Rheumatoid Arthritis: Takayanagi H

Takayanagi H. · Department of Cell Signaling, Graduate School, Tokyo Medical and Dental University. · Nippon Rinsho. · Pubmed #19432129 No free full text.

Abstract: The immune and skeletal systems share various molecules including cytokines, signaling molecules, transcription factors and membrane receptors, while immune cells are maintained in the bone marrow, which provides a physiological space for mutual interaction. In rheumatoid arthritis, synovium is the active site for the interplay between the immune and bone cells, the study of which accelerated the interdisciplinary field of osteoimmunology. This emerging field will be of great importance to better understand how antirheumatic drugs work and to develop new therapeutic strategies for rheumatic diseases.

Inoue H, Takayanagi H. · Department of Cell Signaling, Graduate School, Tokyo Medical and Dental University. · Clin Calcium. · Pubmed #19252243 No free full text.

Abstract: In rheumatoid arthritis, T cells activation enhances osteoclast differentiation and bone destruction through receptor activator of NF-kappaB ligand (RANKL) . Recent study revealed the importance of interleukin-17 (IL-17) -producing helper T cell subset (Th17) in bone destruction. The emerging field of osteoimmunology will be of great importance not only to the better understanding of osteoclast differentiation and activation but also to the regulation of inflammation-associated bone destruction.

Nakashima T, Takayanagi H. · Department of Cell Signaling, Graduate School, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo 113-8549, Japan. · Arch Biochem Biophys. · Pubmed #18410741 No free full text.

Abstract: Investigation into arthritis, as well as numerous bone phenotypes found in mice lacking immune-related genes, has highlighted the importance of the interplay between the bone and immune systems, which has led to the emergence and evolution of the field of osteoimmunology. RANKL stimulates osteoclastogenesis through nuclear factor of activated T cells (NFAT) c1, which is also a crucial regulator of immunity. In rheumatoid arthritis, bone destruction is caused by the enhanced activity of osteoclasts, which is mainly dependent on interleukin-17-producing helper T cells (T(H)17). The scope of osteoimmunology has been extended to encompass a wide range of molecular and cellular interactions. The framework of osteoimmunology will provide a scientific basis for future therapeutic approaches to diseases related to both of these systems.

Takayanagi H. · Tokyo Medical and Dental University, Graduate School, Department of Cell Signaling. · Clin Calcium. · Pubmed #17404476 No free full text.

Abstract: In autoimmune arthritis, activation of T cells induces bone destruction through receptor activator of NF-kappaB ligand (RANKL) . Recent study revealed interleukin-17 (IL-17) -producing helper T cell subset (Th17) , but not IFN-gamma-producing Th1, to be responsible for bone destruction. Here we summarize the current understanding of osteoclast differentiation and activation in the context of osteoimmunology.

Suematsu A, Takayanagi H. · Department of Cell Signaling, Graduate School, Tokyo Medical and Dental University. · Nihon Rinsho Meneki Gakkai Kaishi. · Pubmed #17332701 links to  free full text

Abstract: The immune and skeletal systems share a number of regulatory molecules including cytokines, signaling molecules, transcription factors and membrane receptors, in common. Consequently, the physiology and pathology of one system may very well affect the other. Research into the cartilage and bone destruction associated with rheumatoid arthritis (RA) has highlighted the importance of the interplay between the immune and skeletal systems. This interdisciplinary field called osteoimmunology has attracted much attention in recent years. Recently, animal models deficient in immunomodulatory molecules have been found frequently to develop an unexpected skeletal phenotype. Receptor activator of NF-kappaB ligand (RANKL) is an essential factor for the induction of osteoclastogenesis that links the immune and skeletal systems. Thus, osteoimmunology is becoming increasingly important for understanding the pathogenesis of bone destruction in RA and for developing new therapeutic strategies for diseases affecting both systems. Here we summarize recent advances on the study of the regulation of cartilage and bone destruction by the immune system.

Sato K, Takayanagi H. · Department of Cell Signaling, Graduate School, Tokyo Medical and Dental University, Japan. · Curr Opin Rheumatol. · Pubmed #16763464 No free full text.

