Immunization of rats with homologous type XI collagen leads to chronic and relapsing arthritis with different genetics and joint pathology than arthritis induced with homologous type II collagen

The peculiar features, diversity and impact of citrulline-reactive autoantibodies

Since entering the stage 25 years ago as a highly specific serological biomarker for rheumatoid arthritis, anti-citrullinated protein antibodies (ACPAs) have been a topic of extensive research. This hallmark B cell response arises years before disease onset, displays interpatient autoantigen variability, and is associated with poor clinical outcomes. Technological and scientific advances have revealed broad clonal diversity and intriguing features including high levels of somatic hypermutation, variable-domain N-linked glycosylation, hapten-like peptide interactions, and clone-specific multireactivity to citrullinated, carbamylated and acetylated epitopes. ACPAs have been found in different isotypes and subclasses, in both circulation and tissue, and are secreted by both plasmablasts and long-lived plasma cells. Notably, although some disease-promoting features have been reported, results now demonstrate that certain monoclonal ACPAs therapeutically block arthritis and inflammation in mouse models. A wealth of functional studies using patient-derived polyclonal and monoclonal antibodies have provided evidence for pathogenic and protective effects of ACPAs in the context of arthritis. To understand the roles of ACPAs, one needs to consider their immunological properties by incorporating different facets such as rheumatoid arthritis B cell biology, environmental triggers and chronic antigen exposure. The emerging picture points to a complex role of citrulline-reactive autoantibodies, in which the diversity and dynamics of antibody clones could determine clinical progression and manifestations.

Endophilin A2 deficiency protects rodents from autoimmune arthritis by modulating T cell activation

The introduction of the CTLA-4 recombinant fusion protein has demonstrated therapeutic effects by selectively modulating T-cell activation in rheumatoid arthritis. Here we show, using a forward genetic approach, that a mutation in the SH3gl1 gene encoding the endocytic protein Endophilin A2 is associated with the development of arthritis in rodents. Defective expression of SH3gl1 affects T cell effector functions and alters the activation threshold of autoreactive T cells, thereby leading to complete protection from chronic autoimmune inflammatory disease in both mice and rats. We further show that SH3GL1 regulates human T cell signaling and T cell receptor internalization, and its expression is upregulated in rheumatoid arthritis patients. Collectively our data identify SH3GL1 as a key regulator of T cell activation, and as a potential target for treatment of autoimmune diseases.

The autoimmune disorder, rheumatoid arthritis (RA), has been associated with multiple pathophysiological factors. Here the authors show that deficiency in endophilin A2 in rodents protects them from experimental arthritis by altering T cell activation threshold and effector functions, thereby hinting a potential target for RA therapy.

Crocin exerts anti-inflammatory and anti-arthritic effects on type II collagen-induced arthritis in rats

CONTEXT

Rheumatoid arthritis (RA) is a common systemic auto-immune disease, which is characterized by chronic and symmetry synovial inflammation. Crocin has been reported to exhibit anti-inflammatory effects in animal models.

OBJECTIVE

This study investigates the anti-inflammatory and anti-arthritic effects of crocin on type II collagen-induced arthritis (CIA) in Wistar rats.

MATERIALS AND METHODS

The CIA rat model was established and randomly divided into five groups with or without crocin treatment (10, 20 or 40 mg/kg), which was started on day 21 after arthritis induction and persisted for 36 days. The symptoms and molecular mechanisms of CIA and crocin-treated CIA rats were compared and investigated.

RESULTS

CIA rats presented severe RA symptoms, including high arthritis score, paw swelling, joint inflammation, bone erosion, chondrocyte death, cartilage destruction, enhanced expressions of matrix metalloproteinase (MMP) and pro-inflammatory cytokines. However, crocin could mitigate these symptoms. Crocin (40 mg/kg) exhibited the most efficient therapeutic function on CIA rats: the histological scores of joint inflammation, bone erosion, chondrocyte death, cartilage surface erosion, and bone erosion of CIA rats receiving 40 mg/kg crocin treatment were comparable to the normal rats. MMP-1, -3 and -13 protein expression levels of CIA rats with 40 mg/kg crocin treatment were decreased to levels similar to normal rats. Moreover, crocin could also inhibit the expression of TNF-α, IL-17, IL-6 and CXCL8 in serum and ankle tissues of CIA rats.

