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Hua R, Truong VA, Fajardo RJ, Guda T, Gu S, Jiang JX. Connexin hemichannels drive lactation-induced osteocyte acidification and perilacunar-canalicular remodeling. Cell Rep 2024; 43:114363. [PMID: 38935505 DOI: 10.1016/j.celrep.2024.114363] [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: 11/09/2023] [Revised: 04/30/2024] [Accepted: 05/31/2024] [Indexed: 06/29/2024] Open
Abstract
The maternal skeleton experiences significant bone loss during lactation, followed by rapid restoration post weaning. Parathyroid-related protein (PTHrP)-induced acidification of the perilacunar matrix by osteocytes is crucial in this process, yet its mechanism remains unclear. Here, we identify Cx43 hemichannels (HCs) as key mediators of osteocyte acidification and perilacunar-canalicular remodeling (PLR). Utilizing transgenic mouse models expressing dominant-negative Cx43 mutants, we show that mice with impaired Cx43 HCs exhibit attenuated lactation-induced responses compared to wild-type and only gap junction-impaired groups, including lacunar enlargement, upregulation of PLR genes, and bone loss with compromised mechanical properties. Furthermore, inhibition of HCs by a Cx43 antibody blunts PTHrP-induced calcium influx and protein kinase A activation, followed by impaired osteocyte acidification. Additionally, impeded HCs suppress bone recovery during the post-lactation period. Our findings highlight the pivotal role of Cx43 HCs in orchestrating dynamic bone changes during lactation and recovery by regulating acidification and remodeling enzyme expression.
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Affiliation(s)
- Rui Hua
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Vu A Truong
- School of Osteopathic Medicine, University of the Incarnate Word, San Antonio, TX 78209, USA
| | - Roberto J Fajardo
- School of Osteopathic Medicine, University of the Incarnate Word, San Antonio, TX 78209, USA
| | - Teja Guda
- Department of Biomedical Engineering and Chemical Engineering, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - Sumin Gu
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Jean X Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
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2
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Peres C, Mammano F. A Protocol for the Automated Assessment of Cutaneous Pathology in a Mouse Model of Hemichannel Dysfunction. Methods Mol Biol 2024; 2801:177-187. [PMID: 38578421 DOI: 10.1007/978-1-0716-3842-2_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/06/2024]
Abstract
In this chapter, we provide detailed instructions to perform quantitative reflectance imaging in a mouse model of a rare epidermal disorder caused by hyperactive connexin 26 hemichannels. Reflectance imaging is a versatile and powerful tool in dermatology, offering noninvasive, high-resolution insights into skin pathology, which is essential for both clinical practice and research. This approach offers several advantages and applications. Unlike traditional biopsy, reflectance imaging is noninvasive, allowing for real-time, in vivo examination of the skin. This is particularly valuable for monitoring chronic conditions or assessing the efficacy of treatments over time, enabling the detailed examination of skin morphology. This is crucial for identifying features of skin diseases such as cancers, inflammatory conditions, and infections. In therapeutic applications, reflectance imaging can be used to monitor the response of skin lesions to treatments. It can help in identifying the most representative area of a lesion for biopsy, thereby increasing the diagnostic accuracy. Reflectance imaging can also be used to diagnose and monitor inflammatory skin diseases, like psoriasis and eczema, by visualizing changes in skin structure and cellular infiltration. As the technology becomes more accessible, it has potential in telemedicine, allowing for remote diagnosis and monitoring of skin conditions. In academic settings, reflectance imaging can be a powerful research tool, enabling the study of skin pathology and the effects of novel treatments, including the development of monoclonal antibodies for therapeutic applications.
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Affiliation(s)
- Chiara Peres
- Institute of Biochemistry and Cell Biology, Italian National Research Council, Rome, Italy
- , Bologna, Italy
| | - Fabio Mammano
- Institute of Biochemistry and Cell Biology, Italian National Research Council, Rome, Italy.
- Department of Physics and Astronomy "G. Galilei", University of Padova, Padova, Italy.
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3
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Acosta FM, Riquelme MA, Gu S, Jiang JX. Evaluation of Connexin Hemichannel Activity In Vivo. Methods Mol Biol 2024; 2801:111-124. [PMID: 38578417 DOI: 10.1007/978-1-0716-3842-2_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/06/2024]
Abstract
Connexin hemichannels (Cx HCs) are hexameric structures at the cell plasma membrane, whose function as membrane transport proteins allows for the passive flow of small hydrophilic molecules and ions (≤1 kDa) between the cytosol and the extracellular environment. Activation of Cx HCs is highly dependent on pathological conditions. HC activity provokes changes in the microenvironment, inducing the dissemination of signaling molecules in both an autocrine and paracrine manner. Given the elicitation of a variety of signaling pathways, and assortment of Cx species and dispersion throughout the body, Cx HCs have been implicated in a range of processes such as cell proliferation, differentiation, cell death, and tissue modeling and remodeling. While studying the expression and localization of Cx HCs can be done using traditional laboratory techniques, such as immunoblot analysis, measuring the functionality/activity of the HCs requires a more explicit methodology and is essential for determining Cx-mediated physiological changes. The study of Cx HC function/activity has focused mainly on in vitro measurements through electrophysiological characterization or, more commonly, using HC-permeable dye uptake studies. Here, we describe the use of dye uptake to measure Cx HC activity in vivo using mechanically stimulated osteocytic Cx43 HCs with Evans blue dye as our model.
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Affiliation(s)
- Francisca M Acosta
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Manuel A Riquelme
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Sumin Gu
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Jean X Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
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4
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Li Y, Acosta FM, Jiang JX. Gap Junctions or Hemichannel-Dependent and Independent Roles of Connexins in Fibrosis, Epithelial-Mesenchymal Transitions, and Wound Healing. Biomolecules 2023; 13:1796. [PMID: 38136665 PMCID: PMC10742173 DOI: 10.3390/biom13121796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 12/09/2023] [Accepted: 12/12/2023] [Indexed: 12/24/2023] Open
Abstract
Fibrosis initially appears as a normal response to damage, where activated fibroblasts produce large amounts of the extracellular matrix (ECM) during the wound healing process to assist in the repair of injured tissue. However, the excessive accumulation of the ECM, unresolved by remodeling mechanisms, leads to organ dysfunction. Connexins, a family of transmembrane channel proteins, are widely recognized for their major roles in fibrosis, the epithelial-mesenchymal transition (EMT), and wound healing. Efforts have been made in recent years to identify novel mediators and targets for this regulation. Connexins form gap junctions and hemichannels, mediating communications between neighboring cells and inside and outside of cells, respectively. Recent evidence suggests that connexins, beyond forming channels, possess channel-independent functions in fibrosis, the EMT, and wound healing. One crucial channel-independent function is their role as the primary functional component for cell adhesion. Other channel-independent functions of connexins involve their roles in mitochondria and exosomes. This review summarizes the latest advances in the channel-dependent and independent roles of connexins in fibrosis, the EMT, and wound healing, with a particular focus on eye diseases, emphasizing their potential as novel, promising therapeutic targets.
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Affiliation(s)
- Yuting Li
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA; (Y.L.); (F.M.A.)
- Department of Pathology, Basic Medical School, Ningxia Medical University, Yinchuan 750004, China
| | - Francisca M. Acosta
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA; (Y.L.); (F.M.A.)
| | - Jean X. Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA; (Y.L.); (F.M.A.)
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5
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Plotkin LI, Asad I, Kritikos AE, Sanz N. Role of Cx43 on the Bone Cell Generation, Function, and Survival. Bioelectricity 2023; 5:188-195. [PMID: 37746312 PMCID: PMC10517329 DOI: 10.1089/bioe.2023.0028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/26/2023] Open
Abstract
The presence of gap junction intercellular communication structures in bone cells has been known since the early 1970s, further confirmed by Doty and Marotti at the structural level in the 1980-1990s. Work by Civitelli, Donahue, and others showed the expression of Cx43 at the mRNA and protein levels in all bone cell types: osteoclasts (bone resorbing cells), osteoblasts (bone forming cells), and osteocytes (mature osteoblasts embedded in the bone matrix that regulate the function of both osteoclasts and osteoblasts). While Cx45, Cx46, and Cx37 were also shown to be expressed in bone cells, most studies have focused on Cx43, the most abundant member of the connexin (Cx) family of proteins expressed in bone. The role of Cx43 has been shown to be related to the formation of gap junction intercellular channels, to unopposed hemichannels, and to channel independent functions of the molecule. Cx43 participates in the response of bone cells to pharmacological, hormonal, and mechanical stimuli, and it is involved in the skeletal phenotype with old age. Human and murine studies have shown that mutations of Cx43 lead to oculodentodigital dysplasia and craniometaphyseal dysplasia, both conditions associated with abnormalities in the skeleton. However, whereas substantial advances have been made on the skeletal role of Cx43, further research is needed to understand the basis for the effects of mutated Cx43 and potential ways to prevent the effects of these mutations on bone.
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Affiliation(s)
- Lilian I. Plotkin
- Department of Anatomy, Cell Biology & Physiology, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Roudebush Veterans Administration Medical Center, Indianapolis, Indiana, USA
- Indiana Center for Musculoskeletal Health, Indianapolis, Indiana, USA
| | - Iqra Asad
- Department of Anatomy, Cell Biology & Physiology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Alex E. Kritikos
- Department of Anatomy, Cell Biology & Physiology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Natasha Sanz
- Department of Anatomy, Cell Biology & Physiology, Indiana University School of Medicine, Indianapolis, Indiana, USA
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Chai H, Huang Q, Jiao Z, Wang S, Sun C, Geng D, Xu W. Osteocytes Exposed to Titanium Particles Inhibit Osteoblastic Cell Differentiation via Connexin 43. Int J Mol Sci 2023; 24:10864. [PMID: 37446062 DOI: 10.3390/ijms241310864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2023] [Revised: 06/24/2023] [Accepted: 06/27/2023] [Indexed: 07/15/2023] Open
Abstract
Periprosthetic osteolysis (PPO) induced by wear particles is the most severe complication of total joint replacement; however, the mechanism behind PPO remains elusive. Previous studies have shown that osteocytes play important roles in wear-particle-induced osteolysis. In this study, we investigated the effects of connexin 43 (Cx43) on the regulation of osteocyte-to-osteoblast differentiation. We established an in vivo murine model of calvarial osteolysis induced by titanium (Ti) particles. The osteolysis characteristic and osteogenesis markers in the osteocyte-selective Cx43 (CKO)-deficient and wild-type (WT) mice were observed. The calvarial osteolysis induced by Ti particles was partially attenuated in CKO mice. The expression of β-catenin and osteogenesis markers increased significantly in CKO mice. In vitro, the osteocytic cell line MLO-Y4 was treated with Ti particles. The co-culturing of MLO-Y4 cells with MC3T3-E1 osteoblastic cells was used to observe the effects of Ti-treated osteocytes on osteoblast differentiation. When Cx43 of MLO-Y4 cells was silenced or overexpressed, β-catenin was detected. Additionally, co-immunoprecipitation detection of Cx43 and β-catenin binding in MLO-Y4 cells and MC3T3-E1 cells was performed. Finally, β-catenin expression in MC3T3-E1 cells and osteoblast differentiation were evaluated after 18α-glycyrrhetinic acid (18α-GA) was used to block the intercellular communication of Cx43 between MLO-Y4 and MC3T3-E1 cells. Ti particles increased Cx43 expression and decreased β-catenin expression in MLO-Y4 cells. The silencing of Cx43 increased the β-catenin expression, and the over-expression of Cx43 decreased the β-catenin expression. In the co-culture model, Ti treatment of MLO-Y4 cells inhibited the osteoblastic differentiation of MC3T3-E1 cells and Cx43 silencing in MLO-Y4 cells attenuated the inhibitory effects on osteoblastic differentiation. With Cx43 silencing in the MLO-Y4 cells, the MC3T3-E1 cells, co-cultured alongside MLO-Y4, displayed decreased Cx43 expression, increased β-catenin expression, activation of Runx2, and promotion of osteoblastic differentiation in vitro co-culture. Finally, Cx43 expression was found to be negatively correlated to the activity of the Wnt signaling pathway, mostly through the Cx43 binding of β-catenin from its translocation to the nucleus. The results of our study suggest that Ti particles increased Cx43 expression in osteocytes and that osteocytes may participate in the regulation of osteoblast function via the Cx43 during PPO.
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Affiliation(s)
- Hao Chai
- Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou 215004, China
| | - Qun Huang
- Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou 215004, China
| | - Zixue Jiao
- Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou 215004, China
| | - Shendong Wang
- Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou 215004, China
| | - Chunguang Sun
- Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou 215004, China
| | - Dechun Geng
- Department of Orthopedics, The First Affiliated Hospital of Soochow University, Suzhou 215004, China
| | - Wei Xu
- Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou 215004, China
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7
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Zhao D, Wu J, Acosta FM, Xu H, Jiang JX. Connexin 43 hemichannels and prostaglandin E 2 release in anabolic function of the skeletal tissue to mechanical stimulation. Front Cell Dev Biol 2023; 11:1151838. [PMID: 37123401 PMCID: PMC10133519 DOI: 10.3389/fcell.2023.1151838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 04/05/2023] [Indexed: 05/02/2023] Open
Abstract
Bone adapts to changes in the physical environment by modulating remodeling through bone resorption and formation to maintain optimal bone mass. As the most abundant connexin subtype in bone tissue, connexin 43 (Cx43)-forming hemichannels are highly responsive to mechanical stimulation by permitting the exchange of small molecules (<1.2 kDa) between bone cells and the extracellular environment. Upon mechanical stimulation, Cx43 hemichannels facilitate the release of prostaglandins E2 (PGE2), a vital bone anabolic factor from osteocytes. Although most bone cells are involved in mechanosensing, osteocytes are the principal mechanosensitive cells, and PGE2 biosynthesis is greatly enhanced by mechanical stimulation. Mechanical stimulation-induced PGE2 released from osteocytic Cx43 hemichannels acts as autocrine effects that promote β-catenin nuclear accumulation, Cx43 expression, gap junction function, and protects osteocytes against glucocorticoid-induced osteoporosis in cultured osteocytes. In vivo, Cx43 hemichannels with PGE2 release promote bone formation and anabolism in response to mechanical loading. This review summarizes current in vitro and in vivo understanding of Cx43 hemichannels and extracellular PGE2 release, and their roles in bone function and mechanical responses. Cx43 hemichannels could be a significant potential new therapeutic target for treating bone loss and osteoporosis.
