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Nishimura R, Hata K, Ikeda F, Ichida F, Shimoyama A, Matsubara T, Wada M, Amano K, Yoneda T. Signal transduction and transcriptional regulation during mesenchymal cell differentiation. J Bone Miner Metab 2008; 26:203-12. [PMID: 18470659 DOI: 10.1007/s00774-007-0824-2] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2007] [Accepted: 10/02/2007] [Indexed: 12/11/2022]
Affiliation(s)
- Riko Nishimura
- Department of Molecular and Cellular Biochemistry, Osaka University Graduate School of Dentistry, Suita, Osaka, 565-0871, Japan.
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252
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Baken KA, Pennings JL, Jonker MJ, Schaap MM, de Vries A, van Steeg H, Breit TM, van Loveren H. Overlapping gene expression profiles of model compounds provide opportunities for immunotoxicity screening. Toxicol Appl Pharmacol 2008; 226:46-59. [DOI: 10.1016/j.taap.2007.08.026] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2007] [Revised: 08/17/2007] [Accepted: 08/29/2007] [Indexed: 11/28/2022]
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253
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Suda T, Takahashi N. Contributions to osteoclast biology from Japan. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2008; 84:419-38. [PMID: 19075515 PMCID: PMC3720546 DOI: 10.2183/pjab.84.419] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Accepted: 10/03/2008] [Indexed: 05/27/2023]
Abstract
Bone is a dynamic tissue, in which bone formation by osteoblasts and bone resorption by osteoclasts continue throughout life. In 1998, we molecularly cloned osteoclast differentiation factor (ODF), a long-thought factor responsible for osteoclast formation. This review article describes how Japanese scientists contributed to osteoclast biology before and after the discovery of ODF. This review article is based on the Louis V. Avioli Memorial Lecture of the American Society for Bone and Mineral Research (ASBMR) held in Honolulu in September, 2007.
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Affiliation(s)
- Tatsuo Suda
- Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan.
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254
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Matsunaga T, Shigetomi M, Hashimoto T, Suzuki H, Gondo T, Tanaka H, Sugiyama T, Taguchi T. Effects of bisphosphonate treatment on bone repair under immunosuppression using cyclosporine A in adult rats. Osteoporos Int 2007; 18:1531-40. [PMID: 17492246 DOI: 10.1007/s00198-007-0387-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Accepted: 04/17/2007] [Indexed: 11/29/2022]
Abstract
UNLABELLED The effect of cyclosporine A on bone turnover remains unclear. Using adult rats with vascularized bone transplantation, we show that long-term cyclosporine A administration increases bone turnover and zoledronic acid treatment enhances the reconstruction of cyclosporine A-administered skeleton. Bisphosphonates might be efficacious in human bone repair under immunosuppression using cyclosporine A. INTRODUCTION Bisphosphonate treatment effectively prevents bone loss after transplantation. However, recent evidence from gain- and loss-of-function experiments has indicated that calcineurin inhibitors, such as cyclosporine A (CsA), reduce bone turnover, and severely suppressed bone turnover might delay the union of human fractured bone. The purpose of this study was to investigate the effects of bisphosphonate treatment on the repair of CsA-administered skeleton. METHODS After skeletal reconstruction by vascularized tibial grafting, adult recipient rats were treated with intramuscular CsA (10 mg/kg/day) and low-dose (0.2 microg/kg/week) or high-dose (2 microg/kg/week) subcutaneous zoledronic acid alone or in combination for 8 weeks. Biochemical parameters were measured in blood and urine. The reconstructed skeleton was analyzed using soft X-ray, histology, dual energy X-ray absorptiometry, and three-point bending test. RESULTS CsA induced mild renal dysfunction, hyperparathyroidism and high bone turnover. High-dose zoledronic acid delayed cortical bone union at the distal host-graft junction, but its combination with CsA did not cause such a delay. High-dose zoledronic acid prevented CsA-induced bone loss and bone fragility in the reconstructed skeleton. CONCLUSION In this rat model, long-term CsA administration increases bone turnover, at least partly, through hyperparathyroidism and high-dose zoledronic acid treatment does not impair the union of CsA-administered bone.
