Vegfb gene knockout mice display reduced pathology and synovial angiogenesis in both antigen-induced and collagen-induced models of arthritis

OBJECTIVE: To determine the role of vascular endothelial growth factor B (VEGF-B) in 2 mouse models of arthritis, antigen-induced arthritis (AIA) and collagen-induced arthritis (CIA). METHODS: For AIA studies, monarticular AIA was induced by methylated bovine serum albumin (mBSA) priming of Vegfb gene knockout (Vegfb(-/-)) and wild-type (Vegfb(+/+)) mice, followed by intraarticular injection of mBSA or saline control 8 days later. CIA was induced in Vegfb(-/-) and Vegfb(+/+) mice by intradermal injection of chick type II collagen in adjuvant. Arthritis was monitored in both models using defined criteria (clinical and histologic). Angiogenesis was measured by synovial vessel density in diseased and control joints. RESULTS: In AIA studies, Vegfb(+/+) mice displayed significant knee joint swelling and synovial inflammation 7 days after intraarticular injection of antigen. Synovial inflammation was associated with angiogenesis, since vessel density in AIA synovium was significantly higher in arthritic than in control joints from the same animal. Knee joint swelling, synovial inflammation, and inflammation-associated vessel density in arthritic joints were reduced in Vegfb(-/-) mice compared with arthritic joints from Vegfb(+/+) mice. Similarly, in CIA, both disease incidence and mean clinical severity scores were significantly reduced in Vegfb(-/-) mice compared with Vegfb(+/+) mice. Mean histologic severity scores and mean synovial vessel density were reduced in diseased joints from Vegfb(-/-) mice when compared with diseased joints from Vegfb(+/+) mice. CONCLUSION: The reduction in inflammation-associated synovial angiogenesis in Vegfb(-/-) mice implicates VEGF-B in pathologic vascular remodeling in inflammatory arthritis. VEGF-B may be an attractive target in the design of anti-angiogenic therapies for rheumatoid arthritis.     

Protective effects of plasmin(ogen) in a mouse model of Staphylococcus aureus-induced arthritis

OBJECTIVE: To assess the functional roles of plasmin in a murine model of Staphylococcus aureus-induced bacterial arthritis. METHODS: Bacterial arthritis was induced in plasminogen-deficient (Plg(-/-)) and wild-type (Plg(+/+)) littermates by local injection of 1 x 10(6) colony-forming units of S aureus into the knee joints. Human plasminogen was administered to Plg(-/-) mice on days 0-7 or days 7-14. Antibiotic treatment was administered to Plg(-/-) mice on days 7-14. Bacteria counts and histologic, immunohistochemical, and Western blot analyses were performed. RESULTS: In Plg(+/+) mice, S aureus counts had declined within 2 days, and by day 28 the bacteria had been completely eliminated. However, S aureus was still detectable in all injected joints from Plg(-/-) mice, and bacteria counts were 27 times higher than the amount injected on day 0. The extent of macrophage and neutrophil recruitment to the infected joints was comparable for Plg(+/+) and Plg(-/-) mice on days 1, 7, and 14. The activation of these inflammatory cells appeared to be impaired in Plg(-/-) mice, however. Treatment of Plg(-/-) mice with antibiotic (cloxacillin) resulted in successful killing of the bacteria, but the necrotic tissue remained in the infected joints. When human plasminogen was given intravenously to Plg(-/-) mice daily for 7 days, bacterial clearance was greatly improved as compared with their untreated counterparts, and the amount of necrotic tissue in the joint cavity was dramatically reduced. The expression of interleukin 6 (IL-6) and IL-10 was higher in Plg(+/+) mice than in Plg(-/-) mice during bacterial arthritis. CONCLUSION: Our findings indicate that plasmin plays a pluripotent role in protecting against S aureus-induced arthritis by activating inflammatory cells, killing bacteria, removing necrotic tissue, and enhancing cytokine expression.     

