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Lara-Castillo N, Masunaga J, Brotto L, Vallejo JA, Javid K, Wacker MJ, Brotto M, Bonewald LF, Johnson ML. Muscle secreted factors enhance activation of the PI3K/Akt and β-catenin pathways in murine osteocytes. Bone 2023; 174:116833. [PMID: 37385426 PMCID: PMC10926931 DOI: 10.1016/j.bone.2023.116833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 06/19/2023] [Accepted: 06/25/2023] [Indexed: 07/01/2023]
Abstract
Skeletal muscle and bone interact at the level of mechanical loading through the application of force by muscles to the skeleton and more recently focus has been placed on molecular/biochemical coupling of these two tissues. We sought to determine if muscle and muscle-derived factors were essential to the osteocyte response to loading. Botox® induced muscle paralysis was used to investigate the role of muscle contraction during in vivo tibia compression loading. 5-6 month-old female TOPGAL mice had their right hindlimb muscles surrounding the tibia injected with either BOTOX® or saline. At four days post injections when muscle paralysis peaked, the right tibia was subjected to a single session of in vivo compression loading at ∼2600 με. At 24 h post-load we observed a 2.5-fold increase in β-catenin signaling in osteocytes in the tibias of the saline injected mice, whereas loading of tibias from Botox® injected mice failed to active β-catenin signaling in osteocytes. This suggests that active muscle contraction produces a factor(s) that is necessary for or conditions the osteocyte's ability to respond to load. To further investigate the role of muscle derived factors, MLO-Y4 osteocyte-like cells and a luciferase based β-catenin reporter (TOPflash-MLO-Y4) cell line we developed were treated with conditioned media (CM) from C2C12 myoblasts (MB) and myotubes (MT) and ex vivo contracted Extensor Digitorum Longus (EDL) and Soleus (Sol) muscles under static or loading conditions using fluid flow shear stress (FFSS). 10 % C2C12 myotube CM, but not myoblast or NIH3T3 fibroblast cells CM, induced a rapid activation of the Akt signaling pathway, peaking at 15 min and returning to baseline by 1-2 h under static conditions. FFSS applied to MLO-Y4 cells for 2 h in the presence of 10 % MT-CM resulted in a 6-8 fold increase in pAkt compared to a 3-4 fold increase under control or when exposed to 10 % MB-CM. A similar response was observed in the presence of 10 % EDL-CM, but not in the presence of 10 % Sol-CM. TOPflash-MLO-Y4 cells were treated with 10 ng/ml Wnt3a in the presence or absence of MT-CM. While MT-CM resulted in a 2-fold activation and Wnt3a produced a 10-fold activation, the combination of MT-CM + Wnt3a resulted in a 25-fold activation of β-catenin signaling, implying a synergistic effect of factors in MT-CM with Wnt3a. These data provide clear evidence that specific muscles and myotubes produce factors that alter important signaling pathways involved in the response of osteocytes to mechanical load. These data strongly suggest that beyond mechanical loading there is a molecular coupling of muscle and bone.
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Affiliation(s)
- N Lara-Castillo
- Department of Oral and Craniofacial Sciences, UMKC School of Dentistry, 650 East 25th Street, Kansas City, MO 64108, United States of America.
| | - J Masunaga
- Department of Oral and Craniofacial Sciences, UMKC School of Dentistry, 650 East 25th Street, Kansas City, MO 64108, United States of America
| | - L Brotto
- Bone-Muscle Research Center, College of Nursing and Health Innovation, University of Texas at Arlington, 411 S. Nedderman Dr, Arlington, TX 76019, United States of America
| | - J A Vallejo
- Department of Oral and Craniofacial Sciences, UMKC School of Dentistry, 650 East 25th Street, Kansas City, MO 64108, United States of America; Department of Biomedical Sciences, UMKC School of Medicine, 2411 Holmes, Kansas City, MO 64108, United States of America
| | - K Javid
- Department of Oral and Craniofacial Sciences, UMKC School of Dentistry, 650 East 25th Street, Kansas City, MO 64108, United States of America
| | - M J Wacker
- Department of Biomedical Sciences, UMKC School of Medicine, 2411 Holmes, Kansas City, MO 64108, United States of America
| | - M Brotto
- Department of Biomedical Sciences, UMKC School of Medicine, 2411 Holmes, Kansas City, MO 64108, United States of America
| | - L F Bonewald
- Department of Oral and Craniofacial Sciences, UMKC School of Dentistry, 650 East 25th Street, Kansas City, MO 64108, United States of America; Indiana Center for Musculoskeletal Health, Barnhill Drive, Indianapolis, IN 46202, United States of America
| | - M L Johnson
- Department of Oral and Craniofacial Sciences, UMKC School of Dentistry, 650 East 25th Street, Kansas City, MO 64108, United States of America
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2
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Ma Q, Miri Z, Haugen HJ, Moghanian A, Loca D. Significance of mechanical loading in bone fracture healing, bone regeneration, and vascularization. J Tissue Eng 2023; 14:20417314231172573. [PMID: 37251734 PMCID: PMC10214107 DOI: 10.1177/20417314231172573] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Accepted: 04/13/2023] [Indexed: 05/31/2023] Open
Abstract
In 1892, J.L. Wolff proposed that bone could respond to mechanical and biophysical stimuli as a dynamic organ. This theory presents a unique opportunity for investigations on bone and its potential to aid in tissue repair. Routine activities such as exercise or machinery application can exert mechanical loads on bone. Previous research has demonstrated that mechanical loading can affect the differentiation and development of mesenchymal tissue. However, the extent to which mechanical stimulation can help repair or generate bone tissue and the related mechanisms remain unclear. Four key cell types in bone tissue, including osteoblasts, osteoclasts, bone lining cells, and osteocytes, play critical roles in responding to mechanical stimuli, while other cell lineages such as myocytes, platelets, fibroblasts, endothelial cells, and chondrocytes also exhibit mechanosensitivity. Mechanical loading can regulate the biological functions of bone tissue through the mechanosensor of bone cells intraosseously, making it a potential target for fracture healing and bone regeneration. This review aims to clarify these issues and explain bone remodeling, structure dynamics, and mechano-transduction processes in response to mechanical loading. Loading of different magnitudes, frequencies, and types, such as dynamic versus static loads, are analyzed to determine the effects of mechanical stimulation on bone tissue structure and cellular function. Finally, the importance of vascularization in nutrient supply for bone healing and regeneration was further discussed.
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Affiliation(s)
- Qianli Ma
- Department of Biomaterials, Institute
of Clinical Dentistry, University of Oslo, Norway
- Department of Immunology, School of
Basic Medicine, Fourth Military Medical University, Xi’an, PR China
| | - Zahra Miri
- Department of Materials Engineering,
Isfahan University of Technology, Isfahan, Iran
| | - Håvard Jostein Haugen
- Department of Biomaterials, Institute
of Clinical Dentistry, University of Oslo, Norway
| | - Amirhossein Moghanian
- Department of Materials Engineering,
Imam Khomeini International University, Qazvin, Iran
| | - Dagnjia Loca
- Rudolfs Cimdins Riga Biomaterials
Innovations and Development Centre, Institute of General Chemical Engineering,
Faculty of Materials Science and Applied Chemistry, Riga Technical University, Riga,
Latvia
- Baltic Biomaterials Centre of
Excellence, Headquarters at Riga Technical University, Riga, Latvia
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3
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Ma C, Du T, Niu X, Fan Y. Biomechanics and mechanobiology of the bone matrix. Bone Res 2022; 10:59. [PMID: 36042209 PMCID: PMC9427992 DOI: 10.1038/s41413-022-00223-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 05/13/2022] [Accepted: 05/27/2022] [Indexed: 11/23/2022] Open
Abstract
The bone matrix plays an indispensable role in the human body, and its unique biomechanical and mechanobiological properties have received much attention. The bone matrix has unique mechanical anisotropy and exhibits both strong toughness and high strength. These mechanical properties are closely associated with human life activities and correspond to the function of bone in the human body. None of the mechanical properties exhibited by the bone matrix is independent of its composition and structure. Studies on the biomechanics of the bone matrix can provide a reference for the preparation of more applicable bone substitute implants, bone biomimetic materials and scaffolds for bone tissue repair in humans, as well as for biomimetic applications in other fields. In providing mechanical support to the human body, bone is constantly exposed to mechanical stimuli. Through the study of the mechanobiology of the bone matrix, the response mechanism of the bone matrix to its surrounding mechanical environment can be elucidated and used for the health maintenance of bone tissue and defect regeneration. This paper summarizes the biomechanical properties of the bone matrix and their biological significance, discusses the compositional and structural basis by which the bone matrix is capable of exhibiting these mechanical properties, and studies the effects of mechanical stimuli, especially fluid shear stress, on the components of the bone matrix, cells and their interactions. The problems that occur with regard to the biomechanics and mechanobiology of the bone matrix and the corresponding challenges that may need to be faced in the future are also described.
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Affiliation(s)
- Chunyang Ma
- Key Laboratory of Biomechanics and Mechanobiology (Beihang University), Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100083, China
| | - Tianming Du
- Department of Biomedical Engineering, Faculty of Environment and Life, Beijing University of Technology, Beijing, 100124, China
| | - Xufeng Niu
- Key Laboratory of Biomechanics and Mechanobiology (Beihang University), Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100083, China. .,Research Institute of Beihang University in Shenzhen, Shenzhen, 518057, China.
| | - Yubo Fan
- Key Laboratory of Biomechanics and Mechanobiology (Beihang University), Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100083, China. .,School of Engineering Medicine, Beihang University, Beijing, 100083, China.
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4
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Autophagy Is Possibly Involved in Osteoblast Responses to Mechanical Loadings. Curr Issues Mol Biol 2022; 44:3611-3620. [PMID: 36005143 PMCID: PMC9406517 DOI: 10.3390/cimb44080247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 08/03/2022] [Accepted: 08/04/2022] [Indexed: 11/24/2022] Open
Abstract
Both mechanical loading and autophagy play important roles in regulating bone growth and remodeling, but the relationship between the two remains unclear. In this study, we examined bone structure with micro-CT imaging and measured bone mechanical properties with three-point bending experiments using bones from wild-type (WT) mice and conditional knockout (cKO) mice with Atg7 deletion in their osteoblasts. We found that the knockout mice had significantly less bone volume, bone thickness, bone ultimate breaking force, and bone stiffness compared to wild-type mice. Additionally, bone marrow cells from knockout mice had reduced differentiation and mineralization capacities in terms of alkaline phosphatase and calcium secretion, as well as Runx2 and osteopontin expression. Knockout mice also had significantly less relative bone formation rate due to mechanical loading. Furthermore, we found that the osteoblasts from wild-type mice had stronger responses to mechanical stimulation compared to autophagy-deficient osteoblasts from knockout mice. When inhibiting autophagy with 3 MA in wild-type osteoblasts, we found similar results as we did in autophagy-deficient osteoblasts. We also found that mechanical loading-induced ATP release is able to regulate ERK1/2, Runx2, alkaline phosphatase, and osteopontin activities. These results suggest that the ATP pathway may play an important role in the possible involvement of autophagy in osteoblast mechanobiology.
