Genetic, hormonal and behavioural influence on spontaneously developing arthritis in normal mice

Intermittent administration of PTH for the treatment of inflammatory bone loss does not enhance entheseal pathological new bone formation

OBJECTIVE

To investigate the effect of intermittent parathyroid hormone (iPTH) administration on pathological new bone formation during treatment of ankylosing spondylitis-related osteoporosis.

METHODS

Animal models with pathological bone formation caused by hypothetical AS pathogenesis received treatment with iPTH. We determined the effects of iPTH on bone loss and the formation of pathological new bone with micro-computed tomography (micro-CT) and histological examination. In addition, the tamoxifen-inducible conditional knockout mice (CAGGCre-ERTM; PTHflox/flox, PTH-/-) was established to delete PTH and investigate the effect of endogenous PTH on pathological new bone formation.

RESULTS

iPTH treatment significantly improved trabecular bone mass in the modified collagen-induced arthritis (m-CIA) model and unbalanced mechanical loading models. Meanwhile, iPTH treatment did not enhance pathological new bone formation in all types of animal models. Endogenous PTH deficiency had no effects on pathological new bone formation in unbalanced mechanical loading models.

CONCLUSION

Experimental animal models of AS treated with iPTH show improvement in trabecular bone density, but not entheseal pathological bone formation，indicating it may be a potential treatment for inflammatory bone loss does in AS.

Sex differences in long-term effects of collagen-induced arthritis in middle-aged mice

Introduction: Rheumatoid arthritis (RA) is a chronic inflammatory disorder with high prevalence among middle-aged women. Collagen-induced arthritis (CIA) is the most widely used animal model of RA, however, sex differences and long-term effects of CIA in mice are poorly described in the literature. Aim: Therefore, the present study aimed to analyze the long-term effects of CIA on the joints of middle-aged mice of both sexes and to describe potential sex differences. Materials and methods: CIA was induced in middle-aged DBA/1J mice by immunization with bovine type II collagen and complete Freund's adjuvant. Saline was administered to control mice. Arthritis score assessment, plethysmometry, and thermal imaging of the joints were performed weekly for 15 weeks. Locomotor activity, micro-computed tomography, joint histology and biochemical analyses were performed at the end of the experiment. Results: Our results indicate a similar prevalence of arthritis in both sexes of mice-67% (8/12) of females and 89% (8/9) males with an earlier onset in males (day 14 vs. day 35). After the arthritis scores peaked on day 56 for males and day 63 for females, they steadily declined until the end of the experiment on day 105. A similar dynamics was observed in paw volume and temperature analyzing different aspects of joint inflammation. Long-term consequences including higher proteinuria (by 116%), loss of bone density (by 33.5%) and joint damage in terms of synovial hyperplasia as well as bone and cartilage erosions were more severe in CIA males compared to CIA females. There were no significant differences in locomotor activity between CIA mice and CTRL mice of any sex. Conclusion: This is the first study to describe the long-term effects of the CIA model in terms of sex differences in DBA/1J mice. Our results indicate sex differences in the dynamics, but not in the extent of arthritis. An earlier onset of arthritis and more severe consequences on joints, bones and kidneys were found in males. The underlying immune pathomechanisms responsible for the limited duration of the arthritis symptoms and the opposite sex difference in comparison to RA patients require further investigation.

CXCL12/CXCR4-Rac1-mediated migration of osteogenic precursor cells contributes to pathological new bone formation in ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory disease characterized by inflammatory back pain and spinal ankylosis due to pathological new bone formation. Here, we identified CXCL12 as a critical contributor to pathological new bone formation through recruitment of osteogenic precursor cells (OPCs). CXCL12 was found highly expressed in the regions that would potentially develop pathological new bone. OPCs were recruited to the regions where CXCL12 was up-regulated. Inhibition of CXCL12/CXCR4 axis with AMD3100 or conditional knockout of CXCR4 attenuated OPCs migration and subsequent pathological new bone formation in animal models of AS. By contrast, a genetically engineered animal model with CXCL12 overexpression developed a joint ankylosis phenotype. Furthermore, Rac1 was found essential for OPCs migration and pathological new bone formation. These findings ravel the novel role of CXCL12 in AS and indicate a potential strategy for targeting the CXCL12/CXCR4-Rac1 axis to prevent progression of axial skeleton ankylosis.

Inflammatory Foot Involvement in Spondyloarthritis: From Tarsitis to Ankylosing Tarsitis

Spondyloarthritis (SpA) is a group that includes a wide spectrum of clinically similar diseases manifested by oligoarticular arthritis and axial or peripheral ankylosis. Although axial SpA is predominant in Caucasians and adult-onset patients, juvenile-onset and Latin American patients are characterized by severe peripheral arthritis and particularly foot involvement. The peripheral involvement of SpA can vary from tarsal arthritis to the most severe form named ankylosing tarsitis (AT). Although the cause and etiopathogenesis of axSpA are often studied, the specific characteristics of pSpA are unknown. Several animal models of SpA develop initial tarsitis and foot ankylosis as the main signs, emphasizing the role of foot inflammation in the overall SpA spectrum. In this review, we attempt to highlight the clinical characteristics of foot involvement in SpA and update the knowledge regarding its pathogenesis, focusing on animal models and the role of mechanical forces in inflammation.

Lessons on SpA pathogenesis from animal models

Understanding the complex mechanisms underlying a disorder such as spondyloarthritis (SpA) may benefit from studying animal models. Several suitable models have been developed, in particular to investigate the role of genetic factors predisposing to SpA, including HLA-B27, ERAP1, and genes related to the interleukin (IL)-23/IL-17 axis. One of the best examples of such research is the HLA-B27 transgenic rat model that fostered the emergence of original theories regarding HLA-B27 pathogenicity, including dysregulation of innate immunity, contribution of the adaptive immune system to chronic inflammation, and influence of the microbiota on disease development. Very recently, a new model of HLA-B27 transgenic Drosophila helped to expand further some of those theories in an unexpected direction involving the TGFβ/BMP family of mediators. On the other hand, several spontaneous, inducible, and/or genetically modified mouse models-including SKG mouse, TNF^ΔARE mouse and IL-23-inducible mouse model of SpA-have highlighted the importance of TNFα and IL-23/IL-17 axis in the development of SpA manifestations. Altogether, those animal models afford not only to study disease mechanism but also to investigate putative therapeutic targets.

Aberrant upregulation of CaSR promotes pathological new bone formation in ankylosing spondylitis

Pathological new bone formation is a typical pathological feature in ankylosing spondylitis (AS), and the underlying molecular mechanism remains elusive. Previous studies have shown that the calcium‐sensing receptor (CaSR) is critical for osteogenic differentiation while also being highly involved in many inflammatory diseases. However, whether it plays a role in pathological new bone formation of AS has not been reported. Here, we report the first piece of evidence that expression of CaSR is aberrantly upregulated in entheseal tissues collected from AS patients and animal models with different hypothetical types of pathogenesis. Systemic inhibition of CaSR reduced the incidence of pathological new bone formation and the severity of the ankylosing phenotype in animal models. Activation of PLCγ signalling by CaSR promoted bone formation both in vitro and in vivo. In addition, various inflammatory cytokines induced upregulation of CaSR through NF‐κB/p65 and JAK/Stat3 pathways in osteoblasts. These novel findings suggest that inflammation‐induced aberrant upregulation of CaSR and activation of CaSR‐PLCγ signalling in osteoblasts act as mediators of inflammation, affecting pathological new bone formation in AS.

