1
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Steltzer SS, Abraham AC, Killian ML. Interfacial Tissue Regeneration with Bone. Curr Osteoporos Rep 2024; 22:290-298. [PMID: 38358401 PMCID: PMC11060924 DOI: 10.1007/s11914-024-00859-1] [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: 01/29/2024] [Indexed: 02/16/2024]
Abstract
PURPOSE OF REVIEW Interfacial tissue exists throughout the body at cartilage-to-bone (osteochondral interface) and tendon-to-bone (enthesis) interfaces. Healing of interfacial tissues is a current challenge in regenerative approaches because the interface plays a critical role in stabilizing and distributing the mechanical stress between soft tissues (e.g., cartilage and tendon) and bone. The purpose of this review is to identify new directions in the field of interfacial tissue development and physiology that can guide future regenerative strategies for improving post-injury healing. RECENT FINDINGS Cues from interfacial tissue development may guide regeneration including biological cues such as cell phenotype and growth factor signaling; structural cues such as extracellular matrix (ECM) deposition, ECM, and cell alignment; and mechanical cues such as compression, tension, shear, and the stiffness of the cellular microenvironment. In this review, we explore new discoveries in the field of interfacial biology related to ECM remodeling, cellular metabolism, and fate. Based on emergent findings across multiple disciplines, we lay out a framework for future innovations in the design of engineered strategies for interface regeneration. Many of the key mechanisms essential for interfacial tissue development and adaptation have high potential for improving outcomes in the clinic.
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Affiliation(s)
- Stephanie S Steltzer
- Department of Orthopaedic Surgery, University of Michigan Medical School, Ann Arbor, MI, USA
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Adam C Abraham
- Department of Orthopaedic Surgery, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Megan L Killian
- Department of Orthopaedic Surgery, University of Michigan Medical School, Ann Arbor, MI, USA.
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA.
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Kamalitdinov TB, Fujino K, Keith Lang S, Jiang X, Madi R, Evans MK, Zgonis MH, Kuntz AF, Dyment NA. Targeting the hedgehog signaling pathway to improve tendon-to-bone integration. Osteoarthritis Cartilage 2023; 31:1202-1213. [PMID: 37146960 PMCID: PMC10524548 DOI: 10.1016/j.joca.2023.04.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 04/24/2023] [Accepted: 04/29/2023] [Indexed: 05/07/2023]
Abstract
OBJECTIVE While the role of hedgehog (Hh) signaling in promoting zonal fibrocartilage production during development is well-established, whether this pathway can be leveraged to improve tendon-to-bone repair in adults is unknown. Our objective was to genetically and pharmacologically stimulate the Hh pathway in cells that give rise to zonal fibrocartilaginous attachments to promote tendon-to-bone integration. DESIGN Hh signaling was stimulated genetically via constitutive Smo (SmoM2 construct) activation of bone marrow stromal cells or pharmacologically via systemic agonist delivery to mice following anterior cruciate ligament reconstruction (ACLR). To assess tunnel integration, we measured mineralized fibrocartilage (MFC) formation in these mice 28 days post-surgery and performed tunnel pullout testing. RESULTS Hh pathway-related genes increased in cells forming the zonal attachments in wild-type mice. Both genetic and pharmacologic stimulation of the Hh pathway increased MFC formation and integration strength 28 days post-surgery. We next conducted studies to define the role of Hh in specific stages of the tunnel integration process. We found Hh agonist treatment increased the proliferation of the progenitor pool in the first week post-surgery. Additionally, genetic stimulation led to continued MFC production in the later stages of the integration process. These results indicate that Hh signaling plays an important biphasic role in cell proliferation and differentiation towards fibrochondrocytes following ACLR. CONCLUSION This study reveals a biphasic role for Hh signaling during the tendon-to-bone integration process after ACLR. In addition, the Hh pathway is a promising therapeutic target to improve tendon-to-bone repair outcomes.
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Affiliation(s)
- Timur B Kamalitdinov
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, USA; Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA
| | - Keitaro Fujino
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, USA; Osaka Medical and Pharmaceutical University, Takatsuki, Osaka Prefecture, Japan
| | - Sinaia Keith Lang
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, USA; Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - Xi Jiang
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, USA
| | - Rashad Madi
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, USA
| | - Mary Kate Evans
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, USA; Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA
| | - Miltiadis H Zgonis
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, USA
| | - Andrew F Kuntz
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, USA
| | - Nathaniel A Dyment
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, USA; Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA.
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Wernlé KK, Sonnenfelt MA, Leek CC, Ganji E, Sullivan AL, Offutt C, Shuff J, Ornitz DM, Killian ML. Loss of Fgfr1 and Fgfr2 in Scleraxis-lineage cells leads to enlarged bone eminences and attachment cell death. Dev Dyn 2023; 252:1180-1188. [PMID: 37212424 PMCID: PMC10524747 DOI: 10.1002/dvdy.600] [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: 05/03/2022] [Revised: 04/03/2023] [Accepted: 04/10/2023] [Indexed: 05/23/2023] Open
Abstract
BACKGROUND Tendons and ligaments attach to bone are essential for joint mobility and stability in vertebrates. Tendon and ligament attachments (ie, entheses) are found at bony protrusions (ie, eminences), and the shape and size of these protrusions depend on both mechanical forces and cellular cues during growth. Tendon eminences also contribute to mechanical leverage for skeletal muscle. Fibroblast growth factor receptor (FGFR) signaling plays a critical role in bone development, and Fgfr1 and Fgfr2 are highly expressed in the perichondrium and periosteum of bone where entheses can be found. RESULTS AND CONCLUSIONS We used transgenic mice for combinatorial knockout of Fgfr1 and/or Fgfr2 in tendon/attachment progenitors (ScxCre) and measured eminence size and shape. Conditional deletion of both, but not individual, Fgfr1 and Fgfr2 in Scx progenitors led to enlarged eminences in the postnatal skeleton and shortening of long bones. In addition, Fgfr1/Fgfr2 double conditional knockout mice had more variation collagen fibril size in tendon, decreased tibial slope, and increased cell death at ligament attachments. These findings identify a role for FGFR signaling in regulating growth and maintenance of tendon/ligament attachments and the size and shape of bony eminences.
