A mouse model of autoimmune inner ear disease without endolymphatic hydrops.

Autoimmune inner ear disease (AIED) is an organ-specific disease characterized by irreversible, prolonged, and progressive hearing and equilibrium dysfunctions. The primary symptoms of AIED include asymmetric sensorineural hearing loss accompanied by vertigo, aural fullness, and tinnitus. AIED is divided into primary and secondary types. Research has been conducted using animal models of rheumatoid arthritis (RA), a cause of secondary AIED. However, current models are insufficient to accurately analyze vestibular function, and the mechanism underlying the onset of AIED has not yet been fully elucidated. Elucidation of the mechanism of AIED onset is urgently needed to develop effective treatments. In the present study, we analyzed the pathogenesis of vertigo in autoimmune diseases using a mouse model of type II collagen-induced RA. Auditory brain stem response analysis demonstrated that the RA mouse models exhibited hearing loss, which is the primary symptom of AIED. In addition, our vestibulo-oculomotor reflex analysis, which is an excellent vestibular function test, accurately captured vertigo symptoms in the RA mouse models. Moreover, our results revealed that the cause of hearing loss and vestibular dysfunction was not endolymphatic hydrops, but rather structural destruction of the organ of Corti and the lateral semicircular canal ampulla due to an autoimmune reaction against type II collagen. Overall, we were able to establish a mouse model of AIED without endolymphatic hydrops. Our findings will help elucidate the mechanisms of hearing loss and vertigo associated with AIED and facilitate the development of new therapeutic methods.

Helminth-induced impairment of humoral immunity differently contribute to their anti-arthritic effects in mice: Comparison of Schistosoma mansoni and Trichinella spiralis.

AIMS: We have previously reported reduction of anti-type II collagen (IIC) IgG levels in collagen-induced arthritis (CIA) by Schistosoma mansoni (Sm) and Trichinella spiralis (Ts). To clarify the contribution of the impairment of humoral immunity to their anti-arthritic activities, we herein investigated the relationship between anti-IIC IgG levels and arthritic swelling in Sm- or Ts-infected mice. METHODS AND RESULTS: Male DBA/1J mice were infected with Sm cercariae or Ts muscle larvae prior to the IIC immunization. In the Sm-infected mice, paw swelling and anti-IIC IgG levels were continuously lower than those of non-infected control group. In contrast, arthritic swelling in the Ts-infected mice only decreased in the early phase of CIA progression, despite the continued impairment of anti-IIC IgG production throughout the experimental period. Correlation coefficients between residual paw swelling and anti-IIC IgG titers were similar or higher in the Sm group than in the control group, but were similar or lower in the Ts group than in the control group. CONCLUSION: The down-modulations of anti-IIC IgG levels by the two parasitic infections and the correlation analyses suggest that the anti-arthritic activity of Sm was primarily attributed to the modulation of IgG-independent arthritogenic mechanisms and secondarily to the impairment of anti-IIC IgG production. In contrast, Ts could alleviate CIA mainly via the impairment of antibody production.

Different protective efficacies of a novel antigen-specific DNA vaccine encoding chicken type â ¡ collagen via intramuscular, subcutaneous, and intravenous vaccination against experimental rheumatoid arthritis.

Tolerizing DNA vaccines encoding key autoantigens are one of emerging strategies for the treatment of rheumatoid arthritis (RA). Among these vaccines, the most representative is pcDNA-CCOL2A1, an antigen-specific DNA vaccine encoding chicken type Ⅱ collagen (CCⅡ) with significant therapeutic and prophylactic efficacy in collagen-induced arthritis (CIA) rat models. We compared the in situ expression levels of CCOL2A1-mRNA and CCⅡ protein and the protective efficacies against CIA after a single dose (300 µg/kg) of this vaccine via intramuscular (IM), subcutaneous (SC) and intravenous (IV) vaccinations. The IM vaccination routes resulted in good protective efficacies in terms of decreasing CIA incidence and severity and significantly improved radiographic and histopathologic findings and scores of joints. Furthermore, IM, SC, and IV vaccinations markedly decreased serum levels of anti-type Ⅱ collagen (CⅡ) IgG antibodies, but only IM vaccination significantly reduced serum levels of rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibody. The vaccine exhibited a continuous CCOL2A1-mRNA expression in the tail and abdominal subcutaneous tissue injection sites, but no CCOL2A1-mRNA signal was observed in muscle. Strikingly, CCⅡ protein expression levels at the three injection sites were comparable with minimal variation. IM administration may be considered the preferred route for RA treatment in clinical practice.