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Affiliation(s)
- Dezhi Zhao
- School of Medicine, Northwest University, Xi’an, China
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, United States
- School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
| | - Jiawei Wu
- School of Medicine, Northwest University, Xi’an, China
| | - Francisca M. Acosta
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, United States
| | - Huiyun Xu
- School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
| | - Jean X. Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, United States
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8
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Puts R, Khaffaf A, Shaka M, Zhang H, Raum K. Focused Low-Intensity Pulsed Ultrasound (FLIPUS) Mitigates Apoptosis of MLO-Y4 Osteocyte-like Cells. Bioengineering (Basel) 2023; 10:bioengineering10030387. [PMID: 36978778 PMCID: PMC10045139 DOI: 10.3390/bioengineering10030387] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 03/01/2023] [Accepted: 03/15/2023] [Indexed: 03/30/2023] Open
Abstract
Long cytoplasmic processes of osteocytes orchestrate bone activity by integration of biochemical and mechanical signals and regulate load-induced bone adaptation. Low-Intensity Pulsed Ultrasound (LIPUS) is a clinically used technique for fracture healing that delivers mechanical impulses to the damaged bone tissue in a non-invasive and non-ionizing manner. The mechanism of action of LIPUS is still controversially discussed in the scientific community. In this study, the effect of focused LIPUS (FLIPUS) on the survival of starved MLO-Y4 osteocytes was investigated in vitro. Osteocytes stimulated for 10 min with FLIPUS exhibited extended dendrites, which formed frequent connections to neighboring cells and spanned longer distances. The sonicated cells displayed thick actin bundles and experienced increase in expression of connexin 43 (Cx43) proteins, especially on their dendrites, and E11 glycoprotein, which is responsible for the elongation of cellular cytoplasmic processes. After stimulation, expression of cell growth and survival genes as well as genes related to cell-cell communication was augmented. In addition, cell viability was improved after the sonication, and a decrease in ATP release in the medium was observed. In summary, FLIPUS mitigated apoptosis of starved osteocytes, which is likely related to the formation of the extensive dendritic network that ensured cell survival.
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Affiliation(s)
- Regina Puts
- Center for Biomedicine, Charité-Universitätsmedizin, 12203 Berlin, Germany
- Berlin Institute of Health (BIH) Center for Regenerative Therapies, Charité-Universitätsmedizin, 13353 Berlin, Germany
| | - Aseel Khaffaf
- Center for Biomedicine, Charité-Universitätsmedizin, 12203 Berlin, Germany
| | - Maria Shaka
- Center for Biomedicine, Charité-Universitätsmedizin, 12203 Berlin, Germany
| | - Hui Zhang
- Center for Biomedicine, Charité-Universitätsmedizin, 12203 Berlin, Germany
| | - Kay Raum
- Center for Biomedicine, Charité-Universitätsmedizin, 12203 Berlin, Germany
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Li G, Zhang L, Lu Z, Yang B, Yang H, Shang P, Jiang JX, Wang D, Xu H. Connexin 43 Channels in Osteocytes Are Necessary for Bone Mass and Skeletal Muscle Function in Aged Male Mice. Int J Mol Sci 2022; 23:13506. [PMID: 36362291 PMCID: PMC9654692 DOI: 10.3390/ijms232113506] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 10/24/2022] [Accepted: 11/03/2022] [Indexed: 09/26/2023] Open
Abstract
Osteoporosis and sarcopenia (termed "Osteosarcopenia"), the twin-aging diseases, are major contributors to reduced bone mass and muscle weakness in the elderly population. Connexin 43 (Cx43) in osteocytes has been previously reported to play vital roles in bone homeostasis and muscle function in mature mice. The Cx43-formed gap junctions (GJs) and hemichannels (HCs) in osteocytes are important portals for the exchange of small molecules in cell-to-cell and cell-to-extracellular matrix, respectively. However, the roles of Cx43-based GJs and HCs in both bone and muscle aging are still unclear. Here, we used two transgenic mouse models with overexpression of the dominant negative Cx43 mutants primarily in osteocytes driven by the 10-kb Dmp1 promoter, R76W mice (inhibited gap junctions but enhanced hemichannels) and Δ130-136 mice (both gap junction and hemichannels are inhibited), to determine the actions of Cx43-based hemichannels (HCs) and gap junctions (GJs) in the regulation of bone and skeletal muscle from aged mice (18 months) as compared with those from adult mice (10 months). We demonstrated that enhancement of Cx43 HCs reduces bone mass due to increased osteoclast surfaces while the impairment of Cx43 HCs increases osteocyte apoptosis in aged mice caused by reduced PGE2 levels. Furthermore, altered mitochondrial homeostasis with reduced expression of Sirt-1, OPA-1, and Drp-1 resulted in excessive ROS level in muscle soleus (SL) of aged transgenic mice. In vitro, the impairment of Cx43 HCs in osteocytes from aged mice also promoted muscle collagen synthesis through activation of TGFβ/smad2/3 signaling because of reduced PGE2 levels in the PO CM. These findings indicate that the enhancement of Cx43 HCs while GJs are inhibited reduces bone mass, and the impairment of Cx43 HCs inhibits PGE2 level in osteocytes and this reduction promotes muscle collagen synthesis in skeletal muscle through activation of TGFβ/smad2/3 signaling, which together with increased ROS level contributes to reduced muscle force in aged mice.
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Affiliation(s)
- Guobin Li
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an 710072, China
- College of Life Sciences, Inner Mongolia Agricultural University, Hohhot 010018, China
| | - Lan Zhang
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an 710072, China
| | - Zhe Lu
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an 710072, China
| | - Baoqiang Yang
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an 710072, China
| | - Hui Yang
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an 710072, China
| | - Peng Shang
- Key Laboratory for Space Bioscience and Biotechnology, Research and Development Institute in Shenzhen, Northwestern Polytechnical University, Shenzhen 518057, China
| | - Jean X. Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX 78229, USA
| | - Dong’en Wang
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an 710072, China
| | - Huiyun Xu
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an 710072, China
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10
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Zhao D, Hua R, Riquelme MA, Cheng H, Guda T, Xu H, Gu S, Jiang JX. Osteocytes regulate bone anabolic response to mechanical loading in male mice via activation of integrin α5. Bone Res 2022; 10:49. [PMID: 35851577 PMCID: PMC9293884 DOI: 10.1038/s41413-022-00222-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 05/25/2022] [Accepted: 06/13/2022] [Indexed: 12/18/2022] Open
Abstract
Physical mechanical stimulation can maintain and even increase bone mass. Here, we report an important role of osteocytic integrin α5 in regulating the anabolic response of bone to mechanical loading using an Itga5 conditional gene knockout (cKO) mouse model. Integrin α5 gene deletion increased apoptotic osteocytes and reduced cortical anabolic responses to tibial compression including decreased endosteal osteoblasts and bone formation, and increased endosteal osteoclasts and bone resorption, contributing to the decreased bone area fraction and biomechanical properties, leading to an enlarged bone marrow area in cKO mice. Similar disruption of anabolic responses to mechanical loading was also detected in cKO trabecular bone. Moreover, integrin α5 deficiency impeded load-induced Cx43 hemichannel opening, and production and release of PGE2, an anabolic factor, resulting in attenuated effects of the loading on catabolic sclerostin (SOST) reduction and anabolic β-catenin increase. Together, this study shows an indispensable role of integrin α5 in osteocytes in the anabolic action of mechanical loading on skeletal tissue through activation of hemichannels and PGE2-evoked gene expression. Integrin α5 could act as a potential new therapeutic target for bone loss, especially in the elderly population with impeded mechanical sensitivity.
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Affiliation(s)
- Dezhi Zhao
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
- School of Life Sciences, Northwestern Polytechnical University, Xi'an, China
| | - Rui Hua
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Manuel A Riquelme
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Hongyun Cheng
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Teja Guda
- Department of Biomedical Engineering and Chemical Engineering, University of Texas, San Antonio, TX, USA
| | - Huiyun Xu
- School of Life Sciences, Northwestern Polytechnical University, Xi'an, China
| | - Sumin Gu
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Jean X Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA.
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11
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Hua R, Gu S, Jiang JX. Connexin 43 Hemichannels Regulate Osteoblast to Osteocyte Differentiation. Front Cell Dev Biol 2022; 10:892229. [PMID: 35693933 PMCID: PMC9184820 DOI: 10.3389/fcell.2022.892229] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 04/18/2022] [Indexed: 11/13/2022] Open
Abstract
Connexin 43 (Cx43) is the predominant connexin subtype expressed in osteocytes. Osteocytes, accounting for 90%–95% of total bone cells, function as orchestrators coordinating balanced activity between bone-resorbing osteoclasts and bone-forming osteoblasts. In this study, two newly developed osteocytic cell lines, OCY454 and IDG-SW3, were used to determine the role of Cx43 gap junctions and hemichannels (HCs) in the regulation of osteoblast to osteocyte differentiation. We found that the Cx43 level was substantially increased during the differentiation of IDG-SW3 cells and is also much higher than that of OCY454 cells. We knocked down Cx43 expression using the lentiviral CRISPR/Cas9 approach and inhibition of Cx43 HCs using Cx43 (E2) antibody in IDG-SW3 cells. Cx43 knockdown (KD) or Cx43 HC inhibition decreased gene expression for osteoblast and osteocyte markers, including alkaline phosphatase, type I collagen, dentin matrix protein 1, sclerostin, and fibroblast growth factor 23, whereas increasing the osteoclastogenesis indicator and the receptor activator of nuclear factor kappa-B ligand (RANKL)/osteoprotegerin (OPG) ratio at early and late differentiation stages. Moreover, mineralization was remarkably attenuated in differentiated Cx43-deficient IDG-SW3 cells compared to ROSA26 control. The conditioned medium collected from fully differentiated IDG-SW3 cells with Cx43 KD promoted osteoclastogenesis of RAW264.7 osteoclast precursors. Our results demonstrated that Cx43 HCs play critical roles in osteoblast to osteocyte differentiation process and regulate osteoclast differentiation via secreted factors.
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12
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Zhao D, Riquelme MA, Guda T, Tu C, Xu H, Gu S, Jiang JX. Connexin hemichannels with prostaglandin release in anabolic function of bone to mechanical loading. eLife 2022; 11:74365. [PMID: 35132953 PMCID: PMC8824479 DOI: 10.7554/elife.74365] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 01/10/2022] [Indexed: 01/18/2023] Open
Abstract
Mechanical stimulation, such as physical exercise, is essential for bone formation and health. Here, we demonstrate the critical role of osteocytic Cx43 hemichannels in anabolic function of bone in response to mechanical loading. Two transgenic mouse models, R76W and Δ130–136, expressing dominant-negative Cx43 mutants in osteocytes were adopted. Mechanical loading of tibial bone increased cortical bone mass and mechanical properties in wild-type and gap junction-impaired R76W mice through increased PGE2, endosteal osteoblast activity, and decreased sclerostin. These anabolic responses were impeded in gap junction/hemichannel-impaired Δ130–136 mice and accompanied by increased endosteal osteoclast activity. Specific inhibition of Cx43 hemichannels by Cx43(M1) antibody suppressed PGE2 secretion and impeded loading-induced endosteal osteoblast activity, bone formation and anabolic gene expression. PGE2 administration rescued the osteogenic response to mechanical loading impeded by impaired hemichannels. Together, osteocytic Cx43 hemichannels could be a potential new therapeutic target for treating bone loss and osteoporosis.
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Affiliation(s)
- Dezhi Zhao
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, United States.,School of Life Sciences, Northwestern Polytechnical University, Xian, China
| | - Manuel A Riquelme
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, United States
| | - Teja Guda
- Department of Biomedical Engineering and Chemical Engineering, University of Texas at San Antonio, San Antonio, United States
| | - Chao Tu
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, United States.,Department of Orthopedics, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Huiyun Xu
- School of Life Sciences, Northwestern Polytechnical University, Xian, China
| | - Sumin Gu
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, United States
| | - Jean X Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, United States
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13
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An S, Zheng S, Cai Z, Chen S, Wang C, Li Y, Deng Z. Connexin43 in Musculoskeletal System: New Targets for Development and Disease Progression. Aging Dis 2022; 13:1715-1732. [DOI: 10.14336/ad.2022.0421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 04/21/2022] [Indexed: 11/18/2022] Open
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14
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Gong K, Hong Q, Wu H, Wang F, Zhong L, Shen L, Xu P, Zhang W, Cao H, Zhan YY, Hu T, Hong X. Gap junctions mediate glucose transfer to promote colon cancer growth in three-dimensional spheroid culture. Cancer Lett 2022; 531:27-38. [DOI: 10.1016/j.canlet.2022.01.023] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Revised: 01/18/2022] [Accepted: 01/18/2022] [Indexed: 11/02/2022]
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15
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Osteocytic Connexin Hemichannels Modulate Oxidative Bone Microenvironment and Breast Cancer Growth. Cancers (Basel) 2021; 13:cancers13246343. [PMID: 34944962 PMCID: PMC8699531 DOI: 10.3390/cancers13246343] [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: 11/11/2021] [Revised: 12/09/2021] [Accepted: 12/13/2021] [Indexed: 11/16/2022] Open
Abstract
Osteocytes, the most abundant bone cell types embedded in the mineral matrix, express connexin 43 (Cx43) hemichannels that play important roles in bone remodeling and osteocyte survival. Estrogen deficiency decreases osteocytic Cx43 hemichannel activity and causes a loss in osteocytes' resistance to oxidative stress (OS). In this study, we showed that OS reduced the growth of both human (MDA-MB-231) and murine (Py8119) breast cancer cells. However, co-culturing these cells with osteocytes reduced the inhibitory effect of OS on breast cancer cells, and this effect was ablated by the inhibition of Cx43 hemichannels. Py8119 cells were intratibially implanted in the bone marrow of ovariectomized (OVX) mice to determine the role of osteocytic Cx43 hemichannels in breast cancer bone metastasis in response to OS. Two transgenic mice overexpressing dominant-negative Cx43 mutants, R76W and Δ130-136, were adopted for this study; the former inhibits gap junctions while the latter inhibits gap junctions and hemichannels. Under normal conditions, Δ130-136 mice had significantly more tumor growth in bone than that in WT and R76W mice. OVX increased tumor growth in R76W but had no significant effect on WT mice. In contrast, OVX reduced tumor growth in Δ130-136 mice. To confirm the role of OS, WT and Δ130-136 mice were administered the antioxidant N-acetyl cysteine (NAC). NAC increased tumor burden and growth in Δ130-136 mice but not in WT mice. Together, the data suggest that osteocytes and Cx43 hemichannels play pivotal roles in modulating the oxidative microenvironment and breast cancer growth in the bone.
