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Chen J, Aido M, Roschger A, van Tol A, Checa S, Willie BM, Weinkamer R. Spatial variations in the osteocyte lacuno-canalicular network density and analysis of the connectomic parameters. PLoS One 2024; 19:e0303515. [PMID: 38743675 PMCID: PMC11093372 DOI: 10.1371/journal.pone.0303515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 04/05/2024] [Indexed: 05/16/2024] Open
Abstract
Osteocyte lacuno-canalicular network (LCN) is comprised of micrometre-sized pores and submicrometric wide channels in bone. Accumulating evidence suggests multiple functions of this network in material transportation, mechanobiological signalling, mineral homeostasis and bone remodelling. Combining rhodamine staining and confocal laser scanning microscopy, the longitudinal cross-sections of six mouse tibiae were imaged, and the connectome of the network was quantified with a focus on the spatial heterogeneities of network density, connectivity and length of canaliculi. In-vivo loading and double calcein labelling on these tibiae allowed differentiating the newly formed bone from the pre-existing regions. The canalicular density of the murine cortical bone varied between 0.174 and 0.243 μm/μm3, and therefore is three times larger than the corresponding value for human femoral midshaft osteons. The spatial heterogeneity of the network was found distinctly more pronounced across the cortex than along the cortex. We found that in regions with a dense network, the LCN conserves its largely tree-like character, but increases the density by including shorter canaliculi. The current study on healthy mice should serve as a motivating starting point to study the connectome of genetically modified mice, including models of bone diseases and of reduced mechanoresponse.
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Affiliation(s)
- Junning Chen
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
- Department of Engineering, Faculty of Environment, Science and Economy, University of Exeter, Exeter, United Kingdom
| | - Marta Aido
- Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Berlin, Germany
- Berlin-Brandenburg School for Regenerative Therapies (BSRT), Berlin, Germany
| | - Andreas Roschger
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
- Department of Chemistry and Physics of Materials, Paris-Lodron-University of Salzburg, Salzburg, Austria
| | - Alexander van Tol
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
| | - Sara Checa
- Julius Wolff Institute, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Bettina M. Willie
- Department of Pediatric Surgery, Research Centre, Shriners Hospital for Children-Canada, McGill University, Montreal, Canada
| | - Richard Weinkamer
- Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
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Kelly MM, Sharma K, Wright CS, Yi X, Reyes Fernandez PC, Gegg AT, Gorrell TA, Noonan ML, Baghdady A, Sieger JA, Dolphin AC, Warden SJ, Deosthale P, Plotkin LI, Sankar U, Hum JM, Robling AG, Farach-Carson MC, Thompson WR. Loss of the auxiliary α 2δ 1 voltage-sensitive calcium channel subunit impairs bone formation and anabolic responses to mechanical loading. JBMR Plus 2024; 8:ziad008. [PMID: 38505532 PMCID: PMC10945727 DOI: 10.1093/jbmrpl/ziad008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 10/31/2023] [Accepted: 11/27/2023] [Indexed: 03/21/2024] Open
Abstract
Voltage-sensitive calcium channels (VSCCs) influence bone structure and function, including anabolic responses to mechanical loading. While the pore-forming (α1) subunit of VSCCs allows Ca2+ influx, auxiliary subunits regulate the biophysical properties of the pore. The α2δ1 subunit influences gating kinetics of the α1 pore and enables mechanically induced signaling in osteocytes; however, the skeletal function of α2δ1 in vivo remains unknown. In this work, we examined the skeletal consequences of deleting Cacna2d1, the gene encoding α2δ1. Dual-energy X-ray absorptiometry and microcomputed tomography imaging demonstrated that deletion of α2δ1 diminished bone mineral content and density in both male and female C57BL/6 mice. Structural differences manifested in both trabecular and cortical bone for males, while the absence of α2δ1 affected only cortical bone in female mice. Deletion of α2δ1 impaired skeletal mechanical properties in both sexes, as measured by three-point bending to failure. While no changes in osteoblast number or activity were found for either sex, male mice displayed a significant increase in osteoclast number, accompanied by increased eroded bone surface and upregulation of genes that regulate osteoclast differentiation. Deletion of α2δ1 also rendered the skeleton insensitive to exogenous mechanical loading in males. While previous work demonstrates that VSCCs are essential for anabolic responses to mechanical loading, the mechanism by which these channels sense and respond to force remained unclear. Our data demonstrate that the α2δ1 auxiliary VSCC subunit functions to maintain baseline bone mass and strength through regulation of osteoclast activity and also provides skeletal mechanotransduction in male mice. These data reveal a molecular player in our understanding of the mechanisms by which VSCCs influence skeletal adaptation.
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Affiliation(s)
- Madison M Kelly
- Department of Physical Therapy, School of Health and Human Sciences, Indiana University, Indianapolis, IN 46202, United States
- College of Osteopathic Medicine, Marian University, Indianapolis, IN 46222, United States
| | - Karan Sharma
- Department of Physical Therapy, School of Health and Human Sciences, Indiana University, Indianapolis, IN 46202, United States
- College of Osteopathic Medicine, Marian University, Indianapolis, IN 46222, United States
| | - Christian S Wright
- Department of Physical Therapy, School of Health and Human Sciences, Indiana University, Indianapolis, IN 46202, United States
- Indiana Center for Musculoskeletal Health, Indiana University, Indianapolis, IN 46202, United States
| | - Xin Yi
- Department of Physical Therapy, School of Health and Human Sciences, Indiana University, Indianapolis, IN 46202, United States
- Indiana Center for Musculoskeletal Health, Indiana University, Indianapolis, IN 46202, United States
| | - Perla C Reyes Fernandez
- Department of Physical Therapy, School of Health and Human Sciences, Indiana University, Indianapolis, IN 46202, United States
- Indiana Center for Musculoskeletal Health, Indiana University, Indianapolis, IN 46202, United States
| | - Aaron T Gegg
- Department of Physical Therapy, School of Health and Human Sciences, Indiana University, Indianapolis, IN 46202, United States
| | - Taylor A Gorrell
- Department of Physical Therapy, School of Health and Human Sciences, Indiana University, Indianapolis, IN 46202, United States
| | - Megan L Noonan
- Department of Medical and Molecular Genetics, Indiana University, Indianapolis, IN 46202, United States
| | - Ahmed Baghdady
- College of Osteopathic Medicine, Marian University, Indianapolis, IN 46222, United States
| | - Jacob A Sieger
- College of Osteopathic Medicine, Marian University, Indianapolis, IN 46222, United States
| | - Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College of London, Gower Street, London WC1E 6BT, United Kingdom
| | - Stuart J Warden
- Department of Physical Therapy, School of Health and Human Sciences, Indiana University, Indianapolis, IN 46202, United States
- Indiana Center for Musculoskeletal Health, Indiana University, Indianapolis, IN 46202, United States
- La Trobe Sport and Exercise Medicine Research Centre, La Trobe University, Melbourne Victoria 3086, DX 211319, Australia
| | - Padmini Deosthale
- Indiana Center for Musculoskeletal Health, Indiana University, Indianapolis, IN 46202, United States
- Department of Anatomy, Cell Biology, & Physiology, Indiana University, Indianapolis, IN 46202, United States
| | - Lilian I Plotkin
- Indiana Center for Musculoskeletal Health, Indiana University, Indianapolis, IN 46202, United States
- Department of Anatomy, Cell Biology, & Physiology, Indiana University, Indianapolis, IN 46202, United States
| | - Uma Sankar
- Indiana Center for Musculoskeletal Health, Indiana University, Indianapolis, IN 46202, United States
- Department of Anatomy, Cell Biology, & Physiology, Indiana University, Indianapolis, IN 46202, United States
| | - Julia M Hum
- College of Osteopathic Medicine, Marian University, Indianapolis, IN 46222, United States
- Indiana Center for Musculoskeletal Health, Indiana University, Indianapolis, IN 46202, United States
| | - Alexander G Robling
- Indiana Center for Musculoskeletal Health, Indiana University, Indianapolis, IN 46202, United States
