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Turkel I, Tahtalioglu S, Celik E, Yazgan B, Kubat GB, Ozerklig B, Kosar SN. Time-course and muscle-specific gene expression of matrix metalloproteinases and inflammatory cytokines in response to acute treadmill exercise in rats. Mol Biol Rep 2024; 51:667. [PMID: 38780696 DOI: 10.1007/s11033-024-09637-9] [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] [Received: 02/06/2024] [Accepted: 05/13/2024] [Indexed: 05/25/2024]
Abstract
BACKGROUND The extracellular matrix (ECM) of skeletal muscle plays a pivotal role in tissue repair and growth, and its remodeling tightly regulated by matrix metalloproteinases (MMPs), tissue inhibitors of metalloproteinases (TIMPs), and inflammatory cytokines. This study aimed to investigate changes in the mRNA expression of MMPs (Mmp-2 and Mmp-14), TIMPs (Timp-1 and Timp-2), and inflammatory cytokines (Il-1β, Tnf-α, and Tgfβ1) in the soleus (SOL) and extensor digitorum longus (EDL) muscles of rats following acute treadmill exercise. Additionally, muscle morphology was examined using hematoxylin and eosin (H&E) staining. METHODS AND RESULTS Male rats were subjected to acute treadmill exercise at 25 m/min for 60 min with a %0 slope. The mRNA expression of ECM components and muscle morphology in the SOL and EDL were assessed in both sedentary and exercise groups at various time points (immediately (0) and 1, 3, 6, 12, and 24 h post-exercise). Our results revealed a muscle-specific response, with early upregulation of the mRNA expression of Mmp-2, Mmp-14, Timp-1, Timp-2, Il-1β, and Tnf-α observed in the SOL compared to the EDL. A decrease in Tgfβ1 mRNA expression was evident in the SOL at all post-exercise time points. Conversely, Tgfβ1 mRNA expression increased at 0 and 3 h post-exercise in the EDL. Histological analysis also revealed earlier cell infiltration in the SOL than in the EDL following acute exercise. CONCLUSIONS Our results highlight how acute exercise modulates ECM components and muscle structure differently in the SOL and EDL muscles, leading to distinct muscle-specific responses.
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Affiliation(s)
- Ibrahim Turkel
- Department of Exercise and Sport Sciences, Faculty of Sport Sciences, Hacettepe University, Ankara, Turkey.
| | - Sema Tahtalioglu
- Department of Biotechnology, Institute of Sciences, Amasya University, Amasya, Turkey
| | - Ertugrul Celik
- Department of Pathology, Gulhane Training and Research Hospital, University of Health Sciences, Ankara, Turkey
| | - Burak Yazgan
- Department of Medical Services and Techniques, Sabuncuoğlu Serefeddin Health Services Vocational School, Amasya University, Amasya, Turkey
| | - Gokhan Burcin Kubat
- Department of Mitochondria and Cellular Research, Gulhane Health Sciences Institute, University of Health Sciences, Ankara, Turkey
| | - Berkay Ozerklig
- Department of Exercise and Sport Sciences, Faculty of Sport Sciences, Hacettepe University, Ankara, Turkey
| | - Sukran Nazan Kosar
- Division of Exercise Nutrition and Metabolism, Faculty of Sport Sciences, Hacettepe University, Ankara, Turkey
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2
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Tong S, Sun Y, Kuang B, Wang M, Chen Z, Zhang W, Chen J. A Comprehensive Review of Muscle-Tendon Junction: Structure, Function, Injury and Repair. Biomedicines 2024; 12:423. [PMID: 38398025 PMCID: PMC10886980 DOI: 10.3390/biomedicines12020423] [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: 12/13/2023] [Revised: 01/31/2024] [Accepted: 02/08/2024] [Indexed: 02/25/2024] Open
Abstract
The muscle-tendon junction (MTJ) is a highly specific tissue interface where the muscle's fascia intersects with the extracellular matrix of the tendon. The MTJ functions as the particular structure facilitating the transmission of force from contractive muscle fibers to the skeletal system, enabling movement. Considering that the MTJ is continuously exposed to constant mechanical forces during physical activity, it is susceptible to injuries. Ruptures at the MTJ often accompany damage to both tendon and muscle tissues. In this review, we attempt to provide a precise definition of the MTJ, describe its subtle structure in detail, and introduce therapeutic approaches related to MTJ tissue engineering. We hope that our detailed illustration of the MTJ and summary of the representative research achievements will help researchers gain a deeper understanding of the MTJ and inspire fresh insights and breakthroughs for future research.
