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Background: IL6-related T cell activation and TNFaα-dependent cell proliferation are major targets of therapy in the RA synovium. We investigated whether expression of these pathways in RA synovial biopsies is associated with disease activity and response to therapy. Method: Correlation and gene set enrichment studies were performed using gene expression profiles from RA synovial biopsies. Immunostaining experiments of GADD45B and PDE4D were performed on independent additional sets of early untreated RA samples, obtained in two different centers by needle-arthroscopy or US-guided biopsies. Results: In 65 RA synovial biopsies, transcripts correlating with disease activity were strongly enriched in TNFaα-induced genes. Out of the individual variables used in disease-activity scores, tender joint count, swollen joint count and physician's global assessment, but not CRP or patient's global assessment displayed a similar correlation with the expression of TNFaα-dependent genes. In addition, TNFaα-induced genes were also significantly enriched in transcripts over-expressed in synovial biopsy samples obtained from poor-responders to methotrexate or tocilizumab, prior to initiation of therapy. GADD45B (induced by TNFaα in monocytes) and PDE4D (induced by TNFaα in FLS) immunostaining was significantly higher in overall poor-responders to therapy in 46 independent baseline samples obtained from early untreated RA patients prior to initiation of therapy. GADD45B (but not PDE4D) immunostaining was significantly higher in the sub-group of patients with poor-response to methotrexate therapy, and this was confirmed in another population of methotrexate-treated patients. Conclusion: Higher expression of TNFaα-induced transcripts in early RA synovitis is associated with higher disease activity, and predicts poor response to first-line therapy. That over-expression of TNFaα-induced genes predicts poor-response to therapy regardless of the drug administered, indicates that this molecular signature is associated with disease severity, rather than with specific pathways of escape to therapy., SCOPUS: ar.j, info:eu-repo/semantics/published

The Journal of Rheumatology Copyright © 2016. All rights reserved., Objective: Because limited data currently support the clinical utility of peripherally expressed biomarkers in guiding treatment decisions for patients with rheumatoid arthritis, the search has turned to the disease tissue. The strategic aim of the Outcome Measures in Rheumatology (OMERACT) synovitis working group over the years has been to develop novel diagnostic and prognostic synovial biomarkers. A critical step in this process is to refine and validate minimally invasive, technically simple, robust techniques to sample synovial tissue, for use both in clinical trials and routine clinical practice. The objective of the synovitis working group (SWG) at OMERACT 12 (2014) was to examine whether recently developed ultrasound (US)-guided synovial biopsy techniques could be validated according to the OMERACT filter for future clinical use recommendation. Methods: The SWG examined whether current data reporting US-guided synovial biopsy of both large and small joints addressed the OMERACT filters of truth, discrimination, and feasibility. Results: There are currently limited data examining the performance of US-guided synovial biopsy, mainly from observational studies. Thus, it remains critical to evaluate its performance, within the clinical trials context, against the current gold standard of arthroscopic biopsy, with particular reference to: (1) synovial tissue yield, (2) capacity to determine treatment response as measured by a validated synovial biomarker, and (3) tolerability of the procedure. Conclusion: We summarize the discrete work packages agreed to as requirements to validate US-guided synovial biopsy and therefore lead to a global consensus on the use of synovial biopsy for research and clinical practice.

Sjogren’s syndrome (SS) is an autoimmune, chronic inflammatory disease characterized by focal mononuclear cell infiltration of exocrine tissues. The pathogenesis of the disease is difficult to study both in humans and in vitro. Animal models provide a powerful tool in the study of tissue pathology, in the identification of target antigens and pathological immune mechanisms. This chapter summarizes current knowledge on murine strains, both spontaneous and induced models, used to study SS.

Objective To show that a new recombinant protein (MT07) obtained by fusing a synovial-homing peptide to a neutralizing antibody to C5 can be selectively delivered to inflamed synovium and can effectively control joint inflammation in experimental models of arthritis. Methods Binding of MT07 to human, rat, and mouse synovial tissue was evaluated in vitro by immunofluorescence, and selective localization in the inflamed joints of rats was documented in vivo using time-domain optical imaging. The antiinflammatory effect of MT07 was tested in a rat model of antigen-induced arthritis (AIA) and in a mouse model of collagen antibody–induced arthritis (CAIA). Results MT07 was able to bind to samples of inflamed synovium from humans, mice, and rats while failing to recognize uninflamed synovium as well as inflamed mouse lung or rat kidney. In vivo analysis of the biodistribution of MT07 confirmed its preferential homing to inflamed joints, with negligible inhibition of circulating C5 levels. MT07 prevented and resolved established inflammation in a rat model of AIA, as demonstrated by changes in joint swelling, polymorphonuclear cell counts in synovial washes, release of interleukin-6 and tumor necrosis factor α, and tissue damage. A similar therapeutic effect was obtained testing MT07 in a CAIA model. Conclusion Our findings show that the novel recombinant molecule MT07 has the unique ability to selectively target inflamed joints and to exert local control of the inflammatory process by neutralizing the complement system without interfering with circulating C5 levels. We believe that this approach can be extended to other antiinflammatory drugs currently used to treat patients with rheumatoid arthritis.

Objectives The synovial endothelium targeting peptide (SyETP) CKSTHDRLC has been identified previously and was shown to preferentially localise to synovial xenografts in the human/severe combined immunodeficient (SCID) mouse chimera model of rheumatoid arthritis (RA). The objective of the current work was to generate SyETP-anti-inflammatory-cytokine fusion proteins that would deliver bioactive cytokines specifically to human synovial tissue. Methods Fusion proteins consisting of human interleukin (IL)-4 linked via a matrix metalloproteinase (MMP)-cleavable sequence to multiple copies of either SyETP or scrambled control peptide were expressed in insect cells, purified by Ni-chelate chromatography and bioactivity tested in vitro. The ability of SyETP to retain bioactive cytokine in synovial but not control skin xenografts in SCID mice was determined by in vivo imaging using nano-single-photon emission computed tomography-computed tomography (nano-SPECT-CT) and measuring signal transducer and activator of transcription 6 (STAT6) phosphorylation in synovial grafts following intravenous administration of the fusion protein. Results In vitro assays confirmed that IL-4 and the MMP-cleavable sequence were functional. IL-4-SyETP augmented production of IL-1 receptor antagonist (IL-1ra) by fibroblast-like synoviocytes (FLS) stimulated with IL-1β in a dose-dependent manner. In vivo imaging showed that IL-4-SyETP was retained in synovial but not in skin tissue grafts and the period of retention was significantly enhanced through increasing the number of SyETP copies from one to three. Finally, retention correlated with increased bioactivity of the cytokine as quantified by STAT6 phosphorylation in synovial grafts. Conclusions The present work demonstrates that SyETP specifically delivers fused IL-4 to human rheumatoid synovium transplanted into SCID mice, thus providing a proof of concept for peptide-targeted tissue-specific immunotherapy in RA. This technology is potentially applicable to other biological treatments providing enhanced potency to inflammatory sites and reducing systemic toxicity.