- Department of Anatomy, Cell Biology, & Physiology, Indiana University, Indianapolis, IN 46202, United States
| | - Mary C Farach-Carson
- Department of Diagnostic & Biomedical Sciences, University of Texas Health Science Center at Houston School of Dentistry, Houston, TX 77054, United States
| | - William R Thompson
- Department of Physical Therapy, School of Health and Human Sciences, Indiana University, Indianapolis, IN 46202, United States
- College of Osteopathic Medicine, Marian University, Indianapolis, IN 46222, United States
- Indiana Center for Musculoskeletal Health, Indiana University, Indianapolis, IN 46202, United States
- Department of Anatomy, Cell Biology, & Physiology, Indiana University, Indianapolis, IN 46202, United States
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3
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Lee BS, Murray C, Liu J, Kim M, Hwang MS, Yueh T, Mansour M, Qamar S, Agarwal G, Kim DG. The myosin and RhoGAP MYO9B influences osteocyte dendrite growth and responses to mechanical stimuli. Front Bioeng Biotechnol 2023; 11:1243303. [PMID: 37675403 PMCID: PMC10477788 DOI: 10.3389/fbioe.2023.1243303] [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: 06/20/2023] [Accepted: 08/11/2023] [Indexed: 09/08/2023] Open
Abstract
Introduction: Myosin IXB (MYO9B) is an unconventional myosin with RhoGAP activity and thus is a regulator of actin cytoskeletal organization. MYO9B was previously shown to be necessary for skeletal growth and health and to play a role in actin-based functions of both osteoblasts and osteoclasts. However, its role in responses to mechanical stimulation of bone cells has not yet been described. Therefore, experiments were undertaken to determine the role of MYO9B in bone cell responses to mechanical stress both in vitro and in vivo. Methods: MYO9B expression was knocked down in osteoblast and osteocyte cell lines using RNA interference and the resulting cells were subjected to mechanical stresses including cyclic tensile strain, fluid shear stress, and plating on different substrates (no substrate vs. monomeric or polymerized collagen type I). Osteocytic cells were also subjected to MYO9B regulation through Slit-Robo signaling. Further, wild-type or Myo9b -/- mice were subjected to a regimen of whole-body vibration (WBV) and changes in bone quality were assessed by micro-CT. Results: Unlike control cells, MYO9B-deficient osteoblastic cells subjected to uniaxial cyclic tensile strain were unable to orient their actin stress fibers perpendicular to the strain. Osteocytic cells in which MYO9B was knocked down exhibited elongated dendrites but were unable to respond normally to treatments that increase dendrite length such as fluid shear stress and Slit-Robo signaling. Osteocytic responses to mechanical stimuli were also found to be dependent on the polymerization state of collagen type I substrates. Wild-type mice responded to WBV with increased bone tissue mineral density values while Myo9b -/- mice responded with bone loss. Discussion: These results demonstrate that MYO9B plays a key role in mechanical stress-induced responses of bone cells in vitro and in vivo.
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Affiliation(s)
- Beth S. Lee
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Cynthia Murray
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Jie Liu
- Division of Orthodontics, College of Dentistry, The Ohio State University, Columbus, OH, United States
| | - Minji Kim
- Department of Orthodontics, Graduate School of Clinical Dentistry, Ewha Womans University, Seoul, Republic of Korea
| | - Min Sik Hwang
- Division of Orthodontics, College of Dentistry, The Ohio State University, Columbus, OH, United States
| | - Tina Yueh
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Myrna Mansour
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Sana Qamar
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Gunjan Agarwal
- Department of Mechanical and Aerospace Engineering, College of Engineering, The Ohio State University, Columbus, OH, United States
| | - Do-Gyoon Kim
- Division of Orthodontics, College of Dentistry, The Ohio State University, Columbus, OH, United States
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Reyes Fernandez PC, Wright CS, Farach-Carson MC, Thompson WR. Examining Mechanisms for Voltage-Sensitive Calcium Channel-Mediated Secretion Events in Bone Cells. Calcif Tissue Int 2023; 113:126-142. [PMID: 37261463 PMCID: PMC11008533 DOI: 10.1007/s00223-023-01097-w] [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: 01/31/2023] [Accepted: 05/16/2023] [Indexed: 06/02/2023]
Abstract
In addition to their well-described functions in cell excitability, voltage-sensitive calcium channels (VSCCs) serve a critical role in calcium (Ca2+)-mediated secretion of pleiotropic paracrine and endocrine factors, including those produced in bone. Influx of Ca2+ through VSCCs activates intracellular signaling pathways to modulate a variety of cellular processes that include cell proliferation, differentiation, and bone adaptation in response to mechanical stimuli. Less well understood is the role of VSCCs in the control of bone and calcium homeostasis mediated through secreted factors. In this review, we discuss the various functions of VSCCs in skeletal cells as regulators of Ca2+ dynamics and detail how these channels might control the release of bioactive factors from bone cells. Because VSCCs are druggable, a better understanding of the multiple functions of these channels in the skeleton offers the opportunity for developing new therapies to enhance and maintain bone and to improve systemic health.
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Affiliation(s)
- Perla C Reyes Fernandez
- Department of Physical Therapy, School of Health and Human Sciences, Indiana University, Indianapolis, IN, 46202, USA
- Center for Musculoskeletal Health, Indiana University, Indianapolis, IN, 46202, USA
| | - Christian S Wright
- Department of Physical Therapy, School of Health and Human Sciences, Indiana University, Indianapolis, IN, 46202, USA
- Center for Musculoskeletal Health, Indiana University, Indianapolis, IN, 46202, USA
| | - Mary C Farach-Carson
- Department of Diagnostic and Biomedical Sciences, School of Dentistry, The University of Texas Health Science Center at Houston, Houston, TX, 77054, USA
- Departments of BioSciences and Bioengineering, Rice University, Houston, TX, 77005, USA
| | - William R Thompson
- Department of Physical Therapy, School of Health and Human Sciences, Indiana University, Indianapolis, IN, 46202, USA.
- Center for Musculoskeletal Health, Indiana University, Indianapolis, IN, 46202, USA.
- Department of Anatomy, Cell Biology and Physiology, School of Medicine, Indiana University, Indianapolis, IN, 46202, USA.
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5
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Qin L, Chen Z, Yang D, He T, Xu Z, Zhang P, Chen D, Yi W, Xiao G. Osteocyte β3 integrin promotes bone mass accrual and force-induced bone formation in mice. J Orthop Translat 2023; 40:58-71. [PMID: 37457310 PMCID: PMC10338905 DOI: 10.1016/j.jot.2023.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Revised: 04/24/2023] [Accepted: 05/08/2023] [Indexed: 07/18/2023] Open
Abstract
Background Cell culture studies demonstrate the importance of β3 integrin in osteocyte mechanotransduction. However, the in vivo roles of osteocyte β3 integrin in the regulation of bone homeostasis and mechanotransduction are poorly defined. Materials and methods To study the in vivo role of osteocyte β3 integrin in bone, we utilized the 10-kb Dmp1 (dentin matrix acidic phosphoprotein 1)-Cre to delete β3 integrin expression in osteocyte in mice. Micro-computerized tomography (μCT), bone histomorphometry and in vitro cell culture experiments were performed to determine the effects of osteocyte β3 integrin loss on bone mass accrual and biomechanical properties. In addition, in vivo tibial loading model was applied to study the possible involvement of osteocyte β3 integrin in the mediation of bone mechanotransduction. Results Deletion of β3 integrin in osteocytes resulted in a low bone mass and impaired biomechanical properties in load-bearing long bones in adult mice. The loss of β3 integrin led to abnormal cell morphology with reduced number and length of dentritic processes in osteocytes. Furthermore, osteocyte β3 integrin loss did not impact the osteoclast formation, but significantly reduced the osteoblast-mediated bone formation rate and reduced the osteogenic differentiation of the bone marrow stromal cells in the bone microenvironment. In addition, mechanical loading failed to accelerate the anabolic bone formation in mutant mice. Conclusions Our studies demonstrate the essential roles of osteocyte β3 integrin in regulating bone mass and mechanotransduction.