Arthritis sensory and motor scale: predicting functional deficits from the clinical score in collagen-induced arthritis

Background

In the collagen-induced arthritis (CIA) mouse model, inflammation readouts are usually quantified using operator-dependent clinical scoring systems, and no systematic relationship with functional deficits has been detected. In this study, we extensively quantified sensory and motor deficits in CIA mice during natural disease progression and therapeutic treatment. Then, we used these data to build a scale to predict functional deficits on the basis of the classical clinical score.

Methods

Using the CIA mouse model, we longitudinally screened multiple approaches to assess locomotion (open field test, Catwalk™), sensitivity (Von Frey, Hargreaves, static weight-bearing tests), and inflammation (skin temperature), and identified the most accurate tests to correlate sensory and motor deficits with disease severity, measured by clinical score. We then used these tests to characterize functional deficits in control (naïve and mice injected with complete Freund’s adjuvant) and CIA mice, either untreated or treated with methotrexate to prevent functional deficits. By mathematical approaches, we finally investigated the relationship between functional deficits and clinical score.

Results

We found that the functional disability scores obtained with the open field, Catwalk™, Hargreaves, and skin temperature tests significantly correlated with the clinical score in CIA mice, either untreated or treated with methotrexate. Mathematical correlation showed that motor deficits, robustly characterized by two different tests, were twice more responsive than thermal sensitivity deficits.

Conclusion

We propose the arthritis sensory and motor (ArthriSM) scale as a new theranostic tool to predict motor and sensory deficit based on the clinical score, in the experimental mouse model of CIA. This ArthriSM scale may facilitate the transfer of knowledge between preclinical and clinical studies.

The effect of anti-IL-6 receptor antibody for the treatment of McH-lpr/lpr-RA1 mice that spontaneously developed destructive arthritis and enthesitis

Background

McH-lpr/lpr-RA1 mice are a new strain of mice which spontaneously develop destructive arthritis and enthesitis in the ankle. There is no published data that drug treatment has been trialed on these mice. This study examined the effect of the mouse anti-IL-6 receptor antibody, MR16–1, for the treatment of arthritis and enthesitis in McH-lpr/lpr-RA1 mice.

Methods

Male McH-lpr/lpr-RA1 mice were randomly divided into control and treatment groups. MR16–1 was administered from 10 weeks of age for the treatment group. Saline was applied for the control group. The drug was administered once a week, at an initial dose of 2 mg, then maintained at 0.5 mg once per week thereafter. The effects were evaluated by the histopathological synovitis score, in vivo imaging using indocyanine green liposomes, and analysis of the gene expression of inflammatory cytokines.

Results

Tissue analyses were carried out at 14, 17 and 20 weeks of age. The synovitis scores of treated groups were significantly lower compared with those of the control group at 14 and 17 weeks of age. The kappa coefficient was 0.77. However, progression of entheseal ossification persisted in the MR16–1 treated group. In vivo imaging using indocyanine green liposomes showed significant decreases in signal intensities of treated groups at week 14, but no significant differences were observed at week 18. Blood serum amyloid A levels in treated groups were significantly lower at 17 weeks of age. The gene expression levels of Tnf and Il17 were also significantly lower in MR16–1 treated groups.

Conclusions

Administration of the anti-IL-6 receptor antibody is effective for the treatment of synovitis and bone destruction of McH-lpr/lpr-RA1 mice. McH-lpr/lpr-RA1 mice may be a suitable experimental model for the development of new treatments for destructive arthritis and enthesitis. IL-6 signal blockade could contribute to the treatment of destructive arthritis, and further studies should be carried out to confirm its potential in the prevention of enthesopathy developed to ossification.

Humanized Mouse Models of Rheumatoid Arthritis for Studies on Immunopathogenesis and Preclinical Testing of Cell-Based Therapies

Rodent models of rheumatoid arthritis (RA) have been used over decades to study the immunopathogenesis of the disease and to explore intervention strategies. Nevertheless, mouse models of RA reach their limit when it comes to testing of new therapeutic approaches such as cell-based therapies. Differences between the human and the murine immune system make it difficult to draw reliable conclusions about the success of immunotherapies. To overcome this issue, humanized mouse models have been established that mimic components of the human immune system in mice. Two main strategies have been pursued for humanization: the introduction of human transgenes such as human leukocyte antigen molecules or specific T cell receptors, and the generation of mouse/human chimera by transferring human cells or tissues into immunodeficient mice. Recently, both approaches have been combined to achieve more sophisticated humanized models of autoimmune diseases. This review discusses limitations of conventional mouse models of RA-like disease and provides a closer look into studies in humanized mice exploring their usefulness and necessity as preclinical models for testing of cell-based therapies in autoimmune diseases such as RA.

Conjugated Linoleic Acid Isomers Trans-10, Cis-12 and Cis-9, Trans-11 Prevent Collagen-Induced Arthritis in a Direct Comparison

Mixed-isomer conjugated linoleic acid (CLA) and the individual isomers, trans-10, cis-12 (CLAt10c12) and cis-9, trans-11 (CLAc9t11), decrease severity of collagen-induced arthritis (CA) when consumed after disease onset. Few studies have been conducted exploring the role of CLA in the prevention of autoimmune diseases. These studies suggest that isomer-specific effects may be occurring; however, a direct comparison of CLAt10c12 and CLAc9t11 has yet to be conducted. A study to compare the ability of CLAt10c12 and CLAc9t11 to prevent CA and assess their effects on early inflammation was performed. DBA/1 mice were fed a semipurified diet containing 6% corn oil (CO), 5.5% CO and 0.5% CLAt10c12, or 5.5% CO and 0.5% CLAc9t11 (n = 27 per diet) starting three weeks before CA primary immunization. Effects on disease incidence and severity, anticollagen antibodies, plasma and paw cytokines, and hepatic fatty acids were measured. Arthritis incidence was reduced by a minimum of 34% in mice fed either CLA isomer compared to those fed CO diet (p = 0.06). In mice that did develop arthritis (n = 9-12 mice per treatment), CLAt10c12 reduced arthritic severity to a greater extent than CLAc9t11 and CO (p = 0.03). CLA isomer treatment attenuated the increased hepatic arachidonic acid (ARA; 20:4n-6) observed with arthritis at one-week postonset (p = 0.03), while no differences in anticollagen antibodies or cytokines were observed between dietary treatments. These results suggest that CLA isomers may be effective at preventing specific immune-mediated inflammatory diseases, in part, through modulation of the ARA cascade.

Inflammation Intensity-Dependent Expression of Osteoinductive Wnt Proteins Is Critical for Ectopic New Bone Formation in Ankylosing Spondylitis

OBJECTIVE

To investigate the molecular mechanism underlying inflammation-related ectopic new bone formation in ankylosing spondylitis (AS).

METHODS

Spinal tissues and sera were collected from patients with AS and healthy volunteers and examined for the expression of Wnt proteins. An in vitro cell culture system mimicking the local inflammatory microenvironment of bone-forming sites was established to study the relationship between inflammation and Wnt expression, the regulatory mechanism of inflammation-induced Wnt expression, and the role of Wnt signaling in new bone formation. Modified collagen-induced arthritis (CIA) and proteoglycan-induced spondylitis (PGIS) animal models were used to confirm the key findings in vivo.