Plasminogen activator inhibitor type-1 deficiency attenuates murine antigen-induced arthritis

OBJECTIVE: To examine the role of plasminogen activator inhibitor type-1 (PAI-1), the major fibrinolytic inhibitor, in vivo during murine antigen-induced arthritis (AIA). METHODS: AIA was induced in PAI-1-deficient mice and control wild-type mice. Arthritis severity was evaluated by technetium 99m (99mTc) uptake in the knee joints and by histological scoring. Intra-articular fibrin deposition was examined by immunohistochemistry and synovial fibrinolysis quantitated by tissue D-dimer measurements and zymograms. RESULTS: Joint inflammation, quantitated by 99mTc uptake, was significantly reduced in PAI-1(-/-) mice on day 7 after arthritis onset (P<0.01). Likewise, synovial inflammation, evaluated by histological scoring, was significantly decreased in PAI-1-deficient mice on day 10 after arthritis onset (P<0.001). Articular cartilage damage was significantly decreased in PAI-1(-/-) mice, as shown by histological grading of safranin-O staining on day 10 after arthritis onset (P<0.005). Significantly decreased synovial accumulation of fibrin was observed by day 10 in arthritic joints of PAI-1(-/-) mice (P<0.005). Accordingly, the synovial tissue content of D-dimers, the specific fibrin degradation products generated by plasmin, were increased in PAI-1(-/-) mice (P<0.02). Finally, as expected, PA activity was increased in synovial tissues from PAI-1(-/-) mice, as shown by zymographic analysis. CONCLUSIONS: These results indicate that deficiency of PAI-1 results in increased synovial fibrinolysis, leading to reduced fibrin accumulation in arthritic joints and reduced severity of AIA.     

Unmethylated oligo-DNA containing CpG motifs aggravates collagen-induced arthritis in mice

OBJECTIVE: To investigate the effects of an intradermal injection of an unmethylated oligodeoxynucleotide (ODN) containing CpG motifs on the severity of collagen-induced arthritis (CIA). METHODS: CIA was induced in DBA/1 LacJ mice by immunization with bovine type II collagen (CII) in Freund's complete adjuvant followed 3 weeks later by immunization with CII in Freund's incomplete adjuvant (yielding CIA mice). Unmethylated ODN containing a CpG motif was injected intradermally into DBA/1 LacJ mice at a dosage of 20 microg (yielding CpG-CIA mice) 1 week prior to the first immunization with CII. Unmethylated ODN containing a GpC motif instead of a CpG motif and ODN containing a methylated CpG motif were used to produce controls (GpC-CIA mice and mCpG-CIA mice, respectively). After the second immunization with CII, arthritis scores were measured weekly up to the eighth week. At the eighth week, the mice were killed, histopathologic changes in the ankle joints were examined, and titers of interferon-gamma (IFNgamma) in the supernatants of splenocytes (1 x 10(7)) stimulated in culture by CII for 3 days were determined by enzyme-linked immunosorbent assay. RESULTS: CpG-CIA mice had significantly higher arthritis scores than CIA mice. CpG-CIA mice had more severe histopathologic changes than CIA mice and mCpG-CIA mice. Moreover, splenocytes in CpG-CIA mice produced higher IFNgamma titers in response to CII than did splenocytes in CIA mice and mCpG-CIA mice. CONCLUSION: Injection of unmethylated oligo-DNA containing CpG motifs aggravated CIA through activation of the Th1-type immune response, suggesting that microbial infection could be one of the mechanisms for aggravation or exacerbation of arthritis or, alternatively, that such infection could be an adjuvant in the induction of arthritis in rheumatoid arthritis.     

IFNgamma deficient C57BL/6 (H-2b) mice develop collagen induced arthritis with predominant usage of T cell receptor Vbeta6 and Vbeta8 in arthritic joints

BACKGROUND: Transgenic deficiency in interferon gamma (IFNgamma) or IFNgamma receptor makes resistant strains of mice bearing H-2(b) or H-2(d) susceptible to collagen induced arthritis (CIA). OBJECTIVE: To determine whether the escape from regulation of disease susceptibility at the major histocompatibility complex level involves a new use of autoimmune T cells expressing T cell receptor (TCR) Vbeta that vary from the cell populations previously identified within arthritic joints. METHODS: Arthritis was induced by a standard protocol with type II bovine collagen (CII) in complete Freund's adjuvant. Clinical features, histopathology, immunological responses, and TCR profile in arthritic joints in IFNgamma knockout C57BL/6 (B6.IFNgamma KO) mice (H-2(b)) were compared directly with those in DBA/1 mice (H-2(q)). RESULTS: 60-80% of B6.IFNgamma KO mice developed a progressive arthritis with a similar clinical course to classical CIA in DBA/1 mice. The affected joints in B6.IFNgamma KO mice had an erosive form of arthritis with similar features to joint disease in DBA/1 mice. B6.IFNgamma KO mice produced significantly higher levels of IgG2b and IgG1 autoantibodies to murine CII and showed increased proliferative response to CII compared with B6 mice. Comparable levels of interleukin 1beta and tumour necrosis factor alpha expression were detected in arthritic joints from beta6.IFNgamma KO and DBA/1 mice. B6.IFNgammaKO mice used predominantly TCR Vbeta6 and Vbeta8 in arthritic joints. This TCR Vbeta profile is similar to that found in DBA/1 mice with CIA. CONCLUSIONS: C57BL/6 mice deficient in IFNgamma production can develop arthritis that resembles classical CIA. These data suggest that IFNgamma is a key factor mediating susceptibility to CIA.     

