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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.

Eines der aktuellsten wissenschaftlichen Gebiete ist die Interaktion zwischen dem Immunsystem und metabolischen Vorgangen. In diese Interaktionen werden zunehmend intra- wie extrazellulare Signalmolekule und deren Rezeptoren sowie molekulare Mechanismen eingebracht, die von beiden Systemen, genutzt werden. Das Resultat hieraus wird durch den Begriff „Metaflammation“ charakterisiert und bezieht insbesondere auch das ubiquitar im Korper vorhandene Fettgewebe mit ein. Die bisher identifizierten Verbindungen zwischen Immunsystem und Metabolismus spielen eine grosere Rolle bei entzundlich rheumatischen Gelenkerkrankungen als bisher angenommen. Allgemein gilt, dass v. a. ein ausgepragt hoher Body-Mass-Index (BMI) mit einer erhohten Entzundungsaktivitat assoziiert ist, und dies unabhangig von der Grunderkrankung. Ein hoherer BMI zu Beginn einer Therapie bedingt auch ein schwierigeres Ansprechen auf die immunmodulatorische Medikation. Als aktuelle wissenschaftliche Zielsetzung ergibt sich hieraus, dass v. a. die individuellen „immunometabolischen“ Stoffwechselwege herausgearbeitet werden mussen, um die eingesetzten Medikamente zielgerichtet am Ort des Geschehens wirken zu lassen. Des Weiteren sollten alle neueren Therapeutika, insbesondere die spezifisch gegen einzelne immunologische Molekule wirkende, hinsichtlich ihrer metabolischen Begleiteffekte und ihres Einflusses auf metabolische Komorbiditaten systematisch analysiert werden.

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.

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.

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-1β 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-1β 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. Electronic supplementary material The online version of this article (10.1186/s13075-019-1926-7) contains supplementary material, which is available to authorized users.

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.

ZusammenfassungBei der Entstehung und dem Verlauf rheumatischer Erkrankungen spielen Adipositas, Metabolisches Syndrom (MetS) und Stoffwechselerkrankungen wie Diabetes eine wichtige Rolle. Wichtige Faktoren sind hierbei Fettgewebshormone wie z. B. Adiponektin und Leptin, aber auch andere biologisch aktive Faktoren des Metabolismus, wie die freien und gebundenen Fettsäuren im Blut und die Cholesterinwerte, welche den Krankheitsverlauf von Patienten mit rheumatischen Erkrankungen beeinflussen. Sowohl für Patienten mit rheumatoider Arthritis (RA) und Psoriasis-Arthritis (PsA) als auch für die nicht autoimmun beeinflusste Arthrose stellt Adipositas einen anerkannten Risikofaktor dar und ist somit von pathophysiologischer Bedeutung. Ein Einfluss auf das Ansprechen auf Medikamente wurde ebenso beobachtet. So erreichen übergewichtige PsA-Patienten, v. a. bei vermehrtem abdominalem Fett, unter TNFα-Blocker-Therapie mit geringerer Wahrscheinlichkeit eine minimale Krankheitsaktivität. In der Pathophysiologie rheumatischer Erkrankungen ist Fettgewebe außerdem wichtig als IL-6-Produzent, da IL-6 zu etwa einem Drittel im Fettgewebe produziert wird und eine Reduktion des Körpergewichts auch zur Reduktion des Serum-IL-6-Spiegels führt. Die Interaktion zwischen Immunsystem und biologisch aktiven Faktoren aus dem Metabolismus bei entzündlichen Erkrankungen funktioniert in beide Richtungen, wodurch die Wirknetzwerke sehr komplex werden. Der Entzündungsmarker C-reaktives Protein (CRP) bspw. bindet im Serum an Leptin und verhindert dadurch dessen Wirkung bzw. die Signalweiterleitung an die Zielzellen. Gleichzeitig fördert Leptin in der Leber die Bildung von CRP. Über diese gegenseitigen Einflüsse kann vermutlich CRP die Adipositas und deren Komorbiditäten beeinflussen. Der CRP-Spiegel korreliert aber auch negativ mit den HDL-Werten, und die Lipidwerte im Blut werden durch akute oder chronische Entzündung signifikant verändert. Auch die neuen Therapieansätze mit „Small Molecules“ wie z. B. Tofacitinib wirken sich nicht nur auf die Entzündung, sondern auch auf den Metabolismus aus. So wurde gezeigt, dass Patienten mit RA signifikant niedrigere Werte an Gesamtcholesterin, HDL-C, LDL-C und Apo-A1 im Vergleich zu gesunden Kontrollen aufweisen. Diese werden aber unter Behandlung mit Tofacitinib signifikant erhöht und nähern sich somit den Werten der gesunden Kontrollgruppe an.

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.

Background Rheumatoid arthritis (RA) and psoriatic arthritis (PsA), although similar in several respects, display clinical as well as therapeutic differences. This includes, for example, the higher effectiveness of the anti-IL17A biologic secukinumab in PsA than in RA patients. Synovial fibroblasts (SF) are one of the key effector cell types in the pathophysiology of RA and PsA. We hypothesized that RASF and PsASF respond differentially to IL-17A and its biologic secukinumab and that this might contribute to the difference seen in the therapeutic response. Objectives To examine the effect of the two cytokines IL-17A and TNF-α on RASF in comparison to PsASF as well as the effect of their corresponding biologics. To analyze the effect of the IL-17A homolog IL-17F. Methods SF were isolated from synovium from PsA or RA patients undergoing surgery. SF from RA and PsA patients were stimulated with recombinant IL-17A, IL-17F and TNF-α alone or with respective combinations. Dose-response curve analysis was performed with IL-17A. The biologics secukinumab and adalimumab were used to block the effects on the SF. As a measure of the proinflammatory response, secretion of the cytokine IL–6 was quantified using an immunoassay. Results IL-6 secretion was induced by IL-17A in RASF as well as PsASF (IL-17A: 13.7-fold ↑ vs 6.9–fold ↑; n=3). Although sharing the same receptor, the IL-17A homolog IL-17F alone caused no induction of IL-6 secretion in SF. However, when combined with TNF-α, both IL-17 isoforms, IL–17A and IL-17F, increased IL-6 secretion due to a strong synergistic effect with TNF-α. RASF (n=3) responded more strongly than PsASF (n=3) to the combined stimulation (IL-17A: 544-fold ↑ vs 127-fold ↑, IL-17F: 54-fold ↑ vs 27-fold ↑). Adalimumab and secukinumab were similarly effective in abolishing the synergistic effect of IL-17A + TNF-α in RASF and PsASF. Conclusion According to our data, the differences in the therapeutic effectiveness of the anti-IL17A biologic secukinumab cannot be attributed to differential SF responses since the response to IL-17A alone and IL-17A together with TNF–α is not stronger for PsASF than for RASF and since secukinumab was similarly effective for both SF types. Furthermore, in a proinflammatory milieu with increased TNF levels, both IL-17A and IL-17F can contribute to promoting inflammation in the pathophysiology of PsA and RA. Acknowledgement Supported by an unrestricted educational grant from Celgene GmbH. Disclosure of Interests Klaus Frommer: None declared, Stefan Rehart: None declared, Ulf Muller-Ladner Grant/research support from: Projekt supported by an unrestricted educational grant from Celgene GmbH., Elena Neumann: None declared