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Affiliation(s)
- Kendra K. Wernlé
- Department of Biomedical Engineering, University of Delaware, 150 Academy St, Newark, Delaware, 19716
- Institute of Anatomy, University of Zürich, Winterthurerstrasse 190, Zürich, Switzerland
| | - Michael A. Sonnenfelt
- Department of Biomedical Engineering, University of Delaware, 150 Academy St, Newark, Delaware, 19716
| | - Connor C. Leek
- Department of Biomedical Engineering, University of Delaware, 150 Academy St, Newark, Delaware, 19716
- Department of Orthopaedic Surgery, University of Michigan, 109 Zina Pitcher Pl, Ann Arbor, MI 48109
| | - Elahe Ganji
- Department of Biomedical Engineering, University of Delaware, 150 Academy St, Newark, Delaware, 19716
- Department of Orthopaedic Surgery, University of Michigan, 109 Zina Pitcher Pl, Ann Arbor, MI 48109
- Department of Mechanical Engineering, University of Delaware, 130 Academy St, Newark, DE 19716
| | - Anna Lia Sullivan
- Department of Biomedical Engineering, University of Delaware, 150 Academy St, Newark, Delaware, 19716
| | - Claudia Offutt
- Department of Biomedical Engineering, University of Delaware, 150 Academy St, Newark, Delaware, 19716
| | - Jordan Shuff
- Department of Biomedical Engineering, University of Delaware, 150 Academy St, Newark, Delaware, 19716
| | - David M. Ornitz
- Department of Developmental Biology, Washington University School of Medicine, 660 S. Euclid Avenue, St Louis, Missouri, 63110
| | - Megan L. Killian
- Department of Biomedical Engineering, University of Delaware, 150 Academy St, Newark, Delaware, 19716
- Department of Orthopaedic Surgery, University of Michigan, 109 Zina Pitcher Pl, Ann Arbor, MI 48109
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Liu Y, Liu S, Song Z, Chen D, Album Z, Green S, Deng X, Rodeo SA. GLI1 Deficiency Impairs the Tendon-Bone Healing after Anterior Cruciate Ligament Reconstruction: In Vivo Study Using Gli1-Transgenic Mice. J Clin Med 2023; 12:jcm12030999. [PMID: 36769647 PMCID: PMC9917856 DOI: 10.3390/jcm12030999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 12/31/2022] [Accepted: 01/05/2023] [Indexed: 01/31/2023] Open
Abstract
Hedgehog (Hh) signaling plays a fundamental role in the enthesis formation process and GLI-Kruppel family member GLI1 (Gli1) is a key downstream mediator. However, the role of Gli1 in tendon-bone healing after anterior cruciate ligament reconstruction (ACLR) is unknown. To evaluate the tendon-bone healing after ACLR in Gli1LacZ/LacZ (GLI1-NULL) mice, and compare Gli1LacZ/WT (GLI1-HET) and Gli1WT/WT wild type (WT) mice, a total of 45 mice, 15 mice each of GLI1-NULL, GLI1-HET and WT were used in this study. All mice underwent microsurgical ACLR at 12 weeks of age. Mice were euthanized at 4 weeks after surgery and were used for biomechanical testing, histological evaluation, and micro-CT analysis. The GLI1-NULL group had significantly lower biomechanical failure force, poorer histological healing, and lower BV/TV when compared with the WT and GLI1-HET groups. These significant differences were only observed at the femoral tunnel. Immunohistology staining showed positive expression of Indian hedgehog (IHH) and Patched 1(PTCH1) in all three groups, which indicated the activation of the Hh signal pathway. The GLI1 was negative in the GLI1-NULL group, validating the absence of GLI1 protein in these mice. These results proved that activation of the Hh signaling pathway occurs during ACL graft healing, and the function of Gli1 was necessary for tendon-bone healing. Healing in the femoral tunnel is more obviously impaired by Gli1 deficiency. Our findings provide further insight into the molecular mechanism of tendon-bone healing and suggest that Gli1 might represent a novel therapeutic target to improve tendon-bone healing after ACLR.
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Affiliation(s)
- Yake Liu
- Laboratory for Joint Tissue Repair and Regeneration, Orthopaedic Soft Tissue Research Program, Hospital for Special Surgery, New York, NY 10021, USA
- Department of Orthopedic, Affiliated Hospital of Nantong University, Nantong 226001, China
| | - Shaohua Liu
- Laboratory for Joint Tissue Repair and Regeneration, Orthopaedic Soft Tissue Research Program, Hospital for Special Surgery, New York, NY 10021, USA
| | - Zhe Song
- Laboratory for Joint Tissue Repair and Regeneration, Orthopaedic Soft Tissue Research Program, Hospital for Special Surgery, New York, NY 10021, USA
| | - Daoyun Chen
- Laboratory for Joint Tissue Repair and Regeneration, Orthopaedic Soft Tissue Research Program, Hospital for Special Surgery, New York, NY 10021, USA
| | - Zoe Album
- Laboratory for Joint Tissue Repair and Regeneration, Orthopaedic Soft Tissue Research Program, Hospital for Special Surgery, New York, NY 10021, USA
| | - Samuel Green
- Laboratory for Joint Tissue Repair and Regeneration, Orthopaedic Soft Tissue Research Program, Hospital for Special Surgery, New York, NY 10021, USA
| | - Xianghua Deng
- Laboratory for Joint Tissue Repair and Regeneration, Orthopaedic Soft Tissue Research Program, Hospital for Special Surgery, New York, NY 10021, USA
| | - Scott A. Rodeo
- Laboratory for Joint Tissue Repair and Regeneration, Orthopaedic Soft Tissue Research Program, Hospital for Special Surgery, New York, NY 10021, USA
- Correspondence:
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Hasan MR, Koskenranta A, Alakurtti K, Takatalo M, Rice DP. RAB23 regulates musculoskeletal development and patterning. Front Cell Dev Biol 2023; 11:1049131. [PMID: 36910145 PMCID: PMC9995984 DOI: 10.3389/fcell.2023.1049131] [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: 09/20/2022] [Accepted: 02/07/2023] [Indexed: 02/25/2023] Open
Abstract
RAB23 is a small GTPase which functions at the plasma membrane to regulate growth factor signaling. Mutations in RAB23 cause Carpenter syndrome, a condition that affects normal organogenesis and patterning. In this study, we investigate the role of RAB23 in musculoskeletal development and show that it is required for patella bone formation and for the maintenance of tendon progenitors. The patella is the largest sesamoid bone in mammals and plays a critical role during movement by providing structural and mechanical support to the knee. Rab23 -/- mice fail to form a patella and normal knee joint. The patella is formed from Sox9 and scleraxis (Scx) double-positive chondroprogenitor cells. We show that RAB23 is required for the specification of SOX9 and scleraxis double-positive patella chondroprogenitors during the formation of patella anlagen and the subsequent establishment of patellofemoral joint. We find that scleraxis and SOX9 expression are disrupted in Rab23 -/- mice, and as a result, development of the quadriceps tendons, cruciate ligaments, patella tendons, and entheses is either abnormal or lost. TGFβ-BMP signaling is known to regulate patella initiation and patella progenitor differentiation and growth. We find that the expression of TGFβR2, BMPR1, BMP4, and pSmad are barely detectable in the future patella site and in the rudimentary tendons and ligaments around the patellofemoral joint in Rab23 -/- mice. Also, we show that GLI1, SOX9, and scleraxis, which regulate entheses establishment and maturation, are weakly expressed in Rab23 -/- mice. Further analysis of the skeletal phenotype of Rab23 -/- mice showed a close resemblance to that of Tgfβ2 -/- mice, highlighting a possible role for RAB23 in regulating TGFβ superfamily signaling.
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Affiliation(s)
- Md Rakibul Hasan
- Orthodontics, Oral and Maxillofacial Diseases, University of Helsinki, Helsinki, Finland
| | - Anna Koskenranta
- Orthodontics, Oral and Maxillofacial Diseases, University of Helsinki, Helsinki, Finland
| | - Kirsi Alakurtti
- Orthodontics, Oral and Maxillofacial Diseases, University of Helsinki, Helsinki, Finland
| | - Maarit Takatalo
- Orthodontics, Oral and Maxillofacial Diseases, University of Helsinki, Helsinki, Finland
| | - David P Rice
- Orthodontics, Oral and Maxillofacial Diseases, University of Helsinki, Helsinki, Finland.,Helsinki University Hospital, Helsinki, Finland
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Wang Z, Ma C, Chen D, Haslett C, Xu C, Dong C, Wang X, Zheng M, Jing Y, Feng JQ. Tendon Cells Root Into (Instead of Attach to) Humeral Bone Head via Fibrocartilage-Enthesis. Int J Biol Sci 2023; 19:183-203. [PMID: 36594083 PMCID: PMC9760439 DOI: 10.7150/ijbs.79007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 09/24/2022] [Indexed: 11/24/2022] Open
Abstract
Large joints are composed of two closely linked cartilages: articular cartilage (AC; rich in type II collagen, a well-studied tissue) and fibrocartilaginous enthesis (FE; rich in type I collagen, common disorder sites of enthesopathy and sporting injuries, although receiving little attention). For many years, both cartilages were thought to be formed by chondrocytes, whereas tendon, which attaches to the humeral bone head, is primarily considered as a completely different connective tissue. In this study, we raised an unconventional hypothesis: tendon cells directly form FE via cell transdifferentiation. To test this hypothesis, we first qualitatively and quantitatively demonstrated distinct differences between AC and FE in cell morphology and cell distribution, mineralization status, extracellular matrix (ECM) contents, and critical ECM protein expression profiles using comprehensive approaches. Next, we traced the cell fate of tendon cells using ScxLin (a tendon specific Cre ScxCreERT2; R26R-tdTomato line) with one-time tamoxifen induction at early (P3) or young adult (P28) stages and harvested mice at different development ages, respectively. Our early tracing data revealed different growth events in tendon and FE: an initial increase but gradual decrease in the ScxLin tendon cells and a continuous expansion in the ScxLin FE cells. The young adult tracing data demonstrated continuous recruitment of ScxLin cells into FE expansion during P28 and P56. A separate tracing line, 3.2 Col 1Lin (a so-called "bone-specific" line), further confirmed the direct contribution of tendon cells for FE cell formation, which occurred in days but FE ECM maturation (including high levels of SOST, a potent Wnt signaling inhibitor) took weeks. Finally, loss of function data using diphtheria toxin fragment A (DTA) in ScxLin cells demonstrated a significant reduction of ScxLin cells in both tendons and FE cells, whereas the gain of function study (by stabilizing β-catenin in ScxLin tendon cells via one-time injection of tamoxifen at P3 and harvesting at P60) displayed great expansion of both ScxLin tendon and FE mass. Together, our studies demonstrated that fibrocartilage is an invaded enthesis likely originating from the tendon via a quick cell transdifferentiation mechanism with a lengthy ECM maturation process. The postnatally formed fibrocartilage roots into existing cartilage and firmly connects tendon and bone instead of acting as a simple attachment site as widely believed. We believe that this study will stimulate more intense exploring in this understudied area, especially for patients with enthesopathy and sporting injuries.
