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Szrok-Jurga S, Czumaj A, Turyn J, Hebanowska A, Swierczynski J, Sledzinski T, Stelmanska E. The Physiological and Pathological Role of Acyl-CoA Oxidation. Int J Mol Sci 2023; 24:14857. [PMID: 37834305 PMCID: PMC10573383 DOI: 10.3390/ijms241914857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Revised: 09/27/2023] [Accepted: 09/30/2023] [Indexed: 10/15/2023] Open
Abstract
Fatty acid metabolism, including β-oxidation (βOX), plays an important role in human physiology and pathology. βOX is an essential process in the energy metabolism of most human cells. Moreover, βOX is also the source of acetyl-CoA, the substrate for (a) ketone bodies synthesis, (b) cholesterol synthesis, (c) phase II detoxication, (d) protein acetylation, and (d) the synthesis of many other compounds, including N-acetylglutamate-an important regulator of urea synthesis. This review describes the current knowledge on the importance of the mitochondrial and peroxisomal βOX in various organs, including the liver, heart, kidney, lung, gastrointestinal tract, peripheral white blood cells, and other cells. In addition, the diseases associated with a disturbance of fatty acid oxidation (FAO) in the liver, heart, kidney, lung, alimentary tract, and other organs or cells are presented. Special attention was paid to abnormalities of FAO in cancer cells and the diseases caused by mutations in gene-encoding enzymes involved in FAO. Finally, issues related to α- and ω- fatty acid oxidation are discussed.
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Affiliation(s)
- Sylwia Szrok-Jurga
- Department of Biochemistry, Faculty of Medicine, Medical University of Gdansk, 80-211 Gdansk, Poland; (S.S.-J.); (J.T.); (A.H.)
| | - Aleksandra Czumaj
- Department of Pharmaceutical Biochemistry, Faculty of Pharmacy, Medical University of Gdansk, 80-211 Gdansk, Poland;
| | - Jacek Turyn
- Department of Biochemistry, Faculty of Medicine, Medical University of Gdansk, 80-211 Gdansk, Poland; (S.S.-J.); (J.T.); (A.H.)
| | - Areta Hebanowska
- Department of Biochemistry, Faculty of Medicine, Medical University of Gdansk, 80-211 Gdansk, Poland; (S.S.-J.); (J.T.); (A.H.)
| | - Julian Swierczynski
- Institue of Nursing and Medical Rescue, State University of Applied Sciences in Koszalin, 75-582 Koszalin, Poland;
| | - Tomasz Sledzinski
- Department of Pharmaceutical Biochemistry, Faculty of Pharmacy, Medical University of Gdansk, 80-211 Gdansk, Poland;
| | - Ewa Stelmanska
- Department of Biochemistry, Faculty of Medicine, Medical University of Gdansk, 80-211 Gdansk, Poland; (S.S.-J.); (J.T.); (A.H.)
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2
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Sakuraba K, Krishnamurthy A, Sun J, Zheng X, Xu C, Peng B, Engström M, Jakobsson PJ, Wermeling F, Catrina S, Grönwall C, Catrina AI, Réthi B. Autoantibodies targeting malondialdehyde-modifications in rheumatoid arthritis regulate osteoclasts via inducing glycolysis and lipid biosynthesis. J Autoimmun 2022; 133:102903. [PMID: 36108504 DOI: 10.1016/j.jaut.2022.102903] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 08/16/2022] [Accepted: 08/23/2022] [Indexed: 12/13/2022]
Abstract
Proteins subjected to post-translational modifications, such as citrullination, carbamylation, acetylation or malondialdehyde (MDA)-modification are targeted by autoantibodies in seropositive rheumatoid arthritis (RA). Epidemiological and experimental studies have both suggested the pathogenicity of such humoral autoimmunity, however, molecular mechanisms triggered by anti-modified protein antibodies have remained to be identified. Here we describe in detail the pathways induced by anti-MDA modified protein antibodies that were obtained from synovial B cells of RA patients and that possessed robust osteoclast stimulatory potential and induced bone erosion in vivo. Anti-MDA antibodies boosted glycolysis in developing osteoclasts via an FcγRI, HIF-1α and MYC-dependent mechanism and subsequently increased oxidative phosphorylation. Osteoclast development required robust phosphoglyceride and triacylglyceride biosynthesis, which was also enhanced by anti-MDA by modulating citrate production and expression of the glycerol-3-phosphate dehydrogenase 1 (GPD1) and glycerol-3-phosphate acyltransferase 2 (GPAT2) genes. In summary, we described novel metabolic pathways instrumental for osteoclast differentiation, which were targeted by anti-MDA antibodies, accelerating bone erosion, a central component of RA pathogenesis.
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Affiliation(s)
- Koji Sakuraba
- Division of Rheumatology, Department of Medicine/Solna, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden; Department of Orthopedic Surgery and Rheumatology, Clinical Research Center, National Hospital Organization Kyushu Medical Center, Fukuoka, Japan
| | - Akilan Krishnamurthy
- Division of Rheumatology, Department of Medicine/Solna, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden
| | - Jitong Sun
- Division of Rheumatology, Department of Medicine/Solna, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden
| | - Xiaowei Zheng
- Department of Molecular Medicine and Surgery, Karolinska Institutet and Center for Diabetes, Academic Specialist Centrum, Stockholm, Sweden
| | - Cheng Xu
- Department of Molecular Medicine and Surgery, Karolinska Institutet and Center for Diabetes, Academic Specialist Centrum, Stockholm, Sweden
| | - Bing Peng
- Division of Rheumatology, Department of Medicine/Solna, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden
| | - Marianne Engström
- Division of Rheumatology, Department of Medicine/Solna, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden
| | - Per-Johan Jakobsson
- Division of Rheumatology, Department of Medicine/Solna, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden
| | - Fredrik Wermeling
- Division of Rheumatology, Department of Medicine/Solna, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden
| | - Sergiu Catrina
- Department of Molecular Medicine and Surgery, Karolinska Institutet and Center for Diabetes, Academic Specialist Centrum, Stockholm, Sweden
| | - Caroline Grönwall
- Division of Rheumatology, Department of Medicine/Solna, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden
| | - Anca I Catrina
- Division of Rheumatology, Department of Medicine/Solna, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden
| | - Bence Réthi
- Division of Rheumatology, Department of Medicine/Solna, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden.
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3
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Kushwaha P, Alekos NS, Kim SP, Li Z, Wolfgang MJ, Riddle RC. Mitochondrial fatty acid β-oxidation is important for normal osteoclast formation in growing female mice. Front Physiol 2022; 13:997358. [PMID: 36187756 PMCID: PMC9515402 DOI: 10.3389/fphys.2022.997358] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 08/22/2022] [Indexed: 12/03/2022] Open
Abstract
Skeletal remodeling is an energy demanding process that is linked to nutrient availability and the levels of metabolic hormones. While recent studies have examined the metabolic requirements of bone formation by osteoblasts, much less is known about the energetic requirements of bone resorption by osteoclasts. The abundance of mitochondria in mature osteoclasts suggests that the production of an acidified micro-environment conducive to the ionization of hydroxyapatite, secretion of matrix-degrading enzymes, and motility during resorption requires significant energetic capacity. To investigate the contribution of mitochondrial long chain fatty acid β-oxidation to osteoclast development, we disrupted the expression of carnitine palmitoyltransferase-2 (Cpt2) in myeloid-lineage cells. Fatty acid oxidation increases dramatically in bone marrow cultures stimulated with RANKL and M-CSF and microCT analysis revealed that the genetic inhibition of long chain fatty acid oxidation in osteoclasts significantly increases trabecular bone volume in female mice secondary to reduced osteoclast numbers. In line with these data, osteoclast precursors isolated from Cpt2 mutants exhibit reduced capacity to form large-multinucleated osteoclasts, which was not rescued by exogenous glucose or pyruvate, and signs of an energetic stress response. Together, our data demonstrate that mitochondrial long chain fatty acid oxidation by the osteoclast is required for normal bone resorption as its inhibition produces an intrinsic defect in osteoclast formation.
