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Zhao D, Wu J, Acosta FM, Xu H, Jiang JX. Connexin 43 hemichannels and prostaglandin E 2 release in anabolic function of the skeletal tissue to mechanical stimulation. Front Cell Dev Biol 2023; 11:1151838. [PMID: 37123401 PMCID: PMC10133519 DOI: 10.3389/fcell.2023.1151838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 04/05/2023] [Indexed: 05/02/2023] Open
Abstract
Bone adapts to changes in the physical environment by modulating remodeling through bone resorption and formation to maintain optimal bone mass. As the most abundant connexin subtype in bone tissue, connexin 43 (Cx43)-forming hemichannels are highly responsive to mechanical stimulation by permitting the exchange of small molecules (<1.2 kDa) between bone cells and the extracellular environment. Upon mechanical stimulation, Cx43 hemichannels facilitate the release of prostaglandins E2 (PGE2), a vital bone anabolic factor from osteocytes. Although most bone cells are involved in mechanosensing, osteocytes are the principal mechanosensitive cells, and PGE2 biosynthesis is greatly enhanced by mechanical stimulation. Mechanical stimulation-induced PGE2 released from osteocytic Cx43 hemichannels acts as autocrine effects that promote β-catenin nuclear accumulation, Cx43 expression, gap junction function, and protects osteocytes against glucocorticoid-induced osteoporosis in cultured osteocytes. In vivo, Cx43 hemichannels with PGE2 release promote bone formation and anabolism in response to mechanical loading. This review summarizes current in vitro and in vivo understanding of Cx43 hemichannels and extracellular PGE2 release, and their roles in bone function and mechanical responses. Cx43 hemichannels could be a significant potential new therapeutic target for treating bone loss and osteoporosis.
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Affiliation(s)
- Dezhi Zhao
- School of Medicine, Northwest University, Xi’an, China
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, United States
- School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
| | - Jiawei Wu
- School of Medicine, Northwest University, Xi’an, China
| | - Francisca M. Acosta
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, United States
| | - Huiyun Xu
- School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
| | - Jean X. Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, United States
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Kuttappan S, Jo JI, Sabu CK, Menon D, Tabata Y, Nair MB. Bioinspired nanocomposite fibrous scaffold mediated delivery of ONO-1301 and BMP2 enhance bone regeneration in critical sized defect. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2020; 110:110591. [DOI: 10.1016/j.msec.2019.110591] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 12/19/2019] [Accepted: 12/21/2019] [Indexed: 01/08/2023]
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Zippelius T, Hoff P, Strube P, Schiffner R, Maslaris A, Matziolis G, Röhner E. Effects of iloprost on human mature osteoblasts in vitro. J Back Musculoskelet Rehabil 2020; 32:897-903. [PMID: 30958330 DOI: 10.3233/bmr-171043] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND AND OBJECTIVES Bone marrow oedema is a multifactorial conditioned illness. Alongside any strain relief of an affected joint, treatment with Iloprost also belongs to the choice of cures. In past studies, a modulatory effect on bone could be shown. The hypothesis of the present work is that Iloprost has a growth-stimulating effect on osteoblasts in vitro. METHODS Human osteoblasts were isolated and cultivated. Subsequently, the cells were treated with Iloprost in bioavailable concentrations. Alterations of the cell structure were examined by means of light microscopy. A regulation of the number of vital cells was carried out by using a CASY cell counter. Possible cell impairment after Iloprost treatment was analysed by means of XTT Elisa as well as FDA and PI staining via fluorescence microscopy. RESULTS Using light microscopy, no changes in cell structure could be observed. With the CASY cell counter, no increase in the numbers of osteoblasts appeared after Iloprost treatment. Also, XTT Elisas and fluorescence microscopy did not reveal any cell impairment due to Iloprost. CONCLUSION Our results could not confirm a modulatory effect in mature osteoblasts. On the basis of the present work we could not verify any growth-stimulating effect by Iloprost in mature osteoblasts in vitro. Admittedly, effects had been shown previously during osteogenesis, but we do exclude an effect on mature osteoblasts which have already differentiated.