Total abrogation of collagen II-induced arthritis and the B cell response to type II collagen using suboptimal doses of a topoisomerase II antagonist

BACKGROUND: Collagen-induced arthritis (CIA) is the most commonly used model of rheumatoid arthritis (RA). In both CIA and RA there is an increase in the cellular content of the synovium, this being dominated by macrophages. OBJECTIVE: To assess the impact of etoposide, a topoisomerase II antagonist known to induce monocyte apoptosis, on the development of CIA. METHODS: Mice were primed and booster immunised against collagen II (CII). One group of mice was treated with etoposide two days before CII immunisation and then on four consecutive days weekly until the end of the experiment. The second group of mice was injected with etoposide on four consecutive days a week starting 40 days after CII priming. The third group of mice were controls receiving phosphate buffered saline (PBS). The mice were examined for development of arthritis, numbers of circulating leucocytes, serum CII antibody, and cytokine concentrations. RESULTS: None of the mice given etoposide before CII immunisation developed arthritis. Serum concentrations of anti-CII antibodies were undetectable in these mice, whereas they displayed significantly increased concentrations of interferon gamma and interleukin 6. In addition, the CII specific B cell responses in the draining lymph nodes were highly suppressed. Also, mice treated with etoposide at the onset of clinical arthritis showed reduced frequency of their disease by 50%. CONCLUSION: There was a striking disease alleviating impact of topoisomerase II antagonist on the course of CII-induced arthritis.     

Germinal center reaction in the joints of mice with collagen-induced arthritis: an animal model of lymphocyte activation and differentiation in arthritis joints.

OBJECTIVE: To establish an animal model and provide a basis for investigating the role of germinal center (GC) reaction in autoimmune arthritis. METHODS: DBA/1 mice were immunized with bovine type II collagen (CII) to elicit collagen-induced arthritis (CIA). Sections of arthritic joints were examined by in situ immunohistochemical studies, and purified cells from affected joints were subjected to flow cytometry analysis. RESULTS: De novo GC reaction was induced in the arthritic joints of male DBA/1 mice by immunization with bovine CII. In comparison with GCs formed in lymphoid tissues, such as spleen and lymph nodes, we found that these GCs formed in the joint tissues of mice with CIA were morphologically typical, as determined by immunohistologic and flow cytometric assays. CONCLUSION: The local immune responses in murine CIA induced ectopic GC formation, as observed in the synovial tissues of patients with rheumatoid arthritis. This system will allow for the first time the direct study of the role of the GC reaction in autoimmune arthritis in an animal model.     

The genetic ablation of cyclooxygenase 2 prevents the development of autoimmune arthritis

OBJECTIVE: To determine the effects of cyclooxygenase 1 (COX-1) and COX-2 gene deletion on collagen-induced arthritis (CIA). METHODS: Mice that were susceptible to CIA but lacked either the COX-1 or the COX-2 gene were immunized with type II collagen (CII), and the incidence and severity of arthritis were compared with findings in wild-type animals, by clinical and histologic examination. The immune response was assessed by measuring total CII IgG, IgG1, and IgG2 antibody production in sera from immunized mice. The passive transfer of arthritis, accomplished using anti-CII monoclonal antibodies, was tested in wild-type and COX-deficient (-/-) mice. Splenocytes cultured from CII-immunized wild-type and COX-/- mice were challenged with bovine alpha1(II), and cytokine production was assessed. RESULTS: COX-2 gene deletion reduced the incidence and severity of CIA compared with findings in wild-type and COX-1-/- mice. Histologic examination of joints after the onset of clinical arthritis revealed cartilage erosions, proliferation of the synovial lining, and inflammatory cell infiltration in wild-type and COX-1-/- mice, but not in COX-2-/- mice. COX-2-/- mice exhibited reduced anti-CII IgG antibody levels, indicating a decreased immune response. However, cytokine production by spleen cells from immunized mice indicated no cytokine deficiencies in COX-2-/- mice compared with wild-type or COX-1-/- mice. More important, arthritis could not be passively transferred to naive COX-2-/- mice, indicating a requirement for COX-2 in the pathogenesis of arthritis, independent of the immune response. CONCLUSION: COX-2-/- mice exhibit at least 2 defects resulting in down-modulation of the development of CIA: a reduced immune response to CII demonstrated by a markedly reduced antibody titer, and an "inflammatory" defect reflected by the inability to passively transfer arthritis to COX-2-/- mice.     