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Affiliation(s)
- Priyanka Kushwaha
- Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Nathalie S. Alekos
- Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Soohyun P. Kim
- Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Zhu Li
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Michael J. Wolfgang
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Ryan C. Riddle
- Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, United States,Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD, United States,Baltimore Veterans Administration Medical Center, Baltimore, MD, United States,*Correspondence: Ryan C. Riddle,
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4
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Wculek SK, Dunphy G, Heras-Murillo I, Mastrangelo A, Sancho D. Metabolism of tissue macrophages in homeostasis and pathology. Cell Mol Immunol 2022; 19:384-408. [PMID: 34876704 PMCID: PMC8891297 DOI: 10.1038/s41423-021-00791-9] [Citation(s) in RCA: 121] [Impact Index Per Article: 60.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 09/25/2021] [Indexed: 02/06/2023] Open
Abstract
Cellular metabolism orchestrates the intricate use of tissue fuels for catabolism and anabolism to generate cellular energy and structural components. The emerging field of immunometabolism highlights the importance of cellular metabolism for the maintenance and activities of immune cells. Macrophages are embryo- or adult bone marrow-derived leukocytes that are key for healthy tissue homeostasis but can also contribute to pathologies such as metabolic syndrome, atherosclerosis, fibrosis or cancer. Macrophage metabolism has largely been studied in vitro. However, different organs contain diverse macrophage populations that specialize in distinct and often tissue-specific functions. This context specificity creates diverging metabolic challenges for tissue macrophage populations to fulfill their homeostatic roles in their particular microenvironment and conditions their response in pathological conditions. Here, we outline current knowledge on the metabolic requirements and adaptations of macrophages located in tissues during homeostasis and selected diseases.
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Affiliation(s)
- Stefanie K Wculek
- Immunobiology Laboratory, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, Madrid, 28029, Spain.
| | - Gillian Dunphy
- Immunobiology Laboratory, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, Madrid, 28029, Spain
| | - Ignacio Heras-Murillo
- Immunobiology Laboratory, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, Madrid, 28029, Spain
| | - Annalaura Mastrangelo
- Immunobiology Laboratory, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, Madrid, 28029, Spain
| | - David Sancho
- Immunobiology Laboratory, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, Madrid, 28029, Spain.
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5
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Da W, Tao L, Zhu Y. The Role of Osteoclast Energy Metabolism in the Occurrence and Development of Osteoporosis. Front Endocrinol (Lausanne) 2021; 12:675385. [PMID: 34054735 PMCID: PMC8150001 DOI: 10.3389/fendo.2021.675385] [Citation(s) in RCA: 57] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 04/29/2021] [Indexed: 12/14/2022] Open
Abstract
In recent decades, the mechanism underlying bone metabolic disorders based on energy metabolism has been heavily researched. Bone resorption by osteoclasts plays an important role in the occurrence and development of osteoporosis. However, the mechanism underlying the osteoclast energy metabolism disorder that interferes with bone homeostasis has not been determined. Bone resorption by osteoclasts is a process that consumes large amounts of adenosine triphosphate (ATP) produced by glycolysis and oxidative phosphorylation. In addition to glucose, fatty acids and amino acids can also be used as substrates to produce energy through oxidative phosphorylation. In this review, we summarize and analyze the energy-based phenotypic changes, epigenetic regulation, and coupling with systemic energy metabolism of osteoclasts during the development and progression of osteoporosis. At the same time, we propose a hypothesis, the compensatory recovery mechanism (involving the balance between osteoclast survival and functional activation), which may provide a new approach for the treatment of osteoporosis.
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Affiliation(s)
| | - Lin Tao
- Department of Orthopedics, The First Hospital of China Medical University, Shenyang, China
| | - Yue Zhu
- Department of Orthopedics, The First Hospital of China Medical University, Shenyang, China
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6
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Bellissimo MP, Roberts JL, Jones DP, Liu KH, Taibl KR, Uppal K, Weitzmann MN, Pacifici R, Drissi H, Ziegler TR, Alvarez JA. Metabolomic Associations with Serum Bone Turnover Markers. Nutrients 2020; 12:nu12103161. [PMID: 33081124 PMCID: PMC7602719 DOI: 10.3390/nu12103161] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 10/13/2020] [Accepted: 10/14/2020] [Indexed: 12/21/2022] Open
Abstract
Bone is a dynamic tissue that is in a constant state of remodeling. Bone turnover markers (BTMs), procollagen type I N-terminal propeptide (P1NP) and C-terminal telopeptides of type I collagen (CTX), provide sensitive measures of bone formation and resorption, respectively. This study used ultra-high-resolution metabolomics (HRM) to determine plasma metabolic pathways and targeted metabolites related to the markers of bone resorption and formation in adults. This cross-sectional clinical study included 34 adults (19 females, mean 27.8 years), without reported illnesses, recruited from a US metropolitan area. Serum BTM levels were quantified by an ELISA. Plasma HRM utilized dual-column liquid chromatography and mass spectrometry to identify metabolites and metabolic pathways associated with BTMs. Metabolites significantly associated with P1NP (p < 0.05) were significantly enriched in pathways linked to the TCA cycle, pyruvate metabolism, and metabolism of B vitamins important for energy production (e.g., niacin, thiamin). Other nutrition-related metabolic pathways associated with P1NP were amino acid (proline, arginine, glutamate) and vitamin C metabolism, which are important for collagen formation. Metabolites associated with CTX levels (p < 0.05) were enriched within lipid and fatty acid beta-oxidation metabolic pathways, as well as fat-soluble micronutrient pathways including, vitamin D metabolism, vitamin E metabolism, and bile acid biosynthesis. P1NP and CTX were significantly related to microbiome-related metabolites (p < 0.05). Macronutrient-related pathways including lipid, carbohydrate, and amino acid metabolism, as well as several gut microbiome-derived metabolites were significantly related to BTMs. Future research should compare metabolism BTMs relationships reported here to aging and clinical populations to inform targeted therapeutic interventions.
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Affiliation(s)
- Moriah P. Bellissimo
- Division of Endocrinology, Metabolism and Lipids, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA; (K.R.T.); (M.N.W.); (R.P.); (T.R.Z.); (J.A.A.)
- Emory Center for Clinical and Molecular Nutrition, Emory University, Atlanta, GA 30322, USA;
- Correspondence:
| | - Joseph L. Roberts
- Department of Orthopaedics, Emory University School of Medicine, Atlanta, GA 30322, USA; (J.L.R.); (H.D.)
- Atlanta Department of Veterans Affairs Medical Center, Decatur, GA 30033, USA
| | - Dean P. Jones
- Emory Center for Clinical and Molecular Nutrition, Emory University, Atlanta, GA 30322, USA;
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA; (K.H.L.); (K.U.)
| | - Ken H. Liu
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA; (K.H.L.); (K.U.)
| | - Kaitlin R. Taibl
- Division of Endocrinology, Metabolism and Lipids, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA; (K.R.T.); (M.N.W.); (R.P.); (T.R.Z.); (J.A.A.)
| | - Karan Uppal
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA; (K.H.L.); (K.U.)
| | - M. Neale Weitzmann
- Division of Endocrinology, Metabolism and Lipids, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA; (K.R.T.); (M.N.W.); (R.P.); (T.R.Z.); (J.A.A.)
- Atlanta Department of Veterans Affairs Medical Center, Decatur, GA 30033, USA
- Emory Microbiome Research Center, Emory University, Atlanta, GA 30322, USA
| | - Roberto Pacifici
- Division of Endocrinology, Metabolism and Lipids, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA; (K.R.T.); (M.N.W.); (R.P.); (T.R.Z.); (J.A.A.)
- Emory Microbiome Research Center, Emory University, Atlanta, GA 30322, USA
| | - Hicham Drissi
- Department of Orthopaedics, Emory University School of Medicine, Atlanta, GA 30322, USA; (J.L.R.); (H.D.)
- Atlanta Department of Veterans Affairs Medical Center, Decatur, GA 30033, USA
| | - Thomas R. Ziegler
- Division of Endocrinology, Metabolism and Lipids, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA; (K.R.T.); (M.N.W.); (R.P.); (T.R.Z.); (J.A.A.)
- Emory Center for Clinical and Molecular Nutrition, Emory University, Atlanta, GA 30322, USA;
- Atlanta Department of Veterans Affairs Medical Center, Decatur, GA 30033, USA
- Emory Microbiome Research Center, Emory University, Atlanta, GA 30322, USA
| | - Jessica A. Alvarez
- Division of Endocrinology, Metabolism and Lipids, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA; (K.R.T.); (M.N.W.); (R.P.); (T.R.Z.); (J.A.A.)