Background: Psoriatic arthritis (PsA) is frequently associated with enthesitis. It has been proposed that inflammatory processes at the synovio-enthesal complex are involved in the pathogenesis of inflammatory arthritides including especially PsA. Besides IL-1β and TNF-α, IL-15, IL-23 and IFN-γ are cytokines expressed within the synovium, tendons and entheses and some of which are already used as therapeutic targets. While synovial fibroblasts (SF) are known key effector cells of cartilage destruction in inflammatory arthritides such as RA, tenocytes are a major component of tendons and entheses and play a central role in tendon inflammation observed in PsA. Objectives: To investigate whether PsASF and tenocytes show significant interactions while being stimulated with the above cytokines alone as well as in combination with the aim to find out whether these may contribute to the pathogenesis of PsA. Methods: SF were isolated from patients with PsA undergoing joint surgery. Human tenocytes were acquired commercially and isolated from hamstring tendon tissue of patients undergoing hamstring tendon ACL reconstruction. PsASF and tenocytes were stimulated with IL-1β, TNF-α, IFN-γ, IL-15 and IL-23 alone and in combination. Direct cell co-culture experiments were performed at a 1:1 ratio of both cell types in parallel to experiments with single cell type cultures. IL-6 levels were measured by ELISA to quantify the immunological activation of the cells. Results: PsASF as well as tenocytes showed strong responses to IL-1β (tenocytes ↑173-fold, n=3; PsASF ↑56-fold, n=3) and TNF-α (tenocytes ↑10-fold, n=3; PsASF ↑9-fold, n=3) stimulation regarding IL-6 secretion. IFN-γ alone had only minimal effects on both cell types but acted synergistically when applied together with IL-1β (tenocytes ↑218-fold, n=3; PsASF ↑129-fold, n=3) and TNF-α (tenocytes ↑24-fold, n=3; PsASF ↑19-fold, n=3). IL-15 and IL-23 alone showed no effect but the data suggest a small antagonistic effect against IL-1β (tenocytes IL-15 ↓21%/IL-23 ↓27%, n=3; PsASF IL-23 ↓19%, n=3) and TNF-α induced IL-6 secretion. Overall, PsASF and tenocytes showed similar responses in the single cell type stimulation experiments. Co-culturing PsASF and tenocytes did not reveal any synergistic or antagonistic interactions in regards to any of the cytokines used. Conclusion: Our data suggest that tenocytes and PsASF do not interact in a way that would promote inflammation within the synovio-enthesal complex. Also, as far as the induction of IL-6 is concerned, PsASF and tenocytes are not major target cells of IL-15 and IL-23. IFN-γ, however, may be able to promote inflammation in combination with other cytokines in both cell types. Disclosure of Interests: Felix Dechant: None declared, Klaus Frommer: None declared, Neal L Millar: None declared, Iain McInnes Grant/research support from: AstraZeneca, Celgene, Compugen, Novartis, Roche, UCB Pharma, Consultant for: AbbVie, Celgene, Galvani, Lilly, Novartis, Pfizer, UCB Pharma, Stefan Rehart: None declared, Ulf Muller-Ladner Grant/research support from: Projekt supported by an unrestricted educational grant from Celgene GmbH., Elena Neumann: None declared

Background Osteoporosis (OP), as an age-related disease, is characterized by bone loss, increased fracture risk and poor regeneration. During aging and OP bone marrow adiposity is increased due to a shift of osteogenic towards adipogenic differentiation of bone marrow mesenchymal stem cells (MSC). The differentiation of MSC into adipocytes or osteoblasts is an important determinant of bone structural integrity. It is known, that fatty tissue not simply functions as energy storage but is metabolically highly active. Therefore, adipocyte-derived factors such as adipokines might influence MSC differentiation. Objectives The role of interactions between adipocyte-derived factors and MSC in the pathogenesis of OP is not fully elucidated. Thus, we analyzed the presence of the adipokine visfatin in bone tissue and its effects on MSC differentiation in standard culture vs. spongiosa. Methods The spongiosa of femoral heads of patients with osteoarthritis (OA) after hip replacement surgery, or after osteoporotic femoral neck fracture were used for RNA- and MSC-isolation. Adipogenic MSC differentiation was performed with/without visfatin and its inhibitor Apo866 as well as SB203580 p38-MAPK inhibitor. For the transfer and differentiation of MSC on cancellous bone, bone fragments were purified and sterilized. Gene expression was measured by Realtime PCR. Protein production was evaluated by ELISA. Results Elevated visfatin-level were observed in OP compared to non-osteoporotic OA bone. Visfatin-induced secretion of proinflammatory factors was lower during adipogenesis on cancellous bone then in standard cell culture (e.g. 14d IL6, x-fold: standard culture 151±110, spong. 40±30, n=7). Significantly elevated MMP13 mRNA as well as protein expression induced by visfatin could be detected during adipogenesis on spongiosa as well as in standard cell culture. However visfatin-mediated MMP13 expression was markedly reduced in the presence of cancellous bone (e.g. 21d, x-fold: standard culture 81±89, spong. 13±21, n=7). Inhibition of visfatin by Apo866 decreased the visfatin-induced cytokine release but not the MMP13 expression during adipogenesis in culture (n=4). In contrast to Apo866, the p38-MAPK inhibitor did not influence cytokine release but reduced MMP13 expression in a time dependent manner. Conclusion Visfatin level was elevated in osteoporotic vs OA bone. Therefore, visfatin-mediated increase of MMPs and proinflammatory cytokines during adipogenic differentiation might influence bone turnover at the adipose tissue/bone interface. Our results support the idea that the extracellular matrix attenuates visfatin-mediated detrimental effects during adipogenesis. The observed visfatin-mediated effects most likely depend on different signaling pathways. Disclosure of Interests Lali Tsiklauri: None declared, Janina Werner: None declared, Klaus Frommer: None declared, Stefan Rehart: None declared, Sabine Wenisch: None declared, Ulf Muller-Ladner Grant/research support from: supported by an unrestricted educational grant from Celgene GmbH., Elena Neumann: None declared

Career situation of first and presenting author Student for a master or a PhD. Introduction Osteoporosis (OP) is the most common age-related disorder characterized by bone loss and correlates with increased bone marrow adiposity due to a shift of osteogenic towards adipogenic differentiation of bone marrow mesenchymal stem cells (MSC). Therefore, bone marrow adipocytes are in direct contact with the altered bone matrix in OP. Adipose tissue is metabolically active. Therefore, adipocyte-derived factors such as adipokines might influence MSC differentiation. Objectives We analyzed the presence of adipokines (visfatin, resistin and leptin) in bone tissue and their effects on MSC differentiation under standard culture vs. spongiosa. Methods RNA and MSC were isolated from spongiosa of femoral heads of osteoarthritis patients after hip replacement surgery, or after osteoporotic femoral neck fracture. Adipogenic MSC differentiation was performed with/without adipokines and visfatin inhibitor Apo866 as well as SB203580 p38-MAPK inhibitor. For the transfer and differentiation of MSC on cancellous bone, bone fragments were purified and sterilized. Gene expression was evaluated by Realtime PCR. Protein production was analyzed by ELISA. Results Visfatin and leptin levels were increased in OP bone vs. non-osteoporotic OA bone, however, resistin was reduced. Visfatin induced the secretion of proinflammatory factors during adipogenesis in standard cell culture as well as on cancellous bone. Visfatin-induced cytokine release was markedly reduced during differentiation on spongiosa (e.g. 14d IL6, x-fold: standard culture 151±110, spong. 40±30, n=7). Significantly elevated MMP13 mRNA as well as protein expression induced by visfatin could be observed during adipogenesis in standard cell culture as well as on spongiosa, however visfatin-mediated MMP13 expression was reduced on cancellous bone (e.g. 21d, x-fold,: standard culture 81±89, spong. 13±21, n=7). The visfatin inhibitor Apo866 inhibited the visfatin-induced cytokine release. However, the MMP13 expression was not influenced during adipogenesis in culture (n=4). In contrast to Apo866, the p38-MAPK inhibitor did not reduce cytokine release during adipogenesis. Conclusions Visfatin and leptin levels were elevated in osteoporotic bone. Therefore, visfatin-mediated increase of MMPs and proinflammatory cytokines during adipogenic differentiation might influence bone turnover at the adipose tissue/bone interface. Our results support the idea that the extracellular matrix attenuates visfatin-mediated detrimental effects during adipogenesis. The observed visfatin-mediated effects most likely depend on different signaling pathways. Disclosure of Interest None declared.