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5
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Buettmann EG, Goldscheitter GM, Hoppock GA, Friedman MA, Suva LJ, Donahue HJ. Similarities Between Disuse and Age-Induced Bone Loss. J Bone Miner Res 2022; 37:1417-1434. [PMID: 35773785 PMCID: PMC9378610 DOI: 10.1002/jbmr.4643] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 06/17/2022] [Accepted: 06/24/2022] [Indexed: 11/07/2022]
Abstract
Disuse and aging are known risk factors associated with low bone mass and quality deterioration, resulting in increased fracture risk. Indeed, current and emerging evidence implicate a large number of shared skeletal manifestations between disuse and aging scenarios. This review provides a detailed overview of current preclinical models of musculoskeletal disuse and the clinical scenarios they seek to recapitulate. We also explore and summarize the major similarities between bone loss after extreme disuse and advanced aging at multiple length scales, including at the organ/tissue, cellular, and molecular level. Specifically, shared structural and material alterations of bone loss are presented between disuse and aging, including preferential loss of bone at cancellous sites, cortical thinning, and loss of bone strength due to enhanced fragility. At the cellular level bone loss is accompanied, during disuse and aging, by increased bone resorption, decreased formation, and enhanced adipogenesis due to altered gap junction intercellular communication, WNT/β-catenin and RANKL/OPG signaling. Major differences between extreme short-term disuse and aging are discussed, including anatomical specificity, differences in bone turnover rates, periosteal modeling, and the influence of subject sex and genetic variability. The examination also identifies potential shared mechanisms underlying bone loss in aging and disuse that warrant further study such as collagen cross-linking, advanced glycation end products/receptor for advanced glycation end products (AGE-RAGE) signaling, reactive oxygen species (ROS) and nuclear factor κB (NF-κB) signaling, cellular senescence, and altered lacunar-canalicular connectivity (mechanosensation). Understanding the shared structural alterations, changes in bone cell function, and molecular mechanisms common to both extreme disuse and aging are paramount to discovering therapies to combat both age-related and disuse-induced osteoporosis. © 2022 American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Evan G Buettmann
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, USA
| | - Galen M Goldscheitter
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, USA
| | - Gabriel A Hoppock
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, USA
| | - Michael A Friedman
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, USA
| | - Larry J Suva
- Department of Veterinary Physiology and Pharmacology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, USA
| | - Henry J Donahue
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, USA
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6
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Hodgkinson T, Amado IN, O'Brien FJ, Kennedy OD. The role of mechanobiology in bone and cartilage model systems in characterizing initiation and progression of osteoarthritis. APL Bioeng 2022. [DOI: 10.1063/5.0068277] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Affiliation(s)
- Tom Hodgkinson
- Department of Anatomy and Regenerative Medicine, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Isabel N. Amado
- Department of Anatomy and Regenerative Medicine, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Fergal J. O'Brien
- Department of Anatomy and Regenerative Medicine, Royal College of Surgeons in Ireland, Dublin, Ireland
- Advanced Materials Bio-Engineering Research Centre (AMBER), Dublin, Ireland
- Trinity Centre for Biomedical Engineering, Trinity College Dublin, Dublin, Ireland
| | - Oran D. Kennedy
- Department of Anatomy and Regenerative Medicine, Royal College of Surgeons in Ireland, Dublin, Ireland
- Advanced Materials Bio-Engineering Research Centre (AMBER), Dublin, Ireland
- Trinity Centre for Biomedical Engineering, Trinity College Dublin, Dublin, Ireland
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7
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Zhao D, Riquelme MA, Guda T, Tu C, Xu H, Gu S, Jiang JX. Connexin hemichannels with prostaglandin release in anabolic function of bone to mechanical loading. eLife 2022; 11:74365. [PMID: 35132953 PMCID: PMC8824479 DOI: 10.7554/elife.74365] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 01/10/2022] [Indexed: 01/18/2023] Open
Abstract
Mechanical stimulation, such as physical exercise, is essential for bone formation and health. Here, we demonstrate the critical role of osteocytic Cx43 hemichannels in anabolic function of bone in response to mechanical loading. Two transgenic mouse models, R76W and Δ130–136, expressing dominant-negative Cx43 mutants in osteocytes were adopted. Mechanical loading of tibial bone increased cortical bone mass and mechanical properties in wild-type and gap junction-impaired R76W mice through increased PGE2, endosteal osteoblast activity, and decreased sclerostin. These anabolic responses were impeded in gap junction/hemichannel-impaired Δ130–136 mice and accompanied by increased endosteal osteoclast activity. Specific inhibition of Cx43 hemichannels by Cx43(M1) antibody suppressed PGE2 secretion and impeded loading-induced endosteal osteoblast activity, bone formation and anabolic gene expression. PGE2 administration rescued the osteogenic response to mechanical loading impeded by impaired hemichannels. Together, osteocytic Cx43 hemichannels could be a potential new therapeutic target for treating bone loss and osteoporosis.
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Affiliation(s)
- Dezhi Zhao
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, United States.,School of Life Sciences, Northwestern Polytechnical University, Xian, China
| | - Manuel A Riquelme
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, United States
| | - Teja Guda
- Department of Biomedical Engineering and Chemical Engineering, University of Texas at San Antonio, San Antonio, United States
| | - Chao Tu
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, United States.,Department of Orthopedics, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Huiyun Xu
- School of Life Sciences, Northwestern Polytechnical University, Xian, China
| | - Sumin Gu
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, United States
| | - Jean X Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, United States
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8
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An S, Zheng S, Cai Z, Chen S, Wang C, Li Y, Deng Z. Connexin43 in Musculoskeletal System: New Targets for Development and Disease Progression. Aging Dis 2022; 13:1715-1732. [DOI: 10.14336/ad.2022.0421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 04/21/2022] [Indexed: 11/18/2022] Open
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9
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Aguirre JI, Castillo EJ, Kimmel DB. Biologic and pathologic aspects of osteocytes in the setting of medication-related osteonecrosis of the jaw (MRONJ). Bone 2021; 153:116168. [PMID: 34487892 PMCID: PMC8478908 DOI: 10.1016/j.bone.2021.116168] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 08/02/2021] [Accepted: 08/31/2021] [Indexed: 02/08/2023]
Abstract
Medication-related osteonecrosis of the jaw (MRONJ) is a potentially severe, debilitating condition affecting patients with cancer and patients with osteoporosis who have been treated with powerful antiresorptives (pARs) or angiogenesis inhibitors (AgIs). Oral risk factors associated with the development of MRONJ include tooth extraction and inflammatory dental disease (e.g., periodontitis, periapical infection). In bone tissues, osteocytes play a bidirectional role in which they not only act as the "receiver" of systemic signals from blood vessels, such as hormones and drugs, or local signals from the mineralized matrix as it is deformed, but they also play a critical role as "transmitter" of signals to the cells that execute bone modeling and remodeling (osteoclasts, osteoblasts and lining cells). When the survival capacity of osteocytes is overwhelmed, they can die. Osteocyte death has been associated with several pathological conditions. Whereas the causes and mechanisms of osteocyte death have been studied in conditions like osteonecrosis of the femoral head (ONFH), few studies of the causes and mechanisms of osteocyte death have been done in MRONJ. The three forms of cell death that affect most of the different cells in the body (apoptosis, autophagy, and necrosis) have been recognized in osteocytes. Notably, necroptosis, a form of regulated cell death with "a necrotic cell death phenotype," has also been identified as a form of cell death in osteocytes under certain pathologic conditions. Improving the understanding of osteocyte death in MRONJ may be critical for preventing disease and developing treatment approaches. In this review, we intend to provide insight into the biology of osteocytes, cell death, in general, and osteocyte death, in particular, and discuss hypothetical mechanisms involved in osteocyte death associated with MRONJ.
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Affiliation(s)
- J I Aguirre
- Department of Physiological Sciences, University of Florida (UF), Gainesville, FL, United States of America.
| | - E J Castillo
- Department of Physiological Sciences, University of Florida (UF), Gainesville, FL, United States of America.
| | - D B Kimmel
- Department of Physiological Sciences, University of Florida (UF), Gainesville, FL, United States of America
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10
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Dole NS, Yoon J, Monteiro DA, Yang J, Mazur CM, Kaya S, Belair CD, Alliston T. Mechanosensitive miR-100 coordinates TGFβ and Wnt signaling in osteocytes during fluid shear stress. FASEB J 2021; 35:e21883. [PMID: 34569659 PMCID: PMC9153140 DOI: 10.1096/fj.202100930] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 08/12/2021] [Indexed: 11/12/2022]
Abstract
Organism scale mechanical forces elicit cellular scale changes through coordinated regulation of multiple signaling pathways. The mechanisms by which cells integrate signaling to generate a unified biological response remains a major question in mechanobiology. For example, the mechanosensitive response of bone and other tissues requires coordinated signaling by the transforming growth factor beta (TGFβ) and Wnt pathways through mechanisms that are not well‐defined. Here we report a new microRNA‐dependent mechanism that mediates mechanosensitive crosstalk between TGFβ and Wnt signaling in osteocytes exposed to fluid shear stress (FSS). From 60 mechanosensitive microRNA (miRs) identified by small‐RNAseq, miR100 expression is suppressed by in vivo hindlimb loading in the murine tibia and by cellular scale FSS in OCY454 cells. Though FSS activates both TGFβ and Wnt signaling in osteocytes, only TGFβ represses miR‐100 expression. miR‐100, in turn, antagonizes Wnt signaling by targeting and inhibiting expression of Frizzled receptors (FZD5/FZD8). Accordingly, miR‐100 inhibition blunts FSS‐ and TGFβ‐inducible Wnt signaling. Therefore, our results identify FSS‐responsive miRNAs in osteocytes, including one that integrates the mechanosensitive function of two essential signaling pathways in the osteoanabolic response of bone to mechanical load.
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Affiliation(s)
- Neha S Dole
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, California, USA
| | - Jihee Yoon
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, California, USA
| | - David A Monteiro
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, California, USA
| | - Jason Yang
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, California, USA
| | - Courtney M Mazur
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, California, USA
| | - Serra Kaya
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, California, USA
| | - Cassandra D Belair
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, California, USA.,Department of Urology, University of California, San Francisco, San Francisco, California, USA
| | - Tamara Alliston
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, California, USA.,Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, California, USA
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11
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Juhl OJ, Buettmann EG, Friedman MA, DeNapoli RC, Hoppock GA, Donahue HJ. Update on the effects of microgravity on the musculoskeletal system. NPJ Microgravity 2021; 7:28. [PMID: 34301942 PMCID: PMC8302614 DOI: 10.1038/s41526-021-00158-4] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 06/28/2021] [Indexed: 02/07/2023] Open
Abstract
With the reignited push for manned spaceflight and the development of companies focused on commercializing spaceflight, increased human ventures into space are inevitable. However, this venture would not be without risk. The lower gravitational force, known as microgravity, that would be experienced during spaceflight significantly disrupts many physiological systems. One of the most notably affected systems is the musculoskeletal system, where exposure to microgravity causes both bone and skeletal muscle loss, both of which have significant clinical implications. In this review, we focus on recent advancements in our understanding of how exposure to microgravity affects the musculoskeletal system. We will focus on the catabolic effects microgravity exposure has on both bone and skeletal muscle cells, as well as their respective progenitor stem cells. Additionally, we report on the mechanisms that underlie bone and muscle tissue loss resulting from exposure to microgravity and then discuss current countermeasures being evaluated. We reveal the gaps in the current knowledge and expound upon how current research is filling these gaps while also identifying new avenues of study as we continue to pursue manned spaceflight.
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Affiliation(s)
- Otto J Juhl
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, USA
| | - Evan G Buettmann
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, USA
| | - Michael A Friedman
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, USA
| | - Rachel C DeNapoli
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, USA
| | - Gabriel A Hoppock
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, USA
| | - Henry J Donahue
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, USA.