Staphylococcal enterotoxin B increases the severity of type II collagen induced arthritis in mice.

OBJECTIVE--To observe the influence of T cell subset changes on the development of experimental arthritis, by using the bacterial superantigen staphylococcal enterotoxin B (SEB) to modulate the T cell repertoire during the arthritogenic response to type II collagen (CII) in vivo. METHODS--DBA/1 mice were injected with SEB before immunisation with CII, and assessed for the development of collagen induced arthritis (CIA) and an immune response to CII. Mice with established arthritis were also treated therapeutically with SEB. Flow cytometry was used to evaluate the effect of the therapy on T cell subsets and T cell receptor (TCR) V beta expression. RESULTS--Mice injected with SEB developed arthritis significantly faster than saline treated control animals, and developed more severe clinical features. Mice treated with SEB after the onset of CIA were also observed to progress more rapidly to a severe arthritis than mice treated with saline alone. The level of anti-CII antibody was not affected by SEB injection. Flow cytometric analysis of TCR expression in mice 21 days after injection of CII showed decreased expression of V beta 6 and V beta 8 cells in SEB treated mice, compared with collagen immunised control mice. Injection of SEB alone caused a decrease in V beta 8, but not V beta 6 T cells compared with the values in normal DBA/1 mice. No significant variations in the T cell repertoire were detected 70 days after CII immunisation. CONCLUSIONS--Treatment with the bacterial enterotoxin SEB before the induction of arthritis did not suppress the immunological or arthritogenic response to CII in DBA/1 mice, despite the modulation of the V beta 8 T cell subset. Treatment of mice with established arthritis using SEB provoked a more severe disease course.     

CXCR5- and CCR7-dependent lymphoid neogenesis in a murine model of chronic antigen-induced arthritis

OBJECTIVE: Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease with unknown etiology and only partially defined pathogenesis. The aim of this study was to establish a murine model of chronic arthritis in which the development of tertiary lymphoid tissue, a hallmark of human RA, is locally induced, and to characterize the roles of the homeostatic chemokine receptors CXCR5 and CCR7 in this process. METHODS: We developed a modified model of chronic antigen-induced arthritis (AIA) in mice with a strong bias toward inflammation. Disease pathology was assessed up to 9 months in wild-type, CXCR5-deficient, and CCR7-deficient mice by determination of knee joint swelling and cellular and humoral immune responses, as well as by histologic analysis of arthritic knee joints. RESULTS: In this novel model of AIA, mice developed organized ectopic lymphoid follicles with topologically segregated B cell and T cell areas, high endothelial venules, and germinal center formation within the chronically inflamed synovial tissue. Analysis of the initiation and progression of AIA in wild-type, CXCR5-/-, and CCR7-/- mice revealed a reduction of acute inflammatory parameters in both knockout strains as well as significantly reduced joint destruction in CXCR5-/- mice. Most importantly, the development and organization of tertiary lymphoid tissue were significantly impaired in CXCR5-deficient and CCR7-deficient mice. CONCLUSION: Our results suggest that an inflammatory microenvironment efficiently triggers lymphoid neogenesis in autoimmune diseases such as RA. Moreover, the generation of autoreactive tertiary lymphoid tissues, which is entirely dependent on homeostatic chemokines, may in turn maintain local aberrant chronic immune responses.     