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Affiliation(s)
- Siqi Tong
- School of Medicine, Southeast University, Nanjing 210009, China
- Center for Stem Cell and Regenerative Medicine, Southeast University, Nanjing 210009, China
| | - Yuzhi Sun
- Center for Stem Cell and Regenerative Medicine, Southeast University, Nanjing 210009, China
- Department of Orthopaedic Surgery, Institute of Digital Medicine, Nanjing First Hospital, Nanjing Medical University, Nanjing 210006, China
| | - Baian Kuang
- School of Medicine, Southeast University, Nanjing 210009, China
- Center for Stem Cell and Regenerative Medicine, Southeast University, Nanjing 210009, China
| | - Mingyue Wang
- School of Medicine, Southeast University, Nanjing 210009, China
- Center for Stem Cell and Regenerative Medicine, Southeast University, Nanjing 210009, China
| | - Zhixuan Chen
- School of Medicine, Southeast University, Nanjing 210009, China
- Center for Stem Cell and Regenerative Medicine, Southeast University, Nanjing 210009, China
| | - Wei Zhang
- School of Medicine, Southeast University, Nanjing 210009, China
- Center for Stem Cell and Regenerative Medicine, Southeast University, Nanjing 210009, China
- Jiangsu Key Laboratory for Biomaterials and Devices, Southeast University, Nanjing 210096, China
- China Orthopedic Regenerative Medicine Group (CORMed), Hangzhou 310058, China
| | - Jialin Chen
- School of Medicine, Southeast University, Nanjing 210009, China
- Center for Stem Cell and Regenerative Medicine, Southeast University, Nanjing 210009, China
- Jiangsu Key Laboratory for Biomaterials and Devices, Southeast University, Nanjing 210096, China
- China Orthopedic Regenerative Medicine Group (CORMed), Hangzhou 310058, China
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3
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Yamamoto Y, Yamamoto M, Hirouchi H, Taniguchi S, Watanabe G, Matsunaga S, Abe S. Regeneration process of myotendinous junction injury induced by collagenase injection between Achilles tendon and soleus muscle in mice. Anat Sci Int 2024; 99:138-145. [PMID: 37987921 DOI: 10.1007/s12565-023-00748-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 10/25/2023] [Indexed: 11/22/2023]
Abstract
Recently, it has become clear that peri-muscular tissues play a significant role in the deterioration of muscle function. Understanding the function and regeneration of muscle, as well as its surrounding tissues, is crucial to determining the causes of muscular illnesses. However, the regeneration process of the myotendinous junction (MTJ), the most closely related peri-muscular tissue, is still unknown. Therefore, we generated a mouse model of MTJ injury by collagenase injection and searched for the process of regeneration of the MTJ and its adjacent regions. The MTJ region was damaged by collagenase injection, which greatly increased the tendon cross sectional area. Collagenase injections increased the proportion of myofibers with a central nucleus, which is a characteristic of regenerating muscle. The collagenase injection group had myofibers with central nuclei and expressing MTJ markers. Additionally, we measured the length of MTJs using serial cross sections of the soleus muscle and discovered that MTJs at 2 weeks after collagenase injection were shorter compared to the control group, with a propensity to progressively recover their length over time. The results showed that MTJs undergo morphological regeneration even when severely damaged, and that this regeneration occurs in conjunction with muscle regeneration. We anticipate that these findings will be valuable in upcoming research on motor unit regeneration.
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Affiliation(s)
| | | | | | | | - Genji Watanabe
- Department of Anatomy, Tokyo Dental College, Tokyo, Japan
| | | | - Shinichi Abe
- Department of Anatomy, Tokyo Dental College, Tokyo, Japan
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4
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Kundu A, Bhadoria P. A Case Report on Myotendinous Junction. Cureus 2023; 15:e42233. [PMID: 37605688 PMCID: PMC10440011 DOI: 10.7759/cureus.42233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/21/2023] [Indexed: 08/23/2023] Open
Abstract
Myotendinous junction is the transition zone between the muscle and its tendon. Hence, it is subject to immense stress within the muscle. In this study, it is found that muscles having a greater tensile have a more arranged myotendinous junction compared to muscles with lesser tensile strength. Cadaveric specimens - plantaris, gastrocnemius, and soleus have been histologically studied to study the same.
