CCL19-Positive Lymph Node Stromal Cells Govern the Onset of Inflammatory Arthritis via Tropomyosin Receptor Kinase.

OBJECTIVE: The study objective was to assess the role of CCL19+ lymph node stromal cells of the joint-draining popliteal lymph node (pLN) for the development of arthritis. METHODS: CCL19+ lymph node stromal cells were spatiotemporally depleted for five days in the pLN before the onset of collagen-induced arthritis (CIA) using Ccl19-Cre × iDTR mice. In addition, therapeutic treatment with recombinant CCL19-immunoglobulin G (IgG), locally injected in the footpad, was used to confirm the results. RNA sequencing of lymph node stromal cells combined with T cell coculture assays using tropomyosin receptor kinase (Trk) family inhibitors together with in vivo local pLN small interfering RNA (siRNA) treatments were used to elucidate the pathway by which CCL19+ lymph node stromal cells initiate the onset of arthritis. RESULTS: Spatiotemporal depletion of CCL19+ lymph node stromal cells prevented disease onset in CIA mice. These inhibitory effects could be mimicked by local CCL19-IgG treatment. The messenger RNA sequencing analyses showed that CCL19+ lymph node stromal cells down-regulated the expression of the tropomyosin receptor kinase A (TrkA) just before disease onset. Blocking TrkA in lymph node stromal cells led to increased T cell proliferation in in vitro coculture assays. Similar effects were observed with the pan-Trk inhibitor larotrectinib in cocultures of lymph node stromal cells of patients with rheumatoid arthritis and T cells. Finally, local pLN treatment with TrkA inhibitor and TrkA siRNA led to exacerbated arthritis scores. CONCLUSION: CCL19+ lymph node stromal cells are crucially involved in the development of inflammatory arthritis. Therefore, targeting of CCL19+ lymph node stromal cells via TRK could provide a tool to prevent arthritis.

Increased Frequency of CD4+ Follicular Helper T and CD8+ Follicular T Cells in Human Lymph Node Biopsies during the Earliest Stages of Rheumatoid Arthritis.

Follicular T helper cells (Tfh cells) provide key B-cell help and are essential in germinal center formation and (auto) antibody generation. To gain more insight into their role during the earliest phase of rheumatoid arthritis (RA), we analyzed their frequencies, phenotypes, and cytokine profiles in peripheral blood and lymph node biopsies of healthy controls (HCs), autoantibody-positive individuals at risk for developing RA (RA-risk individuals), and early RA patients. Subsequently, we confirmed their presence in lymph nodes and synovial tissue of RA patients using immunofluorescence microscopy. In the blood, the frequency of Tfh cells did not differ between study groups. In lymphoid and synovial tissues, Tfh cells were localized in B-cell areas, and their frequency correlated with the frequency of CD19+ B cells. Compared to lymphoid tissues of healthy controls, those of RA patients and RA-risk individuals showed more CD19+ B cells, CD4+CXCR5+ follicular helper T cells, and CD8+CXCR5+ follicular T cells. These Tfh cells produced less IL-21 upon ex vivo stimulation. These findings suggest that Tfh cells may present a novel rationale for therapeutic targeting during the preclinical stage of RA to prevent further disease progression.

Impact of Adalimumab Treatment on Interleukin-17 and Interleukin-17 Receptor Expression in Skin and Synovium of Psoriatic Arthritis Patients with Mild Psoriasis.

