Whole-body cryotherapy for the treatment of rheumatoid arthritis: a monocentric, single-blinded, randomised controlled trial.

OBJECTIVES: To evaluate effects of whole-body cryotherapy (WBC) in rheumatoid arthritis (RA). METHODS: Patients with active RA undergoing a 16-day multimodal rheumatologic complex treatment were randomly assigned to either WBC (6 applications in 14 days at -130°C for 3 min) or no treatment. The primary outcome was the difference between groups in pain on a numerical rating scale after intervention. Secondary outcomes assessed effects on i) disease activity, ii) functional capacity, iii) cytokine levels, and iv) use of analgesics. RESULTS: A total of 56 RA patients completed the trial (intervention group [IG]: 31 patients, control group [CG]: 25 patients). The mean change (± standard error) in pain after intervention was -2 in the IG (95% confidence interval [CI] -2.75 to -1.31, p<0.001) and -0.88 (95% CI -1.43 to -0.33, p=0.003) in the CG, with a baseline-adjusted between-group difference of -1.31 ± 0.4 (95% CI -2.1 to -0.53; p=0.002). Pain at the 12-week follow-up visit remained significantly below baseline values in the IG. Disease activity and functional capacity showed statistically and clinically meaningful improvement after intervention but were not significant at the 12-week follow up. TNF and IL-6 levels changed significantly in the IG. Eighteen of 31 (58%) patients of the IG reduced or discontinued analgesics at the 12-week follow-up. No WBC-related side effects were reported. CONCLUSIONS: WBC in RA reduces pain and disease activity significantly and in a clinically meaningful manner, resulting in a reduction of analgesics. These effects are potentially based on a change in cytokine levels.

Treatment of back pain in active axial spondyloarthritis with serial locoregional water-filtered infrared A radiation: A randomized controlled trial.

BACKGROUND: Axial spondyloarthritis (axSpA) is an inflammatory rheumatic disease primarily affecting the axial skeleton. OBJECTIVE: To evaluate the short-term effects of locoregional water-filtered infrared A radiation (sl-wIRAR) in the treatment of lower back pain in patients with axSpA. METHODS: Patients with active axSpA with non-steroidal anti-inflammatory drug (NSAID) therapy undergoing a 7-day multimodal rheumatologic complex treatment in an in-patient setting were eligible. Patients were randomly assigned to the intervention group (IG) receiving sl-wIRAR treatment of the back (2 treatments/day for 30 min each for 6 days) or to the control group (CG) receiving no treatment. Primary outcome was a between-group difference in pain after sl-wIRAR therapy measured on a numeric rating scale (NRS) (0 = no pain, 10 = worst pain). Secondary outcomes included an assessment of i) the onset and development of analgesic effects and an evaluation of whether sl-wIRAR ii) improved axSpA-specific well-being and iii) influenced serum cytokine levels. RESULTS: Seventy-one patients were enrolled, completed the trial and were analyzed (IG: 36 patients, CG: 35 patients). In the IG, there was a statistically significant change (p< 0.0005) in pain level [NRS] (1.6 ± 1.9 [5; 2]) from baseline (4.1 ± 2.4 [0; 8]) to trial completion (2.6 ± 2.0 [0; 7]) and a significant difference to the CG (p= 0.006). In the IG there was a significant improvement in axSpA-specific well-being (BAS-G) (p= 0.006). A physiologically relevant change in serum cytokine levels could not be observed. CONCLUSION: sl-wIRAR treatment can be useful in the treatment of patients with active axSpA as it leads to a rapid reduction of pain.

Systemic versus local adipokine expression differs in a combined obesity and osteoarthritis mouse model.

Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage loss and reduced joint function. OA risk factors are age and obesity. Many adipokines are altered by obesity but also OA although systemic adipokine regulation in OA is not always clear. Therefore, metabolic effects of diet-induced obesity on OA development as well as the influence of obesity and OA progression on systemic vs. local adipokine expression in joints were compared. C57Bl/6-mice fed with HFD (high fat diet) or normal diet prior to destabilization of the medial meniscus (DMM) were sacrificed 4/6/8 weeks after surgery. Sera were evaluated for adiponectin, leptin, visfatin, cytokines. Liver grading and staging for non-alcoholic steatohepatitis (NASH) was performed and crown-like structures (CLS) in adipose tissue measured. OA progression was scored histologically. Adipokine-expressing cells and types were evaluated by immunohistochemistry. Time-dependent changes in DMM-progression were reflected by increased systemic adiponectin levels in DMM especially combined with HFD. While HFD increased serum leptin, DMM reduced systemic leptin significantly. OA scores correlated with bodyweight, leptin and hepatic scoring. Locally, increased numbers of adiponectin- and leptin-producing fibroblasts were observed in damaged menisci but visfatin was not changed. Local adipokine expression was independent from systemic levels, suggesting different mechanisms of action.