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Affiliation(s)
- Timo Zippelius
- Orthopaedic Department of the Waldkliniken Eisenberg, Orthopaedic Professorship of the University Hospital Jena, Eisenberg, Germany
| | - Paula Hoff
- Orthopaedic Department of the Waldkliniken Eisenberg, Orthopaedic Professorship of the University Hospital Jena, Eisenberg, Germany.,Endokrinologikum Berlin, Berlin, Germany.,Department of Rheumatology and Clinical Immunology, Charité University Hospital, Berlin, Germany
| | - Patrick Strube
- Orthopaedic Department of the Waldkliniken Eisenberg, Orthopaedic Professorship of the University Hospital Jena, Eisenberg, Germany
| | - René Schiffner
- Orthopaedic Department of the Waldkliniken Eisenberg, Orthopaedic Professorship of the University Hospital Jena, Eisenberg, Germany
| | - Alexander Maslaris
- Orthopaedic Department of the Waldkliniken Eisenberg, Orthopaedic Professorship of the University Hospital Jena, Eisenberg, Germany
| | - Georg Matziolis
- Orthopaedic Department of the Waldkliniken Eisenberg, Orthopaedic Professorship of the University Hospital Jena, Eisenberg, Germany
| | - Eric Röhner
- Orthopaedic Department of the Waldkliniken Eisenberg, Orthopaedic Professorship of the University Hospital Jena, Eisenberg, Germany
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Whole-blood PUFA and associations with markers of nutritional and health status in acutely malnourished children in Cambodia. Public Health Nutr 2020; 23:974-986. [PMID: 31973779 DOI: 10.1017/s1368980019003744] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE To measure fatty acid composition, particularly whole-blood PUFA content, in acutely malnourished children and identify associations with markers of nutritional and health status. DESIGN PUFA were assessed in dried blood spots obtained from a cross-sectional study. Nutritional and health status were assessed by anthropometry, haemoglobinopathies, inflammation and blood counts. SETTING Cambodia. PARTICIPANTS The study was conducted with 174 children aged 0·5-18 years with acute malnutrition. RESULTS Among total fatty acids (FA), the relative percentage of total PUFA was 20 % FA, with 14 % of the children having very low PUFA (mead acid (MA):arachidonic acid (AA) >0·02, n-6 docosapentaenoic acid:DHA >0·2 and total n-6:n-3 PUFA >10·5). Wasting was not associated with any PUFA. Stunting and low height were consistently positively associated with total PUFA and positively with n-6 PUFA. Height was positively associated with n-3 long-chain PUFA (LCPUFA). The presence of haemoglobinopathies or inflammation was positively associated with MA:AA, but not total PUFA. Elevated blood platelet counts were positively correlated with linoleic acid and appeared to be influenced by anaemia (P = 0·010) and inflammation (P = 0·002). Monocyte counts were high during inflammation (P = 0·052) and correlated positively with n-6 LCPUFA and n-3 LCPUFA. CONCLUSIONS Children with acute malnutrition or stunting had low PUFA, while elevated platelets and monocytes were associated with high PUFA. In acutely malnourished children, inflammation could lead to elevated blood cell counts resulting in increased whole-blood PUFA which does not reflect dietary intake or nutritional status.
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Kuttappan S, Jo JI, Menon D, Ishimoto T, Nakano T, Nair SV, Tabata Y, Nair MB. ONO-1301 loaded nanocomposite scaffolds modulate cAMP mediated signaling and induce new bone formation in critical sized bone defect. Biomater Sci 2019; 8:884-896. [PMID: 31822874 DOI: 10.1039/c9bm01352k] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Recent studies on bone regeneration demonstrate the use of low cost and stable small molecules, which avoid the adverse effect and high cost of growth factors. Herein, we investigate the chemotactic, angiogenic and osteoinductive potential of a prostacyclin analogue, ONO-1301, when delivered through a biomimetic nanocomposite scaffold (nanohydroxyapatite-gelatin matrix reinforced with fibers) for bone tissue regeneration. The small molecule was loaded onto the scaffold in three different concentrations. There was burst release from all the groups of scaffolds within 24 h followed by a sustained release up to 14 days, but the concentration was dependent on loading percentage. ONO-1301 loaded scaffolds augmented the migration, proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs), but increasing the concentration beyond a certain dose did not show any effect. The osteoinduction was mediated through the prostaglandin I2 receptor and cyclic AMP (cAMP) signaling pathway. They also promoted new bone formation in large sized calvarial defects in rats compared to the scaffold alone, but did not show any impact on angiogenesis. Hence, this study suggests the chemotactic and osteoinductive capability of ONO-1301 for the repair and regeneration of critical sized bone defects.
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Affiliation(s)
- Shruthy Kuttappan
- Centre for Nanosciences and Molecular Medicine, Amrita Institute of Medical Sciences and Research Center, Amrita Vishwa Vidyapeetham, India.
| | - Jun-Ichiro Jo
- Laboratory of Biomaterials, Institute for Frontier Life and Medical Sciences, Kyoto University, Japan.
| | - Deepthy Menon
- Centre for Nanosciences and Molecular Medicine, Amrita Institute of Medical Sciences and Research Center, Amrita Vishwa Vidyapeetham, India.
| | - Takuya Ishimoto
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, Osaka, Japan
| | - Takayoshi Nakano
- Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, Osaka, Japan
| | - Shantikumar V Nair
- Centre for Nanosciences and Molecular Medicine, Amrita Institute of Medical Sciences and Research Center, Amrita Vishwa Vidyapeetham, India.
| | - Yasuhiko Tabata
- Laboratory of Biomaterials, Institute for Frontier Life and Medical Sciences, Kyoto University, Japan.
| | - Manitha B Nair
- Centre for Nanosciences and Molecular Medicine, Amrita Institute of Medical Sciences and Research Center, Amrita Vishwa Vidyapeetham, India.
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Xiong Y, Yan C, Chen L, Endo Y, Sun Y, Zhou W, Hu Y, Hu L, Chen D, Xue H, Mi B, Liu G. IL-10 induces MC3T3-E1 cells differentiation towards osteoblastic fate in murine model. J Cell Mol Med 2019; 24:1076-1086. [PMID: 31755174 PMCID: PMC6933380 DOI: 10.1111/jcmm.14832] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Revised: 10/04/2019] [Accepted: 10/28/2019] [Indexed: 12/22/2022] Open
Abstract
Interleukin‐10 (IL‐10) displays well‐documented anti‐inflammatory effects, but its effects on osteoblast differentiation have not been investigated. In this study, we found IL‐10 negatively regulates microRNA‐7025‐5p (miR‐7025‐5p), the down‐regulation of which enhances osteoblast differentiation. Furthermore, through luciferase reporter assays, we found evidence that insulin‐like growth factor 1 receptor (IGF1R) is a miR‐7025‐5p target gene that positively regulates osteoblast differentiation. In vivo studies indicated that the pre‐injection of IL‐10 leads to increased bone formation, while agomiR‐7025‐5p injection delays fracture healing. Taken together, these results indicate that IL‐10 induces osteoblast differentiation via regulation of the miR‐7025‐5p/IGF1R axis. IL‐10 therefore represents a promising therapeutic strategy to promote fracture healing.