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12
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Jewlal E, Barr K, Laird DW, Willmore KE. Connexin 43 contributes to phenotypic robustness of the mouse skull. Dev Dyn 2021; 250:1810-1827. [PMID: 34091987 DOI: 10.1002/dvdy.381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 05/13/2021] [Accepted: 06/02/2021] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND We compared skull shape and variation among genetically modified mice that exhibit different levels of connexin43 (Cx43) channel function, to determine whether Cx43 contributes to craniofacial phenotypic robustness. Specifically, we used two heterozygous mutant mouse models (G60S/+ and I130T/+) that, when compared to their wildtype counterparts, have an ~80% and ~50% reduction in Cx43 function, respectively. RESULTS Both mutant strains showed significant differences in skull shape compared to wildtype littermates and while these differences were more severe in the G60S/+ mouse, shape differences were localized to similar regions of the skull in both mutants. However, increased skull shape variation was observed in G60S/+ mutants only. Additionally, covariation of skull structures was disrupted in the G60S/+ mutants only, indicating that while a 50% reduction in Cx43 function is sufficient to cause a shift in mean skull shape, the threshold for Cx43 function for disrupting craniofacial phenotypic robustness is lower. CONCLUSIONS Collectively, our results indicate Cx43 can contribute to phenotypic robustness of the skull through a nonlinear relationship between Cx43 gap junctional function and phenotypic outcomes.
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Affiliation(s)
- Elizabeth Jewlal
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
| | - Kevin Barr
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
| | - Dale W Laird
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada.,Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
| | - Katherine E Willmore
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada
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13
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Naqvi SM, Panadero Pérez JA, Kumar V, Verbruggen ASK, McNamara LM. A Novel 3D Osteoblast and Osteocyte Model Revealing Changes in Mineralization and Pro-osteoclastogenic Paracrine Signaling During Estrogen Deficiency. Front Bioeng Biotechnol 2020; 8:601. [PMID: 32656194 PMCID: PMC7326002 DOI: 10.3389/fbioe.2020.00601] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 05/18/2020] [Indexed: 11/13/2022] Open
Abstract
Recent in vitro studies have revealed that the mechanobiological responses of osteoblasts and osteocytes are fundamentally impaired during estrogen deficiency. However, these two-dimensional (2D) cell culture studies do not account for in vivo biophysical cues. Thus, the objectives of this study are to (1) develop a three-dimensional (3D) osteoblast and osteocyte model integrated into a bioreactor and (2) apply this model to investigate whether estrogen deficiency leads to changes in osteoblast to osteocyte transition, mechanosensation, mineralization, and paracrine signaling associated with bone resorption by osteoclasts. MC3T3-E1s were expanded in media supplemented with estrogen (17β-estradiol). These cells were encapsulated in gelatin-mtgase before culture in (1) continued estrogen (E) or (2) no further estrogen supplementation. Constructs were placed in gas permeable and water impermeable cell culture bags and maintained at 5% CO2 and 37°C. These bags were either mechanically stimulated in a custom hydrostatic pressure (HP) bioreactor or maintained under static conditions (control). We report that osteocyte differentiation, characterized by the presence of dendrites and staining for osteocyte marker dentin matrix acidic phosphoprotein 1 (DMP1), was significantly greater under estrogen withdrawal (EW) compared to under continuous estrogen treatment (day 21). Mineralization [bone sialoprotein (BSP), osteopontin (OPN), alkaline phosphatase (ALP), calcium] and gene expression associated with paracrine signaling for osteoclastogenesis [receptor activator of nuclear factor kappa-β ligand (RANKL)/osteoprotegerin OPG ratio] were significantly increased in estrogen deficient and mechanically stimulated cells. Interestingly, BSP and DMP-1 were also increased at day 1 and day 21, respectively, which play a role in regulation of biomineralization. Furthermore, the increase in pro-osteoclastogenic signaling may be explained by altered mechanoresponsiveness of osteoblasts or osteocytes during EW. These findings highlight the impact of estrogen deficiency on bone cell function and provide a novel in vitro model to investigate the mechanisms underpinning changes in bone cells after estrogen deficiency.
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Affiliation(s)
- Syeda Masooma Naqvi
- Mechanobiology and Medical Device Research Group, Department of Biomedical Engineering, College of Engineering and Informatics, National University of Ireland Galway, Galway, Ireland
| | - Juan Alberto Panadero Pérez
- Mechanobiology and Medical Device Research Group, Department of Biomedical Engineering, College of Engineering and Informatics, National University of Ireland Galway, Galway, Ireland
| | - Vatsal Kumar
- Mechanobiology and Medical Device Research Group, Department of Biomedical Engineering, College of Engineering and Informatics, National University of Ireland Galway, Galway, Ireland
| | - Anneke S K Verbruggen
- Mechanobiology and Medical Device Research Group, Department of Biomedical Engineering, College of Engineering and Informatics, National University of Ireland Galway, Galway, Ireland
| | - Laoise M McNamara
- Mechanobiology and Medical Device Research Group, Department of Biomedical Engineering, College of Engineering and Informatics, National University of Ireland Galway, Galway, Ireland
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14
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Qin L, Liu W, Cao H, Xiao G. Molecular mechanosensors in osteocytes. Bone Res 2020; 8:23. [PMID: 32550039 PMCID: PMC7280204 DOI: 10.1038/s41413-020-0099-y] [Citation(s) in RCA: 186] [Impact Index Per Article: 46.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 04/07/2020] [Accepted: 04/17/2020] [Indexed: 12/11/2022] Open
Abstract
Osteocytes, the most abundant and long-lived cells in bone, are the master regulators of bone remodeling. In addition to their functions in endocrine regulation and calcium and phosphate metabolism, osteocytes are the major responsive cells in force adaptation due to mechanical stimulation. Mechanically induced bone formation and adaptation, disuse-induced bone loss and skeletal fragility are mediated by osteocytes, which sense local mechanical cues and respond to these cues in both direct and indirect ways. The mechanotransduction process in osteocytes is a complex but exquisite regulatory process between cells and their environment, between neighboring cells, and between different functional mechanosensors in individual cells. Over the past two decades, great efforts have focused on finding various mechanosensors in osteocytes that transmit extracellular mechanical signals into osteocytes and regulate responsive gene expression. The osteocyte cytoskeleton, dendritic processes, Integrin-based focal adhesions, connexin-based intercellular junctions, primary cilium, ion channels, and extracellular matrix are the major mechanosensors in osteocytes reported so far with evidence from both in vitro and in vitro studies. This review aims to give a systematic introduction to osteocyte mechanobiology, provide details of osteocyte mechanosensors, and discuss the roles of osteocyte mechanosensitive signaling pathways in the regulation of bone homeostasis.
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Affiliation(s)
- Lei Qin
- Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, and School of Medicine, Southern University of Science and Technology, Shenzhen, 518055 China
| | - Wen Liu
- Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, and School of Medicine, Southern University of Science and Technology, Shenzhen, 518055 China
| | - Huiling Cao
- Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, and School of Medicine, Southern University of Science and Technology, Shenzhen, 518055 China
| | - Guozhi Xiao
- Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, and School of Medicine, Southern University of Science and Technology, Shenzhen, 518055 China
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15
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Simfia I, Schiavi J, McNamara LM. Alterations in osteocyte mediated osteoclastogenesis during estrogen deficiency and under ROCK-II inhibition: An in vitro study using a novel postmenopausal multicellular niche model. Exp Cell Res 2020; 392:112005. [PMID: 32330507 DOI: 10.1016/j.yexcr.2020.112005] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 04/02/2020] [Accepted: 04/09/2020] [Indexed: 01/03/2023]
Abstract
This study sought to derive an enhanced understanding of the complex intracellular interactions that drive bone loss in postmenopausal osteoporosis. We applied an in-vitro multicellular niche to recapitulate cell-cell signalling between osteocytes, osteoblasts and osteoclasts to investigate (1) how estrogen-deficient and mechanically loaded osteocytes regulate osteoclastogenesis and (2) whether ROCK-II inhibition affects these mechanobiological responses. We report that mechanically stimulated and estrogen-deficient osteocytes upregulated RANKL/OPG and M-CSF gene expression, when compared to those treated with 10 nM estradiol. Osteoclast precursors (RAW 264.7) cultured within this niche underwent significant reduction in osteoclastogenic gene expression (CTSK), and there was an increasing trend in the area covered by TRAP+ osteoclasts (24% vs. 19.4%, p = 0.06). Most interestingly, upon treatment with the ROCK-II inhibitor, RANKL/OPG and M-CSF gene expression by estrogen-deficient osteocytes were downregulated. Yet, this inhibition of the pro-osteoclastogenic factors by osteocytes did not ultimately reduce the differentiation of osteoclast precursors. Indeed, TRAP and CTSK gene expressions in osteoclast precursors were upregulated, and there was an increased trend for osteoclast area (30.4% vs. 24%, p = 0.07), which may have been influenced by static osteoblasts (MC3T3-E1) that were included in the niche. We conclude that ROCK-II inhibition can attenuate bone loss driven by osteocytes during estrogen deficiency.
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Affiliation(s)
- Irene Simfia
- Mechanobiology and Medical Device Research Group, Biomechanics Research Centre, Biomedical Engineering, College of Engineering and Informatics, National University of Ireland Galway, Galway, Ireland
| | - Jessica Schiavi
- Mechanobiology and Medical Device Research Group, Biomechanics Research Centre, Biomedical Engineering, College of Engineering and Informatics, National University of Ireland Galway, Galway, Ireland
| | - Laoise M McNamara
- Mechanobiology and Medical Device Research Group, Biomechanics Research Centre, Biomedical Engineering, College of Engineering and Informatics, National University of Ireland Galway, Galway, Ireland.
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Hardy E, Fernandez-Patron C. Destroy to Rebuild: The Connection Between Bone Tissue Remodeling and Matrix Metalloproteinases. Front Physiol 2020; 11:47. [PMID: 32116759 PMCID: PMC7013034 DOI: 10.3389/fphys.2020.00047] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 01/21/2020] [Indexed: 12/11/2022] Open
Abstract
Bone is a dynamic organ that undergoes constant remodeling, an energetically costly process by which old bone is replaced and localized bone defects are repaired to renew the skeleton over time, thereby maintaining skeletal health. This review provides a general overview of bone’s main players (bone lining cells, osteocytes, osteoclasts, reversal cells, and osteoblasts) that participate in bone remodeling. Placing emphasis on the family of extracellular matrix metalloproteinases (MMPs), we describe how: (i) Convergence of multiple protease families (including MMPs and cysteine proteinases) ensures complexity and robustness of the bone remodeling process, (ii) Enzymatic activity of MMPs affects bone physiology at the molecular and cellular levels and (iii) Either overexpression or deficiency/insufficiency of individual MMPs impairs healthy bone remodeling and systemic metabolism. Today, it is generally accepted that proteolytic activity is required for the degradation of bone tissue in osteoarthritis and osteoporosis. However, it is increasingly evident that inactivating mutations in MMP genes can also lead to bone pathology including osteolysis and metabolic abnormalities such as delayed growth. We argue that there remains a need to rethink the role played by proteases in bone physiology and pathology.
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Affiliation(s)
| | - Carlos Fernandez-Patron
- Department of Biochemistry, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, AB, Canada
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Alfieri R, Vassalli M, Viti F. Flow-induced mechanotransduction in skeletal cells. Biophys Rev 2019; 11:729-743. [PMID: 31529361 DOI: 10.1007/s12551-019-00596-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 09/03/2019] [Indexed: 12/15/2022] Open
Abstract
Human body is subject to many and variegated mechanical stimuli, actuated in different ranges of force, frequency, and duration. The process through which cells "feel" forces and convert them into biochemical cascades is called mechanotransduction. In this review, the effects of fluid shear stress on bone cells will be presented. After an introduction to present the major players in bone system, we describe the mechanoreceptors in bone tissue that can feel and process fluid flow. In the second part of the review, we present an overview of the biological processes and biochemical cascades initiated by fluid shear stress in bone cells.