Compensation of Adiponectin-Induced Adenosine Monophosphate-Activated Protein Kinase and p38 Mitogen-Activated Protein Kinase Signaling in Rheumatoid Arthritis Synovial Fibroblasts.

Rheumatoid arthritis (RA) is a chronic inflammatory disorder marked by synovitis, ultimately leading to cartilage and bone destruction. In RA, adiponectin levels are increased in serum and synovial fluid. Adiponectin belongs to the adipokines, a group of highly bioactive substances secreted by adipocytes and other cell types. It has been shown to induce the production of proinflammatory and prodestructive factors by human RA synovial fibroblasts (RASF), suggesting a role in the pathophysiology of the disease. Although adenosine monophosphate-activated protein kinase (AMPK) and p38 mitogen-activated protein kinase (MAPK) are known to be involved in adiponectin signaling in RASF, no literature is available about whether the different adiponectin isoforms affect AMPK and p38 MAPK signaling in the same manner. In this study, we elucidated the signaling mechanisms in RASF, activated in response to selective stimulation with the 2 biologically most potent adiponectin isoforms, and possible approaches to inhibit adiponectin-mediated effects in RASF. All adiponectin isoforms induced p38 MAPK and AMPK phosphorylation to various degrees. Blocking AMPK activation increased p38 MAPK phosphorylation, while blocking p38 MAPK activation increased AMPK phosphorylation, both independent of the effect of adiponectin. Neither AMPKα1 nor AMPKα2 knockdown reduced interleukin (IL)-6/IL-8 release. Targeting transforming growth factor-activated kinase 1 (TAK1), a signaling molecule upstream of p38 MAPK, reduced the IL-6/IL-8 release. Taken together, our study showed that, in the case of adiponectin isoforms, inhibiting the p38 MAPK or the AMPK signaling pathway individually is not sufficient, probably due to compensatory interactions between these pathways. TAK1 might provide an alternative approach by ameliorating the proinflammatory effects of adiponectin in RA. Our results do not suggest that targeting individual adiponectin isoforms specifically in RA would provide a benefit over targeting adiponectin as a whole. However, whether targeting individual adiponectin isoforms would allow minimizing the loss of the beneficial effects of adiponectin within the metabolic and cardiovascular system still needs further investigation.

[The effect of obesity on disease activity of inflammatory rheumatic diseases]. / Der Einfluss von Adipositas auf die Krankheitsaktivität bei entzündlich rheumatischen Erkrankungen.

One of the most recent scientific fields is the interaction between the immune system and metabolic processes. These interactions increasingly involve intracellular and extracellular signaling molecules and their receptors as well as molecular mechanisms that are used by both systems. The result of these intensive interactions is characterized by the term "metaflammation" and involves in particular, the ubiquitous adipose tissue present throughout the body. The links identified to date between the immune system and metabolism play a greater role in inflammatory rheumatic joint diseases than previously thought. In general, a markedly high body mass index (BMI) in particular, is associated with increased inflammatory activity and this is independent of the underlying disease entity. A higher BMI at the beginning of an immunomodulatory therapy also causes a more difficult response to the medication. Thus, the current scientific objective is to identify the individual "immuno-metabolic" pathways in order to apply the medications specifically to the site of action. Furthermore, all newer therapeutic agents, especially those specifically acting against individual immunological molecules, should be systematically analyzed with respect to their metabolic concomitant effects and their influence on metabolic comorbidities.

Adipokines and Autoimmunity in Inflammatory Arthritis.