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Affiliation(s)
- Zheng Wang
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas 75246, USA
| | - Chi Ma
- Department of Orthopaedic Surgery, University of Texas Southwestern Medical Center, Dallas, TX, 75219, USA
| | - Diane Chen
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas 75246, USA
| | - Caitlin Haslett
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas 75246, USA
| | - Chunmei Xu
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas 75246, USA
| | - Changchun Dong
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas 75246, USA
| | - Xiaofang Wang
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, Texas 75246, USA
| | - Minghao Zheng
- Centre for Orthopaedic Research, Medical School, The University of Western Australia, Nedlands, WA, Australia
| | - Yan Jing
- Department of Orthodontics, Texas A&M University College of Dentistry, Dallas, TX, 75246, USA.,✉ Corresponding authors: Yan Jing, E-mail: Department of Orthodontics, Texas A&M University College of Dentistry, Dallas, Texas 75246, USA. Tel./Fax: +1-214-370-7327. Jian Q. Feng, E-mail: Dental School, the University of Western Australia, Nedlands, 6009 Perth, Australia. Tel./Fax: +1-469-487-4584
| | - Jian Q. Feng
- Dental School and Oral Health Centre, The University of Western Australia, Nedlands, 6009 Australia.,✉ Corresponding authors: Yan Jing, E-mail: Department of Orthodontics, Texas A&M University College of Dentistry, Dallas, Texas 75246, USA. Tel./Fax: +1-214-370-7327. Jian Q. Feng, E-mail: Dental School, the University of Western Australia, Nedlands, 6009 Perth, Australia. Tel./Fax: +1-469-487-4584
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7
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Growth and mechanobiology of the tendon-bone enthesis. Semin Cell Dev Biol 2022; 123:64-73. [PMID: 34362655 PMCID: PMC8810906 DOI: 10.1016/j.semcdb.2021.07.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 07/17/2021] [Accepted: 07/20/2021] [Indexed: 12/15/2022]
Abstract
Tendons are cable-like connective tissues that transfer both active and passive forces generated by skeletal muscle to bone. In the mature skeleton, the tendon-bone enthesis is an interfacial zone of transitional tissue located between two mechanically dissimilar tissues: compliant, fibrous tendon to rigid, dense mineralized bone. In this review, we focus on emerging areas in enthesis development related to its structure, function, and mechanobiology, as well as highlight established and emerging signaling pathways and physiological processes that influence the formation and adaptation of this important transitional tissue.
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8
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Liu Y, Deng XH, Zhang X, Cong T, Chen D, Hall AJ, Ying L, Rodeo SA. The Role of Indian Hedgehog Signaling in Tendon Response to Subacromial Impingement: Evaluation Using a Mouse Model. Am J Sports Med 2022; 50:362-370. [PMID: 34904906 DOI: 10.1177/03635465211062244] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND The underlying cellular and molecular mechanisms involved in the development of tendinopathy due to subacromial supraspinatus tendon (SST) impingement and the response to subsequent removal of impingement remain unknown. PURPOSE To investigate the involvement of Indian hedgehog (IHH) signaling in the development of SST tendinopathy and the subsequent healing process after the relief of subacromial impingement in a novel mouse shoulder impingement model. STUDY DESIGN Controlled laboratory study. METHODS A total of 48 male wild-type C57BL/6 mice were used in this study. Supraspinatus tendinopathy was induced by inserting a microsurgical clip into the subacromial space bilaterally. Eleven mice were sacrificed at 4 weeks after surgery to establish impingement baseline; 24 mice underwent clip removal at 4 weeks after surgery and then were euthanized at 2 or 4 weeks after clip removal. Thirteen mice without surgical intervention were utilized as the control group. All SSTs were evaluated with biomechanical testing; quantitative histomorphometry after staining with hematoxylin and eosin, Alcian blue, and picrosirius red; and immunohistochemical staining (factor VIII, IHH, Patched1 [PTCH1], and glioma-associated oncogene homolog 1 [GLI1]). RESULTS The mean failure force and stiffness in the 4-week impingement group decreased significantly compared with the control group (P < .001) and gradually increased at 2 and 4 weeks after clip removal. Histological analysis demonstrated increased cellularity and disorganized collagen fibers in the SST, with higher modified Bonar scores at 4 weeks, followed by gradual improvement after clip removal. The IHH-positive area and PTCH1- and GLI1-positive cell percentages significantly increased after 4 weeks of clip impingement (20.64% vs 2.06%, P < .001; 53.9% vs 28.03%, P = .016; and 30% vs 12.19%, P = .036, respectively) and continuously increased after clip removal. CONCLUSION The authors' findings suggest that the hedgehog signaling pathway and its downstream signaling mediator and target GLI1 may play a role in the development and healing process of rotator cuff tendinopathy due to extrinsic rotator cuff impingement. CLINICAL RELEVANCE This study suggests the potential for the hedgehog pathway, together with its downstream targets, as candidates for further study as potential therapeutic targets in the treatment of supraspinatus tendinopathy.
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Affiliation(s)
- Yulei Liu
- Orthopedic Soft Tissue Research Program, Hospital for Special Surgery, New York, New York, USA.,Institute of Sports Medicine, Peking University Third Hospital, Beijing, China
| | - Xiang-Hua Deng
- Orthopedic Soft Tissue Research Program, Hospital for Special Surgery, New York, New York, USA
| | - Xueying Zhang
- Orthopedic Soft Tissue Research Program, Hospital for Special Surgery, New York, New York, USA
| | - Ting Cong
- Orthopedic Soft Tissue Research Program, Hospital for Special Surgery, New York, New York, USA
| | - Daoyun Chen
- Orthopedic Soft Tissue Research Program, Hospital for Special Surgery, New York, New York, USA
| | - Arielle Jordan Hall
- Orthopedic Soft Tissue Research Program, Hospital for Special Surgery, New York, New York, USA
| | - Liang Ying
- Orthopedic Soft Tissue Research Program, Hospital for Special Surgery, New York, New York, USA
| | - Scott A Rodeo
- Orthopedic Soft Tissue Research Program, Hospital for Special Surgery, New York, New York, USA
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9
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Hedgehog signaling underlying tendon and enthesis development and pathology. Matrix Biol 2022; 105:87-103. [PMID: 34954379 PMCID: PMC8821161 DOI: 10.1016/j.matbio.2021.12.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 12/18/2021] [Accepted: 12/19/2021] [Indexed: 02/08/2023]
Abstract
Hedgehog (Hh) signaling has been widely acknowledged to play essential roles in many developmental processes, including endochondral ossification and growth plate maintenance. Furthermore, a rising number of studies have shown that Hh signaling is necessary for tendon enthesis development. Specifically, the well-tuned regulation of Hh signaling during development drives the formation of a mineral gradient across the tendon enthesis fibrocartilage. However, aberrant Hh signaling can also lead to pathologic heterotopic ossification in tendon or osteophyte formation at the enthesis. Therefore, the therapeutic potential of Hh signaling modulation for treating tendon and enthesis diseases remains uncertain. For example, increased Hh signaling may enhance tendon-to-bone healing by promoting the formation of mineralized fibrocartilage at the healing interface, but pathologic heterotopic ossification may also be triggered in the adjacent tendon. Further work is needed to elucidate the distinct functions of Hh signaling in the tendon and enthesis to support the development of therapies that target the pathway.