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Affiliation(s)
- Roberta Alfieri
- Institute of Molecular Genetics "Luigi Luca Cavalli-Sforza" - National Research Council (IGM-CNR), Via Abbiategrasso, 207, 27100, Pavia, Italy
| | - Massimo Vassalli
- Institute of Biophysics - National Research Council (IBF-CNR), Via De Marini, 6, 16149, Genoa, Italy
| | - Federica Viti
- Institute of Biophysics - National Research Council (IBF-CNR), Via De Marini, 6, 16149, Genoa, Italy.
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18
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Estrogen deficiency impairs integrin α vβ 3-mediated mechanosensation by osteocytes and alters osteoclastogenic paracrine signalling. Sci Rep 2019; 9:4654. [PMID: 30874595 PMCID: PMC6420496 DOI: 10.1038/s41598-019-41095-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 02/26/2019] [Indexed: 02/06/2023] Open
Abstract
The integrin αvβ3 has been shown to play an important role in osteocyte mechanotransduction. It has been reported that there are fewer β3 integrin-containing cells in osteoporotic bone cells. Osteocytes cultured in vitro under estrogen deficient conditions demonstrate altered mechanotransduction. However, it is unknown whether the altered mechanotransduction in estrogen deficient osteocytes is directly associated with defective αvβ3 expression or signalling. The objective of this study is to investigate the role of estrogen deficiency for regulating MLO-Y4 cell morphology, αvβ3 expression, focal adhesion formation and mechanotransduction by osteocytes. Here, we report that estrogen withdrawal leads to a smaller focal adhesion area and reduced αvβ3 localisation at focal adhesion sites, resulting in an increased Rankl/Opg ratio and defective Cox-2 responses to oscillatory fluid flow. Interestingly, αvβ3 antagonism had a similar effect on focal adhesion assembly, Rankl/Opg ratio, and Cox-2 responses to oscillatory fluid flow. Taken together, our results provide the first evidence for a relationship between estrogen withdrawal and defective αvβ3-mediated signalling. Specifically, this study implicates estrogen withdrawal as a putative mechanism responsible for altered αvβ3 expression and resultant changes in downstream signalling in osteocytes during post-menopausal osteoporosis, which might provide an important, but previously unidentified, contribution to the bone loss cascade.
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19
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Takemura Y, Moriyama Y, Ayukawa Y, Kurata K, Rakhmatia YD, Koyano K. Mechanical loading induced osteocyte apoptosis and connexin 43 expression in three-dimensional cell culture and dental implant model. J Biomed Mater Res A 2019; 107:815-827. [DOI: 10.1002/jbm.a.36597] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 12/06/2018] [Accepted: 12/18/2018] [Indexed: 11/09/2022]
Affiliation(s)
- Yoko Takemura
- Section of Implant and Rehabilitative Dentistry, Division of Oral Rehabilitation, Faculty of Dental Science; Kyushu University; Fukuoka Japan
| | - Yasuko Moriyama
- Section of Implant and Rehabilitative Dentistry, Division of Oral Rehabilitation, Faculty of Dental Science; Kyushu University; Fukuoka Japan
| | - Yasunori Ayukawa
- Section of Implant and Rehabilitative Dentistry, Division of Oral Rehabilitation, Faculty of Dental Science; Kyushu University; Fukuoka Japan
| | - Kosaku Kurata
- Department of Mechanical Engineering, Faculty of Engineering; Kyushu University; Fukuoka Japan
| | - Yunia D. Rakhmatia
- Section of Implant and Rehabilitative Dentistry, Division of Oral Rehabilitation, Faculty of Dental Science; Kyushu University; Fukuoka Japan
| | - Kiyoshi Koyano
- Section of Implant and Rehabilitative Dentistry, Division of Oral Rehabilitation, Faculty of Dental Science; Kyushu University; Fukuoka Japan
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20
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Brézulier D, Pellen-Mussi P, Sorel O, Jeanne S. [Bone mechanobiology, an emerging field: a review]. Orthod Fr 2018; 89:343-353. [PMID: 30565553 DOI: 10.1051/orthodfr/2018034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 10/15/2018] [Indexed: 11/14/2022]
Abstract
INTRODUCTION Mechanobiology, at the interface between biology and biophysics, studies the impact of mechanical forces on tissues, cells and biomolecules. The application of orthodontic forces, followed by induced tooth displacement, is a striking example of its clinical application. OBJECTIVE The purpose of this article was to compile a review of the literature on the subject of mechanobiology; from its detection at bone level to the presentation of stimulated intracellular pathways. MATERIALS AND METHODS The literature search was conducted on the Pubmed database in April 2018, with associations of the terms "mechanobiology", "orthodontics", "cell culture", "physiopathology". RESULTS Three major areas of research were selected: highlighting of the phenomenon and its application in the field of bone biology; the cellular effectors of mechanobiology and its clinical applications. The use of mechanobiology in dentofacial orthopedics opens up a new field of reflection for clinicians regarding future advances in orthodontics.
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Affiliation(s)
- Damien Brézulier
- Université de Rennes, ISCR, CNRS - UMR 6226, Pole Odontologie, 35000 Rennes, France
| | - Pascal Pellen-Mussi
- Université de Rennes, ISCR, CNRS - UMR 6226, Pole Odontologie, 35000 Rennes, France
| | - Olivier Sorel
- Université de Rennes, ISCR, CNRS - UMR 6226, Pole Odontologie, 35000 Rennes, France
| | - Sylvie Jeanne
- Université de Rennes, ISCR, CNRS - UMR 6226, Pole Odontologie, 35000 Rennes, France
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21
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Combined Fluid Shear Stress and Melatonin Enhances the ERK/Akt/mTOR Signal in Cilia-Less MC3T3-E1 Preosteoblast Cells. Int J Mol Sci 2018; 19:ijms19102929. [PMID: 30261648 PMCID: PMC6213863 DOI: 10.3390/ijms19102929] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 09/22/2018] [Accepted: 09/23/2018] [Indexed: 01/05/2023] Open
Abstract
We investigated whether combined fluid shear stress (FSS) and melatonin stimulated signal transduction in cilia-less MC3T3-E1 preosteoblast cells. MC3T3-E1 cells were treated with chloral hydrate or nocodazole, and mechanotransduction sensor primary cilia were removed. p-extracellular signal–regulated kinase (ERK) and p-Akt with/without melatonin increased with nocodazole treatment and decreased with chloral hydrate treatment, whereas p-ERK and p-Akt in FSS with/without melatonin increased in cilia-less groups compared to cilia groups. Furthermore, p-mammalian target of rapamycin (mTOR) with FSS-plus melatonin increased in cilia-less groups compared to only melatonin treatments in cilia groups. Expressions of Bcl-2, Cu/Zn-superoxide dismutase (SOD), and catalase proteins were higher in FSS with/without melatonin with cilia-less groups than only melatonin treatments in cilia groups. Bax protein expression was high in FSS-plus melatonin with chloral hydrate treatment. In chloral hydrate treatment with/without FSS, expressions of Cu/Zn-SOD, Mn-SOD, and catalase proteins were high compared to only-melatonin treatments. In nocodazole treatment, Mn-SOD protein expression without FSS was high, and catalase protein level with FSS was low, compared to only melatonin treatments. These data show that the combination with FSS and melatonin enhances ERK/Akt/mTOR signal in cilia-less MC3T3-E1, and the enhanced signaling in cilia-less MC3T3-E1 osteoblast cells may activate the anabolic effect for the preservation of cell structure and function.
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22
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Abstract
Connexons form the basis of hemichannels and gap junctions. They are composed of six tetraspan proteins called connexins. Connexons can function as individual hemichannels, releasing cytosolic factors (such as ATP) into the pericellular environment. Alternatively, two hemichannel connexons from neighbouring cells can come together to form gap junctions, membrane-spanning channels that facilitate cell-cell communication by enabling signalling molecules of approximately 1 kDa to pass from one cell to an adjacent cell. Connexins are expressed in joint tissues including bone, cartilage, skeletal muscle and the synovium. Indicative of their importance as gap junction components, connexins are also known as gap junction proteins, but individual connexin proteins are gaining recognition for their channel-independent roles, which include scaffolding and signalling functions. Considerable evidence indicates that connexons contribute to the function of bone and muscle, but less is known about the function of connexons in other joint tissues. However, the implication that connexins and gap junctional channels might be involved in joint disease, including age-related bone loss, osteoarthritis and rheumatoid arthritis, emphasizes the need for further research into these areas and highlights the therapeutic potential of connexins.
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Affiliation(s)
- Henry J Donahue
- Department of Biomedical Engineering, Virginia Commonwealth University, 601 West Main Street, Richmond, Virginia 23284, USA
| | - Roy W Qu
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California at Davis, One Shields Avenue, Davis, California 95616, USA
| | - Damian C Genetos
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California at Davis, One Shields Avenue, Davis, California 95616, USA
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23
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Dobrosak C, Gooi JH. Increased sphingosine-1-phosphate production in response to osteocyte mechanotransduction. Bone Rep 2017; 7:114-120. [PMID: 29085869 PMCID: PMC5651498 DOI: 10.1016/j.bonr.2017.10.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 09/06/2017] [Accepted: 10/15/2017] [Indexed: 01/01/2023] Open
Abstract
Over the past few years interest has greatly increased in how the lipid mediator sphingosine-1-phosphate (S1P) influences bone homeostasis. Recent work has postulated multiple effects of S1P on osteoblasts and osteoclasts. Based on these findings, S1P has been proposed as a potential osteoporosis treatment. However, to date, there has been only a single study investigating S1P signalling in the cells that co-ordinate bone metabolism: osteocytes. This study aimed to elucidate the role of S1P signalling in osteocyte mechanotransduction. Utilising 3D cell culture we established the expression profile of all genes related to the S1P signalling system in the Ocy454 osteocyte cell line. Exposure to mechanical loading resulted in a downregulation in Sost, Spns2, the S1P transporter, Sgpl1 and Sgppl1 the enzymes responsible for degradation and dephosphorylation of S1P. These findings, in conjunction with fluid-flow induced upregulation of Sphk1, the kinase responsible for phosphorylation of sphingosine, suggest that mechanical stimulation of osteocytes leads to an increase in intracellular S1P. This was confirmed with mechanical loading of Ocy454 cells rapidly increasing S1P production in conditioned media and protein lysates. These findings strongly suggest an important role for S1P in the response to mechanical loading of bone. Osteocytes form a cellular network throughout bone ideally suited for sensing the needs of the skeleton and responding to them. Over the past few years interest has greatly increased in how S1P influences bone homeostasis. Exposure to mechanical loading significantly modifies osteocyte S1P signalling. This suggests an important role for S1P production in the response to mechanical loading of bone.