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16
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Liu Y, Duan M, Guo D, Kan S, Zhang L, Aili M, Zhang D, Du W, Xie J. PDGF-AA promotes cell-to-cell communication in osteocytes through PI3K/Akt signaling pathway. Acta Biochim Biophys Sin (Shanghai) 2021; 53:1640-1649. [PMID: 34586354 DOI: 10.1093/abbs/gmab136] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 08/24/2021] [Accepted: 09/23/2021] [Indexed: 02/05/2023] Open
Abstract
Osteocytes are the main sensitive cells in bone remodeling due to their potent functional cell processes from the mineralized bone matrix to the bone surface and the bone marrow. Neighboring osteocytes communicate with each other by these cell processes to achieve molecular exchange through gap junction channels. Platelet-derived growth factor-AA (PDGF-AA) has been reported to enhance bone tissue remodeling by promoting cell proliferation, migration, and autocrine secretion in osteoid cell linage. However, the effect of PDGF-AA on intercellular communication between osteocytes is still unclear. In the present study, we elucidated that PDGF-AA could enhance the formation of dendritic processes of osteocytes and the gap junctional intercellular communication by promoting the expression of connexin43 (Cx43). This modulation process was mainly dependent on the activation of phosphorylation of Akt protein by phosphatidylinositol 3-kinase (PI3K)/Akt (also known as protein kinase B, PKB) signaling. Inhibition of PI3K/Akt signaling decreased the Cx43 expression induced by PDGF-AA. These results establish a bridge between PDGF-AA and cell-cell communication in osteocytes, which could help us understand the molecular exchange between bone cells and fracture healing.
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Affiliation(s)
- Yang Liu
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610064, China
| | - Mengmeng Duan
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610064, China
| | - Daimo Guo
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610064, China
| | - Shiyi Kan
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610064, China
| | - Li Zhang
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610064, China
| | - Munire Aili
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610064, China
| | - Demao Zhang
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610064, China
| | - Wei Du
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610064, China
- National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610064, China
- Department of Cariology and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu 610064, China
| | - Jing Xie
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610064, China
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17
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Isojima T, Sims NA. Cortical bone development, maintenance and porosity: genetic alterations in humans and mice influencing chondrocytes, osteoclasts, osteoblasts and osteocytes. Cell Mol Life Sci 2021; 78:5755-5773. [PMID: 34196732 PMCID: PMC11073036 DOI: 10.1007/s00018-021-03884-w] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 06/06/2021] [Accepted: 06/21/2021] [Indexed: 12/13/2022]
Abstract
Cortical bone structure is a crucial determinant of bone strength, yet for many years studies of novel genes and cell signalling pathways regulating bone strength have focused on the control of trabecular bone mass. Here we focus on mechanisms responsible for cortical bone development, growth, and degeneration, and describe some recently described genetic-driven modifications in humans and mice that reveal how these processes may be controlled. We start with embryonic osteogenesis of preliminary bone structures preceding the cortex and describe how this structure consolidates then matures to a dense, vascularised cortex containing an increasing proportion of lamellar bone. These processes include modelling-induced, and load-dependent, asymmetric cortical expansion, which enables the cortex's transition from a highly porous woven structure to a consolidated and thickened highly mineralised lamellar bone structure, infiltrated by vascular channels. Sex-specific differences emerge during this process. With aging, the process of consolidation reverses: cortical pores enlarge, leading to greater cortical porosity, trabecularisation and loss of bone strength. Each process requires co-ordination between bone formation, bone mineralisation, vascularisation, and bone resorption, with a need for locational-, spatial- and cell-specific signalling pathways to mediate this co-ordination. We will discuss these processes, and a number of cell-signalling pathways identified in both murine and human genetic studies to regulate cortical bone mass, including signalling through gp130, STAT3, PTHR1, WNT16, NOTCH, NOTUM and sFRP4.
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Affiliation(s)
- Tsuyoshi Isojima
- St. Vincent's Institute of Medical Research, 9 Princes St, Fitzroy, VIC, 3122, Australia
- Department of Pediatrics, Teikyo University School of Medicine, Tokyo, Japan
| | - Natalie A Sims
- St. Vincent's Institute of Medical Research, 9 Princes St, Fitzroy, VIC, 3122, Australia.
- Department of Medicine at St. Vincent's Hospital, The University of Melbourne, Fitzroy, VIC, Australia.
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18
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Hagan ML, Balayan V, McGee-Lawrence ME. Plasma membrane disruption (PMD) formation and repair in mechanosensitive tissues. Bone 2021; 149:115970. [PMID: 33892174 PMCID: PMC8217198 DOI: 10.1016/j.bone.2021.115970] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 03/26/2021] [Accepted: 04/17/2021] [Indexed: 01/04/2023]
Abstract
Mammalian cells employ an array of biological mechanisms to detect and respond to mechanical loading in their environment. One such mechanism is the formation of plasma membrane disruptions (PMD), which foster a molecular flux across cell membranes that promotes tissue adaptation. Repair of PMD through an orchestrated activity of molecular machinery is critical for cell survival, and the rate of PMD repair can affect downstream cellular signaling. PMD have been observed to influence the mechanical behavior of skin, alveolar, and gut epithelial cells, aortic endothelial cells, corneal keratocytes and epithelial cells, cardiac and skeletal muscle myocytes, neurons, and most recently, bone cells including osteoblasts, periodontal ligament cells, and osteocytes. PMD are therefore positioned to affect the physiological behavior of a wide range of vertebrate organ systems including skeletal and cardiac muscle, skin, eyes, the gastrointestinal tract, the vasculature, the respiratory system, and the skeleton. The purpose of this review is to describe the processes of PMD formation and repair across these mechanosensitive tissues, with a particular emphasis on comparing and contrasting repair mechanisms and downstream signaling to better understand the role of PMD in skeletal mechanobiology. The implications of PMD-related mechanisms for disease and potential therapeutic applications are also explored.
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Affiliation(s)
- Mackenzie L Hagan
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1460 Laney Walker Blvd., CB1101, Augusta, GA, USA
| | - Vanshika Balayan
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1460 Laney Walker Blvd., CB1101, Augusta, GA, USA
| | - Meghan E McGee-Lawrence
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1460 Laney Walker Blvd., CB1101, Augusta, GA, USA; Department of Orthopaedic Surgery, Augusta University, Augusta, GA, USA.
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19
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Adhikari M, Delgado-Calle J. Role of Osteocytes in Cancer Progression in the Bone and the Associated Skeletal Disease. Curr Osteoporos Rep 2021; 19:247-255. [PMID: 33818732 PMCID: PMC8486016 DOI: 10.1007/s11914-021-00679-7] [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] [Accepted: 03/17/2021] [Indexed: 11/29/2022]
Abstract
PURPOSE OF REVIEW The goal of this manuscript is to review the current knowledge on the role of osteocytes in cancer in the bone, discuss the potential of osteocytes as a therapeutic target, and propose future research needed to understand the crosstalk between cancer cells and osteocytes in the tumor niche. RECENT FINDINGS Numerous studies have established that cancer cells manipulate osteocytes to facilitate invasion and tumor progression in bone. Moreover, cancer cells dysregulate osteocyte function to disrupt physiological bone remodeling, leading to the development of bone disease. Targeting osteocytes and their derived factors has proven to effectively interfere with the progression of cancer in the bone and the associated bone disease. Osteocytes communicate with cancer cells and are also part of the vicious cycle of cancer in the bone. Additional studies investigating the role of osteocytes on metastases to the bone and the development of drug resistance are needed.
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Affiliation(s)
- Manish Adhikari
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Jesús Delgado-Calle
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA.
- Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA.
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20
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Chen M, Li G, Zhang L, Ning K, Yang B, Jiang JX, Wang DE, Xu H. Primary Osteocyte Supernatants Metabolomic Profiling of Two Transgenic Mice With Connexin43 Dominant Negative Mutants. Front Endocrinol (Lausanne) 2021; 12:649994. [PMID: 34093433 PMCID: PMC8169970 DOI: 10.3389/fendo.2021.649994] [Citation(s) in RCA: 0] [Impact Index Per Article: 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: 01/06/2021] [Accepted: 04/06/2021] [Indexed: 11/13/2022] Open
Abstract
Osteocytes could release some small molecules (≤ 1 kDa) through gap junctions and hemichannels to extracellular environment, such as prostaglandin E2 (PGE2), nitric oxide (NO) and adenosine triphosphate (ATP), which play key roles in transferring signals between bone cells and other tissue cells. Connexin (Cx) 43 is the most abundant connexin in osteocytes. To further discover molecules released by osteocytes through Cx43 channels and better understand the regulatory function of Cx43 channels in osteocytes, we performed non-targeted global metabolomics analysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS) on conditioned medium collected from osteocytes isolated from two transgenic mouse models with Cx43 dominant negative mutants driven by a 10 kb-DMP1 promoter: R76W (gap junctions are blocked, whereas hemichannels are promoted) and Δ130-136 (both gap junctions and hemichannels are blocked). The results revealed that several new categories of molecules, such as "fatty acyls" and "carboxylic acids and derivatives", could be released through osteocytic Cx43 channels. In addition, alteration of Cx43 channel function affected the release of metabolites related to inflammatory reaction and oxidative stress. Pathway analysis further showed that citric acid cycle was the most differential metabolic pathway regulated by Cx43 channels. In sum, these results isolated new potential metabolites released by osteocytes through Cx43 channels, and offered a novel perspective to understand the regulatory mechanisms of osteocytes on themselves and other cells as well.
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Affiliation(s)
- Meng Chen
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
| | - Guobin Li
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
| | - Lan Zhang
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
| | - Kaiting Ning
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
| | - Baoqiang Yang
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
| | - Jean X. Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, United States
| | - Dong-En Wang
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
| | - Huiyun Xu
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
- Research Center of Special Environmental Biomechanics & Medical Engineering, Northwestern Polytechnical University, Xi’an, China
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21
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Zou ML, Chen ZH, Teng YY, Liu SY, Jia Y, Zhang KW, Sun ZL, Wu JJ, Yuan ZD, Feng Y, Li X, Xu RS, Yuan FL. The Smad Dependent TGF-β and BMP Signaling Pathway in Bone Remodeling and Therapies. Front Mol Biosci 2021; 8:593310. [PMID: 34026818 PMCID: PMC8131681 DOI: 10.3389/fmolb.2021.593310] [Citation(s) in RCA: 92] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 04/23/2021] [Indexed: 12/15/2022] Open
Abstract
Bone remodeling is a continuous process that maintains the homeostasis of the skeletal system, and it depends on the homeostasis between bone-forming osteoblasts and bone-absorbing osteoclasts. A large number of studies have confirmed that the Smad signaling pathway is essential for the regulation of osteoblastic and osteoclastic differentiation during skeletal development, bone formation and bone homeostasis, suggesting a close relationship between Smad signaling and bone remodeling. It is known that Smads proteins are pivotal intracellular effectors for the members of the transforming growth factor-β (TGF-β) and bone morphogenetic proteins (BMP), acting as transcription factors. Smad mediates the signal transduction in TGF-β and BMP signaling pathway that affects both osteoblast and osteoclast functions, and therefore plays a critical role in the regulation of bone remodeling. Increasing studies have demonstrated that a number of Smad signaling regulators have potential functions in bone remodeling. Therefore, targeting Smad dependent TGF-β and BMP signaling pathway might be a novel and promising therapeutic strategy against osteoporosis. This article aims to review recent advances in this field, summarizing the influence of Smad on osteoblast and osteoclast function, together with Smad signaling regulators in bone remodeling. This will facilitate the understanding of Smad signaling pathway in bone biology and shed new light on the modulation and potential treatment for osteoporosis.