Interleukin (IL)-17 and tumor necrosis factor-alpha (TNF)-α are key players in psoriatic arthritis (PsA) pathogenesis. While both cytokines can be therapeutically targeted with beneficial clinical outcome, it is unclear whether inhibiting one cytokine will affect the other at sites of inflammation. If both act independently, this might provide a rationale for dual or combined inhibition of both cytokines. Here, we evaluated the effect of TNF blockade in PsA patients on IL-17 levels in both skin and synovial tissue biopsies. PsA patients with mild psoriatic skin lesions were randomized to receive either adalimumab or placebo for four weeks. Synovial and skin biopsies were obtained at weeks zero and four. Skin from healthy donors (HDs) was used for comparison. Expression of IL-17A, IL-17F, IL-17RA and IL-17RC was assessed by immunohistochemistry and analyzed with digital image analysis. We found relatively low levels of IL-17 and its receptors in the skin of PsA patients compared to HD, and only IL-17F in the dermis of lesional psoriatic skin was significantly higher compared to HD skin (p = 0.0002). Histologically IL-17A, IL-17F, IL-17RA and IL-17RC in skin and synovial tissue were not downregulated by adalimumab treatment. Thus, in this cohort of PsA patients with mild psoriasis, TNF blockade did not affect the protein levels of IL-17 cytokines and its receptors in skin and synovium, despite reduced cellular inflammation and improved clinical outcome for joint involvement.

Ultrasound-guided lymph node biopsy sampling to study the immunopathogenesis of rheumatoid arthritis: a well-tolerated valuable research tool.

BACKGROUND: Analyses of lymphoid organs are required to further elucidate the pathogenesis of inflammatory diseases like rheumatoid arthritis (RA). Yet, invasive tissue collection methods are scarcely applied, because they are often considered burdensome, although patients do not always consider invasive methods as a high burden. We aimed to investigate the perspectives of study participants undergoing ultrasound-guided inguinal lymph node (LN) needle biopsy sampling and determine the molecular and cellular quantity and quality of LN biopsies. METHODS: Together with patient research partners, questionnaires were developed to evaluate the motives, expectations, and experiences of participants undergoing a LN biopsy. Healthy controls and RA(-risk) patients were asked to complete these questionnaires before and after the procedure. RNA and lymphocyte yields from obtained LN biopsies were also calculated. RESULTS: We included 50 individuals, of which 43 (86%) reported their pre- and post-procedure experiences. The median reported pain on a 5-point Likert scale (1 not to 5 very painful) was 1. Interestingly, almost all (n = 32; 74%) study participants would undergo a second procedure and more than half (n = 23; 54%) would encourage others to take part in the LN biopsy study. Motives for current and future participation were mostly altruistic. Inguinal hematoma occurred frequently, but no other significant or unexpected complications ensued. The LN biopsies yielded sufficient and high-quality RNA and lymphocyte numbers. CONCLUSIONS: Ultrasound-guided inguinal LN biopsy sampling is well-tolerated, safe, and provides sufficient material for further molecular and cellular analyses. Our participants' positive experiences endorse the application of this research tool to further elucidate the pathogenesis of RA and other inflammatory diseases.

Lower Metabolic Potential and Impaired Metabolic Flexibility in Human Lymph Node Stromal Cells from Patients with Rheumatoid Arthritis.

Cellular metabolism is important for determining cell function and shaping immune responses. Studies have shown a crucial role for stromal cells in steering proper immune responses in the lymph node microenvironment. These lymph node stromal cells (LNSCs) tightly regulate immune tolerance. We hypothesize that malfunctioning LNSCs create a microenvironment in which normal immune responses are not properly controlled, possibly leading to the development of autoimmune diseases such as rheumatoid arthritis (RA). Therefore, we set out to determine their metabolic profile during health and systemic autoimmunity. We included autoantibody positive individuals at risk of developing RA (RA-risk individuals), RA patients and healthy volunteers. All study subjects underwent lymph node biopsy sampling. Mitochondrial function in cultured LNSCs was assessed by quantitative PCR, flow cytometry, Seahorse and oleate oxidation assays. Overall, mitochondrial respiration was lower in RA(-risk) LNSCs compared with healthy LNSCs, while metabolic potential was only lower in RA LNSCs. To maintain basal mitochondrial respiration, all LNSCs were mostly dependent on fatty acid oxidation. However, RA(-risk) LNSCs were also dependent on glutamine oxidation. Finally, we showed that RA LNSCs have impaired metabolic flexibility. Our results show that the metabolic landscape of LNSCs is not only altered during established disease, but partly already in individuals at risk of developing RA. Future studies are needed to investigate the impact of restoring metabolic capacity in LNSC-mediated immunomodulation and disease progression.