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Affiliation(s)
- Yuan Xiong
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Chenchen Yan
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Lang Chen
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yori Endo
- Division of Plastic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Yun Sun
- Department of Neurosurgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Wu Zhou
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yiqiang Hu
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Liangcong Hu
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Dong Chen
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hang Xue
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Bobin Mi
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Guohui Liu
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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Li G, Zhang L, Wang D, AIQudsy L, Jiang JX, Xu H, Shang P. Muscle-bone crosstalk and potential therapies for sarco-osteoporosis. J Cell Biochem 2019; 120:14262-14273. [PMID: 31106446 DOI: 10.1002/jcb.28946] [Citation(s) in RCA: 92] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Revised: 04/15/2019] [Accepted: 04/18/2019] [Indexed: 12/17/2022]
Abstract
The nature of muscle-bone crosstalk has been historically considered to be only mechanical, where the muscle is the load applier while bone provides the attachment sites. However, this dogma has been challenged with the emerging notion that bone and muscle act as secretory endocrine organs affect the function of each other. Biochemical crosstalk occurs through myokines such as myostatin, irisin, interleukin (IL)-6, IL-7, IL-15, insulin-like growth factor-1, fibroblast growth factor (FGF)-2, and β-aminoisobutyric acid and through bone-derived factors including FGF23, prostaglandin E2 , transforming growth factor β, osteocalcin, and sclerostin. Aside from the biochemical and mechanical interaction, additional factors including aging, circadian rhythm, nervous system network, nutrition intake, and exosomes also have effects on bone-muscle crosstalk. Here, we summarize the current research progress in the area, which may be conductive to identify potential novel therapies for the osteoporosis and sarcopenia, especially when they develop in parallel.
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Affiliation(s)
- GuoBin Li
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an, Shaanxi, China
| | - Lan Zhang
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an, Shaanxi, China
| | - DongEn Wang
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an, Shaanxi, China
| | - Luban AIQudsy
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an, Shaanxi, China
| | - Jean X Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas
| | - HuiYun Xu
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an, Shaanxi, China
| | - Peng Shang
- Research & Development Institute in Shenzhen, Northwestern Polytechnical University, Shenzhen, Guangdong, China
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Wood CL, Soucek O, Wong SC, Zaman F, Farquharson C, Savendahl L, Ahmed SF. Animal models to explore the effects of glucocorticoids on skeletal growth and structure. J Endocrinol 2018; 236:R69-R91. [PMID: 29051192 DOI: 10.1530/joe-17-0361] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 10/17/2017] [Indexed: 12/17/2022]
Abstract
Glucocorticoids (GCs) are effective for the treatment of many chronic conditions, but their use is associated with frequent and wide-ranging adverse effects including osteoporosis and growth retardation. The mechanisms that underlie the undesirable effects of GCs on skeletal development are unclear, and there is no proven effective treatment to combat them. An in vivo model that investigates the development and progression of GC-induced changes in bone is, therefore, important and a well-characterized pre-clinical model is vital for the evaluation of new interventions. Currently, there is no established animal model to investigate GC effects on skeletal development and there are pros and cons to consider with the different protocols used to induce osteoporosis and growth retardation. This review will summarize the literature and highlight the models and techniques employed in experimental studies to date.
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Affiliation(s)
- Claire L Wood
- Division of Developmental BiologyRoslin Institute, University of Edinburgh, Edinburgh, UK
| | - Ondrej Soucek
- Department of Paediatrics2nd Faculty of Medicine, Charles University in Prague and Motol University Hospital, Prague, Czech Republic
- Department of Women's and Children's HealthKarolinska Institutet and Pediatric Endocrinology Unit, Karolinska University Hospital, Stockholm, Sweden
| | - Sze C Wong
- Developmental Endocrinology Research GroupSchool of Medicine, University of Glasgow, Glasgow, UK
| | - Farasat Zaman
- Department of Women's and Children's HealthKarolinska Institutet and Pediatric Endocrinology Unit, Karolinska University Hospital, Stockholm, Sweden
| | - Colin Farquharson
- Division of Developmental BiologyRoslin Institute, University of Edinburgh, Edinburgh, UK
| | - Lars Savendahl
- Department of Women's and Children's HealthKarolinska Institutet and Pediatric Endocrinology Unit, Karolinska University Hospital, Stockholm, Sweden
| | - S Faisal Ahmed
- Developmental Endocrinology Research GroupSchool of Medicine, University of Glasgow, Glasgow, UK
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Abstract
PURPOSE OF REVIEW The role of bone-derived factors in regulation of skeletal muscle function is an important emerging aspect of research into bone-muscle crosstalk. Implications for this area of research are far reaching and include understanding skeletal muscle weakness in cancer, osteoporosis, cachexia, rare diseases of bone, and aging. RECENT FINDINGS Recent research shows that bone-derived factors can lead to changes in the skeletal muscle. These changes can either be anabolic or catabolic, and we focus this review on the role of TGFβ in driving oxidative stress and skeletal muscle weakness in the setting of osteolytic cancer in the bone. The bone is a preferred site for breast cancer metastasis and leads to pathological bone loss. Osteolytic cancer in the bone leads to release of TGFβ from the bone via osteoclast-mediated bone destruction. Our appreciation of crosstalk between the muscle and bone has recently expanded beyond mechanical force-driven events to encompass a variety of signaling factors originating in one tissue and communicating to the other. This review summarizes some previously known mediators of bone-to-muscle signaling and also recent work identifying a new role for bone-derived TGFβ as a cause of skeletal muscle weakness in the setting of osteolytic cancer in the bone. Multiple points of potential therapeutic intervention are discussed.