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10
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Fang F, Schwartz AG, Moore ER, Sup ME, Thomopoulos S. Primary cilia as the nexus of biophysical and hedgehog signaling at the tendon enthesis. SCIENCE ADVANCES 2020; 6:6/44/eabc1799. [PMID: 33127677 PMCID: PMC7608799 DOI: 10.1126/sciadv.abc1799] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 09/17/2020] [Indexed: 05/10/2023]
Abstract
The tendon enthesis is a fibrocartilaginous tissue critical for transfer of muscle forces to bone. Enthesis pathologies are common, and surgical repair of tendon to bone is plagued by high failure rates. At the root of these failures is a gap in knowledge of how the tendon enthesis is formed and maintained. We tested the hypothesis that the primary cilium is a hub for transducing biophysical and hedgehog (Hh) signals to regulate tendon enthesis formation and adaptation to loading. Primary cilia were necessary for enthesis development, and cilia assembly was coincident with Hh signaling and enthesis mineralization. Cilia responded inversely to loading; increased loading led to decreased cilia and decreased loading led to increased cilia. Enthesis responses to loading were dependent on Hh signaling through cilia. Results imply a role for tendon enthesis primary cilia as mechanical responders and Hh signal transducers, providing a therapeutic target for tendon enthesis pathologies.
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Affiliation(s)
- Fei Fang
- Department of Orthopedic Surgery, Columbia University, New York, NY, 10032, USA
| | - Andrea G Schwartz
- Department of Orthopedic Surgery, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Emily R Moore
- School of Dental Medicine, Harvard University, Cambridge, MA, 02138, USA
| | - McKenzie E Sup
- Department of Orthopedic Surgery, Columbia University, New York, NY, 10032, USA
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | - Stavros Thomopoulos
- Department of Orthopedic Surgery, Columbia University, New York, NY, 10032, USA.
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
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11
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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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12
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Friese N, Gierschner MB, Schadzek P, Roger Y, Hoffmann A. Regeneration of Damaged Tendon-Bone Junctions (Entheses)-TAK1 as a Potential Node Factor. Int J Mol Sci 2020; 21:E5177. [PMID: 32707785 PMCID: PMC7432881 DOI: 10.3390/ijms21155177] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 07/10/2020] [Accepted: 07/20/2020] [Indexed: 12/20/2022] Open
Abstract
Musculoskeletal dysfunctions are highly prevalent due to increasing life expectancy. Consequently, novel solutions to optimize treatment of patients are required. The current major research focus is to develop innovative concepts for single tissues. However, interest is also emerging to generate applications for tissue transitions where highly divergent properties need to work together, as in bone-cartilage or bone-tendon transitions. Finding medical solutions for dysfunctions of such tissue transitions presents an added challenge, both in research and in clinics. This review aims to provide an overview of the anatomical structure of healthy adult entheses and their development during embryogenesis. Subsequently, important scientific progress in restoration of damaged entheses is presented. With respect to enthesis dysfunction, the review further focuses on inflammation. Although molecular, cellular and tissue mechanisms during inflammation are well understood, tissue regeneration in context of inflammation still presents an unmet clinical need and goes along with unresolved biological questions. Furthermore, this review gives particular attention to the potential role of a signaling mediator protein, transforming growth factor beta-activated kinase-1 (TAK1), which is at the node of regenerative and inflammatory signaling and is one example for a less regarded aspect and potential important link between tissue regeneration and inflammation.
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Affiliation(s)
- Nina Friese
- Department of Orthopedic Surgery, Graded Implants and Regenerative Strategies, OE 8893, Laboratory for Biomechanics and Biomaterials, Hannover Medical School (MHH), 30625 Hannover, Germany; (N.F.); (M.B.G.); (P.S.); (Y.R.)
- Lower Saxony Centre for Biomedical Engineering, Implant Research and Development (NIFE), 30625 Hannover, Germany
| | - Mattis Benno Gierschner
- Department of Orthopedic Surgery, Graded Implants and Regenerative Strategies, OE 8893, Laboratory for Biomechanics and Biomaterials, Hannover Medical School (MHH), 30625 Hannover, Germany; (N.F.); (M.B.G.); (P.S.); (Y.R.)
- Lower Saxony Centre for Biomedical Engineering, Implant Research and Development (NIFE), 30625 Hannover, Germany
| | - Patrik Schadzek
- Department of Orthopedic Surgery, Graded Implants and Regenerative Strategies, OE 8893, Laboratory for Biomechanics and Biomaterials, Hannover Medical School (MHH), 30625 Hannover, Germany; (N.F.); (M.B.G.); (P.S.); (Y.R.)
- Lower Saxony Centre for Biomedical Engineering, Implant Research and Development (NIFE), 30625 Hannover, Germany
| | - Yvonne Roger
- Department of Orthopedic Surgery, Graded Implants and Regenerative Strategies, OE 8893, Laboratory for Biomechanics and Biomaterials, Hannover Medical School (MHH), 30625 Hannover, Germany; (N.F.); (M.B.G.); (P.S.); (Y.R.)
- Lower Saxony Centre for Biomedical Engineering, Implant Research and Development (NIFE), 30625 Hannover, Germany
| | - Andrea Hoffmann
- Department of Orthopedic Surgery, Graded Implants and Regenerative Strategies, OE 8893, Laboratory for Biomechanics and Biomaterials, Hannover Medical School (MHH), 30625 Hannover, Germany; (N.F.); (M.B.G.); (P.S.); (Y.R.)
- Lower Saxony Centre for Biomedical Engineering, Implant Research and Development (NIFE), 30625 Hannover, Germany
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13
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Biomechanical, histologic, and molecular characteristics of graft-tunnel healing in a murine modified ACL reconstruction model. J Orthop Translat 2020; 24:103-111. [PMID: 32775202 PMCID: PMC7390781 DOI: 10.1016/j.jot.2020.05.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2019] [Revised: 05/15/2020] [Accepted: 05/20/2020] [Indexed: 02/07/2023] Open
Abstract
Purpose The purpose of our study was to introduce and validate a metal-free, reproducible and reliable mouse model of anterior cruciate ligament (ACL) reconstruction (ACLR) surgery as an effective tool for a better understanding of molecular mechanisms of graft-tunnel healing after ACLR. Methods A total of 150 C57BL/6 mice were randomly allocated into five Groups: Group 1 (mice with intact ACL), Group 2–4 (mice underwent modified ACLR surgery and sacrificed 1-, 2-, and 4-weeks after surgery), and Group 5 (mice underwent unmodified ACLR surgery and sacrificed 4 weeks after surgery). Micro-computed tomography (CT), biomechanical histological as well as immunohistochemical (IHC) analyses were performed to characterize the modified ACLR. Results Micro-CT analysis demonstrated there is a non-significant increase in BV/TV and BMD of the bone tunnel during the tendon-to-bone healing following ACLR. Biomechanical tests showed that the mean load-to-failure forces of Group 3 and 4 are equal to 31.7% and 46.0% of that in Group 1, while the stiffness was 33.1% and 57.2% of that of Group 1, respectively. And no obvious difference in biomechanical parameters was found between Group 4 and 5. Histological analysis demonstrated that formation of fibrovascular tissue in the tibial tunnel and aperture in Groups 4 and 5 and direct junction appeared between tendon graft and tunnel both in Groups 4 and 5. IHC results showed that there are gradually enhanced expression of Patched1, Smoothened and Gli2 concomitant with decreased Gli3 protein in the tendon-bone interface during the tendon-bone healing process. Conclusion We introduced a metal-free, reproducible and reliable mouse model of ACLR compared to the unmodified ACLR procedure, and characterized the expression pattern of key molecules in Ihh signaling during the graft healing process. The translational potential of this article In the present study we introduced and validated, for the first time, a metal-free, reproducible and reliable ACLR mouse model, which could be used to investigate the detailed molecular mechanisms of graft-tunnel healing after ACLR. We also explored new strategies to promote the healing of tendon-to-bone integration.