- Emory Center for Clinical and Molecular Nutrition, Emory University, Atlanta, GA 30322, USA;
- Emory Microbiome Research Center, Emory University, Atlanta, GA 30322, USA
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7
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Sirtuin 3 deficiency does not impede digit regeneration in mice. Sci Rep 2019; 9:16491. [PMID: 31712596 PMCID: PMC6848098 DOI: 10.1038/s41598-019-52921-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 10/25/2019] [Indexed: 12/11/2022] Open
Abstract
The mitochondrial deacetylase sirtuin 3 (SIRT3) is thought to be one of the main contributors to metabolic flexibility-promoting mitochondrial energy production and maintaining homeostasis. In bone, metabolic profiles are tightly regulated and the loss of SIRT3 has deleterious effects on bone volume in vivo and on osteoblast differentiation in vitro. Despite the prominent role of this protein in bone stem cell proliferation, metabolic activity, and differentiation, the importance of SIRT3 for regeneration after bone injury has never been reported. We show here, using the mouse digit amputation model, that SIRT3 deficiency has no impact on the regenerative capacity and architecture of bone and soft tissue. Regeneration occurs in SIRT3 deficient mice in spite of the reduced oxidative metabolic profile of the periosteal cells. These data suggest that bone regeneration, in contrast to homeostatic bone turnover, is not reliant upon active SIRT3, and our results highlight the need to examine known roles of SIRT3 in the context of injury.
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8
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Abstract
The adult human skeleton is a multifunctional organ undergoing constant remodeling through the opposing activities of the bone-resorbing osteoclast and the bone-forming osteoblast. The exquisite balance between bone resorption and bone formation is responsible for bone homeostasis in healthy adults. However, evidence has emerged that such a balance is likely disrupted in diabetes where systemic glucose metabolism is dysregulated, resulting in increased bone frailty and osteoporotic fractures. These findings therefore underscore the significance of understanding the role and regulation of glucose metabolism in bone under both normal and pathological conditions. Recent studies have shed new light on the metabolic plasticity and the critical functions of glucose metabolism during osteoclast and osteoblast differentiation. Moreover, these studies have begun to identify intersections between glucose metabolism and the growth factors and transcription factors previously known to regulate osteoblasts and osteoclasts. Here we summarize the current knowledge in the nascent field, and suggest that a fundamental understanding of glucose metabolic pathways in the critical bone cell types may open new avenues for developing novel bone therapeutics.
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Affiliation(s)
- Courtney M Karner
- Department of Orthopaedic Surgery, Duke Orthopaedic Cellular, Developmental, and Genome Laboratories, Department of Cell Biology, Duke University School of Medicine, Durham, NC 27710, USA.
| | - Fanxin Long
- Department of Orthopaedic Surgery, Department of Developmental Biology, Washington University School of Medicine, St Louis, MO 63131, USA.
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9
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Arnett TR, Orriss IR. Metabolic properties of the osteoclast. Bone 2018; 115:25-30. [PMID: 29274806 DOI: 10.1016/j.bone.2017.12.021] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 12/20/2017] [Accepted: 12/20/2017] [Indexed: 01/15/2023]
Abstract
Osteoclasts are defined as cells capable of excavating 3-dimensional resorption pits in bone and other mineralised tissues. They are derived from the differentiation/fusion of promonocytic precursors, and are usually large, multinucleated cells. In common with other cells from this myeloid lineage such as macrophages and dendritic cells, they are adapted to function in hypoxic, acidic environments. The process of bone resorption is rapid and is presumably highly energy-intensive, since osteoclasts must actively extrude protons to dissolve hydroxyapatite mineral, whilst secreting cathepsin K to degrade collagen, as well as maintaining a high degree of motility. Osteoclasts are well known to contain abundant mitochondria but they are also able to rely on glycolytic (anaerobic) metabolism to generate the ATP needed to power their activity. Their primary extracellular energy source appears to be glucose. Excessive accumulation of mitochondrial reactive oxygen species in osteoclasts during extended periods of high activity in oxygen-poor environments may promote apoptosis and help to limit bone resorption - a trajectory that could be termed "live fast, die young". In general, however, the metabolism of osteoclasts remains a poorly-investigated area, not least because of the technical challenges of studying actively resorbing cells in appropriate conditions.
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Affiliation(s)
- Timothy R Arnett
- Department of Cell & Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK.
| | - Isabel R Orriss
- Department of Comparative Biomedical Sciences, Royal Veterinary College, Royal College Street, London NW1 0TU, UK.
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10
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Suh KS, Chon S, Jung WW, Choi EM. Effects of methylglyoxal on RANKL-induced osteoclast differentiation in RAW264.7 cells. Chem Biol Interact 2018; 296:18-25. [PMID: 30217477 DOI: 10.1016/j.cbi.2018.09.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 07/27/2018] [Accepted: 09/11/2018] [Indexed: 12/20/2022]
Abstract
Methylglyoxal (MG) is a reactive dicarbonyl compound produced by glycolytic processing, which has been identified as a precursor of advanced glycation end products. Elevated MG levels in patients with diabetes are believed to contribute to diabetic complications, including bone defects. The objective of this study was to evaluate the effect of MG on RANKL-induced osteoclast differentiation in RAW264.7 cells, a murine macrophage cell line. RAW264.7 cells were cultured in medium containing 50 ng/mL RANKL and different concentrations of MG. Tartrate-resistant acid phosphatase (TRAP) activity and osteoclast bone resorbing activity were assessed and changes in intracellular calcium concentration, mitochondrial mass, mitochondrial membrane potential, and glyoxalase I level were examined. In addition, real-time RT-PCR assay was used to analyse osteoclast-associated genes. MG markedly inhibited RANKL-induced TRAP activity. MG treatment resulted in a significant decrease in intracellular calcium concentration, mitochondrial mass, mitochondrial membrane potential, and glyoxalase I level during osteoclastogenesis. In addition, MG increased the formation of mitochondrial superoxide. Quantitative reverse transcriptase-polymerase chain reaction revealed increased expression of the TRAF6, GAB2, ERK1, c-Fos, NFATc1, CLCN7, and OSTM1 genes, decreased expression of TCIRG and carbonic anhydrase II, and unchanged expression of cathepsin K and MMP-9 upon MG treatment. MG had no effect on the bone resorbing activity of osteoclasts. Our findings indicate that MG inhibits TRAP and glyoxalase I activity and impairs mitochondrial function in osteoclasts. Further validation of the underlying pathway is necessary.
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Affiliation(s)
- Kwang Sik Suh
- Department of Endocrinology & Metabolism, School of Medicine, Kyung Hee University, 1, Hoegi-dong, Dongdaemun-gu, Seoul, 02447, Republic of Korea
| | - Suk Chon
- Department of Endocrinology & Metabolism, School of Medicine, Kyung Hee University, 1, Hoegi-dong, Dongdaemun-gu, Seoul, 02447, Republic of Korea
| | - Woon-Won Jung
- Department of Biomedical Laboratory Science, College of Health Sciences, Cheongju University, Cheongju, Chungbuk, 28503, Republic of Korea
| | - Eun Mi Choi
- Department of Endocrinology & Metabolism, School of Medicine, Kyung Hee University, 1, Hoegi-dong, Dongdaemun-gu, Seoul, 02447, Republic of Korea.
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Abstract
The rising incidence of metabolic diseases worldwide has prompted renewed interest in the study of intermediary metabolism and cellular bioenergetics. The application of modern biochemical methods for quantitating fuel substrate metabolism with advanced mouse genetic approaches has greatly increased understanding of the mechanisms that integrate energy metabolism in the whole organism. Examination of the intermediary metabolism of skeletal cells has been sparked by a series of unanticipated observations in genetically modified mice that suggest the existence of novel endocrine pathways through which bone cells communicate their energy status to other centers of metabolic control. The recognition of this expanded role of the skeleton has in turn led to new lines of inquiry directed at defining the fuel requirements and bioenergetic properties of bone cells. This article provides a comprehensive review of historical and contemporary studies on the metabolic properties of bone cells and the mechanisms that control energy substrate utilization and bioenergetics. Special attention is devoted to identifying gaps in our current understanding of this new area of skeletal biology that will require additional research to better define the physiological significance of skeletal cell bioenergetics in human health and disease.