CONCLUSIONS

In summary, crocin exhibits therapeutic potential for RA, by mitigating the symptoms and inhibiting the pro-inflammatory factor expression.

A Shared Epitope of Collagen Type XI and Type II Is Recognized by Pathogenic Antibodies in Mice and Humans with Arthritis

Background

Collagen XI (CXI) is a heterotrimeric molecule with triple helical structure in which the α3(XI) chain is identical to the α1(II) chain of collagen II (CII), but with extensive posttranslational modifications. CXI molecules are intermingled in the cartilage collagen fibers, which are mainly composed of CII. One of the alpha chains in CXI is shared with CII and contains the immunodominant T cell epitope, but it is unclear whether there are shared B cell epitopes as the antibodies tend to recognize the triple helical structures.

Methods

Mice expressing the susceptible immune response gene Aq were immunized with CII or CXI. Serum antibody responses were measured, monoclonal antibodies were isolated and analyzed for specificity to CII, CXI, and triple helical collagen peptides using bead-based multiplex immunoassays, enzyme-linked immunosorbent assays, and Western blots. Arthritogenicity of the antibodies was investigated by passive transfer experiments.

Results

Immunization with CII or CXI leads to a strong T and B cell response, including a cross-reactive response to both collagen types. Immunization with CII leads to severe arthritis in mice, with a response toward CXI at the chronic stage, whereas CXI immunization induces very mild arthritis only. A series of monoclonal antibodies to CXI were isolated and of these, the L10D9 antibody bound to both CXI and CII equally strong, with a specific binding for the D3 epitope region of α3(XI) or α1(II) chain. The L10D9 antibody binds cartilage in vivo and induced severe arthritis. In contrast, the L5F3 antibody only showed weak binding and L7D8 antibody has no binding to cartilage and did not induce arthritis. The arthritogenic L10D9 antibody bound to an epitope shared with CII, the triple helical D3 epitope. Antibody levels to the shared D3 epitope were elevated in the sera from mice with arthritis as well as in rheumatoid arthritis.

Conclusion

CXI is immunologically not exposed in healthy cartilage but contains T and B cell epitopes cross-reactive with CII, which could be activated in both mouse and human arthritis and could evoke an arthritogenic response.

In Vivo Models for Inflammatory Arthritis

In vivo mouse models of inflammatory arthritis are extensively used to investigate pathogenic mechanisms governing inflammation-driven joint damage. Two commonly utilized models include collagen-induced arthritis (CIA) and methylated bovine serum albumin (mBSA) antigen-induced arthritis (AIA). These offer unique advantages for modeling different aspects of human disease. CIA involves breach of immunological tolerance resulting in systemic autoantibody-driven arthritis, while AIA results in local resolving inflammatory flares and articular T cell-mediated damage. Despite limitations that apply to all animal models of human disease, CIA and AIA have been instrumental in identifying pathogenic mediators, immune cell subsets and stromal cell responses that determine disease onset, progression, and severity. Moreover, these models have enabled investigation of disease phases not easily studied in patients and have served as testing beds for novel biological therapies, including cytokine blockers and small molecule inhibitors of intracellular signaling that have revolutionized rheumatoid arthritis treatment.