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Affiliation(s)
- Aditya Kundu
- Anatomy, All India Institute of Medical Sciences, Rishikesh, IND
| | - Pooja Bhadoria
- Anatomy, All India Institute of Medical Sciences, Rishikesh, IND
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5
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Lipp SN, Jacobson KR, Colling HA, Tuttle TG, Miles DT, McCreery KP, Calve S. Mechanical loading is required for initiation of extracellular matrix deposition at the developing murine myotendinous junction. Matrix Biol 2023; 116:28-48. [PMID: 36709857 PMCID: PMC10218368 DOI: 10.1016/j.matbio.2023.01.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Revised: 01/17/2023] [Accepted: 01/24/2023] [Indexed: 01/27/2023]
Abstract
The myotendinous junction (MTJ) contributes to the generation of motion by connecting muscle to tendon. At the adult MTJ, a specialized extracellular matrix (ECM) is thought to contribute to the mechanical integrity of the muscle-tendon interface, but the factors that influence MTJ formation during mammalian development are unclear. Here, we combined 3D imaging and proteomics with murine models in which muscle contractility and patterning are disrupted to resolve morphological and compositional changes in the ECM during MTJ development. We found that MTJ-specific ECM deposition can be initiated via static loading due to growth; however, it required cyclic loading to develop a mature morphology. Furthermore, the MTJ can mature without the tendon terminating into cartilage. Based on these results, we describe a model wherein MTJ development depends on mechanical loading but not insertion into an enthesis.
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Affiliation(s)
- Sarah N Lipp
- Weldon School of Biomedical Engineering, Purdue University, 206 South Martin Jischke Drive, West Lafayette, IN 47907, United States; The Indiana University Medical Scientist/Engineer Training Program, Indianapolis, IN 46202, United States
| | - Kathryn R Jacobson
- Purdue University Interdisciplinary Life Science Program, 155 S. Grant Street, West Lafayette, IN 47907, United States
| | - Haley A Colling
- Department of Integrative Physiology, University of Colorado Boulder, 354 UCB, Boulder CO, 80309, United States
| | - Tyler G Tuttle
- Paul M. Rady Department of Mechanical Engineering, University of Colorado Boulder, 1111 Engineering Dr, Boulder, CO 80309, United States
| | - Dalton T Miles
- Chemical and Biological Engineering, University of Colorado Boulder, 596 UCB, CO 80309, United States
| | - Kaitlin P McCreery
- Paul M. Rady Department of Mechanical Engineering, University of Colorado Boulder, 1111 Engineering Dr, Boulder, CO 80309, United States
| | - Sarah Calve
- Weldon School of Biomedical Engineering, Purdue University, 206 South Martin Jischke Drive, West Lafayette, IN 47907, United States; Purdue University Interdisciplinary Life Science Program, 155 S. Grant Street, West Lafayette, IN 47907, United States; Paul M. Rady Department of Mechanical Engineering, University of Colorado Boulder, 1111 Engineering Dr, Boulder, CO 80309, United States.
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6
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Jakobsen JR, Mackey AL, Koch M, Imhof T, Hannibal J, Kjaer M, Krogsgaard MR. Larger interface area at the human myotendinous junction in type 1 compared with type 2 muscle fibers. Scand J Med Sci Sports 2023; 33:136-145. [PMID: 36226768 PMCID: PMC10091713 DOI: 10.1111/sms.14246] [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: 01/15/2022] [Revised: 08/13/2022] [Accepted: 10/01/2022] [Indexed: 01/11/2023]
Abstract
The myotendinous junction (MTJ) is structurally specialized to transmit force. The highly folded muscle membrane at the MTJ increases the contact area between muscle and tendon and potentially the load tolerance of the MTJ. Muscles with a high content of type II fibers are more often subject to strain injury compared with muscles with type I fibers. It is hypothesized that this is explained by a smaller interface area of MTJ in type II compared with type I muscle fibers. The aim was to investigate by confocal microscopy whether there is difference in the surface area at the MTJ between type I and II muscle fibers. Individual muscle fibers with an intact MTJ were isolated by microscopic dissection in samples from human semitendinosus, and they were labeled with antibodies against collagen XXII (indicating MTJ) and type I myosin (MHCI). Using a spinning disc confocal microscope, the MTJ from each fiber was scanned and subsequently reconstructed to a 3D-model. The interface area between muscle and tendon was calculated in type I and II fibers from these reconstructions. The MTJ was analyzed in 314 muscle fibers. Type I muscle fibers had a 22% larger MTJ interface area compared with type II fibers (p < 0.05), also when the area was normalized to fiber diameter. By the new method, it was possible to analyze the structure of the MTJ from a large number of human muscle fibers. The finding that the interface area between muscle and tendon is higher in type I compared with type II fibers suggests that type II fibers are less resistant to strain and therefore more susceptible to injury.