In vivo generation of collagen specific Tregs with AAV8 suppresses autoimmune responses and arthritis in DBA1 mice through IL10 production.

Available therapeutics for autoimmune disorders focused on mitigating symptoms, rather than treating the cause of the disorder. A novel approach using adeno-associated virus (AAV) could restore tolerance to the autoimmune targets and provide a permanent treatment for autoimmune diseases. Here, we evaluated the ability of collagen II T-cell epitopes packaged in adeno-associated virus serotype 8 (AAV-8) vectors to reduce pathogenic cellular and humoral responses against collagen and to mitigate the disease in the collagen-induced arthritis mouse model. The cytokines and immune cells involved in the immune suppression were also investigated. Mice treated with AAV-8 containing collagen II T-cell epitopes demonstrated a significant reduction in the arthritis symptoms, pathogenic collagen specific antibody and T cell responses. The AAV-8 mediated immune suppression was mediated by increased interleukin-10 expression and regulatory T cells expansion. Altogether, this study strengthens the notion that AAV vectors are promising candidates for the treatment of autoimmune diseases.

BTN2A2 protein negatively regulates T cells to ameliorate collagen-induced arthritis in mice.

Rheumatoid arthritis (RA) is an autoimmune disorder characterized by persistent inflammatory responses in target tissues and organs, resulting in the destruction of joints. Collagen type II (CII)-induced arthritis (CIA) is the most used animal model for human RA. Although BTN2A2 protein has been previously shown to inhibit T cell functions in vitro, its effect on autoimmune arthritis has not been reported. In this study, we investigate the ability of a recombinant BTN2A2-IgG2a Fc (BTN2A2-Ig) fusion protein to treat CIA. We show here that administration of BTN2A2-Ig attenuates established CIA, as compared with control Ig protein treatment. This is associated with reduced activation, proliferation and Th1/Th17 cytokine production of T cells in BTN2A2-Ig-treated CIA mice. BTN2A2-Ig also inhibits CII-specific T cell proliferation and Th1/Th17 cytokine production. Although the percentage of effector T cells is decreased in BTN2A2-Ig-treated CIA mice, the proportions of naive T cells and regulatory T cells is increased. Furthermore, BTN2A2-Ig reduces the percentage of proinflammatory M1 macrophages but increases the percentage of anti-inflammatory M2 macrophages in the CIA mice. Our results suggest that BTN2A2-Ig protein has the potential to be used in the treatment of collagen-induced arthritis models.

Kinase activity profiling reveals contribution of G-protein signaling modulator 2 deficiency to impaired regulatory T cell migration in rheumatoid arthritis.

The ability of regulatory T (Treg) cells to migrate into inflammatory sites is reduced in autoimmune diseases, including rheumatoid arthritis (RA). The reasons for impaired Treg cell migration remain largely unknown. We performed multiplex human kinase activity arrays to explore possible differences in the post-translational phosphorylation status of kinase related proteins that could account for altered Treg cell migration in RA. Results were verified by migration assays and Western blot analysis of CD4+ T cells from RA patients and from mice with collagen type II induced arthritis. Kinome profiling of CD4+ T cells from RA patients revealed significantly altered post-translational phosphorylation of kinase related proteins, including G-protein-signaling modulator 2 (GPSM2), protein tyrosine kinase 6 (PTK6) and vitronectin precursor (VTNC). These proteins have not been associated with RA until now. We found that GPSM2 expression is reduced in CD4+ T cells from RA patients and is significantly downregulated in experimental autoimmune arthritis following immunization of mice with collagen type II. Interestingly, GPSM2 acts as a promoter of Treg cell migration in healthy individuals. Treatment of RA patients with interleukin-6 receptor (IL-6R) blocking antibodies restores GPSM2 expression, thereby improving Treg cell migration. Our study highlights the potential of multiplex kinase activity arrays as a tool for the identification of RA-related proteins which could serve as targets for novel treatments.

