Early effects of tocilizumab on bone and bone marrow lesions in a collagen-induced arthritis monkey model

Successful Treatment of SARS-CoV-2 Vaccination-related Activation of Rheumatoid Arthritis with Positive Findings for Epstein-Barr Virus

We herein report a 60-year-old woman who experienced severe flare of rheumatoid arthritis (RA) and Epstein-Barr virus (EBV) positivity following administration of the messenger ribonucleic acid (mRNA)-type severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine. Since 40 years old, she had been in long-term remission of anti-citrullinated protein antibody-positive RA. Ten days after SARS-CoV-2 vaccination, she presented with a high fever and polyarthritis, active synovitis on joint ultrasound, a clinical disease activity index of 35, and positivity for anti-early antigen, diffuse type and restricted type (EA DR) IgG and EBV deoxyribonucleic acid (EBV-DNA). Tocilizumab was introduced to treat RA. The RA disease activity disappeared, and anti-EA DR IgG and EBV-DNA became negative.

Cytokine Networks in the Pathogenesis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic systemic inflammation causing progressive joint damage that can lead to lifelong disability. The pathogenesis of RA involves a complex network of various cytokines and cells that trigger synovial cell proliferation and cause damage to both cartilage and bone. Involvement of the cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-6 is central to the pathogenesis of RA, but recent research has revealed that other cytokines such as IL-7, IL-17, IL-21, IL-23, granulocyte macrophage colony-stimulating factor (GM-CSF), IL-1β, IL-18, IL-33, and IL-2 also play a role. Clarification of RA pathology has led to the development of therapeutic agents such as biological disease-modifying anti-rheumatic drugs (DMARDs) and Janus kinase (JAK) inhibitors, and further details of the immunological background to RA are emerging. This review covers existing knowledge regarding the roles of cytokines, related immune cells and the immune system in RA, manipulation of which may offer the potential for even safer and more effective treatments in the future.

Intracellular Staphylococcus aureus in bone and joint infections: A mechanism of disease recurrence, inflammation, and bone and cartilage destruction

Bone and joint infections are devastating afflictions. Although medical interventions and advents have improved their care, bone and joint infections still portend dismal outcomes. Indeed, bone and joint infections are associated with extremely high mortality and morbidity rates and, generally, occur secondary to the aggressive pathogen Staphylococcus aureus. The consequences of bone and joint infections are further compounded by the fact that although they are aggressively treated, they frequently recur and result in massive bone and articular cartilage loss. Here, we review the literature and chronicle the fact that the fundamental cellular components of the musculoskeletal system can be internally infected with Staphylococcus aureus, which explains the ready recurrence of bone and joint infections even after extensive administration of antibiotic therapy and debridement and offer potential treatment solutions for further study. Moreover, we review the ramifications of intracellular infection and expound that the massive bone and articular cartilage loss is caused by the sustained proinflammatory state induced by infection and offer potential combination therapies for further study to protect bone and cartilage.

The establishment of a rheumatoid arthritis primate model in Macaca fascicularis

Background

Rheumatoid arthritis (RA) is a long-term autoimmune disorder that mostly affects the joints and leads to the destruction of cartilage. An RA model in non-human primates is especially useful because of their close phylogenetic relationship to humans in terms of cross-reactivity to compounds developed using modern drug technologies.

Methods

We used a collagen-induced arthritis (CIA) model in Macaca fascicularis. CIA was induced by the immunization of chicken type II collagen. Swelling was measured as the longitudinal and transverse axes of 16 proximal interphalangeal joints.

Results

A new system for visual evaluation was created, with a perfect score of 16. Individual behavioral analysis was also conducted. Serum was collected once a week after the first immunization. Blood chemistry and inflammatory cytokine parameters were higher in the CIA group than in the wild type group.

Conclusion

In conclusion, we established CIA in M. fascicularis, and the results can be used for drug evaluation models.