Translational Research Studies Unraveling the Origins of Psoriatic Arthritis: Moving Beyond Skin and Joints.

Patients with psoriatic arthritis (PsA) are suffering from a decreased quality of life despite currently available treatments. In the latest years, novel therapies targeting the IL-17/IL-23 and TNF pathways improved clinical outcome. Despite this, remission of disease is not achieved in a considerable group of patients, continuous treatment is very often required to reach clinical remission, and prevention of PsA in patients with psoriasis (PsO) is currently impossible. A better understanding of PsA pathogenesis is required to develop novel treatment strategies that target inflammation and destruction more effectively and at an early stage of the disease, or even before clinically manifest disease. The skin is considered as one of the sites of onset of immune activation, triggering the inflammatory cascade in PsA. PsO develops into PsA in 30% of the PsO patients. Influenced by environmental and genetic factors, the inflammatory process in the skin, entheses, and/or gut may evolve into synovial tissue inflammation, characterized by influx of immune cells. The exact role of the innate and adaptive immune cells in disease pathogenesis is not completely known. The involvement of activated IL-17A+ T cells could implicate early immunomodulatory events generated in lymphoid organs thereby shaping the pathogenic inflammatory response leading to disease. In this perspective article, we provide the reader with an overview of the current literature regarding the immunological changes observed during the earliest stages of PsA. Moreover, we will postulate future areas of translational research aimed at increasing our knowledge on the molecular mechanisms driving disease development, which will aid the identification of novel potential therapeutic targets to limit the progression of PsA.

Tertiary Lymphoid Structures: Diversity in Their Development, Composition, and Role.

Lymph node stromal cells coordinate the adaptive immune response in secondary lymphoid organs, providing both a structural matrix and soluble factors that regulate survival and migration of immune cells, ultimately promoting Ag encounter. In several inflamed tissues, resident fibroblasts can acquire lymphoid-stroma properties and drive the formation of ectopic aggregates of immune cells, named tertiary lymphoid structures (TLSs). Mature TLSs are functional sites for the development of adaptive responses and, consequently, when present, can have an impact in both autoimmunity and cancer conditions. In this review, we go over recent findings concerning both lymph node stromal cells and TLSs function and formation and further describe what is currently known about their role in disease, particularly their potential in tolerance.

Molecular Characterization of Human Lymph Node Stromal Cells During the Earliest Phases of Rheumatoid Arthritis.

Rheumatoid arthritis (RA) is a progressive, destructive autoimmune arthritis. Break of tolerance and formation of autoantibodies occur years before arthritis. Adaptive immunity is initiated in lymphoid tissue where lymph node stromal cells (LNSCs) play a crucial role in shaping the immune response and maintaining peripheral tolerance. Here we performed the first epigenomic characterization of LNSCs during health and early RA, by analyzing their transcriptome and DNA methylome in LNSCs isolated from lymph node needle biopsies obtained from healthy controls (HC), autoantibody positive RA-risk individuals and patients with established RA. Of interest, LNSCs from RA-risk individuals and RA patients revealed a common significantly differential expressed gene signature compared with HC LNSCs. Pathway analysis of this common signature showed, among others, significant enrichment of pathways affecting the extracellular matrix (ECM), cholesterol biosynthesis and immune system. In a gel contraction assay LNSCs from RA-risk individuals and RA patients showed impaired collagen contraction compared to healthy LNSCs. In RA LNSCs a significant enrichment was observed for genes involved in cytokine signaling, hemostasis and packaging of telomere ends. In contrast, in RA-risk LNSCs pathways in cancer (cell cycle related genes) were differentially expressed compared with HC, which could be validated in vitro using a proliferation assay, which indicated a slower proliferation rate. DNA methylation analyses revealed common and specific differentially methylated CpG sites (DMS) in LNSC from RA patients and RA-risk individuals compared with HC. Intriguingly, shared DMS were all associated with antigen processing and presentation. This data point toward alterations in cytoskeleton and antigen-processing and presentation in LNSC from RA-risk individuals and RA patients. Further studies are required to investigate the consequence of this LNSC abnormality on LNSC-mediated immunomodulation.