Angiostatin gene transfer as an effective treatment strategy in murine collagen-induced arthritis

OBJECTIVE: To determine the efficacy of local therapy with human angiostatin gene in murine collagen-induced arthritis (CIA). METHODS: DBA/1 mice were immunized with bovine type II collagen. Before the onset of arthritis, NIH3T3 fibroblasts, transduced with angiostatin-expressing retroviral vectors or control vectors, were transplanted into the knee cavity. The incidence of arthritis in the knee joints was evaluated histologically based on pannus formation and cartilage destruction. Paws were evaluated macroscopically for redness, swelling, and deformities and immunologically for levels of interleukin-1 beta. Angiogenesis in paws and knee joints was studied by immunohistochemistry using anti-CD31 antibody and measurement of von Willebrand factor levels. RESULTS: Pannus formation and cartilage erosion were dramatically reduced in knees transplanted with angiostatin-expressing cells. In addition, the onset of CIA in the ipsilateral paws below the knees injected with the angiostatin gene was significantly prevented. Furthermore, angiostatin gene transfer inhibited arthritis-associated angiogenesis. CONCLUSION: Local production of angiostatin in the knee was able to prevent the onset of CIA not only in the knee injected with genetically engineered cells, but also in the uninjected ipsilateral paw. This suggests that transfer of the angiostatin gene, and potentially also its protein, may provide a new, effective approach to the treatment of rheumatoid arthritis.     

Acceleration of the onset of collagen-induced arthritis by a deficiency of platelet endothelial cell adhesion molecule 1

OBJECTIVE: Platelet endothelial cell adhesion molecule 1 (PECAM-1; CD31) is a member of the immunoglobulin superfamily that is expressed in platelets, leukocytes, and endothelial cells. PECAM-1 has been shown to play a role in transendothelial migration of leukocytes and contains immunoreceptor tyrosine-based inhibitory motifs in its cytoplasmic tail and inhibits cellular responses. We examined the role of PECAM-1 in the development of collagen-induced arthritis (CIA). METHODS: CIA was induced in PECAM-1-deficient DBA/1 mice. The incidence of arthritis and the arthritis index were examined. Anti-type II collagen (anti-CII) antibody levels and interferon-gamma (IFNgamma) production by lymph node cells and spleen cells were determined. Lymphocytes from arthritic PECAM-1-deficient and wild-type mice were labeled with dye, transferred to arthritic PECAM-1(+/-) mice, and cell migration to inflamed joints was examined. RESULTS: PECAM-1-deficient mice showed accelerated onset of arthritis and increased severity only during the early phase. Anti-CII antibody levels were also increased during the early phase. IFNgamma production by lymph node cells and spleen cells from PECAM-1-deficient mice in response to CII was higher than that in wild-type mice. Lymphocytes from arthritic PECAM-1-deficient mice showed accelerated migration to inflamed joints, but not lymph nodes or spleen. The development of anti-CII antibody-induced arthritis was similar in PECAM-1-deficient and wild-type mice. CONCLUSION: These results indicate that PECAM-1 negatively regulates humoral and cell-mediated immune responses and lymphocyte migration into joints and, consequently, the development of CIA. In addition, the role of PECAM-1 in the transendothelial migration of leukocytes appears to be redundant in this model.     

Reduced susceptibility to collagen-induced arthritis in DBA/1J mice expressing the TSG-6 transgene

OBJECTIVE: Expression of TSG-6 (tumor necrosis factor-stimulated gene 6) is induced by proinflammatory cytokines. This study was undertaken to examine the effects of local expression of TSG-6 in arthritic joints of TSG-6 transgenic mice, in the collagen-induced arthritis (CIA) model. METHODS: We generated transgenic mice that harbored the TSG-6 gene under the control of the T cell-specific lck promoter. Arthritis was induced by immunization with bovine type II collagen (CII), and its progression was monitored based on the incidence of arthritis, the arthritis index, and footpad swelling. Anti-CII antibodies and cytokine production were determined by enzyme-linked immunosorbent assay. Gene expression arrays were used to compare gene expression profiles of transgenic and control mice at various stages of CIA. RESULTS: TSG-6 was expressed in limbs of transgenic mice after immunization with CII, while its expression in nontransgenic animals was insignificant. The incidence of CIA was reduced in TSG-6 transgenic animals, its onset delayed, and all parameters of clinical arthritis significantly reduced. However, the immune response against CII was not significantly inhibited in TSG-6 transgenic mice. CONCLUSION: TSG-6 expression has been demonstrated in patients with rheumatoid and other forms of arthritis. Our data show that local expression of TSG-6 at sites of inflammation results in potent inhibition of inflammation and joint destruction in a model of autoimmune arthritis in mice. Therefore, it is likely that TSG-6 plays a similar modulatory role in human rheumatoid arthritis and related diseases and may have potential for the treatment of autoimmune arthritis in humans.     