A Reduction in B, T, and Natural Killer Cells Expressing CD38 by TAK-079 Inhibits the Induction and Progression of Collagen-Induced Arthritis in Cynomolgus Monkeys

Ectoenzyme CD38 is increased on lymphocytes in response to an antigenic challenge and it is hypothesized that targeting these activated lymphocytes could ameliorate pathologic activities in autoimmune diseases. The cynomolgus monkey is an appropriate model for assessing potential effects of targeting CD38 in humans because these species exhibit similar expression profiles. TAK-079 is a human monoclonal antibody (IgG_{1 λ} ) that binds to CD38 and lyses bound cells by complement-dependent cytotoxicity and antibody-dependent cell-mediated cytotoxicity. TAK-079 binds to monkey CD38 with an affinity at EC₅₀ 4.5 nM, and the potential activity of TAK-079 was investigated in a monkey collagen-induced arthritis model of autoimmune disease. Prophylactic administration of TAK-079 (3 mg/kg i.v. weekly) was well tolerated and prevented arthritis development compared with vehicle-treated control animals, which exhibited progressive disease with radiographic damage and worsening clinical scores over the study course. Therapeutic treatment of arthritic monkeys with TAK-079 (3 mg/kg i.v. weekly) was also well tolerated and reduced disease progression and symptoms. Arthritis scores and joint swelling were significantly lower than the vehicle control, accompanied by decreases in blood levels of C-reactive protein, alkaline phosphatase, and natural killer, B, and T cells. Histopathology, morphometry, and radiology revealed significantly less joint damage in animals exposed prophylactically to TAK-079 treatment compared with vehicle-treated animals and significantly less damage in animals treated therapeutically with TAK-079 or dexamethasone (0.1 mg/kg oral gavage daily), illustrating potential disease-modifying activity. In conclusion, these data indicate that depletion of CD38-expressing cells could be a therapeutic mechanism for treating autoimmune diseases. SIGNIFICANCE STATEMENT: This study demonstrates that targeting CD38-expressing leukocytes with a cytolytic antibody can ameliorate autoimmune disease in cynomolgus monkeys. The study gives a unique perspective into this therapeutic strategy because the three other anti-CD38 cytolytic antibodies in clinical development (daratumumab, isatuximab, and MOR202) cannot be tested in similar models because they do not crossreact with CD38 expressed by new world primates.

Osteoblastic PLEKHO1 contributes to joint inflammation in rheumatoid arthritis

Background

Osteoblasts participating in the inflammation regulation gradually obtain concerns. However, its role in joint inflammation of rheumatoid arthritis (RA) is largely unknown. Here, we investigated the role of osteoblastic pleckstrin homology domain-containing family O member 1 (PLEKHO1), a negative regulator of osteogenic lineage activity, in regulating joint inflammation in RA.

Methods

The level of osteoblastic PLEKHO1 in RA patients and collagen-induced arthritis (CIA) mice was examined. The role of osteoblastic PLEKHO1 in joint inflammation was evaluated by a CIA model and a K/BxN serum-transfer arthritis (STA) model which were induced in osteoblast-specific Plekho1 conditional knockout mice and mice expressing high Plekho1 exclusively in osteoblasts, respectively. The effect of osteoblastic PLEKHO1 inhibition was explored in a CIA mice model and a non-human primate arthritis model. The mechanism of osteoblastic PLEKHO1 in regulating joint inflammation were performed by a series of in vitro studies.

Results

PLEKHO1 was highly expressed in osteoblasts from RA patients and CIA mice. Osteoblastic Plekho1 deletion ameliorated joint inflammation, whereas overexpressing Plekho1 only within osteoblasts exacerbated local inflammation in CIA mice and STA mice. PLEKHO1 was required for TRAF2-mediated RIP1 ubiquitination to activate NF-κB for inducing inflammatory cytokines production in osteoblasts. Moreover, osteoblastic PLEKHO1 inhibition diminished joint inflammation and promoted bone formation in CIA mice and non-human primate arthritis model.

Conclusions

These data strongly suggest that the highly expressed PLEKHO1 in osteoblasts contributes to joint inflammation in RA. Targeting osteoblastic PLEKHO1 may exert dual therapeutic action of alleviating joint inflammation and promoting bone formation in RA.