RESULTS

The levels of osteoinductive Wnt proteins were increased in sera and spinal ligament tissues from patients with AS. Constitutive low-intensity tumor necrosis factor (TNF) stimulation, but not short-term or high-intensity TNF stimulation, induced persistent expression of osteoinductive Wnt proteins and subsequent bone formation through NF-κB (p65) and JNK/activator protein 1 (c-Jun) signaling pathways. Furthermore, inhibition of either the Wnt/β-catenin or Wnt/protein kinase Cδ (PKCδ) pathway significantly suppressed new bone formation. The increased expression of Wnt proteins was confirmed in both the modified CIA and PGIS models. A kyphotic and ankylosing phenotype of the spine was seen during long-term observation in the modified CIA model. Inhibition of either the Wnt/β-catenin or Wnt/PKCδ signaling pathway significantly reduced the incidence and severity of this phenotype.

CONCLUSION

Inflammation intensity-dependent expression of osteoinductive Wnt proteins is a key link between inflammation and ectopic new bone formation in AS. Activation of both the canonical Wnt/β-catenin and noncanonical Wnt/PKCδ pathways is required for inflammation-induced new bone formation.

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.

Pain in rheumatoid arthritis: models and mechanisms

Pain is one of the most challenging symptoms for patients with rheumatoid arthritis (RA). RA-related pain is frequently considered to be solely a consequence of inflammation in the joints; however, recent studies show that multiple mechanisms are involved. Indeed, RA pain may start even before the disease manifests, and frequently does not correlate with the degree of inflammation or pharmacological management. In this aspect, animal studies have the potential to provide new insights into the pathology that initiate and maintain pain in RA. The focus of this review is to describe the most commonly used animal models for studies of RA pathology, which have also been utilized in pain research, and to summarize findings providing potential clues to the mechanisms involved in the regulation of RA-induced pain.

Methods for Testing Immunological Factors

Hypersensitivity reactions can be elicited by various factors: either immunologically induced, i.e., allergic reactions to natural or synthetic compounds mediated by IgE, or non-immunologically induced, i.e., activation of mediator release from cells through direct contact, without the induction of, or the mediation through immune responses. Mediators responsible for hypersensitivity reactions are released from mast cells. An important preformed mediator of allergic reactions found in these cells is histamine. Specific allergens or the calcium ionophore 48/80 induce release of histamine from mast cells. The histamine concentration can be determined with the o-phthalaldehyde reaction.

Experimental models of arthritis in which pathogenesis is dependent on TNF expression

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease characterized by joint damage as well as systemic manifestations. The exact cause of RA is not known. Both genetic and environmental factors are believed to contribute to the development of this disease. Increased expression of tumor necrosis factor (TNF) has been implicated in the pathogenesis of RA. Currently, the use of anti-TNF drugs is one of the most effective strategies for the treatment of RA, although therapeutic response is not observed in all patients. Furthermore, due to non-redundant protective functions of TNF, systemic anti-TNF therapy is often associated with unwanted side effects such as increased frequency of infectious diseases. Development of experimental models of arthritis in mice is necessary for studies on the mechanisms of pathogenesis of this disease and can be useful for comparative evaluation of various anti-TNF drugs. Here we provide an overview of the field and present our own data with two experimental models of autoimmune arthritis - collagen-induced arthritis and antibody-induced arthritis in C57Bl/6 and BALB/c mice, as well as in tnf-humanized mice generated on C57Bl/6 background. We show that TNF-deficient mice are resistant to the development of collagen-induced arthritis, and the use of anti-TNF therapy significantly reduces the disease symptoms. We also generated and evaluated a fluorescent detector of TNF overexpression in vivo. Overall, we have developed an experimental platform for studying the mechanisms of action of existing and newly developed anti-TNF drugs for the treatment of rheumatoid arthritis.

RANKL, OPG and CTR mRNA expression in the temporomandibular joint in rheumatoid arthritis

The calcitonin receptor (CTR) and receptor activator of nuclear factor κB ligand (RANKL) have been found to be involved in the differentiation of osteoclasts. The association between the RANKL:osteoprotegerin (OPG) expression ratio and the pathogenesis of bone-destructive rheumatoid arthritis (RA) has been described in several joints, but the available data for the temporomandibular joint (TMJ) are limited. The aim of the present study was to investigate the involvement of osteoclasts at sites of bone erosion by determining the CTR expression and the RANKL:OPG expression ratio in the TMJ in a collagen-induced arthritis (CIA) model. Forty-eight male Wistar rats were randomly divided into two groups: Control group, injected with saline solution for 6 weeks; and CIA group, injected with emulsion. The RANKL and OPG mRNA expression was significantly increased in immunized rats compared with that in non-immunized rats. The RANKL:OPG expression ratio on the trabecular bone surface was 9.0 and 6.4 in the CIA group at weeks 4 and 6, respectively, while the RANKL:OPG expression ratio in the controls was 1.0:2. CTR mRNA expression was significantly upregulated in immunized rats compared with that in non-immunized rats; the level of CTR mRNA in the CTR-positive osteoclasts on the trabecular bone surface was 10.9- and 7.8-fold higher in the CIA rats than that in the control rats at weeks 4 and 6, respectively. In conclusion, focal bone destruction in an experimental model of arthritis in the TMJ can be attributed to cells expressing CTR, a defining feature of osteoclasts. The expression of RANKL and OPG mRNA within the inflamed synovium provides an insight into the mechanism of osteoclast differentiation and function at the border of bone erosion in arthritis.

Reactive oxygen species in psoriasis and psoriasis arthritis: relevance to human disease

Psoriasis (Ps) is a chronic, immune-mediated, skin inflammatory disease affecting up to 3% of the population worldwide. Different environmental triggers initiate this complex multifactorial syndrome. Many individuals affected by Ps (6-26%) develop inflammatory disease in other organs, often in the joints as in psoriasis arthritis (PsA). Animal models that reflect the typical Ps syndrome, including both skin and joint pathology as in Ps and PsA, are valuable tools for dissecting disease pathways leading to clinical manifestations. In this context, we developed a new acute Ps and PsA-like disease model that appears after exposure to Saccharomyces cerevisiae mannan in certain mouse strains. The disease was found to be triggered by mannan-activated macrophages, leading to the activation of a pathogenic interleukin-17 pathway involving innate lymphocytes. Interestingly, the production of reactive oxygen species protected the mice from the triggering of this pathway and ameliorated Ps and PsA development.

Lipopolysaccharide treatment suppresses spontaneously developing ankylosing enthesopathy in B10.BR male mice: the potential role of interleukin-10

Background

Ankylosing enthesopathy (ANKENT) is an animal model of human ankylosing spondylitis. ANKENT is an inflammatory disease affecting the ankle and tarsal joints of the hind limbs in susceptible mouse strains. In the disease, the participation of intestinal microbiota components was suggested. Therefore, we attempted to increase the incidence of ANKENT by systemic administration of lipopolysaccharide (LPS), which is a component of bacterial cellular walls and stimulates inflammatory processes.

Methods

ANKENT occurrence, serum cytokine profiles, spleen cellular composition and in vitro cytokine response to LPS were analysed in LPS-treated and control LPS-untreated B10.BR male mice.