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Affiliation(s)
- Jenna N Regan
- Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Trupti Trivedi
- Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Theresa A Guise
- Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - David L Waning
- The Pennsylvania State University College of Medicine, 500 University Drive, H166, Rm C4710E, Hershey, PA, 17033, USA.
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Jumbe T, Comstock SS, Hahn SL, Harris WS, Kinabo J, Fenton JI. Whole Blood Levels of the n-6 Essential Fatty Acid Linoleic Acid Are Inversely Associated with Stunting in 2-to-6 Year Old Tanzanian Children: A Cross-Sectional Study. PLoS One 2016; 11:e0154715. [PMID: 27137223 PMCID: PMC4854382 DOI: 10.1371/journal.pone.0154715] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 04/18/2016] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND In Tanzania, 35% of all children below five years of age are stunted. Dietary fatty acids (FA) are critical for growth and development. However, whole blood FA levels in Tanzanian children are poorly described. OBJECTIVE The objectives of this cross-sectional study were to assess 1) whole blood levels of essential fatty acids and 2) the association between whole blood FA levels and growth parameters in Tanzanian children 2-6 years of age. METHODS A drop of blood was collected on an antioxidant treated card and analyzed for FA composition. Weight and height were measured and z-scores calculated. Relationships between FAs and growth parameters were analyzed by linear regression. RESULTS Of the 334 children that participated, 30.3% were stunted. The average whole blood level of Mead acid was 0.15%. The anthropometric z-score height-for-age (HAZ) was inversely associated with Mead acid, the Mead acid to arachidonic acid (T/T) ratio, and total n-9 FA. Additionally, HAZ was positively associated with linoleic acid and total n-6 FA. BMI-for-age was positively associated with oleic acid, total n-9 FA and T/T ratio but inversely associated with arachidonic acid and total n-6 FA. Weight-for-height was inversely associated with arachidonic acid and total n-6 FAs and positively associated with oleic acid and total n-9 FA. Weight-for-age was not associated with any FA tested. Total n-3 FAs were not associated with any growth parameters measured. CONCLUSIONS The EFA linoleic acid and the markers of FA deficiency were associated with HAZ, an indicator for stunting in 2-6 year old Tanzanian children. Total n-6, total n-9, and a number of individual FAs were associated with growth. Increasing dietary intake of EFA and n-6 FAs may be a strategy to combat stunting in this population.
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Affiliation(s)
- Theresia Jumbe
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan, United States of America
- Sokoine University of Agriculture, Morogoro, Tanzania
| | - Sarah S. Comstock
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan, United States of America
| | - Samantha L. Hahn
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan, United States of America
| | - William S. Harris
- Sanford School of Medicine, University of South Dakota and OmegaQuant Analytics, LLC, Sioux Falls, South Dakota, United States of America
| | - Joyce Kinabo
- Sokoine University of Agriculture, Morogoro, Tanzania
| | - Jenifer I. Fenton
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan, United States of America
- * E-mail:
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Regan JN, Waning DL, Guise TA. Skeletal muscle Ca(2+) mishandling: Another effect of bone-to-muscle signaling. Semin Cell Dev Biol 2015; 49:24-9. [PMID: 26593325 DOI: 10.1016/j.semcdb.2015.11.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 11/13/2015] [Indexed: 01/06/2023]
Abstract
Our appreciation of crosstalk between muscle and bone has recently expanded beyond mechanical force-driven events to encompass a variety of signaling factors originating in one tissue and communicating to the other. While the recent identification of new 'myokines' has shifted some focus to the role of muscle in this partnership, bone-derived factors and their effects on skeletal muscle should not be overlooked. This review summarizes some previously known mediators of bone-to-muscle signaling and also recent work identifying a new role for bone-derived TGF-β as a cause of skeletal muscle weakness in the setting of cancer-induced bone destruction. Oxidation of the ryanodine receptor/calcium release channel (RyR1) in skeletal muscle occurs via a TGF-β-Nox4-RyR1 axis and leads to calcium mishandling and decreased muscle function. Multiple points of potential therapeutic intervention were identified, from preventing the bone destruction to stabilizing the RYR1 calcium channel. This new data reinforces the concept that bone can be an important source of signaling factors in pathphysiological settings.