A sizeable subset of patients with the two most common organ-specific rheumatic autoimmune diseases, rheumatoid arthritis (RA) and Sjögren's syndrome (SS) develop ectopic lymphoid structures (ELS) in the synovial tissue and salivary glands, respectively. These structures are characterized by perivascular (RA) and periductal (SS) clusters of T and B lymphocytes, differentiation of high endothelial venules and networks of stromal follicular dendritic cells (FDC). Accumulated evidence from other and our group demonstrated that the formation and maintenance of ELS in these chronic inflammatory conditions is critically dependent on the ectopic expression of lymphotoxins (LT) and lymphoid chemokines CXCL13, CCL19, CCL21 and CXCL12. In this review we discuss recent advances highlighting the cellular and molecular mechanisms, which regulate the formation of ELS in RA and SS, with particular emphasis on the role of lymphoid chemokines. In particular, we shall focus on the evidence that in the inflammatory microenvironment of the RA synovium and SS salivary glands, several cell types, including resident epithelial, stromal and endothelial cells as well as different subsets of infiltrating immune cells, have been shown to be capable of producing lymphoid chemokines. Finally, we summarize accumulating data supporting the conclusion that ELS in RA and SS represent functional niches for B cells to undergo affinity maturation, clonal selection and differentiation into plasma cells autoreactive against disease-specific antigens, thus contributing to humoral autoimmunity over and above that of secondary lymphoid organs.

Salivary glands in patients with Sjögren’s syndrome (SS) develop ectopic lymphoid structures (ELS) characterized by B/T cell compartmentalization, the formation of high endothelial venules, follicular dendritic cell networks, functional B cell activation with expression of activation-induced cytidine deaminase, as well as local differentiation of autoreactive plasma cells. The mechanisms that trigger ELS formation, autoimmunity, and exocrine dysfunction in SS are largely unknown. In this article, we present a novel model of inducible ectopic lymphoid tissue formation, breach of humoral self-tolerance, and salivary hypofunction after delivery of a replication-deficient adenovirus-5 in submandibular glands of C57BL/6 mice through retrograde excretory duct cannulation. In this model, inflammation rapidly and consistently evolves from diffuse infiltration toward the development of SS-like periductal lymphoid aggregates within 2 wk from AdV delivery. These infiltrates progressively acquire ELS features and support functional GL7+/activation-induced cytidine deaminase+ germinal centers. Formation of ELS is preceded by ectopic expression of lymphoid chemokines CXCL13, CCL19, and lymphotoxin-β, and is associated with development of anti-nuclear Abs in up to 75% of mice. Finally, reduction in salivary flow was observed over 3 wk post-AdV infection, consistent with exocrine gland dysfunction as a consequence of the inflammatory response. This novel model has the potential to unravel the cellular and molecular mechanisms that regulate ELS formation and their role in exocrine dysfunction and autoimmunity in SS.

Objective To isolate recombinant antibodies with specificity for human arthritic synovium and to develop targeting reagents with joint-specific delivery capacity for therapeutic and/or diagnostic applications. Methods In vivo single-chain Fv (scFv) antibody phage display screening using a human synovial xenograft model was used to isolate antibodies specific to the microvasculature of human arthritic synovium. Single-chain Fv antibody tissue-specific reactivity was assessed by immunostaining of synovial tissues from normal controls and from patients with rheumatoid arthritis and osteoarthritis, normal human tissue arrays, and tissues from other patients with inflammatory diseases displaying neovasculogenesis. In vivo scFv antibody tissue-specific targeting capacity was examined in the human synovial xenograft model using both 125I-labeled and biotinylated antibody. Results We isolated a novel recombinant human antibody, scFv A7, with specificity for the microvasculature of human arthritic synovium. We showed that in vivo, this antibody could efficiently target human synovial microvasculature in SCID mice transplanted with human arthritic synovial xenografts. Our results demonstrated that scFv A7 antibody had no reactivity with the microvasculature or with other cellular components found in a comprehensive range of normal human tissues including normal human synovium. Further, we showed that the reactivity of the scFv A7 antibody was not a common feature of neovasculogenesis associated with chronic inflammatory conditions. Conclusion Here we report for the first time the identification of an scFv antibody, A7, that specifically recognizes an epitope expressed in the microvasculature of human arthritic synovium and that has the potential to be developed as a joint-specific pharmaceutical.

Rheumatoid arthritis (RA) is a chronic disease of unspecified etiology that is manifest by persistent inflammation of the synovium. Considerable efforts have been undertaken globally to study the microenvironment of the inflamed synovium, with many encouraging and enlightening results that bring us closer to unmasking the precise etiologies of RA. Subsequent to these efforts, it has been discovered that CD68-positive macrophages present in abundance in the synovial sublining of the inflamed synovium rescind with treatments that induce clinical improvement in RA. Examination of serial synovial biopsies is now commonly used for screening purposes during early drug development, and the number of centers able to perform synovial tissue biopsy sampling according to standardized methods is increasing.Having implemented the use of serial synovial tissue biopsies to evaluate the effects of new treatments on the group level in early proof of principle studies, it is the ambition of the OMERACT Synovial Tissue Group to identify synovial diagnostic and prognostic biomarkers that could be used in individual patients. Therefore, we started a prospective study termed the Synoviomics Project aimed at the identification of novel diagnostic and prognostic synovial biomarkers. We will use straightforward and powerful technologies to analyze patient material and assess clinical parameters to identify such biomarkers. These markers may be used in the future to identify patients who are at risk of having persistent and destructive disease and to start tailor-made targeted therapies in an early phase to prevent autonomous disease progression and irreversible joint damage.

A single Wnt can simultaneously activate different pathways with distinct and independent outcomes and reciprocal regulation in human articular chondrocytes., Activation and disruption of Wnt/β-catenin signaling both result in cartilage breakdown via unknown mechanisms. Here we show that both WNT-3A and the Wnt inhibitor DKK1 induced de-differentiation of human articular chondrocytes through simultaneous activation of β-catenin–dependent and independent responses. WNT-3A activates both the β-catenin–dependent canonical pathway and the Ca2+/CaMKII noncanonical pathways, with distinct transcriptional targets. WNT-3A promotes cell proliferation and loss of expression of the chondrocyte markers COL2A1, Aggrecan, and SOX9; however, proliferation and AXIN2 up-regulation are downstream of the canonical pathway and are rescued by DKK1, whereas the loss of differentiation markers is CaMKII dependent. Finally, we showed that in chondrocytes, the Ca2+/CaMKII-dependent and β-catenin–dependent pathways are reciprocally inhibitory, thereby explaining why DKK1 can induce loss of differentiation through de-repression of the CaMKII pathway. We propose a novel model in which a single WNT can simultaneously activate different pathways with distinct and independent outcomes and with reciprocal regulation. This offers an opportunity for selective pharmacological targeting.

ObjectivesTo dissect the role of toll-like receptor (TLR) signalling and B cell survival/proliferating factors in the crosstalk between rheumatoid arthritis synovial fibroblasts (RASF) and B cells.MethodsRASF, rheumatoid arthritis dermal fibroblasts (RADF) and osteoarthritis synovial fibroblasts (OASF) were analysed for the expression of B cell survival/proliferating factors BAFF and APRIL in resting conditions and upon stimulation with TLR2/TLR3/TLR4 ligands. Unswitched IgD+ B cells were co-cultured with RASF/OASF/RADF in the presence/absence of TLR ligands and with/without BAFF/APRIL blocking antibodies. Activation-induced cytidine deaminase (AID) mRNA expression, Iγ-Cμ and Iα-Cμ circular transcripts (CTs; markers of ongoing class-switching to IgG and IgA) and IgM/A/G production were measured to assess functional activation of B cells.ResultsTLR3 and to a lesser extent TLR4, but not TLR2 stimulation, induced up to ∼1000-fold BAFF mRNA and increased soluble BAFF release. APRIL was less significantly regulated by TLR3. Resting and TLR3-stimulated RASF released higher levels of BAFF/APRIL compared with RADF. TLR3 stimulation of RASF but not RADF in co-culture with B cells strongly enhanced AID expression, Iγ-Cμ and Iα-Cμ CTs and class-switching to IgG/IgA. Blockade of BAFF/APRIL signalling completely inhibited TLR3-induced, RASF-dependent expression of AID, CTs and the secretion of IgG/IgA.ConclusionsRASF produce high levels of BAFF and APRIL constitutively and in response to TLR3 stimulation. These factors are critical in directly modulating AID expression, class-switch recombination and IgG/IgA production in IgD+ B cells. Overall, this work highlights a novel and fundamental role for the TLR3/B cell survival factor axis in sustaining B cell activation in the rheumatoid arthritis synovium.

