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Vrščaj LA, Marc J, Ostanek B. Towards an enhanced understanding of osteoanabolic effects of PTH-induced microRNAs on osteoblasts using a bioinformatic approach. Front Endocrinol (Lausanne) 2024; 15:1380013. [PMID: 39086902 PMCID: PMC11289717 DOI: 10.3389/fendo.2024.1380013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Accepted: 06/03/2024] [Indexed: 08/02/2024] Open
Abstract
In this study, we used a bioinformatic approach to construct a miRNA-target gene interaction network potentially involved in the anabolic effect of parathyroid hormone analogue teriparatide [PTH (1-34)] on osteoblasts. We extracted a dataset of 26 microRNAs (miRNAs) from previously published studies and predicted miRNA target interactions (MTIs) using four software tools: DIANA, miRWalk, miRDB, and TargetScan. By constructing an interactome of PTH-regulated miRNAs and their predicted target genes, we elucidated signaling pathways regulating pluripotency of stem cells, the Hippo signaling pathway, and the TGF-beta signaling pathway as the most significant pathways in the effects of PTH on osteoblasts. Furthermore, we constructed intersection of MTI networks for these three pathways and added validated interactions. There are 8 genes present in all three selected pathways and a set of 18 miRNAs are predicted to target these genes, according to literature data. The most important genes in all three pathways were BMPR1A, BMPR2 and SMAD2 having the most interactions with miRNAs. Among these miRNAs, only miR-146a-5p and miR-346 have validated interactions in these pathways and were shown to be important regulators of these pathways. In addition, we also propose miR-551b-5p and miR-338-5p for further experimental validation, as they have been predicted to target important genes in these pathways but none of their target interactions have yet been verified. Our wet-lab experiment on miRNAs differentially expressed between PTH (1-34) treated and untreated mesenchymal stem cells supports miR-186-5p from the literature obtained data as another prominent miRNA. The meticulous selection of miRNAs outlined will significantly support and guide future research aimed at discovering and understanding the crucial pathways of osteoanabolic PTH-epigenetic effects on osteoblasts. Additionally, they hold potential for the discovery of new PTH target genes, innovative biomarkers for the effectiveness and safety of osteoporosis-affected treatment, as well as novel therapeutic targets.
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Affiliation(s)
- Lucija Ana Vrščaj
- Department of Clinical Biochemistry, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
| | - Janja Marc
- Department of Clinical Biochemistry, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
- Clinical Institute of Clinical Chemistry and Biochemistry, University Clinical Centre Ljubljana, Ljubljana, Slovenia
| | - Barbara Ostanek
- Department of Clinical Biochemistry, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
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Shen L, Yu Y, Karner CM. SLC38A2 provides proline and alanine to regulate postnatal bone mass accrual in mice. Front Physiol 2022; 13:992679. [PMID: 36213239 PMCID: PMC9538353 DOI: 10.3389/fphys.2022.992679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Accepted: 09/02/2022] [Indexed: 11/13/2022] Open
Abstract
Amino acids have recently emerged as important regulators of osteoblast differentiation and bone formation. Osteoblasts require a continuous supply of amino acids to sustain biomass production to fuel cell proliferation, osteoblast differentiation and bone matrix production. We recently identified proline as an essential amino acid for bone development by fulfilling unique synthetic demands that are associated with osteoblast differentiation. Osteoblasts rely on the amino acid transporter SLC38A2 to provide proline to fuel endochondral ossification. Despite this, very little is known about the function or substrates of SLC38A2 during bone homeostasis. Here we demonstrate that the neutral amino acid transporter SLC38A2 is expressed in osteoblast lineage cells and provides proline and alanine to osteoblast lineage cells. Genetic ablation of SLC38A2 using Prrx1Cre results in decreased bone mass in both male and female mice due to a reduction in osteoblast numbers and bone forming activity. Decreased osteoblast numbers are attributed to impaired proliferation and osteogenic differentiation of skeletal stem and progenitor cells. Collectively, these data highlight the necessity of SLC38A2-mediated proline and alanine uptake during postnatal bone formation and bone homeostasis.