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Key Words
- ACL, Anterior cruciate ligament
- ACLR, ACL reconstruction
- Anterior cruciate ligament
- BMD, Bone mineral density
- BV/TV, Bone volume/total volume
- CI, Confidence interval
- CT, Computed tomography
- Gli1, Glioma-associated oncogene homologue 1
- Gli2, Glioma-associated oncogene homologue 2
- Gli3, Glioma-associated oncogene homologue 3
- H&E, Haematoxylin-eosin
- Hedgehog signaling
- Ihh, Indian hedgehog
- Mouse model
- NS, Non-significant
- Ptch1, Patched1
- Smo, Smoothened
- Tendon-bone healing
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14
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Liu H, Xu J, Jiang R. Mkx-Deficient Mice Exhibit Hedgehog Signaling-Dependent Ectopic Ossification in the Achilles Tendons. J Bone Miner Res 2019; 34:557-569. [PMID: 30458056 PMCID: PMC6535142 DOI: 10.1002/jbmr.3630] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 10/25/2018] [Accepted: 11/06/2018] [Indexed: 01/02/2023]
Abstract
Heterotopic ossification is the abnormal formation of mineralized bone in skin, muscle, tendon, or other soft tissues. Tendon ossification often occurs from acute tendon injury or chronic tendon degeneration, for which current treatment relies heavily on surgical removal of the ectopic bony tissues. Unfortunately, surgery creates additional trauma, which often causes recurrence of heterotopic ossification. The molecular mechanisms of heterotopic ossification are not well understood. Previous studies demonstrate that Mkx is a transcription factor crucial for postnatal tendon fibril growth. Here we report that Mkx-/- mutant mice exhibit ectopic ossification in the Achilles tendon within 1 month after birth and the tendon ossification deteriorates with age. Genetic lineage labeling revealed that the tendon ossification in Mkx-/- mice resulted from aberrant differentiation of tendon progenitor cells. Furthermore, tissue-specific inactivation of Mkx in tendon cells postnatally resulted in a similar ossification phenotype, indicating that Mkx plays a key role in tendon tissue homeostasis. Moreover, we show that Hedgehog signaling is ectopically activated at early stages of tendon ossification and that tissue-specific inactivation of Smoothened, which encodes the obligatory transducer of Hedgehog signaling, in the tendon cell lineage prevented or dramatically reduced tendon ossification in Mkx-/- mice. Together, these studies establish a new genetic mouse model of tendon ossification and provide new insight into its pathogenic mechanisms. © 2018 American Society for Bone and Mineral Research.
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Affiliation(s)
- Han Liu
- Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Jingyue Xu
- Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Rulang Jiang
- Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.,Division of Plastic Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.,Shriners Hospitals for Children-Cincinnati, Cincinnati, OH, USA
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15
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Calejo I, Costa-Almeida R, Gomes ME. Cellular Complexity at the Interface: Challenges in Enthesis Tissue Engineering. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1144:71-90. [PMID: 30632116 DOI: 10.1007/5584_2018_307] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The complex heterogeneous cellular environment found in tendon-to-bone interface makes this structure a challenge for interface tissue engineering. Orthopedic surgeons still face some problems associated with the formation of fibrotic tissue or re-tear occurring after surgical re-attachment of tendons to the bony insertion or the application of grafts. Unfortunately, an understanding of the cellular component of enthesis lags far behind of other well-known musculoskeletal interfaces, which blocks the development of new treatment options for the healing and regeneration of this multifaceted junction. In this chapter, the main characteristics of tendon and bone cell populations are introduced, followed by a brief description of the interfacial cellular niche, highlighting molecular mechanisms governing tendon-to-bone attachment and mineralization. Finally, we describe and critically assess some challenges faced concerning the use of cell-based strategies in tendon-to-bone healing and regeneration.
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Affiliation(s)
- Isabel Calejo
- 3B's Research Group, I3Bs - Research Institute on Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Guimarães, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Raquel Costa-Almeida
- 3B's Research Group, I3Bs - Research Institute on Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Guimarães, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Manuela E Gomes
- 3B's Research Group, I3Bs - Research Institute on Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Guimarães, Portugal. .,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal. .,The Discoveries Centre for Regenerative and Precision Medicine, Headquarters at University of Minho, Guimarães, Portugal.
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16
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Felsenthal N, Rubin S, Stern T, Krief S, Pal D, Pryce BA, Schweitzer R, Zelzer E. Development of migrating tendon-bone attachments involves replacement of progenitor populations. Development 2018; 145:dev.165381. [PMID: 30504126 DOI: 10.1242/dev.165381] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 11/16/2018] [Indexed: 12/27/2022]
Abstract
Tendon-bone attachment sites, called entheses, are essential for musculoskeletal function. They are formed embryonically by Sox9+ progenitors and continue to develop postnatally, utilizing Gli1 lineage cells. Despite their importance, we lack information on the transition from embryonic to mature enthesis and on the relation between Sox9+ progenitors and the Gli1 lineage. Here, by performing a series of lineage tracing experiments in mice, we identify the onset of Gli1 lineage contribution to different entheses. We show that Gli1 expression is regulated embryonically by SHH signaling, whereas postnatally it is maintained by IHH signaling. During bone elongation, some entheses migrate along the bone shaft, whereas others remain stationary. Interestingly, in stationary entheses Sox9 + cells differentiate into the Gli1 lineage, but in migrating entheses this lineage is replaced by Gli1 lineage. These Gli1+ progenitors are defined embryonically to occupy the different domains of the mature enthesis. Overall, these findings demonstrate a developmental strategy whereby one progenitor population establishes a simple embryonic tissue, whereas another population contributes to its maturation. Moreover, they suggest that different cell populations may be considered for cell-based therapy of enthesis injuries.
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Affiliation(s)
- Neta Felsenthal
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Sarah Rubin
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Tomer Stern
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Sharon Krief
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Deepanwita Pal
- Research Division, Shriners Hospital for Children, Portland, OR 97201, USA
| | - Brian A Pryce
- Research Division, Shriners Hospital for Children, Portland, OR 97201, USA
| | - Ronen Schweitzer
- Research Division, Shriners Hospital for Children, Portland, OR 97201, USA
| | - Elazar Zelzer
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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17
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Jensen PT, Lambertsen KL, Frich LH. Assembly, maturation, and degradation of the supraspinatus enthesis. J Shoulder Elbow Surg 2018; 27:739-750. [PMID: 29329904 DOI: 10.1016/j.jse.2017.10.030] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 10/22/2017] [Accepted: 10/27/2017] [Indexed: 02/01/2023]
Abstract
The development of the rotator cuff enthesis is still poorly understood. The processes in the early and late developmental steps are gradually elucidated, but it is still unclear how cell activities are coordinated during development and maturation of the structured enthesis. This review summarizes current knowledge about development and age-related degradation of the supraspinatus enthesis. Healing and repair of an injured and degenerated supraspinatus enthesis also remain a challenge, as the original graded transitional tissue of the fibrocartilaginous insertion is not re-created after the tendon is surgically reattached to bone. Instead, mechanically inferior and disorganized tissue forms at the healing site because of scar tissue formation. Consequently, the enthesis never reaches mechanical properties comparable to those of the native enthesis. So far, no novel biologic healing approach has been successful in enhancing healing of the injured enthesis. The results revealed in this review imply the need for further research to pave the way for better treatment of patients with rotator cuff disorder.
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Affiliation(s)
- Peter T Jensen
- Department of Clinical Research, University of Southern Denmark, Odense, Denmark
| | - Kate L Lambertsen
- Department of Clinical Research, University of Southern Denmark, Odense, Denmark; Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Lars H Frich
- Department of Clinical Research, University of Southern Denmark, Odense, Denmark; Department of Orthopaedics and Traumatology, Odense University Hospital, Odense, Denmark.