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Affiliation(s)
- Ming-Li Zou
- Wuxi Clinical Medicine School of Integrated Chinese and Western Medicine, Nanjing University of Chinese Medicine, Wuxi, China.,Institute of Integrated Chinese and Western Medicine, The Hospital Affiliated to Jiangnan University, Wuxi, China
| | - Zhong-Hua Chen
- Institute of Integrated Chinese and Western Medicine, The Third Hospital Affiliated to Nantong University, Wuxi, China
| | - Ying-Ying Teng
- Institute of Integrated Chinese and Western Medicine, The Hospital Affiliated to Jiangnan University, Wuxi, China
| | - Si-Yu Liu
- Wuxi Clinical Medicine School of Integrated Chinese and Western Medicine, Nanjing University of Chinese Medicine, Wuxi, China.,Institute of Integrated Chinese and Western Medicine, The Hospital Affiliated to Jiangnan University, Wuxi, China
| | - Yuan Jia
- Wuxi Clinical Medicine School of Integrated Chinese and Western Medicine, Nanjing University of Chinese Medicine, Wuxi, China.,Institute of Integrated Chinese and Western Medicine, The Hospital Affiliated to Jiangnan University, Wuxi, China
| | - Kai-Wen Zhang
- Wuxi Clinical Medicine School of Integrated Chinese and Western Medicine, Nanjing University of Chinese Medicine, Wuxi, China.,Institute of Integrated Chinese and Western Medicine, The Hospital Affiliated to Jiangnan University, Wuxi, China
| | - Zi-Li Sun
- Wuxi Clinical Medicine School of Integrated Chinese and Western Medicine, Nanjing University of Chinese Medicine, Wuxi, China.,Institute of Integrated Chinese and Western Medicine, The Hospital Affiliated to Jiangnan University, Wuxi, China
| | - Jun-Jie Wu
- Institute of Integrated Chinese and Western Medicine, The Hospital Affiliated to Jiangnan University, Wuxi, China
| | - Zheng-Dong Yuan
- Institute of Integrated Chinese and Western Medicine, The Hospital Affiliated to Jiangnan University, Wuxi, China
| | - Yi Feng
- Institute of Integrated Chinese and Western Medicine, The Hospital Affiliated to Jiangnan University, Wuxi, China
| | - Xia Li
- Institute of Integrated Chinese and Western Medicine, The Hospital Affiliated to Jiangnan University, Wuxi, China
| | - Rui-Sheng Xu
- Institute of Integrated Chinese and Western Medicine, The Hospital Affiliated to Jiangnan University, Wuxi, China
| | - Feng-Lai Yuan
- Institute of Integrated Chinese and Western Medicine, The Hospital Affiliated to Jiangnan University, Wuxi, China
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22
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Preidl RHM, Amann K, Weber M, Schiller M, Ringler M, Ries J, Neukam FW, Kesting M, Geppert CI, Wehrhan F. Lineage-associated connexin 43 expression in bisphosphonate-exposed rat bones. J Craniomaxillofac Surg 2021; 49:738-747. [PMID: 33642117 DOI: 10.1016/j.jcms.2021.02.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 11/19/2020] [Accepted: 02/14/2021] [Indexed: 10/22/2022] Open
Abstract
Expression of signaling proteins in bone cells depends on their embryological mesoderm-derived (e.g. tibia) or cranial neural crest (CNC)-derived (e.g. jaw) origin. Connexin 43 (Cx43) is a gap junction protein that plays an essential role in the mode of action of bisphosphonates (BP). This study aimed to investigate Cx43 expression and the influence of BP application on mesoderm- and CNC-derived bone. Using a rat model, molar extraction and tibia osteotomy with (Group 4) or without (Group 3) previous BP application was performed. Untreated (Group 1) and animals selectively treated with BPs (Group 2) served as controls. Cx43 expression was immunohistochemically determined 12 and 16 weeks postoperatively via a labeling index. Cx43 expression in CNC-derived bone was significantly higher compared with mesodermal bone. BP application decreased Cx43 expression; however, detected expression levels were still higher in jawbone (Group 2 tibia vs jaw: 5.83 ± 5.06 vs 23.52 ± 6.42; p = 0.007). During bone healing after surgical intervention (Group 3) there were no expression differences between tibia and jawbone. BP treatment prior to surgery resulted in significantly lower Cx43 expression in CNC-derived compared with tibia bone (Group 4 tibia vs jaw: 56.84 ± 15.57 vs 16.40 ± 5.66; p < 0.01). Increased Cx43 expression in jaw compared with tibia bone is in line with their embryological origins. A significant Cx43 suppression in jawbone after BP application and surgery might contribute to the selectively altered osseous turnover and development of MRONJ in CNC-derived bone.
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Affiliation(s)
- Raimund H M Preidl
- Resident, Department of Oral and Maxillofacial Surgery, University of Erlangen-Nuremberg, Glückstraße 11, 91056, Erlangen, Germany.
| | - Kerstin Amann
- Head of Nephropathology, University of Erlangen-Nuremberg, Glückstraße 11, 91056, Erlangen, Germany
| | - Manuel Weber
- Resident, Department of Oral and Maxillofacial Surgery, University of Erlangen-Nuremberg, Glückstraße 11, 91056, Erlangen, Germany
| | - Martin Schiller
- Doctoral Students, Department of Oral and Maxillofacial Surgery, University of Erlangen-Nuremberg, Glückstraße 11, 91056, Erlangen, Germany
| | - Manuela Ringler
- Doctoral Students, Department of Oral and Maxillofacial Surgery, University of Erlangen-Nuremberg, Glückstraße 11, 91056, Erlangen, Germany
| | - Jutta Ries
- Department of Oral and Maxillofacial Surgery, University of Erlangen-Nuremberg, Glückstraße 11, 91056, Erlangen, Germany
| | - Friedrich W Neukam
- Former Head of Department of Oral and Maxillofacial Surgery, University of Erlangen-Nuremberg, Glückstraße 11, 91056, Erlangen, Germany
| | - Marco Kesting
- Head of Department of Oral and Maxillofacial Surgery, University of Erlangen-Nuremberg, Glückstraße 11, 91056, Erlangen, Germany
| | - Carol-Immanuel Geppert
- Specialist in Pathology, University of Erlangen-Nuremberg, Glückstraße 11, 91056, Erlangen, Germany
| | - Falk Wehrhan
- Specialist in Oral and Maxillofacial Surgery, Department of Oral and Maxillofacial Surgery, University of Erlangen-Nuremberg, Glückstraße 11, 91056, Erlangen, Germany
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23
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Riquelme MA, Gu S, Hua R, Jiang JX. Mechanotransduction via the coordinated actions of integrins, PI3K signaling and Connexin hemichannels. Bone Res 2021; 9:8. [PMID: 33531460 PMCID: PMC7854719 DOI: 10.1038/s41413-020-00126-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Revised: 09/25/2020] [Accepted: 10/14/2020] [Indexed: 12/11/2022] Open
Abstract
Mechanical loading opens connexin 43 (Cx43) hemichannels (HCs), leading to the release of bone anabolic molecules, such as prostaglandins, from mechanosensitive osteocytes, which is essential for bone formation and remodeling. However, the mechanotransduction mechanism that activates HCs remains elusive. Here, we report a unique pathway by which mechanical signals are effectively transferred between integrin molecules located in different regions of the cell, resulting in HC activation. Both integrin α5 and αV were activated upon mechanical stimulation via either fluid dropping or flow shear stress (FSS). Inhibition of integrin αV activation or ablation of integrin α5 prevented HC opening on the cell body when dendrites were mechanically stimulated, suggesting mechanical transmission from the dendritic integrin αV to α5 in the cell body during HC activation. In addition, HC function was compromised in vivo, as determined by utilizing an antibody blocking αV activation and α5-deficient osteocyte-specific knockout mice. Furthermore, inhibition of integrin αV activation, but not that of α5, attenuated activation of the phosphoinositide 3-kinase (PI3K)-protein kinase B (AKT) signaling pathway upon mechanical loading, and the inhibition of PI3K/AKT activation blocked integrin α5 activation and HC opening. Moreover, HC opening was blocked only by an anti-integrin αV antibody at low but not high FSS levels, suggesting that dendritic αV is a more sensitive mechanosensor than α5 for activating HCs. Together, these results reveal a new molecular mechanism of mechanotransduction involving the coordinated actions of integrins and PI3K/AKT in osteocytic dendritic processes and cell bodies that leads to HC opening and the release of key bone anabolic factors.
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Affiliation(s)
- Manuel A Riquelme
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, 78229-3900, USA
| | - Sumin Gu
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, 78229-3900, USA
| | - Rui Hua
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, 78229-3900, USA
| | - Jean X Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, 78229-3900, USA.
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Hua R, Zhang J, Riquelme MA, Jiang JX. Connexin Gap Junctions and Hemichannels Link Oxidative Stress to Skeletal Physiology and Pathology. Curr Osteoporos Rep 2021; 19:66-74. [PMID: 33403446 PMCID: PMC8174533 DOI: 10.1007/s11914-020-00645-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/16/2020] [Indexed: 12/15/2022]
Abstract
PURPOSE OF REVIEW The goal of this review is to provide an overview of the impact and underlying mechanism of oxidative stress on connexin channel function, and their roles in skeletal aging, estrogen deficiency, and glucocorticoid excess associated bone loss. RECENT FINDINGS Connexin hemichannel opening is increased under oxidative stress conditions, which confers a cell protective role against oxidative stress-induced cell death. Oxidative stress acts as a key contributor to aging, estrogen deficiency, and glucocorticoid excess-induced osteoporosis and impairs osteocytic network and connexin gap junction communication. This paper reviews the current knowledge for the role of oxidative stress and connexin channels in the pathogenesis of osteoporosis and physiological and pathological responses of connexin channels to oxidative stress. Oxidative stress decreases osteocyte viability and impairs the balance of anabolic and catabolic responses. Connexin 43 (Cx43) channels play a critical role in bone remodeling, mechanotransduction, and survival of osteocytes. Under oxidative stress conditions, there is a consistent reduction of Cx43 expression, while the opening of Cx43 hemichannels protects osteocytes against cell injury caused by oxidative stress.
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Affiliation(s)
- Rui Hua
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Jingruo Zhang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Manuel A Riquelme
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Jean X Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA.
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Osteocytic Connexin43 Channels Regulate Bone-Muscle Crosstalk. Cells 2021; 10:cells10020237. [PMID: 33530465 PMCID: PMC7911162 DOI: 10.3390/cells10020237] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 01/22/2021] [Accepted: 01/23/2021] [Indexed: 02/01/2023] Open
Abstract
Bone–muscle crosstalk plays an important role in skeletal biomechanical function, the progression of numerous pathological conditions, and the modulation of local and distant cellular environments. Previous work has revealed that the deletion of connexin (Cx) 43 in osteoblasts, and consequently, osteocytes, indirectly compromises skeletal muscle formation and function. However, the respective roles of Cx43-formed gap junction channels (GJs) and hemichannels (HCs) in the bone–muscle crosstalk are poorly understood. To this end, we used two Cx43 osteocyte-specific transgenic mouse models expressing dominant negative mutants, Δ130–136 (GJs and HCs functions are inhibited), and R76W (only GJs function is blocked), to determine the effect of these two types of Cx43 channels on neighboring skeletal muscle. Blockage of osteocyte Cx43 GJs and HCs in Δ130–136 mice decreased fast-twitch muscle mass with reduced muscle protein synthesis and increased muscle protein degradation. Both R76W and Δ130–136 mice exhibited decreased muscle contractile force accompanied by a fast-to-slow fiber transition in typically fast-twitch muscles. In vitro results further showed that myotube formation of C2C12 myoblasts was inhibited after treatment with the primary osteocyte conditioned media (PO CM) from R76W and Δ130–136 mice. Additionally, prostaglandin E2 (PGE2) level was significantly reduced in both the circulation and PO CM of the transgenic mice. Interestingly, the injection of PGE2 to the transgenic mice rescued fast-twitch muscle mass and function; however, this had little effect on protein synthesis and degradation. These findings indicate a channel-specific response: inhibition of osteocytic Cx43 HCs decreases fast-twitch skeletal muscle mass alongside reduced protein synthesis and increased protein degradation. In contrast, blockage of Cx43 GJs results in decreased fast-twitch skeletal muscle contractile force and myogenesis, with PGE2 partially accounting for the measured differences.
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Gortázar AR, Ardura JA. Osteocytes and Diabetes: Altered Function of Diabetic Osteocytes. Curr Osteoporos Rep 2020; 18:796-802. [PMID: 33184775 DOI: 10.1007/s11914-020-00641-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/28/2020] [Indexed: 12/15/2022]
Abstract
PURPOSE OF REVIEW Diabetes mellitus is a prevalent chronic disease affecting millions of people in the world. Bone fragility is a complication found in diabetic patients. Although osteoblasts and osteoclasts are directly affected by diabetes, herein we focus on how the diabetic state-based on hyperglycemia and accumulation of advanced glycation end products among other features-impairs osteocyte functions exerting deleterious effects on bone. RECENT FINDINGS In the last years, several studies described that diabetic conditions cause morphological modifications on lacunar-canalicular system, alterations on osteocyte mechanoreceptors and intracellular pathways and on osteocyte communication with other cells through the secretion of proteins such as sclerostin or RANKL. This article gives an overview of events occurring in diabetic osteocytes. In particular, mechanical responses seem to be seriously affected in these conditions, suggesting that mechanical sensibility could be a target for future research in the field.
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Affiliation(s)
- Arancha R Gortázar
- Bone Physiopathology laboratory, Applied Molecular Medicine Institute (IMMA), Universidad San Pablo-CEU, CEU Universities, Campus Monteprincipe, 28925, Alcorcón, Madrid, Spain.