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Affiliation(s)
- Leyao Shen
- Department of Internal Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Yilin Yu
- Department of Internal Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Courtney M. Karner
- Department of Internal Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX, United States
- Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, TX, United States
- Department of Orthopaedic Surgery, Duke University School of Medicine, Durham, NC, United States
- *Correspondence: Courtney M. Karner,
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Parathyroid hormone (PTH) regulation of metabolic homeostasis: An old dog teaches us new tricks. Mol Metab 2022; 60:101480. [PMID: 35338013 PMCID: PMC8980887 DOI: 10.1016/j.molmet.2022.101480] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 02/11/2022] [Accepted: 03/16/2022] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Late in the nineteenth century, it was theorized that a circulating product produced by the parathyroid glands could negatively impact skeletal homeostasis. A century later, intermittent administration of that protein, namely parathyroid hormone (PTH), was approved by the FDA and EMA as the first anabolic agent to treat osteoporosis. Yet, several unanswered but important questions remain about the skeletal actions of PTH. SCOPE OF REVIEW Current research efforts have focused on improving the efficacy of PTH treatment by designing structural analogs and identifying other targets (e.g., the PTH or the calcium sensing receptor). A unique but only recently described aspect of PTH action is its regulation of cellular bioenergetics and metabolism, namely in bone and adipose tissue but also in other tissues. The current review aims to provide a brief background on PTH's previously described actions on bone and highlights how PTH regulates osteoblast bioenergetics, contributing to greater bone formation. It will also shed light on how PTH could alter metabolic homeostasis through its actions in other cells and tissues, thereby impacting the skeleton in a cell non-autonomous manner. MAJOR CONCLUSIONS PTH administration enhances bone formation by targeting the osteoblast through transcriptional changes in several pathways; the most prominent is via adenyl cyclase and PKA. PTH and its related protein, PTHrP, also induce glycolysis and fatty acid oxidation in bone cells and drive lipolysis and thermogenic programming in adipocytes; the latter may indirectly but positively influence skeletal metabolism. While much work remains, alterations in cellular metabolism may also provide a novel mechanism related to PTH's temporal actions. Thus, the bioenergetic impact of PTH can be considered another of the myriad anabolic effects of PTH on the skeleton. Just as importantly from a translational perspective, the non-skeletal metabolic effects may lead to a better understanding of whole-body homeostasis along with new and improved therapies to treat musculoskeletal conditions.
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Shen L, Yu Y, Zhou Y, Pruett-Miller SM, Zhang GF, Karner CM. SLC38A2 provides proline to fulfil unique synthetic demands arising during osteoblast differentiation and bone formation. eLife 2022; 11:76963. [PMID: 35261338 PMCID: PMC9007586 DOI: 10.7554/elife.76963] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 03/08/2022] [Indexed: 11/13/2022] Open
Abstract
Cellular differentiation is associated with the acquisition of a unique protein signature which is essential to attain the ultimate cellular function and activity of the differentiated cell. This is predicted to result in unique biosynthetic demands that arise during differentiation. Using a bioinformatic approach, we discovered osteoblast differentiation is associated with increased demand for the amino acid proline. When compared to other differentiated cells, osteoblast-associated proteins including RUNX2, OSX, OCN and COL1A1 are significantly enriched in proline. Using a genetic and metabolomic approach, we demonstrate that the neutral amino acid transporter SLC38A2 acts cell autonomously to provide proline to facilitate the efficient synthesis of proline-rich osteoblast proteins. Genetic ablation of SLC38A2 in osteoblasts limits both osteoblast differentiation and bone formation in mice. Mechanistically, proline is primarily incorporated into nascent protein with little metabolism observed. Collectively, these data highlight a requirement for proline in fulfilling the unique biosynthetic requirements that arise during osteoblast differentiation and bone formation.
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Affiliation(s)
- Leyao Shen
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, United States
| | - Yilin Yu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, United States
| | - Yunji Zhou
- Department of Biostatistics and Bioinformatics, Duke University, Durham, United States
| | - Shondra M Pruett-Miller
- Department of Cell and Molecular Biology, St Jude Children's Research Hospital, Memphis, United States
| | - Guo-Fang Zhang
- Sarah W Stedman Nutrition and Metabolism Center, Duke University Medical Center, Durham, United States
| | - Courtney M Karner
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, United States
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Sharma D, Yu Y, Shen L, Zhang GF, Karner CM. SLC1A5 provides glutamine and asparagine necessary for bone development in mice. eLife 2021; 10:71595. [PMID: 34647520 PMCID: PMC8553342 DOI: 10.7554/elife.71595] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 10/12/2021] [Indexed: 12/03/2022] Open
Abstract
Osteoblast differentiation is sequentially characterized by high rates of proliferation followed by increased protein and matrix synthesis, processes that require substantial amino acid acquisition and production. How osteoblasts obtain or maintain intracellular amino acid production is poorly understood. Here, we identify SLC1A5 as a critical amino acid transporter during bone development. Using a genetic and metabolomic approach, we show SLC1A5 acts cell autonomously to regulate protein synthesis and osteoblast differentiation. SLC1A5 provides both glutamine and asparagine which are essential for osteoblast differentiation. Mechanistically, glutamine and to a lesser extent asparagine support amino acid biosynthesis. Thus, osteoblasts depend on Slc1a5 to provide glutamine and asparagine, which are subsequently used to produce non-essential amino acids and support osteoblast differentiation and bone development.