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Affiliation(s)
- Ryan C Riddle
- Department of Orthopaedic Surgery, The Johns Hopkins University, Baltimore, Maryland; and The Baltimore Veterans Administration Medical Center, Baltimore, Maryland
| | - Thomas L Clemens
- Department of Orthopaedic Surgery, The Johns Hopkins University, Baltimore, Maryland; and The Baltimore Veterans Administration Medical Center, Baltimore, Maryland
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12
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13
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Xiong Q, Zhang L, Zhan S, Ge W, Tang P. Investigation of proteome changes in osteoclastogenesis in low serum culture system using quantitative proteomics. Proteome Sci 2016; 14:8. [PMID: 27034619 PMCID: PMC4815185 DOI: 10.1186/s12953-016-0097-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Accepted: 03/24/2016] [Indexed: 12/31/2022] Open
Abstract
Background RAW 264.7 cells can differentiate into osteoclasts when cultured in medium supplemented with 1 % FBS. However, the proteomic changes in the development of RAW 264.7 cells into osteoclasts in low serum culture system have not been elucidated. Therefore, we conducted quantitative proteomics analysis to investigate proteomic changes during osteoclastogenesis in low serum culture system. Results Our study confirmed that mature multinucleated osteoclasts were generated in a low serum culture system, validated by upregulated expression of 15 characteristic marker proteins, including TRAP, CTSK, MMP9, V-ATPase and ITGAV. Proteomics results demonstrated that 549 proteins expressed differentially in osteoclastogenesis in low serum culture system. In-depth bioinformatics analysis suggested that the differentially expressed proteins were mainly involved in mitochondrial activities and energy metabolism, including the electron transport chain pathway, TCA cycle pathway, mitochondrial LC-fatty acid beta-oxidation pathway and fatty acid biosynthesis pathway. The data have been deposited to the ProteomeXchange with identifier PXD001935. Conclusion Osteoclast formation is an ATP consuming procedure, whether occurring in a low serum culture system or a conventional culture system. In contrast to osteoclasts formed in conventional culture system, the fatty acid biosynthesis pathway was upregulated in osteoclasts cultured in low serum condition. Electronic supplementary material The online version of this article (doi:10.1186/s12953-016-0097-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Qi Xiong
- Department of Orthopedics, General Hospital of Chinese PLA, Fuxing Road 28#, Haidian District, Beijing, 100853 China
| | - Lihai Zhang
- Department of Orthopedics, General Hospital of Chinese PLA, Fuxing Road 28#, Haidian District, Beijing, 100853 China
| | - Shaohua Zhan
- National Key Laboratory of Medical Molecular Biology & Department of Immunology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, DongdanSantiao 5#, Dongcheng District, Beijing, 100005 China
| | - Wei Ge
- National Key Laboratory of Medical Molecular Biology & Department of Immunology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, DongdanSantiao 5#, Dongcheng District, Beijing, 100005 China
| | - Peifu Tang
- Department of Orthopedics, General Hospital of Chinese PLA, Fuxing Road 28#, Haidian District, Beijing, 100853 China
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14
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Giuliano S, Agresta AM, De Palma A, Viglio S, Mauri P, Fumagalli M, Iadarola P, Montalbetti L, Salvini R, Bardoni A. Proteomic analysis of lymphoblastoid cells from Nasu-Hakola patients: a step forward in our understanding of this neurodegenerative disorder. PLoS One 2014; 9:e110073. [PMID: 25470616 PMCID: PMC4254282 DOI: 10.1371/journal.pone.0110073] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 09/05/2014] [Indexed: 12/31/2022] Open
Abstract
Nasu-Hakola disease (NHD) is a recessively inherited rare disorder characterized by a combination of neuropsychiatric and bone symptoms which, while being unique to this disease, do not provide a rationale for the unambiguous identification of patients. These individuals, in fact, are likely to go unrecognized either because they are considered to be affected by other kinds of dementia or by fibrous dysplasia of bone. Given that dementia in NHD has much in common with Alzheimer’s disease and other neurodegenerative disorders, it cannot be expected to achieve the differential diagnosis of this disease without performing a genetic analysis. Under this scenario, the availability of protein biomarkers would indeed provide a novel context to facilitate interpretation of symptoms and to make the precise identification of this disease possible. The work here reported was designed to generate, for the first time, protein profiles of lymphoblastoid cells from NHD patients. Two-dimensional electrophoresis (2-DE) and nano liquid chromatography-tandem mass spectrometry (nLC-MS/MS) have been applied to all components of an Italian family (seven subjects) and to five healthy subjects included as controls. Comparative analyses revealed differences in the expression profile of 21 proteins involved in glucose metabolism and information pathways as well as in stress responses.
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Affiliation(s)
- Serena Giuliano
- Department of Molecular Medicine, Biochemistry Unit, University of Pavia, Pavia, Italy; Laboratoire d'excellence-Ion channel science and therapeutics, UMR, CNRS, Nice, France
| | - Anna Maria Agresta
- Institute for Biochemical Technologies, Proteomics and Metabolomics Unit, National Research Council, Segrate (Milano), Italy
| | - Antonella De Palma
- Institute for Biochemical Technologies, Proteomics and Metabolomics Unit, National Research Council, Segrate (Milano), Italy
| | - Simona Viglio
- Department of Molecular Medicine, Biochemistry Unit, University of Pavia, Pavia, Italy
| | - Pierluigi Mauri
- Institute for Biochemical Technologies, Proteomics and Metabolomics Unit, National Research Council, Segrate (Milano), Italy
| | - Marco Fumagalli
- Department of Biology and Biotechnologies, Biochemistry Unit, University of Pavia, Pavia, Italy
| | - Paolo Iadarola
- Department of Biology and Biotechnologies, Biochemistry Unit, University of Pavia, Pavia, Italy
| | - Lorenza Montalbetti
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Roberta Salvini
- Department of Molecular Medicine, Biochemistry Unit, University of Pavia, Pavia, Italy
| | - Anna Bardoni
- Department of Molecular Medicine, Biochemistry Unit, University of Pavia, Pavia, Italy
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15
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Morten KJ, Badder L, Knowles HJ. Differential regulation of HIF-mediated pathways increases mitochondrial metabolism and ATP production in hypoxic osteoclasts. J Pathol 2013; 229:755-64. [PMID: 23303559 PMCID: PMC3618370 DOI: 10.1002/path.4159] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Revised: 12/02/2012] [Accepted: 12/21/2012] [Indexed: 12/14/2022]
Abstract
Inappropriate osteoclast activity instigates pathological bone loss in rheumatoid arthritis. We have investigated how osteoclasts generate sufficient ATP for the energy-intensive process of bone resorption in the hypoxic microenvironment associated with this rheumatic condition. We show that in human osteoclasts differentiated from CD14+ monocytes, hypoxia (24 h, 2% O2): (a) increases ATP production and mitochondrial electron transport chain activity (Alamar blue, O2 consumption); (b) increases glycolytic flux (glucose consumption, lactate production); and (c) increases glutamine consumption. We demonstrate that glucose, rather than glutamine, is necessary for the hypoxic increase in ATP production and also for cell survival in hypoxia. Using siRNA targeting specific isoforms of the hypoxia-inducible transcription factor HIF (HIF-1α, HIF-2α), we show that employment of selected components of the HIF-1α-mediated metabolic switch to anaerobic respiration enables osteoclasts to rapidly increase ATP production in hypoxia, while at the same time compromising long-term survival. We propose this atypical HIF-driven metabolic pathway to be an adaptive mechanism to permit rapid bone resorption in the short term while ensuring curtailment of the process in the absence of re-oxygenation. Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
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Affiliation(s)
- Karl J Morten
- Nuffield Department of Obstetrics and Gynaecology, The Womens Centre, John Radcliffe Hospital, Oxford, UK
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16
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Influence of omega-6 PUFA arachidonic acid and bone marrow adipocytes on metastatic spread from prostate cancer. Br J Cancer 2009; 102:403-13. [PMID: 19997104 PMCID: PMC2816655 DOI: 10.1038/sj.bjc.6605481] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Prostate cancer (CaP) preferentially metastasises to the bone, and we have previously shown that the poly-unsaturated fatty acid (PUFA) arachidonic acid (AA) is a potent stimulator of CaP invasion. Here we present that AA promotes CaP invasion by inducing bone marrow adipocyte formation. METHODS Boyden invasion-chamber assays assessed the ability of dietary oils, their PUFA components, and specific PUFA-loaded adipocytes to induce PC-3 invasion. Lipid transfer and metabolism was followed using deuterated AA and Fourier Transform Infrared spectroscopy (FTIR). RESULTS Poly-unsaturated fatty acid constituents, but not their corresponding dietary oils, induced PC-3 invasion. PUFAs induce bone marrow adipocyte (BM-Ad) differentiation with AA inducing higher levels of BM-Ad differentiation, as compared with other PUFAs (3998+/-514.4 vs 932+/-265.8; P=0.00002), which stimulated greater PC-3 invasion than free AA (22 408.5+/-607.4 vs 16 236+/-313.9; P=0.01111) or adipocytes generated in the presence of other PUFAs. In bone marrow co-culture PC-3 and BM-Ad interactions result in direct uptake and metabolism of AA by PC-3 cells, destruction of the adipocyte and subsequent formation of a bone metastasis. CONCLUSION The data supports the hypothesis that AA not only promotes CaP invasion, it also prepares the 'soil', making it more supportive for implantation and propagation of the migrating metastatic cell.