Sarilumab plus methotrexate suppresses circulating biomarkers of bone resorption and synovial damage in patients with rheumatoid arthritis and inadequate response to methotrexate: a biomarker study of MOBILITY

Background

Interleukin 6 (IL-6) signaling plays a key role in the pathophysiology of rheumatoid arthritis (RA) and is inhibited by sarilumab, a human monoclonal antibody blocking the IL-6 receptor alpha (IL-6Rα). The effects of sarilumab plus methotrexate (MTX) on serum biomarkers of joint damage and bone resorption were assessed in two independent studies (phase II (part A) and phase III (part B)) of patients with RA with a history of inadequate response to MTX from the MOBILITY study (NCT01061736).

Methods

Serum samples were analyzed at baseline and prespecified posttreatment time points. Biomarkers of tissue destruction, cartilage degradation, and synovial inflammation were measured in part A; assessment of these markers was repeated in part B and included additional analysis of biomarkers of bone formation and resorption (including soluble receptor activator of nuclear factor-kB ligand (sRANKL)). A mixed model for repeated measures was used to compare treatment effects on change in biomarkers. Additionally, changes from baseline in biomarkers were compared between American College of Rheumatology 50 % responders and nonresponders and between patients who achieved or did not achieve low disease activity (LDA), separately by treatment group, at week 24.

Results

In part A, sarilumab 150 and 200 mg every 2 weeks (q2w) significantly reduced biomarkers of tissue destruction, cartilage degradation, and synovial inflammation at both 2 and 12 weeks posttreatment (p < 0.05 vs placebo). These results were replicated in part B, with markers of these damaging processes reduced at weeks 2 and 24 (p < 0.05 vs placebo). Additionally, sarilumab 200 mg q2w significantly reduced both sRANKL and sRANKL/osteoprotegerin ratio at week 24 (p < 0.01 vs placebo). Trends for reduction were noted for several biomarkers in patients who achieved LDA compared with those who did not.

Conclusions

Sarilumab plus MTX significantly suppressed biomarkers of bone resorption and joint damage, as compared with placebo plus MTX, in patients with RA. Additional work is needed to determine whether differences in biomarker profiles at baseline or posttreatment can identify patients who achieve improvement in disease activity.

Trial registration

ClinicalTrials.gov, NCT01061736, February 2, 2010.

Leucine-rich α2 -glycoprotein as a potential biomarker for joint inflammation during anti-interleukin-6 biologic therapy in rheumatoid arthritis

OBJECTIVE

To investigate whether leucine-rich α2 -glycoprotein (LRG) could be a biomarker for disease activity during interleukin-6 (IL-6) blockade treatment of rheumatoid arthritis (RA).

METHODS

In 59 RA patients who were treated with tocilizumab for 24 weeks, serum LRG levels were determined by enzyme-linked immunosorbent assay. RA disease activity was evaluated by the Clinical Disease Activity Index (CDAI). Receiver operating characteristic (ROC) curve analysis was used to examine the diagnostic performance of LRG and other biomarkers. In monkeys with experimental autoimmune arthritis, swollen joint counts, joint pathologic changes, and blood levels of C-reactive protein (CRP) and LRG were evaluated after treatment with anti-IL-6 receptor antibody.

RESULTS

Among tocilizumab-treated RA patients, those with active disease (CDAI >2.8) had significantly higher serum LRG levels compared to those whose disease was in remission. ROC curve analysis suggested that the LRG level was more useful than the CRP or matrix metalloproteinase 3 level or the erythrocyte sedimentation rate in discriminating between remission and active disease during therapy with tocilizumab. In monkeys treated with IL-6 blockade, joint scores were more closely correlated with LRG levels than with CRP levels. Histologic analysis of joints revealed that LRG levels correlated significantly with granulomatous tissue formation, cartilage degeneration, and bone destruction in IL-6 blockade-treated monkeys with low levels of CRP.

CONCLUSION

Under conditions of IL-6 inhibition, LRG was more useful than other biomarkers in discriminating between active and inactive disease in human RA and in detecting joint inflammation in experimental arthritis. LRG may serve as a convenient biomarker for RA disease activity during IL-6 blockade treatment.