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Affiliation(s)
- Deepika Sharma
- Department of Orthopaedic Surgery, Duke University School of Medicine, Durham, United States
| | - Yilin Yu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, United States
| | - Leyao Shen
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, United States
| | - Guo-Fang Zhang
- Sarah W. Stedman Nutrition and Metabolism Center & Duke Molecular Physiology Institute, Duke University Medical Center, Durham, United States.,Department of Medicine, Duke University School of Medicine, Durham, United States
| | - Courtney M Karner
- Department of Orthopaedic Surgery, Duke University School of Medicine, Durham, United States.,Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, United States.,Charles and Jane Pak Center for Mineral Metabolism and Clinical Research. University of Texas Southwestern Medical Center at Dallas, Dallas, United States
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Abstract
Radiolabeled amino acid uptake assays are a highly sensitive method used to characterize the uptake of amino acids by cells or tissues in culture. This method is an excellent tool to quantify changes in amino acid consumption that are associated with states of cellular differentiation and/or disease. The methods presented here can be adapted to measure the transport of all amino acids and can be applied to cultured cells and bone explants.
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Affiliation(s)
- Leyao Shen
- Department of Orthopaedic Surgery, Duke University School of Medicine, Duke University, Durham, NC, USA
| | - Courtney M Karner
- Department of Orthopaedic Surgery, Duke University School of Medicine, Duke University, Durham, NC, USA.
- Department of Cell Biology, Duke Orthopaedic, Cellular, Developmental and Genome Laboratories, Duke University School of Medicine, Duke University, Durham, NC, USA.
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Karner CM, Long F. Wnt signaling and cellular metabolism in osteoblasts. Cell Mol Life Sci 2017; 74:1649-1657. [PMID: 27888287 PMCID: PMC5380548 DOI: 10.1007/s00018-016-2425-5] [Citation(s) in RCA: 200] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 11/15/2016] [Accepted: 11/17/2016] [Indexed: 12/20/2022]
Abstract
The adult human skeleton is a multifunctional organ undergoing continuous remodeling. Homeostasis of bone mass in a healthy adult requires an exquisite balance between bone resorption by osteoclasts and bone formation by osteoblasts; disturbance of such balance is the root cause for various bone disorders including osteoporosis. To develop effective and safe therapeutics to modulate bone formation, it is essential to elucidate the molecular mechanisms governing osteoblast differentiation and activity. Due to their specialized function in collagen synthesis and secretion, osteoblasts are expected to consume large amounts of nutrients. However, studies of bioenergetics and building blocks in osteoblasts have been lagging behind those of growth factors and transcription factors. Genetic studies in both humans and mice over the past 15 years have established Wnt signaling as a critical mechanism for stimulating osteoblast differentiation and activity. Importantly, recent studies have uncovered that Wnt signaling directly reprograms cellular metabolism by stimulating aerobic glycolysis, glutamine catabolism as well as fatty acid oxidation in osteoblast-lineage cells. Such findings therefore reveal an important regulatory axis between bone anabolic signals and cellular bioenergetics. A comprehensive understanding of osteoblast metabolism and its regulation is likely to reveal molecular targets for novel bone therapies.
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Affiliation(s)
- Courtney M Karner
- Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis, MO, 63131, USA
- Department of Orthopaedic Surgery, Duke Orthopaedic, Cellular, Developmental and Genome Laboratories, Duke University School of Medicine, Durham, NC, 27710, USA
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Fanxin Long
- Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis, MO, 63131, USA.
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, 63131, USA.
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Bussolati O, Dall'Asta V, Franchi-Gazzola R, Sala R, Rotoli BM, Visigalli R, Casado J, Lopez-Fontanals M, Pastor-Anglada M, Gazzola GC. The role of system A for neutral amino acid transport in the regulation of cell volume. Mol Membr Biol 2001; 18:27-38. [PMID: 11396608 DOI: 10.1080/09687680110033756] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
System A is a secondary active, sodium dependent transport system for neutral amino acids. Strictly coupled with Na,K-ATPase, its activity determines the size of the intracellular amino acid pool, through a complex network of metabolic reaction and exchange fluxes. Many hormones and drugs affect system A activity in specific cell models or tissues. In all the cell models tested thus far the activity of the system is stimulated by amino acid starvation, cell cycle progression, and the incubation under hypertonic conditions. These three conditions produce marked alterations of cell volume. The stimulation of system A activity plays an important role in cell volume restoration, through an expansion of the intracellular amino acid pool. Under normal conditions, system A substrates represent a major fraction of cell compatible osmolytes, organic compounds that exert a protein stabilizing effect. It is, therefore, likely that the activation of system A represents a portion of a more complex response triggered by exposure to stresses of various nature. Since system A transporters have been recently cloned, the molecular bases of these regulatory mechanisms will probably be elucidated in a short time.