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Affiliation(s)
- Cale Dobrosak
- Department of Medicine, St. Vincent's Hospital Melbourne, University of Melbourne, Melbourne, VIC 3065, Australia
| | - Jonathan H Gooi
- Department of Medicine, St. Vincent's Hospital Melbourne, University of Melbourne, Melbourne, VIC 3065, Australia
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24
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Shah KM, Orton P, Mani N, Wilkinson JM, Gartland A. Osteocyte physiology and response to fluid shear stress are impaired following exposure to cobalt and chromium: Implications for bone health following joint replacement. J Orthop Res 2017; 35:1716-1723. [PMID: 27673573 PMCID: PMC5603770 DOI: 10.1002/jor.23449] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 09/23/2016] [Indexed: 02/04/2023]
Abstract
The effects of metal ion exposure on osteocytes, the most abundant cell type in bone and responsible for coordinating bone remodeling, remain unclear. However, several studies have previously shown that exposure to cobalt (Co2+ ) and chromium (Cr3+ ), at concentrations equivalent to those found clinically, affect osteoblast and osteoclast survival and function. In this study, we tested the hypothesis that metal ions would similarly impair the normal physiology of osteocytes. The survival, dendritic morphology, and response to fluid shear stress of the mature osteocyte-like cell-line MLO-Y4 following exposure to clinically relevant concentrations and combinations of Co and Cr ions were measured in 2D-culture. Exposure of MLO-Y4 cells to metal ions reduced cell number, increased dendrites per cell and increased dendrite length. We found that combinations of metal ions had a greater effect than the individual ions alone, and that Co2+ had a predominate effect on changes to cell numbers and dendrites. Combined metal ion exposure blunted the responses of the MLO-Y4 cells to fluid shear stress, including reducing the intracellular calcium responses and modulation of genes for the osteocyte markers Cx43 and Gp38, and the signaling molecules RANKL and Dkk-1. Finally, we demonstrated that in the late osteoblasts/early osteocytes cell line MLO-A5 that Co2+ exposure had no effect on mineralization, but Cr3+ treatment inhibited mineralization in a dose-dependent manner, without affecting cell viability. Taken together, these data indicate that metal exposure can directly affect osteocyte physiology, with potential implications for bone health including osseointegration of cementless components, and periprosthetic bone remodeling. © 2016 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 35:1716-1723, 2017.
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Affiliation(s)
- Karan M. Shah
- Department of Oncology and MetabolismThe University of SheffieldBeech Hill RdSheffield S10 2RXUnited Kingdom
| | - Peter Orton
- Department of Oncology and MetabolismThe University of SheffieldBeech Hill RdSheffield S10 2RXUnited Kingdom
| | - Nick Mani
- Department of Oncology and MetabolismThe University of SheffieldBeech Hill RdSheffield S10 2RXUnited Kingdom
| | - Jeremy Mark Wilkinson
- Department of Oncology and MetabolismThe University of SheffieldBeech Hill RdSheffield S10 2RXUnited Kingdom
| | - Alison Gartland
- Department of Oncology and MetabolismThe University of SheffieldBeech Hill RdSheffield S10 2RXUnited Kingdom
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25
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Chen G, Xu R, Zhang C, Lv Y. Responses of MSCs to 3D Scaffold Matrix Mechanical Properties under Oscillatory Perfusion Culture. ACS APPLIED MATERIALS & INTERFACES 2017; 9:1207-1218. [PMID: 28006094 DOI: 10.1021/acsami.6b10745] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Both fluid shear stress and matrix stiffness are implicated in bone metabolism and functional adaptation, but the synergistic action of these mechanical cues on the biological behaviors of mesenchymal stem cells (MSCs) is still not well-known. In the present work, a homemade oscillatory flow device was applied to investigate the effects of matrix stiffness on MSCs survival, distribution, and osteogenic differentiation in three-dimensional (3D) conditions. Furthermore, the flow field and cell growth in this bioreactor were theoretically simulated. The results demonstrated that oscillatory shear stress significantly increased the viability and distribution uniformity of MSCs throughout the scaffold after culture for 3 weeks. Compared to static culture, oscillatory shear stress could promote the collagen secretion, mineral deposits, and osteogenic differentiation of MSCs. The findings obtained from this work indicate that the oscillatory perfusion not only provides a higher survival rate and a more uniform distribution of cells but also facilitates osteogenic differentiation of MSCs. Oscillating perfusion bioreactor culture of MSCs in 3D scaffold with optimal matrix stiffness could offer an easy-to-use but efficient bioreactor for bone tissue engineering.
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Affiliation(s)
| | - Rui Xu
- School of Environmental Engineering, Wuhan Textile University , Wuhan 430073, PR China
| | - Chang Zhang
- School of Environmental Engineering, Wuhan Textile University , Wuhan 430073, PR China
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26
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Suswillo RFL, Javaheri B, Rawlinson SCF, Dowthwaite GP, Lanyon LE, Pitsillides AA. Strain uses gap junctions to reverse stimulation of osteoblast proliferation by osteocytes. Cell Biochem Funct 2017; 35:56-65. [PMID: 28083967 PMCID: PMC5299599 DOI: 10.1002/cbf.3245] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 11/01/2016] [Accepted: 11/29/2016] [Indexed: 12/20/2022]
Abstract
Identifying mechanisms by which cells of the osteoblastic lineage communicate in vivo is complicated by the mineralised matrix that encases osteocytes, and thus, vital mechanoadaptive processes used to achieve load-bearing integrity remain unresolved. We have used the coculture of immunomagnetically purified osteocytes and primary osteoblasts from both embryonic chick long bone and calvariae to examine these mechanisms. We exploited the fact that purified osteocytes are postmitotic to examine both their effect on proliferation of primary osteoblasts and the role of gap junctions in such communication. We found that chick long bone osteocytes significantly increased basal proliferation of primary osteoblasts derived from an identical source (tibiotarsi). Using a gap junction inhibitor, 18β-glycyrrhetinic acid, we also demonstrated that this osteocyte-related increase in osteoblast proliferation was not reliant on functional gap junctions. In contrast, osteocytes purified from calvarial bone failed to modify basal proliferation of primary osteoblast, but long bone osteocytes preserved their proproliferative action upon calvarial-derived primary osteoblasts. We also showed that coincubated purified osteocytes exerted a marked inhibitory action on mechanical strain-related increases in proliferation of primary osteoblasts and that this action was abrogated in the presence of a gap junction inhibitor. These data reveal regulatory differences between purified osteocytes derived from functionally distinct bones and provide evidence for 2 mechanisms by which purified osteocytes communicate with primary osteoblasts to coordinate their activity.
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Affiliation(s)
| | - Behzad Javaheri
- Comparative Biomedical Sciences, Royal Veterinary College, London, UK
| | - Simon C F Rawlinson
- Institute of Dentistry, Barts & The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Gary P Dowthwaite
- Comparative Biomedical Sciences, Royal Veterinary College, London, UK
| | - Lance E Lanyon
- School of Veterinary Sciences, University of Bristol, Bristol, UK
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Zhang JN, Zhao Y, Liu C, Han ES, Yu X, Lidington D, Bolz SS, You L. The role of the sphingosine-1-phosphate signaling pathway in osteocyte mechanotransduction. Bone 2015; 79:71-8. [PMID: 25988659 DOI: 10.1016/j.bone.2015.05.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Revised: 04/16/2015] [Accepted: 05/12/2015] [Indexed: 11/17/2022]
Abstract
Osteocytes are proposed to be the mechanosensory cells that translate mechanical loading into biochemical signals during the process of bone adaptation. The lipid mediator sphingosine-1-phosphate (S1P) has been reported to play a role in the mechanotransduction process of blood vessels and also in the dynamic control of bone mineral homeostasis. Nevertheless, the potential role of S1P in bone mechanotransduction has yet to be elucidated. In this study, we hypothesized that a S1P cascade is involved in the activation of osteocytes in response to loading-induced oscillatory fluid flow (OFF) in bone. MLO-Y4 osteocyte-like cells express the necessary components of a functional S1P cascade. To examine the involvement of S1P signaling in osteocyte mechanotransduction, we applied OFF (1 Pa, 1 Hz) to osteocyte-like MLO-Y4 cells under conditions where the S1P signaling pathway was modulated. We found that decreased endogenous S1P levels significantly suppressed the OFF-induced intracellular calcium response. Addition of extracellular S1P to MLO-Y4 cells enhanced the synthesis and release of prostaglandin E2 (PGE2) under static cells and amplified OFF-induced PGE2 release. The stimulatory effect of OFF on the gene expression levels of osteoprotegerin (OPG) and receptor activator for nuclear factor κB ligand (RANKL) was S1P dependent. Furthermore, the S1P2 receptor subtype was shown to be involved in OFF-induced PGE2 synthesis and release, as well as down-regulation of RANKL/OPG gene expression ratio. In summary, our data suggest that S1P cascade is involved in OFF-induced mechanotransduction in MLO-Y4 cells and that extracellular S1P exerts its effect partly through S1P2 receptors.
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Affiliation(s)
- Jia-Ning Zhang
- Institute of Biomaterials & Biomedical Engineering, University of Toronto, ON, Canada
| | - Yan Zhao
- Institute of Biomaterials & Biomedical Engineering, University of Toronto, ON, Canada
| | - Chao Liu
- Institute of Biomaterials & Biomedical Engineering, University of Toronto, ON, Canada
| | - Elizabeth S Han
- Institute of Biomaterials & Biomedical Engineering, University of Toronto, ON, Canada
| | - Xue Yu
- Division of Engineering Science, University of Toronto, ON, Canada
| | | | | | - Lidan You
- Institute of Biomaterials & Biomedical Engineering, University of Toronto, ON, Canada; Department of Mechanical and Industrial Engineering, University of Toronto, ON, Canada.
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28
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Inhibition of T-Type Voltage Sensitive Calcium Channel Reduces Load-Induced OA in Mice and Suppresses the Catabolic Effect of Bone Mechanical Stress on Chondrocytes. PLoS One 2015; 10:e0127290. [PMID: 26011709 PMCID: PMC4444170 DOI: 10.1371/journal.pone.0127290] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 04/13/2015] [Indexed: 01/23/2023] Open
Abstract
Voltage-sensitive calcium channels (VSCC) regulate cellular calcium influx, one of the earliest responses to mechanical stimulation in osteoblasts. Here, we postulate that T-type VSCCs play an essential role in bone mechanical response to load and participate in events leading to the pathology of load-induced OA. Repetitive mechanical insult was used to induce OA in Cav3.2 T-VSCC null and wild-type control mouse knees. Osteoblasts (MC3T3-E1) and chondrocytes were treated with a selective T-VSCC inhibitor and subjected to fluid shear stress to determine how blocking of T-VSCCs alters the expression profile of each cell type upon mechanical stimulation. Conditioned-media (CM) obtained from static and sheared MC3T3-E1 was used to assess the effect of osteoblast-derived factors on the chondrocyte phenotype. T-VSCC null knees exhibited significantly lower focal articular cartilage damage than age-matched controls. In vitro inhibition of T-VSCC significantly reduced the expression of both early and late mechanoresponsive genes in osteoblasts but had no effect on gene expression in chondrocytes. Furthermore, treatment of chondrocytes with CM obtained from sheared osteoblasts induced expression of markers of hypertrophy in chondrocytes and this was nearly abolished when osteoblasts were pre-treated with the T-VSCC-specific inhibitor. These results indicate that T-VSCC plays a role in signaling events associated with induction of OA and is essential to the release of osteoblast-derived factors that promote an early OA phenotype in chondrocytes. Further, these findings suggest that local inhibition of T-VSCC may serve as a therapy for blocking load-induced bone formation that results in cartilage degeneration.
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29
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Abstract
Bone adaptation to changes in mechanical stimuli occurs by adjusting bone formation and resorption by osteoblasts and osteoclasts, to maintain optimal bone mass. Osteocytes coordinate the actions of these cells on the bone surface by sensing mechanical forces and producing cytokines that increase or prevent osteoblast and osteoclast differentiation and function. Channels formed by connexins (Cxs) and, in particular, connexin 43 (Cx43) in osteoblasts and osteocytes are central part of this mechanism to control bone mass. Cx43 hemichannels are opened by fluid flow and mediate the anti-apoptotic effect of mechanical stimulation in vitro, suggesting that Cx43 participates in mechanotransduction. However, mice lacking Cx43 in osteoblasts and/or osteocytes show an increased anabolic response to loading and decreased catabolic response to unloading. This evidence suggests that Cx43 channels expressed in osteoblastic cells are not required for the response to mechanical stimulation, but mediate the consequence of lack thereof. The molecular basis of these unexpected responses to mechanical stimulation is currently under investigation.