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Affiliation(s)
- Lei Qin
- Department of Orthopedics, Huazhong University of Science and Technology Union Shenzhen Hospital, Shenzhen, 518000, China
| | - Zecai Chen
- Department of Orthopedics, Huazhong University of Science and Technology Union Shenzhen Hospital, Shenzhen, 518000, China
| | - Dazhi Yang
- Department of Orthopedics, Huazhong University of Science and Technology Union Shenzhen Hospital, Shenzhen, 518000, China
| | - Tailin He
- Department of Biochemistry, School of Medicine, Southern University of Science and Technology, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, Shenzhen, 518055, China
| | - Zhen Xu
- Department of Orthopedics, Huazhong University of Science and Technology Union Shenzhen Hospital, Shenzhen, 518000, China
| | - Peijun Zhang
- Department of Biochemistry, School of Medicine, Southern University of Science and Technology, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, Shenzhen, 518055, China
| | - Di Chen
- Research Center for Human Tissues and Organs Degeneration, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Weihong Yi
- Department of Orthopedics, Huazhong University of Science and Technology Union Shenzhen Hospital, Shenzhen, 518000, China
| | - Guozhi Xiao
- Department of Biochemistry, School of Medicine, Southern University of Science and Technology, Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Shenzhen Key Laboratory of Cell Microenvironment, Shenzhen, 518055, China
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Mao L, Wang L, Xu J, Zou J. The role of integrin family in bone metabolism and tumor bone metastasis. Cell Death Discov 2023; 9:119. [PMID: 37037822 PMCID: PMC10086008 DOI: 10.1038/s41420-023-01417-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 03/21/2023] [Accepted: 03/24/2023] [Indexed: 04/12/2023] Open
Abstract
Integrins have been the research focus of cell-extracellular matrix adhesion (ECM) and cytokine receptor signal transduction. They are involved in the regulation of bone metabolism of bone precursor cells, mesenchymal stem cells (MSCs), osteoblasts (OBs), osteoclasts (OCs), and osteocytes. Recent studies expanded and updated the role of integrin in bone metabolism, and a large number of novel cytokines were found to activate bone metabolism pathways through interaction with integrin receptors. Integrins act as transducers that mediate the regulation of bone-related cells by mechanical stress, fluid shear stress (FSS), microgravity, hypergravity, extracellular pressure, and a variety of physical factors. Integrins mediate bone metastasis of breast, prostate, and lung cancer by promoting cancer cell adhesion, migration, and survival. Integrin-mediated targeted therapy showed promising prospects in bone metabolic diseases. This review emphasizes the latest research results of integrins in bone metabolism and bone metastasis and provides a vision for treatment strategies.
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Affiliation(s)
- Liwei Mao
- School of Kinesiology, Shanghai University of Sport, 200438, Shanghai, China
| | - Lian Wang
- School of Kinesiology, Shanghai University of Sport, 200438, Shanghai, China
| | - Jiake Xu
- School of Biomedical Sciences, The University of Western Australia, WA, 6009, Perth, Australia
| | - Jun Zou
- School of Kinesiology, Shanghai University of Sport, 200438, Shanghai, China.
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Zhang K, Liu X, Tang Y, Liu Z, Yi Q, Wang L, Geng B, Xia Y. Fluid Shear Stress Promotes Osteoblast Proliferation and Suppresses Mitochondrial-Mediated Osteoblast Apoptosis Through the miR-214-3p-ATF4 Signaling Axis. Physiol Res 2022. [DOI: 10.33549/physiolres.934917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
MicroRNAs (miRNAs) play vital roles in bone metabolism and participate in the mechanically induced bone alterations. The underlying molecular mechanisms by which fluid shear stress (FSS) regulate the proliferative and apoptotic phenotypic changes of osteoblasts remain elusive. The study aimed to investigate the regulatory effects of FSS on osteoblast proliferative and apoptotic phenotypes and the roles of miR-214-3p-ATF4 (activating transcription factor 4) signaling axis in the mechanomodulation processes. FSS promoted the proliferative activity of osteoblasts and suppressed mitochondrial-mediated osteoblast apoptosis. FSS decreased miR-214-3p expression and increased ATF4 expression in MC3T3-E1 osteoblasts. MiR-214-3p inhibited osteoblast proliferative activity and promoted mitochondrial-mediated osteoblast apoptosis. Overexpression of miR-214-3p attenuated FSS-enhanced osteoblast proliferation and FSS-suppressed mitochondrial-mediated osteoblast apoptosis. We validated that ATF4 acted as a target gene of miR-214-3p. Moreover, miR-214 3p regulated osteoblast proliferation and apoptosis through targeting ATF4. Taken together, our study proved that FSS could suppress mitochondrial-mediated osteoblast apoptosis and promote osteoblast proliferation through the miR-214-3p-ATF4 signaling axis.
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Affiliation(s)
- K Zhang
- Department of Orthopaedics, Lanzhou University Second Hospital, Lanzhou Gansu, China, Orthopaedics Key Laboratory of Gansu Province, Lanzhou Gansu, China
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8
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Bolamperti S, Villa I, Rubinacci A. Bone remodeling: an operational process ensuring survival and bone mechanical competence. Bone Res 2022; 10:48. [PMID: 35851054 PMCID: PMC9293977 DOI: 10.1038/s41413-022-00219-8] [Citation(s) in RCA: 98] [Impact Index Per Article: 49.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 05/02/2022] [Accepted: 05/15/2022] [Indexed: 12/12/2022] Open
Abstract
Bone remodeling replaces old and damaged bone with new bone through a sequence of cellular events occurring on the same surface without any change in bone shape. It was initially thought that the basic multicellular unit (BMU) responsible for bone remodeling consists of osteoclasts and osteoblasts functioning through a hierarchical sequence of events organized into distinct stages. However, recent discoveries have indicated that all bone cells participate in BMU formation by interacting both simultaneously and at different differentiation stages with their progenitors, other cells, and bone matrix constituents. Therefore, bone remodeling is currently considered a physiological outcome of continuous cellular operational processes optimized to confer a survival advantage. Bone remodeling defines the primary activities that BMUs need to perform to renew successfully bone structural units. Hence, this review summarizes the current understanding of bone remodeling and future research directions with the aim of providing a clinically relevant biological background with which to identify targets for therapeutic strategies in osteoporosis.
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Affiliation(s)
- Simona Bolamperti
- Osteoporosis and Bone and Mineral Metabolism Unit, IRCCS San Raffaele Hospital, Via Olgettina 60, 20132, Milano, Italy
| | - Isabella Villa
- Osteoporosis and Bone and Mineral Metabolism Unit, IRCCS San Raffaele Hospital, Via Olgettina 60, 20132, Milano, Italy
| | - Alessandro Rubinacci
- Osteoporosis and Bone and Mineral Metabolism Unit, IRCCS San Raffaele Hospital, Via Olgettina 60, 20132, Milano, Italy.
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9
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Abstract
Disuse osteoporosis describes a state of bone loss due to local skeletal unloading or systemic immobilization. This review will discuss advances in the field that have shed light on clinical observations, mechanistic insights and options for the treatment of disuse osteoporosis. Clinical settings of disuse osteoporosis include spinal cord injury, other neurological and neuromuscular disorders, immobilization after fractures and bed rest (real or modeled). Furthermore, spaceflight-induced bone loss represents a well-known adaptive process to microgravity. Clinical studies have outlined that immobilization leads to immediate bone loss in both the trabecular and cortical compartments accompanied by relatively increased bone resorption and decreased bone formation. The fact that the low bone formation state has been linked to high levels of the osteocyte-secreted protein sclerostin is one of the many findings that has brought matrix-embedded, mechanosensitive osteocytes into focus in the search for mechanistic principles. Previous basic research has primarily involved rodent models based on tail suspension, spaceflight and other immobilization methods, which have underlined the importance of osteocytes in the pathogenesis of disuse osteoporosis. Furthermore, molecular-based in vitro and in vivo approaches have revealed that osteocytes sense mechanical loading through mechanosensors that translate extracellular mechanical signals to intracellular biochemical signals and regulate gene expression. Osteocytic mechanosensors include the osteocyte cytoskeleton and dendritic processes within the lacuno-canalicular system (LCS), ion channels (e.g., Piezo1), extracellular matrix, primary cilia, focal adhesions (integrin-based) and hemichannels and gap junctions (connexin-based). Overall, disuse represents one of the major factors contributing to immediate bone loss and osteoporosis, and alterations in osteocytic pathways appear crucial to the bone loss associated with unloading.