Abstract: PURPOSE OF REVIEW: Osteoclasts are terminally differentiated cells of the monocyte/macrophage lineage that resorb bone matrix. Bone destruction in rheumatoid arthritis is mainly attributable to the abnormal activation of osteoclasts, and studies on activation of osteoclasts by the immune system have led to the new research field called osteoimmunology. This interdisciplinary field is very important to biologic research and to the treatment of diseases associated with the bone and immune systems. RECENT FINDINGS: The T-cell-mediated regulation of osteoclast differentiation is dependent on cytokines and membrane-bound factors expressed by T cells. The cross-talk between receptor activator of nuclear factor-kappaB ligand and interferon-gamma has been shown to be crucial for the regulation of osteoclast formation in arthritic joints. Recent studies indicate that an increasing number of immunomodulatory factors are associated with the regulation of bone metabolism: nuclear factor of activated T cells c1 has been shown to be the key transcription factor for osteoclastogenesis, the activation of which requires calcium signaling induced by the immunoglobulin-like receptors. SUMMARY: New findings in osteoimmunology will be instrumental in the development of strategies for research into the treatment of various diseases afflicting the skeletal and immune systems.

Takayanagi H, Sato K, Takaoka A, Taniguchi T. · Department of Cell Signaling, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan. · Immunol Rev. · Pubmed #16313349 No free full text.

Abstract: Interferons (IFNs) play crucial roles in the regulation of a wide variety of innate and adaptive immune responses. Type I interferons (IFN-alpha/beta) are central to the host defense against pathogens such as viruses, whereas type II interferon (IFN-gamma) mainly contributes to the T-cell-mediated regulation of the immune responses. Studies of bone destruction associated with rheumatoid arthritis have highlighted the importance of the interaction between the immune and skeletal systems. Recently, a new research area, termed osteoimmunology, has been spawned by a series of studies focusing on the signaling networks between IFN and other cytokines in bone metabolisms. It has been revealed that IFN-gamma interferes with the osteoclast differentiation induced by receptor activator of nuclear factor-kappaB ligand (RANKL), and this mechanism is critical for the suppression of pathological bone resorption associated with inflammation. In addition, RANKL induces the IFN-beta gene in osteoclast precursor cells, and this induction constitutes a critical aspect of the negative feedback regulation mechanisms of RANKL signaling to suppress excessive osteoclastogenesis. Furthermore, a novel function of signal transducer and activator of transcription 1 (Stat1), the essential transcription factor for both type I and type II IFN responses, was revealed in the regulation of osteoblast differentiation. Collectively, these studies unveil novel aspects of the IFN system and indicate the operation of the intricate signaling network among IFN and other cytokine systems in bone remodeling, which might offer a molecular basis for the treatment of bone diseases.

Kim S, Takayanagi H. · Department of Pathology, CBR, Harvard Medical School. · Nippon Rinsho. · Pubmed #16164211 No free full text.

Abstract: Bone homeostasis is maintained by the balanced activities of two bone specific cell types: bone-resorbing osteoclasts and bone-forming osteoblasts. Since the disorder of osteoclast differentiation and/or activity leads to bone diseases such as postmenopausal osteoporosis, rheumatoid arthritis, etc., it is central to identify factors that regulate osteoclastogenesis and to study the regulatory mechanisms. Here, we show IFNs (IFN-beta and IFN-gamma) as new regulators of osteoclastogenesis: each IFN inhibits osteoclastogenesis via different molecular mechanisms. We also show the regulation of osteoblastogenesis by Stat1, an essential transcription factor for IFN signal. Our research will shed light on the novel cross-talk between IFN signals and bone cells (Table 1).

Sato K, Takayanagi H. · Department of Cell Signaling, Graduate School, Tokyo Medical and Dental University. · Nippon Rinsho. · Pubmed #16164207 No free full text.