Results

Contrary to expectations, LPS treatment decreased the incidence of ANKENT in LPS-treated group compared to control LPS-untreated group. Flow cytometry analysis of splenocytes showed an increased percentage of macrophages, dendritic cells and neutrophils and a decreased percentage of B cells, T cells and T helper cells in LPS-treated males following LPS administration. In addition, LPS-treated males had significantly elevated IL-6 and IL-10 serum levels. At 20–22 weeks after the final LPS application, splenocytes from LPS-treated mice were more susceptible to in vitro LPS stimulation than those of the controls and produced significantly higher levels of TNFα and IL-6.

Conclusions

Repeated systemic stimulation with microbial component lipopolysaccharide in early adulthood significantly reduced the incidence of ANKENT in B10.BR mice and this finding can support the “hygiene hypothesis”. In LPS-treated mice, the innate immunity parameters and the level of anti-inflammatory IL-10 cytokine were significantly increased. Nevertheless, the immunological mechanism of the LPS protective effect remains unclear.

The need for littermate controls

The dramatic increase in the amount of research data being produced necessarily leads to higher demands on statistical thresholds and on experimental planning. This is to avoid positive selection of multiple tested data. Here we would like to highlight the need for including littermate controls in animal experiments, in particular when genetically modified strains are analysed for quantitative phenotypes. Thus, this suggestion will have impact on most immunological experiments performed today.

Decreased physical function and increased pain sensitivity in mice deficient for type IX collagen

OBJECTIVE

In mice with Col9a1 gene inactivation (Col9a1(-/-)), osteoarthritis (OA) and intervertebral disc degeneration develop prematurely. The aim of this study was to investigate Col9a1(-/-) mice for functional and symptomatic changes that may be associated with these pathologies.

METHODS

Col9a1(-/-) and wild-type mice were investigated for reflexes, functional impairment (beam walking, pole climbing, wire hang, grip strength), sensorimotor skills (rotarod), mechanical sensitivity (von Frey hair), and thermal sensitivity (hot plate/tail flick). Gait was also analyzed to determine velocity, stride frequency, symmetry, percentage stance time, stride length, and step width. Postmortem, sera obtained from the mice were analyzed for hyaluronan, and their knees and spines were graded histologically for degeneration.

RESULTS

Col9a1(-/-) mice had compensatory gait changes, increased mechanical sensitivity, and impaired physical ability. Col9a1(-/-) mice ambulated with gaits characterized by increased percentage stance times and shorter stride lengths. These mice also had heightened mechanical sensitivity and were deficient in contact righting, wire hang, rotarod, and pole climbing tasks. Male Col9a1(-/-) mice had the highest mean serum hyaluronan levels and strong histologic evidence of cartilage erosion. Intervertebral disc degeneration was also detected, with Col9a1(-/-) mice having an increased incidence of disc tears.

CONCLUSION

These data describe a Col9a1(-/-) behavioral phenotype characterized by altered gait, increased mechanical sensitivity, and impaired function. These gait and functional differences suggest that Col9a1(-/-) mice select locomotive behaviors that limit joint loads. The nature and magnitude of behavioral changes were largest in male mice, which also had the greatest evidence of knee degeneration. These findings suggest that Col9a1(-/-) mice present behavioral changes consistent with anatomic signs of OA and intervertebral disc degeneration.

Ankylosing enthesitis associated with up-regulated IFN-gamma and IL-17 production in (BXSB x NZB) F(1) male mice: a new mouse model

We found that in contrast to (BXSB x NZB) F(1) female mice that spontaneously develop severe systemic lupus erythematosus (SLE), male (BXSB x NZB) F(1) mice are not prone to SLE, but instead develop seronegative ankylosing enthesitis in ankle/tarsal joints only when caged in groups, with the incidence reaching 83% at 7 months of age. This ankylosis is microscopically characterized by a marked proliferation of fibroblast-like cells positive for bone morphogenetic protein (BMP)-2 in association with heterotropic formation of cartilages and bones in hyperplastic entheseal tissues and subsequent fusion of tarsal bones. Elevated potentials of popliteal lymph node T cells producing interleukin (IL)-17 and interferon (IFN)-gamma were significantly associated with joint ankylosis, suggesting the involvement of these cytokines in effector phase mechanisms of the disease, including up-regulated BMP signaling pathways. There was no difference in serum autoantibody levels between affected and unaffected mice. Parental BXSB and NZB strains of both sexes did not develop the disease even when caged in groups, indicating that the disease develops under the control of susceptibility genes derived from both parental strains. These results indicate that (BXSB x NZB) F(1) male mice are a suitable model for clarifying genetic, environmental and molecular mechanisms underlying ankylosing enthesitis and related diseases.

Novel recombinant congenic mouse strain developing arthritis with enthesopathy

Based on the hypothesis that the complex pathological and immunological manifestations of rheumatoid arthritis (RA) and the related diseases are under the control of multiple gene loci with allelic polymorphism, a recombinant congenic mouse strain was prepared between an MRL/Mp-lpr/lpr (MRL/lpr) strain, which develops arthritis resembling RA, and a non-arthritic strain C3H/HeJ-lpr/lpr (C3H/lpr). In MRL/lpr x (MRL/lpr x C3H/lpr) F1 mice, the mice developing severe arthritis were selected based on joint swelling to further continue intercrosses, and then an McH-lpr/lpr-RA1 (McH/lpr-RA1) strain was established and its histopathological phenotypes of joints and autoimmune traits were analyzed. Arthritis in McH/lpr-RA1 mice developed at a higher incidence by 20 weeks of age, compared with that in the MRL/lpr mice, who had severe synovitis (ankle, 60.3%; knee, 65.1%), and also fibrous and fibrocartilaginous lesions of articular ligamenta resembling enthesopathy (ankle, 79.4%; knee, 38.1%), resulting in ankylosis. The lymphoproliferative disorder was less, and serum levels of IgG and IgG autoantibodies including anti-dsDNA and rheumatoid factor were lower than those of both MRL/lpr and C3H/lpr strains. McH/lpr-RA1 mice may provide a new insight into the study of RA regarding the common genomic spectrum of seronegative RA and enthesopathy.

Collagen-induced arthritis

The collagen-induced arthritis (CIA) mouse model is the most commonly studied autoimmune model of rheumatoid arthritis. Autoimmune arthritis is induced in this model by immunization with an emulsion of complete Freund's adjuvant and type II collagen (CII). This protocol describes the steps necessary for acquisition, handling and preparation of CII, as well as selection of mouse strains, proper immunization technique and evaluation of the arthritis incidence and severity. Typically, the first signs of arthritis appear in this model 21-28 days after immunization, and identification of the arthritic limbs is not difficult. Using the protocol described, the investigator should be able to reproducibly induce a high incidence of CIA in various strains of genetically susceptible mice as well as learn how to critically evaluate the pathology of the disease. The total time for the preparation of reagents and the immunization of ten mice is about 1.5 h.

Bone morphogenetic proteins in destructive and remodeling arthritis

Joint destruction and tissue responses determine the outcome of chronic arthritis. Joint inflammation and damage are often the dominant clinical presentation. However, in some arthritic diseases, in particular the spondyloarthritides, joint remodeling is a prominent feature, with new cartilage and bone formation leading to ankylosis and contributing to loss of function. A role for bone morphogenetic proteins in joint remodeling has been demonstrated in the formation of both enthesophytes and osteophytes. Data from genetic models support a role for bone morphogenetic protein signaling in cartilage homeostasis. Finally, this signaling pathway is likely to play a steering role in the synovium.