- Departamento de Ciencias Médicas Básicas, Facultad de Medicina, Universidad San Pablo-CEU,CEU Universities, Campus Monteprincipe, 28925, Alcorcón, Madrid, Spain.
| | - Juan A Ardura
- Bone Physiopathology laboratory, Applied Molecular Medicine Institute (IMMA), Universidad San Pablo-CEU, CEU Universities, Campus Monteprincipe, 28925, Alcorcón, Madrid, Spain
- Departamento de Ciencias Médicas Básicas, Facultad de Medicina, Universidad San Pablo-CEU,CEU Universities, Campus Monteprincipe, 28925, Alcorcón, Madrid, Spain
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27
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Osteocyte apoptosis: the roles and key molecular mechanisms in resorption-related bone diseases. Cell Death Dis 2020; 11:846. [PMID: 33046704 PMCID: PMC7552426 DOI: 10.1038/s41419-020-03059-8] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 09/23/2020] [Accepted: 09/24/2020] [Indexed: 01/18/2023]
Abstract
Vital osteocytes have been well known to function as an important orchestrator in the preservation of robustness and fidelity of the bone remodeling process. Nevertheless, some key pathological factors, such as sex steroid deficiency and excess glucocorticoids, and so on, are implicated in inducing a bulk of apoptotic osteocytes, subsequently resulting in resorption-related bone loss. As much, osteocyte apoptosis, under homeostatic conditions, is in an optimal state of balance tightly controlled by pro- and anti-apoptotic mechanism pathways. Importantly, there exist many essential signaling proteins in the process of osteocyte apoptosis, which has a crucial role in maintaining a homeostatic environment. While increasing in vitro and in vivo studies have established, in part, key signaling pathways and cross-talk mechanism on osteocyte apoptosis, intrinsic and complex mechanism underlying osteocyte apoptosis occurs in various states of pathologies remains ill-defined. In this review, we discuss not only essential pro- and anti-apoptotic signaling pathways and key biomarkers involved in these key mechanisms under different pathological agents, but also the pivotal role of apoptotic osteocytes in osteoclastogenesis-triggered bone loss, hopefully shedding new light on the attractive and proper actions of pharmacotherapeutics of targeting apoptosis and ensuing resorption-related bone diseases such as osteoporosis and fragility fractures.
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Price JC, Krause AL, Waters SL, El Haj AJ. Predicting Bone Formation in Mesenchymal Stromal Cell-Seeded Hydrogels Using Experiment-Based Mathematical Modeling. Tissue Eng Part A 2020; 26:1014-1023. [PMID: 32178595 DOI: 10.1089/ten.tea.2020.0027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
In vitro bone formation by mesenchymal stromal cells encapsulated in type-1 collagen hydrogels is demonstrated after a 28-day in vitro culture period. Analysis of the hydrogels is carried out by X-ray microcomputed tomography, histology, and immunohistochemistry, which collectively demonstrates that bone formation in the hydrogels was quantifiably proportional to the initial collagen concentration, and subsequently the population density of seeded cells. This was established by varying the initial collagen concentration at a constant cell seeding density (3 × 105 cells/0.3 mL hydrogel), and separately varying cell seeding density at a constant collagen concentration (1 mg/mL). Using these data, a mathematical model is presented for the total hydrogel volume and mineralization volume based on the observed linear contraction dynamics of cell-seeded collagen gels. The model parameters are fitted by comparing the predictions of the mathematical model for the hydrogel and mineralized volumes on day 28 with the experimental data. The model is then used to predict the hydrogel and mineralization volumes for a range of hydrogel collagen concentrations and cell seeding densities, providing comprehensive input/output descriptors for generating mineralized hydrogels for bone tissue engineering. It is proposed that this quantitative approach will be a useful tool for generating in vitro manufactured bone tissue, defining input parameters that yield predictable output measures of tissue maturation. Impact statement This article describes a simple yet powerful quantitative description of in vitro tissue-engineered bone by combining experimental data with mathematical modeling. The overall aim of the article is to examine what is currently known about cell-mediated collagen contraction, and demonstrate that this phenomenon can be exploited to tailor bone formation by choosing a specific set of input parameters in the form of cell seeding density and collagen hydrogel concentration. Our study utilizes a clinically relevant cell source (human mesenchymal stem cells) with a biomaterial that has received regulatory approval for use in humans (collagen type 1), and hence could be useful for clinical applications, as well as furthering our understanding of cell/extracellular matrix interactions in determining in vitro bone tissue formation.
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Affiliation(s)
- Joshua C Price
- Institute for Science and Technology in Medicine, Guy Hilton Research Centre, Keele University, Stoke-on-Trent, United Kingdom
- Optics and Photonics Research Group, Faculty of Engineering, The University of Nottingham, Nottingham, United Kingdom
| | - Andrew L Krause
- Mathematical Institute, University of Oxford, Oxford, United Kingdom
| | - Sarah L Waters
- Mathematical Institute, University of Oxford, Oxford, United Kingdom
| | - Alicia J El Haj
- Institute for Science and Technology in Medicine, Guy Hilton Research Centre, Keele University, Stoke-on-Trent, United Kingdom
- Healthcare Technology Institute, Institute of Translational Medicine, University of Birmingham, Birmingham, United Kingdom
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29
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Shen H, Schwartz AG, Civitelli R, Thomopoulos S. Connexin 43 Is Necessary for Murine Tendon Enthesis Formation and Response to Loading. J Bone Miner Res 2020; 35:1494-1503. [PMID: 32227614 PMCID: PMC7725385 DOI: 10.1002/jbmr.4018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 03/08/2020] [Accepted: 03/21/2020] [Indexed: 12/28/2022]
Abstract
The enthesis is a mineralized fibrocartilage transition that attaches tendon to bone and is vital for musculoskeletal function. Despite recent studies demonstrating the necessity of muscle loading for enthesis formation, the mechanisms that regulate enthesis formation and mechanoresponsiveness remain unclear. Therefore, the current study investigated the role of the gap junction protein connexin 43 in these processes by deleting Gja1 (the Cx43 gene) in the tendon and enthesis. Compared with their wild-type (WT) counterparts, mice lacking Cx43 showed disrupted entheseal cell alignment, reduced mineralized fibrocartilage, and impaired biomechanical properties of the supraspinatus tendon entheses during postnatal development. Cx43-deficient mice also exhibited reduced ability to complete a treadmill running protocol but no apparent deficits in daily activity, metabolic indexes, shoulder muscle size, grip strength, and major trabecular bone properties of the adjacent humeral head. To examine enthesis mechanoresponsiveness, young adult mice were subjected to modest treadmill exercise. Gja1 deficiency in the tendon and enthesis reduced entheseal anabolic responses to treadmill exercise: WT mice had increased expression of Sox9, Ihh, and Gli1 and increased Brdu incorporation, whereas Cx43-deficient mice showed no changes or decreased levels with exercise. Collectively, the results demonstrated an essential role for Cx43 in postnatal tendon enthesis formation, function, and response to loading; results further provided evidence implicating a link between Cx43 function and the hedgehog signaling pathway. © 2020 American Society for Bone and Mineral Research.
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Affiliation(s)
- Hua Shen
- Department of Orthopaedic Surgery, Washington University, St. Louis, MO, USA
| | - Andrea G Schwartz
- Department of Orthopaedic Surgery, Washington University, St. Louis, MO, USA
| | - Roberto Civitelli
- Department of Internal Medicine, Division of Bone and Mineral Disease, Washington University, St. Louis, MO, USA
| | - Stavros Thomopoulos
- Department of Orthopedic Surgery, Columbia University, New York, NY, USA.,Department of Biomedical Engineering, Columbia University, New York, NY, USA
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Giaume C, Naus CC, Sáez JC, Leybaert L. Glial Connexins and Pannexins in the Healthy and Diseased Brain. Physiol Rev 2020; 101:93-145. [PMID: 32326824 DOI: 10.1152/physrev.00043.2018] [Citation(s) in RCA: 75] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Over the past several decades a large amount of data have established that glial cells, the main cell population in the brain, dynamically interact with neurons and thus impact their activity and survival. One typical feature of glia is their marked expression of several connexins, the membrane proteins forming intercellular gap junction channels and hemichannels. Pannexins, which have a tetraspan membrane topology as connexins, are also detected in glial cells. Here, we review the evidence that connexin and pannexin channels are actively involved in dynamic and metabolic neuroglial interactions in physiological as well as in pathological situations. These features of neuroglial interactions open the way to identify novel non-neuronal aspects that allow for a better understanding of behavior and information processing performed by neurons. This will also complement the "neurocentric" view by facilitating the development of glia-targeted therapeutic strategies in brain disease.
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Affiliation(s)
- Christian Giaume
- Collège de France, Center for Interdisciplinary Research in Biology (CIRB)/Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7241/Institut National de la Santé et de la Recherche Médicale U1050, Paris, France; University Pierre et Marie Curie, Paris, France; MEMOLIFE Laboratory of Excellence and Paris Science Lettre Research University, Paris, France; Department of Cellular & Physiological Sciences, Life Sciences Institute, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago, Chile; Instituo de Neurociencias, Centro Interdisciplinario de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile; Physiology Group, Department of Basic and Applied Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
| | - Christian C Naus
- Collège de France, Center for Interdisciplinary Research in Biology (CIRB)/Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7241/Institut National de la Santé et de la Recherche Médicale U1050, Paris, France; University Pierre et Marie Curie, Paris, France; MEMOLIFE Laboratory of Excellence and Paris Science Lettre Research University, Paris, France; Department of Cellular & Physiological Sciences, Life Sciences Institute, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago, Chile; Instituo de Neurociencias, Centro Interdisciplinario de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile; Physiology Group, Department of Basic and Applied Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
| | - Juan C Sáez
- Collège de France, Center for Interdisciplinary Research in Biology (CIRB)/Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7241/Institut National de la Santé et de la Recherche Médicale U1050, Paris, France; University Pierre et Marie Curie, Paris, France; MEMOLIFE Laboratory of Excellence and Paris Science Lettre Research University, Paris, France; Department of Cellular & Physiological Sciences, Life Sciences Institute, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago, Chile; Instituo de Neurociencias, Centro Interdisciplinario de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile; Physiology Group, Department of Basic and Applied Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
| | - Luc Leybaert
- Collège de France, Center for Interdisciplinary Research in Biology (CIRB)/Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7241/Institut National de la Santé et de la Recherche Médicale U1050, Paris, France; University Pierre et Marie Curie, Paris, France; MEMOLIFE Laboratory of Excellence and Paris Science Lettre Research University, Paris, France; Department of Cellular & Physiological Sciences, Life Sciences Institute, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago, Chile; Instituo de Neurociencias, Centro Interdisciplinario de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile; Physiology Group, Department of Basic and Applied Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
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31
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Zhao D, Liu R, Li G, Chen M, Shang P, Yang H, Jiang JX, Xu H. Connexin 43 Channels in Osteocytes Regulate Bone Responses to Mechanical Unloading. Front Physiol 2020; 11:299. [PMID: 32296345 PMCID: PMC7137730 DOI: 10.3389/fphys.2020.00299] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 03/16/2020] [Indexed: 01/01/2023] Open
Abstract
Connexin (Cx) 43 forms gap junctions and hemichannels that mediate communication between osteocytes and adjacent cells or the extracellular environment in bone, respectively. To investigate the role of each channel type in response to mechanical unloading, two transgenic mouse models overexpressing dominant-negative Cx43 predominantly in osteocytes driven by a 10 kb dentin matrix protein 1 (Dmp1) promoter were generated. The R76W mutation resulted in gap junction inhibition and enhancement of hemichannels, whereas the Δ130-136 mutation inhibited both gap junctions and hemichannels. Both mutations led to cortical bone loss with increased endocortical osteoclast activity during unloading. Increased periosteal osteoclasts with decreased apoptotic osteocytes were observed only in R76W mice. These findings indicated that inhibiting osteocytic Cx43 channels promotes bone loss induced by unloading, mainly in the cortical area; moreover, hemichannels protect osteocytes against apoptosis and promote periosteal bone remodeling, whereas gap junctions modulate endocortical osteoclast activity in response to unloading.
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Affiliation(s)
- Dezhi Zhao
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
| | - Ruofei Liu
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
| | - Guobin Li
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
| | - Meng Chen
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
| | - Peng Shang
- Key Laboratory for Space Bioscience and Biotechnology, Research and Development Institute in Shenzhen, Northwestern Polytechnical University, Shenzhen, China
| | - Hui Yang
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
- Research Center of Special Environmental Biomechanics and Medical Engineering, Northwestern Polytechnical University, Xi’an, China
| | - Jean X. Jiang
- Department of Biochemistry and Structural Biology, The University of Texas Health Science Center, San Antonio, TX, United States
| | - Huiyun Xu
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an, China
- Key Laboratory for Space Bioscience and Biotechnology, Research and Development Institute in Shenzhen, Northwestern Polytechnical University, Shenzhen, China
- Research Center of Special Environmental Biomechanics and Medical Engineering, Northwestern Polytechnical University, Xi’an, China
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32
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Wang T, Yu X, He C. Pro-inflammatory Cytokines: Cellular and Molecular Drug Targets for Glucocorticoid-induced-osteoporosis via Osteocyte. Curr Drug Targets 2020; 20:1-15. [PMID: 29618305 DOI: 10.2174/1389450119666180405094046] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 03/11/2018] [Accepted: 03/21/2018] [Indexed: 02/08/2023]
Abstract
Glucocorticoids are widely used to treat varieties of allergic and autoimmune diseases, however, long-term application results in glucocorticoid-induced osteoporosis (GIOP). Inflammatory cytokines: tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) play important regulatory roles in bone metabolism, but their roles in GIOP remain largely unknown. Osteocytes can modulate the formation and function of both osteoblasts and osteoclasts, directly via gap junctions, or indirectly by transferring molecule signaling. Apoptotic osteocytes release RANKL, HMGB1 and pro-inflammatory cytokines to stimulate osteoclastogenesis. Moreover, osteocytes can secrete FGF23 to regulate bone metabolism. Exposure to high levels of GCs can drive osteocyte apoptosis and influence gap junctions, leading to bone loss. GCs treatment is regarded to produce more FGF23 to inhibit bone mineralization. GCs also disrupt the vascular to decrease osteocyte feasibility and mineral appositional rate, resulting in a decline in bone strength. Apoptotic bodies from osteocytes induced by GCs treatment can enhance production of TNF-α and IL-6. On the other hand, TNF-α and IL-6 show synergistic effects by altering osteocytes signaling towards osteoclasts and osteoblasts. In addition, TNF-α can induce osteocyte apoptosis and attribute to a worsened bone quality in GCs. IL-6 and osteocytes may interact with each other. Therefore, we hypothesize that GCs regulate osteocyteogenesis through TNF-α and IL-6, which are highly expressed around osteocyte undergoing apoptosis. In the present review, we summarized the roles of osteocytes in regulating osteoblasts and osteoclasts. Furthermore, the mechanism of GCs altered relationship between osteocytes and osteoblasts/osteoclasts. In addition, we discussed the roles of TNF-α and IL-6 in GIOP by modulating osteocytes. Lastly, we discussed the possibility of using pro-inflammatory signaling pathway as therapeutic targets to develop drugs for GIOP.