Adipokines are adipose tissue-derived factors not only playing an important role in metabolism but also influencing other central processes of the body, such as inflammation. In autoimmune diseases, adipokines are involved in inflammatory pathways affecting different cell types. Many rheumatic diseases belong to the group of autoimmune diseases, for example rheumatoid arthritis (RA) and psoriatic arthritis. Due to the autoimmune responses, a chronic inflammatory milieu develops, which affects the whole body, including adipose tissue. Metabolic alterations such as obesity influence inflammatory responses in autoimmune diseases. Adipokines are bioactive mediators mainly produced by adipose tissue. Due to alterations of systemic adipokine levels, their role as biomarkers with diagnostic potential has been suggested in the context of rheumatic diseases. In the affected joints of RA patients, different synoviocytes but also osteoclasts, osteoblasts, and chondrocytes produce several adipokines, contributing to the unique inflammatory microenvironment. Adipokines have been shown to be potent modulatory effectors on different cell types of the immune system but also local cells in synovial tissue, cartilage, and bone. This review highlights the most recent findings on the role of adipokines in the pathophysiology of inflammatory arthritis with a distinct focus on RA in the quickly developing research field.

Role of adipokines in systemic sclerosis pathogenesis.

Systemic sclerosis (SSc) is a chronic autoimmune connective tissue disease with manifestations in multiple organs, including the skin, lung, heart, joints, gastrointestinal tract, kidney, and liver. Its pathophysiology is characterized by inflammation, fibrosis, and vascular damage, with an increased expression of numerous cytokines, chemokines, and growth factors. However, besides these growth factors and cytokines, another group of molecules may be involved in the pathogenesis of SSc: the adipokines. Adipokines are proteins with metabolic and cytokine-like properties, which were originally found to be expressed by adipose tissue. However, their expression is not limited to this tissue, and they can also be found in other organs. Therefore, this review will describe the current knowledge regarding adipokines in the context of SSc and try to elucidate their potential role in the pathogenesis of SSc.

Adipokines and Inflammation Alter the Interaction Between Rheumatoid Arthritis Synovial Fibroblasts and Endothelial Cells.

Objective: The long-distance migration of rheumatoid arthritis synovial fibroblasts (RASFs) in the severe combined immunodeficiency (SCID) mouse model of rheumatoid arthritis (RA) suggests that an interaction between RASFs and endothelial cells (EC) is critical in this process. Our objective was to assess whether immunomodulatory factors such as adipokines and antirheumatic drugs affect the adhesion of RASFs to ECs or the expression of surface molecules. Methods: Primary ECs or human umbilical vein endothelial cell (HUVEC) and primary RASFs were stimulated with adiponectin (10 µg/mL), visfatin (100 ng/mL), and resistin (20 ng/mL) or treated with methotrexate (1.5 and 1,000 µM) and the glucocorticoids prednisolone (1 µM) and dexamethasone (1 µM), respectively. The expression of adhesion molecules was analyzed by real-time polymerase chain reaction. The interaction of both cell types was analyzed under static (cell-to-cell binding assay) and dynamic conditions (flow-adhesion assay). Results: Under static conditions, adipokines increased mostly binding of RASFs to EC (adiponectin: 40%, visfatin: 28%, tumor necrosis factor α: 49%). Under flow conditions, visfatin increased RASF adhesion to HUVEC (e.g., 0.5 dyn/cm2: 75.2%). Reduced adhesion of RASFs to E-selectin was observed after treatment with dexamethasone (e.g., 0.9 dyn/cm2: -40%). In ECs, tumor necrosis factor α (TNF-α) increased expression of intercellular adhesion molecule 1 (20-fold) and vascular cell adhesion molecule 1 (77-fold), whereas P-selectin was downregulated after stimulation with TNF-α (-6-fold). Conclusion: The adhesion of RASFs to EC was increased by visfatin under static and flow conditions, whereas glucocorticoids were able to decrease adhesion to E-selectin. The process of migration and adhesion of RASFs to ECs could be enhanced by adipokines via adhesion molecules and seems to be targeted by therapeutic intervention with glucocorticoids.

Free Fatty Acids in Bone Pathophysiology of Rheumatic Diseases.