A non-major histocompatibility locus determines tissue specificity in the pathogenic process underlying synovial proliferation in a mouse arthropathy model

BACKGROUND

The incidence and characteristics of spontaneous ankylosis in the ankle of specific F(1) mice descended from two Fas-deficient strains were reported. Here the coincidence of synovial proliferation and ankylosis in the descendent F(2) mice is reported.

AIM

To clarify whether the two distinct manifestations are genetically different.

METHODS

An arthropathic group of mice (MCF(2)) were bred by intercrossing MRL/Mp.Fas(lpr)-sap(-)/sap(-) and C3H/He.Fas(lpr) mice. All mice were killed by bleeding under anaesthesia when they were 6 months old. Pathological grades for synovial proliferation were determined by microscopical examination. To obtain a linkage locus, the whole genome of male MCF(2) mice was scanned by using 73 microsatellite markers.

RESULTS

Synovial proliferation was equally observed in male and female MCF(2) mice. No correlation was observed between the grades of synovial proliferation and the ankylosis occurring in the MCF(2) mice. A suggestive susceptibility locus was shown in the middle of chromosome 11. This locus was an MRL allele with a recessive inheritance mode.

CONCLUSION

The pathogenic mechanisms of synovial proliferation and ankylosis are genetically different. The present locus is overlapped with some loci associated with rheumatoid arthritis and with others associated with experimental arthritides.

Genetic characterisation of spontaneous ankylosing arthropathy with unique inheritance from Fas-deficient strains of mice

BACKGROUND

The spontaneous onset of macroscopic arthropathy in the ankle of the particular F1 mice descended from two Fas-deficient strains of mice; a mutant substrain of MRL/Mp.Fas(lpr) (MRL/rpl) and C3H/He.Fas(lpr) (C3H/lpr) was recently observed.

AIM

To histopathologically characterise and genetically interpret the unique inheritance mode of disease in this arthropathy model.

METHODS

MRL/rpl, C3H/lpr, (MRL/rpl x C3H/lpr; MC) F1, (C3H/lpr x MRL/rpl; CM) F1 and MCF2 mice were bred under specific pathogen-free conditions. Histopathological grade of arthropathy was determined at 6 months by examination under a light microscope. To search for a linkage locus to the arthropathy, the whole genome of selected 48 male MCF2 mice with 71 polymorphic microsatellite markers was scanned, followed by quantitative trait locus analysis.

RESULTS

The incidence of microscopically defined arthropathy in the male and female MCF1 groups was 100% and 19.4%, respectively. No incidence was observed in the parental strains, MRL/rpl and C3H/lpr, and in CMF1 mice. In the MCF1 mice, the arthropathy mainly affected the ankle joints and was histopathologically characterised by marked entheseal proliferation with chondrocytic differentiation and ossification in the ankle joints, the manifestations similar to ankylosing enthesitis reported previously. An MRL/rpl-derived autosomal dominant susceptibility locus was mapped in the distal of D7Mit68 (60 cM) to the ankylosis onset.

CONCLUSION

The MCF1 mice stably develop spontaneous ankylosing disorders in the ankle, with a male predominance. The unique inheritance mode of ankylosis is possibly interpreted by the genetic interaction between the autosomal dominant locus and a Y-linked locus.

Psoriatic arthritis and Klinefelter syndrome: case report

Psoriatic arthritis (PsA) is a well-known disease characterized by psoriasis and inflammatory joint disease, with distinct clinical and radiological features to differentiate it from other arthropathies. Whereas many cases of coexistence of arthritis and other autoimmune disorders with chromosomal abnormalities have been reported, the occurrence of PsA and Klinefelter syndrome has not been reported previously. A case of Klinefelter syndrome and PsA was reported. This case report emphasizes the role played by sex hormones and chromosomal abnormalities in the pathogenesis of autoimmune disorder, and to our knowledge, this is an uncommon case of a patient with Klinefelter syndrome who developed PsA.

Type IX collagen deficiency enhances the binding of cartilage-specific antibodies and arthritis severity

Joint cartilage is attacked in both autoimmune inflammatory and osteoarthritic processes. Type IX collagen (CIX) is a protein of importance for cartilage integrity and stability. In this study we have backcrossed a transgenic disruption of the col9a1 gene, which leads to an absence of CIX, into two different inbred mouse strains, DBA/1 and B10.Q. None of the CIX-deficient mice developed observable clinical or microscopic osteoarthritis, but DBA/1 male mice had more pronounced enthesopathic arthritis, the so-called stress-induced arthritis. Both DBA/1 and B10.Q strains are susceptible to the induction of collagen-induced arthritis, and CIX deficiency in both strains led to the development of a more severe arthritis than in the controls. Induction of arthritis with monoclonal antibodies against type II collagen (CII) led to an earlier arthritis in the paws that also involved the knee joints. The antibodies used, which were specific for the J1 and the C1I epitopes of CII, initiate their arthritogenic attack by binding to cartilage. The C1I-specific antibodies bound to cartilage better in CIX-deficient mice than in wild-type animals, demonstrating that the lack of CIX in cartilage leads to an increased accessibility of structures for antibody binding and thus making the joints more vulnerable to inflammatory attack. These findings accentuate the importance of cartilage stability; cartilage disrupted as a result of genetic disorders could be more accessible and vulnerable to an autoimmune attack by pathogenic antibodies.

Modulation of bone morphogenetic protein signaling inhibits the onset and progression of ankylosing enthesitis

Joint ankylosis is a major cause of disability in the human spondyloarthropathies. Here we report that this process partially recapitulates embryonic endochondral bone formation in a spontaneous model of arthritis in DBA/1 mice. Bone morphogenetic protein (BMP) signaling appears to be a key molecular pathway involved in this pathological cascade. Systemic gene transfer of noggin, a BMP antagonist, is effective both as a preventive and a therapeutic strategy in the mouse model, mechanistically interfering with enthesial progenitor cell proliferation in early stages of the disease process. Immunohistochemical staining for phosphorylated smad1/5 in enthesial biopsies of patients with spondyloarthropathy reveals active BMP signaling in similar target cells. Our data suggest that BMP signaling is an attractive therapeutic target for interfering with structural changes in spondyloarthropathy either as an alternative or complementary approach to current antiinflammatory treatments.

Accelerating effect of an MRL gene locus on the severity and onset of arthropathy in DBA/1 mice

OBJECTIVE

To analyze the influence of the genetic background of an arthritis-prone strain of mice, MRL, on the spontaneous development of arthropathy in DBA/1 mice, which histopathologically resembles enthesopathy in humans, and to clarify the strain-specific gene loci and their interactions that confer susceptibility to arthropathy.

METHODS

MRL, DBA/1, (MRL x DBA/1)F(1), and (MRL x DBA/1)F(2) intercross mice were prepared, and the severity and onset of arthropathy of the ankle joints in individual mice were quantified (0-3 and 0-5 scale, respectively). A genome-wide scan of 271 male F(2) intercross mice with polymorphic microsatellite markers was performed.

