Arthritis Research & Therapy - Most viewed articles

Osteoarthritis is the most common degenerative disorder of the modern world. However, many basic cellular features and molecular processes of the disease are poorly understood. In the present study we used oligonucleotide-based microarray analysis of genes of known or assumed relevance to the cellular phenotype to screen for relevant differences in gene expression between normal and osteoarthritic chondrocytes. Custom made oligonucleotide DNA arrays were used to screen for differentially expressed genes in normal (n = 9) and osteoarthritic (n = 10) cartilage samples. Real-time polymerase chain reaction (PCR) with gene-specific primers was used for quantification. Primary human adult articular chondrocytes and chondrosarcoma cell line HCS-2/8 were used to study changes in gene expression levels after stimulation with interleukin-1β and bone morphogenetic protein, as well as the dependence on cell differentiation. In situ hybridization with a gene-specific probe was applied to detect mRNA expression levels in fetal growth plate cartilage. Overall, more than 200 significantly regulated genes were detected between normal and osteoarthritic cartilage (P < 0.01). One of the significantly repressed genes, Tob1, encodes a protein belonging to a family involved in silencing cells in terms of proliferation and functional activity. The repression of Tob1 was confirmed by quantitative PCR and correlated to markers of chondrocyte activity and proliferation in vivo. Tob1 expression was also detected at a decreased level in isolated chondrocytes and in the chondrosarcoma cell line HCS-2/8. Again, in these cells it was negatively correlated with proliferative activity and positively with cellular differentiation. Altogether, the downregulation of the expression of Tob1 in osteoarthritic chondrocytes might be an important aspect of the cellular processes taking place during osteoarthritic cartilage degeneration. Activation, the reinitiation of proliferative activity and the loss of a stable phenotype are three major changes in osteoarthritic chondrocytes that are highly significantly correlated with the repression of Tob1 expression.

The anti-PM/Scl autoantibodies are known to characterize a subset of autoimmune patients with myositis, scleroderma (Scl), and the PM/Scl overlap syndrome. The major autoantigens that are recognized by anti-PM/Scl autoantibodies are designated PM/Scl-100 and PM/Scl-75. These autoantigens have been reported to associate into a large complex consisting of 11 to 16 proteins and to play a role in ribosome synthesis. Recently, it was discovered that the PM/Scl complex is the human counterpart of the yeast (Saccharomyces cerevisiae) exosome, which is an RNA-processing complex consisting of 11 3' → 5' exoribonucleases. To date, 10 human exosome components have been identified, although only some of these were studied in more detail. In this review, we discuss some recent advances in the characterization of the PM/Scl complex.

IntroductionIn this study we aimed to investigate whether there are indications of premature atherosclerosis, as measured by endothelial dependent flow-mediated dilation (ED-FMD) and intima media thickness (IMT), in patients with very early RA, and to analyze its relation to biomarkers of endothelial dysfunction, taking inflammation and traditional cardiovascular disease (CVD) risk factors into account. Methods: Patients from the three northern counties of Sweden diagnosed with early RA are followed in an ongoing prospective study of CVD co-morbidity. Of these, all patients aged ≤60 years were consecutively included in this survey of CVD risk factors (n = 79). Forty-four age and sex matched controls were included. IMT of common carotid artery and ED-FMD of brachial artery were measured using ultrasonography. Blood was drawn for analysis of lipids, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (tPA)-mass, VonWillebrand factor (VWF), soluble intercellular adhesion molecule-1 (sICAM), soluble vascular cell adhesion molecule-1 (sVCAM), sE-selectin, sL-selectin and monocyte chemotactic protein-1 (MCP-1). In a subgroup of 27 RA patients and their controls the ultrasound measurements were reanalysed after 18 months. Results: There were no significant differences between RA patients and controls in terms of IMT or ED-FMD at the first evaluation. However after 18 months there was a significant increase in the IMT among the patients with RA (P < 0.05). Patients with RA had higher levels of VWF, sICAM-1 (P < 0.05) and of MCP-1 (P = 0.001) compared with controls. In RA, IMT was related to some of the traditional CVD risk factors, tPA-mass, VWF (P < 0.01) and MCP-1 and inversely to sL-selectin (P < 0.05). In RA, ED-FMD related to sL-selectin (P < 0.01). DAS28 at baseline was related to PAI-1, tPA-mass and inversely to sVCAM-1 (P < 0.05) and sL-selectin (P = 0.001). Conclusions: We found no signs of atherosclerosis in patients with newly diagnosed RA compared with controls. However, in patients with early RA, IMT and ED-FMD were, to a greater extent than in controls, related to biomarkers known to be associated with endothelial dysfunction and atherosclerosis. After 18 months, IMT had increased significantly in RA patients but not in controls.