Effect of rituximab treatment on T and B cell subsets in lymph node biopsies of patients with rheumatoid arthritis.

OBJECTIVES: The exact underlying mechanism of rituximab treatment in patients with RA is poorly defined and knowledge about the effect of B cell depletion on immune cells in secondary lymphoid organs is lacking. We analysed lymphoid tissue responses to rituximab in RA patients. METHODS: Fourteen RA patients received 2 × 1000 mg rituximab intravenously, and lymph node (LN) biopsies were obtained before and 4 weeks after the first infusion. Tissues were examined by flow cytometry, immunohistochemistry and quantitative PCR. LN biopsies from five healthy individuals (HC) served as controls. RESULTS: LN biopsies of RA patients showed increased frequencies of CD21+CD23+IgDhighIgMvariable follicular B cells and CD3+CD25+CD69+ early activated, tissue resident T cells when compared with HCs. After treatment, there was incomplete depletion of LN B cells. There was a significant decrease in CD27-IgD+ naïve B cells, and CD27+IgD+ unswitched memory B cells including the CD27+IgD+IgM+ subset and follicular B cells. Strikingly, CD27+IgD- switched memory B cells persisted in LN biopsies after rituximab treatment. In the T cell compartment, a significant decrease was observed in the frequency of early activated, tissue resident T cells after rituximab treatment, but late activated T cells persisted. B cell proliferation inducing cytokine IL-21 was higher expressed in LN biopsies of RA patients compared with HC and expression was not affected by rituximab treatment. CONCLUSION: Rituximab does not cure RA, possibly due to persistence of switched memory B cells in lymphoid tissues suggesting that factors promoting B cell survival and differentiation need to be additionally targeted.

Impaired lymph node stromal cell function during the earliest phases of rheumatoid arthritis.

BACKGROUND: Systemic autoimmunity can be present years before clinical onset of rheumatoid arthritis (RA). Adaptive immunity is initiated in lymphoid tissue where lymph node stromal cells (LNSCs) regulate immune responses through their intimate connection with leucocytes. We postulate that malfunctioning of LNSCs creates a microenvironment in which normal immune responses are not properly controlled, possibly leading to autoimmune disease. In this study we established an experimental model for studying the functional capacities of human LNSCs during RA development. METHODS: Twenty-four patients with RA, 23 individuals positive for autoantibodies but without clinical disease (RA risk group) and 14 seronegative healthy control subjects underwent ultrasound-guided inguinal lymph node (LN) biopsy. Human LNSCs were isolated and expanded in vitro for functional analyses. In analogous co-cultures consisting of LNSCs and peripheral blood mononuclear cells, αCD3/αCD28-induced T-cell proliferation was measured using carboxyfluorescein diacetate succinimidyl ester dilution. RESULTS: Fibroblast-like cells expanded from the LN biopsy comprised of fibroblastic reticular cells (gp38+CD31-) and double-negative (gp38-CD31-) cells. Cultured LNSCs stably expressed characteristic adhesion molecules and cytokines. Basal expression of C-X-C motif chemokine ligand 12 (CXCL12) was lower in LNSCs from RA risk individuals than in those from healthy control subjects. Key LN chemokines C-C motif chemokine ligand (CCL19), CCL21 and CXCL13 were induced in LNSCs upon stimulation with tumour necrosis factor-α and lymphotoxin α1ß2, but to a lesser extent in LNSCs from patients with RA. The effect of human LNSCs on T-cell proliferation was ratio-dependent and altered in RA LNSCs. CONCLUSIONS: Overall, we developed an experimental model to facilitate research on the role of LNSCs during the earliest phases of RA. Using this innovative model, we show, for the first time to our knowledge, that the LN stromal environment is changed during the earliest phases of RA, probably contributing to deregulated immune responses early in disease pathogenesis.