RESULTS

Only male DBA/1, (MRL x DBA/1)F(1), and (MRL x DBA/1)F(2) mice developed arthropathy. The macroscopic and histopathologic findings of arthropathy in the F(2) mice were similar to those in the parental DBA/1 mice, but the onset was significantly earlier. In the quantitative trait locus analysis of male F(2) mice, 1 susceptibility locus for both the severity and early onset of the disease in the region of an MRL allele, Amd1, was located at marker D10Mit259 (map position 40.0 cM), which was common to 1 of the sialadenitis susceptibility loci in MRL mice, Asm1. Another susceptibility locus for the severity and early onset of arthropathy in the region of a DBA allele, Amd2, was located at D3Mit46 (29.5 cM). These loci manifested an additive effect on the development of arthropathy.

CONCLUSION

Arthropathy in DBA/1 mice is under the control of an allelic combination of gene loci, one of which is common to the locus for sialadenitis in MRL/MpJ-lpr/lpr mice.

A robust model of adjuvant-induced chronic unilateral arthritis in two mouse strains

We have developed a model of unilateral adjuvant-arthritis that is reproducible across two mouse strains. DBA/1 and C57BL/6 male mice were injected intra-articularly into a stifle joint with FCA (5 microg in 5 microl) once per week for 4 weeks. Measurements of joint diameter and joint histopathology were used to monitor the course of the arthritis. Inflammatory hyperalgesia was assessed as the pressure causing a limb withdrawal. FCA injection into the mouse stifle joint caused a pronounced increase in joint diameter when compared to the contralateral limb or vehicle controls. There was also a significant decrease in the pressure required to elicit a withdrawal of the injected limb. Histology showed arthritic changes, including synovial hypertrophy and polymorphonuclear neutrophil infiltration. In established chronic inflammation, seven days of treatment with either indomethacin (NSAID) or prednisolone (steroid) caused a significant decrease in joint inflammation and associated hyperalgesia. FCA induces a long-lasting joint inflammation in DBA/1 and C57BL/6 mice, which is restricted to the injected joint and exhibits some of the pathology associated with an arthritic condition. This model will be useful in examining the effect of joint inflammation on nociceptor sensitisation in both normal and transgenic mice.

Dependence on interferon-γ for the spontaneous occurrence of arthritis in DBA/1 mice

OBJECTIVE

Male DBA/1 mice are known to spontaneously develop arthritis in the hind legs. The present study was undertaken to investigate the role of endogenous interferon-gamma (IFNgamma) in the pathogenesis of this ankylosing enthesopathy.

METHODS

The role of IFNgamma was studied by examining the development of arthritis in IFNgamma receptor-knockout (IFNgammaR-KO) DBA/1 mice as compared with wild-type mice, and by treatment of wild-type mice with monoclonal anti-IFNgamma antibody. IFNgamma-disrupted and wild-type mice were mixed and housed in the same cage, and clinical symptoms of arthritis were assessed weekly for at least 9 weeks. Histologic examination was performed at the end of the experiment.

RESULTS

In DBA/1 wild-type mice, 70% of the animals developed clinical symptoms of spontaneous arthritis, such as redness and swelling of the proximal interphalangeal joints, toe stiffness, and ankylosis. As evident from microscopic evaluation, the arthritis was mainly characterized by formation of new cartilage and bone, originating at the entheses and leading to ankylosis. The incidence and severity of arthritis, both clinically and histologically, were significantly reduced in IFNgammaR-KO mice. In wild-type mice, neutralizing anti-IFNgamma antibody inhibited the occurrence of the disease for the duration of treatment.

CONCLUSION

The results suggest that endogenous IFNgamma plays an important role in the initial stages of spontaneous arthritis, and that the inflammatory components in its pathogenesis are more prominent than has been believed. In view of the similarity between this disease and spondylarthropathies in humans, the data suggest that endogenous IFNgamma may also play a disease-promoting role in the human condition and thus may serve as a target for therapy.

Sex effect on clinical and immunologic quantitative trait loci in a murine model of rheumatoid arthritis

OBJECTIVE

To explore the effect of sex on clinical and immunologic traits in major histocompatibility complex-matched (H-2d) F(2) hybrid mice with proteoglycan (PG)-induced arthritis and to identify how the quantitative trait locus (QTL) on the X chromosome influences the onset QTL of another chromosome.

METHODS

(BALB/c x DBA/2)F(2) hybrid mice were immunized with cartilage PG, and a genome-wide linkage analysis was performed using >200 simple sequence-length polymorphic markers. The major clinical traits (susceptibility, onset, and severity) were assessed, and PG-specific T and B cell responses, and the production of proinflammatory and antiinflammatory cytokines (tumor necrosis factor alpha, interleukin-1 [IL-1], IL-6, interferon-gamma, IL-4, IL-10, and IL-12) were measured in 133 arthritic and 426 nonarthritic female and male F(2) hybrid mice. The major clinical and immunologic traits were linked to genetic loci, and potential linkages among these QTLs and the effect of sex were analyzed.

RESULTS

Thirteen QTLs reported in previous studies were confirmed. Binary traits (susceptibility to arthritis) and disease onset were female specific and were identified on chromosomes 3, 7, 10, 11, 13, and X. QTLs for disease severity were mostly male specific and were located on chromosomes 1, 4, 5, 8, 14, 15, and 19. In addition, we identified 4 new QTLs for the onset of arthritis on chromosomes 3, 4, and 11, and 1 new QTL for severity on chromosome 14; all showed a strong gender association. A locus on the X chromosome interacted with a QTL on chromosome 10, and these 2 loci together seemed to control disease incidence and onset. Most of the clinical traits (QTLs) shared common regions with the immunologic traits and frequently showed a locus-locus interaction.

CONCLUSION

Numerous immunologic QTLs overlap with clinical QTLs, thus providing information about possible mechanisms underlying QTL function. Disease susceptibility and onset showed predominant linkage with the female sex, under the control of a QTL on the X chromosome, while the severity QTLs were more strongly linked to the male sex.

Identification of Genes Controlling Collagen-Induced Arthritis in Mice: Striking Homology with Susceptibility Loci Previously Identified in the Rat

The susceptibility to collagen-induced arthritis in the highly susceptible DBA/1 mouse has earlier been shown to be partly controlled by the MHC class II gene Aq. To identify susceptibility loci outside of MHC, we have made crosses between DBA/1 and the less susceptible B10.Q strain, both expressing the MHC class II gene Aq. Analysis of 224 F2 intercross mice with 170 microsatellite markers in a genome-wide scan suggested 4 quantitative trait loci controlling arthritis susceptibility located on chromosomes 6, 7, 8, and 10. The locus on chromosome 6 (Cia6), which was associated with arthritis onset, yielded a logarithm of odds score of 4.7 in the F2 intercross experiment and was reproduced in serial backcross experiments. Surprisingly, the DBA/1 allele had a recessive effect leading to a delay in arthritis onset. The suggestive loci on chromosomes 7 and 10 were associated with arthritis severity rather than onset, and another suggestive locus on chromosome 8 was most closely associated with arthritis incidence. The loci on chromosomes 7, 8, and 10 all appeared to contain disease-promoting alleles derived from the DBA/1 strain. Interestingly, most of the identified loci were situated in chromosomal regions that are homologous to regions in the rat genome containing susceptibility genes for arthritis; the mouse Cia6 locus is homologous with the rat Cia3, Pia5, Pia2, and Aia3; the locus on chromosome 7 (Cia7) is homologous with the rat Cia2; and the locus on chromosome 10 (Cia8) is homologous with the rat Cia4.