This article has no abstract.

Statement of findingsThis study describes the upregulation of neurokinin 1 and bradykinin 2 receptors in dorsal root ganglion (DRG) neurons in the course of antigen-induced arthritis (AIA) in the rat knee. In the acute phase of AIA, which was characterized by pronounced hyperalgesia, there was a substantial bilateral increase in the proportion of lumbar DRG neurons that express neurokinin 1 receptors (activated by substance P) and bradykinin 2 receptors. In the chronic phase the upregulation of bradykinin 2 receptors persisted on the side of inflammation. The increase in the receptor expression is relevant for the generation of acute and chronic inflammatory pain.

Interstitial lung disease (ILD) is a challenging clinical entity associated with multiple connective tissue diseases, and is a significant cause of morbidity and mortality. Effective therapies for connective tissue disease-associated interstitial lung disease (CTD-ILD) are still lacking. Multidisciplinary clinics dedicated to the early diagnosis and improved management of patients with CTD-ILD are now being established. There is rapid progress in understanding and identifying the effector cells, the proinflammatory and profibrotic mediators, and the pathways involved in the pathogenesis of CTD-ILD. Serum biomarkers may provide new insights as risk factors for pulmonary fibrosis and as measures of disease progression. Despite these recent advances, the management of patients with CTD-ILD remains suboptimal. Further studies are therefore urgently needed to better understand these conditions, and to develop effective therapeutic interventions.

IntroductionThe glucocorticoid receptor (GR) plays an important regulatory role in the immune system. Four polymorphisms in the GR gene are associated with differences in glucocorticoid (GC) sensitivity; the minor alleles of the polymorphisms N363S and BclI are associated with relative hypersensitivity to GCs, while those of the polymorphisms ER22/23EK and 9beta are associated with relative GC resistance. Because differences in GC sensitivity may influence immune effector functions, we examined whether these polymorphisms are associated with the susceptibility to develop Rheumatoid Arthritis (RA) and RA disease severity. Methods: The presence of GR polymorphisms was assessed in healthy controls (n=5033), and in RA patients (n=368). A second control group (n=532) was used for confirmation of results. In RA patients, the relationship between GR polymorphisms and disease severity was examined. Results: Carriers of the N363S and BclI minor alleles had a lower risk of developing RA: odds ratio (OR)=0.55 (95% confidence interval (CI) 0.32-0.96, P=0.032) and OR=0.73 (95% CI 0.58-0.91, P=0.006), respectively. In contrast, 9beta minor allele carriers had a higher risk of developing RA: OR=1.26 (95% CI 1.00-1.60, P=0.050). For ER22/23EK minor allele carriers a trend to an increased risk OR=1.42 (95% CI 0.95-2.13, P=0.086) was found. All ER22/23EK carriers (32/32) had erosive disease, while only 77% (259/336) of the non-carriers did (P=0.008). In addition, ER22/23EK carriers were treated more frequently with anti-tumor necrosis factor-alpha (TNFalpha) therapy (P<0.05). Conclusions: The minor alleles of the 9beta and ER22/23EK polymorphisms seem to be associated with increased predisposition to develop RA. Conversely, the minor alleles of the N363S and BclI polymorphisms are associated with reduced susceptibility to develop RA. These opposite associations suggest that constitutionally determined GC resistance may predispose to development of auto-immunity, at least in RA, and vice versa.

The scientific and medical community remains skeptical regarding the efficacy of nutrition for osteoarthritis despite their broad acceptation by patients. In this context, this paper systematically reviews human clinical trials evaluating the effects of nutritional compounds on osteoarthritis. We searched the Medline, Embase, and Biosis databases from their inception to September 2005 using the terms random, double-blind method, trial, study, placebo, and osteoarthritis. We selected all peer-reviewed articles reporting the results of randomised human clinical trials (RCTs) in osteoarthritis that investigated the effects of oral interventions based on natural molecules. Studies on glucosamine and chondroitin sulfate were excluded. The quality of the RCTs was assessed with an osteoarthritic-specific standardised set of 12 criteria and a validated instrument. A best-evidence synthesis was used to categorise the scientific evidence behind each nutritional compound as good, moderate, or limited. A summary of the most relevant in vitro and animal studies is used to shed light on the potential mechanisms of action. Inclusion criteria were met by 53 RCTs out of the 2,026 identified studies. Good evidence was found for avocado soybean unsaponifiables. Moderate evidence was found for methylsulfonylmethane and SKI306X, a cocktail of plant extracts. Limited evidence was found for the Chinese plant extract Duhuo Jisheng Wan, cetyl myristoleate, lipids from green-lipped mussels, and plant extracts from Harpagophytum procumbens. Overall, scientific evidence exists for some specific nutritional interventions to provide symptom relief to osteoarthritic patients. It remains to be investigated whether nutritional compounds can have structure-modifying effects.