The development of biological therapies has improved management of rheumatoid arthritis. However, costs and unresponsiveness to therapy in a sizeable proportion of patients limit their use, making it imperative to identify new targets for drug development programs. Here we investigated the melanocortin-receptor type 3 (MC(3)) pathway. Gene-deficient mice were subjected to a model of serum-transfer-induced arthritis and joints analyzed for gene expression (cytokines, MCs) and morphology. Pharmacological analyses were also conducted in this model. Osteoclastogenesis was studied from bone marrow cells. Mc(3)(-/-) mice displayed an exacerbated inflammatory arthritis, associated with prominent bone erosion and higher articular expression of Rankl. Osteoclastogenesis studied from Mc(3)(-/-) bone marrow cells revealed a higher degree of responsiveness to Rankl, linked to prolonged NF-κB activation compared to wild types. Up-regulation of a discrete set of inflammatory genes, including Il-1β, Il-6, and Nos2, was measured in Mc(3)(-/-) mice, and a marked up-regulation of joint Mc(3) accompanied arthritis resolution in wild-type mice. Administration of an MC(3) agonist, D[Trp8]-γ-MSH, attenuated disease incidence and severity in wild-type but not Mc(3)(-/-) mice. Overall, these findings identify MC(3)-mediated signaling as a beneficial pathway in experimental arthritis; hence this receptor is a novel target for the development of therapeutics for arthritis.

OBJECTIVES: Subclinical gut inflammation has been demonstrated in patients with AS. Altered expression of paneth cell (PC) anti-microbial peptides have been reported in the inflamed ileum of patients with Crohn's disease (CD). Here, we investigated the expression of PC-derived peptides in subclinical gut inflammation in AS. METHODS: Multiple adjacent mucosal biopsies from terminal ileum were obtained from 25 patients with AS, 30 CD and 15 healthy controls (HCs). Expression of human α-defensin 5 (HD-5), phospholipase A2 (PLA2), lysozyme and SOX-9 molecules was assessed by quantitative Taqman RT-PCR on mucosal samples. Immunohistochemistry with anti-human HD-5 antibody and genotyping of relevant NOD2 mutations was also performed. RESULTS: HD-5, PLA2 and lysozyme transcript levels were strongly increased in AS and CD with similar degrees of intestinal inflammation when compared with normal controls. Immunohistochemical evaluation showed a normal number of PCs in both AS patients with chronic gut inflammation and CD patients with less-inflamed ileal samples. Conversely, CD patients with higher degree of gut inflammation had a reduced number of PCs and low expression levels of HD-5. CONCLUSION: In this study, we provide evidence that over-expression of PC-derived anti-microbial peptides occurs in the ileum of AS patients with subclinical gut inflammation, likely representing an important early alteration of the mucosal innate immune component and intestinal host defence in AS.

Serum amyloid A (A-SAA), an acute-phase protein with cytokine-like properties, is expressed at sites of inflammation. This study investigated the effects of A-SAA on chemokine-regulated migration and angiogenesis using rheumatoid arthritis (RA) cells and whole-tissue explants in vitro, ex vivo, and in vivo. A-SAA levels were measured by real-time PCR and ELISA. IL-8 and MCP-1 expression was examined in RA synovial fibroblasts, human microvascular endothelial cells, and RA synovial explants by ELISA. Neutrophil transendothelial cell migration, cell adhesion, invasion, and migration were examined using transwell leukocyte/monocyte migration assays, invasion assays, and adhesion assays with or without anti–MCP-1/anti–IL-8. NF-κB was examined using a specific inhibitor and Western blotting. An RA synovial/SCID mouse chimera model was used to examine the effects of A-SAA on cell migration, proliferation, and angiogenesis in vivo. High expression of A-SAA was demonstrated in RA patients (p < 0.05). A-SAA induced chemokine expression in a time- and dose-dependent manner (p < 0.05). Blockade with anti-scavenger receptor class B member 1 and lipoxin A4 (A-SAA receptors) significantly reduced chemokine expression in RA synovial tissue explants (p < 0.05). A-SAA induced cell invasion, neutrophil–transendothelial cell migration, monocyte migration, and adhesion (all p < 0.05), effects that were blocked by anti–IL-8 or anti–MCP-1. A-SAA–induced chemokine expression was mediated through NF-κB in RA explants (p < 0.05). Finally, in the RA synovial/SCID mouse chimera model, we demonstrated for the first time in vivo that A-SAA directly induces monocyte migration from the murine circulation into RA synovial grafts, synovial cell proliferation, and angiogenesis (p < 0.05). A-SAA promotes cell migrational mechanisms and angiogenesis critical to RA pathogenesis.

Autoantibodies play a significant role in the progression and pathogenesis of many autoimmune diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). No studies have analyzed the expression of plasma cell/plasmablast genes during RA disease progression and the potential of an anti-CD38 antibody in depleting plasma cells and plasmablasts for efficacy in autoimmunity. Therefore, we interrogated the rationale of daratumumab, an anti-CD38 monoclonal antibody, as a potential therapeutic in RA and SLE. RNA-Seq analysis of synovial biopsies from various stages of RA disease development shows that plasma cell/plasmablast-related genes CD38, XBP1, IRF4, PRDM1, IGJ and TNFSF13B are significantly up-regulated in synovial biopsies from arthralgia, undifferentiated arthritis, early RA and established RA compared to healthy and osteoarthritis controls. In addition, flow cytometry analysis reveals highest CD38 expression on plasma cells and plasmablasts compared to natural killer cells, classical dendritic cell (DC), plasmacytoid DC, and T cells, in peripheral blood of healthy control, SLE and RA donors. We show that IGJ expression mRNA strongly correlates with the number of plasma cell/plasmablast in SLE patient PBMCs. Most importantly, IGJ mRNA down-regulation correlates with daratumumab-mediated depletion of these cells ex vivo. The data indicates a potential use of IGJ mRNA as a surrogate pharmacodynamic biomarker in clinical testing of daratumumab. Taken together, our data provides rationale for daratumumab in the treatment of RA and SLE.