Methotrexate as combination partner of TNF inhibitors and tocilizumab. What is reasonable from an immunological viewpoint?

The goal of therapy of rheumatoid arthritis is to achieve a remission or at least low disease activity. TNF inhibitors induce high remission rates only in combination with methotrexate, whereas the efficacy of tocilizumab is optimal even as a monotherapy. In this article, the differing dependence of the biological drugs on methotrexate is explained from the viewpoint of an immunologist. A selective search and evaluation of the literature was performed with regard to the mode of action of TNF inhibitors, tocilizumab and methotrexate in rheumatoid arthritis. Methotrexate primarily inhibits the activation and proliferation of lymphocytes. TNF inhibitors suppress monocytes and myeloid dendritic cells, and tocilizumab has a broader activity and is directed against both the lymphoid as well as the myeloid compartment. In view of the broad mode of action of tocilizumab, it can be explained why this drug, in contrast to TNF inhibitors, is acting optimally even in monotherapy.

Muscle wasting associated with pathologic change is a risk factor for the exacerbation of joint swelling in collagen-induced arthritis in cynomolgus monkeys

BACKGROUND

Not only joint destruction but also muscle wasting due to rheumatoid cachexia has been problem in terms of quality of life of patients with rheumatoid arthritis (RA). In the present study, we performed histopathological examination and assessed relationships between characteristic parameters relating to muscle and joint swelling in a collagen-induced arthritis (CIA) model using cynomolgus monkeys (CMs).

METHODS

Female CMs were used and CIA was induced by twice immunizations using bovine type II collagen with Freund's complete adjuvant. Arthritis level was evaluated from the degree of swelling at the peripheral joints of the fore and hind limbs. Food consumption, body weight, and serum biochemical parameters were measured sequentially. Five or 6 animals per time point were sacrificed at 2, 3, 5 and 9 weeks after the first immunization to obtain quadriceps femoris specimens for histopathology. Pimonidazole hydrochloride was intravenously administered to determine tissue hypoxia in skeletal muscle.

RESULTS

Gradual joint swelling was observed and the maximum arthritis score was noted at Week 5. In histopathology, necrosis of muscle fiber in the quadriceps femoris was observed only at Week 2 and the most significant findings such as degeneration, atrophy, and regeneration of muscle fiber were mainly observed at Week 5. Food consumption was decreased up to Week 4 but recovered thereafter. Body weight decreased up to Week 5 and did not completely recover thereafter. A biphasic increase in serum cortisol was also observed at Weeks 2 and 5. Histopathology showed that muscle lesions were mainly composed of degeneration and atrophy of the muscle fibers, and ATPase staining revealed that the changes were more pronounced in type II muscle fiber than type I muscle fiber. In the pimonidazole experiment, mosaic pattern in skeletal muscle was demonstrated in the intact animal, but not the CIA animal. Increased arthritis score was accompanied by a decrease in serum creatinine, a marker that reflects muscle mass.

CONCLUSIONS

Muscle wasting might exacerbate joint swelling in a collagen-induced arthritis model of cynomolgus monkeys.

Advances in research on animal models of rheumatoid arthritis

At present, rheumatoid arthritis (RA) is considered a type of autoimmune disease. Its pathology is not certain, and effective drugs with less toxicity have not been established. The establishment and application of animal models are effective methods for RA research, especially using animal models similar to humans. Arthritis is more heterogeneous, and this is an important starting point when discussing animal models for arthritis. Animal models are instrumental in understanding the etiology and pathogenetic mechanisms of RA. Appropriate animal models should be selected according to experiments because they have different traits. Various methods have been applied to induce arthritis in animal experimental models, which have provided important insights into the etiopathogenetic mechanisms of human RA. This review was written to give a broad introduction of the current stage of RA model and hope to offer beneficial help for RA-related research.