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Affiliation(s)
- Jenna N Regan
- Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - David L Waning
- Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Theresa A Guise
- Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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12
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Riquelme MA, Burra S, Kar R, Lampe PD, Jiang JX. Mitogen-activated Protein Kinase (MAPK) Activated by Prostaglandin E2 Phosphorylates Connexin 43 and Closes Osteocytic Hemichannels in Response to Continuous Flow Shear Stress. J Biol Chem 2015; 290:28321-28328. [PMID: 26442583 DOI: 10.1074/jbc.m115.683417] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Indexed: 01/04/2023] Open
Abstract
Cx43 hemichannels serve as a portal for the release of prostaglandins, a critical process in mediating biological responses of mechanical loading on bone formation and remodeling. We have previously observed that fluid flow shear stress (FFSS) opens hemichannels; however, sustained FFSS results in hemichannel closure, as continuous opening of hemichannels is detrimental to cell viability and bone remodeling. However, the mechanism that regulates the closure of the hemichannels is unknown. Here, we show that activation of p44/42 ERK upon continuous FFSS leads to Cx43 phosphorylation at Ser(279)-Ser(282), sites known to be phosphorylated sites by p44/42 MAPK. Incubation of osteocytic MLO-Y4 cells with conditioned media (CM) collected after continuous FFSS increased MAPK-dependent phosphorylation of Cx43. CM treatment inhibited hemichannel opening and this inhibition was reversed when cells were pretreated with the MAPK pathway inhibitor. We found that prostaglandin E2 (PGE2) accumulates in the CM in a time-dependent manner. Treatment with PGE2 increased phospho-p44/42 ERK levels and also Cx43 phosphorylation at Ser(279)-Ser(282) sites. Depletion of PGE2 from CM, and pre-treatment with a p44/42 ERK pathway-specific inhibitor, resulted in a complete inhibition of ERK-dependent Cx43 phosphorylation and attenuated the inhibition of hemichannels by CM and PGE2. Consistently, the opening of hemichannels by FFSS was blocked by PGE2 and CM and this blockage was reversed by U0126 and the CM depleted of PGE2. A similar observation was also obtained in isolated primary osteocytes. Together, results from this study suggest that extracellular PGE2 accumulated after continuous FFSS is responsible for activation of p44/42 ERK signaling and subsequently, direct Cx43 phosphorylation by activated ERK leads to hemichannel closure.
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Affiliation(s)
- Manuel A Riquelme
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229-3900
| | - Sirisha Burra
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229-3900
| | - Rekha Kar
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229-3900
| | - Paul D Lampe
- Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109
| | - Jean X Jiang
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229-3900.
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Factors affecting the incidence of aseptic nonunion after surgical fixation of humeral diaphyseal fracture. J Orthop Sci 2014; 19:973-7. [PMID: 25196794 DOI: 10.1007/s00776-014-0640-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Accepted: 08/19/2014] [Indexed: 10/24/2022]
Abstract
BACKGROUND Although aseptic nonunion of humeral diaphyseal fracture is rare, it often is debilitating for the patient. Treatment is challenging for the surgeon when nonunion occurs. The purpose of this study was to analyze and identify independent risk factors for aseptic nonunion among patients with humeral diaphyseal fracture undergoing surgical fixation. METHODS The medical records of all humeral diaphyseal fracture patients who underwent surgical fixation from January 2005 to January 2011 were reviewed to identify those who developed aseptic nonunion. We performed univariate and multivariate logistic regression to identify independent associations of potential risk factors for aseptic nonunion among patients with surgical humeral diaphyseal fracture. RESULTS A total of 686 patients were identified, with 659 meeting our inclusion criteria. Among these 659 cases there were 24 cases of septic nonunion, an incidence of 3.6%. The patients were followed for 9-24 months, with an average follow-up period of 14.8 months. In the final regression model, advanced age (odds ratio, 1.09; 95% CI: 1.03-1.14, P = 0.001), smoking (odds ratio, 5.34; 95% CI: 1.05-27.00, P = 0.043), use of NSAIDs (odds ratio, 2.51; 95% CI: 1.80-3.50, P < 0.001), and ASA score (odds ratio, 3.04; 95% CI: 1.06-8.74, P = 0.039) were risk factors for aseptic nonunion of humeral diaphyseal fracture after surgical fixation. CONCLUSIONS This analysis confirms advanced age, smoking, use of NSAIDs, and ASA score were related to an increased risk of aseptic nonunion of humeral diaphyseal fracture after surgical fixation. Patients who have the risk factors identified in this study should be counseled about the possibility of aseptic nonunion occurring after surgical fixation.
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Zhang J, Zhang HY, Zhang M, Qiu ZY, Wu YP, Callaway DA, Jiang JX, Lu L, Jing L, Yang T, Wang MQ. Connexin43 hemichannels mediate small molecule exchange between chondrocytes and matrix in biomechanically-stimulated temporomandibular joint cartilage. Osteoarthritis Cartilage 2014; 22:822-30. [PMID: 24704497 PMCID: PMC4706739 DOI: 10.1016/j.joca.2014.03.017] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Revised: 03/14/2014] [Accepted: 03/22/2014] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Connexin (Cx) 43 hemichannels play a role in mechanotransduction. This study was undertaken in order to determine if Cx43 hemichannels were activated in rat temporomandibular joint (TMJ) chondrocytes under mechanical stimulation. METHODS Sprague-Dawley rats were stimulated dental-mechanically. Cx43 expression in rat TMJ cartilage was determined with immunohistochemistry and real-time PCR, and Cx43 hemichannel opening was evaluated by the extra- and intracellular levels of prostaglandin E2 (PGE2). Both primary rat chondrocytes and ATDC5 cells were treated with fluid flow shear stress (FFSS) to induce hemichannel opening. The Cx43 expression level was then determined by real-time PCR or Western blotting, and the extent of Cx43 hemichannel opening was evaluated by measuring both PGE2 release and cellular dye uptake. RESULTS Cx43 expression and intra- and extracellular PGE2 levels were increased in mechanically-stimulated rat TMJ cartilage compared to the unstimulated control. The FFSS treatment increased Cx43 expression and induced Cx43 hemichannel opening in primary rat chondrocytes and ATDC5 cells indicated by enhanced PGE2 release and dye uptake. Furthermore, the Cx43 hemichannel opening could be blocked by the addition of 18β-glycyrrhetinic acid, a Cx channel inhibitor, Cx43-targeting siRNA, or by withdrawal of FFSS stimulation. The migration of cytosolic Cx43 protein to the plasma membrane in ATDC5 cells was still significant after 8 h post 2-h FFSS treatment, and the Cx43 protein level was still high at 48 h, which returned to control levels at 72 h after treatment. CONCLUSION Cx43 hemichannels are activated and mediate small molecule exchange between TMJ chondrocytes and matrix under mechanical stimulation.