We thank Mossel and colleagues for their interest in our work.1 2 They raise a number of limitations that we acknowledge and have discussed. In addition, we agree that an understanding of the pathology underlying the abnormal salivary gland ultrasound findings in Sjogren’s syndrome is an important objective to help establish the validity of this tool as a potential outcome measure in clinical trials. As both we and Mossel and colleagues discuss, we did not observe a difference in hypoechoic areas between rituximab and placebo. Similar hypoechoic areas can be observed in long-standing postradiotherapy salivary glands where inflammatory cell infiltrate is variable and of a differing pattern.3–5 Furthermore, the pattern of hypoechoic areas on ultrasound in Sjogren’s syndrome is reminiscent of sialography findings which are characterised by contrast-defined changes …

Immune checkpoint blockade with therapeutic anti-cytotoxic T lymphocyte-associated antigen (CTLA)-4 (Ipilimumab) and anti-programmed death (PD)-1 (Nivolumab and Pembrolizumab) antibodies alone or in combination has shown remarkable efficacy in multiple cancer types, concomitant with immune-related adverse events, including arthralgia and inflammatory arthritis (IA) in some patients. Herein, using Nivolumab (anti-PD-1 antagonist)-responsive genes along with transcriptomics of synovial tissue from multiple stages of rheumatoid arthritis (RA) disease progression, we have interrogated the activity status of PD-1 pathway during RA development. We demonstrate that the expression of PD-1 was increased in early and established RA synovial tissue compared to normal and OA synovium, whereas that of its ligands, programmed death ligand-1 (PD-L1) and PD-L2, was increased at all the stages of RA disease progression, namely arthralgia, IA/undifferentiated arthritis, early RA and established RA. Further, we show that RA patients expressed PD-1 on a majority of synovial tissue infiltrating CD4+ and CD8+ T cells. Moreover, enrichment of Nivolumab gene signature was observed in IA and RA, indicating that the PD-1 pathway was downregulated during RA disease progression. Furthermore, serum soluble (s) PD-1 levels were increased in autoantibody positive early RA patients. Interestingly, most of the early RA synovium tissue sections showed negative PD-L1 staining by immunohistochemistry. Therefore, downregulation in PD-1 inhibitory signaling in RA could be attributed to increased serum sPD-1 and decreased synovial tissue PD-L1 levels. Taken together, these data suggest that agonistic PD1 antibody-based therapeutics may show efficacy in RA treatment and interception.

Objective— The proinflammatory phenotype induced by low laminar shear stress (LSS) is implicated in atherogenesis. The kinin B1 receptor (B1R), known to be induced by inflammatory stimuli, exerts many proinflammatory effects including vasodilatation and leukocyte recruitment. We investigated whether low LSS is a stimulus for endothelial B1R expression and function. Methods and Results— Human and mouse atherosclerotic plaques expressed high level of B1R mRNA and protein. In addition, B1R expression was upregulated in the aortic arch (low LSS region) of ApoE −/− mice fed a high-fat diet compared to vascular regions of high LSS and animals fed normal chow. Of interest, a greater expression of B1R was noticed in endothelial cells from regions of low LSS in aortic arch of ApoE −/− mice. B1R was also upregulated in human umbilical vein endothelial cells (HUVECs) exposed to low LSS (0 to 2 dyn/cm 2 ) compared to physiological LSS (6 to 10 dyn/cm 2 ): an effect similarly evident in murine vascular tissue perfused ex vivo. Functionally, B1R activation increased prostaglandin and CXCL5 expression in cells exposed to low, but not physiological, LSS. IL-1β and ox-LDL induced B1R expression and function in HUVECs, a response substantially enhanced under low LSS conditions and inhibited by blockade of NFκB activation. Conclusion— Herein, we show that LSS is a major determinant of functional B1R expression in endothelium. Furthermore, whereas physiological high LSS is a powerful repressor of this inflammatory receptor, low LSS at sites of atheroma is associated with substantial upregulation, identifying this receptor as a potential therapeutic target.

Objective—Junctional adhesion molecule-C (JAM-C) is an adhesion molecule that has multiple roles in inflammation and vascular biology, but many aspects of its functions under pathological conditions are unknown. Here we investigated the role of JAM-C in leukocyte migration in response to ischemia reperfusion (I/R) injury.Methods and Results—Pretreatment of mice with soluble JAM-C (sJAM-C), used as a pharmacological blocker of JAM-C-mediated reactions, significantly suppressed leukocyte migration in models of kidney and cremaster muscle I/R injury (39 and 51% inhibition, respectively). Furthermore, in the cremaster muscle model (studied by intravital microscopy), both leukocyte adhesion and transmigration were suppressed in JAM-C-deficient mice (JAM-C−/−) and enhanced in mice overexpressing JAM-C in their endothelial cells (ECs). Analysis of JAM-C subcellular expression by immunoelectron microscopy indicated that in I/R-injured tissues, EC JAM-C was redistributed from cytoplasmic vesicles and EC junctional sites to nonjunctional plasma membranes, a response that may account for the role of JAM-C in both leukocyte adhesion and transmigration under conditions of I/R injury.Conclusions—The findings demonstrate a role for EC JAM-C in mediating leukocyte adhesion and transmigration in response to I/R injury and indicate the existence of a novel regulatory mechanism for redistribution and hence function of EC JAM-C in vivo.

Objective. The purpose of this study was to explore the development of a pre-clinical nuclear imaging model as a tool for testing novel radiopharmaceutical agents for imaging and/or delivery systems to human tissues. Here we report for the first time the imaging of human synovial tissue transplanted into SCID mice using a radiolabelled anti-E-selectin antibody and NanoSPECT/CT technology. Methods. Human synovium was transplanted into SCID mice. Two to three weeks post-transplantation tissue vasculature was stimulated with TNF-� by intra-graft injection 5 h prior to intravenous injection of 111 In-labelled anti-E-selectin or isotype control antibody. At 1, 4, 24 and 48 h animals were imaged and transplant activity quantified. Results. Activity was detectable in the grafts at all time points, with clear delineation of the transplants in the reconstructed images. A significant difference in graft radioactivity was observed at 4 and 24 h with a significantly higher uptake (P < 0.05) of 111 In-anti-E-selectin compared with isotype control antibody. Conclusions. This article highlights NanoSPECT/CT imaging in the SCID mouse chimeric model as a powerful tool for the pre-clinical development of radiopharmaceutical and delivery agents targeting human synovial tissue in vivo.

Th17 cells are a recently defined subset of proinflammatory T cells that contribute to pathogen clearance and tissue inflammation by means of the production of their signature cytokine IL-17A (henceforth termed IL-17). Although the in vitro requirements for human Th17 development are reasonably well established, it is less clear what their in vivo requirements are. Here, we show that the production of IL-17 by human Th17 cells critically depends on both the activation status and the anatomical location of accessory cells. In vivo activated CD14+ monocytes were derived from the inflamed joints of patients with active rheumatoid arthritis (RA). These cells were found to spontaneously and specifically promote Th17, but not Th1 or Th2 responses, compared with resting CD14+ monocytes from the blood. Surprisingly, unlike Th17 stimulation by monocytes that were in vitro activated with lipopolysaccharide, intracellular IL-17 expression was induced by in vivo activated monocytes in a TNF-α- and IL-1β-independent fashion. No role for IL-6 or IL-23 production by either in vitro or in vivo activated monocytes was found. Instead, in vivo activated monocytes promoted Th17 responses in a cell-contact dependent manner. We propose that, in humans, newly recruited memory CD4 + T cells can be induced to produce IL-17 in nonlymphoid inflamed tissue after cell–cell interactions with activated monocytes. Our data also suggest that different pathways may be utilized for the generation of Th17 responses in situ depending on the site or route of accessory cell activation.