Obesity-in which free fatty acid (FFA) levels are chronically elevated-is a known risk factor for different rheumatic diseases, and obese patients are more likely to develop osteoarthritis (OA) also in non-weight-bearing joints. These findings suggest that FFA may also play a role in inflammation-related joint damage and bone loss in rheumatoid arthritis (RA) and OA. Therefore, the objective of this study was to analyze if and how FFA influence cells of bone metabolism in rheumatic diseases. When stimulated with FFA, osteoblasts from RA and OA patients secreted higher amounts of the proinflammatory cytokine interleukin (IL)-6 and the chemokines IL-8, growth-related oncogene α, and monocyte chemotactic protein 1. Receptor activator of nuclear factor kappa B ligand (RANKL), osteoprotegerin, and osteoblast differentiation markers were not influenced by FFA. Mineralization activity of osteoblasts correlated inversely with the level of FFA-induced IL-6 secretion. Expression of the Wnt signaling molecules, axin-2 and ß-catenin, was not changed by palmitic acid (PA) or linoleic acid (LA), suggesting no involvement of the Wnt signaling pathway in FFA signaling for osteoblasts. On the other hand, Toll-like receptor 4 blockade significantly reduced PA-induced IL-8 secretion by osteoblasts, while blocking Toll-like receptor 2 had no effect. In osteoclasts, IL-8 secretion was enhanced by PA and LA particularly at the earliest time point of differentiation. Differences were observed between the responses of RA and OA osteoclasts. FFA might therefore represent a new molecular factor by which adipose tissue contributes to subchondral bone damage in RA and OA. In this context, their mechanisms of action appear to be dependent on inflammation and innate immune system rather than Wnt-RANKL pathways.

The Adipokine Network in Rheumatic Joint Diseases.

Rheumatic diseases encompass a diverse group of chronic disorders that commonly affect musculoskeletal structures. Osteoarthritis (OA) and rheumatoid arthritis (RA) are the two most common, leading to considerable functional limitations and irreversible disability when patients are unsuccessfully treated. Although the specific causes of many rheumatic conditions remain unknown, it is generally accepted that immune mechanisms and/or uncontrolled inflammatory responses are involved in their etiology and symptomatology. In this regard, the bidirectional communication between neuroendocrine and immune system has been demonstrated to provide a homeostatic network that is involved in several pathological conditions. Adipokines represent a wide variety of bioactive, immune and inflammatory mediators mainly released by adipocytes that act as signal molecules in the neuroendocrine-immune interactions. Adipokines can also be synthesized by synoviocytes, osteoclasts, osteoblasts, chondrocytes and inflammatory cells in the joint microenvironment, showing potent modulatory properties on different effector cells in OA and RA pathogenesis. Effects of adiponectin, leptin, resistin and visfatin on local and systemic inflammation are broadly described. However, more recently, other adipokines, such as progranulin, chemerin, lipocalin-2, vaspin, omentin-1 and nesfatin, have been recognized to display immunomodulatory actions in rheumatic diseases. This review highlights the latest relevant findings on the role of the adipokine network in the pathophysiology of OA and RA.

The activin-follistatin anti-inflammatory cycle is deregulated in synovial fibroblasts.

BACKGROUND: Activin A and follistatin exhibit immunomodulatory functions, thus affecting autoinflammatory processes as found in rheumatoid arthritis (RA). The impact of both proteins on the behavior of synovial fibroblasts (SF) in RA as well as in osteoarthritis (OA) is unknown. METHODS: Immunohistochemical analyses of synovial tissue for expression of activin A and follistatin were performed. The influence of RASF overexpressing activin A on cartilage invasion in a SCID mouse model was examined. RASF and OASF were stimulated with either IL-1ß or TNFα in combination with or solely with activin A, activin AB, or follistatin. Protein secretion was measured by ELISA and mRNA expression by RT-PCR. Smad signaling was confirmed by western blot. RESULTS: In human RA synovial tissue, the number of activin A-positive cells as well as its extracellular presence was higher than in the OA synovium. Single cells within the tissue expressed follistatin in RA and OA synovial tissue. In the SCID mouse model, activin A overexpression reduced RASF invasion. In human RASF, activin A was induced by IL-1ß and TNFα. Activin A slightly increased IL-6 release by unstimulated RASF, but decreased protein and mRNA levels of follistatin. CONCLUSION: The observed decrease of cartilage invasion by RASF overexpressing activin A in the SCID mouse model appears to be mediated by an interaction between activin/follistatin and other local cells indirectly affecting RASF because activin A displayed certain pro-inflammatory effects on RASF. Activin A even inhibits production and release of follistatin in RASF and therefore prevents itself from being blocked by its inhibitory binding protein follistatin in the local inflammatory joint environment.

Targeting Activated Synovial Fibroblasts in Rheumatoid Arthritis by Peficitinib.