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Affiliation(s)
- J Zhang
- State Key Laboratory of Military Stomatology, Department of Oral Anatomy and Physiology, School of Stomatology, Fourth Military Medical University, 145 Changlexi Road, Xi'an, 710032, China
| | - H Y Zhang
- State Key Laboratory of Military Stomatology, Department of Oral Anatomy and Physiology, School of Stomatology, Fourth Military Medical University, 145 Changlexi Road, Xi'an, 710032, China
| | - M Zhang
- State Key Laboratory of Military Stomatology, Department of Oral Anatomy and Physiology, School of Stomatology, Fourth Military Medical University, 145 Changlexi Road, Xi'an, 710032, China
| | - Z Y Qiu
- College of Life Science, Shaanxi Normal University, Xi'an, 710062, China
| | - Y P Wu
- Institute of Orthopaedics, Xijing Hospital, Fourth Military Medical University, 15 Changlexi Road, Xi'an, 710032, China
| | - D A Callaway
- Department of Biochemistry, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - J X Jiang
- Department of Biochemistry, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - L Lu
- State Key Laboratory of Military Stomatology, Department of Oral Anatomy and Physiology, School of Stomatology, Fourth Military Medical University, 145 Changlexi Road, Xi'an, 710032, China
| | - L Jing
- State Key Laboratory of Military Stomatology, Department of Oral Anatomy and Physiology, School of Stomatology, Fourth Military Medical University, 145 Changlexi Road, Xi'an, 710032, China
| | - T Yang
- State Key Laboratory of Military Stomatology, Department of Oral Anatomy and Physiology, School of Stomatology, Fourth Military Medical University, 145 Changlexi Road, Xi'an, 710032, China
| | - M Q Wang
- State Key Laboratory of Military Stomatology, Department of Oral Anatomy and Physiology, School of Stomatology, Fourth Military Medical University, 145 Changlexi Road, Xi'an, 710032, China.
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Lo KWH, Ashe KM, Kan HM, Laurencin CT. The role of small molecules in musculoskeletal regeneration. Regen Med 2013; 7:535-49. [PMID: 22817627 DOI: 10.2217/rme.12.33] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The uses of bone morphogenetic proteins and parathyroid hormone therapeutics are fraught with several fundamental problems, such as cost, protein stability, immunogenicity, contamination and supraphysiological dosage. These downsides may effectively limit their more universal use. Therefore, there is a clear need for alternative forms of biofactors to obviate the drawbacks of protein-based inductive factors for bone repair and regeneration. Our group has studied small molecules with the capacity to regulate osteoblast differentiation and mineralization because their inherent physical properties minimize limitations observed in protein growth factors. For instance, in general, small molecule inducers are usually more stable, highly soluble, nonimmunogenic, more affordable and require lower dosages. Small molecules with the ability to induce osteoblastic differentiation may represent the next generation of bone regenerative medicine. This review describes efforts to develop small molecule-based biofactors for induction, paying specific attention to their novel roles in bone regeneration.
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Affiliation(s)
- Kevin W-H Lo
- Institute for Regenerative Engineering, University of Connecticut Health Center, School of Medicine, Farmington, CT 06030, USA
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Li KH, Cheng L, Zhu Y, Deng GB, Long HT. Effects of a selective cyclooxygenase-2 inhibitor (celecoxib) on fracture healing in rats. Indian J Orthop 2013; 47:395-401. [PMID: 23960285 PMCID: PMC3745695 DOI: 10.4103/0019-5413.114930] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND Several studies suggested that celecoxib interferes with bone healing while others contradict these findings. This study was conducted to investigate the effects of celecoxib on bone healing in rats femur mold with a dose based on body surface area conversion. MATERIALS AND METHODS 72 adult female Sprague Dawley rats were randomly divided into three groups after the internal fixation operation of nondisplaced transverse mid diaphyseal fractures of the right femurs. Each group was treated with 1% methylcellulose, celecoxib (21 mg/kg/d) for 1 week, or celecoxib (21 mg/kg/d) for 4 weeks after surgeries respectively. Bone healing scores and callus formation were evaluated by radiographs at 3, 4, 6 weeks after surgeries. Half of these rats were sacrificed for histological analysis at 4 weeks after surgery. The remaining fractured femurs were evaluated by biomechanical tests at 6 weeks after surgery. RESULTS The mean radiographic scores for fracture healing of both short and long term groups were lower than that of the control group and the differences among the three groups were statistically significant (P < 0.05) at 3, 4, 6 weeks after surgery. The mean bone trabecula density of both groups was smaller than that of the control group and the differences were also statistically significant (P < 0.05) at 4 week. The maximum load, total energy and stiffness in both the short term and long term groups were significantly decreased compared with those in the control group (P < 0.05) at 6 week. CONCLUSION Both short term and long term sustained use of celecoxib in rat models has significantly inhibitory effects on rat fracture healing.