Radiologic analysis of the effect of tocilizumab on hands and large joints in children with systemic juvenile idiopathic arthritis

OBJECTIVES

To assess the efficacy of tocilizumab for preventing damage to the joints of systemic juvenile idiopathic arthritis (sJIA) patients, we examined serial radiographs of the hands and large weight-bearing joints of these patients before and after treatment with this agent.

METHODS

Nine patients with sJIA receiving 8 mg/kg of tocilizumab intravenously every 2 weeks were studied. The mean follow-up period was 82 months. The number of active joints and laboratory markers of inflammation were assessed before and after tocilizumab treatment, together with radiologic evaluation of the hips, knees, ankles, shoulders, and elbows. The latter examination included soft tissue swelling, juxta-articular osteoporosis, epiphyseal irregularity, joint-space narrowing, cyst formation, erosion, and localized growth abnormalities. Modified Larsen scores for the large joints and the Poznanski score were also recorded.

RESULTS

After tocilizumab treatment, the number of active joints and serum inflammatory markers decreased (p < 0.01). There was a decrease in radiologic abnormalities at the final follow-up (p < 0.01) with the exception of localized growth abnormalities. Radiologic improvement was observed in 47 joints (52%), but ten (11%) worsened. Total Larsen score was decreased from 15.8 to 10.9 at the final follow-up. Although the Poznanski score did not change after tocilizumab treatment, it was closely correlated with the total Larsen score (r = 0.53, p < 0.05).

CONCLUSIONS

We describe radiologic improvement of the majority of damaged large joints in sJIA following tocilizumab therapy, but some deteriorated further despite stabilization of systemic inflammatory responses. Further studies with a larger number of patients are needed.

GP130 cytokines and bone remodelling in health and disease

Cytokines that bind to and signal through the gp130 co-receptor subunit include interleukin (IL)-6, IL-11, oncostatin M (OSM), leukemia inhibitory factor (LIF), cardiotrophin-1 (CT-1), and ciliary neutrophic factor (CNTF). Apart from contributing to inflammation, gp130 signalling cytokines also function in the maintenance of bone homeostasis. Expression of each of these cytokines and their ligand-specific receptors is observed in bone and joint cells, and bone-active hormones and inflammatory cytokines regulate their expression. gp130 signalling cytokines have been shown to regulate the differentiation and activity of osteoblasts, osteoclasts and chondrocytes. Furthermore, cytokine and receptor specific gene-knockout mouse models have identified distinct roles for each of these cytokines in regulating bone resorption, bone formation and bone growth. This review will discuss the current models of paracrine and endocrine actions of gp130-signalling cytokines in bone remodelling and growth, as well as their impact in pathologic bone remodelling evident in periodontal disease, rheumatoid arthritis, spondylarthropathies and osteoarthritis.

Intercellular adhesion molecule-1 on synovial cells attenuated interleukin-6-induced inhibition of osteoclastogenesis induced by receptor activator for nuclear factor κB ligand

In a co-culture of osteoclast precursor cells and synovial cells, interleukin-6 (IL-6) induces osteoclast formation. In contrast, in a monoculture of osteoclast precursor cells, IL-6 directly suppresses receptor activator for nuclear factor κB ligand (RANKL)-induced differentiation of osteoclast precursor cells into osteoclasts. In the present study, we explored why the effect of IL-6 differed between the monoculture and the co-culture systems. In the monoculture, mouse osteoclast precursor cell line, RAW 264·7 (RAW) cells were cultured with soluble RANKL (sRANKL) for 24 h or 3 days. sRANKL increased both expression of osteoclastogenesis marker, tartrate-resistant acid phosphatase isoform 5b (TRAP5b) and nuclear factor of activated T cells cytoplasmic 1 (NFATc1), whereas the co-addition of IL-6 decreased them both in a dose-dependent manner. In the co-culture, RAW cells and human synovial cell line, SW982 cells were cultured with IL-6+soluble IL-6 receptor (sIL-6R) for 3 days. TRAP5b and NFATc1 expression reduced by IL-6 was increased by the addition of SW982 cells in a manner dependent upon the number of added cells. IL-6+sIL-6R treatment significantly induced RANKL production in SW982 cells, and anti-RANKL antibody inhibited IL-6+sIL-6R-induced osteoclastogenesis. SW982 cells expressed high levels of ICAM-1 originally, and ICAM-1 expression was increased significantly by IL-6+sIL-6R. Anti-ICAM-1 antibody suppressed IL-6-induced osteoclastogenesis. Finally, in the monoculture system, addition of sICAM-1 dose-dependently restored the expression of TRAP5b reduced by IL-6. Similar results were obtained when the formation of TRAP-positive multi-nuclear cells were examined using mouse bone marrow cells. In conclusion, IL-6 gave different results in the co-culture and monoculture systems because in the co-culture, ICAM-1 from the synovial cells restored osteoclastogenesis suppressed by IL-6.