Brief Report: Altered Innate Lymphoid Cell Subsets in Human Lymph Node Biopsy Specimens Obtained During the At-Risk and Earliest Phases of Rheumatoid Arthritis.

OBJECTIVE: Innate lymphoid cells (ILCs) are emerging mediators of immunity, and accumulation of inflammatory ILC populations can occur in inflammatory-mediated conditions. Since early lymph node (LN) activation has been shown in rheumatoid arthritis (RA), we aimed to investigate the frequency and distribution of ILCs in LN biopsy specimens obtained during the earliest phases of RA. METHODS: Twelve patients with early RA, 12 individuals with IgM rheumatoid factor and/or anti-citrullinated protein antibodies without arthritis (RA risk group), and 7 healthy controls underwent ultrasound-guided inguinal LN biopsy. ILC subsets and the expression of vascular cell adhesion molecule (VCAM) and intercellular adhesion molecule (ICAM) by LN endothelial cells and fibroblasts were analyzed by flow cytometry. RESULTS: Although no differences in the frequencies of total ILCs (Lin-CD45+/low CD127+) were found, the distribution of the ILC subpopulations differed among groups. RA patients showed lower numbers of lymphoid tissue-inducer (LTi) cells (c-Kit+NKp44- ILCs) and increased ILC1 (c-Kit-NKp44- ILCs) and ILC3 (c-Kit+NKp44+ ILCs) numbers compared with controls (P < 0.001, P < 0.050, and P < 0.050, respectively). Individuals at risk of RA exhibited an increased frequency of ILC1 compared with controls (P < 0.01). LTi cells paralleled the expression of adhesion molecules on endothelial cells and fibroblasts. CONCLUSION: Our findings indicate that during the at-risk and earliest phases of RA, the ILC distribution in LN changes from a homeostatic profile toward a more inflammatory profile, thereby providing evidence of a role for ILCs in RA pathogenesis.

Lymph node biopsy analysis reveals an altered immunoregulatory balance already during the at-risk phase of autoantibody positive rheumatoid arthritis.

The balance between proinflammatory and regulatory CD4+ T cells is tightly controlled in lymphoid organs. In autoimmune diseases this balance is altered in the periphery and target tissue of patients. However, not much is known about the balance initiated in lymphoid organs during the development of disease. Since systemic autoimmunity is present years before the clinical manifestations of rheumatoid arthritis (RA), it is possible to study the immunoregulatory balance during the earliest (preclinical) phases of disease. Here, we report for the first time the frequency and phenotype of proinflammatory and regulatory CD4+ T cells in lymph node biopsies obtained from autoantibody positive individuals at risk for developing RA, patients with established disease and healthy controls. The frequency of proinflammatory LN Th1 cells was increased in RA patients compared with HCs, while the frequency of regulatory T cells was lower in LN biopsies of RA-risk individuals. Upon in vitro stimulation LN CD4+ T cells produced lower levels of proinflammatory cytokines, IFN-γ and IL-17A, in both RA-risk individuals and early RA patients. This study shows that already during the earliest phases of systemic autoimmunity the immunoregulatory balance between proinflammatory and regulatory CD4+ T cells is altered in LN tissue.

Inflammatory cytokines epigenetically regulate rheumatoid arthritis fibroblast-like synoviocyte activation by suppressing HDAC5 expression.