Type II Collagen-Specific B Cells Induce Immune Tolerance in Th1-Skewed, Th2-Skewed, and Arthritis-Prone Strains of Mice.

Antigen-specific regulatory T cells play key immune suppressive roles in autoimmune disease models and regulate the peripheral tolerance achieved via anterior chamber-associated immune deviation (ACAID). Articular cartilage has type II collagen (CII), which is a potent autoantigen protein in arthritis. There has not been much research on the clinical importance of CII-associated diseases. Moreover, the capability of CII to induce immune tolerance has not been previously assessed. We reported that delivery of CII either directly into the eye or via intravenous injection of CII-specific ACAID antigen presenting cells (APCs) can induce ACAID. Here, we hypothesized that peripheral tolerance can be induced following adoptive transfer of in vitro generated CII-specific ACAID B cells to naive mice. Delayed hypersensitivity (DTH) assays were used to assess the suppressive ability of adoptively transferred B cells. Immune responses of ACAID B cell-injected mice were significantly suppressed following challenges with CII as compared to positive controls. This effect was replicated in three different strains of mice (C57BL/6, BALB/c, and DBA/1). Thus, CII-specific ACAID B cells were able to induce immune tolerance in Th1-skewed, Th2-skewed, and arthritis-prone mice. ACAID B cell-mediated tolerance induced by CII could have therapeutic implications for the treatment of CII-mediated autoimmune diseases.

Infrared radiation from cage bedding moderates rat inflammatory and autoimmune responses in collagen-induced arthritis.

The development of collagen type II (CII)-induced arthritis (CIA), a model of rheumatoid arthritis, in rats housed in cages with bedding composed of Celliant fibres containing ceramic particles, which absorb body heat and re-emit the energy back to the body in the form of infrared radiation (+IRF rats), and those housed in cages with standard wooden shaving bedding (-IRF control rats) was examined. The appearance of the first signs of CIA was postponed, while the disease was milder (judging by the arthritic score, paw volume, and burrowing behaviour) in +IRF compared with -IRF rats. This correlated with a lower magnitude of serum anti-CII IgG antibody levels in +IRF rats, and lower production level of IL-17, the Th17 signature cytokine, in cultures of their paws. This could be partly ascribed to impaired migration of antigen-loaded CD11b + dendritic cells and their positioning within lymph nodes in +IRF rats reflecting diminished lymph node expression of CCL19 /CCL21. Additionally, as confirmed in rats with carrageenan-induced paw inflammation (CIPI), the infrared radiation from Celliant fibres, independently from immunomodulatory effects, exerted anti-inflammatory effects (judging by a shift in pro-inflammatory mediator to anti-inflammatory/immunoregulatory mediator ratio towards the latter in paw cultures) and ameliorated burrowing behaviour in CIA rats.

Deficiency of ß-arrestin2 exacerbates inflammatory arthritis by facilitating plasma cell formation.

ß-arrestin2 (ß-arr2) is, a key protein that mediates desensitization and internalization of G protein-coupled receptors and participates in inflammatory and immune responses. Deficiency of ß-arr2 has been found to exacerbate collagen antibody-induced arthritis (CAIA) through unclear mechanisms. In this study we tried to elucidate the molecular mechanisms underlying ß-arr2 depletion-induced exacerbation of CAIA. CAIA was induced in ß-arr2-/- and wild-type (WT) mice by injection of collagen antibodies and LPS. The mice were sacrificed on d 13 after the injection, spleen, thymus and left ankle joints were collected for analysis. Arthritis index (AI) was evaluated every day or every 2 days. We showed that ß-arr2-/- mice with CAIA had a further increase in the percentage of plasma cells in spleen as compared with WT mice with CAIA, which was in accordance with elevated serum IgG1 and IgG2A expression and aggravating clinical performances, pathologic changes in joints and spleen, joint effusion, and joint blood flow. Both LPS stimulation of isolated B lymphocytes in vitro and TNP-LPS challenge in vivo led to significantly higher plasma cell formation and antibodies production in ß-arr2-/- mice as compared with WT mice. LPS treatment induced membrane distribution of toll-like receptor 4 (TLR4) on B lymphocytes, accordingly promoted the nuclear translocation of NF-κB and the transcription of Blimp1. Immunofluorescence analysis confirmed that more TLR4 colocalized with ß-arr2 in B lymphocytes in response to LPS stimulation. Depletion of ß-arr2 restrained TLR4 on B lymphocyte membrane after LPS treatment and further enhanced downstream NF-κB signaling leading to additional increment in plasma cell formation. In summary, ß-arr2 depletion exacerbates CAIA and further increases plasma cell differentiation and antibody production through inhibiting TLR4 endocytosis and aggravating NF-κB signaling.