Abstract: Bone destruction in rheumatoid arthritis (RA) is caused by osteoclasts, multinuclear cells of the monocyte/macrophage lineage. Since osteoclast differentiation factor RANKL (receptor activator of NF-kappaB ligand) is expressed on activated T cells and T cells, especially Th1 type cells, are implicated in the pathogenesis of RA, it has been believed that they play an important role in the osteoclastogenesis in RA lesions. However, main Th1-type cytokine IFN-gamma strongly suppresses osteoclastogenesis, casting doubt on the relevancy of Th1 cells as stimulators of osteoclastogenesis. Recently, IL-17 from T cells has been reported to enhance osteoclastogenesis. Characterizing real Th subsets which support osteoclastogenesis would be beneficial to solving a clinically important problem, bone destruction in RA.

Takayanagi H. · Department of Cell Signaling, Graduate School, Tokyo Medical and Dental University, SORST, JST. · Nippon Rinsho. · Pubmed #16164203 No free full text.

Abstract: Since research into the bone destruction in rheumatoid arthritis led us to realize the importance of the interplay of the immune and skeletal systems, interdisciplinary research field called osteoimmunology has attracted further attention. This is partly based on the identification of a number of unexpected bone phenotypes in mice lacking immunomodulatory molecules. Accumulating evidence suggests that the immune and skeletal systems share not only cytokines but also various signaling molecules, transcription factors and membrane receptors. This emerging field will be increasingly important not only for the future strategy for rheumatic diseases but also for clinical and basic studies in all the related fields.

Takayanagi H. · Department of Cell Signaling, Graduate School, Tokyo Medical and Dental University, Center of Excellence (COE) Program for Frontier Research on Molecular Destruction and Reconstruction of Tooth and Bone, Bunkyo-ku, Tokyo, Japan. · J Periodontal Res. · Pubmed #15966905 No free full text.

Abstract: OBJECTIVES: The metabolism of hard tissue is influenced by the immune system. Research into the bone destruction associated with inflammatory diseases such as periodontal disease and rheumatoid arthritis has highlighted the importance of the interplay of the immune and skeletal systems. This interdisciplinary research field, called 'osteoimmunology', has become increasingly important for each system by itself as well as the biology linking them. The history and recent progress of this field are reviewed. MATERIAL AND METHODS: 'Osteoimmunology' was coined to describe the pioneering work on the T-cell regulation of osteoclastogenesis by the receptor activator of nuclear factor-kappaB ligand (RANKL) and interferon (IFN)-gamma. Accumulating evidence suggests that the immune and skeletal systems share not only cytokines but also various signaling molecules, transcription factors and membrane receptors. The contribution of T cells to the pathogenesis of inflammatory bone destruction is discussed, and our recent findings are summarized to illustrate how the osteoimmunological network functions. RESULTS: RANKL is an osteoclastogenic cytokine that links bone and the immune system. Immunomodulatory cytokines such as IFNs also participate in the regulation of RANKL signaling and inflammatory bone loss. The transcription factor nuclear factor of activated T cells c1 (NFATc1) has been identified as a master switch regulator of osteoclastogenesis. In addition, immunoglobulin-like receptors are critically involved in bone homeostasis. CONCLUSION: Bone turns out to be a dynamic tissue that is constantly renewed, where the immune system participates to a hitherto unexpected extent. This emerging field will be of great importance to a better understanding and treatment of diseases of the skeletal and immune systems, as well as to the fundamental biology underpinning both.

Takayanagi H. · Department of Cell Signaling, Graduate School, Center of Excellence Program, Tokyo Medical and Dental University. · Nihon Rinsho Meneki Gakkai Kaishi. · Pubmed #15863966 links to  free full text

Abstract: The interdisciplinary field called osteoimmunology has attracted much attention, due to the observations that bone destruction is caused by an abnormal activation of the immune system in rheumatoid arthritis, and mice lacking immunomodulatory molecules often exhibit an unexpected bone phenotype. Osteoclasts are cells of monocyte/macrophage origin that degrade the bone matrix in health and disease. Receptor activator of NF-kappaB ligand (RANKL), a tumor necrosis factor (TNF) family cytokine, is an essential osteoclastogenic factor linking the bone and the immune system. In the genomewide screening of RANKL-inducible genes using GeneChip, we identified nuclear factor of activated T cells c1 (NFATc1) as the master transcription factor for osteoclastogenesis. We also applied the GeneChip method to the analysis of osteoimmunological regulation: analysis of costimulatory signal for RANKL and the target genes of antirheumatic drugs. Here we summarize our recent findings in the field of osteoimmunology obtained by GeneChip.