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Affiliation(s)
- Jens Rithamer Jakobsen
- Section for Sports Traumatology M51, Department of Orthopaedic Surgery, Copenhagen University Hospital, Bispebjerg and Frederiksberg, Denmark
| | - Abigail Louise Mackey
- Department of Orthopaedic Surgery M, Institute of Sports Medicine, Copenhagen University Hospital, Bispebjerg and Frederiksberg, Denmark.,Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Manuel Koch
- Institute for Dental Research and Oral Musculoskeletal Biology, and Center for Biochemistry, Medical Faculty, University of Cologne, Cologne, Germany.,Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
| | - Thomas Imhof
- Institute for Dental Research and Oral Musculoskeletal Biology, and Center for Biochemistry, Medical Faculty, University of Cologne, Cologne, Germany
| | - Jens Hannibal
- Department of Clinical Biochemistry, Copenhagen University Hospital, Bispebjerg and Frederiksberg, Copenhagen, Denmark
| | - Michael Kjaer
- Department of Orthopaedic Surgery M, Institute of Sports Medicine, Copenhagen University Hospital, Bispebjerg and Frederiksberg, Denmark
| | - Michael Rindom Krogsgaard
- Section for Sports Traumatology M51, Department of Orthopaedic Surgery, Copenhagen University Hospital, Bispebjerg and Frederiksberg, Denmark
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7
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Musculoskeletal research in human space flight - unmet needs for the success of crewed deep space exploration. NPJ Microgravity 2023; 9:9. [PMID: 36707515 PMCID: PMC9883469 DOI: 10.1038/s41526-023-00258-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 01/20/2023] [Indexed: 01/29/2023] Open
Abstract
Based on the European Space Agency (ESA) Science in Space Environment (SciSpacE) community White Paper "Human Physiology - Musculoskeletal system", this perspective highlights unmet needs and suggests new avenues for future studies in musculoskeletal research to enable crewed exploration missions. The musculoskeletal system is essential for sustaining physical function and energy metabolism, and the maintenance of health during exploration missions, and consequently mission success, will be tightly linked to musculoskeletal function. Data collection from current space missions from pre-, during-, and post-flight periods would provide important information to understand and ultimately offset musculoskeletal alterations during long-term spaceflight. In addition, understanding the kinetics of the different components of the musculoskeletal system in parallel with a detailed description of the molecular mechanisms driving these alterations appears to be the best approach to address potential musculoskeletal problems that future exploratory-mission crew will face. These research efforts should be accompanied by technical advances in molecular and phenotypic monitoring tools to provide in-flight real-time feedback.
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8
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Nestin and osteocrin mRNA increases in human semitendinosus myotendinous junction 7 days after a single bout of eccentric exercise. Histochem Cell Biol 2022; 158:49-64. [DOI: 10.1007/s00418-022-02101-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/20/2022] [Indexed: 11/26/2022]
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9
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Zhang X, Wang D, Mak KLK, Tuan RS, Ker DFE. Engineering Musculoskeletal Grafts for Multi-Tissue Unit Repair: Lessons From Developmental Biology and Wound Healing. Front Physiol 2021; 12:691954. [PMID: 34504435 PMCID: PMC8421786 DOI: 10.3389/fphys.2021.691954] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 07/22/2021] [Indexed: 12/13/2022] Open
Abstract
In the musculoskeletal system, bone, tendon, and skeletal muscle integrate and act coordinately as a single multi-tissue unit to facilitate body movement. The development, integration, and maturation of these essential components and their response to injury are vital for conferring efficient locomotion. The highly integrated nature of these components is evident under disease conditions, where rotator cuff tears at the bone-tendon interface have been reported to be associated with distal pathological alterations such as skeletal muscle degeneration and bone loss. To successfully treat musculoskeletal injuries and diseases, it is important to gain deep understanding of the development, integration and maturation of these musculoskeletal tissues along with their interfaces as well as the impact of inflammation on musculoskeletal healing and graft integration. This review highlights the current knowledge of developmental biology and wound healing in the bone-tendon-muscle multi-tissue unit and perspectives of what can be learnt from these biological and pathological processes within the context of musculoskeletal tissue engineering and regenerative medicine. Integrating these knowledge and perspectives can serve as guiding principles to inform the development and engineering of musculoskeletal grafts and other tissue engineering strategies to address challenging musculoskeletal injuries and diseases.