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Affiliation(s)
- Lilian I Plotkin
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, and Roudebush Veterans Administration Medical Center, 635 Barnhill Drive, MS-5035, Indianapolis, IN, 46202, USA,
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Bouet G, Marchat D, Cruel M, Malaval L, Vico L. In VitroThree-Dimensional Bone Tissue Models: From Cells to Controlled and Dynamic Environment. TISSUE ENGINEERING PART B-REVIEWS 2015; 21:133-56. [DOI: 10.1089/ten.teb.2013.0682] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Guenaelle Bouet
- Laboratoire de Biologie du Tissu Osseux, Institut National de la Santé et de la Recherche Médicale—U1059, Université de Lyon—Université Jean Monnet, Saint-Etienne, France
| | - David Marchat
- Center for Biomedical and Healthcare Engineering, Ecole Nationale Supérieure des Mines, CIS-EMSE, CNRS:UMR 5307, Saint-Etienne, France
| | - Magali Cruel
- University of Lyon, LTDS, UMR CNRS 5513, Ecole Centrale de Lyon, Ecully, France
| | - Luc Malaval
- Laboratoire de Biologie du Tissu Osseux, Institut National de la Santé et de la Recherche Médicale—U1059, Université de Lyon—Université Jean Monnet, Saint-Etienne, France
| | - Laurence Vico
- Laboratoire de Biologie du Tissu Osseux, Institut National de la Santé et de la Recherche Médicale—U1059, Université de Lyon—Université Jean Monnet, Saint-Etienne, France
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31
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Bone cell mechanosensation of fluid flow stimulation: a fluid–structure interaction model characterising the role integrin attachments and primary cilia. Biomech Model Mechanobiol 2014; 14:703-18. [DOI: 10.1007/s10237-014-0631-3] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Accepted: 11/05/2014] [Indexed: 11/27/2022]
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32
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Uzer G, Pongkitwitoon S, Ian C, Thompson WR, Rubin J, Chan ME, Judex S. Gap junctional communication in osteocytes is amplified by low intensity vibrations in vitro. PLoS One 2014; 9:e90840. [PMID: 24614887 PMCID: PMC3948700 DOI: 10.1371/journal.pone.0090840] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 02/05/2014] [Indexed: 11/21/2022] Open
Abstract
The physical mechanism by which cells sense high-frequency mechanical signals of small magnitude is unknown. During exposure to vibrations, cell populations within a bone are subjected not only to acceleratory motions but also to fluid shear as a result of fluid-cell interactions. We explored displacements of the cell nucleus during exposure to vibrations with a finite element (FE) model and tested in vitro whether vibrations can affect osteocyte communication independent of fluid shear. Osteocyte like MLO-Y4 cells were subjected to vibrations at acceleration magnitudes of 0.15 g and 1 g and frequencies of 30 Hz and 100 Hz. Gap junctional intracellular communication (GJIC) in response to these four individual vibration regimes was investigated. The FE model demonstrated that vibration induced dynamic accelerations caused larger relative nuclear displacement than fluid shear. Across the four regimes, vibrations significantly increased GJIC between osteocytes by 25%. Enhanced GJIC was independent of vibration induced fluid shear; there were no differences in GJIC between the four different vibration regimes even though differences in fluid shear generated by the four regimes varied 23-fold. Vibration induced increases in GJIC were not associated with altered connexin 43 (Cx43) mRNA or protein levels, but were dependent on Akt activation. Combined, the in silico and in vitro experiments suggest that externally applied vibrations caused nuclear motions and that large differences in fluid shear did not influence nuclear motion (<1%) or GJIC, perhaps indicating that vibration induced nuclear motions may directly increase GJIC. Whether the increase in GJIC is instrumental in modulating anabolic and anti-catabolic processes associated with the application of vibrations remains to be determined.
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Affiliation(s)
- Gunes Uzer
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York, United States of America
- Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Suphannee Pongkitwitoon
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York, United States of America
| | - Cheng Ian
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York, United States of America
| | - William R. Thompson
- Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Janet Rubin
- Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Meilin E. Chan
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York, United States of America
| | - Stefan Judex
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York, United States of America
- * E-mail:
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Knapik DM, Perera P, Nam J, Blazek AD, Rath B, Leblebicioglu B, Das H, Wu LC, Hewett TE, Agarwal SK, Robling AG, Flanigan DC, Lee BS, Agarwal S. Mechanosignaling in bone health, trauma and inflammation. Antioxid Redox Signal 2014; 20:970-85. [PMID: 23815527 PMCID: PMC3924811 DOI: 10.1089/ars.2013.5467] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
SIGNIFICANCE Mechanosignaling is vital for maintaining the structural integrity of bone under physiologic conditions. These signals activate and suppress multiple signaling cascades regulating bone formation and resorption. Understanding these pathways is of prime importance to exploit their therapeutic potential in disorders associated with bone loss due to disuse, trauma, or disruption of homeostatic mechanisms. RECENT ADVANCES In the case of cells of the bone, an impressive amount of data has been generated that provides evidence of a complex mechanism by which mechanical signals can maintain or disrupt cellular homeostasis by driving transcriptional regulation of growth factors, matrix proteins and inflammatory mediators in health and inflammation. Mechanical signals act on cells in a magnitude dependent manner to induce bone deposition or resorption. During health, physiological levels of these signals are essential for maintaining bone strength and architecture, whereas during inflammation, similar signals can curb inflammation by suppressing the nuclear factor kappa B (NF-κB) signaling cascade, while upregulating matrix synthesis via mothers against decapentaplegic homolog and/or Wnt signaling cascades. Contrarily, excessive mechanical forces can induce inflammation via activation of the NF-κB signaling cascade. CRITICAL ISSUES Given the osteogenic potential of mechanical signals, it is imperative to exploit their therapeutic efficacy for the treatment of bone disorders. Here we review select signaling pathways and mediators stimulated by mechanical signals to modulate the strength and integrity of the bone. FUTURE DIRECTIONS Understanding the mechanisms of mechanotransduction and its effects on bone lay the groundwork for development of nonpharmacologic mechanostimulatory approaches for osteodegenerative diseases and optimal bone health.
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Affiliation(s)
- Derrick M Knapik
- 1 Department of Orthopaedic Surgery, The Ohio State University College of Medicine , Columbus, Ohio
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34
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Lloyd SA, Loiselle AE, Zhang Y, Donahue HJ. Shifting paradigms on the role of connexin43 in the skeletal response to mechanical load. J Bone Miner Res 2014; 29:275-86. [PMID: 24588015 PMCID: PMC5949871 DOI: 10.1002/jbmr.2165] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Gap junctions (GJs) are membrane-spanning channels that allow for the movement of small molecules across cell membranes. Connexin43 (Cx43) is the predominant GJ protein in bone. In vitro studies suggest that gap junctional intercellular communication (GJIC) sensitizes bone cells to mechanical signals. Additionally, mechanical signals detected by osteocytes are communicated to osteoblasts via GJIC, and osteocytic Cx43 hemichannels release anabolic factors, such as PGE2 and ATP, in response to mechanical load. These findings and others have led to near consensus among researchers in the field that GJIC, hemichannels or connexins facilitate the anabolic response of bone to mechanical load and, in their absence, bone would be less sensitive to load. However, recent in vivo evidence suggests the opposite is true. Studies from our laboratory and others demonstrate that Cx43-deficient mice have an increased anabolic response to mechanical load and are protected against the catabolic effects of mechanical unloading. These developments suggest a paradigm shift in our understanding of connexins, GJIC, and mechanotransduction in bone. That is, inhibiting bone cell Cx43 expression or GJIC has a beneficial effect on bone's response to its mechanical environment, preserving bone during unloading and enhancing its formation during loading. Here, we review literature in support of this hypothesis and suggest a mechanism by which Cx43, through interaction with WNT/β-catenin signaling, moderates both arms of bone remodeling.
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Affiliation(s)
- Shane A Lloyd
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation; Penn State College of Medicine; Hershey PA USA
| | - Alayna E Loiselle
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation; Penn State College of Medicine; Hershey PA USA
| | - Yue Zhang
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation; Penn State College of Medicine; Hershey PA USA
| | - Henry J Donahue
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation; Penn State College of Medicine; Hershey PA USA
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35
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Vaughan TJ, Verbruggen SW, McNamara LM. Are all osteocytes equal? Multiscale modelling of cortical bone to characterise the mechanical stimulation of osteocytes. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2013; 29:1361-1372. [PMID: 23897701 DOI: 10.1002/cnm.2578] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 06/18/2013] [Accepted: 06/20/2013] [Indexed: 06/02/2023]
Abstract
Bone continuously adapts its internal structure to accommodate the functional demands of its mechanical environment. This process is orchestrated by a network of mechanosensitive osteocytes that respond to external mechanical signals and recruit osteoblasts and osteoclasts to alter bone mass to meet loading demands. Because of the irregular hierarchical microarchitecture of bone tissue, the precise mechanical stimuli experienced by osteocytes located in different regions of the tissue is not well-understood. The objective of this study is to characterise the local stimulus experienced by osteocytes distributed throughout the tissue structure. Our models predict that an inhomogeneous microstructural strain field contributes to osteocytes receiving vastly different stimuli at the cellular level, depending on their location within the microstructure. In particular, osteocytes located directly adjacent to micropores experienced strain amplifications in their processes of up to nine times the applied global strain. Furthermore, it was found that the principal orientation of lamellar regions was found to contribute significantly to the magnitude of the stimulus being received at the cellular level. These findings indicate that osteocytes are not equal in terms of the mechanical stimulus being received, and we propose that only a subset of osteocytes may be sufficiently stimulated to function as mechanoreceptors.
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Affiliation(s)
- Ted J Vaughan
- Biomechanics Research Centre (BMEC), Biomedical Engineering, College of Engineering and Informatics, National University of Ireland, Galway, Ireland; National Centre for Biomedical Engineering Sciences (NCBES), National University of Ireland, Galway, Ireland
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36
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Loiselle AE, Jiang JX, Donahue HJ. Gap junction and hemichannel functions in osteocytes. Bone 2013; 54:205-12. [PMID: 23069374 DOI: 10.1016/j.bone.2012.08.132] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 07/30/2012] [Accepted: 08/20/2012] [Indexed: 10/27/2022]
Abstract
Cell-to-cell and cell-to-matrix communication in bone cells mediated by gap junctions and hemichannels, respectively, maintains bone homeostasis. Gap junctional communication between cells permits the passage of small molecules including calcium and cyclic AMP. This cell-to-cell communication occurs between bone cells including osteoblasts, osteoclasts and osteocytes, and is important in both bone formation and bone resorption. Connexin (Cx) 43 is the predominant gap junction protein in bone cells, and facilitates the communication of cellular signals either through docking of gap junctions between two cells, or through the formation of un-paired hemichannels. Systemic deletion of Cx43 results in perinatal lethality, so conditional deletion models are necessary to study the postnatal role of gap junctions in bone. These models provide the opportunity to determine the role of gap junctions in specific bone cells, notably the osteocyte. In this review, we summarize the key roles that gap junctions and hemichannels in osteocytes play in bone cell response to many stimuli including mechanical loading, intracellular and extracellular stimuli, such as parathyroid hormone, PGE2, plasma calcium levels and pH, as well as in maintaining osteocyte survival.