OBJECTIVES: Epigenetic modifications play an important role in the regulation of gene transcription and cellular function. Here, we examined if pro-inflammatory factors present in the inflamed joint of patients with rheumatoid arthritis (RA) could regulate histone deacetylase (HDAC) expression and function in fibroblast-like synoviocytes (FLS). METHODS: Protein acetylation in synovial tissue was assessed by immunohistochemistry. The mRNA levels of HDAC family members and inflammatory mediators in the synovial tissue and the changes in HDAC expression in RA FLS were measured by quantitative (q) PCR. FLS were either transfected with HDAC5 siRNA or transduced with adenoviral vector encoding wild-type HDAC5 and the effects of HDAC5 manipulation were examined by qPCR arrays, ELISA and ELISA-based assays. RESULTS: Synovial class I HDAC expression was associated with local expression of tumour necrosis factor (TNF) and matrix metalloproteinase-1, while class IIa HDAC5 expression was inversely associated with parameters of disease activity (erythrocyte sedimentation rate, C-reactive protein, Disease Activity Score in 28 Joints). Interleukin (IL)-1ß or TNF stimulation selectively suppressed HDAC5 expression in RA FLS, which was sufficient and required for optimal IFNB, CXCL9, CXCL10 and CXCL11 induction by IL-1ß, associated with increased nuclear accumulation of the transcription factor, interferon regulatory factor 1(IRF1). CONCLUSIONS: Inflammatory cytokines suppress RA FLS HDAC5 expression, promoting nuclear localisation of IRF1 and transcription of a subset of type I interferon response genes. Our results identify HDAC5 as a novel inflammatory mediator in RA, and suggest that strategies rescuing HDAC5 expression in vivo, or the development of HDAC inhibitors not affecting HDAC5 activity, may have therapeutic applications in RA treatment.

Expression of Prostaglandin E2 Enzymes in the Synovium of Arthralgia Patients at Risk of Developing Rheumatoid Arthritis and in Early Arthritis Patients.

OBJECTIVE: Arthralgia may precede the development of synovial inflammation in autoantibody-positive individuals at risk of developing rheumatoid arthritis (RA). A major pathway involved in pain is the prostaglandin (PG) E2 pathway. We investigated this pathway in the synovium of individuals with RA-specific autoantibodies and in early arthritis patients. METHODS: Nineteen autoantibody-positive individuals (IgM-rheumatoid factor and/or anti-cyclic citrullinated peptide antibodies) with arthralgia (n=15) and/or a positive family history of RA (n=8), who had been prospectively followed for at least 2 years, were included. In addition, we included early arthritis patients (disease-modifying antirheumatic drug naïve) who after 2 years follow up fulfilled classification criteria for RA (n=63), spondyloarthritis (SpA; n=14), or had unclassified arthritis (UA; n=27). In all subjects we assessed pain and performed synovial biopsy sampling by mini-arthroscopy at baseline. Tissue sections were examined by immunohistochemistry to detect and quantify PGE2 pathway enzymes expression levels (mPGES-1; COX-1 and -2; 15-PGDH). RESULTS: In both study groups synovial expression of PGE2 enzymes was not clearly related to pain sensation. Expression levels at baseline were not associated with the development of arthritis after follow up (6 out of 19 autoantibody-positive individuals). However, in early SpA patients the expression levels of mPGES-1 and COX-1 were significantly increased compared to RA and UA patients. CONCLUSION: Pain in autoantibody-positive individuals without synovial inflammation who are at risk of developing RA and in early arthritis patients may be regulated by pathways other than the PGE2 pathway or originate at sites other than the synovium. In contrast, in SpA, the PGE2 pathway may be inherently linked to the pathophysiology/etiology of the disease.

JNK-dependent downregulation of FoxO1 is required to promote the survival of fibroblast-like synoviocytes in rheumatoid arthritis.