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Affiliation(s)
- Tim Rolvien
- Division of Orthopaedics, Department of Trauma and Orthopaedic Surgery, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany.
| | - Michael Amling
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestrasse 59, 22529, Hamburg, Germany.
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10
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Choi JUA, Kijas AW, Lauko J, Rowan AE. The Mechanosensory Role of Osteocytes and Implications for Bone Health and Disease States. Front Cell Dev Biol 2022; 9:770143. [PMID: 35265628 PMCID: PMC8900535 DOI: 10.3389/fcell.2021.770143] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 12/13/2021] [Indexed: 12/14/2022] Open
Abstract
Bone homeostasis is a dynamic equilibrium between bone-forming osteoblasts and bone-resorbing osteoclasts. This process is primarily controlled by the most abundant and mechanosensitive bone cells, osteocytes, that reside individually, within chambers of porous hydroxyapatite bone matrix. Recent studies have unveiled additional functional roles for osteocytes in directly contributing to local matrix regulation as well as systemic roles through endocrine functions by communicating with distant organs such as the kidney. Osteocyte function is governed largely by both biochemical signaling and the mechanical stimuli exerted on bone. Mechanical stimulation is required to maintain bone health whilst aging and reduced level of loading are known to result in bone loss. To date, both in vivo and in vitro approaches have been established to answer important questions such as the effect of mechanical stimuli, the mechanosensors involved, and the mechanosensitive signaling pathways in osteocytes. However, our understanding of osteocyte mechanotransduction has been limited due to the technical challenges of working with these cells since they are individually embedded within the hard hydroxyapatite bone matrix. This review highlights the current knowledge of the osteocyte functional role in maintaining bone health and the key regulatory pathways of these mechanosensitive cells. Finally, we elaborate on the current therapeutic opportunities offered by existing treatments and the potential for targeting osteocyte-directed signaling.
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Affiliation(s)
- Jung Un Ally Choi
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD, Australia
| | - Amanda W Kijas
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD, Australia
| | - Jan Lauko
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD, Australia
| | - Alan E Rowan
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD, Australia
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11
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Lewis KJ. Osteocyte calcium signaling - A potential translator of mechanical load to mechanobiology. Bone 2021; 153:116136. [PMID: 34339908 DOI: 10.1016/j.bone.2021.116136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 06/25/2021] [Accepted: 07/27/2021] [Indexed: 10/20/2022]
Abstract
Osteocytes are embedded dendritic bone cells; by virtue of their position in bone tissue, ability to coordinate bone building osteoblasts and resorbing osteoclasts, and sensitivity to tissue level mechanical loading, they serve as the resident bone mechanosensor. The mechanisms osteocytes use to change mechanical loading into biological signals that drive tissue level changes has been well studied over the last 30 years, however the ways loading parameters are encoded at the cellular level are still not fully understood. Calcium signaling is a first messenger signal exhibited by osteocytes in response to mechanical forces. A body of work interrogating the mechanisms of osteocyte calcium signaling exists and is presently expanding, presenting the opportunity to better understand the relationship between calcium signaling characteristics and tuned osteocyte responses to tissue level strain features (e.g. magnitude, duration, frequency). This review covers the history of osteocyte load induced calcium signaling and highlights potential cellular mechanisms used by osteocytes to turn details about loading parameters into biological events.
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Affiliation(s)
- Karl J Lewis
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, United States of America.
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12
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Lewis KJ, Cabahug-Zuckerman P, Boorman-Padgett JF, Basta-Pljakic J, Louie J, Stephen S, Spray DC, Thi MM, Seref-Ferlengez Z, Majeska RJ, Weinbaum S, Schaffler MB. Estrogen depletion on In vivo osteocyte calcium signaling responses to mechanical loading. Bone 2021; 152:116072. [PMID: 34171514 PMCID: PMC8316427 DOI: 10.1016/j.bone.2021.116072] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 06/15/2021] [Accepted: 06/20/2021] [Indexed: 11/27/2022]
Abstract
Microstructural adaptation of bone in response to mechanical stimuli is diminished with estrogen deprivation. Here we tested in vivo whether ovariectomy (OVX) alters the acute response of osteocytes, the principal mechanosensory cells of bone, to mechanical loading in mice. We also used super resolution microscopy (Structured Illumination microscopy or SIM) in conjunction with immunohistochemistry to assess changes in the number and organization of "osteocyte mechanosomes" - complexes of Panx1 channels, P2X7 receptors and CaV3 voltage-gated Ca2+ channels clustered around αvβ3 integrin foci on osteocyte processes. Third metatarsals bones of mice expressing an osteocyte-targeted genetically encoded Ca2+ indicator (DMP1-GCaMP3) were cyclically loaded in vivo to strains from 250 to 3000 με and osteocyte intracellular Ca2+ signaling responses were assessed in mid-diaphyses using multiphoton microscopy. The number of Ca2+ signaling osteocytes in control mice increase monotonically with applied strain magnitude for the physiological range of strains. The relationship between the number of Ca2+ signaling osteocytes and loading was unchanged at 2 days post-OVX. However, it was altered markedly at 28 days post-OVX. At loads up to 1000 με, there was a dramatic reduction in number of responding (i.e. Ca2+ signaling) osteocytes; however, at higher strains the numbers of Ca2+ signaling osteocytes were similar to control mice. OVX significantly altered the abundance, make-up and organization of osteocyte mechanosome complexes on dendritic processes. Numbers of αvβ3 foci also staining with either Panx 1, P2X7R or CaV3 declined by nearly half after OVX, pointing to a loss of osteocyte mechanosomes on the dendritic processes with estrogen depletion. At the same time, the areas of the remaining foci that stained for αvβ3 and channel proteins increased significantly, a redistribution of mechanosome components suggesting a potential compensatory response. These results demonstrate that the deleterious effects of estrogen depletion on skeletal mechanical adaptation appear at the level of mechanosensation; osteocytes lose the ability to sense small (physiological) mechanical stimuli. This decline may result at least partly from changes in the structure and organization of osteocyte mechanosomes, which contribute to the distinctive sensitivity of osteocytes (particularly their dendritic processes) to mechanical stimulation.
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Affiliation(s)
- Karl J Lewis
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Pamela Cabahug-Zuckerman
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - James F Boorman-Padgett
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Jelena Basta-Pljakic
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Joyce Louie
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Samuel Stephen
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - David C Spray
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, United States of America
| | - Mia M Thi
- Orthopaedic Surgery, Albert Einstein College of Medicine, Bronx, NY, United States of America; Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, United States of America
| | - Zeynep Seref-Ferlengez
- Orthopaedic Surgery, Albert Einstein College of Medicine, Bronx, NY, United States of America
| | - Robert J Majeska
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Sheldon Weinbaum
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Mitchell B Schaffler
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America.
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13
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Luo Y, Li J, Li B, Xia Y, Wang H, Fu C. Physical Cues of Matrices Reeducate Nerve Cells. Front Cell Dev Biol 2021; 9:731170. [PMID: 34646825 PMCID: PMC8502847 DOI: 10.3389/fcell.2021.731170] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Accepted: 08/20/2021] [Indexed: 11/15/2022] Open
Abstract
The behavior of nerve cells plays a crucial role in nerve regeneration. The mechanical, topographical, and electrical microenvironment surrounding nerve cells can activate cellular signaling pathways of mechanical transduction to affect the behavior of nerve cells. Recently, biological scaffolds with various physical properties have been developed as extracellular matrix to regulate the behavior conversion of nerve cell, such as neuronal neurite growth and directional differentiation of neural stem cells, providing a robust driving force for nerve regeneration. This review mainly focused on the biological basis of nerve cells in mechanical transduction. In addition, we also highlighted the effect of the physical cues, including stiffness, mechanical tension, two-dimensional terrain, and electrical conductivity, on neurite outgrowth and differentiation of neural stem cells and predicted their potential application in clinical nerve tissue engineering.