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Affiliation(s)
- Kang-Hua Li
- Department of Orthopaedics, Xiangya Hospital, Central South University, Changsha, China
| | - Liang Cheng
- Department of Orthopaedics, Xiangya Hospital, Central South University, Changsha, China
| | - Yong Zhu
- Department of Orthopaedics, Xiangya Hospital, Central South University, Changsha, China,Address for correspondence: Dr. Yong Zhu, Department of Orthopaedics, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China. E-mail:
| | - Guo-Bing Deng
- Department of Orthopaedics, Chenzhou People's Hospital, Chenzhou, 423000, Hunan, China
| | - Hai-Tao Long
- Department of Orthopaedics, Xiangya Hospital, Central South University, Changsha, China
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Bacabac RG, Van Loon JJWA. Stress Response by Bone Cells and Implications on Microgravity Environment. Clin Rev Bone Miner Metab 2011. [DOI: 10.1007/s12018-011-9082-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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18
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Sanchez C, Gabay O, Salvat C, Henrotin YE, Berenbaum F. Mechanical loading highly increases IL-6 production and decreases OPG expression by osteoblasts. Osteoarthritis Cartilage 2009; 17:473-81. [PMID: 18974013 DOI: 10.1016/j.joca.2008.09.007] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Accepted: 09/12/2008] [Indexed: 02/02/2023]
Abstract
OBJECTIVES In osteoarthritis (OA), mechanical factors play a key role, not only in cartilage degradation, but also in subchondral bone sclerosis. The aim of this study was to develop on original compression model for studying the effect of mechanical stress on osteoblasts. MATERIALS AND METHODS We investigate the effects of compression on primary calvaria osteoblasts isolated from newborn mice and cultured for 28 days in monolayer. At the end of this period, osteoblasts were embedded in a newly synthesized extracellular matrix which formed a three-dimensional membrane. This membrane was then submitted to compression in Biopress Flexercell plates (1-1.7 MPa compressions at 1 Hz frequency) during 1-8h. The expression of 20 genes was investigated by real time reverse transcriptase polymerase chain reaction. Interleukin (IL)-6, matrix metalloproteinase (MMP)-3 and prostaglandin (PG)E(2) were assayed in the culture medium by specific immunoassays. RESULTS The compression highly increased IL-6 and cyclooxygenase (COX)-2 mRNA levels in osteoblasts. In parallel, increased amount of IL-6 and PGE(2) was found in the supernatant of loaded osteoblasts. This stimulation reached a maximum after 4h of 10% compression. MMP-2, MMP-3, and MMP-13 mRNA levels were also increased by compressive stress, while 15-hydroxyprostaglandin-dehydrogenase and osteoprotegerin (OPG) start to decrease at hour 4. COX-1, microsomial PG E synthase-1 (mPGES1), mPGES2 and cytosolic PGES and receptor activator of nuclear factor ligand (RANKL) were unmodified. Finally, we observed that alpha 5 beta 1 integrin, intracellular Ca(++), nuclear factor-kappaB and extracellular signal-regulated kinase 1/2 pathways were involved in the compression-induced IL-6 and PGE(2) production. IL-6 neutralizing antibodies and piroxicam inhibited the decrease OPG expression, but did not modify RANKL mRNA level, indicating that IL-6 and PGE(2) induce a decrease of the OPG/RANKL ratio. CONCLUSION This work demonstrates that IL-6 is mechano-sensitive cytokine and probably a key factor in the biomechanical control of bone remodeling in OA.
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Affiliation(s)
- C Sanchez
- Bone and Cartilage Metabolism Research Unit, University of Liège, Belgium
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19
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Sanchez C, Deberg MA, Bellahcène A, Castronovo V, Msika P, Delcour JP, Crielaard JM, Henrotin YE. Phenotypic characterization of osteoblasts from the sclerotic zones of osteoarthritic subchondral bone. ACTA ACUST UNITED AC 2008; 58:442-55. [DOI: 10.1002/art.23159] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Murnaghan M, Li G, Marsh DR. Nonsteroidal anti-inflammatory drug-induced fracture nonunion: an inhibition of angiogenesis? J Bone Joint Surg Am 2006; 88 Suppl 3:140-7. [PMID: 17079380 DOI: 10.2106/jbjs.f.00454] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND Approximately 5% to 10% of fractures may result in delayed union or nonunion. The results of research done over the past three decades have shown that the use of nonsteroidal anti-inflammatory drugs (NSAIDs) has an inhibitory effect on fracture repair, but the exact mechanism of action remains to be elucidated. Cancer research has identified that NSAIDs impede cell proliferation by inhibiting angiogenesis. It is proposed that a similar mechanism occurs in the induction of NSAID-induced nonunions. This hypothesis was investigated in a randomized placebo-controlled trial of the NSAID rofecoxib with use of a murine femoral fracture model. METHODS Two hundred and forty mice were randomized to receive either the nonsteroidal anti-inflammatory drug rofecoxib (5 mg/kg orally) in a 0.5% methylcellulose solution (the NSAID group) or the 0.5% methylcellulose solution only (the control group). Two hundred and thirty-five of the 240 mice underwent surgery to induce an open transverse middiaphyseal femoral fracture, which was then treated with use of a custom-made external fixator. Five additional animals underwent sham surgery with no fracture induced. Outcomes measures included radiographic assessment, histologic analysis, biomechanical testing, and use of laser Doppler flowmetry to assess blood flow across the fracture gap. RESULTS Radiography revealed similar healing patterns in both groups; however, at the later stages (day 32), the NSAID group had poorer healing. Histological analysis demonstrated that the control animals healed quicker (at days 24 and 32) and had more callus and less fibrous tissue (at days 8 and 32) than the NSAID animals did. Biomechanical testing found that the control animals were stronger at day 32. Both groups exhibited a similar pattern of blood flow; however, the NSAID group exhibited a lower median flow from day 4 onward (significant at days 4, 16, and 24). Positive correlations were demonstrated between both histological and radiographic assessments of healing and increasing blood flow. NSAID-treated animals exhibited lower blood flow and poorer healing by all parameters. Regression analysis, however, demonstrated that the negative effect of NSAIDs on fracture repair is independent of its inhibitory action on blood flow. CONCLUSIONS Following the development of a novel method of analyzing functional vascularity across a fracture gap, we have demonstrated that the cyclooxygenase-2 (COX-2) inhibitor rofecoxib has a significant negative effect on blood flow across the fracture gap as well as an inhibiting effect on fracture repair. CLINICAL RELEVANCE COX-2 inhibitors are marketed as having low side-effect profiles. We propose that these drugs should be used with caution in all patients following osseous trauma and, in particular, after injuries that may already predispose a fracture to a delayed union due to osseous, vascular, or patient-related factors.