BACKGROUND: Forkhead box O (FoxO) transcription factors integrate environmental signals to modulate cell proliferation and survival, and alterations in FoxO function have been reported in rheumatoid arthritis (RA). OBJECTIVES: To examine the relationship between inflammation and FoxO expression in RA, and to analyse the mechanisms and biological consequences of FoxO regulation in RA fibroblast-like synoviocytes (FLS). METHODS: RNA was isolated from RA patient and healthy donor (HD) peripheral blood and RA synovial tissue. Expression of FoxO1, FoxO3a and FoxO4 was measured by quantitative PCR. FoxO1 DNA binding, expression and mRNA stability in RA FLS were measured by ELISA-based assays, immunoblotting and quantitative PCR. FLS were transduced with adenovirus encoding constitutively active FoxO1 (FoxO1ADA) or transfected with small interfering RNA targeting FoxO1 to examine the effects on cell viability and gene expression. RESULTS: FoxO1 mRNA levels were reduced in RA patient peripheral blood compared with HD blood, and RA synovial tissue FoxO1 expression correlated negatively with disease activity. RA FLS stimulation with interleukin 1ß or tumour necrosis factor caused rapid downregulation of FoxO1. This effect was independent of protein kinase B (PKB), but dependent on c-Jun N-terminal kinase (JNK)-mediated acceleration of FoxO1 mRNA degradation. FoxO1ADA overexpression in RA FLS induced apoptosis associated with altered expression of genes regulating cell cycle and survival, including BIM, p27(Kip1) and Bcl-XL. CONCLUSIONS: Our findings identify JNK-dependent modulation of mRNA stability as an important PKB-independent mechanism underlying FoxO1 regulation by cytokines, and suggest that reduced FoxO1 expression is required to promote FLS survival in RA.

Heterogeneous expression pattern of interleukin 17A (IL-17A), IL-17F and their receptors in synovium of rheumatoid arthritis, psoriatic arthritis and osteoarthritis: possible explanation for nonresponse to anti-IL-17 therapy?

INTRODUCTION: Accumulating evidence suggests an important role for interleukin 17 (IL-17) in the pathogenesis of several inflammatory diseases, including rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Accordingly, clinical trials aimed at blocking IL-17 have been initiated, but clinical results between patients and across different diseases have been highly variable. The objective was to determine the variability in expression of IL-17A, IL-17F and their receptors IL-17RA and IL-17RC in the synovia of patients with arthritis. METHODS: Synovial biopsies were obtained from patients with RA (n = 11), PsA (n = 15) and inflammatory osteoarthritis (OA, n = 14). For comparison, synovia from noninflamed knee joints (n = 7) obtained from controls were included. Frozen sections were stained for IL-17A, IL-17F, IL-17RA and IL-17RC and evaluated by digital image analysis. We used confocal microscopy to determine which cells in the synovium express IL-17A and IL-17F, double-staining with CD4, CD8, CD15, CD68, CD163, CD31, von Willebrand factor, peripheral lymph node address in, lymphatic vessel endothelial hyaluronan receptor 1, mast cell tryptase and retinoic acid receptor-related orphan receptor γt (RORγt). RESULTS: IL-17A, IL-17F, IL-17RA and IL-17RC were abundantly expressed in synovial tissues of all patient groups. Whereas IL-17RA was present mostly in the synovial sublining, IL-17RC was abundantly expressed in the intimal lining layer. Digital image analysis showed a significant (P < 0.05) increase of only IL-17A in arthritis patients compared to noninflamed control tissues. The expression of IL-17A, IL-17F and their receptors was similar in the different patient groups, but highly variable between individual patients. CD4+ and CD8+ cells coexpressed IL-17A, and few cells coexpressed IL-17F. IL-17A and IL-17F were not expressed by CD15+ neutrophils. Mast cells were only occasionally positive for IL-17A or IL-17F. Interestingly, IL-17A and IL-17F staining was also observed in macrophages, as well as in blood vessels and lymphatics. This staining probably reflects receptor-bound cytokine staining. Many infiltrated cells were positive for the transcription factor RORγt. Colocalisation between RORγt and IL-17A and IL-17F indicates local IL-17 production. CONCLUSIONS: Increased expression of IL-17A is not restricted to synovial tissues of RA and PsA patients; it is also observed in inflammatory OA. The heterogeneous expression levels may explain nonresponse to anti-IL-17 therapy in subsets of patients.