Rheumatoid arthritis: identifying and characterising polymorphisms using rat models

Rheumatoid arthritis is a chronic inflammatory joint disorder characterised by erosive inflammation of the articular cartilage and by destruction of the synovial joints. It is regulated by both genetic and environmental factors, and, currently, there is no preventative treatment or cure for this disease. Genome-wide association studies have identified ∼100 new loci associated with rheumatoid arthritis, in addition to the already known locus within the major histocompatibility complex II region. However, together, these loci account for only a modest fraction of the genetic variance associated with this disease and very little is known about the pathogenic roles of most of the risk loci identified. Here, we discuss how rat models of rheumatoid arthritis are being used to detect quantitative trait loci that regulate different arthritic traits by genetic linkage analysis and to positionally clone the underlying causative genes using congenic strains. By isolating specific loci on a fixed genetic background, congenic strains overcome the challenges of genetic heterogeneity and environmental interactions associated with human studies. Most importantly, congenic strains allow functional experimental studies be performed to investigate the pathological consequences of natural genetic polymorphisms, as illustrated by the discovery of several major disease genes that contribute to arthritis in rats. We discuss how these advances have provided new biological insights into arthritis in humans.

Influence of hydrocarbon oil structure on adjuvanticity and autoimmunity

Mineral oils are extensively used in our daily life, in food, cosmetics, biomedicine, vaccines and in different industrial applications. However, exposure to these mineral oils has been associated with immune adjuvant effects and the development of autoimmune diseases. Here we investigate the structural impacts of the hydrocarbon oil molecules on their adjuvanticity and autoimmunity. First, we showed that hydrocarbon oil molecules with small atomic differences could result in experimental arthritis in DA rats differing in disease severity, incidence, weight change and serum levels of acute phase proteins. Injection of these hydrocarbon oils resulted in the activation, proliferation and elevated expression of Th1 and especially Th17 cytokines by the T cells, which correlate with the arthritogenicity of the T cells. Furthermore, the more arthritogenic hydrocarbon oils resulted in an increased production of autoantibodies against cartilage joint specific, triple-helical type II collagen epitopes. When injected together with ovalbumin, the more arthritogenic hydrocarbon oils resulted in an increased production of αβ T cell-dependent anti-ovalbumin antibodies. This study shows the arthritogenicity of hydrocarbon oils is associated with their adjuvant properties with implications to not only arthritis research but also other diseases and medical applications such as vaccines in which oil adjuvants are involved.

The minor collagens in articular cartilage

Articular cartilage is a connective tissue consisting of a specialized extracellular matrix (ECM) that dominates the bulk of its wet and dry weight. Type II collagen and aggrecan are the main ECM proteins in cartilage. However, little attention has been paid to less abundant molecular components, especially minor collagens, including type IV, VI, IX, X, XI, XII, XIII, and XIV, etc. Although accounting for only a small fraction of the mature matrix, these minor collagens not only play essential structural roles in the mechanical properties, organization, and shape of articular cartilage, but also fulfil specific biological functions. Genetic studies of these minor collagens have revealed that they are associated with multiple connective tissue diseases, especially degenerative joint disease. The progressive destruction of cartilage involves the degradation of matrix constituents including these minor collagens. The generation and release of fragmented molecules could generate novel biochemical markers with the capacity to monitor disease progression, facilitate drug development and add to the existing toolbox for in vitro studies, preclinical research and clinical trials.

VAV1 regulates experimental autoimmune arthritis and is associated with anti-CCP negative rheumatoid arthritis

Rheumatoid arthritis (RA) patients can be stratified into two subgroups defined by the presence or absence of antibodies against citrullinated circular peptides (anti-CCP) with most of the genetic association found in anti-CCP positive RA. Here we addressed the role of VAV1, previously associated to multiple sclerosis (MS), in the pathogenesis of RA in experimental models and in a genetic association study. Experimental arthritis triggered by pristane or collagen type II was induced in DA rats and in the DA.BN-R25 congenic line that carries a polymorphism in Vav1. Difference in arthritis severity was observed only after immunization with pristane. In a case-control study, 34 SNPs from VAV1 locus were analyzed by Immunochip genotyping in 11475 RA patients (7573 anti-CCP positive and 3902 negative) and 15,870 controls in six cohorts of European Caucasians. A combination of the previous MS-associated haplotype and two additional SNPs was associated with anti-CCP negative RA (alleles G-G-A-A of rs682626-rs2546133-rs2617822-rs12979659, OR=1.13, P=1.27 × 10^-5). The same markers also contributed to activity of RA at baseline with the strongest association in the anti-CCP negative group for the rs682626-rs12979659 G-A haplotype (β=-0.283, P=0.0048). Our study suggests a role for VAV1 and T-cell signaling in the pathology of anti-CCP-negative RA.