Background: Synovial fibroblasts (SF) play a major role in the pathogenesis of rheumatoid arthritis (RA) and develop an aggressive phenotype destroying cartilage and bone, thus termed RASF. JAK inhibitors have shown to be an efficient therapeutic option in RA treatment, but less is known about the effect of JAK inhibitors on activated RASF. The aim of the study was to examine the effects of JAK inhibitors on activated RASF. Methods: Synovium of RA patients was obtained during knee replacement surgeries. Synoviocytes were isolated and pretreated with JAK inhibitors. Pro-inflammatory cytokines and matrix degrading proteinases were measured by ELISA in supernatant after stimulation with oncostatin M or IL-1ß. The proliferation of RASF was measured by BrdU incorporation. Cell culture inserts were used to evaluate cell migration. For adhesion assays, RASF were seeded in culture plates. Then, plates were extensively shaken and adherent RASF quantified. Cell viability, cytotoxicity and apoptosis were measured using the ApoTox-Glo™ Triplex and the CellTox™ Green Cytotoxicity Assay. Results: Tofacitinib and baricitinib decreased the IL-6 release of RASF stimulated with oncostatin M. JAK inhibition attenuated the IL-6 release of IL-1ß activated and with soluble IL-6 receptor treated RASF. In contrast, only peficitinib and filgotinib decreased the IL-6 release of RASF activated with IL-1ß. Peficitinib decreased also the MMP-3, CXCL8, and CXCL1 release at 5 µM. Moreover, peficitinib was the only JAK inhibitor suppressing proliferation of activated RASF at 1 µM. Peficitinib further decreased the migration of RASF without being cytotoxic or pro-apoptotic and without altering cell adhesion. Conclusions: JAK inhibitors effectively suppress the inflammatory response induced by oncostatin M and by transsignaling of IL-6 in RASF. Only peficitinib modulated the IL-1ß-induced response of RASF and their proliferation in vitro at concentrations close to reported Cmax values of well tolerated doses in vivo. In contrast to filgotinib, peficitinib also highly suppressed RASF migration showing the potential of peficitinib to target RASF.

Adipokine expression in systemic sclerosis lung and gastrointestinal organ involvement.

OBJECTIVES: The immunomodulatory properties of adipokines have previously been reported in autoimmune disorders. Less is known about the role of adipokines in systemic sclerosis (SSc). Lung and gastrointestinal tract are frequently involved in SSc; therefore, these organs were analyzed for adipokine expression as well as pulmonary samples of patients suffering from idiopathic pulmonary fibrosis (IPF) as comparison. METHODS: Gastric samples (antrum, corpus) of SSc were analyzed immunohistochemically for adiponectin, resistin and visfatin compared with non-SSc related gastritis. Inflammatory cells were quantified in gastric samples and correlated with adipokine expression. Lung samples of SSc, IPF and healthy controls were also analyzed. Protein levels of lung tissue lysates and bronchoalveolar lavages (BAL) in minor fibrotic stages were measured by ELISA. RESULTS: Lung sections of donor parenchyma showed significantly stronger adiponectin signals as IPF and SSc (donor vs. IPF: p < 0.0001). In SSc and IPF, resistin and visfatin were increased within immune cell infiltrates, but overall no difference in expression for resistin or visfatin compared to controls was observed. In BAL and lung protein lysates of early stages of fibrosis, adiponectin and visfatin were not reduced in IPF and SSc compared to controls. In gastric samples collected by standard endoscopic gastric biopsy, adiponectin was also significantly reduced in SSc- compared to non-SSc gastritis (p = 0.049) while resistin and visfatin were comparable although deeper fibrotic layers were not included in the respective samples. Adiponectin-positive tissues showed higher amounts of CD4+ but not CD8+ T cells. Controls showed no correlation between CD4+ T cells and resistin, whereas SSc showed significantly more CD4+ T cells in resistin-negative tissues. CONCLUSION: Adipokines are expressed in gastric and lung samples of patients with SSc and in lung samples affected by IPF. Prominently, adiponectin levels were reduced in fibrotic SSc gastritic tissue as well as in IPF and SSc lung tissue. Consequently, adiponectin expression seems to be associated with fibrotic progression in the context of SSc and IPF.

Interactions between rheumatoid arthritis synovial fibroblast migration and endothelial cells.

