarthropathies and try to formulate a hypothesis for the possible mechanism of bone loss in this group of inflammatory rheumatic disease.

Topics: Animals; Bone Resorption; Cytokines; Humans; Osteoclasts; Osteoprotegerin; RANK Ligand; Receptor Activator of Nuclear Factor-kappa B; Signal Transduction; Spondylarthropathies

Rheumatoid arthritis, juvenile idiopathic arthritis, the seronegative spondyloarthropathies including psoriatic arthritis, and systemic lupus erythematosus are all examples of rheumatic diseases in which inflammation is associated with skeletal pathology. Although some of the mechanisms of skeletal remodeling are shared among these diseases, each disease has a unique impact on articular bone or on the axial or appendicular skeleton. Studies in human disease and in animal models of arthritis have identified the osteoclast as the predominant cell type mediating bone loss in arthritis. Many of the cytokines and growth factors implicated in the inflammatory processes in rheumatic diseases have also been demonstrated to impact osteoclast differentiation and function either directly, by acting on cells of the osteoclast-lineage, or indirectly, by acting on other cell types to modulate expression of the key osteoclastogenic factor receptor activator of nuclear factor (NF) kappaB ligand (RANKL) and/or its inhibitor osteoprotegerin (OPG). Further elucidation of the mechanisms responsible for inflammation-induced bone loss will potentially lead to the identification of novel therapeutic strategies for the prevention of bone loss in these diseases. In this review, we provide an overview of the cell types, inflammatory mediators, and mechanisms that are implicated in bone loss and new bone formation in inflammatory joint diseases.

Topics: Animals; Arthritis, Juvenile; Arthritis, Rheumatoid; Bone and Bones; Bone Remodeling; Bone Resorption; Carrier Proteins; Cytokines; Glycoproteins; Humans; Inflammation; Lupus Erythematosus, Systemic; Membrane Glycoproteins; Osteoclasts; Osteogenesis; Osteoprotegerin; Parathyroid Hormone-Related Protein; Prostaglandins; RANK Ligand; Receptor Activator of Nuclear Factor-kappa B; Receptors, Cytoplasmic and Nuclear; Receptors, Tumor Necrosis Factor; Signal Transduction; Spondylarthropathies

To demonstrate the expression of osteoprotegerin (OPG) and receptor activator of nuclear factor kappaB ligand (RANKL) in synovial tissue from rheumatoid arthritis (RA) patients, establish the cell lineage expressing OPG and compare the expression of OPG in RA, spondyloarthropathies, osteoarthritis and normal synovial tissue.. Synovial biopsy specimens were obtained at arthroscopy from 16 RA and 12 spondyloarthropathy patients with active synovitis of a knee joint, six RA patients with no evidence of active synovitis, 10 patients with osteoarthritis and 18 normal subjects. Immunohistological analysis was performed using monoclonal antibodies (mAb) to detect OPG and RANKL expression. In addition, dual immunohistochemical evaluation was performed with lineage-specific monoclonal antibodies (macrophages, fibroblasts and endothelial cells) and OPG to determine the cell lineages expressing OPG. The sections were evaluated by computer-assisted image analysis and semiquantitative analysis.. Two patterns of OPG expression were seen, one exclusively in endothelial cells and one expressed predominantly in macrophages in the synovial lining layer. Both patterns of OPG staining could be blocked with excess recombinant OPG. Endothelial and synovial lining expression of OPG was seen in all synovial tissues except those from patients with active RA. In contrast, RANKL expression was seen predominantly in synovial tissue from patients with active disease, mainly in sublining regions, particularly within areas of lymphocyte infiltration.. OPG expression on macrophage type synovial lining cells as well as endothelial cells is deficient in RA patients with active synovitis, in contrast to that seen in spondyloarthropathy patients with active synovitis. This deficiency in OPG expression in the inflamed joint of RA patients may be important in the development of radiologically defined joint erosions.

Topics: Acute Disease; Adult; Aged; Arthritis; Arthritis, Rheumatoid; Arthroscopy; Blotting, Western; Carrier Proteins; Case-Control Studies; Endothelium; Female; Glycoproteins; Humans; Image Processing, Computer-Assisted; Immunohistochemistry; Knee Joint; Macrophages; Male; Membrane Glycoproteins; Middle Aged; Osteoarthritis, Knee; Osteoprotegerin; RANK Ligand; Receptor Activator of Nuclear Factor-kappa B; Receptors, Cytoplasmic and Nuclear; Receptors, Tumor Necrosis Factor; Spondylarthropathies; Statistics, Nonparametric; Synovial Membrane

To compare receptor activator of NF-kappaB ligand (RANKL) production in the synovial tissue from patients with active rheumatoid arthritis (RA), inactive RA, spondyloarthropathies (SpA), osteoarthritis, and from normal subjects. In addition, to establish the cell lineages expressing RANKL in these tissues.. Immunohistological analysis of frozen synovial tissue biopsy specimens was performed using a monoclonal antibody (mAb) to detect RANKL. Sections were evaluated by computer assisted image analysis and semiquantitative analysis to compare RANKL expression between groups. Dual and sequential labelling with mAb RANKL and cell lineage specific monoclonal antibodies were used to determine the types of cells expressing RANKL.. Higher levels of RANKL were expressed in tissues from patients with active RA and SpA than in tissues from patients with inactive RA, osteoarthritis, and from normal subjects. RANKL protein was associated with CD3 antigen-positive lymphocytes and some macrophages. RANKL was predominantly associated with activated, memory T cells (CD45Ro positive cells) in patients with active RA and spondyloarthropathy (SpA).. The highest levels of RANKL were detected in patients with RA with active synovitis and in some patients with SpA. An increase in RANKL in the inflamed joint of patients with RA, produced by infiltrating activated T cells and macrophages, is likely to be an important cause of joint erosions in RA.

Topics: Adult; Aged; Arthritis, Rheumatoid; CD3 Complex; Female; Glycoproteins; Humans; Immunoenzyme Techniques; Leukocytes, Mononuclear; Lymphocytes; Macrophages; Male; Middle Aged; Osteoarthritis; Osteoprotegerin; Receptors, Cytoplasmic and Nuclear; Receptors, Tumor Necrosis Factor; Spondylarthropathies; Synovial Fluid