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Affiliation(s)
- Yiqian Luo
- Department of Spine Surgery, The First Hospital of Jilin University, Changchun, China
| | - Jie Li
- Department of Spine Surgery, The First Hospital of Jilin University, Changchun, China
| | - Baoqin Li
- Department of Spine Surgery, The First Hospital of Jilin University, Changchun, China
| | - Yuanliang Xia
- Department of Spine Surgery, The First Hospital of Jilin University, Changchun, China
| | - Hengyi Wang
- Department of Spine Surgery, The First Hospital of Jilin University, Changchun, China
| | - Changfeng Fu
- Department of Spine Surgery, The First Hospital of Jilin University, Changchun, China
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14
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Yokoyama Y, Kameo Y, Kamioka H, Adachi T. High-resolution image-based simulation reveals membrane strain concentration on osteocyte processes caused by tethering elements. Biomech Model Mechanobiol 2021; 20:2353-2360. [PMID: 34471950 PMCID: PMC8595188 DOI: 10.1007/s10237-021-01511-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 08/13/2021] [Indexed: 11/08/2022]
Abstract
Osteocytes are vital for regulating bone remodeling by sensing the flow-induced mechanical stimuli applied to their cell processes. In this mechanosensing mechanism, tethering elements (TEs) connecting the osteocyte process with the canalicular wall potentially amplify the strain on the osteocyte processes. The ultrastructure of the osteocyte processes and canaliculi can be visualized at a nanometer scale using high-resolution imaging via ultra-high voltage electron microscopy (UHVEM). Moreover, the irregular shapes of the osteocyte processes and the canaliculi, including the TEs in the canalicular space, should considerably influence the mechanical stimuli applied to the osteocytes. This study aims to characterize the roles of the ultrastructure of osteocyte processes and canaliculi in the mechanism of osteocyte mechanosensing. Thus, we constructed a high-resolution image-based model of an osteocyte process and a canaliculus using UHVEM tomography and investigated the distribution and magnitude of flow-induced local strain on the osteocyte process by performing fluid–structure interaction simulation. The analysis results reveal that local strain concentration in the osteocyte process was induced by a small number of TEs with high tension, which were inclined depending on the irregular shapes of osteocyte processes and canaliculi. Therefore, this study could provide meaningful insights into the effect of ultrastructure of osteocyte processes and canaliculi on the osteocyte mechanosensing mechanism.
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Affiliation(s)
- Yuka Yokoyama
- Department of Micro Engineering, Graduate School of Engineering, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Yoshitaka Kameo
- Department of Micro Engineering, Graduate School of Engineering, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan.,Department of Biosystems Science, Institute for Frontier Life and Medical Sciences, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan.,Department of Mammalian Regulatory Network, Graduate School of Biostudies, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Hiroshi Kamioka
- Department of Orthodontics, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 2-5-1 Shikata-Cho, Kita-ku, Okayama, 700-8525, Japan
| | - Taiji Adachi
- Department of Micro Engineering, Graduate School of Engineering, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan. .,Department of Biosystems Science, Institute for Frontier Life and Medical Sciences, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan. .,Department of Mammalian Regulatory Network, Graduate School of Biostudies, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan.
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15
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Gould NR, Torre OM, Leser JM, Stains JP. The cytoskeleton and connected elements in bone cell mechano-transduction. Bone 2021; 149:115971. [PMID: 33892173 PMCID: PMC8217329 DOI: 10.1016/j.bone.2021.115971] [Citation(s) in RCA: 19] [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] [Received: 01/29/2021] [Revised: 03/30/2021] [Accepted: 04/17/2021] [Indexed: 02/07/2023]
Abstract
Bone is a mechano-responsive tissue that adapts to changes in its mechanical environment. Increases in strain lead to increased bone mass acquisition, whereas decreases in strain lead to a loss of bone mass. Given that mechanical stress is a regulator of bone mass and quality, it is important to understand how bone cells sense and transduce these mechanical cues into biological changes to identify druggable targets that can be exploited to restore bone cell mechano-sensitivity or to mimic mechanical load. Many studies have identified individual cytoskeletal components - microtubules, actin, and intermediate filaments - as mechano-sensors in bone. However, given the high interconnectedness and interaction between individual cytoskeletal components, and that they can assemble into multiple discreet cellular structures, it is likely that the cytoskeleton as a whole, rather than one specific component, is necessary for proper bone cell mechano-transduction. This review will examine the role of each cytoskeletal element in bone cell mechano-transduction and will present a unified view of how these elements interact and work together to create a mechano-sensor that is necessary to control bone formation following mechanical stress.
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Affiliation(s)
- Nicole R Gould
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Olivia M Torre
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Jenna M Leser
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Joseph P Stains
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD 21201, USA..
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16
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Gao Y, Patil S, Jia J. The Development of Molecular Biology of Osteoporosis. Int J Mol Sci 2021; 22:8182. [PMID: 34360948 PMCID: PMC8347149 DOI: 10.3390/ijms22158182] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Revised: 07/25/2021] [Accepted: 07/26/2021] [Indexed: 02/07/2023] Open
Abstract
Osteoporosis is one of the major bone disorders that affects both women and men, and causes bone deterioration and bone strength. Bone remodeling maintains bone mass and mineral homeostasis through the balanced action of osteoblasts and osteoclasts, which are responsible for bone formation and bone resorption, respectively. The imbalance in bone remodeling is known to be the main cause of osteoporosis. The imbalance can be the result of the action of various molecules produced by one bone cell that acts on other bone cells and influence cell activity. The understanding of the effect of these molecules on bone can help identify new targets and therapeutics to prevent and treat bone disorders. In this article, we have focused on molecules that are produced by osteoblasts, osteocytes, and osteoclasts and their mechanism of action on these cells. We have also summarized the different pharmacological osteoporosis treatments that target different molecular aspects of these bone cells to minimize osteoporosis.
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Affiliation(s)
- Yongguang Gao
- Tangshan Key Laboratory of Green Speciality Chemicals, Department of Chemistry, Tangshan Normal University, Tangshan 063000, China;
| | - Suryaji Patil
- Lab for Bone Metabolism, School of Life Sciences, Northwestern Polytechnical University, Xi’an 710072, China;
| | - Jingxian Jia
- Tangshan Key Laboratory of Green Speciality Chemicals, Department of Chemistry, Tangshan Normal University, Tangshan 063000, China;
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17
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Monteiro DA, Dole NS, Campos JL, Kaya S, Schurman CA, Belair CD, Alliston T. Fluid shear stress generates a unique signaling response by activating multiple TGFβ family type I receptors in osteocytes. FASEB J 2021; 35:e21263. [PMID: 33570811 PMCID: PMC7888383 DOI: 10.1096/fj.202001998r] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 11/11/2020] [Accepted: 11/25/2020] [Indexed: 12/18/2022]
Abstract
Bone is a dynamic tissue that constantly adapts to changing mechanical demands. The transforming growth factor beta (TGFβ) signaling pathway plays several important roles in maintaining skeletal homeostasis by both coupling the bone‐forming and bone‐resorbing activities of osteoblasts and osteoclasts and by playing a causal role in the anabolic response of bone to applied loads. However, the extent to which the TGFβ signaling pathway in osteocytes is directly regulated by fluid shear stress (FSS) is unknown, despite work suggesting that fluid flow along canaliculi is a dominant physical cue sensed by osteocytes following bone compression. To investigate the effects of FSS on TGFβ signaling in osteocytes, we stimulated osteocytic OCY454 cells cultured within a microfluidic platform with FSS. We find that FSS rapidly upregulates Smad2/3 phosphorylation and TGFβ target gene expression, even in the absence of added TGFβ. Indeed, relative to treatment with TGFβ, FSS induced a larger increase in levels of pSmad2/3 and Serpine1 that persisted even in the presence of a TGFβ receptor type I inhibitor. Our results show that FSS stimulation rapidly induces phosphorylation of multiple TGFβ family R‐Smads by stimulating multimerization and concurrently activating several TGFβ and BMP type I receptors, in a manner that requires the activity of the corresponding ligand. While the individual roles of the TGFβ and BMP signaling pathways in bone mechanotransduction remain unclear, these results implicate that FSS activates both pathways to generate a downstream response that differs from that achieved by either ligand alone.