Targeting interleukin-6 in pediatric rheumatic diseases

PURPOSE OF REVIEW

To describe the most recent data regarding the role of interleukin-6 (IL-6) in immune and inflammatory responses, the mode of action and safety information on tocilizumab, the only available IL-6 inhibitor, and discuss recent results on the therapeutic inhibition of IL-6 in pediatric rheumatic diseases.

RECENT FINDINGS

New data on the effects of IL-6 on T and B cells have been published. Clinical trials with tocilizumab in adults, particularly with rheumatoid arthritis, provide new data on mechanism of action and a reasonably wide safety database. A withdrawal design trial showed marked efficacy in systemic juvenile idiopathic arthritis (s-JIA). Open label studies or anecdotal reports suggest possible efficacy also in other JIA subtypes, as well as other rheumatic diseases.

SUMMARY

Targeting IL-6 activities is an effective approach in the treatment of chronic inflammatory diseases. The long-term benefit and safety of tocilizumab have to be defined in long-term extension studies. The risk/benefit ratio appears to be particularly favorable in s-JIA. With the increasing number of biologics becoming available, future efforts should be directed to the definition of biomarkers that will identify responders to each novel biologic, allowing a personalized approach.

A novel distal enhancer mediates cytokine induction of mouse RANKl gene expression

Chronic inflammatory states are associated with increased bone loss. This increase is often linked to an elevation in receptor activator of nuclear factor-kappaB ligand (RANKL), a TNFalpha-like factor essential to osteoclast formation. In this study, we document the ability of IL-6 in combination with IL-6 soluble receptor (IL-6/IL-6sR) and oncostatin M to induce Rankl expression in stromal cells via signal transducer and activator of transcription 3 (STAT3). We used chromatin immunoprecipitation-tiled DNA microarray analysis to determine sites of action of STAT3 at the Rankl locus and to assess the consequences of binding on histone H4 acetylation and RNA polymerase II recruitment. Both IL-6/IL-6 soluble receptor and oncostatin M stimulated STAT3 binding upstream of the Rankl transcriptional start site. Although previously identified enhancers bound STAT3, a more distal enhancer termed mRLD6 was a particular focus of STAT3 binding. When fused to a heterologous promoter, this enhancer was highly active, containing two functionally active STAT response elements. Importantly, small interfering RNA knockdown of Stat3 mRNA and protein, but not that of Stat1 or Stat5a, was effective in limiting Rankl mRNA up-regulation. Interestingly, although RNA polymerase II and histone H4 acetylation marked many of the enhancers under basal conditions, the levels of both were strongly increased after cytokine treatment, particularly at mRLD6. Finally, mRLD6 was also a target for forskolin-induced cellular response element-binding protein (CREB) recruitment, which potentiated cytokine activity. Our studies provide new insight into mechanisms by which glycoprotein 130 activating cytokines induce RANKL expression.