Career situation of first and presenting author Student for a master or a PhD. Introduction Osteoarthritis (OA) and osteoporosis are destructive bone diseases causing chronic pain and leading to disability. Mesenchymal stromal cells (MSC) are essential to bone health and tissue repair. Adipokines such as visfatin alter the osteogenic potential of MSCs and contribute to the loss of bone homeostasis. Long non-coding RNA H19 is one of the first lncRNAs discovered and relevant for distinct processes, e.g. during embryonic growth and tumor formation. lncRNAs interact directly with DNA, RNA as well as proteins, modulating transcription, protein expression and protein function. H19 upregulation was shown in osteogenic differentiation of MSCs.1 H19 increases the osteogenic potential via TGFβ1 and Wnt/β-catenin pathways.2 3 Objectives To investigate the influence of visfatin on H19 expression during osteogenesis. Methods Human MSCs from healthy donors (hMSC) and primary human MSCs from osteoarthritis patients (phMSC) after knee replacement surgery were treated with differentiation medium to induce osteogenic differentiation (OD). Matrix mineralization (MM) was quantified after 21 days by Alizarin Red. H19 expression by realtime PCR and IL-6 production by ELISA were measured. Results lncRNA H19 was up-regulated during OD. Although the H19 upregulation was not altered by co-stimulation with resistin, leptin or TNFα, visfatin co-stimulation during OD down-regulated H19 expression up to 10-fold as compared to unstimulated MSCs. The effect was significant in phMSCs at two of three measured time points (day 7 p=0.03; day 14 p=0.002, n=3) and in hMSCs at day 14 (p=0.0003, n=4). Visfatin co-stimulation of MSCs in OD increased MM, as well as IL-6 levels. However, TNF did not alter H19 expression or increase MM. Conclusions Visfatin co-stimulation during osteogenesis down-regulated lncRNA H19 expression, indicating a loss of the growthpromoting effects of lncRNA H19 in affected areas of destructive bone disease. This regulatory effect was specific to visfatin and did not occur upon co-stimulation with other adipokines or inflammatory stimuli such as TNF supporting a TNF-independent effect of visfatin. References Wang, L. Differential expression of long noncoding ribonucleic acids during osteogenic differentiation of human bone marrow mesenchymal stem cells. Int. Orthop. 2015;39:1013–1019. Huang, Y. Long Noncoding RNA H19 Promotes Osteoblast Differentiation Via TGF-?1/Smad3/HDAC Signaling Pathway by Deriving miR-675. Stem Cells 2015;33:3481–3492. Liang, W.-C. H19 activates Wnt signaling and promotes osteoblast differentiation by functioning as a competing endogenous RNA. Sci. Rep. 2012;6:20121. Disclosure of Interest None declared.

Career situation of first and presenting author Post-doctoral fellow. Introduction Rheumatoid arthritis (RA) and psoriatic arthritis (PsA) are both rheumatic autoimmune diseases, which share a number of similarities but also display differences. For example, the anti-IL17A biologic secukinumab turned out to be more effective in PsA than in RA. The anti-TNF biologic adalimumab on the other hand is equally indicated for both diseases. Synovial fibroblasts (SF) are one of the key effector cell types in the pathophysiology of RA and PsA. Objectives We therefore investigated whether the effect of the two cytokines IL-17A and TNF-α as well as the effect of their corresponding biologics differs between RASF and PsASF, thus contributing to the difference seen in the therapeutic response. The effect of the IL-17A homolog IL-17F was also analyzed. Methods SF were isolated from patients with PsA or RA, each undergoing surgery. SF from RA and PsA patients were stimulated with recombinant IL-17A, IL-17F and TNF-α alone or with respective combinations. Dose-response curve analysis was performed with IL-17A. The biologics secukinumab and adalimumab were used to block the effects on the SF. As a measure of the proinflammatory response, secretion of the cytokine IL–6 was quantified using an immunoassay. Results RASF as well as PsASF responded to IL-17A (IL-17A: 13.7-fold vs 6.9–fold; n=3), while IL-17F alone caused no induction of IL-6 secretion in either SF type. However, when used in combination with TNF-α, both IL-17 isoforms, IL–17A and IL-17F, increased IL-6 secretion due to a strong synergistic effect with TNF-α. Surprisingly, these effects were notably stronger for RASF than for PsASF (IL-17A: 544-fold vs 127-fold, IL-17F: 54-fold vs 27-fold; n=3). However, adalimumab and secukinumab were similarly effective in abolishing the synergistic effect of IL-17A and TNF-α in RASF as well as PsASF. Conclusions SF appear not to contribute to the differences in the therapeutic effectiveness of the anti-IL17A biologic secukinumab as the response to IL-17A alone and IL-17A together with TNF–α is not stronger for PsASF than for RASF. Furthermore, secukinumab was similarly effective for both SF types. The data also suggest that in a proinflammatory milieu with increased TNF levels IL-17A as well as IL-17F play a role in the SF-mediated pathophysiology of PsA and, therefore, approaches targeting TNF are effective in both diseases. Acknowledgements Supported by an unrestricted educational grant from Celgene GmbH. Disclosure of Interest K. Frommer Grant/research support from: unrestricted educational grant from Celgene GmbH, S. Rehart: None declared, U. Muller-Ladner: None declared, E. Neumann: None declared.

Background:Activin A and follistatin belong to an anti-inflammatory auto-regulatory cycle. Patients with rheumatoid arthritis (RA) have increased activin A levels in the synovial fluid and tissue. During inflammation, activin A is released systemically, then inducing its antagonist follistatin. This negative feedback is active in different cell types but not RA synovial fibroblasts (SF). Fibroblasts interact with endothelial cells in inflamed tissues inducing angiogenesis.Objectives:Evaluation of the role of activin A and follistatin on RASF and endothelial cell interactions.Methods:RA synovium was used for RASF isolation, HUVEC were commercially obtained. RASF and HUVEC were stimulated in mono- and coculture. Direct: RASF together with HUVEC; indirect: inserts with HUVEC separated by a membrane from RASF. Stimuli: activin A 15ng/ml, follistatin 500ng/ml, IL-1β 1ng/ml. Proliferation was analyzed by BrdU assay. RASF were Calcein-AM stained. Cells were transferred to 24-well plates after 18h stimulation. After adhesion for 1h, non-adherent cells were removed by shaking 3x for 5 min. Afterwards, fluorescent cells were quantified. For the flow-adhesion assay, HUVEC were cultured on rattail collagen coated capillary slides. HUVEC and RASF were stimulated for 4h with TNFα, TNFα+activin A or TNFα+follistatin. After stimulation, 2x10^6 RASF were resuspended in 20ml medium and sent through the capillaries. Two 1min videos were recorded (18.4ml/h, 30.5ml/h). Settings: TNFα-stimulated RASF on HUVEC stimulated wit TNFα or activin A+TNFα or follistatin+ TNFα. For migration assays, 2% FCS medium with 1x10^5 cells were placed in inserts (8µm membrane) into wells with 10% FCS (control: 2%FCS vs. 2%FCS) and stimulated with, IL-1, IL-1+activinA and IL-1+follistatin. After 16h, migrated cells were quantified. For scratch-assay 4x10^5 cells were cultured overnight, then cells were scratched and stimulated, afterwards 3 pictures per scratch were taken at start, after 10h and every 1.5h. Cells migrating into the scratch area were quantified.Results:IL-1 induced activin A in RASF and HUVEC in all settings. IL-1-induced activin A release was reduced by follistatin in HUVEC monoculture and both cocultures compared to IL-1 alone but not in RASF monoculture. IL-1-induced IL-6 release was reduced by activin A in HUVEC and indirect coculture but not in RASF monoculture and direct coculture. Follistatin did not alter IL-6 responses. IL-1 induced VEGF in RASF but not in HUVEC and was not altered by activin A. Short-term adhesion showed no significant influence of activin A or follistatin (n=4). Flow adhesion assay showed reduced adherence/rolling of RASF on HUVEC stimulated with TNFα and activin A (n=4). Migration assays showed that IL-1 decreased migration but without significant difference between the induced effects mediated by IL-1+activinA and IL-1+follistatin (n=4). Scratch assay showed increased migration in dicrect coculture with greater difference between stimulated and unstimulated cells in RASF monoculture and indirect coculture (n=4). Proliferation was not altered by activin A or follistatin.Conclusion:In direct and indirect coculture of HUVEC with RASF the effect on HUVEC was dominant leading to reduced IL-1-induced activin A release. However, the IL-1-induced IL-6 release in RASF or HUVECs was decreased by activin A in HUVEC monoculture and indirect coculture but not during cell-contact between both cell types. The direct interaction of RASF with HUVEC seems to prevent the reducing activin A effect on IL-6 release in HUVECs. Activin A seems to not to have an impact on short-term cell adhesion but first observations show, that activin A alters selectin-mediated adhesion under flow conditions. The migration assay shows that IL-1-induced effects on cell migration were enhanced by activin A and follistatin. Migration assay shows that IL-1-induced decrease on migration more prominent in indirect coculture and RASF monoculture than in direct coculture although in gap migration in the scratch assay was highest in direct coculture.Disclosure of Interests:None declared

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.