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Affiliation(s)
- T Matsunaga
- Department of Orthopaedic Surgery, Yamaguchi University School of Medicine, 1-1-1 Minamikogushi, Yamaguchi 755-8505, Japan
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255
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Abstract
Antiresorptive agents have proven to be effective therapies for the treatment of bone diseases associated with excessive osteoclast activity. Decreased osteoclast formation, inhibition of osteoclast actions, and reduced osteoclast survival represent mechanisms by which antiresorptive agents could act. The goals of this article are to present the evidence that antiresorptive agents can decrease osteoclast survival through apoptosis, to review the mechanisms by which they are thought to activate the apoptotic process, and to consider whether the actions on apoptosis fully account for the antiresorptive effects. As background, the apoptotic process will be briefly summarized together with the evidence that factors that promote osteoclast survival affect steps in the process. Following this, therapeutic agents that are both antiresorptive and can stimulate osteoclast apoptosis will be discussed. Other bone therapeutic agents that are either antiresorptive or apoptotic, but not both, will be described. Finally, newer antiresorptive compounds that elicit apoptosis and could represent potential therapeutic agents will be noted.
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Affiliation(s)
- Paula H Stern
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA.
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256
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Yeo H, Beck LH, Thompson SR, Farach-Carson MC, McDonald JM, Clemens TL, Zayzafoon M. Conditional disruption of calcineurin B1 in osteoblasts increases bone formation and reduces bone resorption. J Biol Chem 2007; 282:35318-27. [PMID: 17884821 DOI: 10.1074/jbc.m702435200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We recently reported that the pharmacological inhibition of calcineurin (Cn) by low concentrations of cyclosporin A increases osteoblast differentiation in vitro and bone mass in vivo. To determine whether Cn exerts direct actions in osteoblasts, we generated mice lacking Cnb1 (Cn regulatory subunit) in osteoblasts (DeltaCnb1(OB)) using Cre-mediated recombination methods. Transgenic mice expressing Cre recombinase, driven by the human osteocalcin promoter, were crossed with homozygous mice that express loxP-flanked Cnb1 (Cnb1(f/f)). Microcomputed tomography analysis of tibiae at 3 months showed that DeltaCnb1(OB) mice had dramatic increases in bone mass compared with controls. Histomorphometric analyses showed significant increases in mineral apposition rate (67%), bone volume (32%), trabecular thickness (29%), and osteoblast numbers (68%) as well as a 40% decrease in osteoclast numbers as compared with the values from control mice. To delete Cnb1 in vitro, primary calvarial osteoblasts, harvested from Cnb1(f/f) mice, were infected with adenovirus expressing the Cre recombinase. Cre-expressing osteoblasts had a complete inhibition of Cnb1 protein levels but differentiated and mineralized more rapidly than control, green fluorescent protein-expressing cells. Deletion of Cnb1 increased expression of osteoprotegerin and decreased expression of RANKL. Co-culturing Cnb1-deficient osteoblasts with wild type osteoclasts demonstrated that osteoblasts lacking Cnb1 failed to support osteoclast differentiation in vitro. Taken together, our findings demonstrate that the inhibition of Cnb1 in osteoblasts increases bone mass by directly increasing osteoblast differentiation and indirectly decreasing osteoclastogenesis.
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Affiliation(s)
- Hyeonju Yeo
- Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama 35294-2182, USA
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257
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Canté-Barrett K, Winslow MM, Crabtree GR. Selective Role of NFATc3 in Positive Selection of Thymocytes. THE JOURNAL OF IMMUNOLOGY 2007; 179:103-10. [PMID: 17579027 DOI: 10.4049/jimmunol.179.1.103] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The four Ca(2+)-dependent NFATc proteins are both signal transducers and transcription factors that reside in the cytoplasm until dephosphorylation by calcineurin. Dephosphorylation exposes nuclear import sequences and sends NFATc proteins into the nucleus where they assemble with nuclear partners into NFAT transcription complexes. Recent genetic studies have indicated that calcineurin-NFAT signaling is a major determinant of vertebrate morphogenesis and development. Mice lacking calcineurin activity show a complete block in positive selection of CD4 and CD8 double-positive thymocytes, yet the role of the NFATc proteins in T cell development has been controversial. In this study, we address the requirement for NFATc3 in T cell development by generating NFATc3 conditional knockout mice. We show that specific deletion of NFATc3 in thymocytes causes a partial block at the double-negative stage 3 and also a partial block in positive selection. Furthermore, the defect does not become more pronounced when NFATc2 is also absent, consistent with the fact that NFATc2-null mice do not have a T cell developmental defect. Expression of a nuclear (and constitutively active) NFATc1 even at subphysiological levels can rescue the transition of double-negative to double-positive thymocytes in RAG-null mice, but is unable to rescue development of CD4 and CD8 single-positive cells. In addition to NFATc3, this suggests a role for NFATc1 in T cell development. Our studies indicate that the signals that direct positive selection likely use both NFATc1 and NFATc3 downstream of calcineurin.