C57BL/6 mice need MHC class II Aq to develop collagen-induced arthritis dependent on autoreactive T cells

INTRODUCTION

Collagen-induced arthritis (CIA) has traditionally been performed in MHC class II A(q)-expressing mice, whereas most genetically modified mice are on the C57BL/6 background (expressing the b haplotype of the major histocompatibility complex (MHC) class II region). However, C57BL/6 mice develop arthritis after immunisation with chicken-derived collagen type II (CII), but arthritis susceptibility has been variable, and the immune specificity has not been clarified.

OBJECTIVE

To establish a CIA model on the C57BL/6 background with a more predictable and defined immune response to CII.

RESULTS

Both chicken and rat CII were arthritogenic in C57BL/6 mice provided they were introduced with high doses of Mycobacterium tuberculosis adjuvant. However, contaminating pepsin was strongly immunogenic and was essential for arthritis development. H-2(b)-restricted T cell epitopes on chicken or rat CII could not be identified, but expression of A(q) on the C57BL/6 background induced T cell response to the CII260-270 epitope, and also prolonged the arthritis to be more chronic.

CONCLUSIONS

The putative (auto)antigen and its arthritogenic determinants in C57BL/6 mice remains undisclosed, questioning the value of the model for addressing T cell-driven pathological pathways in arthritis. To circumvent this impediment, we recommend MHC class II congenic C57BL/6N.Q mice, expressing A(q), with which T cell determinants have been thoroughly characterised.

MicroRNA-337 is associated with chondrogenesis through regulating TGFBR2 expression

OBJECTIVE

MicroRNAs (miRNAs) have been implicated in regulating diverse cellular pathways and involved in development and inflammation. This study aimed to examine six miRNAs expression during the cartilage development and identify the key miRNA which is associated with chondrogenesis.

METHODS

The expression of six miRNAs in cartilage tissue during development was screened by real-time quantitative polymerase chain reaction (RT-qPCR). Rat models of bone matrix gelatin induced endochondral ossification, collagen-induced arthritis and pristane-induced arthritis were established to examine whether miR-337 is involved in chondrogenesis. Furthermore, the regulation of transforming growth factor-b type II receptor (TGFBR2) expression by miR-337 was determined with the luciferase reporter gene assay and Western blot. The expression of some specific genes relevant to cartilage tissue was tested by RT-qPCR after miR-337 mimic or inhibitor transfection.

RESULTS

MiR-337 expression was significantly down-regulated and almost disappeared in the maturation phases of endochondral ossification. The results of histology and RT-qPCR from three rat models showed that miR-337 is directly bound up with chondrogenesis. Furthermore, the results from the luciferase reporter gene assay and Western blot indicated that miR-337 regulated TGFBR2 expression. Our study also found that the enhancement of miR-337 may modulate the expression of cartilage-specific genes such as AGC1 in C-28/I2 chondrocytes.

CONCLUSION

We proved that miRNA-337 is associated with chondrogenesis through regulating TGFBR2 expression, and miRNA-337 can also influence cartilage-specific gene expression in chondrocytes. These findings may provide an important clue for further research in the arthritis pathogenesis and suggest a new remedy for arthritis treatment.