Microscopic fractures (so-called microcracks) or traumatic macrofractures require bone, as the basic scaffold of the human body, to have a high regenerative capability. In order to be able to provide this regenerative capability, bone is in a constant process of remodeling. This finely tuned homeostasis of bone formation and degradation can become disrupted, which leads to osteoporosis or other bone disorders. It has been shown that the immune system is substantially involved in the regulation of bone homeostasis and that chronic inflammation in particular can disturb this balance; therefore, this article reviews the osteoimmunological aspects contributing to osteoporosis and other diseases associated with bone degradation.

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

Objective Osteoarthritis is not only characterized by cartilage degradation but also involves subchondral bone remodeling and osteophyte formation. Osteophytes are fibrocartilage-capped bony outgrowths originating from the periosteum. The pathophysiology of osteophyte formation is not completely understood. Yet, different research approaches are under way. Therefore, a histological osteophyte classification to achieve comparable results in osteophyte research was established for application to basic science research questions. Methods The osteophytes were collected from knee joints of osteoarthritis patients ( n = 10, 94 osteophytes in total) after joint replacement surgery. Their size and origin in the respective joint were photo-documented. To develop an osteophyte classification, serial tissue sections were evaluated using histological (hematoxylin and eosin, Masson's trichrome, toluidine blue) and immunohistochemical staining (collagen type II). Results Based on the histological and immunohistochemical evaluation, osteophytes were categorized into four different types depending on the degree of ossification and the percentage of mesenchymal connective tissue. Size and localization of osteophytes were independent from the histological stages. Conclusion This histological classification system of osteoarthritis osteophytes provides a helpful tool for analyzing and monitoring osteophyte development and for characterizing osteophyte types within a single human joint and may therefore contribute to achieve comparable results when analyzing histological findings in osteophytes.

Background:Long non-coding (lnc-)RNA are regulatory molecules transcribed from DNA similar to mRNA and interact directly with DNA, RNA and proteins. Some lncRNAs have been shown to contain micro (mi-)RNAs in their sequence that can be released by splicing and lead to active miRNA molecules, e.g. lncRNA H19 includes two miRNAs 675-3p and -5p in its sequence.Adipose tissue derived factors (adipokines) are involved in inflammation processes and osteoarthritis (OA) development. The proinflammatory adipokine visfatin has been shown to alter osteogenic differentiation (OD) of pluripotent mesenchymal stem cells (MSCs) and reduces elastic fiber expression, increases matrix mineralization and proinflammatory cytokine and chemokine production(1).Objectives:We evaluated a novel effect of visfatin on lncRNA H19 in MSCs during OD. The goal was to explore the kinetics of the visfatin effect during OD with regard to H19 regulation and to investigate H19 downstream mechanisms leading to the observed altered MSC differentiation and osteoblast activity.Methods:MSCs isolated from OA hip or knee bone (phMSC) and commercially obtained healthy human (h-)MSCs were differentiated towards osteoblasts with/without visfatin, resistin, leptin, TNF and Wnt/TGFβ1 pathway inhibitors. Supernatants were collected at days 2, 7, 9, 14 and 21 of OD, cell lysates at day 2, 7, 9, 14 and matrix mineralization assays conducted at day 21. H19 and miRNA expression was evaluated by real-time PCR after mi-/RNA isolation. IL-6 was analyzed by ELISA.Results:H19 was continuously upregulated in unstimulated controls as expected during OD but also when stimulated with other adipokines. In contrast, stimulation with visfatin significantly decreased H19 (day 2 to 14 of OD, hip-phMSCs: p = 0.0097, knee-phMSCs: p=0.0075, h-MSC: p = 0.044). Visfatin increased matrix mineralization and IL-6 production as expected (hMSC: p = 0.03, phMSC: p = 0.013)(1). TNF stimulation during OD did not lead to a downregulation of H19 nor increased matrix mineralization, thus showing that the effects were visfatin-dependent. H19s endogenous miRNA 675-5p was changed in parallel with H19, increased during control OD and significantly down-regulated by visfatin (e.g. day 14 p = 0.015). However, H19s endogenous miRNA 675-3p was inversely regulated, downregulated during control OD while visfatin stimulation attenuated this effect (e.g. day 14 p = 0.025). Altered Wnt-signaling and involvement of the TGFβ1 pathway could not be observed.Conclusion:H19 is upregulated during OD and may therefore play a regulatory role in the process of osteogenesis. Visfatin stimulation of MSCs during OD showed pro-inflammatory effects, increased matrix mineralization while reducing elastic fiber production(1). These effects were associated with a downregulation of H19, a specific visfatin effect not triggered by other adipokines or TNF. The H19 sequence includes two endogenous micro-RNAs 675-3p and 5p. We demonstrated miRNA 675-5p to be regulated in parallel to H19, whereas miRNA 675-3p was inversely regulated and increased continuously upon visfatin stimulation. Based on these results, we hypothesize that visfatin provides a specific stimulus for the splicing of miRNA 675-3p from H19, in turn leading to H19 reduction. miRNA 675-3p thus represents an effector mechanism of visfatin that contributes to the observed functional effects in differentiating MSCs.References:[1]Tsiklauri, L.et al.Visfatin alters the cytokine and matrix-degrading enzyme profile during osteogenic and adipogenic MSC differentiation.Osteoarthr. Cartil.26, 1225–1235 (2018).Disclosure of Interests:Dennis Küppers: None declared, Lali Tsiklauri: None declared, Marie Hülser: None declared, Klaus Frommer: None declared, Stefan Rehart: None declared, Caroline Ospelt Consultant of: Consultancy fees from Gilead Sciences., Ulf Müller-Ladner Speakers bureau: Biogen, Elena Neumann: None declared

Background Although rheumatoid arthritis (RA) and psoriatic arthritis (PsA) have several features in common, they also possess distinct differences. We hypothesised that RA and PsA synovial fibroblasts (SF), known key effector cells in the pathophysiology of inflammatory arthritis, differentially respond to various stimuli including adipokines and cytokines and that this may contribute to those differences. For example, IL-17 (also found in synovial tissue) is of particular therapeutic significance in PsA but not as effective in RA. Thus far, IL-17 in its isoform IL-17A has been the major therapeutic target in PsA but IL-17F also plays a role in the IL-23/IL-17 axis of inflammatory diseases. Objectives Therefore, we analysed the responses of SF from patients with PsA, RA or no rheumatic disease to IL-17A/F±TNF-α and the adipokines visfatin and resistin, which show strong expression in the synovium of inflammatory arthritis. Methods SF were isolated from patients with PsA, RA or non-rheumatic disease controls (N), each undergoing joint surgery. PsASF, RASF and NSF were stimulated with human recombinant IL-17A/F, TNF-α, visfatin, and resistin. A neutralising anti-IL-17A antibody was used to verify specificity of the IL-17A effects. Secretion of the proinflammatory cytokine IL-6 was used as the initial readout parameter and was quantified using a commercial immunoassay. Results Stimulation with visfatin caused a strong increase in IL-6 secretion in all SF types (n=3 each), while resistin had no effect. Differences in responses were not statistically significant between the SF types studied. IL-17A at concentrations found in serum or synovial fluid did not induce IL-6 secretion in any of the SF. Dose-response curve analysis showed that considerably higher concentrations of IL–17A, which may occur locally in tissue, are required for the induction of IL-6 secretion. An anti-IL–17A antibody abolished the effect, thus showing that the effect is specific for IL-17A. The effects of IL-17A and IL–17F on IL-6 secretion by PsASF could be strongly amplified by a co–stimulation with TNF-a (IL-17A: 5-fold vs 113-fold; IL-17F: 1.7-fold vs 39-fold; TNF-α alone: 12-fold). The effects were stronger for IL-17A than for IL–17F with or without TNF co–stimulation. No effect of IL–17F alone was observed on NSF (n=1). Conclusions SF from RA and PsA patients were not differentially affected by the adipokines visfatin and resistin or IL-17A when used at serum or synovial fluid concentrations suggesting inflammatory cells to be the primary target of anti-IL-17 therapy. In its use as a therapeutic target, the attribute of IL-17F affecting PsASF would potentially increase the beneficial effects. Acknowledgements This work was supported by an unrestricted educational grant from Celgene GmbH. Disclosure of Interest K. Frommer Grant/research support from: unrestricted educational grant from Celgene GmbH, S. Rehart: None declared, M. Sauerbier: None declared, U. Muller-Ladner: None declared, E. Neumann: None declared

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.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.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 CD4Adipokines 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.