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Affiliation(s)
- Tiantian Wang
- Department of Rehabilitation Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, China.,Key Laboratory of Rehabilitation Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, China.,Laboratory of Endocrinology and Metabolism, Department of Endocrinology, National Key Laboratory of Biotherapy/Collaborative Innovation Center of Biotherapy and Cancer Center, West China Hospital, Sichuan University, 610041, China
| | - Xijie Yu
- Laboratory of Endocrinology and Metabolism, Department of Endocrinology, National Key Laboratory of Biotherapy/Collaborative Innovation Center of Biotherapy and Cancer Center, West China Hospital, Sichuan University, 610041, China
| | - Chengqi He
- Department of Rehabilitation Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, China.,Key Laboratory of Rehabilitation Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, China
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33
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Riquelme MA, Cardenas ER, Xu H, Jiang JX. The Role of Connexin Channels in the Response of Mechanical Loading and Unloading of Bone. Int J Mol Sci 2020; 21:ijms21031146. [PMID: 32050469 PMCID: PMC7038207 DOI: 10.3390/ijms21031146] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 01/31/2020] [Accepted: 02/04/2020] [Indexed: 12/13/2022] Open
Abstract
The skeleton adapts to mechanical loading to promote bone formation and remodeling. While most bone cells are involved in mechanosensing, it is well accepted that osteocytes are the principal mechanosensory cells. The osteocyte cell body and processes are surrounded by a fluid-filled space, forming an extensive lacuno-canalicular network. The flow of interstitial fluid is a major stress-related factor that transmits mechanical stimulation to bone cells. The long dendritic processes of osteocytes form a gap junction channel network connecting not only neighboring osteocytes, but also cells on the bone surface, such as osteoblasts and osteoclasts. Mechanosensitive osteocytes also form hemichannels that mediate the communication between the cytoplasmic and extracellular microenvironment. This paper will discuss recent research progress regarding connexin (Cx)-forming gap junctions and hemichannels in osteocytes, osteoblasts, and other bone cells, including those richly expressing Cx43. We will then cover the recent progress regarding the regulation of these channels by mechanical loading and the role of integrins and signals in mediating Cx43 channels, and bone cell function and viability. Finally, we will summarize the recent studies regarding bone responses to mechanical unloading in Cx43 transgenic mouse models. The osteocyte has been perceived as the center of bone remodeling, and connexin channels enriched in osteocytes are a likely major player in meditating the function of bone. Based on numerous studies, connexin channels may present as a potential new therapeutic target in the treatment of bone loss and osteoporosis. This review will primarily focus on Cx43, with some discussion in other connexins expressed in bone cells.
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Affiliation(s)
- Manuel A. Riquelme
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX 78229, USA; (M.A.R.); (E.R.C.)
| | - Eduardo R. Cardenas
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX 78229, USA; (M.A.R.); (E.R.C.)
| | - Huiyun Xu
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi’an 710072, China;
| | - Jean X. Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX 78229, USA; (M.A.R.); (E.R.C.)
- Correspondence: ; Tel.: +1-210-562-4094
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34
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Tresguerres F, Torres J, López-Quiles J, Hernández G, Vega J, Tresguerres I. The osteocyte: A multifunctional cell within the bone. Ann Anat 2020; 227:151422. [DOI: 10.1016/j.aanat.2019.151422] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2017] [Revised: 01/09/2019] [Accepted: 09/16/2019] [Indexed: 12/31/2022]
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35
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Yang L, Zhou G, Li M, Li Y, Yang L, Fu Q, Tian Y. High Glucose Downregulates Connexin 43 Expression and Its Gap Junction and Hemichannel Function in Osteocyte-like MLO-Y4 Cells Through Activation of the p38MAPK/ERK Signal Pathway. Diabetes Metab Syndr Obes 2020; 13:545-557. [PMID: 32161481 PMCID: PMC7049751 DOI: 10.2147/dmso.s239892] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 02/16/2020] [Indexed: 12/30/2022] Open
Abstract
PURPOSE Osteocyte network structure correlates with bone material quality. This network is profoundly altered in diabetic mice; however, the underlying mechanisms are unknown. The gap junction protein connexin 43 (Cx43) is necessary for normal osteocyte function and osteocyte network formation. Here, we evaluated Cx43 expression in patients with diabetes, the effect of high glucose on Cx43 expression, and the function of Cx43 gap junctions and hemichannels in osteocyte-like MLO-Y4 (MLO-Y4) cells. PATIENTS AND METHODS Human cortical bone samples were obtained from patients with or without type II diabetes mellitus (T2DM) who underwent arthroplasty surgery to treat osteoporosis-induced femoral neck fracture. UNLABELLED Cx43 expression was quantified in human cortical bone samples from both groups of patients and MLO-Y4 cells. The functions of Cx43 gap junctions and hemichannels in MLO-Y4 cells were evaluated using dye transfer and dye uptake assays, respectively. Furthermore, we evaluated levels of membrane Cx43 (mCx43), the functional form, and p38MAPK/ERK1/2 signaling, which is involved in mCx43 internalization, to characterize the mechanism of decreased Cx43 expression and gap junctions and hemichannels function. RESULTS Osteocyte Cx43 expression was decreased in femoral neck cortical bone samples of patients with T2DM patients compared with the non-diabetic control group. In addition, Cx43 expression was decreased in MLO-Y4 cells treated with high glucose. The functions of Cx43 gap junctions and hemichannels were inhibited in MLO-Y4 cells treated with high glucose. mCx43 expression was decreased in response to activation of p38-MAPK/ERK signaling. Inhibition of the p38-MAPK/ERK pathway partially reversed the decreases in Cx43 hemichannels and gap-junctions function. CONCLUSION High glucose dampened Cx43 gap junction and hemichannel function in MLO-Y4 cells by activating the p38MAPK/ERK pathway leading to subsequent mCx43 internalization.
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Affiliation(s)
- Lei Yang
- Orthopedics Department, Shengjing Hospital of China Medical University, Shenyang, Liaoning Province, People’s Republic of China
| | - Guangping Zhou
- Orthopedics Department, Shenyang Orthopedics Hospital, Shenyang, Liaoning Province, People’s Republic of China
| | - Mingyang Li
- Orthopedics Department, Shengjing Hospital of China Medical University, Shenyang, Liaoning Province, People’s Republic of China
| | - Yan Li
- Orthopedics Department, Shengjing Hospital of China Medical University, Shenyang, Liaoning Province, People’s Republic of China
| | - Liqing Yang
- Orthopedics Department, Shengjing Hospital of China Medical University, Shenyang, Liaoning Province, People’s Republic of China
| | - Qin Fu
- Orthopedics Department, Shengjing Hospital of China Medical University, Shenyang, Liaoning Province, People’s Republic of China
- Correspondence: Qin Fu Tel +86-18940251086 Email
| | - Ye Tian
- Orthopedics Department, Shengjing Hospital of China Medical University, Shenyang, Liaoning Province, People’s Republic of China
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36
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Abstract
Bone is the most frequent site of breast cancer and prostate cancer metastasis, and one of the most common sites of metastasis for many solid tumors. Once cancer cells colonize in the bone, it imposes a major clinical challenge for the treatment of the disease, and fatality rates increase drastically. Bone, the largest organ in the body, provides a fertile microenvironment enriched with nutrients, growth factors and hormones, a generous reward for cancer cells. Dependent on cancer type, cancer cells can cause osteoblastic (bone forming) or osteolytic lesions to promote the net resorption and/or release of growth factors from the bone extracellular matrix. These processes activate a "vicious cycle", leading to disruption of bone integrity and promoting cancer cell growth and migration. Cancer cells influence the bone microenvironment favoring their colonization and growth. In order to metastasize to the bone, cancer cells must first migrate from the site of origin, and once established within the bone, they must overcome the dormant inducing effects of resident cells. If successful, cancer cells can then colonize and continually disrupt bone homeostasis that is primarily maintained by osteocytes, the most abundant bone cell type. For example, it has been shown that exercise induces osteocytes to release anabolic factors that inhibit osteoclast resorptive activity, promote dormancy and the release of anti-cancer factors that inhibit breast cancer cell metastasis. In this review, we will summarize recent research findings and provide mechanistic insights related to the role of osteocytes in osteolytic metastasis.
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37
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Schlesinger PH, Blair HC, Beer Stolz D, Riazanski V, Ray EC, Tourkova IL, Nelson DJ. Cellular and extracellular matrix of bone, with principles of synthesis and dependency of mineral deposition on cell membrane transport. Am J Physiol Cell Physiol 2019; 318:C111-C124. [PMID: 31532718 DOI: 10.1152/ajpcell.00120.2019] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Bone differs from other connective tissues; it is isolated by a layer of osteoblasts that are connected by tight and gap junctions. This allows bone to create dense lamellar type I collagen, control pH, mineral deposition, and regulate water content forming a compact and strong structure. New woven bone formed after degradation of mineralized cartilage is rapidly degraded and resynthesized to impart structural order for local bone strength. Ossification is regulated by thickness of bone units and by patterning via bone morphogenetic receptors including activin, other bone morphogenetic protein receptors, transforming growth factor-β receptors, all part of a receptor superfamily. This superfamily interacts with receptors for additional signals in bone differentiation. Important features of the osteoblast environment were established using recent tools including osteoblast differentiation in vitro. Osteoblasts deposit matrix protein, over 90% type I collagen, in lamellae with orientation alternating parallel or orthogonal to the main stress axis of the bone. Into this organic matrix, mineral is deposited as hydroxyapatite. Mineral matrix matures from amorphous to crystalline hydroxyapatite. This process includes at least two-phase changes of the calcium-phosphate mineral as well as intermediates involving tropocollagen fibrils to form the bone composite. Beginning with initiation of mineral deposition, there is uncertainty regarding cardinal processes, but the driving force is not merely exceeding the calcium-phosphate solubility product. It occurs behind a epithelial-like layer of osteoblasts, which generate phosphate and remove protons liberated during calcium-phosphate salt deposition. The forming bone matrix is discontinuous from the general extracellular fluid. Required adjustment of ionic concentrations and water removal from bone matrix are important details remaining to be addressed.
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Affiliation(s)
| | - Harry C Blair
- Veterans Affairs Medical Center, Pittsburgh, Pennsylvania.,Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Donna Beer Stolz
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Vladimir Riazanski
- Department of Neurobiology, Pharmacology, and Physiology, University of Chicago, Chicago, Illinois
| | - Evan C Ray
- Renal Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Irina L Tourkova
- Veterans Affairs Medical Center, Pittsburgh, Pennsylvania.,Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Deborah J Nelson
- Department of Neurobiology, Pharmacology, and Physiology, University of Chicago, Chicago, Illinois
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38
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Xie Y, Zhang L, Xiong Q, Gao Y, Ge W, Tang P. Bench-to-bedside strategies for osteoporotic fracture: From osteoimmunology to mechanosensation. Bone Res 2019; 7:25. [PMID: 31646015 PMCID: PMC6804735 DOI: 10.1038/s41413-019-0066-7] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 06/20/2019] [Accepted: 06/21/2019] [Indexed: 12/16/2022] Open
Abstract
Osteoporosis is characterized by a decrease in bone mass and strength, rendering people prone to osteoporotic fractures caused by low-energy forces. The primary treatment strategy for osteoporotic fractures is surgery; however, the compromised and comminuted bones in osteoporotic fracture sites are not conducive to optimum reduction and rigid fixation. In addition, these patients always exhibit accompanying aging-related disorders, including high inflammatory status, decreased mechanical loading and abnormal skeletal metabolism, which are disadvantages for fracture healing around sites that have undergone orthopedic procedures. Since the incidence of osteoporosis is expected to increase worldwide, orthopedic surgeons should pay more attention to comprehensive strategies for improving the poor prognosis of osteoporotic fractures. Herein, we highlight the molecular basis of osteoimmunology and bone mechanosensation in different healing phases of elderly osteoporotic fractures, guiding perioperative management to alleviate the unfavorable effects of insufficient mechanical loading, high inflammatory levels and pathogen infection. The well-informed pharmacologic and surgical intervention, including treatment with anti-inflammatory drugs and sufficient application of antibiotics, as well as bench-to-bedside strategies for bone augmentation and hardware selection, should be made according to a comprehensive understanding of bone biomechanical properties in addition to the remodeling status of osteoporotic bones, which is necessary for creating proper biological and mechanical environments for bone union and remodeling. Multidisciplinary collaboration will facilitate the improvement of overall osteoporotic care and reduction of secondary fracture incidence.