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Affiliation(s)
- David A Monteiro
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA.,UC Berkeley-UCSF Graduate Program in Bioengineering, San Francisco, CA, USA
| | - Neha S Dole
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - J Luke Campos
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Serra Kaya
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA
| | - Charles A Schurman
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA.,UC Berkeley-UCSF Graduate Program in Bioengineering, San Francisco, CA, USA
| | - Cassandra D Belair
- The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, CA, USA.,Department of Urology, University of California, San Francisco, CA, USA
| | - Tamara Alliston
- Department of Orthopaedic Surgery, University of California, San Francisco, CA, USA.,UC Berkeley-UCSF Graduate Program in Bioengineering, San Francisco, CA, USA.,The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, CA, USA
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18
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Li MCM, Chow SKH, Wong RMY, Qin L, Cheung WH. The role of osteocytes-specific molecular mechanism in regulation of mechanotransduction - A systematic review. J Orthop Translat 2021; 29:1-9. [PMID: 34036041 PMCID: PMC8138679 DOI: 10.1016/j.jot.2021.04.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 03/15/2021] [Accepted: 04/11/2021] [Indexed: 11/29/2022] Open
Abstract
Background Osteocytes, composing over 90% of bone cells, are well known for their mechanosensing abilities. Aged osteocytes with impaired morphology and function are less efficient in mechanotransduction which will disrupt bone turnover leading to osteoporosis. The aim of this systematic review is to delineate the mechanotransduction mechanism at different stages in order to explore potential target for therapeutic drugs. Methods A systematic literature search was performed in PubMed and Web of Science. Original animal, cell and clinical studies with available English full-text were included. Information was extracted from the included studies for review. Results The 26 studies included in this review provided evidence that mechanical loading are sensed by osteocytes via various sensing proteins and transduced to different signaling molecules which later initiate various biochemical responses. Studies have shown that osteocyte plasma membrane and cytoskeletons are emerging key players in initiating mechanotransduction. Bone regulating genes expressions are altered in response to load sensed by osteocytes, but the genes involved different signaling pathways and the spatiotemporal expression pattern had made mechanotransduction mechanism complicated. Most of the included studies described the important role of osteocytes in pathways that regulate mechanosensing and bone remodeling. Conclusions This systematic review provides an up-to-date insight to different steps of mechanotransduction. A better understanding of the mechanotransduction mechanism is beneficial in search of new potential treatment for osteoporotic patients. By delineating the unique morphology of osteocytes and their interconnected signaling network new targets can be discovered for drug development. Translational potential of this article This systematic review provides an up-to-date sequential overview and highlights the different osteocyte-related pathways and signaling molecules during mechanotransduction. This allows a better understanding of mechanotransduction for future development of new therapeutic interventions to treat patients with impaired mechanosensitivity.
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Affiliation(s)
- Meng Chen Michelle Li
- Musculoskeletal Research Laboratory, Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Hong Kong, China
| | - Simon Kwoon Ho Chow
- Musculoskeletal Research Laboratory, Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Hong Kong, China
- The CUHK-ACC Space Medicine Centre on Health Maintenance of Musculoskeletal System, The Chinese University of Hong Kong Shenzhen Research Institute, Shenzhen, PR China
| | - Ronald Man Yeung Wong
- Musculoskeletal Research Laboratory, Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Hong Kong, China
| | - Ling Qin
- Musculoskeletal Research Laboratory, Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Hong Kong, China
| | - Wing Hoi Cheung
- Musculoskeletal Research Laboratory, Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Hong Kong, China
- The CUHK-ACC Space Medicine Centre on Health Maintenance of Musculoskeletal System, The Chinese University of Hong Kong Shenzhen Research Institute, Shenzhen, PR China
- Corresponding author.Department of Orthopaedics and Traumatology, 5/F, Clinical Sciences Building, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
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19
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Kong Q, Quan Y, Tian G, Zhou J, Liu X. Purinergic P2 Receptors: Novel Mediators of Mechanotransduction. Front Pharmacol 2021; 12:671809. [PMID: 34025431 PMCID: PMC8138185 DOI: 10.3389/fphar.2021.671809] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 04/26/2021] [Indexed: 02/05/2023] Open
Abstract
Mechanosensing and mechanotransduction are vital processes in mechanobiology and play critical roles in regulating cellular behavior and fate. There is increasing evidence that purinergic P2 receptors, members of the purinergic family, play a crucial role in cellular mechanotransduction. Thus, information on the specific mechanism of P2 receptor-mediated mechanotransduction would be valuable. In this review, we focus on purinergic P2 receptor signaling pathways and describe in detail the interaction of P2 receptors with other mechanosensitive molecules, including transient receptor potential channels, integrins, caveolae-associated proteins and hemichannels. In addition, we review the activation of purinergic P2 receptors and the role of various P2 receptors in the regulation of various pathophysiological processes induced by mechanical stimuli.
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Affiliation(s)
- Qihang Kong
- Laboratory of Cardiovascular Diseases, Regenerative Medicine Research Center, West China Hospital, Sichuan University, Chengdu, China
| | - Yue Quan
- Laboratory of Cardiovascular Diseases, Regenerative Medicine Research Center, West China Hospital, Sichuan University, Chengdu, China
| | - Geer Tian
- Laboratory of Cardiovascular Diseases, Regenerative Medicine Research Center, West China Hospital, Sichuan University, Chengdu, China
| | - Junteng Zhou
- Department of Cardiology, West China Hospital, Sichuan University, Chengdu, China
| | - Xiaojing Liu
- Laboratory of Cardiovascular Diseases, Regenerative Medicine Research Center, West China Hospital, Sichuan University, Chengdu, China.,Department of Cardiology, West China Hospital, Sichuan University, Chengdu, China
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20
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Abstract
PURPOSE OF REVIEW Skeletal adaptation to mechanical loading plays a critical role in bone growth and the maintenance of bone homeostasis. Osteocytes are postulated to serve as a hub orchestrating bone remodeling. The recent findings on the molecular mechanisms by which osteocytes sense mechanical loads and the downstream bone-forming factors are reviewed. RECENT FINDINGS Calcium channels have been implicated in mechanotransduction in bone cells for a long time. Efforts have been made to identify a specific calcium channel mediating the skeletal response to mechanical loads. Recent studies have revealed that Piezo1, a mechanosensitive ion channel, is critical for normal bone growth and is essential for the skeletal response to mechanical loading. Identification of mechanosensors and their downstream effectors in mechanosensing bone cells is essential for new strategies to modulate regenerative responses and develop therapies to treat the bone loss related to disuse or advanced age.
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Affiliation(s)
- Xuehua Li
- Department of Orthopaedic Surgery, Center for Musculoskeletal Disease Research, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Jacob Kordsmeier
- Department of Orthopaedic Surgery, Center for Musculoskeletal Disease Research, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Jinhu Xiong
- Department of Orthopaedic Surgery, Center for Musculoskeletal Disease Research, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
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21
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Large magnitude of force leads to NO-mediated cell shrinkage in single osteocytes implying an initial apoptotic response. J Biomech 2021; 117:110245. [PMID: 33493709 DOI: 10.1016/j.jbiomech.2021.110245] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 11/06/2020] [Accepted: 01/03/2021] [Indexed: 11/22/2022]
Abstract
Damage accumulation in the bone under continuous daily loading causes local mechanical overloading known to induce osteocyte apoptosis, which promotes bone resorption to repair bone damage. However, only a few studies have investigated the mechanism of apoptosis in mechanically overloaded osteocytes. As mechanically stimulated osteocytes produce nitric oxide (NO), which triggers apoptosis in various cell types, we aimed to elucidate the mechanism underlying apoptosis in mechanically overloaded osteocytes, focusing on intracellular NO. To investigate the effects of force magnitude on apoptosis and intracellular NO production, we isolated osteocytes from DMP1-EGFP mice and subjected them to quantitative local forces via fibronectin-coated micro beads targeting integrin on the cell surface using a magnetic tweezer. Cell shrinkage was microscopically examined, and intracellular NO production was visualized using DAR-4 M. Mechanical stimulation revealed relationships between force magnitude, apoptosis, and intracellular NO production. The application of a smaller force resulted in no significant cell shrinkage or intracellular NO production; however, a larger force caused a rapid increase in intracellular NO production followed by cell shrinkage. Besides, intracellular NOS (NO synthase) inhibition and NO donation revealed the pro-apoptotic roles of NO in osteocytes. L-NAME (NOS inhibitor)-treated cells displayed no significant shrinkage under a larger force, whereas SNP (NO donor)-treated cells showed cell shrinkage and Annexin V fluorescence, indicating apoptosis. Collectively, our study demonstrates that larger force leads to NO production-mediated osteocyte shrinkage, implying an initial apoptotic response and highlighting the importance of NO production in bone damage.