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Affiliation(s)
- Kirsten Canté-Barrett
- Departments of Developmental Biology and Pathology, Howard Hughes Medical Institute, Stanford University, 279 Campus Drive, Stanford, CA 94305, USA
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258
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Pan M, Winslow MM, Chen L, Kuo A, Felsher D, Crabtree GR. Enhanced NFATc1 nuclear occupancy causes T cell activation independent of CD28 costimulation. THE JOURNAL OF IMMUNOLOGY 2007; 178:4315-21. [PMID: 17371988 DOI: 10.4049/jimmunol.178.7.4315] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
TCR signals induce the nuclear localization of NFATc proteins, which are removed from the nucleus after rephosphorylation by glycogen synthase kinase 3 and other kinases. Rapid nuclear export might allow continuous monitoring of receptor occupancy, making the transcriptional response proportional to the duration of TCR/CD28 signaling. To investigate this possibility, we analyzed mice in which T cells express a NFATc1 variant (NFATc1(nuc)) with serine-to-alanine changes at the glycogen synthase kinase 3 phosphorylation sites. NFATc1(nuc) T cells have constitutively nuclear NFATc1, enhanced T cell activation in vivo, and calcineurin-independent proliferation in vitro. NFATc1(nuc) T cells are hypersensitive to TCR/CD3 stimulation, resulting in enhanced proliferation and cytokine production that is independent of CD28 costimulation. These results support the notion that CD28 inhibits nuclear export of NFATc transcription factors. In addition, NFATc1(nuc) destabilizes a positive feedback loop in which NFATc1 activates its own transcription as well as its targets, such as CD40 ligand and Th1/Th2 cytokines.
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Affiliation(s)
- Minggui Pan
- Division of Oncology, Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA.
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259
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Penolazzi L, Zennaro M, Lambertini E, Tavanti E, Torreggiani E, Gambari R, Piva R. Induction of estrogen receptor alpha expression with decoy oligonucleotide targeted to NFATc1 binding sites in osteoblasts. Mol Pharmacol 2007; 71:1457-62. [PMID: 17389747 DOI: 10.1124/mol.107.034561] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The nuclear factor of activated T cell cytoplasmic 1 (NFATc1) is a member of the NFAT family and is strictly implicated in the growth and development of bone. Most studies have focused on the effects of NFATc1 activation on osteoclastogenesis. On the contrary, the specific roles of NFAT in osteoblast differentiation are not well understood and, in some instances, reports of its role are contradictory. In the present study, we demonstrated that NFATc1 was involved in the transcriptional regulation of human estrogen receptor alpha (ERalpha) gene in SaOS-2 osteoblastic like cells. NFATc1 was specifically recruited "in vivo" at C and F distal promoters of ERalpha gene. In addition, it is here identified as the negative transcription factor removed by the RA4-3'decoy oligonucleotide able to induce ERalpha expression in osteoblasts. Ca(2+)/calcineurin-NFAT-mediated signaling pathways and ERalpha-dependent signals are involved in diverse cellular reactions by regulating gene expression under both physiological and pathological conditions. Therefore, our data might be useful for proper manipulation of NFATc1- and ERalpha-mediated cellular reactions in different bone disorders, such as osteoporosis.
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Affiliation(s)
- Letizia Penolazzi
- Department of Biochemistry and Molecular Biology, Molecular Biology Section, Ferrara, Italy
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260
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Takayanagi H. Osteoimmunology: shared mechanisms and crosstalk between the immune and bone systems. Nat Rev Immunol 2007; 7:292-304. [PMID: 17380158 DOI: 10.1038/nri2062] [Citation(s) in RCA: 1349] [Impact Index Per Article: 74.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Osteoimmunology is an interdisciplinary research field focused on the molecular understanding of the interplay between the immune and skeletal systems. Although osteoimmunology started with the study of the immune regulation of osteoclasts, its scope has been extended to encompass a wide range of molecular and cellular interactions, including those between osteoblasts and osteoclasts, lymphocytes and osteoclasts, and osteoblasts and haematopoietic cells. Therefore, the two systems should be understood to be integrated and operating in the context of the 'osteoimmune' system, a heuristic concept that provides not only a framework for obtaining new insights by basic research, but also a scientific basis for the discovery of novel treatments for diseases related to both systems.