Blockade of lymphotoxin pathway exacerbates autoimmune arthritis by enhancing the Th1 response

OBJECTIVE: To study the role of the lymphotoxin (LT) signaling pathway in the development and pathogenesis of collagen-induced arthritis (CIA), and to understand the mechanisms by which blockade of the LT pathway influences the arthritogenic response to type II collagen (CII). METHODS: LTalpha-deficient and wild-type C57BL/6 mice were immunized with CII. Male DBA/1 mice were immunized with CII and treated with LTbeta receptor immunoglobulin fusion protein (LTbetaR-Ig) or control Ig. Mice were monitored for the development and severity of arthritis. The effects of LT blockade on immune responses were evaluated by cytokine production and antigen-specific proliferation in vitro, the delayed-type hypersensitivity (DTH) response, and serum levels of CII-specific antibodies. RESULTS: CIA that developed in LTalpha-deficient mice was more severe and prolonged than that which developed in wild-type mice. Blocking LT signaling with LTbetaR-Ig significantly exacerbated the disease. Exacerbation of CIA was associated with an enhanced Th1-type response, including increased type 1 cytokine production, an enhanced DTH response, and elevated production of CII-specific IgG2a antibodies. CONCLUSION: Blockade of the LT signaling pathway exacerbates the development and progression of CIA, probably by skewing the Th1/Th2 balance that determines the outcome of autoimmune responses.     

Increased resistance to collagen-induced arthritis in CD44-deficient DBA/1 mice.

OBJECTIVE: To study the role of CD44, the principal hyaluronan (HA) receptor, in experimental arthritis. METHODS: We generated CD44 gene deficiency in arthritis-susceptible DBA/1LacJ mice to study the role of CD44 directly in collagen-induced arthritis (CIA). Wild-type and CD44-deficient mice were immunized with chicken type II collagen, and the onset and severity of CIA were monitored up to day 64. The immune status of immunized mice was determined at the end of the experiments. Cell transfer experiments were performed to monitor lymphocyte traffic to the inflamed joints. RESULTS: Mice homozygous for the CD44 mutation developed normally and showed no phenotypic defects. Although they showed a normal response to immunization with type II collagen and had Th1/Th2 ratios comparable with those in wild-type animals, CD44-deficient mice exhibited significant reductions in both the incidence and severity of CIA. This was accompanied by altered serum levels of HA, reduced expression of L-selectin, and a delayed entry of intravenously injected CD44-deficient donor lymphocytes into the arthritic joints of recipient mice. CONCLUSION: While CD44 is not essential for morphogenesis and autoimmunity, this cell surface receptor seems to play an important role in the development of arthritis, most likely by directing leukocyte traffic to the site of inflammation.     

123I-antileukoproteinase scintigraphy reveals microscopic cartilage alterations in the contralateral knee joint of rats with "monarticular" antigen-induced arthritis

OBJECTIVE: To assess the involvement of the contralateral knee joint in monarticular antigen-induced arthritis (AIA) by scintigraphy with the cationic (pI >10), 123I-labeled, serine proteinase inhibitor antileukoproteinase (123I-ALP) and to compare the scintigraphic findings with those of radiography and high-resolution ex vivo magnetic resonance imaging (MRI). METHODS: Lewis rats with chronic AIA were examined 2.5 months following arthritis induction (injection of 500 microg of methylated bovine serum albumin/saline into the ipsilateral [arthritic] knee joint and injection of phosphate buffered saline into the contralateral knee joint following systemic immunization). 123I-ALP was injected intravenously into normal rats (n = 4) or rats with AIA (n = 6). The ipsilateral and contralateral knee joints and both ankles were examined by scintigraphy and radiography. Joint cartilage was examined by high-resolution ex vivo MRI, histopathology, and measurement of tissue radioactivity. RESULTS: ALP accumulation (typically observed in normal articular cartilage) was lost in both the ipsilateral and the contralateral knee joints, but not in the clinically unaffected ankles of rats with AIA. In both knee joints, 123I-ALP target:background ratios and cartilage radioactivity correlated negatively with the loss of toluidine blue staining in cartilage, which documents the depletion of charged matrix molecules. Findings of histopathology confirmed mild alterations in the ipsilateral knee joint and even milder alterations in the contralateral knee joint, while the ankles were normal. Radiography and high-resolution ex vivo MRI failed to detect abnormalities in the contralateral knee joint. CONCLUSION: Loss of ALP accumulation appears to document proteoglycan depletion, even in the microscopically altered cartilage of the contralateral knee joint in AIA. These findings underscore the high sensitivity of 123I-ALP for in vivo detection of biochemical cartilage alterations in arthritis, and furthermore, question the use of the contralateral knee joint as a normal control in AIA.     