Objective Synovial B cells play a critical role in rheumatoid arthritis (RA), being involved in autoantibody synthesis, T cell activation, and cytokine production. CXCL13 is a B cell chemoattractant that is instrumental in synovial B cell organization; the regulatory determinants of CXCL13 in inflammation are poorly characterized. This study was undertaken to investigate the functional involvement of synovial T cells in the ectopic expression of CXCL13 in RA. Methods CXCL13 production and regulation were addressed using immunohistochemistry, in situ hybridization, quantitative polymerase chain reaction, multicolor flow cytometry, and enzyme-linked immunosorbent assay, by in situ–ex vivo analysis and in vitro functional assays with rheumatoid synovial tissue and primary cells. Results CXCL13 messenger RNA and protein expression and spontaneous CXCL13 secretion were detected in RA synovial fluid T cells but were not detected (or were detected only occasionally) in peripheral blood T cells. Analysis of tissue expression confirmed cytoplasm localization of CXCL13 in T lymphocytes infiltrating B cell follicles and small perivascular aggregates. Multicolor characterizations in synovial fluid demonstrated CXCL13 expression in antigen-experienced T helper cells, frequently characterized by terminal differentiation and the lack of the follicular helper T cell markers CXCR5 and BCL6 protein. In vitro functional assays revealed the enhancing effect of T cell receptor–CD28 engagement on CXCL13 production and secretion in primary cells. Conclusion Our findings define a new functional property of synovial T cells, demonstrating their active involvement in the local production of B cell chemoattractants, and support a direct contribution of the adaptive immune system and antigen-dependent signals in the mechanisms of B cell localization in RA.

Objective To characterize the molecular response of adult human articular cartilage to acute mechanical injury. Methods An established ex vivo model was used to compare gene expression of adult human articular cartilage explants 24 hours after mechanical injury with that of uninjured controls by microarray analysis of gene expression. Confirmation for selected genes was obtained by real-time polymerase chain reaction and immunohistochemical analysis. Expression of selected genes was also investigated in preserved and osteoarthritic (OA) cartilage. Results Six hundred ninety genes were significantly regulated at least 2-fold following mechanical injury. They included genes previously reported to be differentially expressed in OA versus normal cartilage or having allelic variants genetically linked to OA. Significant functional clusters included genes associated with wound healing, developmental processes, and skeletal development. The transforming growth factor β, fibroblast growth factor, and Wnt pathways were modulated. A systematic analysis of the Wnt signaling pathway revealed up-regulation of Wnt-16, down-regulation of FRZB, up-regulation of Wnt target genes, and nuclear localization of β-catenin in injured cartilage. In addition, in OA, Wnt-16 and β-catenin were barely detectable in preserved cartilage areas, but were dramatically up-regulated in areas of the same joint with moderate to severe OA damage. Conclusion Our findings indicate that mechanical injury to adult human articular cartilage results in the activation of a signaling response, with reactivation of morphogenetic pathways. Therapeutic targeting of such pathways may improve current protocols of joint surface defect repair and/or prevent the evolution of such lesions into posttraumatic OA.

Frequently, the immune cell infiltrate of chronically inflamed tissues develops functional germinal centres and acquires structural features of secondary lymphoid organs. Ectopic lymphoid structures occur in peripheral tissues not only during autoimmune diseases but also in tumors (reactive infiltrate), chronic infections and graft rejection, indicating a strong link between lymphoid neogenesis and persistent antigen driven immune/inflammatory responses. There has been a renewed interest in ectopic lymphoid neogenesis, as better understanding of the mechanisms underpinning this process could contribute to elucidate the bio-pathological mechanisms involved in transition from acute-self resolving to chronic immunological aggression as well as identify novel therapeutic targets. Here we critically review recent clinical and biological studies addressing the role of ectopic lymphoid neogenesis specifically in rheumatoid arthritis.

Demonstration of ectopic germinal center-like structures (GC-LSs) in chronically inflamed tissues in patients with autoimmune disorders is a relatively common finding. However, to what extent ectopic lymphoid structures behave as true GC and are able to support class switch recombination (CSR) and somatic hypermutation (SHM) of the Ig genes is still debated. In addition, no information is available on whether CSR and SHM can take place in the absence of GCs at extrafollicular sites in an ectopic lymphoid tissue. In this study, we show that in salivary glands (SGs) of Sjögren’s syndrome (SS) activation-induced cytidine deaminase (AID), the enzyme responsible for CSR and SHM is invariably expressed within follicular dendritic cell (FDC) networks but is not detectable in SGs in the absence of ectopic GC-LSs, suggesting that FDC networks play an essential role in sustaining the Ag-driven B cell proliferation within SS-SGs. We also show that the recently described population of interfollicular large B cells selectively expresses AID outside ectopic GC in the T cell-rich areas of periductal aggregates. Finally, we report that AID retains its exclusive association with numerous, residual GCs in parotid SS-MALT lymphomas, whereas neoplastic marginal zone-like B cells are consistently AID negative. These results strongly support the notion that ectopic lymphoid structures in SS-SGs express the molecular machinery to support local autoantibody production and B cell expansion and may play a crucial role toward lymphomagenesis.

Made available in DSpace on 2018-12-11T17:00:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-11-25 Microvesicles (MVs) are emerging as a new mechanism of intercellular communication by transferring cellular lipid and protein components to target cells, yet their function in disease is only now being explored. We found that neutrophilderived MVs were increased in concentration in synovial fluid from rheumatoid arthritis patients compared to paired plasma. Synovial MVs overexpressed the proresolving, anti-inflammatory protein annexin A1 (AnxA1). Mice deficient in TMEM16F, a lipid scramblase required for microvesiculation, exhibited exacerbated cartilage damage when subjected to inflammatory arthritis. To determine the function of MVs in inflammatory arthritis, toward the possibility of MV-based therapeutics, we examined the role of immune cell-derived MVs in rodent models and in human primary chondrocytes. In vitro, exogenous neutrophil-derived AnxA1+ MVs activated anabolic gene expression in chondrocytes, leading to extracellular matrix accumulation and cartilage protection through the reduction in stress-adaptive homeostatic mediators interleukin-8 and prostaglandin E2. In vivo, intra-articular injection of AnxA1+ MV lessened cartilage degradation caused by inflammatory arthritis. Arthritic mice receiving adoptive transfer of whole neutrophils displayed abundant MVs within cartilage matrix and revealed that MVs, but not neutrophils themselves, can penetrate cartilage. Mechanistic studies support a model whereby MV-associated AnxA1 interacts with its receptor FPR2 (formyl peptide receptor 2)/ALX, increasing transforming growth factor-p production by chondrocytes, ultimately leading to cartilage protection. We envisage that MVs, either directly or loaded with therapeutics, can be harnessed as a unique therapeutic strategy for protection in diseases associated with cartilage degeneration. William Harvey Research Institute Barts and The London School of Medicine Queen Mary University of London, Charterhouse Square Department of Physiology Howard Hughes Medical Institute University of California San Francisco Department of Biology Instituto de Biociências Letras e Ciências Exatas São Paulo State University (UNESP) Department of Rheumatology Barts Health Trust, Bancroft Road Department of Biology Instituto de Biociências Letras e Ciências Exatas São Paulo State University (UNESP)

Significance Ectopic clusters of immune cells that mimic the structure and function of secondary lymphoid organs are defined as tertiary lymphoid organs (TLOs). They have been observed at sites of chronic inflammation for decades, but their formation and function have remained enigmatic. TLOs are thought to contribute to disease pathogenesis by promoting autoreactive lymphocyte survival and autoantibody production. In this study we identify a novel role for the cytokine IL-22 in TLO development and biology. We provide evidence that IL-22 expression within TLOs is instrumental for the production of the lymphoid chemokines, chemokine (C-X-C motif) ligand 13 and chemokine (C-X-C motif) ligand 12, which in turn orchestrate B-cell clustering, lymphoid aggregation, and autoantibody production. Our data provide a strong rationale for targeting IL-22 in TLO-associated autoimmune diseases.