Takayanagi H. · Department of Cellular Physiological Chemistry, Graduate School, Center of Excellence Program, Tokyo Medical and Dental University. · Nippon Rinsho. · Pubmed #15799324 No free full text.

This publication has no abstract.

Takayanagi H. · Department of Cellular Physiological Chemistry, COE Program for Frontier Research on Molecular Destruction and Reconstruction of Tooth and Bone, Graduate School, Tokyo Medical and Dental University, Japan. · J Mol Med. · Pubmed #15776286 No free full text.

Abstract: Recently a close relationship between the immune and skeletal systems or the interdisciplinary field called osteoimmunology has attracted much attention due to the observations that bone destruction is caused by an abnormal activation of the immune system in rheumatoid arthritis, and that mice lacking immunomodulatory molecules often exhibit an unexpected bone phenotype. Osteoclasts are cells of monocyte/macrophage origin that degrade the bone matrix. They are among the key players in the control of bone metabolism in health and disease. Receptor activator of NF-kappaB ligand (RANKL), a tumor necrosis factor (TNF) family cytokine, induces the differentiation of osteoclasts in the presence of macrophage-colony stimulating factor. RANKL activates TRAF6, c-Fos, and calcium signaling pathways, all of which are indispensable for the induction and activation of nuclear factor of activated T cells (NFAT) c1, the master transcription factor for osteoclastogenesis. The autoamplification of NFATc1 gene results in the efficient induction of osteoclast-specific genes. An AP-1 transcription factor complex containing c-Fos plays a crucial role in these processes, although results in conditional knockout mice show that Jun family members have a redundant role. The immunoreceptor tyrosine-based activation motif (ITAM) is an important signaling component for a number of receptors in the immune system including T-cell, B-cell, NK-cell, and Fc receptors, but its contribution to the skeletal system remains unclarified. In search for the calcium-mobilizing mechanism during osteoclastogenesis we determined that multiple immunoglobulinlike receptors associated with ITAM-harboring adaptors, Fc receptor common gamma chain (FcRgamma), and DNAX-activating protein (DAP) 12, are essential for osteoclastogenesis. In osteoclast precursor cells FcRgamma-associated receptors include osteoclast-associated receptor and paired immunoglobulinlike receptor A, while triggering receptor expressed in myeloid cells 2 and signal-regulatory protein beta1 preferentially associate with DAP12. In cooperation with RANKL these receptors activate phospholipase Cgamma and calcium signaling essential for the induction of NFATc1 through ITAM phosphorylation. Thus we have established the importance of the ITAM-mediated costimulatory signals in RANKL-induced osteoclast differentiation, which is analogous to the role of costimulatory signals in the immune system. Here we summarize recent advances in the study of signaling mechanism of osteoclast differentiation in the context of osteoimmunology.

Takayanagi H. · No affiliation provided · Ryumachi. · Pubmed #14598653 No free full text.

This publication has no abstract.

Takayanagi H. · Department of Immunology, Faculty of Medicine and Graduate School of Medicine, University of Tokyo. · Nippon Rinsho. · Pubmed #12510352 No free full text.

Abstract: Bone destruction in rheumatoid arthritis is characterized as 'the defective control of bone metabolism by the immune system'. During the course of our study to investigate the mechanism of arthritic bone destruction, we have explored a new field called' osteo-immunology'. Here we summarize the regulation of the bone metabolism by signalling cross-talk between RANKL and IFNs, focusing on the T cell-mediated regulation of osteoclastogenesis by IFN-gamma. The better understanding of the interactions between bone and immune cells will provide further insights into the both fields.