In vitro elimination of autoreactive B cells from rheumatoid arthritis patients by universal chimeric antigen receptor T cells.

OBJECTIVES: Autoreactive B cells play a crucial role in the pathogenesis of rheumatoid arthritis (RA), and B cell-depleting therapies using an antibodies, such as rituximab, have been suggested to be effective in RA treatment. However, transient B cell depletion with rituximab is associated with significant safety challenges related to global suppression of the immune system and thus increases the risks of infection and cancer development. To address selective and persistent issues associated with RA therapy, we developed a customised therapeutic strategy employing universal antifluorescein isothiocyanate (FITC) chimeric antigen receptor T cells (CAR-T cells) combined with FITC-labelled antigenic peptide epitopes to eliminate autoreactive B cell subsets recognising these antigens in RA. METHODS: For a proof-of-concept study, four citrullinated peptide epitopes derived from citrullinated autoantigens, namely, citrullinated vimentin, citrullinated type II collagen, citrullinated fibrinogen and tenascin-C, and a cyclocitrulline peptide-1 were selected as ligands for targeting autoreactive B cells; Engineered T cells expressing a fixed anti-FITC CAR were constructed and applied as a universal CAR-T cell system to specifically eliminate these protein-specific autoreactive B cells via recognition of the aforementioned FITC-labelled autoantigenic peptide epitopes. RESULTS: We demonstrated that anti-FITC CAR-T cells could be specifically redirected and kill hybridoma cells generated by immunisation with antigenic peptides, and autoreactive B cell subsets from RA patients via recognition of corresponding FITC-labelled citrullinated peptide epitopes. Additionally, the cytotoxicity of the CAR-T cells was dependent on the presence of the peptides and occurred in a dose-dependent manner. CONCLUSIONS: The approach described here provides a direction for precise, customised approaches to treat RA and can likely be applied to other systemic autoimmune diseases.

Construction of CII-Specific CAR-T to Explore the Cytokine Cascades Between Cartilage-Reactive T Cells and Chondrocytes.

Cytokine cascades exist in many autoimmune disorders which amplify and sustain the autoimmune process and lead to chronic inflammatory injury to the host tissues. Increasing evidence indicates that chondrocytes can interact with T cells, which may be a crucial event in inflammatory arthritis. To address the reciprocal influences of cartilage-reactive T cells and chondrocytes, we constructed cartilage-reactive T cells by developing a type II collagen-specific chimeric antigen receptor (CII-CAR). An in vitro co-culture model of CII-CAR-T cells and fresh cartilage was developed, in which CII-CAR-T displayed specific proliferative capacity and cytokine release against fresh cartilage samples, and chondrocytes could respond to CII-CAR-T cells by secreting IL-6. The proposed model will help us to explore the possible cytokine cascades between cartilage-reactive T cells and cartilage.

Synthesis of an Array of Triple-Helical Peptides from Type II Collagen for Multiplex Analysis of Autoantibodies in Rheumatoid Arthritis.