Rheumatoid arthritis (RA) is a chronic, systemic, autoimmune disease that leads to excessive joint inflammation and is associated with significant morbidity and mortality. Although much is still to be learned about the aetiology RA, a growing body of evidence suggests that an altered vascular environment is an important aspect of its pathophysiology. In this context, RA shares many similarities with cancer, and it is expected that several angiogenic targets in cancer might be relevant to the treatment of RA. Here, we discuss how these targets can be combined with advances in drug development to generate the next generation of RA therapeutics.

Introduction Neovascularization contributes to the development of sustained synovial inflammation in the early stages of Rheumatoid Arthritis. Ultrasound (US) provides an indirect method of assessing synovial blood flow and has been shown to correlate with clinical disease activity in patients with Rheumatoid Arthritis. This study examines the relationship of US determined synovitis with synovial vascularity, angiogenic / lymphangiogenic factors and cellular mediators of inflammation in a cohort of patients with early Rheumatoid Arthritis (RA) patients prior to therapeutic intervention with disease modifying therapy or corticosteroids. Methods An ultrasound guided synovial biopsy of the supra-patella pouch was performed in 12 patients with early RA prior to treatment. Clinical, US and biochemical assessments were undertaken prior to the procedure. Ultrasound images and histological samples were obtained from the supra-patella pouch. Histological samples were stained for Factor VIII and a-SMA (a-smooth muscle actin). Using digital imaging analysis a vascular area score was recorded. QT-PCR (quantitative-PCR) of samples provided quantification of angiogenic and lymphangiogenic gene expression and immunohistochemistry stained tissue was scored for macrophage, T cell and B cell infiltration using an existing semi-quantitative score. Results Power Doppler showed a good correlation with histological vascular area (Spearman r - 0.73) and angiogenic factors such as vascular endothelial growth factor- A (VEGF-A), Angiopoietin 2 and Tie-2. In addition, lymphangiogenic factors such as VEGF-C and VEGF-R3 correlated well with US assessment of synovitis. A significant correlation was also found between power Doppler and synovial thickness, pro-inflammatory cytokines and sub-lining macrophage infiltrate. Within the supra-patella pouch there was no significant difference in US findings, gene expression or inflammatory cell infiltrate between any regions of synovium biopsied. Conclusion Ultrasound assessment of synovial tissue faithfully reflects synovial vascularity. Both grey scale and power Doppler synovitis in early RA patients correlate with a pro-angiogenic and lymphangiogenic gene expression profile. In early RA both grey scale and power Doppler synovitis are associated with a pro-inflammatory cellular and cytokine profile providing considerable validity in its use as an objective assessment of synovial inflammation in clinical practice.

Ultrasound-guided synovial biopsy (UGSB) is a minimally-invasive procedure capable of retrieving good quality tissue from small and large joints. The use of UGSB in prospective clinical trials poses a dilemma as to whether biopsied joints may be later included in core data sets for clinical or imagining response, as the procedure itself may alter disease activity assessment. In this study, we examine the impact of UGSB of the wrist on subsequent clinical and ultrasound (US) assessments in a cohort of rheumatoid arthritis (RA) patients prior to initiation of anti-TNF-alpha therapy.Patients had active disease (DAS5.1) involving their wrist. Both wrists were scanned and the most inflamed one underwent an UGSB. Ultrasonographic and clinical assessments were repeated at the patients' subsequent visit, without any changes in disease-modifying treatment between visits. US images were scored semi-quantitatively and quantitatively for synovial thickness (ST) and power Doppler (PD). Mixed-effects model and paired-Wilcoxon signed rank test were used to assess the effect of UGSB on these scores.Twenty-nine patients were enrolled. No significant difference in mean ST (p=0.32) or PD (p=0.21) was demonstrated pre- and post-biopsy (mean time 14.7 days). Similar results were obtained using quantitative measures. The DAS-28 and its components did not change significantly post-biopsy.In this population, UGSB of the wrist did not significantly alter subsequent clinical or US assessments, indicating that a wrist joint, which has undergone UGSB, may be incorporated into an US dataset or clinical outcome assessment tools, such as the DAS-28, without prejudice.

ObjectivesOsteoarthritis (OA) is a leading cause of disability for which there is no cure. The identification of molecules supporting cartilage homeostasis and regeneration is therefore a major pursuit in musculoskeletal medicine. Agrin is a heparan sulfate proteoglycan which, through binding to low-density lipoprotein receptor-related protein 4 (LRP4), is required for neuromuscular synapse formation. In other tissues, it connects the cytoskeleton to the basement membrane through binding to α-dystroglycan. Prompted by an unexpected expression pattern, we investigated the role and receptor usage of agrin in cartilage.MethodsAgrin expression pattern was investigated in human osteoarthritic cartilage and following destabilisation of the medial meniscus in mice. Extracellular matrix (ECM) formation and chondrocyte differentiation was studied in gain and loss of function experiments in vitro in three-dimensional cultures and gain of function in vivo, using an ectopic cartilage formation assay in nude mice. Receptor usage was investigated by disrupting LRP4 and α-dystroglycan by siRNA and blocking antibodies respectively.ResultsAgrin was detected in normal cartilage but was progressively lost in OA. In vitro, agrin knockdown resulted in reduced glycosaminoglycan content, downregulation of the cartilage transcription factor SOX9 and other cartilage-specific ECM molecules. Conversely, exogenous agrin supported cartilage differentiation in vitro and ectopic cartilage formation in vivo. In the context of cartilage differentiation, agrin used an unusual receptor repertoire requiring both LRP4 and α-dystroglycan.ConclusionsWe have discovered that agrin strongly promotes chondrocyte differentiation and cartilage formation in vivo. Our results identify agrin as a novel potent anabolic growth factor with strong therapeutic potential in cartilage regeneration.

Rheumatoid Arthritis (RA) is a chronic, inflammatory, autoimmune disease affecting diarthrodial joints and extra-articular tissues; in the absence of an effective treatment, it is characterized by persistent symmetrical and erosive synovitis which leads to structural joint damage and lifelong disability. Several autoantibodies have been associated with RA such as rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA). B cells have been shown to play a crucial role in the pathogenesis of RA by producing autoantibodies and promoting synovial inflammation through antigen presentation, T cells activation and cytokines production [1]. Although biologic agents have notably improved disease outcome and patients’ quality of life, currently around 30-40% of subjects do not respond to treatment and the mechanisms leading to resistance are still not known [2]. For this reason, new prognostic biomarkers and predictors of response are needed. We and others have postulated that the development of biomarkers for patients’ stratification prior therapeutic intervention may be possible through a better understanding of the different histopathological patterns present both in early and established individual RA patient and the related underlying cellular and molecular mechanisms. To date, Tumor Necrosis Factor (TNF)-α has been shown to be one of the master elements of inflammation in RA; however, even though therapies aimed at blocking this key cytokine have emerged as a major tool in the treatment of RA, a large proportion of patients (approximately 30-40%) do not achieve a meaningful clinical response assessed by either the American College of Rheumatology (ACR) or the European League Against Rheumatism (EULAR) criteria. The same limitation can be applied to the use of rituximab, a chimeric monoclonal antibody directed against CD20, which is uniquely expressed by all B-lymphocytes during the maturation process from late stage pro-B cells to memory cells. The clinical efficacy of rituximab has been proved by several clinical studies [3] but it is highly variable. Currently, NICE guidelines recommend rituximab in patients with inadequate response to a first-line biologic therapy, including at least one anti-TNFα agent independently of their pre-treatment chance to respond. In all cases, whether considering biologics used for several years in RA patients (anti-TNFα or rituximab) or relatively newer biologics in clinical use (i.e. tocilizumab, an anti-interleukin (IL) -6 receptor blocking monoclonal antibody or abatacept, a CTLA4 inhibitor fusion protein designed to target the T cell co-stimulatory signal mediated through the CD28-CD80/86 pathway), no validated biomarkers predictive of clinical response currently exist. Consequently, to date a “trial-and-error” approach is used in the prescription of biologics in RA, which has the obvious disadvantage of potentially exposing patients to drugs that they may not respond, with potential unnecessary side-effects, delaying use of an effective treatment and causing a significant economic burden to society. Therefore, identifying pre-treatment predictors of response with a customized stratification approach would be of invaluable importance in RA, also in consideration of the large number of biologics in development targeting novel pathways currently being tested in clinical trials. In this manuscript, we review existing data and provide future perspectives with regard to the role of synovial histopathology as a potential prognostic biomarker for patient stratification in RA, in particular regarding the use of specific biologic therapies.