Leukocytes travel within the circulation and enter connective tissues by interactions with endothelium of postcapillary venules mediated by cell adhesion molecules, summarized as the leukocyte adhesion cascade. In the severe combined immunodeficient (SCID) mouse model, rheumatoid arthritis (RA) synovial fibroblasts (SF) migrated to distant cartilage through the vasculature. Therefore, RASF adhesion toward endothelial cells (EC) and E- and P-selectins were analyzed. Cell-to-cell binding assays between SF and EC were performed. Interactions of SF with tumor necrosis factor α (TNFα)-activated EC or selectins were analyzed in flow adhesion assays. Immunohistochemistry for E-selectin ligand CD15s was performed. CD15s induction in RASF by human serum or media was evaluated. Wild-type and E-/-/ P-/- Selectin-SCID mice were used for inverse-wrap surgery. After laser-mediated microdissection, real-time PCR for E-/P-selectin/vascular cell adhesion molecule 1 was performed. Adhesion between SF/EC under static conditions was highest in Roswell Park Memorial Institute-cultured RASF to TNFαα-activated human umbilical vein endothelial cells (2.25-fold) and RASF adhesion was higher toward venous than arterial EC (Dulbecco's modified eagle medium P = 0.0419, RPMI P = 0.0119). In flow chamber assays, RASF adhesion to E-selectin was higher than to P-selectin (e.g. 0.9 dyn cm-2 P = 0.0001). Osteoarthritis synovial fibroblasts showed lower rolling/adhesion properties (e.g. 0.5 dyn cm-2 , P = 0.0010). RASF adhesion to TNFαα-activated EC was increased (e.g. 0.9 dyn cm-2 , P = 0.0061). CD15s induction in RASF was strongest in RA serum. Vimentin/CD15s double-positive cells were detectable. In E-/P-selectin-deficient mice, contralateral invasion was reduced (P = 0.023). E- and P-selectin, and vascular cell adhesion molecule 1 expression in EC of implants was confirmed. Our data indicate that the milieu within vessels induces CD15s which enables RASF to interact with E-selectin/EC under flow. Therefore, RASF may migrate to distant sites and leave the vasculature similarly to leukocytes.

Response of human rheumatoid arthritis osteoblasts and osteoclasts to adiponectin.

OBJECTIVES: Adiponectin is an effector molecule in the pathophysiology of rheumatoid arthritis, e.g. by inducing cytokines and matrix degrading enzymes in synovial fibroblasts. There is growing evidence that adiponectin affects osteoblasts and osteoclasts although the contribution to the aberrant bone metabolism in rheumatoid arthritis is unclear. Therefore, the adiponectin effects on rheumatoid arthritis-derived osteoblasts and osteoclasts were evaluated. METHODS: Adiponectin and its receptors were examined in bone tissue. Primary human osteoblasts and osteoclasts were stimulated with adiponectin and analysed using realtime polymerase chain-reaction and immunoassays. Effects on matrix-production by osteoblasts and differentiation and resorptive activity of osteoclasts were examined. RESULTS: Immunohistochemistry of rheumatoid arthritis bone tissue showed adiponectin expression in key cells of bone remodelling. Adiponectin altered gene expression and cytokine release in osteoblasts and increased IL-8 secretion by osteoclasts. Adiponectin inhibited osterix and induced osteoprotegerin mRNA in osteoblasts. In osteoclasts, MMP-9 and tartrate resistant acid phosphatase expression was increased. Accordingly, mineralisation capacity of osteoblasts decreased whereas resorptive activity of osteoclasts increased. CONCLUSIONS: The results confirm the proinflammatory potential of adiponectin and support the idea that adiponectin influences rheumatoid arthritis bone remodelling through alterations in osteoblast and osteoclast.

Expression of adipokines in osteoarthritis osteophytes and their effect on osteoblasts.