Type II collagen (CII) is the most abundant protein in joint cartilage. Antibodies to CII appear around the clinical onset of the autoimmune disease rheumatoid arthritis (RA) in a subset of patients. They target specific epitopes on CII and can be pathogenic or protective. Assays for early detection of such autoantibodies may provide new opportunities for selecting effective treatment strategies of RA. We report the efficient and reproducible assembly of an array of covalently branched native and citrullinated triple helical peptides (THPs) from CII that contain defined autoantibody epitopes. Both monoclonal antibodies and sera from experimental mouse models show a unique reactivity toward the THPs, compared to cyclic peptides containing the epitopes, revealing the importance that the epitopes are displayed in a triple-helical conformation. Importantly, antibodies against three of the THPs that contain major CII epitopes were found to be increased in sera from patients with RA, compared to control persons. These results indicate that such synthetic THPs should be included in multiplex analysis of autoantibodies that are uniquely occurring in individuals with early RA, to provide valuable information on disease prognosis and on what type of therapy should be chosen for individual patients.

Comparative study between human mesenchymal stem cells and etanercept as immunomodulatory agents in rat model of rheumatoid arthritis.

To compare human adipose tissue mesenchymal stem cells (AT-MSCs) and etanercept as immunomodulatory agents for collagen-induced arthritis (CIA). CIA was induced by rats' immunization with collagen type II (CII) in complete Freund's adjuvant in days 0 and 7. Before the onset of CIA, prevention group received five doses of AT-MSCS intraperitoneally. After establishment of arthritis, rats received either five doses of AT-MSCs or phosphate-buffered saline (PBS) intraperitoneally or six doses of etanercept subcutaneously. Clinical and histopathological evaluation were performed in all groups; serum levels of tumor necrosis factor-α (TNF-α), interleukin-10 (IL-10), and anti-collagen II were assessed by enzyme-linked immunosorbent assay (ELISA). A total percent of autoreactive T and regulatory T (Treg) cells were quantified using spleen immune histochemical analysis. AT-MSCs were able to delay the onset of CIA, suppress the ongoing clinical and histopathological signs, decrease serum levels of TNF-α and anti-collagen type II, and downregulate the autoreactive T cells as etanercept. AT-MSCs were more potent in Treg cells upregulation, producing high serum levels of IL10. AT-MSCs might have a therapeutic effect in CIA via their potency in immune cell education, representing an effective new promising approach in rheumatoid arthritis in human.

Mouse CD163 deficiency strongly enhances experimental collagen-induced arthritis.

The scavenger receptor CD163 is highly expressed in macrophages in sites of chronic inflammation where it has a not yet defined role. Here we have investigated development of collagen-induced arthritis (CIA) and collagen antibody-induced arthritis (CAIA) in CD163-deficient C57BL/6 mice. Compared to wild-type mice, the CIA in CD163-deficient mice had a several-fold higher arthritis score with early onset, prolonged disease and strongly enhanced progression. Further, the serum anti-collagen antibody isotypes as well as the cytokine profiles and T cell markers in the inflamed joints revealed that CD163-deficient mice after 52 days had a predominant Th2 response in opposition to a predominant Th1 response in CD163+/+ mice. Less difference in disease severity between the CD163+/+ and CD163-/- mice was seen in the CAIA model that to a large extent induces arthritis independently of T-cell response and endogenous Th1/Th2 balance. In conclusion, the present set of data points on a novel strong anti-inflammatory role of CD163.

Deficiency of STING Promotes Collagen-Specific Antibody Production and B Cell Survival in Collagen-Induced Arthritis.

The levels of interferon-alpha are high in the serum and synovial fluid of rheumatoid arthritis (RA) patients. Activation of the stimulator of type I interferon genes (STING) mediates the productions of type I interferon and promotes chronic inflammation. STING plays a significant role in autoimmune lupus mice. However, the function of STING in collagen-induced arthritis (CIA) model has never been described. This study aimed to test the function of STING in CIA. The Sting-deficient mice developed arthritis comparable to WT mice. The levels of anti-collagen antibody from Sting-deficient mice were significantly higher than the WT mice. The B cells derived from Sting-deficient mice showed better survival than WT mice in response to the B cell receptor (BCR) stimulation. Activation of STING also induced B cell death, especially in activated B cells. This study demonstrated that the inhibition of STING promotes anti-collagen antibodies and B cell survival, which suggested that STING acts as a negative regulator of B cell function in the CIA model.