Smoking and overweight determine the likelihood of developing rheumatoid arthritis.

OBJECTIVES: Rheumatoid arthritis (RA) is a prototypic chronic inflammatory disease with a debilitating course if untreated. A genetic predisposition for RA is known, and its occurrence is associated with the presence of autoantibodies in the serum and with environmental factors. It is unknown if smoking and overweight are contributory factors for developing RA in individuals with RA-specific autoantibodies in the serum. METHODS: Fifty-five individuals at risk for developing RA, based on the presence of RA-specific autoantibodies in the serum, who never had any evidence of arthritis upon physical examination, were followed over time. Smoking was assessed as being never or ever smoker and body mass index as <25 (normal) or ≥25 kg/m² (overweight). Clinical endpoint was the occurrence of arthritis. Proportional hazard regression analysis was performed to investigate the potential of (combinations of) variables in predicting the onset of arthritis over time. RESULTS: After a median follow up time of 13 (IQR 6-27) months, 15 individuals (27%) developed arthritis. Smoking was associated with the development of arthritis (HR (95% CI): 9.6 (1.3 to 73.0); p=0.029). Overweight was, independently of smoking, associated with arthritis (HR (95% CI): 5.6 (1.3 to 25.0); p=0.023). The overall arthritis risk of 28% after a median of 27 months follow up increased to 60% in individuals with a smoking history combined with overweight. CONCLUSIONS: This is the first prospective study showing that smoking and overweight increase the risk of development of arthritis in a cohort of autoantibody-positive individuals at risk for developing RA. These results show the importance of life style factors in development of RA and should be critically evaluated in future clinical research aimed at disease prevention.

[Tailored therapy for rheumatic disease within reach]. / Kan therapie op maat realiteit worden?

Personalised medicine has the potential to increase therapeutic effectiveness, reduce side effects and lower cost. This approach has recently taken off in oncology where different malignancies may be treated with specific drugs based on genetic biomarkers or other tumour characteristics. This type of tailored therapy could also be developed for immune-mediated inflammatory disease, for which rheumatoid arthritis (RA) may serve as a prototype. While novel treatments are able to halt or even prevent disease progression, not all RA patients respond, and stratification of patient groups is needed. The identification of biomarkers predictive of the clinical response to specific treatments in subsets of patients may soon become reality in a variety of diseases.

Evaluating antirheumatic treatments using synovial biopsy: a recommendation for standardisation to be used in clinical trials.

Inflammation of synovium is one of the hallmarks of rheumatoid arthritis (RA). Analysis of synovial tissue has increased our understanding of RA pathogenesis, aided in identifying potential therapeutic targets and has been used in the response and mechanistic evaluation of antirheumatic treatments. In addition, studies are ongoing, aimed at the identification of diagnostic and prognostic biomarkers in the synovium. This paper outlines the currently used procedures for sampling and processing of synovial tissue, and presents a standardised recommendation to support multicentre translational research.

Type I IFN and TNFα cross-regulation in immune-mediated inflammatory disease: basic concepts and clinical relevance.

A cross-regulation between type I IFN and TNFα has been proposed recently, where both cytokines are hypothesized to counteract each other. According to this model, different autoimmune diseases can be viewed as disequilibrium between both cytokines. As this model may have important clinical implications, the present review summarizes and discusses the currently available clinical evidence arguing for or against the proposed cross-regulation between TNFα and type I IFN. In addition, we review how this cross-regulation works at the cellular and molecular levels. Finally, we discuss the clinical relevance of this proposed cross-regulation for biological therapies such as type I IFN or anti-TNFα treatment.