Influence of long term silicone implantation on type II collagen induced arthritis in mice

OBJECTIVES

The use of silicone implants in cosmetic and reconstructive surgery has been implicated in the development of autoimmune connective tissue diseases. Previous investigation of the influence of short-term silicone implantation using an experimental model of rheumatoid arthritis revealed no adverse influence upon disease despite the generation of autoantibodies against silicone bound proteins. This study was designed to examine the influence of long term implantation of different forms of silicone in collagen induced arthritis.

METHODS

DBA/1 mice were surgically implanted with silicone elastomers, gel or oil nine months before immunisation with type II collagen emulsified in Freund's incomplete adjuvant. The incidence and severity of arthritis, antibodies to type II collagen, and serum cytokines were assessed and compared with sham implanted mice. Silicone implants were recovered, and autoantibodies to silicone bound proteins evaluated in arthritic and non-arthritic mice.

RESULTS

Immunisation with CII/FIA resulted in a 30% arthritis incidence in sham implanted DBA/1 mice. Long term silicone implantation resulted in an increased incidence of arthritis, with a significant increase of 90% arthritis in animals implanted with silicone elastomers. Animals implanted with silicone elastomer also developed foreign body sarcomas during the study. Serum concentrations of interleukin 10 were increased in mice implanted with elastomers and immunised with CII/FIA, while interleukin 5 concentrations were significantly diminished in these mice. The production of autoantibodies to autologous silicone bound proteins, including anti-type I collagen antibody, was also attributed to the implantation of either silicone gel or silicone elastomer in type II collagen immunised animals.

CONCLUSIONS

These data suggest that long term silicone implantation results in both the production of autoantibodies to connective tissue antigens and increased susceptibility to an experimental model of autoimmune disease.

Autoimmunity: Another pathway towards arthritis

A new pathway leading to arthritis has been revealed by the discovery that antibodies specific for a ubiquitously expressed antigen are able to transfer a severe arthritic phenotype in mice. This new model will be useful for further analyses of the different pathways involved in rheumatoid arthritis.

Collagen-induced arthritis development requires alpha beta T cells but not gamma delta T cells: studies with T cell-deficient (TCR mutant) mice

Collagen type II (CII)-induced arthritis (CIA) in mice is a model for rheumatoid arthritis (RA) in which the role of T lymphocytes remains controversial. To clarify this, we have bred a targeted gene deletion of TCR beta or delta loci into two mouse strains susceptible to CIA, the B10.Q and DBA/1 strains. The TCRbeta-/- mice lacked alphabeta T cells, which was compensated by an expansion of B cells, gammadelta T cells and NK cells. The beta-/- mice, but not control beta+/- littermates, were completely resistant to CIA. The production of anti-CII IgG antibodies was also abolished in beta-/- mice, revealing a strict alphabeta T cell dependency. In contrast, beta-/- mice produced reduced, but significant, anti-CII IgM titers after immunization with either CII or ovalbumin, indicating a multispecificity for these alphabeta T cell-independent IgM antibodies. The TCRdelta-/- mice lacked gammadelta T cells but had no other significant changes in lymphocyte or monocyte subsets. The cytokine response (IL-2, IL-4, IL-10 and IFN-gamma) in delta-/- mice, quantified by flow cytometry staining of mitogen-stimulated lymphocytes, was indistinguishable from normal mice. Likewise, no statistically significant differences were observed in CIA between mice lacking gammadelta T cells and control littermates, considering arthritis incidence, day of disease onset, maximum arthritic score, anti-CII IgG titers and disease course. We conclude that alphabeta T cells are necessary for CIA development and for an IgG response towards CII, whereas gammadelta T cells are neither necessary nor sufficient for development of CIA.

Transgenic mouse models of rheumatoid arthritis

A combined analysis of data available in the literature has demonstrated that the strongest association in rheumatoid arthritis (RA) is with DR genes rather than DQ or DP genes. Functional and structural data of RA-associated DR molecules suggest that selective binding of peptides is the molecular basis for this association. The establishment of functional transgenic mice expressing RA-associated HLA class II molecules has proven to be useful in the delineation of the role of these molecules in immune responses possibly related to RA and in the development of humanized models for this disease. Such humanized mice develop arthritis upon immunization with type II collagen (CII), which shows similarities with RA. Interestingly, the immunodominant T-cell determinant in CII is derived from positions 261-273, which overlap with a previously identified CII T-cell epitope restricted by the mouse Aq molecule, which is associated with collagen-induced arthritis. Studies in collagen transgenic mice have shown that recognition of this peptide may lead either to T-cell tolerance or to an arthritogenic response. It is therefore proposed that the T-cell recognition of the CII peptide bound by DR molecules is one of the molecular interactions of critical importance in the development of RA and accordingly also an important target for prevention and treatment of this disease.

Mice Lacking Mature T and B Lymphocytes Develop Arthritic Lesions after Immunization with Type II Collagen

Collagen-induced arthritis in DBA/1 mice is a widely used experimental model of rheumatoid arthritis. The induction phase of the disease is thought to be dependent upon MHC-restricted T and B cell-mediated immune responses to type II collagen, but an influence of additional non-MHC-restricted mechanisms has also been proposed. In this study, we report that type II collagen immunization of DBA/1 mice lacking mature T and B lymphocytes resulted in the development of arthritic lesions, which were characterized by synovial hyperplasia with occasional inflammation as well as cartilage and bone destruction. The specificity of disease induction to type II collagen was confirmed, because arthritis could not be induced when control preparations of OVA or adjuvant alone were administered. A delay in clinical disease onset and a reduction in severity between lymphocyte-positive and -negative DBA/1 mice confirmed that lymphocytes play an important role in disease; however, similar pathologic features and normal incidence suggest that lymphocyte-independent mechanisms of disease induction also operate in the standard collagen-induced arthritis model. We conclude that adaptive immune responses are not the only arthritogenic mechanism and hypothesize that the nonantigenic properties of type II collagen can also lead to arthritis.

Histopathological characterization of spontaneously developing osteoarthropathy in the BCBC/Y mouse established newly from B6C3F1 mice

A new breed of mouse showing cinnamon-color of hair and osteoarthropathy was born from mouse of the B6C3F1 strain, and was named the BCBC/Y mouse. The incidence and severity of the articular lesions increased with aging, and by 10 to 22 months of age, many mice showed moderate-severe motor paresis with ankylotic changes of the limb joints. Abnormal radiographic changes were observed at many joints with increasing age. There was bone and joint deformity, followed by progressive osteoarthritic changes and ankylosis of the limb joints. Histopathologically, degenerative changes, followed by loosening, fissuring and erosion of the articular cartilage were observed at early stage of articular lesions. Unilateral progressive changes, characterized by joint fusion with abnormal osteophytes, were observed at late stage of articular lesions with aging. For successive breeding to establish a homogeneous strain, generation mice retained the symptoms of the primary mice. Thus, these BCBC/Y mice may be a useful as mode to elucidate the hereditary background and hyperplastic changes of the osteochondrocytes for pathogenesis of the osteoarthropathy.