Recent advances in neutralizing the IL-6 pathway in arthritis

Recent advances in understanding the mechanism(s) of how IL-6 trans-signaling regulates immune cell function and promotes inflammation in autoimmune arthritis are critically reviewed. Serum and/or synovial fluid (SF) IL-6 is markedly elevated in adult and juvenile rheumatoid arthritis (RA), psoriatic arthritis (PsA), ankylosing spondylitis (AS) and osteoarthritis (OA). IL-6, in concert with IL-17, determines the fate of CD4⁺ lymphocytes and therefore TH₁₇ cell differentiation. IL-6 also plays a critical role in modulating B-lymphocyte activity. The recognition that IL-6 trans-signaling regulates inflammation resulted in the development of tocilizumab, a fully humanized monoclonal antibody that neutralizes the biological activity of the IL-6-receptor (IL-6R). Significant clinical benefit was demonstrated as well as reduced serum IL-6 levels with suppression of X-ray progression of disease in several clinical trials in which juvenile or adult RA patients were treated with tocilizumab monotherapy or tocilizumab plus methotrexate. However, levels of serum and/or SF IL-6 cytokine protein superfamily members, adiponectin, oncostatin M, pre-B-cell colony enhancing factor/visfatin and leukemia inhibitory factor are also elevated in RA. Additional studies will be required to determine if anti-IL-6 trans-signaling inhibition strategies with tocilizumab or recombinant soluble IL-6R reduce the level of these cytokines.

Reduction of particle-induced osteolysis by interleukin-6 involves anti-inflammatory effect and inhibition of early osteoclast precursor differentiation

The goal of this study was to define the anti-osteoclastogenic and/or anti-inflammatory role of IL-6 in inflammatory bone resorption using in vivo and in vitro methods. To this end, titanium particles were placed on murine calvaria, and bone resorption and osteoclast formation quantified in wild-type and IL-6(-/-) mice. In this model, calvarial bone loss and osteoclast formation were increased in titanium-treated IL-6(-/-) mice. Although basal numbers of splenic osteoclast precursors (OCP) were similar, IL-6(-/-) mice treated with particles in vivo had increased splenic OCP suggesting an enhanced systemic inflammatory response. In vitro osteoclastogenesis was measured using splenic (OCP) at various stages of maturation, including splenocytes from WT, IL-6(-/-) and TNFalpha transgenic mice. ELISA was used to measure TNFalpha production. IL-6 inhibited osteoclastogenesis in early OCP obtained from wild-type and IL-6(-/-) spleens. Pre-treatment of OCP with M-CSF for three days increased the CD11b(high)/c-Fms+ cell population, resulting in an intermediate staged OCP. Osteoclastogenesis was unaffected by IL-6 in M-CSF pre-treated and TNFalpha transgenic derived OCP. IL-6(-/-) splenocytes secreted greater concentrations of TNFalpha in response to titanium particles than WT; addition of exogenous IL-6 to these cultures decreased TNFalpha expression while anti-IL-6 antibody increased TNFalpha. While IL-6 lacks effects on intermediate staged precursors, the dominant in vivo effects of IL-6 appear to be related to strong suppression of early OCP differentiation and an anti-inflammatory effect targeting TNFalpha. Thus, the absence of IL-6 results in increased inflammatory bone loss.

IL-6R distribution in normal human and cynomolgus monkey tissues

Interleukin-6 (IL-6) is a pleiotropic cytokine and a contributing factor in many diseases such as rheumatoid arthritis, Castleman's disease, Crohn's disease, and multiple myeloma. Since the blockade of the signaling pathway of the IL-6/interleukin-6 receptor (IL-6R)/gp130 complex is considered to have therapeutic value in such diseases, we developed an IL-6R humanized antibody (tocilizumab). In the current report, distribution of IL-6R in both normal human and cynomolgus monkey tissues was assessed as fundamental data to support preclinical and clinical studies of tocilizumab. Human and cynomolgus monkey tissue panels were stained with commercially available anti-human IL-6R and a species- and isotype-matched negative antibody, as well as assay control slides. The detection system applied used an Envision immunoperoxidase staining procedure with DAB reaction. Positive reactions were observed in the tissue elements of lymphatic, hematopoietic, digestive, reproductive, exocrine, endocrine, neural, muscular, epidermal, respiratory, and urinary systems of the human and cynomolgus monkey tissue panels. The current report is inclusive of a wide variety of tissues and shows the distribution of IL-6R to be similar for both human and monkey tissues. We consider this information fundamental for the support and interpretation of preclinical and clinical studies of anti-IL-6R antibody therapy.