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Affiliation(s)
- Alayna E Loiselle
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation, Penn State College of Medicine, Hershey, PA 17033, USA
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37
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Kim CH, Yoo YM. Fluid shear stress and melatonin in combination activate anabolic proteins in MC3T3-E1 osteoblast cells. J Pineal Res 2013; 54:453-61. [PMID: 23397978 DOI: 10.1111/jpi.12043] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2012] [Accepted: 01/11/2013] [Indexed: 12/19/2022]
Abstract
In this study, we investigated whether fluid shear stress and melatonin in combination stimulate the anabolic proteins through the phosphorylation of extracellular signal-regulated kinase (p-ERK) in MC3T3-E1 osteoblast cells. First, we researched why fluid shear stress and melatonin in combination influence cell survival. Fluid shear stress (1 hr) and melatonin (1 mM) in combination reduced autophagic marker LC3-II compared with fluid shear stress (1 hr) and/or melatonin (0.1 mM). Under the same conditions for fluid shear stress, markers of cell survival signaling pathway p-ERK, phosphorylation of serine-threonine protein kinase (p-Akt), phosphorylation of mammalian target of rapamycin (p-mTOR), and p85-S6K were investigated. p-Akt, p-mTOR (Ser 2481) expressions increased with the addition of 1 mM melatonin prior to 0.1 mM melatonin treatment. However, p-S6K expression did not change significantly. Next, mitochondria activity including Bcl-2, Bax, catalase, and Mn-superoxide dismutase (Mn-SOD) were studied. Expressions of Bcl-2, Bax, and catalase proteins were low under fluid shear stress plus 1 mM melatonin compared with only fluid shear stress alone, whereas Mn-SOD expression was high compared with conditions of no fluid shear stress. Finally, the anabolic proteins of bone, osteoprotegerin, type I collagen (collagen I), and bone sialoprotein II (BSP II) were checked. These proteins increased with combined fluid shear stress (1, 4 hr) and melatonin (0.1, 1 mM). Together, these results suggest that fluid shear stress and melatonin in combination may increase the expression of anabolic proteins through the p-ERK in MC3T3-E1 osteoblast cells. Therefore, fluid shear stress in combination with melatonin may promote the anabolic response of osteoblasts.
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Affiliation(s)
- Chi Hyun Kim
- Department of Biomedical Engineering, College of Health Science, Yonsei University, Wonju, Gangwon-do, Korea
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38
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Boccafoschi F, Mosca C, Ramella M, Valente G, Cannas M. The effect of mechanical strain on soft (cardiovascular) and hard (bone) tissues: common pathways for different biological outcomes. Cell Adh Migr 2013; 7:165-73. [PMID: 23287581 PMCID: PMC3954035 DOI: 10.4161/cam.23020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Mechanical stress plays a pivotal role in developing and maintaining tissues functionalities. Cells are constantly subjected to strain and compressive forces that are sensed by specialized membrane mechanosensors and converted in biochemical signals able to differently influence cellular behavior in terms of surviving, differentiation and extracellular matrix remodeling. This review focuses on the effects of mechanical strain on soft and hard tissues. Unexpectedly, different cells share almost the same membrane mechanosensors and the relative intracellular pathways, but to ultimately obtain very different biological effects. The events occurring in cardiovascular and bone tissues are treated in details, showing that integrins, cadherins, growth factor receptors and ions channels specifically expressed in the different tissues are the major actors of the sight. However, MAPkinases and RhoGTPases are mainly involved in the biochemical intracellular signaling directed to nuclear modifications.
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Affiliation(s)
- Francesca Boccafoschi
- Department of Health Sciences, University of Piemonte Orientale A. Avogadro, Novara, Italy.
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39
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Genetos DC, Zhou Z, Li Z, Donahue HJ. Age-related changes in gap junctional intercellular communication in osteoblastic cells. J Orthop Res 2012; 30:1979-84. [PMID: 22696456 PMCID: PMC3640546 DOI: 10.1002/jor.22172] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Accepted: 05/22/2012] [Indexed: 02/04/2023]
Abstract
Aging demonstrates deleterious effects upon the skeleton which can predispose an individual to osteoporosis and related fractures. Despite the well-documented evidence that aging decreases bone formation, there remains little understanding whereby cellular aging alters skeletal homeostasis. We, and others, have previously demonstrated that gap junctions--membrane-spanning channels that allow direct cell-to-cell conductance of small signaling molecules--are critically involved in osteoblast differentiation and skeletal homeostasis. We examined whether the capacity of rat osteoblastic cells to form gap junctions and respond to known modulators of gap junction intercellular communication (GJIC) was dependent on the age of the animal from which they were isolated. We observed no effect of age upon osteoblastic Cx43 mRNA, protein or GJIC. We also examined age-related changes in PTH-stimulated GJIC. PTH demonstrated age-dependent effects upon GJIC: Osteoblastic cells from young rats increased GJIC in response to PTH, whereas there was no change in GJIC in response to PTH in osteoblastic cells from mature or old rats. PTH-stimulated GJIC occurred independently of changes in Cx43 mRNA or protein expression. Cholera toxin significantly increased GJIC in osteoblastic cells from young rats compared to those from mature and old rats. These data demonstrate an age-related impairment in the capacity of osteoblastic cells to generate functional gap junctions in response to PTH, and suggest that an age-related defect in G protein-coupled adenylate cyclase activity at least partially contributes to decreased PTH-stimulated GJIC.
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Affiliation(s)
- Damian C. Genetos
- Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California-Davis, Davis, CA
| | - Zhiyi Zhou
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation, The Pennsylvania State University College of Medicine, Hershey, PA
| | - Zhongyong Li
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation, The Pennsylvania State University College of Medicine, Hershey, PA
| | - Henry J. Donahue
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation, The Pennsylvania State University College of Medicine, Hershey, PA
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40
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Lloyd SA, Lewis GS, Zhang Y, Paul EM, Donahue HJ. Connexin 43 deficiency attenuates loss of trabecular bone and prevents suppression of cortical bone formation during unloading. J Bone Miner Res 2012; 27:2359-72. [PMID: 22714552 PMCID: PMC3683470 DOI: 10.1002/jbmr.1687] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Connexin 43 (Cx43) is the most abundant gap junction protein in bone and has been demonstrated as an integral component of skeletal homeostasis. In the present study, we sought to further refine the role of Cx43 in the response to mechanical unloading by subjecting skeletally mature mice with a bone-specific deletion of Cx43 (cKO) to 3 weeks of mechanical unloading via hindlimb suspension (HLS). The HLS model was selected to recapitulate the effects of skeletal unloading due to prolonged bed rest, reduced activity associated with aging, and spaceflight microgravity. At baseline, the cortical bone of cKO mice displayed an osteopenic phenotype, with expanded cortices, decreased cortical thickness, decreased bone mineral density, and increased porosity. There was no baseline trabecular phenotype. After 3 weeks of HLS, wild-type (WT) mice experienced a substantial decline in trabecular bone volume fraction, connectivity density, trabecular thickness, and trabecular tissue mineral density. These deleterious effects were attenuated in cKO mice. Conversely, there was a similar and significant amount of cortical bone loss in both WT and cKO. Interestingly, mechanical testing revealed a greater loss of strength and rigidity for cKO during HLS. Analysis of double-label quantitative histomorphometry data demonstrated a substantial decrease in bone formation rate, mineralizing surface, and mineral apposition rate at both the periosteal and endocortical surfaces of the femur after unloading of WT mice. This suppression of bone formation was not observed in cKO mice, in which parameters were maintained at baseline levels. Taken together, the results of the present study indicate that Cx43 deficiency desensitizes bone to the effects of mechanical unloading, and that this may be due to an inability of mechanosensing osteocytes to effectively communicate the unloading state to osteoblasts to suppress bone formation. Cx43 may represent a novel therapeutic target for investigation as a countermeasure for age-related and unloading-induced bone loss.
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Affiliation(s)
- Shane A Lloyd
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation, Penn State College of Medicine, Hershey, PA 17033, USA
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41
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Jahani M, Genever PG, Patton RJ, Ahwal F, Fagan MJ. The effect of osteocyte apoptosis on signalling in the osteocyte and bone lining cell network: a computer simulation. J Biomech 2012; 45:2876-83. [PMID: 23040883 DOI: 10.1016/j.jbiomech.2012.08.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 07/18/2012] [Accepted: 08/09/2012] [Indexed: 02/03/2023]
Abstract
Osteocytes play a critical role in the regulation of bone remodelling by translating strain due to mechanical loading into biochemical signals transmitted through the interconnecting lacuno-canalicular network to bone lining cells (BLCs) on the bone surface. This work aims to examine the effects of disruption of that intercellular communication by simulation of osteocyte apoptosis in the bone matrix. A model of a uniformly distributed osteocyte network has been developed that simulates the signalling through the network to the BLCs based on strain level. Bi-directional and asymmetric communication between neighbouring osteocytes and BLCs is included. The effect of osteocyte apoptosis is examined by preventing signalling at and through the affected cells. The simulation shows that apoptosis of only 3% of the osteocyte cells leads to a significant reduction in the peak signal at the BLCs. Furthermore, experiments with the model confirm how important the location and density of the apoptotic osteocytes are to the signalling received at the bone surface. With 5% and 9% osteocyte apoptosis, the mean peak BLC levels were reduced by 25% and 37% respectively. Such a significant reduction in the signal at the BLCs may explain a possible mechanism that leads to the increased remodelling and eventual bone loss observed with osteoporosis. More generally, it provides a unique framework for a broader exploration of the role of osteocyte and bi-directional and asymmetric cell-cell communication in mechanotransduction, and the effects of disruption to that communication.
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Affiliation(s)
- Masoumeh Jahani
- Department of Engineering, University of Hull, Hull, HU6 7RX, UK.
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Stern AR, Stern MM, Van Dyke ME, Jähn K, Prideaux M, Bonewald LF. Isolation and culture of primary osteocytes from the long bones of skeletally mature and aged mice. Biotechniques 2012; 52:361-73. [PMID: 22668415 PMCID: PMC3612989 DOI: 10.2144/0000113876] [Citation(s) in RCA: 138] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Accepted: 05/18/2012] [Indexed: 12/20/2022] Open
Abstract
The purpose of this work was to establish a methodology to enable the isolation and study of osteocytes from skeletally mature young (4-month-old) and old (22-month-old) mice. The location of osteocytes deep within bone is ideal for their function as mechanosensors. However, this location makes the observation and study of osteocytes in vivo technically difficult. Osteocytes were isolated from murine long bones through a process of extended collagenase digestions combined with EDTA-based decalcification. A tissue homogenizer was used to reduce the remaining bone fragments to a suspension of bone particles, which were placed in culture to yield an outgrowth of osteocyte-like cells. All of the cells obtained from this outgrowth that displayed an osteocyte-like morphology stained positive for the osteocyte marker E11/GP38. The osteocyte phenotype was further confirmed by a lack of staining for alkaline phosphatase and the absence of collagen1a1 expression. The outgrowth of osteocytes also expressed additional osteocyte-specific genes such as Sost and Mepe. This technique facilitates the isolation of osteocytes from skeletally mature bone. This novel enabling methodology should prove useful in advancing our understanding of the roles mature osteocytes play in bone health and disease.
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Affiliation(s)
- Amber Rath Stern
- Mechanical Engineering and Oral Biology, University of Missouri Kansas City, Kansas City, MO, USA.