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18
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Lim J, Munivez E, Jiang MM, Song IW, Gannon F, Keene DR, Schweitzer R, Lee BH, Joeng KS. mTORC1 Signaling is a Critical Regulator of Postnatal Tendon Development. Sci Rep 2017; 7:17175. [PMID: 29215029 PMCID: PMC5719403 DOI: 10.1038/s41598-017-17384-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 11/24/2017] [Indexed: 12/11/2022] Open
Abstract
Tendons transmit contractile forces between musculoskeletal tissues. Whereas the biomechanical properties of tendons have been studied extensively, the molecular mechanisms regulating postnatal tendon development are not well understood. Here we examine the role of mTORC1 signaling in postnatal tendon development using mouse genetic approaches. Loss of mTORC1 signaling by removal of Raptor in tendons caused severe tendon defects postnatally, including decreased tendon thickness, indicating that mTORC1 is necessary for postnatal tendon development. By contrast, activation of mTORC1 signaling in tendons increased tendon cell numbers and proliferation. In addition, Tsc1 conditional knockout mice presented severely disorganized collagen fibers and neovascularization in the tendon midsubstance. Interestingly, collagen fibril diameter was significantly reduced in both Raptor and Tsc1 conditional knockout mice, albeit with variations in severity. We performed RNA-seq analysis using Achilles tendons to investigate the molecular changes underlying these tendon phenotypes. Raptor conditional knockout mice showed decreased extracellular matrix (ECM) structure-related gene expression, whereas Tsc1 conditional knockout mice exhibited changes in genes regulating TGF-β/BMP/FGF signaling, as well as in genes controlling ECM structure and disassembly. Collectively, our studies suggest that maintaining physiological levels of mTORC1 signaling is essential for postnatal tendon development and maturation.
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Affiliation(s)
- Joohyun Lim
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA
| | - Elda Munivez
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA
| | - Ming-Ming Jiang
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA
| | - I-Wen Song
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA
| | - Francis Gannon
- Department of Pathology, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA
| | - Douglas R Keene
- Research Center, Shriners Hospital for Children, Portland, OR, 97239, USA
| | - Ronen Schweitzer
- Research Center, Shriners Hospital for Children, Portland, OR, 97239, USA
| | - Brendan H Lee
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA.
| | - Kyu Sang Joeng
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA
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19
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Abstract
During embryogenesis, the musculoskeletal system develops while containing within itself a force generator in the form of the musculature. This generator becomes functional relatively early in development, exerting an increasing mechanical load on neighboring tissues as development proceeds. A growing body of evidence indicates that such mechanical forces can be translated into signals that combine with the genetic program of organogenesis. This unique situation presents both a major challenge and an opportunity to the other tissues of the musculoskeletal system, namely bones, joints, tendons, ligaments and the tissues connecting them. Here, we summarize the involvement of muscle-induced mechanical forces in the development of various vertebrate musculoskeletal components and their integration into one functional unit.
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Affiliation(s)
- Neta Felsenthal
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Elazar Zelzer
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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20
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Deng A, Zhang H, Hu M, Liu S, Wang Y, Gao Q, Guo C. The inhibitory roles of Ihh downregulation on chondrocyte growth and differentiation. Exp Ther Med 2017; 15:789-794. [PMID: 29434683 PMCID: PMC5772930 DOI: 10.3892/etm.2017.5458] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Accepted: 11/03/2017] [Indexed: 01/05/2023] Open
Abstract
The proliferative rate of chondrocytes affects bone elongation. Chondrocyte hypertrophy is required for endochondral bone formation as chondrocytes secrete factors required for osteoblast differentiation and maturation. Previous studies have demonstrated that the Indian hedgehog (Ihh) signaling pathway is a key regulator of skeletal development and homeostasis. The aim of the present study was to investigate the function of Ihh in chondrocyte proliferation and differentiation, as well as the underlying mechanisms. Ihh was knocked down in mouse chondrocyte cells using short hairpin RNA. Chondrocyte apoptosis and cell cycle arrest were assessed using flow cytometry and the results indicated that knockdown of Ihh significantly inhibited cell growth (P<0.05) and increased apoptosis (P<0.001) compared with negative control cells. Downregulation of Ihh also resulted in cell cycle arrest at G1 to S phase in chondrocytes. It was also observed that knockdown of Ihh decreased alkaline phosphatase activity and mineral deposition of chondrocytes. The inhibitory roles of Ihh downregulation on chondrocyte growth and differentiation may be associated with the transforming growth factor-β/mothers against decapentaplegic and osteoprotegerin/receptor activator of nuclear factor κB ligand signaling pathway. The results of the present study suggest that chondrocyte-derived Ihh is essential for maintaining bone growth plates and that manipulation of Ihh expression or its signaling components may be a novel therapeutic technique for the treatment of skeletal diseases, including achondroplasia.
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Affiliation(s)
- Ang Deng
- Department of Spine Surgery, Xiangya Hospital of Central South University, Changsha, Hunan 410008, P.R. China
| | - Hongqi Zhang
- Department of Spine Surgery, Xiangya Hospital of Central South University, Changsha, Hunan 410008, P.R. China
| | - Minyu Hu
- Department of Nutrition and Food Hygiene, School of Public Health, Central South University, Changsha, Hunan 410078, P.R. China
| | - Shaohua Liu
- Department of Spine Surgery, Xiangya Hospital of Central South University, Changsha, Hunan 410008, P.R. China
| | - Yuxiang Wang
- Department of Spine Surgery, Xiangya Hospital of Central South University, Changsha, Hunan 410008, P.R. China
| | - Qile Gao
- Department of Spine Surgery, Xiangya Hospital of Central South University, Changsha, Hunan 410008, P.R. China
| | - Chaofeng Guo
- Department of Spine Surgery, Xiangya Hospital of Central South University, Changsha, Hunan 410008, P.R. China
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21
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Zong JC, Mosca MJ, Degen RM, Lebaschi A, Carballo C, Carbone A, Cong GT, Ying L, Deng XH, Rodeo SA. Involvement of Indian hedgehog signaling in mesenchymal stem cell-augmented rotator cuff tendon repair in an athymic rat model. J Shoulder Elbow Surg 2017; 26:580-588. [PMID: 27887870 DOI: 10.1016/j.jse.2016.09.036] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Revised: 09/21/2016] [Accepted: 09/29/2016] [Indexed: 02/01/2023]
Abstract
BACKGROUND Bone marrow aspirate has been used in recent years to augment tendon-to-bone healing, including in rotator cuff repair. However, the healing mechanism in cell-based therapy has not been elucidated in detail. METHODS Sixteen athymic nude rats were randomly allocated to 2 groups: experimental (human mesenchymal stem cells in fibrin glue carrier) and control (fibrin glue only). Animals were sacrificed at 2 and 4 weeks. Immunohistochemical staining was performed to evaluate Indian hedgehog (Ihh) signaling and SOX9 signaling in the healing enthesis. Macrophages were identified using CD68 and CD163 staining, and proliferating cells were identified using proliferating cell nuclear antigen staining. RESULTS More organized and stronger staining for collagen II and a higher abundance of SOX9+ cells were observed at the enthesis in the experimental group at 2 weeks. There was significantly higher Gli1 and Patched1 expression in the experimental group at the enthesis at 2 weeks and higher numbers of Ihh+ cells in the enthesis of the experimental group vs control at both 2 weeks and 4 weeks postoperatively. There were more CD68+ cells localized to the tendon midsubstance at 2 weeks compared with 4 weeks, and there was a higher level of CD163 staining in the tendon midsubstance in the experimental group than in the control group at 4 weeks. CONCLUSION Stem cell application had a positive effect on fibrocartilage formation at the healing rotator cuff repair site. Both SOX9 and Ihh signaling appear to play an important role in the healing process.
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Affiliation(s)
- Jian-Chun Zong
- Department of Orthopaedic Surgery, The Second Affiliated Hospital, Chongqing Medical University, Chongqing, China
| | | | - Ryan M Degen
- The Hospital for Special Surgery, New York, NY, USA
| | | | | | | | | | - Liang Ying
- The Hospital for Special Surgery, New York, NY, USA
| | | | - Scott A Rodeo
- The Hospital for Special Surgery, New York, NY, USA.