OBJECTIVE: To determine the tolerability, safety and yield of synovial tissue in an early arthritis cohort using a minimally invasive, ultrasound (US)-guided, synovial biopsy technique in small, medium and large joints. METHODS: 93 sequential biopsy procedures were assessed from a total of 57 patients (baseline and 36 repeat biopsies at 6 months) recruited as part of the 'Pathobiology of Early Arthritis Cohort' study. Patients completed a tolerability questionnaire prior to and following the synovial biopsy procedure. The synovial biopsy was performed under US guidance with US images of the joint recorded prior to each procedure. Synovial tissue was harvested for immunohistochemistry and RNA extraction. RESULTS: Five different joint sites were biopsied (knee, elbow, wrist, metacarpal phalangeal and proximal interphalangeal). No significant complications were reported following the procedure. No difference in pain, swelling and stiffness of the biopsied joint from before and after the procedure was demonstrated. A median of 14 biopsy samples was retrieved from each procedure with 93% of biopsy procedures yielding good quality tissue. RNA yield was good in all joints and in repeat biopsies. Multivariant analysis demonstrated a significantly greater yield of RNA and graded tissue in relation to a high prebiopsy, grey-scale synovitis score (0-3, semiquantitative). CONCLUSIONS: A minimally invasive approach to synovial tissue harvesting, using US guidance, is both safe and well-tolerated by patients. Tissue quality/RNA yield is preserved in subsequent biopsies following therapeutic intervention. A high US grey-scale synovitis score is a predictor of good quality/quantity of tissue and RNA.

Statins, the widely used inhibitors of cholesterol biosynthesis, also have immunomodulatory properties. Statins have recently been shown to have beneficial prophylactic and therapeutic effects in actively induced, short-term animal models of the autoimmune diseases multiple sclerosis and rheumatoid arthritis, leading to clinical trials. We therefore investigated whether statins’ protective effects could be reproduced in the nonobese diabetic (NOD) mouse, a spontaneous, chronic model of autoimmune diabetes. Mice were treated with 0, 1, 10, or 50 mg · kg−1 · day−1 oral atorvastatin from 6 or 12 weeks of age, without effect on the rate or prevalence of diabetes development, islet infiltration, or islet major histocompatibility complex class II expression. However, there was clear evidence of a disease-relevant immunological effect of statins in vivo, since short-term (12-day) treatment significantly reduced the number of proinflammatory (γ-interferon–producing) CD8 cells recognizing a dominant pathogenic epitope. This effect was absent in mice treated for longer periods, suggesting that atorvastatin loses efficiency in inhibiting autoantigen-specific T-cells over time. This observation may explain the discrepancy between the reported success of statins in acutely induced models and the lack of it in a chronic, spontaneous model of autoimmune disease and has implications for the adoption of such therapy in humans.

An increasing wealth of evidence suggests an important role for chemokines and their receptors in the pathogenesis of inflammation. In this review, the authors explore the role of chemokines in inflammatory joint diseases, with particular emphasis on rheumatoid arthritis. Recent progress aimed at modulating the chemokine and chemokine receptor system for therapy will also be discussed.

Biological regeneration is proving to be an increasingly attractive alternative/complement to prosthetic replacement of tissues and organs. In cell-based therapeutic approaches, cells are manipulated in vitro and administered to patients as living and dynamic biological agents. In this review, we have focused on the regeneration of the injured joint surface to discuss novel issues that these new therapeutic agents raise and are difficult to address within the paradigms of traditional pharmacology. They include: determination of the mechanism of action and dose, evaluation of potency, safety and toxicity, as well as upscale, delivery and identification of proper indications. Finally, novel potential approaches are proposed in which resident progenitor cells are targeted to regenerate the damaged tissue.

Lactate has long been considered a “waste” by-product of cell metabolism, and it accumulates at sites of inflammation. Recent findings have identified lactate as an active metabolite in cell signalling, although its effects on immune cells during inflammation are largely unexplored. Here we ask whether lactate is responsible for T cells remaining entrapped in inflammatory sites, where they perpetuate the chronic inflammatory process. We show that lactate accumulates in the synovia of rheumatoid arthritis patients. Extracellular sodium lactate and lactic acid inhibit the motility of CD4+ and CD8+ T cells, respectively. This selective control of T cell motility is mediated via subtype-specific transporters (Slc5a12 and Slc16a1) that we find selectively expressed by CD4+ and CD8+ subsets, respectively. We further show both in vitro and in vivo that the sodium lactate-mediated inhibition of CD4+ T cell motility is due to an interference with glycolysis activated upon engagement of the chemokine receptor CXCR3 with the chemokine CXCL10. In contrast, we find the lactic acid effect on CD8+ T cell motility to be independent of glycolysis control. In CD4+ T helper cells, sodium lactate also induces a switch towards the Th17 subset that produces large amounts of the proinflammatory cytokine IL-17, whereas in CD8+ T cells, lactic acid causes the loss of their cytolytic function. We further show that the expression of lactate transporters correlates with the clinical T cell score in the synovia of rheumatoid arthritis patients. Finally, pharmacological or antibody-mediated blockade of subtype-specific lactate transporters on T cells results in their release from the inflammatory site in an in vivo model of peritonitis. By establishing a novel role of lactate in control of proinflammatory T cell motility and effector functions, our findings provide a potential molecular mechanism for T cell entrapment and functional changes in inflammatory sites that drive chronic inflammation and offer targeted therapeutic interventions for the treatment of chronic inflammatory disorders., High levels of lactate that accumulate in chronic inflammatory sites can trigger unfavorable responses in infiltrating T cells; reducing T cells' sensitivity to lactate might offer therapeutic solutions to chronic inflammatory disorders., Author Summary Acidity is a feature of inflammatory sites such as arthritic synovia, atherosclerotic plaques, and tumor microenvironments and results in part from the accumulation of lactate as a product of glycolysis under hypoxic conditions. Recently it has emerged that lactate may be more than just a bystander and might act to modulate the immune-inflammatory response. Here we report just such activity: lactate inhibits T cell motility by interfering with glycolysis that is required for T cells to migrate, it causes T cells to produce higher amounts of the proinflammatory cytokine IL-17, and it triggers loss of cytolytic activity. These phenomena are hallmark features of T cells in chronic inflammatory infiltrates. The functional changes depend on the expression of specific lactate transporters by different subsets of T cells, namely the sodium lactate transporter Slc5a12 in CD4+ T cells and the lactic acid transporter Slc16a1 in CD8+ T cells. We propose that T cells entering inflammatory sites sense high concentrations of lactate via their specific transporters. Loss of motility leads to their entrapment at the site, where through their increased production of inflammatory cytokines yet decreased cytolytic capacity, they add detrimentally to chronic inflammation. Targeting lactate transporters and/or metabolic pathways on T cells could deliver novel, invaluable therapeutics for the treatment of widespread chronic inflammatory disorders.