The involvement of V(alpha)14 natural killer T cells in the pathogenesis of arthritis in murine models

OBJECTIVE: To examine the physiologic role of natural killer T (NKT) cells bearing V(alpha)14 T cell receptor (TCR) in the pathogenesis of collagen-induced arthritis (CIA) and antibody-induced arthritis in mice. METHODS: NKT cells were stained with alpha-galactosylceramide-loaded CD1 dimer, and then assessed using flow cytometry. CIA was induced in mice by immunization on days 0 and 21 with type II collagen (CII) emulsified with an equal volume of Freund's complete adjuvant. Anti-CII antibodies were measured by enzyme-linked immunosorbent assay. For antibody-induced arthritis, mice were injected with anti-CII monoclonal antibodies (mAb) followed by lipopolysaccharide, or with serum from KRN TCR-transgenic mice crossed with nonobese diabetic mice (K/BxN). The severity of arthritis was monitored with a macroscopic scoring system. RESULTS: The number of NKT cells increased in the liver at the peak of the clinical course of CIA. Administration of anti-CD1 mAb inhibited development of CIA. The severity of CIA in NKT cell-deficient mice was reduced compared with that in wild-type mice. The IgG1:IgG2a ratio of anti-CII was elevated and production of interleukin-10 from draining lymph node cells was increased in NKT cell-deficient mice. NKT cell-deficient mice were significantly less susceptible to antibody-induced arthritis. CONCLUSION: NKT cells contribute to the pathogenesis of arthritis by enhancing autoantibody-mediated inflammation. NKT cells also contribute to the disease process in a deleterious way, due, at least in part, to the alteration of the Th1/Th2 balance in T cell response to CII.     

Arthritis in mice that are deficient in interleukin-1 receptor antagonist is dependent on genetic background

OBJECTIVE: To determine the effect of deletion of interleukin-1 receptor antagonist (IL-1Ra) protein in an animal model of rheumatoid arthritis. METHODS: BALB/c mice deficient in IL-1Ra (IL-1Ra(-/-)) were bred with collagen-induced arthritis (CIA)-susceptible DBA/1 mice and B10 mice transgenic for HLA-DRB1*0101 (B10.DR1). After generation of IL-1Ra(-/-) mice on the DBA/1 and B10.DR1 backgrounds, the mice were observed for the development of spontaneous arthritis and immunized for induction of CIA. RESULTS: We found that although BALB/c mice deficient in IL-1Ra (BALB/c(-/-)) spontaneously developed chronic inflammatory arthritis, DBA/1 IL-1Ra-deficient (DBA/1(-/-)) and B10.DR1 IL-1Ra-deficient (B10.DR1(-/-)) mice did not. Splenocytes from BALB/c(-/-) mice produced elevated levels of IL-2, IL-4, IL-6, IL-10, IL-17, and granulocyte-macrophage colony-stimulating factor in response to anti-CD3 stimulation. After immunization with type II collagen (CII), DBA/1(-/-) and B10.DR1(-/-) mice had a significantly earlier onset of CIA, and with increased severity compared with IL-1Ra(+/+) mice. Immunization of BALB/c(-/-) mice with CII did not aggravate spontaneous arthritis. All of the immunized mice developed antibodies to CII that correlated with arthritis severity. Levels of antibody to CII in the BALB/c(-/-) strain were relatively low. CONCLUSION: These data indicate that the spontaneous arthritis of IL-1Ra deficiency is highly dependent on non-major histocompatibility complex genes and that autoimmunity to CII is not the major disease-inducing event. Class II immune response genes are more important for the regulation of CIA, and although these 2 models of arthritis share many pathogenic mechanisms, they also have significant differences.