OBJECTIVE: Osteophyte formation in osteoarthritis (OA) is mediated by increased osteoblast activity, which is -in turn- regulated by the Wnt signaling pathway. Obesity is regarded a risk factor in OA, yet little is known about the interaction between adipose tissue-derived factors, the adipokines, and bone formation, although adipokines are associated with the pathogenesis of OA. Therefore, the effect of adipokines on bone and cartilage forming cells and osteophyte development was analyzed. METHODS: Human OA osteophytes were histologically characterized and adipokine expression was evaluated by immunohistochemistry. Osteoblasts and chondrocytes were isolated from OA tissue and stimulated with adiponectin, resistin, or visfatin. Cytokine and osteoblast/chondrocyte markers were quantified and activation of Wnt and p38 MAPK signaling was analyzed. RESULTS: Adiponectin, resistin, and visfatin were expressed in OA osteophytes by various articular cell types. Stimulation of OA osteoblasts with adiponectin and of OA chondrocytes with visfatin led to an increased release of proinflammatory mediators but not to osteoblast differentiation or activation. Additionally, visfatin increased matrix degrading factors in chondrocytes. Wnt signaling was not altered by adipokines, but adiponectin induced p38 MAPK signaling in osteoblasts. CONCLUSION: Adipokines are present in OA osteophytes, and adiponectin and visfatin increase the release of proinflammatory mediators by osteoblasts and chondrocytes. The effects of adiponectin were mediated by p38 MAPK but not Wnt signaling in osteoblasts. Therefore, the results support the idea that adipokines do not directly influence osteophyte development but the proinflammatory conditions in OA.

Influence of Extracellular RNAs, Released by Rheumatoid Arthritis Synovial Fibroblasts, on Their Adhesive and Invasive Properties.

Extracellular RNA (exRNA) has been characterized as a molecular alarm signal upon cellular stress or tissue injury and to exert biological functions as a proinflammatory, prothrombotic, and vessel permeability-regulating factor. In this study, we investigated the contribution of exRNA and its antagonist RNase1 in a chronic inflammatory joint disease, rheumatoid arthritis (RA). Upon immunohistochemical inspection of RA, osteoarthritis (OA), and psoriatic arthritis synovium, exRNA was detectable only in the RA synovial lining layer, whereas extracellular DNA was detectable in various areas of synovial tissue. In vitro, exRNA (150-5000 nt) was released by RA synovial fibroblasts (RASF) under hypoxic conditions but not under normoxia or TNF-α treatment. RNase activity was increased in synovial fluid from RA and OA patients compared with psoriatic arthritis patients, whereas RNase activity of RASF and OASF cultures was not altered by hypoxia. Reduction of exRNA by RNase1 treatment decreased adhesion of RASF to cartilage, but it had no influence on their cell proliferation or adhesion to endothelial cells. In vivo, treatment with RNase1 reduced RASF invasion into coimplanted cartilage in the SCID mouse model of RA. We also analyzed the expression of neuropilins in synovial tissue and SF, as they may interact with vascular endothelial growth factor signaling and exRNA. The data support the concepts that the exRNA/RNase1 system participates in RA pathophysiology and that RASF are influenced by exRNA in a prodestructive manner.

The impact of serial radon and hyperthermia exposure in a therapeutic adit on pivotal cytokines of bone metabolism in rheumatoid arthritis and osteoarthritis.

Secondary osteoporosis is a frequent complication of rheumatoid arthritis (RA) and the result of an imbalance of catabolic and anabolic mechanisms of bone metabolism. The effects of serial low-dose radon and hyperthermia (LDRnHT) exposure in a therapeutic adit (12 applications in 3 weeks) on the serum levels of the cytokines osteoprotegerin (OPG), receptor activator of NF kappa-B ligand (RANKL), tumor necrosis factor-α (TNF-α), and also on the RANKL/OPG ratio were investigated in 25 RA patients and an age-matched control of 24 patients with osteoarthritis (OA). Cytokine measurements were performed at baseline and after completion of LDRnHT. Anti-CCP antibodies (ACPA) were measured in RA patients in parallel. Medication in both groups was limited to non-steroidal anti-inflammatory drugs, and low-dose prednisolone (16 of 24 RA patients) as needed. RA and OA patients showed a significant decrease of TNF-α levels (p < 0.001). Both groups showed significantly decreased levels of RANKL (RA: p < 0.001, OA: p < 0.01). Only the RA patients presented a significant increase of OPG (p < 0.01) and decrease of the RANKL/OPG ratio (p < 0.01), and the ACPA levels (p < 0.001). LDRnHT results in a reduction of osteocatabolic and an increase of osteoanabolic cytokines, which represents the molecular basis for inhibiting osteoclastic activity in secondary osteoporosis and explains in part the effect of LDRnHT this physical therapy modality in a key inflammatory disease. Although reduced ACPA levels were observed under the therapy and although this could potentially contribute to an osteoprotective effect, in this case, it is rather uncertain as the reduction was only minor in magnitude.