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Affiliation(s)
- O Bussolati
- Department of Experimental Medicine, University of Parma, Italy.
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Williams DC, Frolik CA. Physiological and pharmacological regulation of biological calcification. INTERNATIONAL REVIEW OF CYTOLOGY 1991; 126:195-292. [PMID: 2050499 DOI: 10.1016/s0074-7696(08)60685-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Biological calcification is a highly regulated process which occurs in diverse species of microorganisms, plants, and animals. Calcification provides tissues with structural rigidity to function in support and protection, supplies the organism with a reservoir for physiologically important ions, and also serves in a variety of specialized functions. In the vertebrate skeleton, hydroxyapatite crystals are laid down on a backbone of type I collagen, with the process being controlled by a wide range of noncollagenous proteins present in the local surroundings. In bone, cells of the osteoblast lineage are responsible for the synthesis of the bone matrix and many of these regulatory proteins. Osteoclasts, on the other hand, are continually resorbing bone to both produce changes in bone shape and maintain skeletal integrity, and to establish the ionic environment needed by the organism. The proliferation, differentiation, and activity of these cells is regulated by a number of growth factors and hormones. While much has already been discovered over the past few years about the involvement of various regulators in the process of mineralization, the identification and functional characterization of these factors remains an area of intense investigation. As with any complex, biological system that is in a finely tuned equilibrium under normal conditions, problems can occur. An imbalance in the processes of formation and resorption can lead to calcification disorders, and the resultant diseases of the skeletal system have a major impact on human health. A number of pharmacological agents have been, and are being, investigated for their therapeutic potential to correct these defects.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- D C Williams
- Department of Connective Tissue and Monoclonal Antibody Research, Eli Lilly and Company, Indianapolis, Indiana 46285
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Hall GE, Yee JA. Parathyroid hormone alteration of free and tRNA-bound proline specific activities in cultured mouse osteoblast-like cells. Biochem Biophys Res Commun 1989; 161:994-1000. [PMID: 2742596 DOI: 10.1016/0006-291x(89)91341-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The effects of the synthetic amino-terminal fragment of parathyroid hormone [bPTH-(1-34)] on proline uptake and on the specific activities of intracellular free proline and tRNA-bound proline were studied in confluent primary cultures of osteoblast-like cells isolated from neonatal mouse calvaria. Pretreatment of cells for 4 hours with 24 nM bPTH-(1-34) increased subsequent proline uptake by approximately 50-60%; also increased were the specific activities of both intracellular free proline and tRNA-bound proline when [3H]proline was included in the extracellular uptake solution. Specific activities of the free and tRNA-bound proline pools remained elevated after proline uptake times of as long as 30 minutes and 120 minutes, respectively. These results indicate that experiments in which radiolabeled proline is used to evaluate PTH-induced protein synthesis in bone cells must be interpreted cautiously, since apparent changes in protein synthesis might actually reflect, at least in part, PTH-induced changes in the specific activities of precursor pools.
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Affiliation(s)
- G E Hall
- Department of Cell Biology and Anatomy, Texas Tech University Health Sciences Center, Lubbock 79430
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Yee JA, Sutton JK. Parathyroid hormone regulation of proline uptake by cultured neonatal mouse osteoblastlike cells. J Bone Miner Res 1989; 4:23-7. [PMID: 2541599 DOI: 10.1002/jbmr.5650040105] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Regulation of proline uptake by the synthetic amino-terminal fragment of bovine parathyroid hormone [bPTH-(1-34)] has been studied in confluent primary cultures of osteoblastlike cells isolated from neonatal mouse calvaria. The initial velocity of proline transport was increased by 85% in cultures treated with 24 nM bPTH-(1-34) for 6 h. Cycloheximide, at a concentration that inhibited protein synthesis by 97%, did not prevent this effect. However, adding the inhibitor during the first 1-2 h of hormone treatment did significantly reduce its magnitude. Exposure of cells to the inhibitor alone caused a time-dependent decrease in the basal rate of proline uptake. In the absence of protein synthesis, the maximal velocity (Vmax) of transport was 60% greater in cultures treated with 24 nM bPTH-(1-34) than in controls. The concentration of proline at which half-maximal transport occurred (Km) was unchanged. In cultures treated with cycloheximide alone, proline transport decreased as a first-order exponential with a half-life of 250-280 min. Parathyroid hormone significantly reduced this decline, increasing the half-life of proline transport activity about fourfold. These effects were duplicated by 1 mM DBcAMP. It is concluded that bPTH-(1-34) increases proline transport in osteoblastlike cells by decreasing the degradation of amino acid transport system A proteins. The hormone may also affect the synthesis of these molecules. These effects appear to be mediated by cAMP.
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Affiliation(s)
- J A Yee
- Department of Cell Biology and Anatomy, Texas Tech University Health Sciences Center, Lubbock 79430
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