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Affiliation(s)
- Hiroshi Takayanagi
- Department of Cell Signaling, Graduate School, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo 113-8549, Japan.
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261
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Yeo H, Beck LH, McDonald JM, Zayzafoon M. Cyclosporin A elicits dose-dependent biphasic effects on osteoblast differentiation and bone formation. Bone 2007; 40:1502-16. [PMID: 17392048 PMCID: PMC1974856 DOI: 10.1016/j.bone.2007.02.017] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2006] [Revised: 01/19/2007] [Accepted: 02/12/2007] [Indexed: 11/22/2022]
Abstract
Cyclosporin A (CsA) is thought to prevent immune reactions after organ transplantation by inhibiting calcineurin (Cn) and its substrate, the Nuclear Factor of Activated T Cells (NFAT). A dichotomy exists in describing the effects of CsA on bone formation. The concept that the suppression of Cn/NFAT signaling by CsA inhibits bone formation is not entirely supported by many clinical reports and laboratory animal studies. Gender, dosage and basal inflammatory activity have all been suggested as explanations for these seemingly contradictory reports. Here we examine the effects of varying concentrations of CsA on bone formation and osteoblast differentiation and elucidate the role of NFATc1 in this response. We show that low concentrations of CsA (<1 microM in vitro and 35.5 nM in vivo) are anabolic as they increase bone formation, osteoblast differentiation, and bone mass, while high concentrations (>1 microM in vitro and in vivo) elicit an opposite and catabolic response. The overexpression of constitutively active NFATc1 inhibits osteoblast differentiation, and treatment with low concentrations of CsA does not ameliorate this inhibition. Treating osteoblasts with low concentrations of CsA (<1 microM) increases fra-2 gene expression and protein levels in a dose-dependent manner as well as AP-1 DNA-binding activity. Finally, NFATc1 silencing with siRNA increases Fra-2 expression, whereas NFATc1 overexpression inhibits Fra-2 expression. Therefore, NFATc1 negatively regulates osteoblast differentiation, and its specific inhibition may represent a viable anabolic therapy for osteoporosis.
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Affiliation(s)
- Hyeonju Yeo
- Department of Pathology, University of Alabama at Birmingham, 813 Shelby Biomedical Research Building, 1825 University Boulevard, Birmingham, AL 35294, USA
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262
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Wu H, Peisley A, Graef IA, Crabtree GR. NFAT signaling and the invention of vertebrates. Trends Cell Biol 2007; 17:251-60. [PMID: 17493814 DOI: 10.1016/j.tcb.2007.04.006] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Revised: 03/27/2007] [Accepted: 04/25/2007] [Indexed: 01/08/2023]
Abstract
The calcium/calcineurin-dependent NFATc family is thought to have arisen following the recombination of an ancient precursor with a Rel domain about 500 million years ago, producing a new group of signaling and transcription factors (the NFATc genes) found only in the genomes of vertebrates. Cell biological, genetic and biochemical evidence indicates that the circuitry of this pathway is well suited for intercalation with older pathways. We propose that this recombination enabled Ca(2+) signals to be redirected to a new transcriptional program, which provided part of the groundwork for vertebrate morphogenesis and organogenesis. This notion predicts that calcineurin-NFAT signaling would be essential for much of vertebrate development. We review recent evidence supporting this prediction and propose a systematic approach to explore aspects of vertebrate morphogenesis.
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Affiliation(s)
- Hai Wu
- Stanford University and the Howard Hughes Medical Institute, Department of Pathology, Beckman Center, Stanford, CA 94305, USA
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263
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Huang W, Yang S, Shao J, Li YP. Signaling and transcriptional regulation in osteoblast commitment and differentiation. FRONT BIOSCI-LANDMRK 2007; 12:3068-92. [PMID: 17485283 PMCID: PMC3571113 DOI: 10.2741/2296] [Citation(s) in RCA: 467] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The major event that triggers osteogenesis is the transition of mesenchymal stem cells into bone forming, differentiating osteoblast cells. Osteoblast differentiation is the primary component of bone formation, exemplified by the synthesis, deposition and mineralization of extracellular matrix. Although not well understood, osteoblast differentiation from mesenchymal stem cells is a well-orchestrated process. Recent advances in molecular and genetic studies using gene targeting in mouse enable a better understanding of the multiple factors and signaling networks that control the differentiation process at a molecular level. Osteoblast commitment and differentiation are controlled by complex activities involving signal transduction and transcriptional regulation of gene expression. We review Wnt signaling pathway and Runx2 regulation network, which are critical for osteoblast differentiation. Many other factors and signaling pathways have been implicated in regulation of osteoblast differentiation in a network manner, such as the factors Osterix, ATF4, and SATB2 and the TGF-beta, Hedgehog, FGF, ephrin, and sympathetic signaling pathways. This review summarizes the recent advances in the studies of signaling transduction pathways and transcriptional regulation of osteoblast cell lineage commitment and differentiation. The knowledge of osteoblast commitment and differentiation should be applied towards the development of new diagnostic and therapeutic alternatives for human bone diseases.