IntroductionHigh mobility group box 1 (HMGB1) is released by necrotic cells or secreted in response to inflammatory stimuli. Extracellular HMGB1 may act as a pro-inflammatory cytokine in rheumatoid arthritis. We have recently reported that HMGB1 is released by osteoarthritic synoviocytes after activation with interleukin-1beta (IL-1beta). The present study investigated the role of HMGB1 in synovial inflammation in osteoarthritis (OA). Methods: HMGB1 was determined in human synovium using immunohistochemistry, comparing normal to OA. OA synoviocytes were incubated with HMGB1 at 15 or 25 ng/ml in the absence or presence of IL-1beta (10 ng/ml). Gene expression was analyzed by quantitative PCR and protein expression by Western Blot and ELISA. Matrix metalloproteinase (MMP) activity was studied by fluorometric procedures and nuclear factor (NF)-kappaB activation by transient transfection with a NF-kappaB-luciferase plasmid. Results: In the normal synovium, HMGB1 was found in the synovial lining cells, sublining cells, and in the vascular wall cells. The distribution of HMGB1 in OA synovium was similar but the number of HMGB1 positive cells was higher and HMGB1 was also present in infiltrated cells. In normal synovial membrane cells, HMGB1 was found mostly in the nuclei, whereas in OA, HMGB1 was generally found mostly in the cytoplasm. In OA synoviocytes, HMGB1 alone at concentrations of 15 or 25 ng/ml did not affect the production of IL-6, IL-8, CCL2, CCL20, MMP-1 or MMP-3, but in the presence of IL-1beta, a significant potentiation of protein and mRNA expression, as well as MMP activity was observed. HMGB1 also enhanced the phosphorylated ERK1/2 and p38 levels, with a lower effect on phosphorylated Akt. In contrast, JNK1/2 phosphorylation was not affected. In addition, HMGB1 at 25 ng/ml significantly potentiated NF-kappaB activation in the presence of IL-1beta. Conclusions: Our results indicate that HMGB1 is overexpressed in OA synovium and mostly present in extracellular form. In OA synoviocytes, HMGB1 cooperates with IL-1beta to amplify the inflammatory response leading to the production of a number of cytokines, chemokines and MMPs. Our data support a pro-inflammatory role for this protein contributing to synovitis and articular destruction in OA.

IntroductionDiverse bone pathologies are observed in patients with psoriatic arthritis (PsA). Uncoupling of bone remodeling with disordered osteoclastogenesis has been implicated in the pathogenesis of PsA. The aim of this study was to examine the role of soluble mediators of bone remodeling within the circulation of patients with PsA. Methods: Patients with PsA (n=38), with psoriasis (n=10) and healthy controls (n=12) were studied. Serum was obtained for testing of Dikkopf-1 (Dkk-1), macrophage-colony stimulating factor (M-CSF), osteoprotegerin (OPG) and receptor activator of nuclear factor-kappaB ligand (RANKL) by ELISA. Patients with PsA also had bone densitometry, plain radiographs of the hands and feet, and assessment of peripheral blood osteoclast precursors. Radiographs were scored for erosion, joint space narrowing, osteolysis and new bone formation. Results: Compared with psoriasis and healthy controls, patients with PsA had higher circulating concentrations of Dkk-1 and M-CSF. In patients with PsA, M-CSF and RANKL, but not Dkk-1, concentrations positively correlated with radiographic erosion, joint space narrowing and osteolysis scores. Mediators of bone remodeling did not correlate with the number of joints with new bone formation or with total hip bone mineral density. Peripheral blood CD14+/CD11b+ cells, and the number of osteoclast-like cells and resorptive pits following culture with RANKL and M-CSF also correlated with radiographic damage scores. Circulating M-CSF concentrations correlated with the percentage of peripheral blood CD14+/CD11b+ cells. Conclusions: Systemic expression of soluble factors that promote osteoclastogenesis is disordered in patients with PsA, and may contribute to periarticular bone loss in this disease.