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17
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Kim JM, Jeong D, Kang HK, Jung SY, Kang SS, Min BM. Osteoclast precursors display dynamic metabolic shifts toward accelerated glucose metabolism at an early stage of RANKL-stimulated osteoclast differentiation. Cell Physiol Biochem 2007; 20:935-46. [PMID: 17982276 DOI: 10.1159/000110454] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/22/2007] [Indexed: 12/23/2022] Open
Abstract
Mature osteoclasts have an increased citric acid cycle and mitochondrial respiration to generate high ATP production and ultimately lead to bone resorption. However, changes in metabolic pathways during osteoclast differentiation have not been fully illustrated. We report that glycolysis and oxidative phosphorylation characterized by glucose and oxygen consumption as well as lactate production were increased during receptor activator of nuclear factor-kappaB ligand (RANKL)-induced osteoclastogenesis from RAW264.7 and bone marrow-derived macrophage cells. Cell proliferation and differentiation varied according to glucose concentrations (0 to 100 mM). Maximal cell growth occurred at 20 mM glucose concentration and differentiation occurred at 5 mM concentration. Despite the similar growth rates exhibited when cultured cells were exposed to either 5 mM or 40 mM glucose, their differentiation was markedly decreased in high glucose concentrations. This finding suggests the possibility that osteoclastogenesis could be regulated by changes in metabolic substrate concentrations. To further address the effect of metabolic shift on osteoclastogenesis, we exposed cultured cells to pyruvate, which is capable of promoting mitochondrial respiration. Treatment of pyruvate synergistically increased osteoclastogenesis through the activation of RANKL-stimulated signals (ERK and JNK). We also found that osteoclastogenesis was retarded by blocking ATP production with either the inhibitors of mitochondrial complexes, such as rotenone and antimycin A, or the inhibitor of ATP synthase, oligomycin. Taken together, these results indicate that glucose metabolism during osteoclast differentiation is accelerated and that a metabolic shift towards mitochondrial respiration allows high ATP production and induces enhanced osteoclast differentiation.
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Affiliation(s)
- Jin-Man Kim
- Department of Oral Biochemistry and Craniomaxillofacial Reconstructive Sciences, Dental Research Institute, and BK21 CLS, Seoul National University School of Dentistry, Seoul, Korea
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18
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Wezeman FH, Gong Z. Adipogenic effect of alcohol on human bone marrow-derived mesenchymal stem cells. Alcohol Clin Exp Res 2005; 28:1091-101. [PMID: 15252296 DOI: 10.1097/01.alc.0000130808.49262.f5] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
BACKGROUND In addition to a decrease in bone mass in alcoholics their osteopenic skeletons show an increase in bone marrow adiposity. Human bone marrow mesenchymal stem cells (hMSC) in vivo differentiate into several phenotypes including osteogenic and adipogenic cells, both of which remain as resident populations of bone marrow. In vitro, the lineage commitment and differentiation of hMSC toward the adipogenic pathway can be promoted by alcohol. METHODS Human male and female mesenchymal stem cells from joint replacement surgery were cultured. Cells were grouped as: 1) Control (no additions to the culture medium), 2) EtOH (50 mm alcohol added to the culture medium), 3) OS (osteogenic inducers added to the culture medium), and 4) OS + EtOH (osteogenic inducers and 50 mm alcohol added to the culture medium). Cultures stained with Nile Red confirmed the development of differentiated adipocytes. Population analysis was performed using fluorescence-activated cell sorting. Gene expression of early, middle, late, and terminal differentiation stage markers (PPAR)gamma2, lipoprotein lipase, adipsin, leptin, and adipocyte P2 (aP2)] was studied by Northern hybridization, and protein synthesis of aP2 was determined by Western analysis. RESULTS Nile red staining confirmed increased adipocyte development 10 days after the onset of treatment with 50 mm alcohol and osteogenic induction. By day 21 the number of adipocytes increased to 13.6% of the total population. Alcohol up-regulated the gene expression of PPARgamma2 whereas no up-regulation was observed for the other genes. Protein production of aP2 was significantly increased in hMSC cells by culture in the presence of alcohol. CONCLUSIONS The data suggest that alcohol's adipogenic effect on cultured hMSC is through up-regulation of PPARgamma2 at the point of lineage commitment as well as through enhancement of lipid transport and storage through increased aP2 synthesis. The alcohol-induced expression and synthesis changes account for the increased Nile red staining of cultured hMSC.
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Affiliation(s)
- Frederick H Wezeman
- Department of Orthopaedic Surgery and Rehabilitation and the Alcohol Research Program, Loyola University Stritch School of Medicine, Maywood, Illinois 60153, USA.
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19
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Vermeer C, Shearer MJ, Zittermann A, Bolton-Smith C, Szulc P, Hodges S, Walter P, Rambeck W, Stöcklin E, Weber P. Beyond deficiency: potential benefits of increased intakes of vitamin K for bone and vascular health. Eur J Nutr 2004; 43:325-35. [PMID: 15309455 DOI: 10.1007/s00394-004-0480-4] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2003] [Accepted: 12/10/2003] [Indexed: 02/07/2023]
Abstract
Vitamin K is well known for its role in the synthesis of a number of blood coagulation factors. During recent years vitamin K-dependent proteins were discovered to be of vital importance for bone and vascular health. Recommendations for dietary vitamin K intake have been made on the basis of the hepatic requirements for the synthesis of blood coagulation factors. Accumulating evidence suggests that the requirements for other functions than blood coagulation may be higher. This paper is the result of a closed workshop (Paris, November 2002) in which a number of European vitamin K experts reviewed the available data and formulated their standpoint with respect to recommended dietary vitamin K intake and the use of vitamin K-containing supplements.
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Affiliation(s)
- Cees Vermeer
- Dept. of Biochemistry, University of Maastricht, P. O. Box 616, 6200 MD Maastricht, The Netherlands.
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20
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Horiuchi-Suzuki K, Konno A, Ueda M, Fukuda Y, Nishio S, Hashimoto K, Saji H. Skeletal affinity of Tc(V)-DMS is bone cell mediated and pH dependent. Eur J Nucl Med Mol Imaging 2003; 31:388-98. [PMID: 14647982 DOI: 10.1007/s00259-003-1364-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2003] [Accepted: 09/16/2003] [Indexed: 10/26/2022]
Abstract
In spite of recent advances in bone cellular and molecular biology, there is still a poor correlation between these parameters and data obtained from bone scintigraphy. Diphosphonate derivatives radiolabelled with technetium-99m (Tc-BPs) have long been recognised as bone-seeking agents with an affinity for areas of active mineralisation. However, during clinical trials with a pH-sensitive tumour agent, the pentavalent technetium complex of dimercaptosuccinic acid [Tc(V)-DMS] showed a noticeable osteotropic character only in bone pathologies (bone metastases, Paget's diseases) and lacked accumulation in normal mature bone. To decipher the osteotropic character of Tc(V)-DMS, a study at the cellular level was considered necessary. Moreover, to learn more about the role of Tc bone agents, acid-base regulation by bone tissue or cells was studied. First, biological parameters in body fluid were measured under systemic acidosis, induced by glucose administration, in normal and Ehrlich ascites tumour (EAT)-bearing mice. Then, in vivo biodistribution studies using Tc(V)-DMS or a conventional Tc-BP agent were carried out. The effect of glucose-mediated acidification on the skeletal distribution of the Tc agents in the mice provided valuable hints regarding the differential mediation of bone cells in skeletal tissue affinity for the agents. Thereafter, in vitro studies on osteoblast and osteoclast cells were performed and the comparative affinity of Tc(V)-DMS and Tc-BP was screened under diverse acidification conditions. Moreover, studies were also carried out on acid-base parameters related to the cellular uptake mechanism. Very specific pH-sensitive Tc(V)-DMS accumulation only in the osteoclastic system was detected, and use of Tc(V)-DMS in the differential detection of osteoblastic and osteoclastic metastases is discussed.