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Affiliation(s)
- Wei Huang
- College of Life Sciences, Zhejiang University, Hangzhou, China
| | - Shuying Yang
- Department of Cytokine Biology, Forsyth Institute, Harvard School of Dental Medicine, Boston, Massachusetts
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts
| | - Jianzhong Shao
- College of Life Sciences, Zhejiang University, Hangzhou, China
| | - Yi-Ping Li
- College of Life Sciences, Zhejiang University, Hangzhou, China
- Department of Cytokine Biology, Forsyth Institute, Harvard School of Dental Medicine, Boston, Massachusetts
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts
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264
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Riddle RC, Taylor AF, Rogers JR, Donahue HJ. ATP release mediates fluid flow-induced proliferation of human bone marrow stromal cells. J Bone Miner Res 2007; 22:589-600. [PMID: 17243863 DOI: 10.1359/jbmr.070113] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
UNLABELLED Oscillatory fluid flow induced the vesicular release of ATP from human BMSCs that directly contributes to the induction of BMSC proliferation. Degrading extracellular nucleotides prevents fluid flow-induced increases in intracellular calcium concentration, the activation of calcineurin, and the nuclear translocation of NFAT. INTRODUCTION Regulation of bone cell activity by autocrine/paracrine factors is a well-established mechanism by which skeletal homeostasis is regulated by mechanical signals. The release of extracellular nucleotides in particular has been shown to induce many of the responses thought to be necessary for load-induced bone formation. In these studies, we examined the effect of oscillatory fluid flow on the release of ATP from bone marrow stromal cells (BMSCs) and the effect of ATP release on BMSC proliferation and intracellular calcium signaling pathways. MATERIALS AND METHODS BMSCs were exposed to oscillatory fluid flow, and the concentration of ATP in conditioned media samples was determined using a luciferin:luciferase-based reaction. Western blot analysis was used to examine the expression of purinergic receptors. Using pharmacological antagonists of gap junction hemichannels and vesicular trafficking, we studied the mechanism of ATP release from BMSCs. Apyrase was used to study the effect of extracellular nucleotides on intracellular calcium concentration, calcineurin activity, and nuclear factor of activated T cells (NFAT) nuclear translocation. RESULTS AND CONCLUSIONS Fluid flow exposure induced the flow rate-dependent release of ATP from BMSCs that was attenuated by treatment with monensin and N-ethylmaleimide, suggesting a vesicular mechanism. Treating BMSCs with ATP, but not other nucleotides, increased cellular proliferation. Moreover, extracellular ATP was a prerequisite for fluid flow-induced increases in intracellular calcium concentration, activation of calcineurin, the nuclear translocation of NFATc1, and proliferation. These data indicate that ATP regulates not only osteoblastic and osteocytic cell behavior but also that of mesenchymal precursors and support our hypothesis that similar mechanotransduction mechanisms are activated by fluid flow in these cell types.
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Affiliation(s)
- Ryan C Riddle
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation, Pennsylvania State University College of Medicine, Milton S Hershey Medical Center, Hershey, PA 17033, USA
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265
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Saita Y, Takagi T, Kitahara K, Usui M, Miyazono K, Ezura Y, Nakashima K, Kurosawa H, Ishii S, Noda M. Lack of Schnurri-2 expression associates with reduced bone remodeling and osteopenia. J Biol Chem 2007; 282:12907-15. [PMID: 17311925 DOI: 10.1074/jbc.m611203200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Regulation of bone remodeling determines the levels of bone mass and its imbalance causes major skeletal diseases such as osteoporosis. A zinc finger protein, Schnurri-2 (SHN-2), was recently demonstrated to regulate bone morphogenetic protein-dependent adipogenesis and lymphogenesis. However, the role of SHN-2 in bone is not known. Here, we investigated the effects of Shn-2 deficiency on bone metabolism and cell function in Shn-2-null mice. Lack of SHN-2 expression reduced bone remodeling by suppressing both osteoblastic bone formation and osteoclastic bone resorption activities in vivo. Shn-2 deficiency suppressed osterix and osteocalcin expression as well as in vitro mineralization. Conversely, Shn-2 overexpression enhanced osteocalcin promoter activity and bone morphogenetic protein-dependent osteoblastic differentiation. Shn-2 deficiency suppressed Nfatc1 and c-fos expression leading to reduction of tartrate-resistant acid phosphatase-positive cell development in vivo as well as in the cultures of bone marrow cells. These studies demonstrate that SHN-2 regulates the activities of critical transcription factors required for normal bone remodeling.