Introduction Osteoporosis predominantly affects elderly people and is characterised by bone loss, increased fracture risk and reduced regeneration ability. Age-related bone loss correlates with increased bone marrow adiposity due to a shift of osteogenic towards adipogenic differentiation of bone marrow-derived mesenchymal stem cells (MSC). Adipose tissue is metabolically active. Through the release of adipokines with immunomodulatory properties adipose tissue might influence differentiation of bone marrow-derived MSC and contribute to bone loss in osteoporosis. Objectives Thus we analysed the presence of adipokines (visfatin, resistin and leptin) in the bone marrow cavity and their effects on MSC differentiation. Methods MSC and RNA were isolated out of spongiosa from femoral heads (hip replacement surgery of osteoarthritis patients (OA) or after osteoporotic femoral neck fracture (FF). Adipogenic as well as osteogenic MSC differentiation was performed with/without adipokines. For the transfer and differentiation of MSC on cancellous bone, cell-free bone fragments were prepared and sterilised. Proinflammatory factors were measured by immunoassays. Gene expression was evaluated by Realtime PCR. Matrix mineralization was assayed using Alizarin red S staining. Results While resistin was reduced, visfatin and leptin levels were increased in FF bone vs. non-osteoporotic OA bone (FF mean visfatin 7.77±1.86, n=11; OA 2.25±0.36, n=13, p=0.002). In contrast to leptin and resistin, visfatin induced the secretion of proinflammatory factors (IL-6, IL-8, MCP-1) during both, osteogenic and adipogenic differentiation, (e.g. adipogenic differentiation IL-6, 21d; control: 270.3±140.2 pg/ml; visfatin: 3,223±600.4 pg/ml, p=0.0006, n=12). In osteogenically differentiated cells matrix mineralization was significantly increased, while collagen type 1 expression was downregulated (d21: −4.2-fold/p=0.0001; n=7) after visfatin stimulation. The expression of MMP2, −13, TIMP1 and −2 (e.g. d21: −2.4-fold; −3.2-fold; −3.2-fold; −4.3 fold, respectively) was also reduced by visfatin during osteogenesis. Interestingly, visfatin significantly induced MMP13 expression (e.g. d21: 104-fold) during adipogenic differentiation under cell culture conditions. However, when differentiated on autologous cancellous bone, visfatin-induced MMP13 expression, as well as IL-6 and IL-8 release was markedly reduced (e.g. MMP13 21d: 13.8-fold, p=0.0156, n=7). Conclusions Taken together, visfatin expression was not only elevated in osteoporotic bone, it induced release of proinflammatory factors and dysregulated the MMP/TIMP balance during MSC-differentiation. Therefore visfatin might influence bone remodelling specifically at the bone/adipose tissue interface. The visfatin-mediated increase of matrix mineralization and the observed reduction of organic component of ECM – Coll.1, essential for the bone plasticity might contribute to bone fragility and therefore to the pathogenesis of osteoporosis. Disclosure of interest None declared

Resume Objectif L’arthrose est non seulement caracterisee par une degradation du cartilage, mais comporte egalement un remodelage de l’os sous-chondral et la formation d’osteophytes. Les osteophytes sont des excroissances osseuses coiffees de fibrocartilage provenant du perioste. La physiopathologie de la formation d’osteophytes n’est pas completement comprise. Pourtant, differentes voies de recherche sont en cours. Par consequent, une classification histologique des osteophytes en vue d’obtenir des resultats comparables de la recherche sur les osteophytes a ete creee en vue d’une application aux questions de recherche fondamentale. Methodes Les osteophytes ont ete recueillis sur des genoux de patients souffrant d’arthrose ( n = 10 ; 94 osteophytes au total) apres mise en place d’une prothese. Leur taille et origine dans leur articulation respective furent documentees par photographies. Afin de developper une classification des osteophytes, des coupes seriees de tissus furent effectuees en utilisant des colorations histologiques (hematoxyline-eosine, trichrome de Masson, bleu de toluidine) et immunohistochimiques (collagene de type II). Resultats En fonction d’une evaluation histologique et immunohistochimique, les osteophytes furent classes en quatre types differents selon leur degre d’ossification et le pourcentage de tissu conjonctif mesenchymateux. La taille et la situation des osteophytes etaient independantes des stades histologiques. Conclusion Ce systeme de classification histologique des osteophytes arthrosiques fournit un outil utile pour l’analyse et le suivi du developpement des osteophytes et pour caracteriser le type d’osteophyte dans une seule articulation humaine. Il peut donc contribuer a obtenir des resultats comparables lors de l’analyse histologique des osteophytes.

Objective Adipokines have metabolic and inflammatory functions but can also affect bone metabolism. The purpose of this study was to determine the relationship between serum levels of adiponectin, resistin, and visfatin and markers of inflammation, disease activity, and radiographic spinal progression in patients with ankylosing spondylitis (AS). Methods Levels of adiponectin, resistin, and visfatin in the serum of 86 AS patients and 25 healthy controls were measured by enzyme-linked immunosorbent assay at baseline. Radiographic spinal progression was determined by the scoring of radiographs of the spine obtained at baseline and after 2 years. Results Mean (±SD) baseline levels of resistin and visfatin were significantly higher in AS patients than in healthy controls (11.6 ± 10.6 ng/ml versus 6.6 ± 3.2 ng/ml [P = 0.01] for resistin, and 20.9 ± 48.3 ng/ml versus 3.4 ± 2.6 ng/ml [P = 0.001] for visfatin). Adipokine serum levels did not correlate with disease activity or functional indices. Only resistin serum levels correlated with markers of inflammation. Baseline levels of visfatin, but not resistin or adiponectin, were significantly higher in patients with worsening of the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS) by ≥2 units after 2 years (n = 19) as compared to patients without mSASSS worsening (37.7 ± 57.8 ng/ml versus 16.1 ± 44.6 ng/ml; P = 0.029) and in patients with syndesmophyte formation/progression (n = 22) as compared to patients without such progression (37.1 ± 55.3 ng/ml versus 15.3 ± 44.8 ng/ml; P = 0.023). Visfatin levels of >8 ng/ml at baseline were predictive of subsequent radiographic spinal progression (adjusted odds ratio 3.6 for mSASSS progression and 5.4 for syndesmophyte formation/progression). Conclusion Serum levels of resistin and visfatin are elevated in AS patients. Elevated visfatin levels at baseline are predictive of subsequent progression of radiographic damage in AS patients.