Attenuation of Murine Collagen-Induced Arthritis by Targeting CD6.

OBJECTIVE: CD6 is an important regulator of T cell function that interacts with the ligands CD166 and CD318. To further clarify the significance of CD6 in rheumatoid arthritis (RA), we examined the effects of targeting CD6 in the mouse model of collagen-induced arthritis (CIA), using CD6-knockout (CD6-KO) mice and CD6-humanized mice that express human CD6 in lieu of mouse CD6 on their T cells. METHODS: We immunized wild-type (WT) and CD6 gene-KO mice with a collagen emulsion to induce CIA. For treatment studies using CD6-humanized mice, mice were immunized similarly and a mouse anti-human CD6 IgG (UMCD6) or control IgG was injected on days 7, 14, and 21. Joint tissues were evaluated for tissue damage, leukocyte infiltration, and local inflammatory cytokine production. Collagen-specific Th1, Th9, and Th17 responses and serum levels of collagen-specific IgG subclasses were also evaluated in WT and CD6-KO mice with CIA. RESULTS: The absence of CD6 reduced 1) collagen-specific Th9 and Th17, but not Th1 responses, 2) the levels of many proinflammatory joint cytokines, and 3) serum levels of collagen-reactive total IgG and IgG1, but not IgG2a and IgG3. Joint homogenate hemoglobin content was significantly reduced in CD6-KO mice with CIA compared to WT mice with CIA (P < 0.05) (reduced angiogenesis). Moreover, treating CD6-humanized mice with mouse anti-human CD6 monoclonal antibody was similarly effective in reducing joint inflammation in CIA. CONCLUSION: Taken together, these data suggest that interaction of CD6 with its ligands is important for the perpetuation of CIA and other inflammatory arthritides that are T cell driven.

Immunoglobulin A antibodies to oxidized collagen type II as a potential biomarker for the stratification of spondyloarthritis from rheumatoid arthritis.

OBJECTIVES: The discovery of diseased tissue-specific neoantigens offers the opportunity to develop important disease tissue-specific biomarkers that can help in the prediction, diagnosis, and stratification of diseases. This opportunity is specifically significant for autoimmune diseases where diagnostic biomarkers are not available. Inflammatory autoimmune diseases are commonly associated with local generation of large amounts of reactive oxidants. We have previously identified oxidative post-translationally modified (oxPTM) tissue-specific neoantigens in rheumatoid arthritis (RA) and type 1 diabetes that elicit an immune response. In the current study, we studied the presence and clinical significance of antibodies to oxPTM collagen type II (CII) in patients with spondyloarthritis (SpA). METHOD: Levels of antibodies specific to native CII and oxPTM-CII were assessed by enzyme-linked immunosorbent assay. RESULTS: Immunoglobulin G (IgG) binding to oxPTM-CII was observed in 52%, 83%, and 28% of serum samples from patients with axial spondyloarthritis (axSpA), RA, and psoriatic arthritis (PsA), respectively. Importantly, while strong IgA anti-oxPTM-CII responses were detected in axSpA and PsA patients, with 47% and 84% respective binders, no IgA anti-oxPTM-CII was detected in RA patients. IgA anti-oxPTM-CII reactivity in axSpA patients treated with biologics was higher and more frequent, with 85% binders compared to 9% binders in patients treated with synthetic disease-modifying anti-rheumatic drugs. CONCLUSION: Our data imply that SpA and PsA are associated with the presence of antibodies to oxPTM-CII, suggesting that there may be a humoral component that may distinguish patients with SpA from RA. Our approach could be adapted to other diseases, particularly to inflammatory autoimmune diseases.

The impact of Clonorchis sinensis infection on immune response in mice with type II collagen-induced arthritis.