Suematsu A, Tajiri Y, Nakashima T, Taka J, Ochi S, Oda H, Nakamura K, Tanaka S, Takayanagi H. · Department of Cell Signaling, Graduate School, Tokyo Medical and Dental University and COE Program for Frontier Research on Molecular Destruction and Reconstruction of Tooth and Bone, 1-5-45 Yushima, Tokyo 113-8549, Japan. · Mod Rheumatol. · Pubmed #17278017 No free full text.

Abstract: Finding a means to ameliorate and prevent bone destruction is one of the urgent issues in the treatment of rheumatoid arthritis. Recent studies revealed bone-resorbing osteoclasts to be essential for arthritic bone destruction, but to date there has been scarce experimental evidence for the underlying mechanism of the bone-protective effect of antirheumatic drugs. Here we examined the effects of one or a combination of disease-modifying antirheumatic drugs (DMARDs) on osteoclast differentiation to provide a cellular and molecular basis for their efficacy against bone destruction. The effects on osteoclast precursor cells and osteoclastogenesis-supporting cells were distinguished by two in vitro osteoclast culture systems. Methotrexate (MTX), bucillamine (Buc) and salazosulphapyridine (SASP) inhibited osteoclastogenesis by acting on osteoclast precursor cells and interfering with receptor activator of NF-kappaB ligand (RANKL)-mediated induction of the nuclear factor of activated T cells (NFAT) c1. MTX and SASP also suppressed RANKL expression on osteoclastogenesis-supporting mesenchymal cells. Interestingly, the combination of three antirheumatic drugs exerted a marked inhibitory effect on osteoclastogenesis even at a low dose at which there was much less of an effect when administered individually. These results are consistent with the reported efficacy of combined DMARDs therapy in humans and suggest that osteoclast culture systems are useful tools to provide an experimental basis for the bone-protective effects of antirheumatic drugs.

Takayanagi H. · Department of Cell Signaling, Graduate School, Tokyo Medical and Dental University, , Center of Excellence (COE) Program for Frontier Research on Molecular Destruction and Reconstruction of Tooth and Bone, Japan. · Mod Rheumatol. · Pubmed #17029070 No free full text.

Abstract: Research into the bone destruction associated with rheumatoid arthritis has highlighted the importance of the interplay of the immune and skeletal systems. Arthritic bone destruction is attributable to the defective control of osteoclastogenesis by T cells. We revealed that excessive expression of receptor activator of NF-kappaB ligand (RANKL) and a paucity of interferon-gamma underlie the enhanced osteoclastogenesis in arthritis. The interdisciplinary research field called osteoimmunology has attracted further attention after identification of a number of unexpected bone phenotypes in mice lacking immunomodulatory molecules. Accumulating evidence suggests that the immune and skeletal systems share not only cytokines but also various signaling molecules, transcription factors, and membrane receptors. Thus, bone turns out to be a dynamic tissue that is constantly renewed, where the immune system participates to a hitherto unexpected extent. This emerging field will be of great importance for a better understanding and treatment of rheumatic diseases.

Takayanagi H. · Department of Immunology, Graduate School of Medicine and Faculty of Medicine, University of Tokyo PRESTO, JST. · Clin Calcium. · Pubmed #15775138 No free full text.

Abstract: Osteoclasts play a critical role in bone destruction in rheumatoid arthritis. Activation of osteoclastogenesis is mediated by the enhanced expression of RANKL (receptor activator of NF-kappaB ligand), accompanied by reduced expression of its inhibitor, IFN-gamma. Accumulating evidence indicates that the osteoclast-targeted therapy is effective in arthritis models, suggesting a promising new strategy for rheumatoid bone destruction.

Takatsuna H, Asagiri M, Kubota T, Oka K, Osada T, Sugiyama C, Saito H, Aoki K, Ohya K, Takayanagi H, Umezawa K. · Department of Applied Chemistry, Faculty of Science and Technology, Keio University, Yokohama, Japan. · J Bone Miner Res. · Pubmed #15765185 No free full text.