Summary Objectives Age-related bone loss is associated with bone marrow adiposity. Adipokines (e.g., visfatin, resistin, leptin) are adipocyte-derived factors with immunomodulatory properties and might influence differentiation of bone marrow-derived mesenchymal stem cells (MSC) in osteoarthritis (OA) and osteoporosis (OP). Thus, the presence of adipokines and MMPs in bone marrow and their effects on MSC differentiation were analyzed. Methods MSC and ribonucleic acid (RNA) were isolated from femoral heads after hip replacement surgery of OA or osteoporotic femoral neck fracture (FF) patients. Bone structural parameters were evaluated by microcomputed tomography (μCT). MSC were differentiated towards adipocytes or osteoblasts with/without adipokines. Gene expression (adipokines, bone marker genes, MMPs, TIMPs) and cytokine production was evaluated by realtime-polymerase chain reaction (realtime-PCR) and enzyme-linked immunosorbent assay (ELISA). Matrix mineralization was quantified using Alizarin red S staining. Results μCT showed an osteoporotic phenotype of FF compared to OA bone (reduced trabecular thickness and increased ratio of bone surface vs volume of solid bone). Visfatin and leptin were increased in FF vs OA. Visfatin induced the secretion of IL-6, IL-8, and MCP-1 during osteogenic and adipogenic differentiation. In contrast to resistin and leptin, visfatin increased MMP2 and MMP13 during adipogenesis. In osteogenically differentiated cells, MMPs and TIMPs were reduced by visfatin. Visfatin significantly increased matrix mineralization during osteogenesis, whereas collagen type I expression was reduced. Conclusion Visfatin-mediated increase of matrix mineralization and reduced collagen type I expression could contribute to bone fragility. Visfatin is involved in impaired bone remodeling at the adipose tissue/bone interface through induction of proinflammatory factors and dysregulated MMP/TIMP balance during MSC differentiation.

To the Editor: In the past several years, adipokines have gained a lot of attention in the field of rheumatic diseases1. Rheumatoid arthritis (RA), for example, is associated with an altered production of adipokines1, and there is some evidence of involvement of adipokines in the pathophysiology of RA as suggested by in vitro 1 and in vivo data2,3. The term “adipokines” was originally used to describe cytokine-like factors secreted by adipose tissue, but it turned out that many adipokines are also produced at other sites including the joints1,4,5, where they might have an influence on effector cells of RA or osteoarthritis (OA) pathophysiology. As an adipokine, omentin was first found in omental adipose tissue from patients with Crohn disease6. Before this, it was identified as a secretory glycoprotein able to bind to galactofuranosyl residue on various microorganisms, suggesting a function in immune recognition of certain pathogens. It has also been described as a lactoferrin-binding protein with lactoferrin being a protein with multiple immunological functions. Omentin is highly abundant in human plasma6. It displayed antiinflammatory and antiatherogenic properties in obese patients7 … Address correspondence to Dr. K.W. Frommer, Department of Internal Medicine and Rheumatology, University of Giessen, Kerckhoff Clinic, Benekestrasse 2-8, D-61231 Bad Nauheim, Germany. E-mail: k.frommer{at}kerckhoff-klinik.de

Background Various inflammatory cardiovascular and metabolic diseases such as atherosclerosis, coronary heart diseases and type 2 diabetes are associated with chronically elevated free fatty acid (FFA) levels. With inflammation being a factor in pathological bone loss, FFA may also be contributors to bone loss in osteoarthritis (OA) and/or rheumatoid arthritis (RA). Objectives To investigate whether FFA have an influence on osteoblasts and osteoclasts from patients with RA or OA, in a way that may alter bone degradation in these diseases. Methods Primary osteoblasts (OB) were isolated from cancellous bone of OA and RA patients undergoing knee joint surgery. Osteoclasts (OC) were differentiated from peripheral blood mononuclear cells (PBMC). OB and OC were stimulated with the saturated FFA palmitic acid (PA) and the unsaturated FFA linoleic acid (LA) (100 μM each). Immunoassays were used to quantify protein secretion. mRNA expression levels were quantified by real-time PCR. Mineralization activity was quantified using Alizarin Red S staining, differentiated OC were quantified by counting TRAP-positive multinuclear cells (>2 nuclei). Toll-like receptor (TLR) 4 and TLR2 were blocked by neutralizing antibodies. Results When stimulated with FFA, OB from RA and OA patients secreted higher amounts of the proinflammatory cytokine IL-6 (up to 9-fold) and the chemokines IL-8 (up to 221-fold), GRO-a (from below detection level to detectable levels) and MCP-1 (up to 16-fold). Differences in the degree of response were more dependent on the patient than the disease. RANKL as well as OPG, OB-secreted modulators of OC differentiation, as well as OB differentiation markers (e.g. osterix, osteocalcin) were not influenced by FFA on mRNA or protein level. The effect of FFA on mineralization activity of OB varied between patients, yet overall there was no significant difference between FFA-treated and untreated OB. Expression of the two Wnt signaling molecules, axin-2 and b-catenin, was not changed by PA or LA, suggesting no involvement of the Wnt signaling pathway in the effects observed by FFA in OB. On the other hand, TLR4 blockade significantly reduced PA-induced IL-8 secretion by OB (by 93%), while blocking TLR2 had no effect. In both RA and OA OC, IL-8 secretion was significantly enhanced by PA and LA, with a clear time-dependency within the differentiation process for RA OC but not for OA OC. The number of TRAP positive multinuclear cells decreased for RA OC by approx. 50%, which was in agreement with the reduced TRAP secretion by a factor of 2–3 at d14. mRNA expression of various osteoclast activity markers (CLCN7, CTSK, TCIRG) was not altered. Conclusions Inflammation is promoted by FFA via both OB and OC from patients with RA or OA, thus possibly indirectly contributing to bone loss while no direct effect on OB/OC activity could be observed. In OB, these effects are probably mainly mediated by TLR4, while TLR2 and Wnt pathways do not play a role. Disclosure of Interest None declared

Background Osteoporosis (OP) and osteoarthritis (OA) are two common age-related disorders leading to chronic pain and disability in elderly people. Age-related bone loss and articular cartilage damage are associated with increased bone marrow adiposity due to a possible shift of osteogenic differentiation towards adipogenic differentiation of bone marrow mesenchymal stem cells (MSC). The differentiation of MSC into adipocytes or osteoblasts is an important determinant of bone structural integrity. Adipose tissue is an metabolically active tissue. Therefore adipocyte-derived factors -adipokines- might influence differentiation of bone marrow-derived MSC. Objectives The role of fat-bone interactions in the pathogenesis of OP is poorly understood. Therefore, we analyzed the presence of distinct adipokines (visfatin, resistin and leptin) in the bone marrow cavity and their effects on MSC differentiation. Methods Spongiosa from femoral heads was collected (hip replacement surgery of OA patients or after osteoporotic femoral neck fracture). MSC were cultured in adipogenic and osteogenic media with/without adipokines. For the transfer and differentiation of MSC on cancellous bone, bone fragments were purified and sterilized. mRNA expression of adipokines, bone marker genes, TIMPs and MMPs of stimulated MSC and bone samples were evaluated by realtime PCR. Matrix mineralization was assayed using Alizarin red S staining. Proinflammatory factors were measured by ELISA. Results Visfatin and leptin levels were increased in OP bone vs. non-osteoporotic bone (n=14). In contrast to leptin and resistin, visfatin induced the secretion of proinflammatory factors (IL-6, IL-8, MCP-1) during both, osteogenic and adipogenic differentiation. Visfatin significantly increased the matrix mineralization and downregulated collagen type 1-expression (e.g. d21: -4.6-fold) in osteogenic differentiated cells. Visfatin also reduced the expression of MMP2, MMP13, RunX2, TIMP1 and TIMP2 (e.g. d21: -2.4-fold/-3.18-fold/-5.85-fold/-3.2-fold/-4.3 fold respectively) during osteogenic differentiation, but not leptin and resistin. In contrast to osteogenesis, visfatin significantly induced MMP13 expression (e.g. d21: 104-fold) during adipogenic differentiation under standard cell culture conditions. However, visfatin-induced MMP13-expression was markedly reduced during differentiation on purified autologous cancellous bone. Conclusions Visfatin and leptin levels were elevated in osteoporotic bone tissue. Therefore, the visfatin-mediated increase of matrix mineralization and reduction of collagen type 1 expression might lead to enhanced bone fragility and contribute to the pathogenesis of OP. Visfatin induced release of proinflammatory cytokines and dysregulated expression of MMPs and TIMPs during osteogenic and adipogenic MSC-differentiation might influence bone turnover specifically at the adipose tissue/bone interface. Disclosure of Interest None declared