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22
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Chang B, Ma C, Liu X. Nanofibrous Tubular Three-Dimensional Platform for Single Dental Pulp Stem Cell Polarization. ACS APPLIED MATERIALS & INTERFACES 2020; 12:54481-54488. [PMID: 33252216 PMCID: PMC8025693 DOI: 10.1021/acsami.0c17730] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Dental pulp stem cells (DPSCs) are the primary stem cell source for regenerative endodontics. DPSCs need to undergo a polarization process and retain the permanent polarization status to perform the function of odontoblasts. However, the factors that control DPSC polarization and its underlying mechanism remain unknown. In this study, we established a unique nanofibrous tubular three-dimensional (3D) platform to explore DPSC polarization. The 3D platform has a "clean" background and confines one single DPSC in each microisland of the platform; therefore, it is capable of deciphering any signal that initiates or regulates DPSC polarization. Using the biomimetic platform, we identified that the nanofibrous tubular architecture is the crucial factor to initiate DPSC polarization. Dynamic morphological observation showed that the cellular process of the polarized DPSCs continuously extended and reached a plateau at 72 h. Meanwhile, Golgi apparatus, a cell polarization marker, continuously moved from a juxtanuclear region, passed the nucleus, and eventually settled down at a final position that was a few micrometers away from the nucleus. Inhibition of microfilament and microtubule polymerization demonstrated the indispensable role of cytoskeleton reorganization in modulating DPSC polarization. In addition, cell tension was involved in the regulation of DPSC polarization. The findings of this work expand the in-depth understanding of DPSC polarization, which helps design new bioinspired materials for regenerative endodontics.
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Affiliation(s)
- Bei Chang
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas 75246, United States
| | - Chi Ma
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas 75246, United States
| | - Xiaohua Liu
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas 75246, United States
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23
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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)
| | | | | | | | - 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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24
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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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25
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Yan Y, Wang L, Ge L, Pathak JL. Osteocyte-Mediated Translation of Mechanical Stimuli to Cellular Signaling and Its Role in Bone and Non-bone-Related Clinical Complications. Curr Osteoporos Rep 2020; 18:67-80. [PMID: 31953640 DOI: 10.1007/s11914-020-00564-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
PURPOSE OF REVIEW Osteocytes comprise > 95% of the cellular component in bone tissue and produce a wide range of cytokines and cellular signaling molecules in response to mechanical stimuli. In this review, we aimed to summarize the molecular mechanisms involved in the osteocyte-mediated translation of mechanical stimuli to cellular signaling, and discuss their role in skeletal (bone) diseases and extra-skeletal (non-bone) clinical complications. RECENT FINDINGS Two decades before, osteocytes were assumed as a dormant cells buried in bone matrix. In recent years, emerging evidences have shown that osteocytes are pivotal not only for bone homeostasis but also for vital organ functions such as muscle, kidney, and heart. Osteocyte mechanotransduction regulates osteoblast and osteoclast function and maintains bone homeostasis. Mechanical stimuli modulate the release of osteocyte-derived cytokines, signaling molecules, and extracellular cellular vesicles that regulate not only the surrounding bone cell function and bone homeostasis but also the distant organ function in a paracrine and endocrine fashion. Mechanical loading and unloading modulate the osteocytic release of NO, PGE2, and ATPs that regulates multiple cellular signaling such as Wnt/β-catenin, RANKL/OPG, BMPs, PTH, IGF1, VEGF, sclerostin, and others. Therefore, the in-depth study of the molecular mechanism of osteocyte mechanotransduction could unravel therapeutic targets for various bone and non-bone-related clinical complications such as osteoporosis, sarcopenia, and cancer metastasis to bone.
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Affiliation(s)
- Yongyong Yan
- Key Laboratory of Oral Medicine, Guangzhou Institute of Oral Disease, Affiliated Stomatology Hospital of Guangzhou Medical University, Guangzhou, 510140, China
| | - Liping Wang
- Key Laboratory of Oral Medicine, Guangzhou Institute of Oral Disease, Affiliated Stomatology Hospital of Guangzhou Medical University, Guangzhou, 510140, China
| | - Linhu Ge
- Key Laboratory of Oral Medicine, Guangzhou Institute of Oral Disease, Affiliated Stomatology Hospital of Guangzhou Medical University, Guangzhou, 510140, China.
| | - Janak L Pathak
- Key Laboratory of Oral Medicine, Guangzhou Institute of Oral Disease, Affiliated Stomatology Hospital of Guangzhou Medical University, Guangzhou, 510140, China.
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26
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Creecy A, Damrath JG, Wallace JM. Control of Bone Matrix Properties by Osteocytes. Front Endocrinol (Lausanne) 2020; 11:578477. [PMID: 33537002 PMCID: PMC7848033 DOI: 10.3389/fendo.2020.578477] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 12/01/2020] [Indexed: 12/13/2022] Open
Abstract
Osteocytes make up 90-95% of the cellular content of bone and form a rich dendritic network with a vastly greater surface area than either osteoblasts or osteoclasts. Osteocytes are well positioned to play a role in bone homeostasis by interacting directly with the matrix; however, the ability for these cells to modify bone matrix remains incompletely understood. With techniques for examining the nano- and microstructure of bone matrix components including hydroxyapatite and type I collagen becoming more widespread, there is great potential to uncover novel roles for the osteocyte in maintaining bone quality. In this review, we begin with an overview of osteocyte biology and the lacunar-canalicular system. Next, we describe recent findings from in vitro models of osteocytes, focusing on the transitions in cellular phenotype as they mature. Finally, we describe historical and current research on matrix alteration by osteocytes in vivo, focusing on the exciting potential for osteocytes to directly form, degrade, and modify the mineral and collagen in their surrounding matrix.
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Affiliation(s)
- Amy Creecy
- Department of Biomedical Engineering, Indiana University-Purdue University at Indianapolis, Indianapolis, IN, United States
| | - John G. Damrath
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, United States
| | - Joseph M. Wallace
- Department of Biomedical Engineering, Indiana University-Purdue University at Indianapolis, Indianapolis, IN, United States
- *Correspondence: Joseph M. Wallace,
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27
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Liu X, Tang C, Zhang X, Cai J, Yan Z, Xie K, Yang Z, Wang J, Guo XE, Luo E, Jing D. Spatiotemporal Distribution of Linear Microcracks and Diffuse Microdamage Following Daily Bouts of Fatigue Loading of Rat Ulnae. J Orthop Res 2019; 37:2112-2121. [PMID: 31206769 DOI: 10.1002/jor.24391] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Accepted: 06/06/2019] [Indexed: 02/04/2023]
Abstract
Microdamage accumulation contributes to impaired skeletal mechanical integrity. The bone can remove microdamage by initiating targeted bone remodeling. However, the spatiotemporal characteristics of microdamage initiation and propagation and their relationship with bone remodeling in response to fatigue loading, especially for more physiologically relevant daily bouts of compressive loading, remain poorly understood. The right forelimbs of 24 rats were cyclically loaded with a ramp waveform for 1,500 cycles/day, and contralateral ulnae were not loaded as the controls. The rats were divided into four equal groups and loaded for 1, 4, 7, and 10 days, respectively. We demonstrated that linear microcracking accumulation exhibited a non-linear time-varying process within 10 days of loading with peaked microcrack density at Day 7. Disrupted canaliculi surrounding linear microcracks showed high similarity with the temporal changes of linear microcracking accumulation. Observable intracortical resorption regions were found on Day 10. We found more linear microcracks accumulated in the tensile cortex, but longer cracks were observed in the compressive sides. Increased accumulation of diffuse microdamage was observed from Day 4, but no obvious peak was observed within the 10-day loading period. Diffuse damage first initiated in the compressive cortices but extended to tension from Day 7. The diffuse damage exhibited no impacts on the surrounding osteocyte integrity. Together, our findings revealed a time-dependent, bone remodeling-mediated varying process of linear microcracking accumulation following daily bouts of fatigue loading (with observable peak at Day 7 under our loading regime). Our study also identified distinct spatial accumulation of linear and diffuse microdamage in rat ulnae with tensile and compressive strains. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2112-2121, 2019.