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Affiliation(s)
- Kazuko Horiuchi-Suzuki
- Development Bureau, Hamamatsu Photonics K.K., Hirakuchi 500, 434-8601, Hamakita City, Japan.
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21
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Abstract
Cathepsin K is a member of the papain superfamily of cysteine proteases and plays a pivotal role in osteoclast-mediated bone resorption. This enzyme is an excellent target for antiresorptive therapies for osteopenic disorders such as osteoporosis.(1) Although isolated inhibitor studies on purified enzymes is required to discover potent and selective inhibitors of cathepsin K, a quantitative cytochemical assay(2) for cathepsin K would allow inhibitors to be tested on actual osteoclasts within sections of bone. Furthermore cathepsin K activity could be used to identify and analyse osteoclasts at definitive stages of their lifespan. A cytochemical assay is described that localizes osteoclast cathepsin K activity in unfixed, undecalcified cryostat sections of animal and human bone.
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Affiliation(s)
- Robert A Dodds
- Growth Factors Drug Discovery, Johnson and Johnson Pharmaceutical Research and Development, Raritan, NJ 08869, USA.
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22
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Abstract
In this study we analyzed the acromial spurs of 15 patients with impingement syndrome undergoing open rotator cuff repair. Mineral apposition analysis and quantitative cytochemical techniques for glucose-6-phosphate dehydrogenase (G6PD) activity (pentose phosphate pathway), alkaline phosphatase (ALP) activity (osteoblast activity), and tartrate-resistant acid phosphatase (TRAP) activity (osteoclast phenotype) were used to examine the distribution and level of activity of selected marker enzymes within the acromial spur insertion into the coracoacromial ligament in order to establish whether local behavior of bone cells is consistent with the proposed secondary development of the acromial spur. Our results indicate that G6PD and ALP activity was higher in osteoblasts on the inferior surface compared with the superior surface of the acromial spur in all patients (P <.001). This area correlated to the most intense area of mineral apposition shown by dual tetracycline labeling. TRAP activity revealed a heterogeneous distribution within the samples. A greater G6PD activity per cell (mean increase of 87%) was seen at the tip compared with that in post- and pre-tip zones within the coronal plane (P <.0002). The qualitative and quantitative enzyme analyses show that the acromial insertion of the coracoacromial ligament is actively involved in bone turnover. The spatial distribution patterns of metabolically active bone-forming osteoblastic cells compared with a heterogeneous distribution of TRAP-positive osteoclasts provide evidence of bone remodeling consistent with the morphologic contours of the acromial enthesis. The sites of oxytetracycline labeling appear to correlate with the sites of high ALP and G6PD activity, which supports the concept of spur formation being a secondary phenomenon in the presence of established rotator cuff tears.
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Affiliation(s)
- A F W Chambler
- Department of Orthopaedics, St. Mary's Hospital, London, United Kingdom.
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23
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Noxon SJ, King GJ, Gu G, Huang G. Osteoclast clearance from periodontal tissues during orthodontic tooth movement. Am J Orthod Dentofacial Orthop 2001; 120:466-76. [PMID: 11709664 DOI: 10.1067/mod.2001.117912] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The presence of osteoclasts at locations of alveolar bone remodeling is antecedent to orthodontic tooth movement. Cell recruitment and clearance are the mechanisms by which osteoclast populations are regulated. Research in other tissues has revealed that many cells die after their functional lives are past by a process called apoptosis, or programmed cell death. The purpose of this study was to examine the role of apoptosis in osteoclast clearance at orthodontically treated sites as a function of time and location. Orthodontic appliances were placed on 96 rats of the Sprague-Dawley strain. The rats were assigned to either treatment or sham (control) groups and killed 1, 3, 5, and 7 days after appliance placement. Tissue samples were prepared for histochemical evaluation and quantification of morphologic features. Tartrate-resistant acid phosphatase (TRAP) and ApopTag (TdT-mediated dUTP-biotin nick 3' end labeling) stains were used to identify osteoclasts and committed preosteoclasts and to discriminate between apoptotic and nonapoptotic nuclei. Pyknotic nuclei and apoptotic bodies were also counted as a morphologic assessment of apoptosis. The percentages of TRAP/ApopTag-positive nuclei were measured in 4 different periodontal regions. There was a highly significant difference in the overall percentage of TRAP/ApopTag-positive nuclei between the control and the treatment groups at 3, 5, and 7 days (P <.001). Morphologic criteria were also statistically different at days 5 and 7 (P <.05). These data strongly suggested that osteoclasts recruited for orthodontic tooth movement are, at least in part, cleared by apoptosis.
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Affiliation(s)
- S J Noxon
- Department of Orthodontics, University of Washington, Seattle, USA
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24
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Dodds RA, James IE, Rieman D, Ahern R, Hwang SM, Connor JR, Thompson SD, Veber DF, Drake FH, Holmes S, Lark MW, Gowen M. Human osteoclast cathepsin K is processed intracellularly prior to attachment and bone resorption. J Bone Miner Res 2001; 16:478-86. [PMID: 11277265 DOI: 10.1359/jbmr.2001.16.3.478] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Cathepsin K is a member of the papain superfamily of cysteine proteases and has been proposed to play a pivotal role in osteoclast-mediated bone resorption. We have developed a sensitive cytochemical assay to localize and quantify osteoclast cathepsin K activity in sections of osteoclastoma and human bone. In tissue sections, osteoclasts that are distant from bone express high levels of cathepsin K messenger RNA (mRNA) and protein. However, the majority of the cathepsin K in these cells is in an inactive zymogen form, as assessed using both the cytochemical assay and specific immunostaining. In contrast, osteoclasts that are closer to bone contain high levels of immunoreactive mature cathepsin K that codistributes with enzyme activity in a polarized fashion toward the bone surface. Polarization of active enzyme was clearly evident in osteoclasts in the vicinity of bone. The osteoclasts apposed to the bone surface were almost exclusively expressing the mature form of cathepsin K. These cells showed intense enzyme activity, which was polarized at the ruffled border. These results suggest that the in vivo activation of cathepsin K occurs intracellularly, before secretion into the resorption lacunae and the onset of bone resorption. The processing of procathepsin K to mature cathepsin K occurs as the osteoclast approaches bone, suggesting that local factors may regulate this process.
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Affiliation(s)
- R A Dodds
- Department of Bone and Cartilage Biology, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania, USA
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Nuttall ME, Gimble JM. Is there a therapeutic opportunity to either prevent or treat osteopenic disorders by inhibiting marrow adipogenesis? Bone 2000; 27:177-84. [PMID: 10913909 DOI: 10.1016/s8756-3282(00)00317-3] [Citation(s) in RCA: 223] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Bone marrow stromal cells can undergo adipogenesis or osteoblastogenesis in vitro and in vivo. This review explores the stromal cell's differentiation plasticity in the context of osteoporosis and other metabolic bone disorders. Attention is focused on the apparent reciprocal relationship that is postulated to exist between the adipocyte and osteoblast phenotypes. The signal transduction pathways implicated in this process are evaluated as potential targets for therapeutic intervention and drug design.
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Affiliation(s)
- M E Nuttall
- Department of Bone and Cartilage Biology, SmithKline Beecham Pharmaceuticals, King of Prussia, PA 19406, USA.