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Affiliation(s)
- Yoshitomo Saita
- Department of Molecular Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo 101-0062, Japan
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266
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Thirunavukkarasu K, Pei Y, Moore TL, Wei T, Wang H, Chandrasekhar S. Regulation of NFATc2 gene expression by the transcription factor Runx2. Mol Biol Rep 2006; 34:1-10. [PMID: 17103021 DOI: 10.1007/s11033-006-9001-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2006] [Accepted: 08/21/2006] [Indexed: 11/30/2022]
Abstract
NFATc2 is a transcription factor that has been shown to function as a repressor of cartilage cell growth and differentiation in mice. In order to understand the transcriptional regulation of NFATc2 gene expression, we have cloned and characterized approximately 2.5 kb 5'-flanking regions of the mouse and human NFATc2 genes. Sequence analysis of the promoters revealed putative binding sites for the Runx family of transcription factors, of which one member, Runx2, plays a key role in chondrocyte maturation and osteoblast differentiation. Using promoter-reporter assays we have shown that Runx2 overexpression results in a significant increase in NFATc2 transactivation in fibroblastic, mesenchymal and chondrocytic cells. Runx2 overexpression also resulted in a substantial increase in endogenous NFATc2 mRNA levels in C3H10T1/2 mesenchymal cells implicating the NFATc2 gene as a potential downstream target of Runx2. Our results suggest that the role of Runx2 in promoting chondrocyte maturation and hypertrophy may be mediated, at least in part, via the stimulation of NFATc2 expression.
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Affiliation(s)
- Kannan Thirunavukkarasu
- Musculoskeletal Research, Lilly Research Labs, Eli Lilly and Company, Drop Code 0403, Indianapolis, IN 46285, USA.
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267
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Heit JJ, Apelqvist AA, Gu X, Winslow MM, Neilson JR, Crabtree GR, Kim SK. Calcineurin/NFAT signalling regulates pancreatic beta-cell growth and function. Nature 2006; 443:345-9. [PMID: 16988714 DOI: 10.1038/nature05097] [Citation(s) in RCA: 354] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Accepted: 07/18/2006] [Indexed: 01/28/2023]
Abstract
The growth and function of organs such as pancreatic islets adapt to meet physiological challenges and maintain metabolic balance, but the mechanisms controlling these facultative responses are unclear. Diabetes in patients treated with calcineurin inhibitors such as cyclosporin A indicates that calcineurin/nuclear factor of activated T-cells (NFAT) signalling might control adaptive islet responses, but the roles of this pathway in beta-cells in vivo are not understood. Here we show that mice with a beta-cell-specific deletion of the calcineurin phosphatase regulatory subunit, calcineurin b1 (Cnb1), develop age-dependent diabetes characterized by decreased beta-cell proliferation and mass, reduced pancreatic insulin content and hypoinsulinaemia. Moreover, beta-cells lacking Cnb1 have a reduced expression of established regulators of beta-cell proliferation. Conditional expression of active NFATc1 in Cnb1-deficient beta-cells rescues these defects and prevents diabetes. In normal adult beta-cells, conditional NFAT activation promotes the expression of cell-cycle regulators and increases beta-cell proliferation and mass, resulting in hyperinsulinaemia. Conditional NFAT activation also induces the expression of genes critical for beta-cell endocrine function, including all six genes mutated in hereditary forms of monogenic type 2 diabetes. Thus, calcineurin/NFAT signalling regulates multiple factors that control growth and hallmark beta-cell functions, revealing unique models for the pathogenesis and therapy of diabetes.
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Affiliation(s)
- Jeremy J Heit
- Department of Developmental Biology, Stanford University, Stanford, California 94305, USA
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