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Affiliation(s)
- Yong Xie
- Department of Orthopedics, Chinese PLA General Hospital, Beijing, China
| | - Licheng Zhang
- Department of Orthopedics, Chinese PLA General Hospital, Beijing, China
| | - Qi Xiong
- Department of Oncology, Chinese PLA General Hospital, Beijing, China
| | - Yanpan Gao
- State Key Laboratory of Medical Molecular Biology and Department of Immunology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Beijing, China
| | - Wei Ge
- State Key Laboratory of Medical Molecular Biology and Department of Immunology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Beijing, China
| | - Peifu Tang
- Department of Orthopedics, Chinese PLA General Hospital, Beijing, China
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39
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Werner SL, Sharma R, Woodruff K, Horn D, Harris SE, Gorin Y, Lee DY, Hua R, Gu S, Fajardo RJ, Habib SL, Jiang JX. CSF-1 in Osteocytes Inhibits Nox4-mediated Oxidative Stress and Promotes Normal Bone Homeostasis. JBMR Plus 2019; 4:e10080. [PMID: 32666016 DOI: 10.1002/jbm4.10080] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 08/28/2018] [Accepted: 08/30/2018] [Indexed: 12/12/2022] Open
Abstract
CSF-1 is a key factor in regulating bone remodeling; osteocytes express CSF-1 and its receptor. Viable osteocytes are essential for bone remodeling through cell-cell contact and secretion of factors that regulate osteoblasts and osteoclasts. Increased oxidative stress contributes to osteocyte death and correlates with bone loss during aging. The NADPH oxidase Nox4 is a major source of ROS in bone. CSF-1 decreases Nox4, suggesting that CSF-1 protects against oxidative stress. Here, we show that osteocyte apoptosis previously reported in our global CSF-1KO mice is associated with increased Nox4, as well as 4-HNE expression in osteocytes. Osteocytes isolated from CSF-1KO mice were less viable and showed increased intracellular ROS, elevated NADPH oxidase activity/Nox4 protein, activation of mTOR/S6K, and downstream apoptosis signals compared with WT osteocytes. Nox4 expression was also increased in CSF-1KO osteocytes and colocalized with MitoTracker Red in mitochondria. Notably, CSF-1 inhibited Nox4 expression and apoptosis cascade signals. In additional studies, shNox4 decreased these signals in CSF-1KO osteocytes, whereas overexpression of Nox4 in WT osteocytes activated the apoptosis pathway. To determine the role of CSF-1 in osteocytes, DMP1Cre-CSF-1cKO (CSF-1cKO) mice that lack CSF-1 in osteocytes/late osteoblasts were developed. Osteocyte defects in CSF-1cKO mice overlapped with those in CSF-1KO mice, including increased apoptosis, Nox4, and 4-HNE-expressing osteocytes. CSF-1cKO mice showed unbalanced cancellous bone remodeling with decreased bone formation and resorption. Continued exposure to high Nox4/ROS levels may further compromise bone formation and predispose to bone loss and skeletal fragility. Taken together, our findings suggest a novel link between CSF-1, Nox4-derived ROS, and osteocyte survival/function that is crucial for osteocyte-mediated bone remodeling. Results reveal new mechanisms by which CSF-1/oxidative stress regulate osteocyte homeostasis, which may lead to therapeutic strategies to improve skeletal health in aging. © 2018 American Society for Bone and Mineral Research.
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Affiliation(s)
- Sherry L Werner
- Department of Pathology University of Texas Health Science Center at San Antonio TX USA
| | - Ramaswamy Sharma
- Department of Cell Systems and Anatomy University of Texas Health Science Center at San Antonio TX USA
| | - Kathleen Woodruff
- Department of Pathology University of Texas Health Science Center at San Antonio TX USA
| | - Diane Horn
- Department of Pathology University of Texas Health Science Center at San Antonio TX USA
| | - Stephen E Harris
- Department of Periodontics University of Texas Health Science Center at San Antonio TX USA
| | - Yves Gorin
- Department of Medicine/Nephrology University of Texas Health Science Center at San Antonio TX USA
| | - Doug-Yoon Lee
- Department of Medicine/Nephrology University of Texas Health Science Center at San Antonio TX USA
| | - Rui Hua
- Department of Biochemistry and Structural Biology University of Texas Health Science Center at San Antonio TX USA
| | - Sumin Gu
- Department of Biochemistry and Structural Biology University of Texas Health Science Center at San Antonio TX USA
| | - Roberto J Fajardo
- Department of Orthopedics University of Texas Health Science Center at San Antonio TX USA
| | - Samy L Habib
- South Texas Veterans Health Care and Department of Cell Systems and Anatomy University of Texas Health Science Center at San Antonio TX USA
| | - Jean X Jiang
- Department of Biochemistry and Structural Biology University of Texas Health Science Center at San Antonio TX USA
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40
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Connexin 43 hemichannels protect bone loss during estrogen deficiency. Bone Res 2019; 7:11. [PMID: 31016065 PMCID: PMC6476886 DOI: 10.1038/s41413-019-0050-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 02/28/2019] [Accepted: 03/18/2019] [Indexed: 02/02/2023] Open
Abstract
Estrogen deficiency in postmenopausal women is a major cause of bone loss, resulting in osteopenia, osteoporosis, and a high risk for bone fracture. Connexin 43 (Cx43) hemichannels (HCs) in osteocytes play an important role in osteocyte viability, bone formation, and remodeling. We showed here that estrogen deficiency reduced Cx43 expression and HC function. To determine if functional HCs protect osteocytes and bone loss during estrogen deficiency, we adopted an ovariectomy model in wild-type (WT) and two transgenic Cx43 mice: R76W (dominant-negative mutant inhibiting only gap junction channels) and Cx43 Δ130–136 (dominant-negative mutant compromising both gap junction channels and HCs). The bone mineral density (BMD), bone structure, and histomorphometric changes of cortical and trabecular bones after ovariectomy were investigated. Our results showed that the Δ130–136 transgenic cohort had greatly decreased vertebral trabecular bone mass compared to WT and R76W mice, associated with a significant increase in the number of apoptotic osteocyte and empty lacunae. Moreover, osteoclast surfaces in trabecular and cortical bones were increased after ovariectomy in the R76W and WT mice, respectively, but not in ∆130–136 mice. These data demonstrate that impairment of Cx43 HCs in osteocytes accelerates vertebral trabecular bone loss and increase in osteocyte apoptosis, and further suggest that Cx43 HCs in osteocytes protect trabecular bone against catabolic effects due to estrogen deficiency. Channels that form between cells and their extracellular environment help protect bone tissue from the damage wrought by low estrogen levels, a major cause of bone loss in post-menopausal women. Jean Jiang from the UT Health San Antonio and colleagues showed that depleting the estrogen hormone in mouse bone cells reduced levels of connexin 43 and impaired the protein’s ability to forms pores known as ‘hemichannels’. The researchers surgically removed the ovaries of various mouse strains to induce estrogen deficiencies. They found that transgenic mice without working hemichannels had reduced bone mass compared to normal mice or mice that could make hemichannels but lacked the ability for those channels to come together to form complete passageways. The findings highlight the importance of connexin 43 hemichannels in protecting bone tissue against osteoporosis.
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41
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Chen Y, Chen M, Xue T, Li G, Wang D, Shang P, Jiang JX, Xu H. Osteocytic connexin 43 channels affect fracture healing. J Cell Physiol 2019; 234:19824-19832. [PMID: 30980397 DOI: 10.1002/jcp.28581] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2018] [Revised: 02/24/2019] [Accepted: 03/05/2019] [Indexed: 12/27/2022]
Abstract
The cross-talk between cells is very critical for moving forward fracture healing in an orderly manner. Connexin (Cx) 43-formed gap junctions and hemichannels mediate the communication between adjacent cells and cells and extracellular environment. Loss of Cx43 in osteoblasts/osteocytes results in delayed fracture healing. For investigating the role of two channels in osteocytes in bone repair, two transgenic mouse models with Cx43 dominant negative mutants driven by a 10 kb-DMP1 promoter were generated: R76W (gap junctions are blocked, whereas hemichannels are promoted) and Δ130-136 (both gap junctions and hemichannels are blocked). R76W mice (promotion of hemichannels) showed a significant increase of new bone formation, whereas delayed osteoclastogenesis and healing was observed in Δ130-136 (impairment of gap junctions), but not in R76W mice (hemichannel promotion may recover the delay). These results suggest that gap junctions and hemichannels play some similar and cooperative roles in bone repair.
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Affiliation(s)
- Yunhe Chen
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an, Shaanxi, China
| | - Meng Chen
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an, Shaanxi, China
| | - Tong Xue
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an, Shaanxi, China
| | - Guobin Li
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an, Shaanxi, China
| | - Dongen Wang
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an, Shaanxi, China
| | - Peng Shang
- Key Laboratory for Space Bioscience and Biotechnology, Research & Development Institute in Shenzhen, Northwestern Polytechnical UniversityShenzhen, Shenzhen, Guangdong, China
| | - Jean X Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas
| | - Huiyun Xu
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an, Shaanxi, China.,Key Laboratory for Space Bioscience and Biotechnology, Research & Development Institute in Shenzhen, Northwestern Polytechnical UniversityShenzhen, Shenzhen, Guangdong, China.,Research Center of Special Environmental Biomechanics & Medical Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi, China
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42
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Sherk VD, Rosen CJ. Senescent and apoptotic osteocytes and aging: Exercise to the rescue? Bone 2019; 121:255-258. [PMID: 30735796 PMCID: PMC6459182 DOI: 10.1016/j.bone.2019.02.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 02/04/2019] [Accepted: 02/05/2019] [Indexed: 12/11/2022]
Abstract
Osteocytes are the most prevalent cell in the skeleton and are the master regulator of bone remodeling. Despite the understanding that osteocytes have a multiyear lifespan, and some factors induce apoptosis in osteocytes, much less is understood about the induction and consequences of osteocyte senescence. Filling these gaps in knowledge will provide novel approaches to slowing age-related bone loss and preventing fragility fractures. The purpose of this review is to examine the roles of senescence and apoptosis in osteocytes in age-related bone loss. Based on evidence that exercise can prevent senescence in skeletal muscle, we provide a novel hypothesis by which exercise can prolong skeletal health.
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Affiliation(s)
- Vanessa D Sherk
- Department of Medicine, Division of Endocrinology, Metabolism, and Diabetes, University of Colorado Anschutz Medical Campus, Aurora, CO, United States of America.
| | - Clifford J Rosen
- Tufts University School of Medicine, Maine Medical Center Research Institute Scarborough, ME, United States of America
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43
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Xing L, Yang T, Cui S, Chen G. Connexin Hemichannels in Astrocytes: Role in CNS Disorders. Front Mol Neurosci 2019; 12:23. [PMID: 30787868 PMCID: PMC6372977 DOI: 10.3389/fnmol.2019.00023] [Citation(s) in RCA: 122] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 01/21/2019] [Indexed: 12/19/2022] Open
Abstract
In the central nervous system (CNS), astrocytes form networks interconnected by gap junctions made from connexins of the subtypes Cx30 and Cx43. When unopposed by an adjoining hemichannel, astrocytic connexins can act as hemichannels to control the release of small molecules such as ATP and glutamate into the extracellular space. Accruing evidence indicates that astrocytic connexins are crucial for the coordination and maintenance of physiologic CNS activity. Here we provide an update on the role of astrocytic connexins in neurodegenerative disorders, glioma, and ischemia. In addition, we address the regulation of Cx43 in chronic pain.
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Affiliation(s)
- LingYan Xing
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China
| | - Tuo Yang
- Department of Hand Surgery, China-Japan Union Hospital of Jilin University, Changchun, China
| | - ShuSen Cui
- Department of Hand Surgery, China-Japan Union Hospital of Jilin University, Changchun, China
| | - Gang Chen
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China.,Department of Anesthesiology, Affiliated Hospital of Nantong University, Nantong, China
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44
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Transforming growth factor-β1 up-regulates connexin43 expression in osteocytes via canonical Smad-dependent signaling pathway. Biosci Rep 2018; 38:BSR20181678. [PMID: 30482881 PMCID: PMC6294634 DOI: 10.1042/bsr20181678] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Revised: 11/20/2018] [Accepted: 11/23/2018] [Indexed: 02/05/2023] Open
Abstract
Connexin 43 (Cx43)-mediated gap junctional intercellular communication (GJIC) has been shown to be important in regulating multiple functions of bone cells. Transforming growth factor-β1 (TGF-β1) exhibited controversial effects on the expression of Cx43 in different cell types. To date, the effect of TGF-β1 on the Cx43 expression of osteocytes is still unknown. In the present study, we detected the expression of TGF-β1 in osteocytes and bone tissue, and then used recombinant mouse TGF-β1 to elucidate its effect on gap junctions (GJs) of osteocytes. Our data indicated that TGF-β1 up-regulated both mRNA and protein expression of Cx43 in osteocytes. Together with down-regulation of Cx43 expression after being treated with TGF-β type I receptor inhibitor Repsox, we deduced that TGF-β1 can positively regulate Cx43 expression in osteocytes. Thus we next focussed on the downstream signals of TGF-β and found that TGF-β1-mediated smads, Smad3 and Smad4, to translocate into nucleus. These translocated signal proteins bind to the promoter of Gja1 which was responsible for the changed expression of Cx43. The present study provides evidence that TGF-β1 can enhance GJIC between osteocytes through up-regulating Cx43 expression and the underlying mechanism involved in the activation of Smad-dependent pathway.