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43
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Thompson WR, Rubin CT, Rubin J. Mechanical regulation of signaling pathways in bone. Gene 2012; 503:179-93. [PMID: 22575727 DOI: 10.1016/j.gene.2012.04.076] [Citation(s) in RCA: 268] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Revised: 03/20/2012] [Accepted: 04/22/2012] [Indexed: 12/21/2022]
Abstract
A wide range of cell types depend on mechanically induced signals to enable appropriate physiological responses. The skeleton is particularly dependent on mechanical information to guide the resident cell population towards adaptation, maintenance and repair. Research at the organ, tissue, cell and molecular levels has improved our understanding of how the skeleton can recognize the functional environment, and how these challenges are translated into cellular information that can site-specifically alter phenotype. This review first considers those cells within the skeleton that are responsive to mechanical signals, including osteoblasts, osteoclasts, osteocytes and osteoprogenitors. This is discussed in light of a range of experimental approaches that can vary parameters such as strain, fluid shear stress, and pressure. The identity of mechanoreceptor candidates is approached, with consideration of integrins, pericellular tethers, focal adhesions, ion channels, cadherins, connexins, and the plasma membrane including caveolar and non-caveolar lipid rafts and their influence on integral signaling protein interactions. Several mechanically regulated intracellular signaling cascades are detailed including activation of kinases (Akt, MAPK, FAK), β-catenin, GTPases, and calcium signaling events. While the interaction of bone cells with their mechanical environment is complex, an understanding of mechanical regulation of bone signaling is crucial to understanding bone physiology, the etiology of diseases such as osteoporosis, and to the development of interventions to improve bone strength.
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Affiliation(s)
- William R Thompson
- Department of Medicine, University of North Carolina, Chapel Hill, NC 27599, USA.
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Mechanical stress-activated integrin α5β1 induces opening of connexin 43 hemichannels. Proc Natl Acad Sci U S A 2012; 109:3359-64. [PMID: 22331870 DOI: 10.1073/pnas.1115967109] [Citation(s) in RCA: 179] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The connexin 43 (Cx43) hemichannel (HC) in the mechanosensory osteocytes is a major portal for the release of factors responsible for the anabolic effects of mechanical loading on bone formation and remodeling. However, little is known about how the Cx43 molecule responds to mechanical stimulation leading to the opening of the HC. Here, we demonstrate that integrin α5β1 interacts directly with Cx43 and that this interaction is required for mechanical stimulation-induced opening of the Cx43 HC. Direct mechanical perturbation via magnetic beads or conformational activation of integrin α5β1 leads to the opening of the Cx43 HC, and this role of the integrin is independent of its association with an extracellular fibronectin substrate. PI3K signaling is responsible for the shear stress-induced conformational activation of integrin α5β1 leading to the opening of the HC. These results identify an unconventional function of integrin that acts as a mechanical tether to induce opening of the HC and provide a mechanism connecting the effect of mechanical forces directly to anabolic function of the bone.
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Salameh A, Dhein S. Effects of mechanical forces and stretch on intercellular gap junction coupling. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:147-56. [PMID: 22245380 DOI: 10.1016/j.bbamem.2011.12.030] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Revised: 12/17/2011] [Accepted: 12/27/2011] [Indexed: 01/27/2023]
Abstract
Mechanical forces provide fundamental physiological stimulus in living organisms. Recent investigations demonstrated how various types of mechanical load, like strain, pressure, shear stress, or cyclic stretch can affect cell biology and gap junction intercellular communication (GJIC). Depending on the cell type, the type of mechanical load and on strength and duration of application, these forces can induce hypertrophic processes and modulate the expression and function of certain connexins such as Cx43, while others such as Cx37 or Cx40 are reported to be less mechanosensitive. In particular, not only expression but also subcellular localization of Cx43 is altered in cardiomyocytes submitted to cyclic mechanical stretch resulting in the typical elongated cell shape with an accentuation of Cx43 at the cell poles. In the heart both cardiomyocytes and fibroblasts can alter their GJIC in response to mechanical load. In the vasculature both endothelial cells and smooth muscle cells are subject to strain and cyclic stretch resulting from the pulsatile flow. In addition, vascular endothelial cells are mainly affected by shear stress resulting from the blood flow parallel to their surface. These mechanical forces lead to a regulation of GJIC in vascular tissue. In bones, osteocytes and osteoblasts are coupled via gap junctions, which also react to mechanical forces. Since gap junctions are involved in regulation of cell growth and differentiation, the mechanosensitivity of the regulation of these channels might open new perspectives to explain how cells can respond to mechanical load, and how stretch induces self-organization of a cell layer which might have implications for embryology and the development of organs. This article is part of a Special Issue entitled: The Communicating junctions, roles and dysfunctions.
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Affiliation(s)
- Aida Salameh
- Clinic for Pediatric Cardiology, University of Leipzig, Heart Centre, Germany
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46
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Lim JY, Loiselle AE, Lee JS, Zhang Y, Salvi JD, Donahue HJ. Optimizing the osteogenic potential of adult stem cells for skeletal regeneration. J Orthop Res 2011; 29:1627-33. [PMID: 21509820 PMCID: PMC3263698 DOI: 10.1002/jor.21441] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Accepted: 03/31/2011] [Indexed: 02/04/2023]
Abstract
Adult stem cells, including mesenchymal stem cells, display plasticity in that they can differentiate toward various lineages including bone cells, cartilage cells, fat cells, and other types of connective tissue cells. However, it is not clear what factors direct adult stem cell lineage commitment and terminal differentiation. Emerging evidence suggests that extracellular physical cues have the potential to control stem cell lineage specification. In this perspective article, we review recent findings on biomaterial surface and mechanical signal regulation of stem cell differentiation. Specifically, we focus on stem cell response to substrate nanoscale topography and fluid flow induced shear stress and how these physical factors may regulate stem cell osteoblastic differentiation in vitro.
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Affiliation(s)
- Jung Yul Lim
- Department of Engineering Mechanics, University of Nebraska, Lincoln, Nebraska 68588
,The Graduate School of Dentistry, Kyung Hee University, Seoul, Korea
| | - Alayna E. Loiselle
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation, Center for Biomedical Devices and Functional Tissue Engineering, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania 17033
| | - Jeong Soon Lee
- Department of Engineering Mechanics, University of Nebraska, Lincoln, Nebraska 68588
| | - Yue Zhang
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation, Center for Biomedical Devices and Functional Tissue Engineering, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania 17033
| | - Joshua D. Salvi
- Weill Cornell Medical College, Cornell University, New York, New York 10021
| | - Henry J. Donahue
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation, Center for Biomedical Devices and Functional Tissue Engineering, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania 17033
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Batra N, Kar R, Jiang JX. Gap junctions and hemichannels in signal transmission, function and development of bone. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1909-18. [PMID: 21963408 DOI: 10.1016/j.bbamem.2011.09.018] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Revised: 09/03/2011] [Accepted: 09/15/2011] [Indexed: 10/17/2022]
Abstract
Gap junctional intercellular communication (GJIC) mediated by connexins, in particular connexin 43 (Cx43), plays important roles in regulating signal transmission among different bone cells and thereby regulates development, differentiation, modeling and remodeling of the bone. GJIC regulates osteoblast formation, differentiation, survival and apoptosis. Osteoclast formation and resorptive ability are also reported to be modulated by GJIC. Furthermore, osteocytes utilize GJIC to coordinate bone remodeling in response to anabolic factors and mechanical loading. Apart from gap junctions, connexins also form hemichannels, which are localized on the cell surface and function independently of the gap junction channels. Both these channels mediate the transfer of molecules smaller than 1.2kDa including small ions, metabolites, ATP, prostaglandin and IP(3). The biological importance of the communication mediated by connexin-forming channels in bone development is revealed by the low bone mass and osteoblast dysfunction in the Cx43-null mice and the skeletal malformations observed in occulodentodigital dysplasia (ODDD) caused by mutations in the Cx43 gene. The current review summarizes the role of gap junctions and hemichannels in regulating signaling, function and development of bone cells. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.
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Affiliation(s)
- Nidhi Batra
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX, USA
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Enhanced osteoclastic resorption and responsiveness to mechanical load in gap junction deficient bone. PLoS One 2011; 6:e23516. [PMID: 21897843 PMCID: PMC3163577 DOI: 10.1371/journal.pone.0023516] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2010] [Accepted: 07/20/2011] [Indexed: 11/20/2022] Open
Abstract
Emerging evidence suggests that connexin mediated gap junctional intercellular communication contributes to many aspects of bone biology including bone development, maintenance of bone homeostasis and responsiveness of bone cells to diverse extracellular signals. Deletion of connexin 43, the predominant gap junction protein in bone, is embryonic lethal making it challenging to examine the role of connexin 43 in bone in vivo. However, transgenic murine models in which only osteocytes and osteoblasts are deficient in connexin 43, and which are fully viable, have recently been developed. Unfortunately, the bone phenotype of different connexin 43 deficient models has been variable. To address this issue, we used an osteocalcin driven Cre-lox system to create osteoblast and osteocyte specific connexin 43 deficient mice. These mice displayed bone loss as a result of increased bone resorption and osteoclastogenesis. The mechanism underlying this increased osteoclastogenesis included increases in the osteocytic, but not osteoblastic, RANKL/OPG ratio. Previous in vitro studies suggest that connexin 43 deficient bone cells are less responsive to biomechanical signals. Interestingly, and in contrast to in vitro studies, we found that connexin 43 deficient mice displayed an enhanced anabolic response to mechanical load. Our results suggest that transient inhibition of connexin 43 expression and gap junctional intercellular communication may prove a potentially powerful means of enhancing the anabolic response of bone to mechanical loading.
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Jeon OH, Yoo YM, Kim KH, Jacobs CR, Kim CH. Primary Cilia-Mediated Osteogenic Response to Fluid Flow Occurs via Increases in Focal Adhesion and Akt Signaling Pathway in MC3T3-E1 Osteoblastic Cells. Cell Mol Bioeng 2011. [DOI: 10.1007/s12195-011-0191-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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50
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Weinbaum S, Duan Y, Thi MM, You L. An Integrative Review of Mechanotransduction in Endothelial, Epithelial (Renal) and Dendritic Cells (Osteocytes). Cell Mol Bioeng 2011; 4:510-537. [PMID: 23976901 DOI: 10.1007/s12195-011-0179-6] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In this review we will examine from a biomechanical and ultrastructural viewpoint how the cytoskeletal specialization of three basic cell types, endothelial cells (ECs), epithelial cells (renal tubule) and dendritic cells (osteocytes), enables the mechano-sensing of fluid flow in both their native in vivo environment and in culture, and the downstream signaling that is initiated at the molecular level in response to fluid flow. These cellular responses will be discussed in terms of basic mysteries and paradoxes encountered by each cell type. In ECs fluid shear stress (FSS) is nearly entirely attenuated by the endothelial glycocalyx that covers their apical membrane and yet FSS is communicated to both intracellular and junctional molecular components in activating a wide variety of signaling pathways. The same is true in proximal tubule (PT) cells where a dense brush border of microvilli covers the apical surface and the flow at the apical membrane is negligible. A four decade old unexplained mystery is the ability of PT epithelia to reliably reabsorb 60% of the flow entering the tubule regardless of the glomerular filtration rate. In the cortical collecting duct (CCD) the flow rates are so low that a special sensing apparatus, a primary cilia is needed to detect very small variations in tubular flow. In bone it has been a century old mystery as to how osteocytes embedded in a stiff mineralized tissue are able to sense miniscule whole tissue strains that are far smaller than the cellular level strains required to activate osteocytes in vitro.
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Affiliation(s)
- Sheldon Weinbaum
- Department of Biomedical Engineering, The City College of the City University of New York, New York, NY 10031, USA
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