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Affiliation(s)
- Xu Zhang
- Institute for Tissue Engineering and Regenerative Medicine, The Chinese University of Hong Kong, Shatin, China
- Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, China
| | - Dan Wang
- Institute for Tissue Engineering and Regenerative Medicine, The Chinese University of Hong Kong, Shatin, China
- Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, China
- Department of Orthopaedics and Traumatology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, China
- Key Laboratory for Regenerative Medicine, Ministry of Education, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, China
| | - King-Lun Kingston Mak
- Bioland Laboratory (Guangzhou Regenerative Medicine and Health-Guangdong Laboratory), Guangzhou, China
| | - Rocky S. Tuan
- Institute for Tissue Engineering and Regenerative Medicine, The Chinese University of Hong Kong, Shatin, China
- Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, China
| | - Dai Fei Elmer Ker
- Institute for Tissue Engineering and Regenerative Medicine, The Chinese University of Hong Kong, Shatin, China
- Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, China
- Department of Orthopaedics and Traumatology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, China
- Key Laboratory for Regenerative Medicine, Ministry of Education, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, China
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10
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Martinez GZ, Grillo BAC, Rocha LC, Jacob CDS, Pimentel Neto J, Tomiate AN, Barbosa GK, Watanabe IS, Ciena AP. Morphological Changes in the Myotendinous Junction of mdx Mice. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2021; 27:1-5. [PMID: 34376263 DOI: 10.1017/s1431927621012496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The myotendinous junction (MTJ) is the interface between muscle and tendon, and it is the main area of force transmission of the locomotor apparatus. Dystrophic processes promote pathological injury which affects the skeletal muscle and can influence the morphology of the MTJ. This study aimed to investigate the adaptations in MTJ morphology of mdx mice in the tibialis anterior muscle. Male mice (n = 24) were divided into Control—C57bl/10 and mdx—C57bl/10mdx (Duchenne muscular dystrophy experimental model). In the mdx group, centralized nuclei with a large area and greater deposition of type III collagen (fibrosis) were observed. Also, shorter sarcomeres and sarcoplasmatic projections of MTJ were observed. We concluded that the adaptations in mdx mice demonstrated extensive impairment in the MTJ region with reduced ultrastructures.
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Affiliation(s)
- Giovana Zerbo Martinez
- Laboratory of Morphology and Physical Activity (LAMAF), São Paulo State University (UNESP), Institute of Biosciences (IB), Avenue 24A, n. 1515, Rio Claro, SP 13506-900, Brazil
| | - Bruna Aléxia Cristofoletti Grillo
- Laboratory of Morphology and Physical Activity (LAMAF), São Paulo State University (UNESP), Institute of Biosciences (IB), Avenue 24A, n. 1515, Rio Claro, SP 13506-900, Brazil
| | - Lara Caetano Rocha
- Laboratory of Morphology and Physical Activity (LAMAF), São Paulo State University (UNESP), Institute of Biosciences (IB), Avenue 24A, n. 1515, Rio Claro, SP 13506-900, Brazil
| | - Carolina Dos Santos Jacob
- Laboratory of Morphology and Physical Activity (LAMAF), São Paulo State University (UNESP), Institute of Biosciences (IB), Avenue 24A, n. 1515, Rio Claro, SP 13506-900, Brazil
| | - Jurandyr Pimentel Neto
- Laboratory of Morphology and Physical Activity (LAMAF), São Paulo State University (UNESP), Institute of Biosciences (IB), Avenue 24A, n. 1515, Rio Claro, SP 13506-900, Brazil
| | - André Neri Tomiate
- Laboratory of Morphology and Physical Activity (LAMAF), São Paulo State University (UNESP), Institute of Biosciences (IB), Avenue 24A, n. 1515, Rio Claro, SP 13506-900, Brazil
| | - Gabriela Klein Barbosa
- Laboratory of Morphology and Physical Activity (LAMAF), São Paulo State University (UNESP), Institute of Biosciences (IB), Avenue 24A, n. 1515, Rio Claro, SP 13506-900, Brazil
| | - Ii-Sei Watanabe
- Department of Anatomy, Institute of Biomedical Sciences III, University of São Paulo (USP), São Paulo, SP, Brazil
| | - Adriano Polican Ciena