Abstract: (-)-DHMEQ, a newly designed NF-kappaB inhibitor, inhibited RANKL-induced osteoclast differentiation in mouse BMMs through downregulation of the induction of NFATc1, an essential transcription factor of osteoclastogenesis. INTRODUCTION: Bone destruction is often observed in advanced case of rheumatoid arthritis and neoplastic diseases, including multiple myeloma. Effective and nontoxic chemotherapeutic agents are expected for the suppression of these bone destructions. RANKL induces activation of NF-kappaB and osteoclastogenesis in bone marrow-derived monocyte/macrophage precursor cells (BMMs). Targeted disruption or pharmacological suppression of NF-kappaB result in impaired osteoclastogenesis, but how NF-kappaB is involved in the regulation of osteoclastogenesis is not known. MATERIALS AND METHODS: The effect of (-)-dehydroxymethylepoxyquinomicin [(-)-DHMEQ] on osteoclast differentiation was studied using a culture system of mouse BMMs stimulated with RANKL and macrophage colony-stimulating factor. The mechanism of the inhibition was studied by biochemical analysis such as immunoblotting and retroviral transfer experiments. RESULTS: (-)-DHMEQ strongly inhibited RANKL-induced NF-kappaB activation in BMMs and inhibited RANKL-induced formation of TRACP(+) multinucleated cells. Interestingly, (-)-DHMEQ specifically inhibited the RANKL-induced expression of NFATc1 but not the expressions of TRAF6 or c-fos. Inhibition of osteoclast differentiation by (-)-DHMEQ was rescued by overexpression of NFATc1, suggesting that the inhibition is not caused by a toxic effect. Moreover, pit formation assays showed that (-)-DHMEQ also inhibited the bone-resorbing activity of mature osteoclasts. CONCLUSION: The inhibition of NF-kappaB suppresses osteoclastogenesis by downregulation of NFATc1, suggesting that NFATc1 expression is regulated by NF-kappaB in RANKL-induced osteoclastogenesis. Our results also indicate the possibility of (-)-DHMEQ becoming a new therapeutic strategy against bone erosion.

Urushibara M, Takayanagi H, Koga T, Kim S, Isobe M, Morishita Y, Nakagawa T, Löeffler M, Kodama T, Kurosawa H, Taniguchi T. · Graduate School of Medicine, University of Tokyo, Tokyo, Japan. · Arthritis Rheum. · Pubmed #15022321 links to  free full text

Abstract: OBJECTIVE: Suppression of bone destruction is required as part of an effective therapeutic strategy for autoimmune arthritis. Although numerous antirheumatic drugs are in clinical use, little is known about whether they inhibit bone destruction by acting on activated T cells or other cell types, such as bone-resorbing osteoclasts. This study was undertaken to determine whether leflunomide has a direct action on the osteoclast lineage and to gain insights into the molecular basis for the bone-protective effect of leflunomide. METHODS: The direct effect of leflunomide on osteoclast differentiation was investigated using an in vitro culture system of bone marrow monocyte/macrophages stimulated with receptor activator of NF-kappa B ligand (RANKL) and macrophage colony-stimulating factor. The molecular mechanism of the inhibition was analyzed by genome-wide screening. The T cell-independent effect of leflunomide was examined in rag-2(-/-) mice. RESULTS: Leflunomide blocked de novo pyrimidine synthesis and RANKL-induced calcium signaling in osteoclast precursor cells in vitro; hence, the induction of nuclear factor of activated T cells c1 (NF-ATc1) was strongly inhibited. The inhibition of this pathway is central to the action of leflunomide, since the inhibition was overcome by ectopic expression of NF-ATc1 in the precursor cells. Leflunomide suppressed endotoxin-induced inflammatory bone destruction even in rag-2(-/-) mice. CONCLUSION: Leflunomide has a direct inhibitory effect on RANKL-mediated osteoclast differentiation by inhibiting the induction of NF-ATc1, the master switch regulator for osteoclast differentiation. Our study suggests that the direct inhibitory action of leflunomide on osteoclast differentiation constitutes an important aspect in the amelioration of bone destruction, and that the RANKL-dependent NF-ATc1 induction pathway is a promising target for pharmacologic intervention in arthritic bone destruction.