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45
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Zhu Y, Ma Y, Elefteriou F. Cortical bone is an extraneuronal site of norepinephrine uptake in adult mice. Bone Rep 2018; 9:188-198. [PMID: 30581894 PMCID: PMC6296164 DOI: 10.1016/j.bonr.2018.11.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 10/23/2018] [Accepted: 11/21/2018] [Indexed: 12/30/2022] Open
Abstract
The sympathetic nervous system is a major efferent pathway through which the central nervous system controls the function of peripheral organs. Genetic and pharmacologic evidence in mice indicated that stimulation of the β2 adrenergic receptor (β2AR) in osteoblasts promotes bone loss, leading to the paradigm that high sympathetic nervous activity is deleterious to bone mass. However, considerably less data exist to understand the putative impact of endogenous norepinephrine (NE), released by sympathetic nerves, on bone homeostasis. In this study, we investigated the in vivo expression and activity of the norepinephrine transporter (NET), a membrane pump known to actively uptake NE from the extracellular space in presynaptic neurons. Consistent with previously published in vitro data showing NET uptake activity in differentiated osteoblasts, we were able to detect active NET-specific NE uptake in the mouse cortical bone compartment in vivo. This uptake was the highest in young mice and accordingly with an age-related reduction in NET uptake, NE bone content increased whereas Net RNA and protein expression decreased with age. Histologically, NET expression in adult mouse bones was detected in osteocytes via immunofluorescence. Lastly, taking advantage of tissue-specific fluorescent reporter mice, we used CLARITY imaging and light sheet microscopy to visualize the 3D distribution of sympathetic fibers in whole mount preparations of bone tissues. These analyses allowed us to detect tyrosine hydroxylase (TH)-positive sympathetic nerve fibers penetrating the cortical bone, where NET+ osteocytes reside. Together, these in vitro results support the existence of an age-dependent extraneuronal and osteocytic function of NET with potential to buffer the bone catabolic action of endogenous NE released by sympathetic nerves in vivo.
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Affiliation(s)
- Yuantee Zhu
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, United States
- Department of Orthopedics, Baylor College of Medicine, Houston, TX, United States
| | - Yun Ma
- Department of Orthopedics, Baylor College of Medicine, Houston, TX, United States
| | - Florent Elefteriou
- Department of Orthopedics, Baylor College of Medicine, Houston, TX, United States
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States
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46
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Lopes D, Martins-Cruz C, Oliveira MB, Mano JF. Bone physiology as inspiration for tissue regenerative therapies. Biomaterials 2018; 185:240-275. [PMID: 30261426 PMCID: PMC6445367 DOI: 10.1016/j.biomaterials.2018.09.028] [Citation(s) in RCA: 200] [Impact Index Per Article: 33.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 09/15/2018] [Accepted: 09/17/2018] [Indexed: 12/14/2022]
Abstract
The development, maintenance of healthy bone and regeneration of injured tissue in the human body comprise a set of intricate and finely coordinated processes. However, an analysis of current bone regeneration strategies shows that only a small fraction of well-reported bone biology aspects has been used as inspiration and transposed into the development of therapeutic products. Specific topics that include inter-scale bone structural organization, developmental aspects of bone morphogenesis, bone repair mechanisms, role of specific cells and heterotypic cell contact in the bone niche (including vascularization networks and immune system cells), cell-cell direct and soluble-mediated contact, extracellular matrix composition (with particular focus on the non-soluble fraction of proteins), as well as mechanical aspects of native bone will be the main reviewed topics. In this Review we suggest a systematic parallelization of (i) fundamental well-established biology of bone, (ii) updated and recent advances on the understanding of biological phenomena occurring in native and injured tissue, and (iii) critical discussion of how those individual aspects have been translated into tissue regeneration strategies using biomaterials and other tissue engineering approaches. We aim at presenting a perspective on unexplored aspects of bone physiology and how they could be translated into innovative regeneration-driven concepts.
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Affiliation(s)
- Diana Lopes
- Department of Chemistry, CICECO - Aveiro Institute of Materials, University of Aveiro, Campus Universitário de Santiago,, 3810 193 Aveiro, Portugal
| | - Cláudia Martins-Cruz
- Department of Chemistry, CICECO - Aveiro Institute of Materials, University of Aveiro, Campus Universitário de Santiago,, 3810 193 Aveiro, Portugal
| | - Mariana B Oliveira
- Department of Chemistry, CICECO - Aveiro Institute of Materials, University of Aveiro, Campus Universitário de Santiago,, 3810 193 Aveiro, Portugal.
| | - João F Mano
- Department of Chemistry, CICECO - Aveiro Institute of Materials, University of Aveiro, Campus Universitário de Santiago,, 3810 193 Aveiro, Portugal.
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47
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Therapeutic Targeting of Connexin Channels: New Views and Challenges. Trends Mol Med 2018; 24:1036-1053. [PMID: 30424929 DOI: 10.1016/j.molmed.2018.10.005] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 10/09/2018] [Accepted: 10/11/2018] [Indexed: 12/22/2022]
Abstract
Connexins, in particular connexin 43 (Cx43), function as gap junction channels (GJCs) and hemichannels (HCs). Only recently, specific tools have been developed to study their pleiotropic functions. Based on various protein interaction sites, distinct connexin-mimetic peptides have been established that enable discrimination between the function of HCs and GJCs. Although the precise mechanism of action of most of these peptides is still a matter of debate, an increasing number of studies report on important effects of those compounds in disease models. In this review, we summarize the structure, life cycle, and the most important physiological and pathological functions of both connexin GJCs and HCs. We provide a critical overview on the use of connexin-targeting peptides, in particular targeting Cx43, with a special focus on the remaining questions and hurdles to be taken in the research field of connexin channels.
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48
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Tanaka T, Hoshijima M, Sunaga J, Nishida T, Hashimoto M, Odagaki N, Osumi R, Aadachi T, Kamioka H. Analysis of Ca 2+ response of osteocyte network by three-dimensional time-lapse imaging in living bone. J Bone Miner Metab 2018; 36:519-528. [PMID: 29027020 DOI: 10.1007/s00774-017-0868-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 08/30/2017] [Indexed: 11/26/2022]
Abstract
Osteocytes form a three-dimensional (3D) cellular network within the mineralized bone matrix. The cellular network has important roles in mechanosensation and mechanotransduction related to bone homeostasis. We visualized the embedded osteocyte network in chick calvariae and observed the flow-induced Ca2+ signaling in osteocytes using 3D time-lapse imaging. In response to the flow, intracellular Ca2+ ([Ca2+]i) significantly increased in developmentally mature osteocytes in comparison with young osteocytes in the bone matrix. To investigate the differences in response between young and developmentally mature osteocytes in detail, we evaluated the expression of osteocyte-related genes using the osteocyte-like cell line MLO-Y4, which was 3D-cultured within type I collagen gels. We found that the c-Fos, Cx43, Panx3, Col1a1, and OCN mRNA levels significantly increased on day 15 in comparison with day 7. These findings indicate that developmentally mature osteocytes are more responsive to mechanical stress than young osteocytes and have important functions in bone formation and remodeling.
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Affiliation(s)
- Tomoyo Tanaka
- Department of Orthodontics, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 5-1 Shikata-cho, 2-chome, Kitaku, Okayama, 700-8525, Japan
| | - Mitsuhiro Hoshijima
- Department of Orthodontics, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 5-1 Shikata-cho, 2-chome, Kitaku, Okayama, 700-8525, Japan
- Advanced Research Center for Oral and Craniofacial Sciences, Dental School, Okayama University, Okayama, Japan
| | - Junko Sunaga
- Laboratory of Biomechanics, Department of Biosystems Science, Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto, Japan
| | - Takashi Nishida
- Department of Biochemistry and Molecular Dentistry, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | - Mana Hashimoto
- Department of Orthodontics, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 5-1 Shikata-cho, 2-chome, Kitaku, Okayama, 700-8525, Japan
| | - Naoya Odagaki
- Department of Orthodontics, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 5-1 Shikata-cho, 2-chome, Kitaku, Okayama, 700-8525, Japan
| | - Ryuta Osumi
- Department of Orthodontics, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 5-1 Shikata-cho, 2-chome, Kitaku, Okayama, 700-8525, Japan
| | - Taiji Aadachi
- Laboratory of Biomechanics, Department of Biosystems Science, Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto, Japan
| | - Hiroshi Kamioka
- Department of Orthodontics, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 5-1 Shikata-cho, 2-chome, Kitaku, Okayama, 700-8525, Japan.
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49
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Gago-Fuentes R, Bechberger JF, Varela-Eirin M, Varela-Vazquez A, Acea B, Fonseca E, Naus CC, Mayan MD. The C-terminal domain of connexin43 modulates cartilage structure via chondrocyte phenotypic changes. Oncotarget 2018; 7:73055-73067. [PMID: 27682878 PMCID: PMC5341963 DOI: 10.18632/oncotarget.12197] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 09/16/2016] [Indexed: 12/13/2022] Open
Abstract
Chondrocytes in cartilage and bone cells population express connexin43 (Cx43) and gap junction intercellular communication (GJIC) is essential to synchronize cells for coordinated electrical, mechanical, metabolic and chemical communication in both tissues. Reduced Cx43 connectivity decreases chondrocyte differentiation and defective Cx43 causes skeletal defects. The carboxy terminal domain (CTD) of Cx43 is located in the cytoplasmic side and is key for protein functions. Here we demonstrated that chondrocytes from the CTD-deficient mice, K258stop/Cx43KO and K258stop/K258stop, have reduced GJIC, increased rates of proliferation and reduced expression of collagen type II and proteoglycans. We observed that CTD-truncated mice were significantly smaller in size. Together these results demonstrated that the deletion of the CTD negatively impacts cartilage structure and normal chondrocyte phenotype. These findings suggest that the proteolytic cleavage of the CTD under pathological conditions, such as under the activation of metalloproteinases during tissue injury or inflammation, may account for the deleterious effects of Cx43 in cartilage and bone disorders such as osteoarthritis.
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Affiliation(s)
- Raquel Gago-Fuentes
- CellCOM-SB Research Group, Instituto de Investigación Biomédica de A Coruña (INIBIC), CH-Universitario A Coruña (XXIAC), University of A Coruña, Servizo Galego de Saúde (SERGAS), Xubias de Arriba, 84 15006 A Coruña, Spain
| | - John F Bechberger
- Department of Cellular and Physiological Sciences, The Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z3
| | - Marta Varela-Eirin
- CellCOM-SB Research Group, Instituto de Investigación Biomédica de A Coruña (INIBIC), CH-Universitario A Coruña (XXIAC), University of A Coruña, Servizo Galego de Saúde (SERGAS), Xubias de Arriba, 84 15006 A Coruña, Spain
| | - Adrian Varela-Vazquez
- CellCOM-SB Research Group, Instituto de Investigación Biomédica de A Coruña (INIBIC), CH-Universitario A Coruña (XXIAC), University of A Coruña, Servizo Galego de Saúde (SERGAS), Xubias de Arriba, 84 15006 A Coruña, Spain
| | - Benigno Acea
- CellCOM-SB Research Group, Instituto de Investigación Biomédica de A Coruña (INIBIC), CH-Universitario A Coruña (XXIAC), University of A Coruña, Servizo Galego de Saúde (SERGAS), Xubias de Arriba, 84 15006 A Coruña, Spain
| | - Eduardo Fonseca
- CellCOM-SB Research Group, Instituto de Investigación Biomédica de A Coruña (INIBIC), CH-Universitario A Coruña (XXIAC), University of A Coruña, Servizo Galego de Saúde (SERGAS), Xubias de Arriba, 84 15006 A Coruña, Spain
| | - Christian C Naus
- Department of Cellular and Physiological Sciences, The Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z3
| | - Maria D Mayan
- CellCOM-SB Research Group, Instituto de Investigación Biomédica de A Coruña (INIBIC), CH-Universitario A Coruña (XXIAC), University of A Coruña, Servizo Galego de Saúde (SERGAS), Xubias de Arriba, 84 15006 A Coruña, Spain
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50
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Yu K, Sellman DP, Bahraini A, Hagan ML, Elsherbini A, Vanpelt KT, Marshall PL, Hamrick MW, McNeil A, McNeil PL, McGee-Lawrence ME. Mechanical loading disrupts osteocyte plasma membranes which initiates mechanosensation events in bone. J Orthop Res 2018; 36:653-662. [PMID: 28755471 PMCID: PMC5788741 DOI: 10.1002/jor.23665] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 07/24/2017] [Indexed: 02/04/2023]
Abstract
Osteocytes sense loading in bone, but their mechanosensation mechanisms remain poorly understood. Plasma membrane disruptions (PMD) develop with loading under physiological conditions in many cell types (e.g., myocytes, endothelial cells). These PMD foster molecular flux across cell membranes that promotes tissue adaptation, but this mechanosensation mechanism had not been explored in osteocytes. Our goal was to investigate whether PMD occur and initiate consequent mechanotransduction in osteocytes during physiological loading. We found that osteocytes experience PMD during in vitro (fluid flow) and in vivo (treadmill exercise) mechanical loading, in proportion to the level of stress experienced. In fluid flow studies, osteocyte PMD preferentially formed with rapid as compared to gradual application of loading. In treadmill studies, osteocyte PMD increased with loading in weight bearing locations (tibia), but this trend was not seen in non-weight bearing locations (skull). PMD initiated osteocyte mechanotransduction including calcium signaling and expression of c-fos, and repair rates of these PMD could be enhanced or inhibited pharmacologically to alter downstream mechanotransduction and osteocyte survival. PMD may represent a novel mechanosensation pathway in bone and a target for modifying skeletal adaptation signaling in osteocytes. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:653-662, 2018.
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Affiliation(s)
- Kanglun Yu
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1120 15 St, Augusta, GA
| | - David P. Sellman
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1120 15 St, Augusta, GA
| | - Anoosh Bahraini
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1120 15 St, Augusta, GA
| | - Mackenzie L. Hagan
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1120 15 St, Augusta, GA
| | - Ahmed Elsherbini
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1120 15 St, Augusta, GA
| | - Kayce T. Vanpelt
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1120 15 St, Augusta, GA
| | - Peyton L. Marshall
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1120 15 St, Augusta, GA
| | - Mark W. Hamrick
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1120 15 St, Augusta, GA
| | - Anna McNeil
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1120 15 St, Augusta, GA
| | - Paul L. McNeil
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1120 15 St, Augusta, GA
| | - Meghan E. McGee-Lawrence
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1120 15 St, Augusta, GA
- Department of Orthopaedic Surgery, Medical College of Georgia, Augusta University, 1120 15 St, Augusta, GA
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