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Affiliation(s)
- Mark Murnaghan
- SpR in Department of Trauma and Orthopaedic Surgery, Queen's University Belfast, Musgrave Park Hospital, 20 Stockman's Lane, Belfast BT9 7JB, Northern Ireland, United Kingdom.
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Cherian PP, Siller-Jackson AJ, Gu S, Wang X, Bonewald LF, Sprague E, Jiang JX. Mechanical strain opens connexin 43 hemichannels in osteocytes: a novel mechanism for the release of prostaglandin. Mol Biol Cell 2005; 16:3100-6. [PMID: 15843434 PMCID: PMC1165395 DOI: 10.1091/mbc.e04-10-0912] [Citation(s) in RCA: 372] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Mechanosensing bone osteocytes express large amounts of connexin (Cx)43, the component of gap junctions; yet, gap junctions are only active at the small tips of their dendritic processes, suggesting another function for Cx43. Both primary osteocytes and the osteocyte-like MLO-Y4 cells respond to fluid flow shear stress by releasing intracellular prostaglandin E2 (PGE2). Cells plated at lower densities release more PGE2 than cells plated at higher densities. This response was significantly reduced by antisense to Cx43 and by the gap junction and hemichannel inhibitors 18 beta-glycyrrhetinic acid and carbenoxolone, even in cells without physical contact, suggesting the involvement of Cx43-hemichannels. Inhibitors of other channels, such as the purinergic receptor P2X7 and the prostaglandin transporter PGT, had no effect on PGE2 release. Cell surface biotinylation analysis showed that surface expression of Cx43 was increased by shear stress. Together, these results suggest fluid flow shear stress induces the translocation of Cx43 to the membrane surface and that unapposed hemichannels formed by Cx43 serve as a novel portal for the release of PGE2 in response to mechanical strain.
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Affiliation(s)
- Priscilla P Cherian
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX 78229-3900, USA
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Abstract
The strength and integrity of our bones depends on maintaining a delicate balance between bone resorption by osteoclasts and bone formation by osteoblasts. As we age or as a result of disease, this delicate balancing act becomes tipped in favor of osteoclasts so that bone resorption exceeds bone formation, rendering bones brittle and prone to fracture. A better understanding of the biology of osteoclasts and osteoblasts is providing opportunities for developing therapeutics to treat diseases of bone. Drugs that inhibit the formation or activity of osteoclasts are valuable for treating osteoporosis, Paget's disease, and inflammation of bone associated with rheumatoid arthritis or periodontal disease. Far less attention has been paid to promoting bone formation with, for example, growth factors or hormones, an approach that would be a valuable adjunct therapy for patients receiving inhibitors of bone resorption.
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Affiliation(s)
- G A Rodan
- Merck Research Laboratories, West Point, PA 19486, USA. St. Vincent's Institute of Medical Research, Melbourne 3065, Australia.
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Machwate M, Rodan SB, Rodan GA, Harada SI. Sphingosine kinase mediates cyclic AMP suppression of apoptosis in rat periosteal cells. Mol Pharmacol 1998; 54:70-7. [PMID: 9658191 DOI: 10.1124/mol.54.1.70] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Prostaglandin E stimulates bone formation in humans and animals, and increases intracellular cAMP in osteoblastic cells. We found that cAMP inhibits apoptosis in osteoblastic cells, and examined the mechanism of this effect. We report that the cAMP elevating agent, forskolin, increases cell number in the rat periosteal cell line (RP-11), by suppressing apoptosis in a cell type-specific manner. In RP-11, forskolin transiently up-regulates extracellular signal-regulated kinase activity, a known suppressor of apoptosis. PD98059, a selective inhibitor of the extracellular signal-regulated kinase pathway, only partially reverses the antiapoptotic effect of forskolin, which suggests an additional mechanism for cAMP action. We found that forskolin stimulates cytosolic sphingosine kinase (SPK) activity in these cells; in two other osteoblastic cell lines, however, forskolin does not suppress apoptosis. In contrast to the partial opposing effect of PD98059 to forskolin action, N, N-dimethylsphingosine, a specific inhibitor of SPK, completely reverses the antiapoptotic effect of forskolin, and has no effect on apoptosis in the absence of forskolin. These findings show for the first time that cAMP activates SPK in a cell-type-specific manner, and suggest that cAMP suppression of apoptosis in RP-11 periosteal cells is mediated by its stimulation of SPK.
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Affiliation(s)
- M Machwate
- Department of Bone Biology and Osteoporosis Research, Merck Research Laboratories, WP26A-1000, West Point, Pennsylvania 19486, USA
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