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26
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Prichett WP, Patton AJ, Field JA, Brun KA, Emery JG, Tan KB, Rieman DJ, McClung HA, Nadeau DP, Mooney JL, Suva LJ, Gowen M, Nuttall ME. Identification and cloning of a human urea transporter HUT11, which is downregulated during adipogenesis of explant cultures of human bone. J Cell Biochem 2000. [DOI: 10.1002/(sici)1097-4644(20000315)76:4<639::aid-jcb12>3.0.co;2-i] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Abstract
Osteoclasts are the primary cell type responsible for bone resorption. This paper reviews many of the known regulators of osteoclast activity, including hormones, cytokines, ions, and arachidonic acid metabolites. Most of the hormones and cytokines that inhibit osteoclast activity act directly on the osteoclasts. In contrast, most of the hormones and cytokines that stimulate osteoclast activity act indirectly through osteoblasts. Particularly interesting in this regard are agents that directly inhibit activity of highly purified osteoclasts yet stimulate activity of osteoclasts that are co-cultured with osteoblasts. Recent studies have demonstrated that the primary mechanism by which bone resorptive agents stimulate osteoclast activity indirectly is likely to be up-regulation of production of osteoclast differentiation factor/osteoprotegerin ligand (ODF/OPGL) by the osteoblasts. In addition to discussing regulators of osteoclast activity per se, this paper also reviews the role of osteoclast apoptosis to limit the extent of bone resorption.
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Affiliation(s)
- E M Greenfield
- Department of Orthopaedics, Case Western Reserve University, Cleveland, OH 44106-5000, USA.
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28
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Nuttall ME, Patton AJ, Olivera DL, Nadeau DP, Gowen M. Human trabecular bone cells are able to express both osteoblastic and adipocytic phenotype: implications for osteopenic disorders. J Bone Miner Res 1998; 13:371-82. [PMID: 9525337 DOI: 10.1359/jbmr.1998.13.3.371] [Citation(s) in RCA: 288] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The decrease in bone volume associated with osteoporosis and age-related osteopenia is accompanied by increased marrow adipose tissue formation. Reversal of this process may provide a novel therapeutic approach for osteopenic disorders. We have shown that cells cultured from human trabecular bone are not only osteogenic, but are able also to undergo adipocyte differentiation under defined culture conditions. Osteoblast differentiation was induced by 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and adipocyte differentiation by dexamethasone (dex) plus 3-isobutyl-1-methylxanthine (IBMX) treatment. Adipogenesis was characterized by lineage-specific enzyme and gene activities, alpha-glycerophosphate-3-dehydrogenase activity, fatty acid binding protein, aP2 and lipoprotein lipase expression. Osteoblastogenesis was assessed by osteoblast characteristic 1,25(OH)2D3 induction of alkaline phosphatase activity and osteoblast-specific 1,25(OH)2D3-induced osteocalcin synthesis and release. We provide evidence for a common pluripotent mesenchymal stem cell that is able either to undergo adipogenesis or osteoblastogenesis, using clonal cell lines derived from human trabecular bone cell cultures. Adipogenesis can be induced also by long chain fatty acids and the thiazolidinedione troglitazone. Dex plus IBMX-induced adipogenesis can be inhibited by interleukin-1beta, tumor necrosis factor-alpha, and transforming growth factor-beta. Interestingly, and in contrast to extramedullary adipocyte differentiation as shown by mouse 3T3L-1 and a human liposarcoma SW872 cell line, trabecular bone adipogenesis was unaffected by insulin. Also, the formation of fully differentiated adipocytes from trabecular bone cells after troglitazone treatment and long chain fatty acids was dependent on increased expression of the nuclear hormone receptor peroxisome proliferator-activated receptor gamma2 caused by dex plus IBMX. Specific inhibition of marrow adipogenesis and promotion of osteoblastogenesis of a common precursor cell may provide a novel therapeutic approach to the treatment of osteopenic disorders.
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Affiliation(s)
- M E Nuttall
- Department of Bone and Cartilage Biology, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406, USA.
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29
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Frith JC, Mönkkönen J, Blackburn GM, Russell RG, Rogers MJ. Clodronate and liposome-encapsulated clodronate are metabolized to a toxic ATP analog, adenosine 5'-(beta, gamma-dichloromethylene) triphosphate, by mammalian cells in vitro. J Bone Miner Res 1997; 12:1358-67. [PMID: 9286751 DOI: 10.1359/jbmr.1997.12.9.1358] [Citation(s) in RCA: 307] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Clodronate, alendronate, and other bisphosphonates are widely used in the treatment of bone diseases characterized by excessive osteoclastic bone resorption. The exact mechanisms of action of bisphosphonates have not been identified but may involve a toxic effect on mature osteoclasts due to the induction of apoptosis. Clodronate encapsulated in liposomes is also toxic to macrophages in vivo and may therefore be of use in the treatment of inflammatory diseases. It is generally believed that bisphosphonates are not metabolized. However, we have found that mammalian cells in vitro (murine J774 macrophage-like cells and human MG63 osteosarcoma cells) can metabolize clodronate (dichloromethylenebisphosphonate) to a nonhydrolyzable adenosine triphosphate (ATP) analog, adenosine 5'-(beta, gamma-dichloromethylene) triphosphate, which could be detected in cell extracts by using fast protein liquid chromatography. J774 cells could also metabolize liposome-encapsulated clodronate to the same ATP analog. Liposome-encapsulated adenosine 5'-(beta, gamma-dichloromethylene) triphosphate was more potent than liposome-encapsulated clodronate at reducing the viability of cultures of J774 cells and caused both necrotic and apoptotic cell death. Neither alendronate nor liposome-encapsulated alendronate were metabolized. These results demonstrate that the toxic effect of clodronate on J774 macrophages, and probably on osteoclasts, is due to the metabolism of clodronate to a nonhydrolyzable ATP analog. Alendronate appears to act by a different mechanism.
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Affiliation(s)
- J C Frith
- Department of Human Metabolism and Clinical Biochemistry, University of Sheffield Medical School, United Kingdom
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Gupta A, Guo XL, Alvarez UM, Hruska KA. Regulation of sodium-dependent phosphate transport in osteoclasts. J Clin Invest 1997; 100:538-49. [PMID: 9239400 PMCID: PMC508220 DOI: 10.1172/jci119563] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Osteoclasts are the primary cells responsible for bone resorption. They are exposed to high ambient concentrations of inorganic phosphate (Pi) during the process of bone resorption and they possess specific Pi-transport system(s) capable of taking up Pi released by bone resorption. By immunochemical studies and PCR, we confirmed previous studies suggesting the presence of an Na-dependent Pi transporter related to the renal tubular "NaPi" proteins in the osteoclast. Using polyclonal antibodies to NaPi-2 (the rat variant), an approximately 95-kD protein was detected, localized in discrete vesicles in unpolarized osteoclasts cultured on glass coverslips. However, in polarized osteoclasts cultured on bone, immunofluorescence studies demonstrated the protein to be localized exclusively on the basolateral membrane, where it colocalizes with an Na-H exchanger but opposite to localization of the vacuolar H-ATPase. An inhibitor of phosphatidylinositol 3-kinase, wortmannin, and an inhibitor of actin cytoskeletal organization, cytochalasin D, blocked the bone-stimulated increase in Pi uptake. Phosphonoformic acid (PFA), an inhibitor of the renal NaPi-cotransporter, reduced NaPi uptake in the osteoclast. PFA also elicited a dose-dependent inhibition of bone resorption. PFA limited ATP production in osteoclasts attached to bone particles. Our results suggest that Pi transport in the osteoclast is a process critical to the resorption of bone through provision of necessary energy substrates.
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Affiliation(s)
- A Gupta
- Renal Division, Barnes-Jewish Hospital of St. Louis, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Williams JP, Blair HC, McDonald JM, McKenna MA, Jordan SE, Williford J, Hardy RW. Regulation of osteoclastic bone resorption by glucose. Biochem Biophys Res Commun 1997; 235:646-51. [PMID: 9207213 DOI: 10.1006/bbrc.1997.6795] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Osteoclasts degrade bone by pumping molar quantities of HCl to dissolve the calcium salts of bone, an energy intensive process evidently supported by abundant mitochondria. This is the first study to directly examine the ability of various metabolites to serve as potential energy sources for osteoclastic bone resorption. Glucose, and to a lesser extent lactate, supported osteoclastic bone degradation. However, fatty acids (palmitate, myristate and stearate), essential amino acids plus 20 mM alanine, or ketone bodies (acetoacetate, beta-hydroxybutyrate and alpha-ketoglutarate) did not support bone degradation. Resorption declined to 10-30% of glucose controls when fatty acids or ketoacids were substituted for glucose. Resorption was glucose concentration dependent, with maximal activity at approximately 7 mM (K(M) approximately 3 mM). Glucose transport was linear for approximately 15 minutes, specific for D-glucose, and inhibited by cytochalasin B. Osteoclasts cultured on bone transported glucose at almost twice the rate of those off bone (Vmax 23 versus 13 nmols/mg/min, respectively) and medium acid accumulation paralleled glucose uptake, while the K(M) was unchanged. We conclude that glucose is the principal energy source required for bone degradation. Further, characteristics of glucose transport are consistent with the hypothesis that fluctuations in serum glucose concentration are an important component in regulation of osteoclastic bone degradation.