Spontaneous osteoarthritic lesions in a new mutant strain of the mouse

In our laboratory, mice showing signs of osteoarthritic lesions with cinnamon colored (yellowish-brown) hair were discovered in a colony of B6C3F1 mice. This mouse is characterized by tiptoe walking and swelling and ankylotic changes in the ankle joint. As to radiographic findings, osteoarthritic changes, such as erosion and/or fusion of the bone tissue, were evident in the ankle joints. Histopathological characteristics included irregularity of articular surfaces caused by fissuring and/or erosion with degeneration of articular cartilage, as well as osteophytes with abnormal proliferation of chondrocytes in joint margin regions. Subsequently, ankylotic changes in the ankle joints were completed in the formation of a cartilaginous bridge and fusion of articular cavity with abnormal proliferation of cartilaginous or bone tissues. This mouse strain may provide an additional animal model that is valuable in the study of human osteoarthritis (OA).

Staphylococcal enterotoxin B induces arthritis in female DBA/1 mice but fails to induce activation of type II collagen-reactive lymphocytes

It has been proposed that superantigens are involved in the pathogenesis of autoimmune diseases. To test the possibility of superantigens inducing arthritis in naive mice, V beta 8-reactive superantigen staphylococcal enterotoxin B (SEB) was injected into naive mice. We used female DBA/1 mice, because they were susceptible to collagen-induced arthritis (CIA), in which the pathogenic T cells were supposed to preferentially use limited V betas of T cell receptors including V beta 8. Mild monoarthritis developed in uninjected hindlimbs of mice administered with SEB in higher frequency (an average incidence of 24%) than the control phosphate-buffered saline-injected mice (4.2%). Autoimmune responses in mice administered with SEB were compared with those in mice developing CIA. However, activation of type II collagen (IIC)-reactive T cells was not detected in SEB-injected mice. Production of autoantibodies, anti-IIC antibody and rheumatoid factor was also undetected. Although exact mechanisms of pathogenesis of this arthritis remain to be known, V beta 8+ T cells were activated for a long period and the unresponsiveness of V beta 8+ T cells was not detected in this strain. From these results, we discuss the pathogenesis of arthritis induced by SEB and the possibility that superantigen may play a role in the induction of autoimmune diseases.

The influence of silicone implantation on type II collagen-induced arthritis in mice

OBJECTIVE

To determine whether silicone implantation exacerbates autoimmune disease in a murine experimental model of arthritis.

METHODS

DBA/1 mice were implanted with silicone in the form of an elastomer, gel, or oil, and immunized with type II collagen. The influence of silicone implantation on collagen-induced arthritis and the immune response to type II collagen were determined by comparison against control mice receiving sham implantation. Adjuvant effects of silicone implantation were examined by measuring cytokine levels in implanted animals and assessing autoantibodies against proteins extracted from recovered silicone implants.

RESULTS

No adverse influence of silicone implantation on the clinical aspects of collagen-induced arthritis was observed. Further, polydimethylsiloxane silicone oil failed to serve as an adjuvant in the immune or arthritogenic response to type II collagen in mice. Cytokine analysis indicated that tumor necrosis factor alpha levels were lower and interleukin-2 levels were higher in silicone-implanted mice. The development of arthritis increased protein binding to implanted elastomers and gel, and autoantibodies against silicone-bound proteins were present in sera from arthritic mice and absent in sera from nonarthritic mice.

CONCLUSION

The data suggest that silicone implantation may result in autoantibodies against silicone-bound proteins, and the presence of arthritis may either provoke or increase the level of such autoantibodies. However, silicone implantation did not increase the incidence or severity of disease compared with sham-operated controls. Thus, it appears that autoantibodies against silicone-bound proteins may not have pathologic significance in this experimental model of arthritis.

Grouped caging predisposes male mice to ankylosing enthesopathy

OBJECTIVE

To evaluate the number of males per cage as a possible risk factor for murine ankylosing enthesopathy (ANKENT)--a spontaneous joint disease with parallels to human seronegative spondylarthropathies--since ANKENT shows incomplete penetrance of genetic susceptibility factors among individuals living in a stable environment.

METHODS

Frequency of ANKENT was compared among males housed with females, with other males, or alone.

RESULTS

In three independent cohorts, a trend was observed that males housed with females rarely develop the disease, in contrast to males housed with other males (P < 0.25, P < 0.05, and P < 0.01). Furthermore, no males caged alone developed ANKENT, whereas disease did occur in males grouped together (P < 0.01). When healthy males (retired breeders) were recaged either alone or with other males, ANKENT developed among the grouped males only (P < 0.005).

CONCLUSIONS

Caging males together is a relative risk factor for ANKENT. Grouped caging may perturb the immune system through endocrine pathways or modify microbiological load through behaviour (for example, infection due to biting).

Hormones and autoimmunity: animal models of arthritis

Hormones, particularly those involved in the hypothalamic-pituitary-gonadal and -adrenal axes (HPG and HPA), play important roles in various animal models of autoimmunity such as systemic lupus erythematosus in mice and collagen-induced arthritis (CIA) in mice and rats, and the streptococcal cell wall, adjuvant and avridine arthritis models in rats. Intimately linked to the subject of hormones and autoimmunity are gender, sex chromosomes and age. The importance of these factors in the various animal models is emphasized in this chapter. Several major themes are apparent. First, oestrogens promote B-cell dependent immune-complex mediated disease (e.g. lupus nephritis) but suppress T-cell dependent pathology (CIA in mice and rats), and vice versa. Second, testosterone's effects are complicated and depend on species and disease model. In rats, testosterone suppresses both T-cell and B-cell immunity. In mice, the effects are complex and difficult to interpret, e.g. they tend to enhance CIA arthritis and suppress lupus. Sex chromosome/sex hormone interactions are clearly involved in generating these complicated effects. Third, studies in Lewis and Fischer F344 rats exemplify the importance of corticosteroids, corticotrophin releasing hormone and the HPA axis in the regulation of inflammation and the predisposition to autoimmune diseases. Fourth, the HPA axis is intimately linked to the HPG axis and is sexually dimorphic. Oestrogens stimulate higher corticosteroid responses in females. The animal model data have major implications for understanding autoimmunity in humans. In particular, adrenal and gonadal hormone deficiency is likely to facilitate T-cell dependent diseases like rheumatoid arthritis, while high oestrogen levels or effects, relative to testosterone, are likely to promote B-cell dependent immune-complex-mediated diseases such as lupus nephritis.

Systemic versus cartilage-specific expression of a type II collagen-specific T-cell epitope determines the level of tolerance and susceptibility to arthritis

Immunization of mice with rat type II collagen (CII), a cartilage-specific protein, leads to development of collagen-induced arthritis (CIA), a model for rheumatoid arthritis. To define the interaction between the immune system and cartilage, we produced two sets of transgenic mice. In the first we point mutated the mouse CII gene to express an earlier defined T-cell epitope, CII-(256-270), present in rat CII. In the second we mutated the mouse type I collagen gene to express the same T-cell epitope. The mice with mutated type I collagen showed no T-cell reactivity to rat CII and were resistant to CIA. Thus, the CII-(256-270) epitope is immunodominant and critical for development of CIA. In contrast, the mice with mutated CII had an intact B-cell response and had T cells which could produce gamma interferon, but not proliferate, in response to CII. They developed CIA, albeit with a reduced incidence. Thus, we conclude that T cells recognize CII derived from endogenous cartilage and are partially tolerized but may still be capable of mediating CIA.