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Affiliation(s)
- Xiyu Liu
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China
| | - Chi Tang
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China
| | - Xuhui Zhang
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China.,Department of Medical Engineering, 456th Hospital of Chinese People's Liberation Army, Jinan, China
| | - Jing Cai
- Department of Diagnostics, College of Basic Medicine, Shaanxi University of Chinese Medicine, Xianyang, China
| | - Zedong Yan
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China
| | - Kangning Xie
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China
| | - Zhiping Yang
- Department of Nuclear Medicine, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Jing Wang
- Department of Nuclear Medicine, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - X Edward Guo
- Department of Biomedical Engineering, Bone Bioengineering Laboratory, Columbia University, New York, New York
| | - Erping Luo
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China
| | - Da Jing
- Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, China
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Abstract
PURPOSE OF REVIEW Osteocytes are the main mechanosensitive cells in bone. Integrin-based adhesions have been shown to facilitate mechanotransduction, and therefore play an important role in load-induced bone formation. This review outlines the role of integrins in osteocyte function (cell adhesion, signalling, and mechanotransduction) and possible role in disease. RECENT FINDINGS Both β1 and β3 integrins subunits have been shown to be required for osteocyte mechanotransduction. Antagonism of these integrin subunits in osteocytes resulted in impaired responses to fluid shear stress. Various disease states (osteoporosis, osteoarthritis, bone metastases) have been shown to result in altered integrin expression and function. Osteocyte integrins are required for normal cell function, with dysregulation of integrins seen in disease. Understanding the mechanism of faulty integrins in disease may aid in the creation of novel therapeutic approaches.
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Affiliation(s)
- Ivor P Geoghegan
- Department of Mechanical and Biomedical Engineering, Mechanobiology and Medical Device Research Group (MMDRG), Biomedical Engineering, National University of Ireland, Galway, Ireland
- Centre for Research in Medical Devices (CÚRAM), National University of Ireland, Galway, Ireland
| | - David A Hoey
- Centre for Research in Medical Devices (CÚRAM), National University of Ireland, Galway, Ireland
- Trinity Centre for Bioengineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland
- Department of Mechanical and Manufacturing Engineering, School of Engineering, Trinity College Dublin, Dublin 2, Ireland
- Advanced Materials and Bioengineering Research Centre, Trinity College Dublin & RCSI, Dublin 2, Ireland
| | - Laoise M McNamara
- Department of Mechanical and Biomedical Engineering, Mechanobiology and Medical Device Research Group (MMDRG), Biomedical Engineering, National University of Ireland, Galway, Ireland.
- Centre for Research in Medical Devices (CÚRAM), National University of Ireland, Galway, Ireland.
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29
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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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30
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Hinton PV, Rackard SM, Kennedy OD. In Vivo Osteocyte Mechanotransduction: Recent Developments and Future Directions. Curr Osteoporos Rep 2018; 16:746-753. [PMID: 30406580 DOI: 10.1007/s11914-018-0485-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
PURPOSE OF REVIEW Mechanical loading is an essential stimulus for skeletal tissues. Osteocytes are primarily responsible for sensing mechanical stimuli in bone and for orchestrating subsequent responses. This is critical for maintaining homeostasis, and responding to injury/disease. The osteocyte mechanotransduction pathway, and the downstream effects it mediates, is highly complex. In vivo models have proved invaluable in understanding this process. This review summarizes the commonly used models, as well as more recently developed ones, and describes how they are used to address emerging questions in the field. RECENT FINDINGS Minimally invasive animal models can be used to determine mechanisms of osteocyte mechanotransduction, at the cell and molecular level, while simultaneously reducing potentially confounding responses such as inflammation/wound-healing. The details of osteocyte mechanotransduction in bone are gradually becoming clearer. In vivo model systems are a key tool in pursing this question. Advances in this field are explored and discussed in this review.
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Affiliation(s)
- Paige V Hinton
- Department of Anatomy & Tissue Engineering Research Group, Royal College of Surgeons in Ireland, 123 St Stephens Green, Dublin 2, Ireland
| | - Susan M Rackard
- School of Veterinary Medicine, Veterinary Science Centre, University College Dublin, Dublin 4, Ireland
| | - Oran D Kennedy
- Department of Anatomy & Tissue Engineering Research Group, Royal College of Surgeons in Ireland, 123 St Stephens Green, Dublin 2, Ireland.
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31
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Seref-Ferlengez Z, Urban-Maldonado M, Sun HB, Schaffler MB, Suadicani SO, Thi MM. Role of pannexin 1 channels in load-induced skeletal response. Ann N Y Acad Sci 2018; 1442:79-90. [PMID: 29952014 DOI: 10.1111/nyas.13914] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 05/18/2018] [Accepted: 06/01/2018] [Indexed: 12/31/2022]
Abstract
The pannexin 1 (Panx1) channel is a mechanosensitive channel that interacts with P2X7 receptors (P2X7R) to form a functional complex that has been shown in vitro to play an essential role in osteocyte mechanosignaling. While the participation of P2X7R in skeletal responses to mechanical loading has been demonstrated, the role of Panx1 and its interplay with P2X7R still remain to be determined. In this study, we use a global Panx1-/- mouse model and in vivo mechanical loading to demonstrate that Panx1 channels play an essential role in load-induced skeletal responses. We found that absence of Panx1 not only disrupts the P2X7R-Panx1 signaling complex, but also alters load-induced regulation of P2X7R expression. Moreover, lack of Panx1 completely abolished load-induced periosteal bone formation. Load-induced regulation of β-catenin and sclerostin expression was dysregulated in Panx1-/- , compared to wild-type, bone. This finding suggests that Panx1 deficiency disrupts Wnt/β-catenin signaling by lowering β-catenin while favoring inhibition of bone formation by increasing load-induced sclerostin expression. This study demonstrates the existence of a Panx1-dependent mechanosensitive mechanism that not only modulates ATP signaling but also coordinates Wnt/β-catenin signaling that is essential for proper skeletal response to mechanical loading.
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Affiliation(s)
- Zeynep Seref-Ferlengez
- Department of Orthopaedic Surgery.,Laboratories of Musculoskeletal Orthopedic Research at Einstein-Montefiore (MORE)
| | - Marcia Urban-Maldonado
- Department of Orthopaedic Surgery.,Laboratories of Musculoskeletal Orthopedic Research at Einstein-Montefiore (MORE).,Department of Urology
| | - Hui B Sun
- Department of Orthopaedic Surgery.,Laboratories of Musculoskeletal Orthopedic Research at Einstein-Montefiore (MORE).,Department of Radiation Oncology
| | - Mitchell B Schaffler
- Department of Biomedical Engineering, City College of New York, New York, New York
| | - Sylvia O Suadicani
- Laboratories of Musculoskeletal Orthopedic Research at Einstein-Montefiore (MORE).,Department of Urology.,Department of Neuroscience, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, New York
| | - Mia M Thi
- Department of Orthopaedic Surgery.,Laboratories of Musculoskeletal Orthopedic Research at Einstein-Montefiore (MORE).,Department of Neuroscience, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, New York
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32
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Guo XE, Hung CT, Sandell LJ, Silva MJ. Musculoskeletal mechanobiology: A new era for MechanoMedicine. J Orthop Res 2018; 36:531-532. [PMID: 29409134 DOI: 10.1002/jor.23789] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- X Edward Guo
- Department of Biomedical Engineering, Columbia University, 1210 Amsterdam Avenue, New York, NY 10027
| | - Clark T Hung
- Department of Biomedical Engineering, Columbia University, 1210 Amsterdam Avenue, New York, NY 10027
| | - Linda J Sandell
- Department of Orthopaedic Surgery, Washington University School of Medicine, 660 S. Euclid Avenue, St. Louis, MO 63110
| | - Matthew J Silva
- Department of Orthopaedic Surgery, Washington University School of Medicine, 660 S. Euclid Avenue, St. Louis, MO 63110
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