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22
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Huang AH. Coordinated development of the limb musculoskeletal system: Tendon and muscle patterning and integration with the skeleton. Dev Biol 2017; 429:420-428. [PMID: 28363737 DOI: 10.1016/j.ydbio.2017.03.028] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 03/16/2017] [Accepted: 03/27/2017] [Indexed: 12/14/2022]
Abstract
Functional movement and stability of the limb depends on an organized and fully integrated musculoskeletal system composed of skeleton, muscle, and tendon. Much of our current understanding of musculoskeletal development is based on studies that focused on the development and differentiation of individual tissues. Likewise, research on patterning events have been largely limited to the primary skeletal elements and the mechanisms that regulate soft tissue patterning, the development of the connections between tissues, and their interdependent development are only beginning to be elucidated. This review will therefore highlight recent exciting discoveries in this field, with an emphasis on tendon and muscle patterning and their integrated development with the skeleton and skeletal attachments.
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Affiliation(s)
- Alice H Huang
- Icahn School of Medicine at Mount Sinai, Department of Orthopaedics, 1 Gustave Levy Place, Box 1188, New York, NY 10029, United States.
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23
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Schwartz AG, Galatz LM, Thomopoulos S. Enthesis regeneration: a role for Gli1+ progenitor cells. Development 2017; 144:1159-1164. [PMID: 28219952 DOI: 10.1242/dev.139303] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 02/13/2017] [Indexed: 12/14/2022]
Abstract
The tendon enthesis originates from a specific pool of hedgehog-active Gli1+ progenitor cells that differentiate and produce mineralized fibrocartilage. The current study investigated the regenerative capacity of this cell population by comparing the responses of early postnatal and mature entheses to injury. Lineage tracing studies demonstrated that the original Gli1+ cell population had the capacity to heal immature entheses after injury, but this capacity was lost after the cells differentiated into mature fibrochondrocytes. To further examine the involvement of Gli1+ cells and hedgehog signaling in enthesis healing, Gli1 expression was examined via lineage tracing approaches and the effect of Smo deletion was examined in the injured entheses. Immature injured entheses retained high levels of Gli1 expression, a marker of hedgehog activation, consistent with non-injured controls. In contrast, injured mature entheses had few Gli1+ cells early in the healing process, with limited recovery of the cell population later in the healing process. These results suggest that the presence of activated hedgehog signaling in enthesis cells early in the healing process may enhance healing of enthesis injuries by mimicking developmental processes.
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Affiliation(s)
- Andrea G Schwartz
- Department of Orthopedic Surgery, Washington University, St. Louis, MO 63110, USA
| | - Leesa M Galatz
- Department of Orthopedic Surgery, Icahn School of Medicine at Mount Sinai Hospital, Mount Sinai Health System, New York, NY 10029, USA
| | - Stavros Thomopoulos
- Department of Orthopedic Surgery, Columbia University, New York, NY 10032, USA .,Department of Biomedical Engineering, Columbia University, New York, NY 10032, USA
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24
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Rothrauff BB, Pauyo T, Debski RE, Rodosky MW, Tuan RS, Musahl V. The Rotator Cuff Organ: Integrating Developmental Biology, Tissue Engineering, and Surgical Considerations to Treat Chronic Massive Rotator Cuff Tears. TISSUE ENGINEERING PART B-REVIEWS 2017; 23:318-335. [PMID: 28084902 DOI: 10.1089/ten.teb.2016.0446] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The torn rotator cuff remains a persistent orthopedic challenge, with poor outcomes disproportionately associated with chronic, massive tears. Degenerative changes in the tissues that comprise the rotator cuff organ, including muscle, tendon, and bone, contribute to the poor healing capacity of chronic tears, resulting in poor function and an increased risk for repair failure. Tissue engineering strategies to augment rotator cuff repair have been developed in an effort to improve rotator cuff healing and have focused on three principal aims: (1) immediate mechanical augmentation of the surgical repair, (2) restoration of muscle quality and contractility, and (3) regeneration of native enthesis structure. Work in these areas will be reviewed in sequence, highlighting the relevant pathophysiology, developmental biology, and biomechanics, which must be considered when designing therapeutic applications. While the independent use of these strategies has shown promise, synergistic benefits may emerge from their combined application given the interdependence of the tissues that constitute the rotator cuff organ. Furthermore, controlled mobilization of augmented rotator cuff repairs during postoperative rehabilitation may provide mechanotransductive cues capable of guiding tissue regeneration and restoration of rotator cuff function. Present challenges and future possibilities will be identified, which if realized, may provide solutions to the vexing condition of chronic massive rotator cuff tears.
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Affiliation(s)
- Benjamin B Rothrauff
- 1 Department of Orthopaedic Surgery, Center for Cellular and Molecular Engineering, University of Pittsburgh , Pittsburgh, Pennsylvania.,2 McGowan Institute for Regenerative Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Thierry Pauyo
- 3 Division of Sports Medicine, Department of Orthopaedic Surgery, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Richard E Debski
- 2 McGowan Institute for Regenerative Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Mark W Rodosky
- 3 Division of Sports Medicine, Department of Orthopaedic Surgery, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Rocky S Tuan
- 1 Department of Orthopaedic Surgery, Center for Cellular and Molecular Engineering, University of Pittsburgh , Pittsburgh, Pennsylvania.,2 McGowan Institute for Regenerative Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Volker Musahl
- 2 McGowan Institute for Regenerative Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania.,3 Division of Sports Medicine, Department of Orthopaedic Surgery, University of Pittsburgh , Pittsburgh, Pennsylvania.,4 Orthopaedic Robotics Laboratory, Department of Orthopaedic Surgery, University of Pittsburgh , Pittsburgh, Pennsylvania
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25
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Paredes JJ, Andarawis-Puri N. Therapeutics for tendon regeneration: a multidisciplinary review of tendon research for improved healing. Ann N Y Acad Sci 2016; 1383:125-138. [PMID: 27768813 DOI: 10.1111/nyas.13228] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 08/12/2016] [Accepted: 08/17/2016] [Indexed: 02/06/2023]
Abstract
Tendon injuries, known as tendinopathies, are common musculoskeletal injuries that affect a wide range of the population. Canonical tendon healing is characterized by fibrosis, scar formation, and the loss of tissue mechanical and structural properties. Understanding the regenerative tendon environment is an area of increasing interest in the field of musculoskeletal research. Previous studies have focused on utilizing individual elements from the fields of biomechanics, developmental biology, cell and growth factor therapy, and tissue engineering in an attempt to develop regenerative tendon therapeutics. Still, the specific mechanism for regenerative healing remains unknown. In this review, we highlight some of the current approaches of tendon therapeutics and elucidate the differences along the tendon midsubstance and enthesis, exhibiting the necessity of location-specific tendon therapeutics. Furthermore, we emphasize the necessity of further interdisciplinary research in order to reach the desired goal of fully understanding the mechanisms underlying regenerative healing.
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Affiliation(s)
| | - Nelly Andarawis-Puri
- Meinig School of Biomedical Engineering.,Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York
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26
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Dyment NA, Jiang X, Chen L, Hong SH, Adams DJ, Ackert-Bicknell C, Shin DG, Rowe DW. High-Throughput, Multi-Image Cryohistology of Mineralized Tissues. J Vis Exp 2016. [PMID: 27684089 DOI: 10.3791/54468] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
There is an increasing need for efficient phenotyping and histopathology of a variety of tissues. This phenotyping need is evident with the ambitious projects to disrupt every gene in the mouse genome. The research community needs rapid and inexpensive means to phenotype tissues via histology. Histological analyses of skeletal tissues are often time consuming and semi-quantitative at best, regularly requiring subjective interpretation of slides from trained individuals. Here, we present a cryohistological paradigm for efficient and inexpensive phenotyping of mineralized tissues. First, we present a novel method of tape-stabilized cryosectioning that preserves the morphology of mineralized tissues. These sections are then adhered rigidly to glass slides and imaged repeatedly over several rounds of staining. The resultant images are then aligned either manually or via computer software to yield composite stacks of several layered images. The protocol allows for co-localization of numerous molecular signals to specific cells within a given section. In addition, these fluorescent signals can be quantified objectively via computer software. This protocol overcomes many of the shortcomings associated with histology of mineralized tissues and can serve as a platform for high-throughput, high-content phenotyping of musculoskeletal tissues moving forward.