Treatment with total alkaloids from Radix Linderae reduces inflammation and joint destruction in type II collagen-induced model for rheumatoid arthritis

Radix Linderae, the dry roots of Lindera aggregata (Sims) Kosterm., is frequently used in traditional Chinese medicine. It contains alkaloids, volatile oils and sesquiterpene esters. In the present study, we investigated the therapeutic potential and underlying mechanisms of the total alkaloids from Radix Linderae (TARL) on collagen II (CII)-induced arthritis (CIA) in mice. TARL (50, 100 and 200mg/kg), orally administered on the same day of an antigen challenge for 20 consecutive days, alleviated disease severity in a dose-dependent manner but did not significantly affect body weights. The TARL treatment reduced the serum level of anti-CII IgG and suppressed the delayed type hypersensitivity evaluated by its effect against CII-induced ear swelling. TARL also protected joint destruction based on the evidence of reducing the histopathological scores. Furthermore, TARL suppressed CII- and concanavalin A-stimulated lymphocyte proliferation in popliteal lymph nodes, where are close to the affected joints in CIA. These data suggest that TARL is a potential therapeutic agent for rheumatoid arthritis that suppresses inflammation and protects joints from destruction.

Anti-inflammatory effect of Ulmus davidiana Planch (Ulmaceae) on collagen-induced inflammation in rats

Ulmus davidiana Planch (Ulmaceae) extract (UD) has long been known to have anti-inflammatory and anticancer activities. UD has been also known to have protective effects on damaged tissue, inflammation and bone among other functions. Effects of UD on inflammatory and immune responses and its mechanisms in collagen-induced inflammation (CII) rat were studied. Hind paw volumes of rats were measured by volume meter; lymphocyte proliferation, interleukin (IL)-1, IL-2, tumor necrosis factor (TNF)-α level was determined by 3-(4,5-2dimethylthiazal-2yl)2,5-diphenyltetrazoliumbromide assay. Antibodies to collagen type II (BC-II) were determined by enzyme-linked immunosorbent assay. There was a marked secondary inflammatory response in CII model, which accompanied with the decrease of body weight and the weight of immune organs simultaneously. The administration of UD (20, 80, 150mg/kg, intragastrically×10 days) inhibited the inflammatory response and restored body weight and the weight of immune organs of CII rats. Lymphocyte proliferation and IL-2 production of CII rats increases, together with IL-1 and TNF-α in peritoneal macrophages and synoviocytes. The administration of UD (20, 80, 150mg/kg, 10 days) reduced above changes significantly. UD had no effect on the concentration of antibodies to BC-II. From the results, it was concluded that UD possesses anti-inflammatory and immunoregulatory activities and has a therapeutic effect on CII rats.

Experimental spondyloarthropathies: Animal models of ankylosing spondylitis

Spondyloarthropathies (SpAs), including ankylosing spondylitis, are chronic inflammatory diseases of the axial skeleton. Genomic scans of SpA families revealed the overwhelming complexity of the disease, which appears to be under the control of over 20 chromosome loci, including the major SpA gene HLA-B27 within class I of the major histocompatibility complex (MHC). Animal models confirmed the primary role of MHC in SpA susceptibility and supported the hypothesis that certain enterobacterial infections can trigger SpA. Immunization of mice with proteoglycan aggrecan also can provoke SpA, thus providing the opportunity to study genetic and clinical details of the disease initiation.

Can unresolved infection precipitate autoimmune disease?

Autoimmune diseases are frequently postulated to arise as post-infectious phenomena. Here we survey the evidence supporting these theories, with particular emphasis on Crohn's disease and ankylosing spondylitis. Direct proof that infection establishes persistent autoimmunity remains lacking, although it may provoke a prolonged inflammatory response when occurring on a susceptible immunological background. The argument of infective causality is by no means trivial, since it carries important consequences for the safety of vaccine development.

Positional cloning of Ncf1--a piece in the puzzle of arthritis genetics

Positional cloning of susceptibility genes in complex diseases like rheumatoid arthritis in humans is hampered by aspects like genetic heterogeneity and environmental variations, while genetic studies in animal models contain several advantages. With animal models, the environment can be controlled, the genetic complexity of the disease is minimized and the disease onset can be predicted, which simplify diagnosis and characterization. We use pristane-induced arthritis in rats to investigate the inheritance of arthritis. Until now, we have identified 15 loci that significantly predispose rats to the development of arthritis. One of these arthritis loci has been isolated and confirmed to be caused by a polymorphism in the Ncf1 gene. In this review, we outline the methods used to identify Ncf1 as one single susceptibility gene in a complex puzzle of inherited factors that render susceptibility to a complex autoimmune disorder like arthritis.