BACKGROUND: Clonorchis sinensis infection could trigger strong immune responses in mice and humans. However, whether the C.sinensis infection has an impact on arthritis is unknown. Here we investigated the effect of C.sinensis infection on type II collagen-induced arthritis in BALB/c mice. RESULTS: The mice were firstly infected with 45 C.sinensis metacercariae by oral gavage. Four weeks later, arthritis in mice was induced by type II collagen. Joint inflammation with severe redness and swelling in hind paws was observed in type II collagen-induced arthritis (CIA) mice. Besides, the physical activity was significantly reduced, but the respiratory exchange ratio was increased in CIA mice. Compared with CIA mice, C.sinensis infection could increase the severity of arthritis in CIA mice, based on the results of disease score and pathological changes. Compared to CIA mice, increased neutrophils and Ly6Chi monocytes, decreased B cells and CD4+T cells, were found in C.sinensis infected CIA mice. Besides these, C.sinensis infected mice also displayed significantly higher levels of serum IL-4 and IL-17 than those in CIA mice. CONCLUSIONS: Taken together, our data suggest that C.sinensis infection have a bad effect on arthritis, and could induce the abnormality of the immune response in mice with CIA.

Sex differences in Tfh cell help to B cells contribute to sexual dimorphism in severity of rat collagen-induced arthritis.

The study examined germinal centre (GC) reaction in lymph nodes draining inflamed joints and adjacent tissues (dLNs) in male and female Dark Agouti rat collagen type II (CII)-induced arthritis (CIA) model of rheumatoid arthritis. Female rats exhibiting the greater susceptibility to CIA mounted stronger serum CII-specific IgG response than their male counterparts. This correlated with the higher frequency of GC B cells in female compared with male dLNs. Consistently, the frequency of activated/proliferating Ki-67+ cells among dLN B cells was higher in females than in males. This correlated with the shift in dLN T follicular regulatory (Tfr)/T follicular helper (Tfh) cell ratio towards Tfh cells in females, and greater densities of CD40L and CD40 on their dLN T and B cells, respectively. The higher Tfh cell frequency in females was consistent with the greater dLN expression of mRNA for IL-21/27, the key cytokines involved in Tfh cell generation and their help to B cells. Additionally, in CII-stimulated female rat dLN cell cultures IFN-γ/IL-4 production ratio was shifted towards IFN-γ. Consistently, the serum IgG2a(b)/IgG1 CII-specific antibody ratio was shifted towards an IgG2a(b) response in females. Thus, targeting T-/B-cell interactions should be considered in putative further sex-based translational pharmacology research.

Lipid accumulation and mitochondrial abnormalities are associated with fiber atrophy in the skeletal muscle of rats with collagen-induced arthritis.

Rheumatoid arthritis (RA) has a negative impact on muscle mass, and reduces patient's mobility and autonomy. Furthermore, RA is associated with metabolic comorbidities, notably in lipid homeostasis by unknown mechanisms. To understand the links between the loss in muscle mass and the metabolic abnormalities, arthritis was induced in male Sprague Dawley rats (n = 11) using the collagen-induced arthritis model. Rats immunized with bovine type II collagen were compared to a control group of animals (n = 11) injected with acetic acid and complete Freund's adjuvant. The clinical severity of the ensuing arthritis was evaluated weekly by a semi-quantitative score. Skeletal muscles from the hind limb were used for the histological analysis and exploration of mitochondrial activity, lipid accumulation, metabolism and regenerative capacities. A significant atrophy in tibialis anterior muscle fibers was observed in the arthritic rats despite a non-significant decrease in the weight of the muscles. Despite moderate inflammation, accumulation of triglycerides (P < 0.05), reduced mitochondrial DNA copy number (P < 0.05) and non-significant dysfunction in mitochondrial cytochrome c oxidase activity were found in the gastrocnemius muscle. Concomitantly, our results suggested an activation of the muscle specific E3 ubiquitin ligases MuRF-1 and MAFbx. Finally, the adipose tissue from the arthritic rats exhibited decreased PPARγ mRNA suggesting reduced adipogenic capacities. In conclusion, the reduced adipose tissue adipogenic capacity and skeletal muscle mitochondrial capacity are probably involved in the activation of protein catabolism, inhibition of myogenesis, accumulation of lipids and fiber atrophy in the skeletal muscle during RA.