Takayanagi H, Iizuka H, Juji T, Nakagawa T, Yamamoto A, Miyazaki T, Koshihara Y, Oda H, Nakamura K, Tanaka S. · The University of Tokyo, Japan. · Arthritis Rheum. · Pubmed #10693864 links to  free full text

Abstract: OBJECTIVE: To clarify the mechanism by which osteoclasts are formed in culture of rheumatoid synoviocytes by exploring the involvement of receptor activator of nuclear factor kappaB ligand (RANKL)/osteoclast differentiation factor (ODF). METHODS: Osteoclast formation was evaluated in cocultures of rheumatoid synovial fibroblasts and peripheral blood mononuclear cells (PBMC) in the presence of macrophage colony stimulating factor and 1,25-dihydroxyvitamin D3 (1,25[OH]2D3) utilizing separating membrane filters. RANKL/ODF expression was examined by Northern blotting in synovial tissues from 5 rheumatoid arthritis (RA) patients and tissues from patients with giant cell tumor (GCT), osteosarcoma (OS), and osteoarthritis (OA). RANKL/ODF expression and the ability of synovial fibroblasts to support osteoclastogenesis were investigated in coculture with PBMC in the presence or absence of 1,25(OH)2D3, and soluble RANKL/ODF and osteoprotegerin (OPG)/osteoclastogenesis inhibitory factor (OCIF) were measured by enzyme-linked immunosorbent assay. The effects of OPG/OCIF on the osteoclastogenesis in the primary culture of rheumatoid synoviocytes and the coculture system were determined. RESULTS: Synovial fibroblasts did not induce osteoclastogenesis when separately cocultured with PBMC. Northern blotting revealed that RANKL/ODF was highly expressed in all tissues from RA and GCT patients, but not from OA or OS patients. Cultured rheumatoid synovial fibroblasts efficiently induced osteoclastogenesis in the presence of 1,25(OH)2D3, which was accompanied by up-regulated expression of RANKL/ODF and decreased production of OPG/OCIF. Osteoclastogenesis from synoviocytes was dose-dependently inhibited by OPG/OCIF. CONCLUSION: RANKL/ODF expressed on synovial fibroblasts is involved in rheumatoid bone destruction by inducing osteoclastogenesis and would therefore be a good therapeutic target.

Takayanagi H, Juji T, Miyazaki T, Iizuka H, Takahashi T, Isshiki M, Okada M, Tanaka Y, Koshihara Y, Oda H, Kurokawa T, Nakamura K, Tanaka S. · Department of Orthopaedic Surgery, Third Department of Internal Medicine, and Fourth Department of Internal Medicine, Faculty of Medicine, the University of Tokyo, Tokyo 113-0033, Japan. · J Clin Invest. · Pubmed #10411542 links to  free full text

Abstract: Rheumatoid arthritis (RA) is characterized by a chronic inflammation of the synovial joints resulting from hyperplasia of synovial fibroblasts and infiltration of lymphocytes, macrophages, and plasma cells, all of which manifest signs of activation. Recent studies have revealed the essential role of osteoclasts in joint destruction in RA. Src family tyrosine kinases are implicated in various intracellular signaling pathways, including mitogenic response to growth factors in fibroblasts, activation of lymphocytes, and osteoclastic bone resorption. Therefore, inhibiting Src activity can be a good therapeutic strategy to prevent joint inflammation and destruction in RA. We constructed an adenovirus vector carrying the csk gene, which negatively regulates Src family tyrosine kinases. Csk overexpression in cultured rheumatoid synoviocytes remarkably suppressed Src kinase activity and reduced their proliferation rate and IL-6 production. Bone-resorbing activity of osteoclasts was strongly inhibited by Csk overexpression. Furthermore, local injection of the virus into rat ankle joints with adjuvant arthritis not only ameliorated inflammation but suppressed bone destruction. In conclusion, adenovirus-mediated direct transfer of the csk gene is useful in repressing bone destruction and inflammatory reactions, suggesting the involvement of Src family tyrosine kinases in arthritic joint breakdown and demonstrating the feasibility of intervention in the kinases for gene therapy in RA. off