The observation that circulating leucocytes adhere to and migrate across the vascular endothelium was first made 70 yr ago; this was noted to occur without breach of the endothelial barrier, suggesting the presence of complex regulatory mechanisms [1]. More recently, in a series of classic experiments, Gowans and Knight observed that lymphocytes isolated from the rat thoracic duct homed rapidly back to lymph nodes and secondary lymphoid organs upon reinjection: furthermore, it was noted that this occurred across the distinctly shaped endothelial cells of the postcapillary venules [2]. Since then we have learnt much about the molecular basis of leucocyte extravasation and the regulatory mechanisms involved. In this review we will describe molecular interactions involved in the stages of leucocyte recruitment and extravasation into the tissues. We will also describe the specific molecular interactions that allow the selective recruitment of tissue-specific leucocytes to inflammatory sites. Finally, we will emphasize the central role that adhesion molecules have in the development of the inflammatory response by drawing from examples of human disease, and describe recent progress in the therapeutic targeting of these molecules with particular reference to inflammatory arthritis.

Rheumatoid arthritis is a serious, inflammatory disease of the distal joints that has a possible neurogenic component underlying its pathology. Substance P (SP), an endogenous neuropeptide that acts upon the neurokinin 1 (NK1) receptor, is released from sensory nerves and is involved in neurogenic inflammation. In this study, we have developed novel techniques to determine the contribution of SP to microvascular responses in a model of complete Freund's adjuvant (CFA)-induced arthritis in NK1 knockout mice. Detailed analysis in normal mice revealed that CFA (20 μg i.art.)-induced plasma extravasation was raised from 18 to 72 h, when compared with intravascular volume. By comparison, knee swelling was sustained for 3 weeks. Neutrophil accumulation mirrored plasma extravasation. SP (10 pmol i.art.) caused significant acute plasma extravasation, but not other parameters, in wild type (WT), but not NK1 knockout mice. CFA (10 μg i.art.) induced a significantly decreased intravascular volume, presumably due to decreased blood flow, at early time points (5 and 7 h) in WT but not NK1 knockouts. Otherwise, similar responses in WT and NK1 knockout mice were observed. However, injection of SP into CFA-pretreated joints caused a significant enhancement of plasma extravasation and knee swelling in the WT but not NK1 knockouts. In conclusion, the present study has used novel techniques in WT and NK1 knockout mice to show that SP can modulate vascular tone and permeability in the inflamed joint via activation of the NK1 receptor and that SP-induced responses are more pronounced where pre-existing inflammation is present. Keywords: Substance P, rheumatoid arthritis, neurokinin 1 receptor, plasma extravasation, intravascular volume, neutrophil accumulation, knee swelling Introduction Rheumatoid arthritis in humans is a chronic, debilitating, inflammatory disease that affects connective tissue in distal joints and is characterized by spontaneous remissions and unpredictable exacerbations of the condition (Ignatavicius, 2001). Inflammatory processes involved in joint disease include plasma extravasation leading to joint swelling, vascular remodeling and cellular infiltration of the synovia. The precise microvascular mechanisms underlying these events are not fully understood, but it is possible that a neurogenic component is involved in joint disease. For example, in experimental models of joint disease, transection of sensory nerves has been shown to reduce hyperalgesia, swelling and joint destruction (Levine et al., 1986). Furthermore, there is a strong tendency for symmetrical joint inflammation in patients with rheumatoid arthritis suggesting a possible neural influence on the progression of the disease (Niissalo et al., 2002). Indeed, a neurogenic influence of contralateral responses has been demonstrated in a rat model of joint disease (Kidd et al., 1995). Neurogenic inflammation is defined as the oedema formation, increased blood flow and inflammatory cell involvement observed after stimulation of sensory nerve fibres (usually C and Aδ fibres) and release of neuropeptides, such as substance P (SP), calcitonin gene-related peptide and neuropeptide Y. SP, acting on the neurokinin 1 (NK1) receptor, exerts a variety of proinflammatory effects. For example, SP is a potent mediator of increased microvascular permeability in species that include the mouse through its action on postcapillary endothelial cells (Cao et al., 1999) and SP has a potent effect on the cellular components of inflammation, such as neutrophil accumulation (Cao et al., 2000). The involvement of SP in joint inflammation has been implicated in arthritis, both in human and experimental animal studies. In human rheumatoid synovia, a strong hybridization signal of the NK1 receptor has been detected and, moreover, the signal intensity of NK1 receptor mRNA positively correlated with the severity of joint disease (Sakai et al., 1998). In animal studies, antigen-induced mono-arthritis leads to a pronounced bilateral upregulation of expression of NK1 receptors in the rat dorsal root ganglion (Segond von Banchet et al., 2000). Furthermore, adjuvant-induced joint inflammation has been shown to cause a very rapid transcription of the SP precursor, β-preprotachykinin, in the innervating dorsal root ganglia of the rat (Bulling et al., 2001). The availability of NK1 receptor knockout mice now enables the investigation of neurogenic mechanisms in arthritis in this species. However, to date, published methods for investigating joint disease in mice do not permit a detailed analysis of the early stages of microvascular responses in which neuropeptides are known to have their most potent effects. With this in mind, we have developed techniques whereby both the early and late microvascular responses in the mouse knee joint can be determined. In particular, a quantitative radiometric assay for measuring plasma extravasation or intravascular volume has been developed and used in conjunction with a traditional technique for measuring knee swelling. Furthermore, a method has been developed for collecting a synovial lavage from mouse knee joints. To our knowledge, this is the first time that a technique that permits the analysis of the cellular and soluble contents of mouse joint synovial fluid has been published. Using the developed techniques, we have elucidated the time course of microvascular responses to intra-articular (i.art.) injection of complete Freund's adjuvant (CFA), determined the relationship between plasma extravasation and knee swelling and investigated the contribution of SP to joint inflammation.

Objective To evaluate the presence and immunohistochemical characteristics of subchondral bone marrow inflammatory infiltrate in rheumatoid arthritis (RA) and to determine the in situ relationship between marrow inflammation and osteoclast recruitment. Methods Bone samples and paired synovia from 8 RA patients undergoing joint surgery were analyzed by immunohistochemistry and in situ hybridization for specific lymphoid neogenetic features, such as T and B cell composition, follicular dendritic cell (FDC) networks, peripheral lymph node addressin (PNAd)–positive high endothelial venules, and lymphoid chemokine expression. Osteoclasts were identified as multinucleated tartrate-resistant acid phosphatase (TRAP)–positive and cathepsin K–positive cells adherent to the bone surface. Results An inflammatory infiltrate with perivascular aggregates of variable size was detected in 7 (87.5%) of 8 synovial samples and in paired bone samples. Lymphoid neogenetic features typical of rheumatoid synovium were also recognized in the bone marrow. PNAd+ blood vessels were found in 4 of 8 patients, CD21+ FDC networks in 2 patients, CXCL13+ cells in 5 patients, and CCL21+ cells in 6 patients. TRAP-positive and cathepsin K–positive osteoclasts were identified on both the synovial and marrow sides of the bone surface. Bone marrow samples showing a higher degree of inflammation were characterized by a significantly increased number of osteoclasts adherent to the subchondral bone. Conclusion Our data demonstrate that lymphoid aggregates with lymphoid neogenetic features are detectable on the subchondral side of the joint in established RA. Moreover, the local inflammation/aggregation process appears to be related to osteoclast differentiation on the marrow side of subchondral bone, supporting a functional role of the bone compartment in local damage.