Effects and mechanisms of glucosides of chaenomeles speciosa on collagen-induced arthritis in rats

Effects of glucosides of chaenomeles speciosa (GCS)-a Chinese traditional herbal medicine (CTM) on inflammatory and immune responses and its mechanisms in collagen-induced arthritis (CIA) rat were studied. Hind paw volumes of rats were measured by volume meter; lymphocyte proliferation, interleukin-1, interleukin-2, TNF-alpha level was determined by 3-(4,5-2 dimethylthiazal-2yl)2,5-diphenyltetrazoliumbromide (MTT) assay; cAMP level in synoviocytes was analyzed by competitive protein binding assay (CPBA). mRNA expression of G(i,), G(s), and TNF-alpha of synoviocytes in CIA rats was measured by RT-PCR and antibodies to collagen type II (CII) were determined by enzyme-linked immunosorbent assay (ELISA), respectively. There was a marked secondary inflammatory response in CIA model, which accompanied with the decrease of body weight and the weight of immune organs simultaneously. The administration of GCS (30, 60, 120 mg x kg(-1), ig x 7 days) inhibited the inflammatory response and restored body weight and the weight of immune organs of CIA rats. Lymphocyte proliferation and IL-2 production of CIA rats increases, together with IL-1 and TNF-alpha in peritoneal macrophages and synoviocytes. The administration of GCS (30, 60, 120 mg x kg(-1), ig x 7 days) reduced above changes significantly. GCS at the concentration of 0.5, 2.5, 12.5, 62.5, 125 mg x l(-1) increased cAMP level of synoviocytes, which decreased in CIA rats in vitro. At the same time, GCS inhibited mRNA expression of G(i,) and TNF-alpha of synoviocytes and increased mRNA expression of G(s) of synoviocytes in CIA rats. GCS had no effect on the concentration of antibodies to CII. GCS possesses anti-inflammatory and immunoregulatory actions and has a therapeutic effect on CIA rats due to G protein-AC-cAMP transmembrane signal transduction of synoviocytes, which play a crucial role in pathogenesis of this disease.

Both common and unique susceptibility genes in different rat strains with pristane-induced arthritis

Pristane-induced arthritis (PIA) in rats is an animal model for rheumatoid arthritis (RA). We have previously identified seven quantitative trait loci (QTLs), which regulate arthritis development using a cross between the susceptible DA strain and the resistant E3 strain of rats (Pia2-8). In the present study the inbred rat strain LEW.1F was used as the susceptible strain in a cross with the E3 strain. The results confirmed the locus Pia4 on chromosome 12, which previously was shown to be associated with PIA, and also with experimental allergic encephalomyelitis, in crosses between the rat strains E3 and DA. On chromosome 1, linked to the albino locus, we identified a novel QTL, Pia9 in the LEW.F1 cross. This locus was associated with arthritis severity in the early phase of disease. A locus on chromosome 16, denoted Pia11, was also associated with arthritis severity in the early phase of the disease. A suggestive locus was detected on chromosome 14, which was associated with arthritis severity at the time when PIA progresses into a chronic phase. Using a congenic LEW.1F strain, which carries E3 alleles at the Pia9 locus, we confirmed that the E3 allele significantly suppresses arthritis severity during the early phase of the disease. The results revealed synergistic effects between different susceptibility loci using ANOVA analysis. These interactions were influenced by gender. Rats with Pia9 alleles from LEW.1F and Pia11 alleles from E3, were shown to suffer from much more severe arthritis in the early stage of the disease. On the other hand, the Pia9 and the suggestive locus on chromosome 14 affected only males during the chronic phase of the disease. These findings provide clues to how genetic factors by themselves, and in interaction with each other, regulate the development of a disease, which displays many similarities to RA.