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Affiliation(s)
- J P Williams
- Department of Pathology, The University of Alabama at Birmingham 35294, USA
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James IE, Dodds RA, Olivera DL, Nuttall ME, Gowen M. Human osteoclastoma-derived stromal cells: correlation of the ability to form mineralized nodules in vitro with formation of bone in vivo. J Bone Miner Res 1996; 11:1453-60. [PMID: 8889845 DOI: 10.1002/jbmr.5650111012] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
It has been suggested that the stromal element of human osteoclastomas contains osteoblastic cells. In this study, we demonstrate that osteoclast-depleted, passaged stromal cells express alkaline phosphatase and osteocalcin in vitro and form mineralized nodules under appropriate culture conditions. In addition, we describe a model in which severe combined immunodeficient (SCID) mice were used to support the differentiation of these putative human osteoblast progenitors in vivo. Lesions formed from human stromal cells were identified using the OKa blood group antigen and human procollagen type I antibodies. By 21 days, the lesion was a complete bone unit: a fully mineralized cortex, remodeling trabeculae, and a highly cellular marrow space. Stromal cells derived from six out of seven osteoclastomas produced identical lesions. Further studies have demonstrated that the capacity of the osteoclastoma-derived stromal cells to form bone in vivo and in vitro is passage dependent; early passages were osteogenic in both model systems, while later passages were not. In conclusion, we have developed a model in which the osteogenic nature of cells can be confirmed in vivo. Furthermore, human osteoclastoma-derived stromal cells provide a source of these osteogenic cells to study human osteoblast differentiation, both in vivo and in vitro.
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Affiliation(s)
- I E James
- Department of Cellular Biochemistry, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania, USA
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Drake FH, Dodds RA, James IE, Connor JR, Debouck C, Richardson S, Lee-Rykaczewski E, Coleman L, Rieman D, Barthlow R, Hastings G, Gowen M. Cathepsin K, but not cathepsins B, L, or S, is abundantly expressed in human osteoclasts. J Biol Chem 1996; 271:12511-6. [PMID: 8647859 DOI: 10.1074/jbc.271.21.12511] [Citation(s) in RCA: 525] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Random high throughput sequencing of a human osteoclast cDNA library was employed to identify novel osteoclast-expressed genes. Of the 5475 ESTs obtained, approximately 4% encoded cathepsin K, a novel cysteine protease homologous to cathepsins S and L; ESTs for other cathepsins were rare. In addition, ESTs for cathepsin K were absent or at low frequency in cDNA libraries from numerous other tissues and cells. In situ hybridization in osteoclastoma and osteophyte confirmed that cathepsin K mRNA was highly expressed selecively in osteoclasts; cathepsins S, L, and B were not detectable. Cathepsin K was not detected by in situ hybridization in a panel of other tissues. Western blot of human osteoclastoma or fetal rat humerus demonstrated bands of 38 and 27 kDa, consistent with sizes predicted for pro- and mature cathepsin K. Immunolocalization in osteoclastoma and osteophyte showed intense punctate staining of cathepsin K exclusively in osteoclasts, with a polar distribution that was more intense at the bone surface. The abundant expression of cathepsin K selectively in osteoclasts strongly suggests that it plays a specialized role in bone resorption. Furthermore, the data suggest that random sequencing of ESTs from cDNA libraries is a valuable approach for identifying novel cell-selective genes.
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Affiliation(s)
- F H Drake
- Department of Cellular Biochemistry, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406, USA
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Dodds RA, Connor JR, James IE, Rykaczewski EL, Appelbaum E, Dul E, Gowen M. Human osteoclasts, not osteoblasts, deposit osteopontin onto resorption surfaces: an in vitro and ex vivo study of remodeling bone. J Bone Miner Res 1995; 10:1666-80. [PMID: 8592943 DOI: 10.1002/jbmr.5650101109] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Osteopontin is a phosphorylated glycoprotein believed to be secreted by osteoblasts and deposited into the bone matrix to facilitate osteoclasts adhesion or to initiate osteoid mineralization. Previously we have presented contradictory evidence that osteoclasts express osteopontin mRNA in human remodeling bone. The aim of this study was to ascertain whether osteoclasts synthesize and deposit osteopontin in resorption lucunae. We characterized expression of osteopontin mRNA and protein expression in both intramembranous and endochondral ossification, as well as remodeling bone, in the human osteophyte. Osteopontin mRNA was expressed in osteoclast with tartrate-resistant acid phosphatase (TRAP) positivity within resorption lacunae. The osteoclasts and immediate resorption surfaces also expressed osteopontin. However, osteopontin mRNA and protein were weak (transient) or undetectable in osteoblasts at adjacent bone formation sites; no osteopontin expression was observed in the osteoid, although occasional reactivity was observed in osteocytes and the mineral-osteoid interface. In contrast, osteopontin was highly expressed in the osteoblasts and matrix of woven bone during intramembranous and endochondral ossification. The matrix expression correlated with mineralization; however, in some instances osteopontin deposition was observed prior to mineralization. Similarly, osteopontin expression was evident in cartilage matrix, solely at foci of mineralization. Chondroclasts expressed osteopontin mRNA and protein: the surfaces of resorbed calcified cartilage also expressed osteopontin. Abnormal, unmineralized matrices apparently lacked deposited osteopontin, but were nevertheless resorbed by osteoclasts; the osteoclasts and resorbed surfaces expressed no osteopontin protein. That osteoclasts are responsible for the deposition of osteopontin was confirmed in vitro, whereby resorption pits in whale dentine and bovine bone slices, produced by isolated human osteoclasts, contained deposited osteopontin. Osteopontin may facilitate the adhesion (or detachment) of the osteoclast to the bone surface. Alternatively, the possibility that osteopontin may act as a postresorptive signal to recruit osteoblasts, or to polarize and direct the mineralization of the formed osteoid, is discussed.
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Affiliation(s)
- R A Dodds
- SmithKline Beecham Pharmaceuticals, Department of Cellular Biochemistry, King of Prussia, Pennsylvania, USA
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Middleton J, Arnott N, Walsh S, Beresford J. Osteoblasts and osteoclasts in adult human osteophyte tissue express the mRNAs for insulin-like growth factors I and II and the type 1 IGF receptor. Bone 1995; 16:287-93. [PMID: 7786631 DOI: 10.1016/8756-3282(94)00040-9] [Citation(s) in RCA: 84] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Insulin-like growth factors (IGFs) are among the most abundant growth factors present in bone. In vitro, bone-derived cells both produce and respond to IGFs I and II, suggesting that these growth factors play an autocrine role in the regulation of bone turnover. In vivo, however, particularly in adult bone, their sites of expression have not been well documented. We have used, therefore, the technique of in situ hybridization to study the expression of the mRNAs for IGFs I and II and the type 1 IGF receptor in adult human osteophyte tissue. Throughout the developing osteophyte there was a strong association between osteogenesis and the expression of all three mRNA transcripts. The highest levels of expression were observed in active osteoblasts. Hybridization signals were weak or absent in flat cells lining quiescent surfaces and in cells of the bone marrow, including those that expressed alkaline phosphatase activity. Osteocytes and cells of the periosteum were negative. At sites of endochondral bone formation newly differentiated and hypertrophic chondrocytes expressed the mRNAs for IGFs and IGF receptor whereas cells of the perichondrium were negative. A striking finding of this investigation was that osteoclasts at sites of bone and calcified cartilage resorption expressed high levels of all three mRNA transcripts. These results support the hypothesis that locally produced IGFs are important regulators of bone formation. The differential expression of all three transcripts among cells of the osteoblast lineage suggests that IGFs may be involved in the maintenance of the mature osteoblast phenotype rather than in inducing the differentiation of marrow precursors or controlling the osteoblast-osteocyte transition.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J Middleton
- Bath Institute for Rheumatic Diseases, United Kingdom
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