Background The role of fat–bone interactions in the pathogenesis of osteoporosis is poorly understood. An inverse relationship between bone marrow adipose tissue and bone mineral density during ageing and in osteoporosis is well documented. Adipokines (eg, visfatin, resistin and leptin) are adipocyte-derived factors with immunomodulatory properties and they might influence the differentiation of bone marrow-derived mesenchymal stem cells (MSC) into osteoblasts and adipocytes. The aim was to analyse the presence of adipokines in the bone marrow cavity and their effects on MSC differentiation. Methods Spongiosa from femoral heads containing bone marrow were collected (hip replacement of osteoarthritis patients or after osteoporotic femoral neck fracture). MSC were cultured in adipogenic and osteogenic media with/without adipokines. For the transfer and differentiation of MSC on cancellous bone, bone fragments were purified and sterilised. mRNA expression of adipokines, bone marker genes, TIMPs and MMPs of stimulated MSC and of bone samples were evaluated by real time PCR. Matrix mineralization was investigated using Alizarin red S staining. Proinflammatory factors were measured by ELISA. Results Visfatin and leptin level were increased in osteoporotic bone vs. non-osteoporotic bone (n=14). Visfatin induced the secretion of proinflammatory factors (IL-6, IL-8, MCP-1) during both, osteogenic and adipogenic differentiation but not leptin or resistin. Visfatin markedly increased mineralization during osteogenic differentiation, whereas the Coll.1-expression was significantly downregulated (eg, d21: −4.6-fold). In contrast to resistin and leptin visfatin also reduced the expression of MMP2, MMP13, RunX2, TIMP1 and TIMP2 (eg, d21: −2.4-fold/−3.18 fold/−5.85 fold/−3.2 fold/−4.3 fold respectively) in osteogenic differentiated cells. In contrast to osteogenesis, visfatin significantly increased MMP13 expression (eg, d21: 104-fold) during adipogenic differentiation under standard cell culture conditions, however visfatin induced MMP13-Expression was markedly reduced during differentiation on purified autologous cancellous bone. Conclusion Visfatin and leptin were elevated in osteoporotic bone tissue. Visfatin-mediated increase of matrix mineralization and reduction of Coll.1 expression could enhance bone fragility and contribute to the pathogenesis of osteoporosis. Visfatin might impair bone remodelling at the adipose tissue/bone interface through enhancing secretion of proinflammatory factors and dysregulated MMP- and TIMP-expression during MSC-differentiation.

Background Increased amounts of visceral fat are often associated with lower bone density. Also, in obese patients an increased risk of osteoarthritis can be seen in non-weight bearing joints. Chronically elevated free fatty acid (FFA) levels as occurring in obesity may therefore also play a role in bone loss. We hence analysed if and how FFA influence cells of bone metabolism in rheumatic diseases. Methods Primary osteoblasts (OB) were isolated from cancellous bone of OA and RA patients undergoing knee joint surgery. Osteoclasts (OC) were differentiated from peripheral blood mononuclear cells (PBMC). OB and OC were stimulated with the saturated FFA palmitic acid (PA) and the unsaturated FFA linoleic acid (LA). Protein secretion was quantified by immunoassays, mRNA expression by real-time PCR. Mineralization activity was quantified using Alizarin Red S staining, differentiated OC were quantified by counting TRAP-positive multinuclear cells. Toll-like receptor (TLR) 4 and TLR2 were blocked by neutralising antibodies. Results Stimulation with PA or LA increased OB secretion of the proinflammatory cytokine IL6 (up to 9-fold ↑) and the chemokines IL-8 (up to 221-fold ↑), GRO-α (from below detection level to detectable levels) and MCP1 (up to 16-fold ↑). RANKL and OPG were not influenced by FFA on protein and mRNA level. In osteoblasts, activity (ALP/collagen type I) and differentiation markers (e.g. osteocalcin) as well as production of inorganic matrix were not altered by FFA stimulation. TLR4 but not TLR2 blockade significantly reduced PA-induced IL-8 secretion by OB. Secretion of IL-8 by RA OC was increased by FFA, while MMP-9 was reduced. The mRNA expression of osteoclast activity markers (CLCN7, CTSK, TCIRG) remained unchanged. However, the number of TRAP positive multinuclear cells formed from RA PBMC was decreased (by around 50%). Conclusions The pro-inflammatory effect of certain FFA on osteoblasts and osteoclasts may indirectly contribute to bone loss, while the reduction of mature OC after FFA stimulation suggests an inhibitory effect on bone resorption. In osteoblasts, FFA signalling is at least in part mediated by TLR4, but not by TLR2.

A finely balanced relationship between bone resorption and bone formation is characteristic for a healthy bone metabolism. Osteoblasts are responsible for bone formation and osteoclasts for bone resorption. In general inflammatory and in particular chronic inflammatory processes influence osteoblast and osteoclast function directly or via indirect mechanisms. Bone metabolism can be influenced by the interaction of cytokines, hormones and growth factors with bone cells. A central factor involved in bone metabolism is the receptor activator of nuclear factor-κB (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) system, which is influenced by different inflammatory processes. Usually, (chronic) inflammation results in increased bone loss. The molecular mechanisms and pathophysiological pathways of bone metabolism under the influence of inflammation are summarized in this review.

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.

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.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.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.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.

Adipose tissue secretes highly bioactive factors, the adipokines. Systemic levels of adipokines are often altered in the presence of inflammation. In turn, adipokines affect different tissues and cells systemically as well as locally, contributing to immunomodulatory and bone remodelling mechanisms. The role of adipokines has been evaluated in chronic inflammatory diseases, such as rheumatoid arthritis, as well as in primarily degenerative joint diseases, such as osteoarthritis, particularly with regard to their levels of expression and their effects on joint tissues including synovial membrane, cartilage and bone. Distinct adipokines have been found to modulate matrix remodelling as well as inflammatory responses. In this Review, we summarize current knowledge relating to adipokines in rheumatic diseases, with a particular focus on the effects of adipokines on bone remodelling.

Adipokines such as adiponectin and visfatin/pre-B-cell colony-enhancing factor (PBEF) have been recently shown to contribute to synovial inflammation in rheumatoid arthritis (RA). In this study, we evaluated the pathophysiological implication of visfatin/PBEF in the molecular patterns of RA synovial tissue, focusing on RA synovial fibroblasts (RASFs), key players in RA synovium. Expression of visfatin/PBEF in synovial fluid and tissue of RA patients was detected by immunoassays and immunohistochemistry. RASFs were stimulated with different concentrations of visfatin/PBEF over varying time intervals, and changes in gene expression were evaluated at the RNA and protein levels using Affymetrix array, real-time PCR, and immunoassays. The signaling pathways involved were identified. The influence of visfatin/PBEF on fibroblast motility and migration was analyzed. In RA synovium, visfatin/PBEF was predominantly expressed in the lining layer, lymphoid aggregates, and interstitial vessels. In RASFs, visfatin/PBEF induced high amounts of chemokines such as IL-8 and MCP-1, proinflammatory cytokines such as IL-6, and matrix metalloproteinases such as MMP-3. Phosphorylation of p38 MAPK was observed after visfatin/PBEF stimulation, and inhibition of p38 MAPK showed strong reduction of visfatin-induced effects. Directed as well as general fibroblast motility was increased by visfatin/PBEF-induced factors. The results of this study indicate that visfatin/PBEF is involved in synovial fibroblast activation by triggering fibroblast motility and promoting cytokine synthesis at central sites in RA synovium.

Biologika, haufig in Kombination mit einer konventionellen DMARD-Therapie, stellen einen wesentlichen Fortschritt in der Behandlung rheumatischer Erkrankungen dar. Doch sie sind auch mit Nachteilen verbunden, wie etwa hohen Produktionskosten und parenteraler Administration. Eine erstrebenswerte Alternative sind daher orale niedermolekulare Therapeutika, deren Hauptangriffspunkte intrazellulare Signaltransduktionsmolekule sind. Im Beitrag besprochen werden daher potenzielle intrazellulare Angriffspunkte fur die Behandlung rheumatischer Erkrankungen. Wie therapeutische Signaltransduktionsinhibitoren in der klinischen Praxis letztendlich eingesetzt werden, hangt von mehreren Faktoren ab: von ihrer Gesamteffektivitat, von ihrer Effektivitat bei Patienten, die auf konventionelle DMARD und/oder Biologika nicht oder nur unzureichend ansprechen, von ihrer Effektivitat bei Kombination mit anderen Therapeutika, von ihren Nebenwirkungen und von ihrem Kosten-Nutzen-Verhaltnis.