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Affiliation(s)
- Nathaniel A Dyment
- Department of Reconstructive Sciences, University of Connecticut Health Center;
| | - Xi Jiang
- Department of Reconstructive Sciences, University of Connecticut Health Center
| | - Li Chen
- Department of Reconstructive Sciences, University of Connecticut Health Center
| | - Seung-Hyun Hong
- Department of Computer Science and Engineering, University of Connecticut
| | - Douglas J Adams
- Department of Orthopaedic Surgery, University of Connecticut Health Center
| | | | - Dong-Guk Shin
- Department of Computer Science and Engineering, University of Connecticut
| | - David W Rowe
- Department of Reconstructive Sciences, University of Connecticut Health Center;
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27
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The role of bone sialoprotein in the tendon-bone insertion. Matrix Biol 2016; 52-54:325-338. [PMID: 26826499 DOI: 10.1016/j.matbio.2016.01.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 01/20/2016] [Accepted: 01/23/2016] [Indexed: 01/08/2023]
Abstract
Tendons/ligaments insert into bone via a transitional structure, the enthesis, which is susceptible to injury and difficult to repair. Fibrocartilaginous entheses contain fibrocartilage in their transitional zone, part of which is mineralized. Mineral-associated proteins within this zone have not been adequately characterized. Members of the Small Integrin Binding Ligand N-linked Glycoprotein (SIBLING) family are acidic phosphoproteins expressed in mineralized tissues. Here we show that two SIBLING proteins, bone sialoprotein (BSP) and osteopontin (OPN), are present in the mouse enthesis. Histological analyses indicate that the calcified zone of the quadriceps tendon enthesis is longer in Bsp(-/-) mice, however no difference is apparent in the supraspinatus tendon enthesis. In an analysis of mineral content within the calcified zone, micro-CT and Raman spectroscopy reveal that the mineral content in the calcified fibrocartilage of the quadriceps tendon enthesis are similar between wild type and Bsp(-/-) mice. Mechanical testing of the patellar tendon shows that while the tendons fail under similar loads, the Bsp(-/-) patellar tendon is 7.5% larger in cross sectional area than wild type tendons, resulting in a 16.5% reduction in failure stress. However, Picrosirius Red staining shows no difference in collagen organization. Data collected here indicate that BSP is present in the calcified fibrocartilage of murine entheses and suggest that BSP plays a regulatory role in this structure, influencing the growth of the calcified fibrocartilage in addition to the weakening of the tendon mechanical properties. Based on the phenotype of the Bsp(-/-) mouse enthesis, and the known in vitro functional properties of the protein, BSP may be a useful therapeutic molecule in the reattachment of tendons and ligaments to bone.
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28
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Cell Signaling in Tenocytes: Response to Load and Ligands in Health and Disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 920:79-95. [DOI: 10.1007/978-3-319-33943-6_7] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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29
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Killian ML, Thomopoulos S. Scleraxis is required for the development of a functional tendon enthesis. FASEB J 2015; 30:301-11. [PMID: 26443819 DOI: 10.1096/fj.14-258236] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 09/08/2015] [Indexed: 11/11/2022]
Abstract
The attachment of dissimilar materials is a major engineering challenge, yet this challenge is seemingly overcome in biology. This study aimed to determine how the transcription factor Scleraxis (Scx) influences the development and maturation of the tendon-to-bone attachment (enthesis). Mice with conditional knockout (cKO) for Scx (Scx(flx/-), Prx1Cre(+)) and wild-type [(WT) Scx(flx/+) or Scx(flx/flx)] littermates were killed at postnatal days 7-56 (P7-P56). Enthesis morphometry, histology, and collagen alignment were investigated throughout postnatal growth. Enthesis tensile mechanical properties were also assessed. Laser microdissection of distinct musculoskeletal tissues was performed at P7 for WT, cKO, and muscle-unloaded (botulinum toxin A treated) attachments for quantitative PCR. cKO mice were smaller, with altered bone shape and impaired enthesis morphology, morphometry, and organization. Structural alterations led to altered mechanical properties; cKO entheses demonstrated reduced strength and stiffness. In P7 attachments, cKO mice had reduced expression of transforming growth factor (TGF) superfamily genes in fibrocartilage compared with WT mice. In conclusion, deletion of Scx led to impairments in enthesis structure, which translated into impaired functional (i.e., mechanical) outcomes. These changes may be driven by transient signaling cues from mechanical loading and growth factors.
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Affiliation(s)
- Megan L Killian
- Department of Orthopedic Surgery, Washington University, St. Louis, Missouri, USA
| | - Stavros Thomopoulos
- Department of Orthopedic Surgery, Washington University, St. Louis, Missouri, USA
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30
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Dyment NA, Breidenbach AP, Schwartz AG, Russell RP, Aschbacher-Smith L, Liu H, Hagiwara Y, Jiang R, Thomopoulos S, Butler DL, Rowe DW. Gdf5 progenitors give rise to fibrocartilage cells that mineralize via hedgehog signaling to form the zonal enthesis. Dev Biol 2015; 405:96-107. [PMID: 26141957 DOI: 10.1016/j.ydbio.2015.06.020] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2015] [Revised: 06/03/2015] [Accepted: 06/24/2015] [Indexed: 02/01/2023]
Abstract
The sequence of events that leads to the formation of a functionally graded enthesis is not clearly defined. The current study demonstrates that clonal expansion of Gdf5 progenitors contributes to linear growth of the enthesis. Prior to mineralization, Col1+ cells in the enthesis appose Col2+ cells of the underlying primary cartilage. At the onset of enthesis mineralization, cells at the base of the enthesis express alkaline phosphatase, Indian hedgehog, and ColX as they mineralize. The mineralization front then extends towards the tendon midsubstance as cells above the front become encapsulated in mineralized fibrocartilage over time. The hedgehog (Hh) pathway regulates this process, as Hh-responsive Gli1+ cells within the developing enthesis mature from unmineralized to mineralized fibrochondrocytes in response to activated signaling. Hh signaling is required for mineralization, as tissue-specific deletion of its obligate transducer Smoothened in the developing tendon and enthesis cells leads to significant reductions in the apposition of mineralized fibrocartilage. Together, these findings provide a spatiotemporal map of events - from expansion of the embryonic progenitor pool to synthesis of the collagen template and finally mineralization of this template - that leads to the formation of the mature zonal enthesis. These results can inform future tendon-to-bone repair strategies to create a mechanically functional enthesis in which tendon collagen fibers are anchored to bone through mineralized fibrocartilage.
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Affiliation(s)
- Nathaniel A Dyment
- Center for Regenerative Medicine and Skeletal Development, School of Dental Medicine, University of Connecticut Health Center, United States.
| | - Andrew P Breidenbach
- Biomedical Engineering Program, College of Engineering and Applied Science, University of Cincinnati, United States
| | - Andrea G Schwartz
- Department of Orthopaedic Surgery, Washington University in St. Louis, United States
| | - Ryan P Russell
- Center for Regenerative Medicine and Skeletal Development, School of Dental Medicine, University of Connecticut Health Center, United States
| | | | - Han Liu
- Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, United States
| | - Yusuke Hagiwara
- Department of Orthopaedic Surgery, Nippon Medical School Hospital, Tokyo, Japan
| | - Rulang Jiang
- Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, United States
| | - Stavros Thomopoulos
- Department of Orthopaedic Surgery, Washington University in St. Louis, United States
| | - David L Butler
- Biomedical Engineering Program, College of Engineering and Applied Science, University of Cincinnati, United States
| | - David W Rowe
- Center for Regenerative Medicine and Skeletal Development, School of Dental Medicine, University of Connecticut Health Center, United States
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