Introduction Chemerin stimulates migration of leukocytes to sites of inflammation and also increases inflammatory signaling in chondrocytes suggesting a function of chemerin in joint inflammation. Synovial fibroblasts (SF) are critically involved in synovitis and subsequent cartilage destruction. Here, we analyzed whether synovial fibroblasts express chemerin and its receptor CMKLR1. Further, the role of chemerin in synovial fibroblast chemotaxis, proliferation, insulin response and release of inflammatory proteins was studied. Methods Synovial tissue sections were labeled with chemerin antibody and chemerin was measured in synovial fluid by ELISA. Chemerin mRNA and protein as well as CMKLR1 expression were determined in SFs from patients with osteoarthritis (OA) and rheumatoid arthritis (RA). Effects of chemerin on cytokines, chemokines and matrix metalloproteinases (MMP), and on proliferation, migration and insulin signaling were analyzed appropriately. Results SFs expressed CMKLR1 and chemerin mRNA, and chemerin protein was found in cell supernatants of synovial fibroblasts. Immunohistochemistry detected chemerin in synovial tissue predominantly localized within the lining layer. Chemerin was present in synovial fluids of RA, OA and psoriatic arthritis patients in similar concentrations. Chemerin neither increased IL-6 levels nor MMP-2 or − 9 activity in SFs. Also, it did not act as a chemoattractant for these cells. With respect to intracellular signaling, neither basal nor insulin-mediated phosphorylation of Akt was affected. However, chemerin significantly increased TLR4 mRNA and synthesis of CCL2 in SFs while CCL4 and − 5 were not altered. Cell proliferation of SFs, however, was modestly reduced by chemerin. Conclusions These data show that human SFs express both chemerin and its receptor. As chemerin enhanced expression of TLR4 and induced release of CCL2 in SFs, a role of this protein in innate immune system-associated joint inflammation is proposed.

Adipose tissue is ubiquitously present in the human organism. It is a structural component of many organs including the skin, the intestinal tract, and the joints. Besides its central function in energy metabolism, adipose tissue usually serves as a bolster in gaps or intersections between tissues. The dominant cell type, adipocytes, secretes highly bioactive substances, the socalled adipokines or adipocytokines (Table 1). Adipokines include a growing number of pluripotent factors such as adiponectin, resistin, leptin, and visfatin/pre–B cell colony-enhancing factor (PBEF) (1,2). Table 2 provides an overview of several characteristics of these adipokines, and their respective functional aspects are discussed below. There is also increasing evidence that adipocytes actively secrete additional proinflammatory factors operative in the pathophysiology of inflamed joints, such as tumor necrosis factor (TNF ), interleukin-6 (IL-6), factors of the complement system, growth factors, and adhesion molecules (2–4). Moreover, adipokines are able to actively modulate inflammation and the innate immune system (1,5). In this review, the current knowledge about the influence of central adipokines in rheumatic diseases, highlighting several aspects of the role of adipokines in chronic inflammation, is summarized.

Liebe Leserin, lieber Leser,beim Thema Stoffwechsel und Rheuma denken vermutlich die meisten von Ihnen zuallererst an Adipositas und Arthrose. Doch die Verbindung zwischen Metabolismus/Stoffwechsel und Rheuma ist deutlich breiter gefächert. Stoffwechselerkrankungen, altersbedingte metabolische Veränderungen bzw. allgemein verschiedene Metabolite können Risikofaktor, Ursache oder kontributiver Faktor von rheumatischen Erkrankungen sein.

OBJECTIVE: Rheumatoid arthritis (RA) is associated with increased production of adipokines, which are cytokine-like mediators that are produced mainly in adipose tissue but also in synovial cells. Since RA synovial fibroblasts (RASFs), lymphocytes, endothelial cells, and chondrocytes are key players in the pathophysiology of RA, this study was undertaken to analyze the effects of the key adipokine adiponectin on proinflammatory and prodestructive synovial effector cells. METHODS: Lymphocytes were activated in part prior to stimulation. All cells were stimulated with adiponectin, and changes in gene and protein expression were determined by Affymetrix and protein arrays. Messenger RNA and protein levels were confirmed using semiquantitative reverse transcription-polymerase chain reaction (PCR), real-time PCR, and immunoassays. Intracellular signal transduction was evaluated using chemical signaling inhibitors. RESULTS: Adiponectin stimulation of human RASFs predominantly induced the secretion of chemokines, as well as proinflammatory cytokines, prostaglandin synthases, growth factors, and factors of bone metabolism and matrix remodeling. Lymphocytes, endothelial cells, and chondrocytes responded to adiponectin stimulation with enhanced synthesis of cytokines and various chemokines. Additionally, chondrocytes released increased amounts of matrix metalloproteinases. In RASFs, adiponectin-mediated effects were p38 MAPK and protein kinase C dependent. CONCLUSION: Our previous findings indicated that adiponectin was present in inflamed synovium, at sites of cartilage invasion, in lymphocyte infiltrates, and in perivascular areas. The findings of the present study indicate that adiponectin induces gene expression and protein synthesis in human RASFs, lymphocytes, endothelial cells, and chondrocytes, supporting the concept of adiponectin being involved in the pathophysiologic modulation of RA effector cells. Adiponectin promotes inflammation through cytokine synthesis, attraction of inflammatory cells to the synovium, and recruitment of prodestructive cells via chemokines, thus promoting matrix destruction at sites of cartilage invasion.

Bone remodelling is characterized by a balance between bone resorption and bone formation. The osteoblasts are responsible for bone synthesis and the osteoclasts for bone resorption. A finely adjusted interaction between molecular mechanisms results, via cytokines, hormones and growth factors, in homeostasis of bone metabolism. Here, the RANK/RANKL/OPG-system is actively involved in the differentiation and function of osteoclasts and is known to play a central role in the majority of pathophysiological mechanisms. Also the Wnt and BMP signalling pathways play a major role in osteoblast differentiation and bone remodeling. An increased osteoclast activity contributes to inflammatory and destructive osteocatabolic manifestations and/or osteoporosis whereas an increased osteoblast activity can result in osteopetrosis. This overview describes the known relevant pathophysiological metabolic pathways in this remodelling process, especially the effect of inflammation on bone metabolism, and outlines the links from bench to bedside.

ObjectivesDue to their role in inflammatory metabolic diseases, we hypothesised that free fatty acids (FFA) are also involved in inflammatory joint diseases. To test this hypothesis, we analysed the effect of FFA on synovial fibroblasts (SF), human chondrocytes and endothelial cells. We also investigated whether the toll-like receptor 4 (TLR4), which can contribute to driving arthritis, is involved in FFA signalling.MethodsRheumatoid arthritis SF, osteoarthritis SF, psoriatic arthritis SF, human chondrocytes and endothelial cells were stimulated in vitro with different FFA. Immunoassays were used to quantify FFA-induced protein secretion. TLR4 signalling was inhibited extracellularly and intracellularly. Fatty acid translocase (CD36), responsible for transporting long-chain FFA into the cell, was also inhibited.ResultsIn rheumatoid arthritis synovial fibroblasts (RASF), FFA dose-dependently enhanced the secretion of the proinflammatory cytokine IL-6, the chemokines IL-8 and MCP-1, as well as the matrix-degrading enzymes pro-MMP1 and MMP3. The intensity of the response was mainly dependent on the patient rather than on the type of disease. Both saturated and unsaturated FFA showed similar effects on RASF, while responses to the different FFA varied for human chondrocytes and endothelial cells. Extracellular and intracellular TLR4 inhibition as well as fatty acid transport inhibition blocked the palmitic acid-induced IL-6 secretion of RASF.ConclusionsThe data show that FFA are not only metabolic substrates but may also directly contribute to articular inflammation and degradation in inflammatory joint diseases. Moreover, the data suggest that, in RASF, FFA exert their effects via TLR4 and require extracellular and intracellular access to the TLR4 receptor complex.