- Laboratory of Morphology and Physical Activity (LAMAF), São Paulo State University (UNESP), Institute of Biosciences (IB), Avenue 24A, n. 1515, Rio Claro, SP 13506-900, Brazil
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Grillo BAC, Rocha LC, Martinez GZ, Pimentel Neto J, Jacob CDS, Watanabe IS, Ciena AP. Myotendinous Junction Components of Different Skeletal Muscles Present Morphological Changes in Obese Rats. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2021; 27:1-6. [PMID: 33879277 DOI: 10.1017/s1431927621000313] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Obesity is characterized by excess adipose tissue and chronic inflammation and promotes extensive changes that can compromise skeletal muscles’ structural and functional integrity. Obesity can seriously impact the force transmission region between the muscle and the tendon, the myotendinous junction (MTJ). The present study aimed to investigate the plasticity of muscle fibers and MTJ regions in high-fat diet-induced obesity in rat tibialis anterior (TA) and soleus (SO) muscles. Wistar rats were divided into control and obese groups (induced by a high-fat diet). The samples of TA and SO muscles were prepared for histochemical and ultrastructural analysis (sarcomeres and MTJ projection). In the muscle fiber, similar adaptations were observed between the muscles of the smaller fiber (types I and IIa) in the obesity results. The MTJ region demonstrated different adaptations between the analyzed muscles. The TA–MTJ region has shorter ultrastructures, while in the SO–MTJ region, the ultrastructures were larger. We conclude that obesity induced by a high-fat diet promotes similar adaptation in the muscle fibers; however, in the MTJ region, the sarcoplasmatic projections and adjacent sarcomere demonstrate different adaptations according to distinct muscle phenotypes.
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Affiliation(s)
- Bruna Aléxia Cristofoletti Grillo
- Laboratory of Morphology and Physical Activity (LAMAF), Institute of Biosciences (IB), São Paulo State University (UNESP), Rio Claro, SP13506-900, Brazil
| | - Lara C Rocha
- Laboratory of Morphology and Physical Activity (LAMAF), Institute of Biosciences (IB), São Paulo State University (UNESP), Rio Claro, SP13506-900, Brazil
| | - Giovana Z Martinez
- Laboratory of Morphology and Physical Activity (LAMAF), Institute of Biosciences (IB), São Paulo State University (UNESP), Rio Claro, SP13506-900, Brazil
| | - Jurandyr Pimentel Neto
- Laboratory of Morphology and Physical Activity (LAMAF), Institute of Biosciences (IB), São Paulo State University (UNESP), Rio Claro, SP13506-900, Brazil
| | - Carolina Dos Santos Jacob
- Laboratory of Morphology and Physical Activity (LAMAF), Institute of Biosciences (IB), São Paulo State University (UNESP), Rio Claro, SP13506-900, Brazil
| | - Ii-Sei Watanabe
- Department of Anatomy, Institute of Biomedical Sciences -ICB III, University of São Paulo (USP), São Paulo, SP05508-900, Brazil
| | - Adriano P Ciena
- Laboratory of Morphology and Physical Activity (LAMAF), Institute of Biosciences (IB), São Paulo State University (UNESP), Rio Claro, SP13506-900, Brazil
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12
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Jakobsen JR, Krogsgaard MR. The Myotendinous Junction-A Vulnerable Companion in Sports. A Narrative Review. Front Physiol 2021; 12:635561. [PMID: 33841171 PMCID: PMC8032995 DOI: 10.3389/fphys.2021.635561] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 02/15/2021] [Indexed: 01/17/2023] Open
Abstract
The incidence of strain injuries continues to be high in many popular sports, especially hamstring strain injuries in football, despite a documented important effect of eccentric exercise to prevent strains. Studies investigating the anatomical properties of these injuries in humans are sparse. The majority of strains are seen at the interface between muscle fibers and tendon: the myotendinous junction (MTJ). It has a unique morphology with a highly folded muscle membrane filled with invaginations of collagen fibrils from the tendon, establishing an increased area of force transmission between muscle and tendon. There is a very high rate of remodeling of the muscle cells approaching the MTJ, but little is known about how the tissue adapts to exercise and which structural changes heavy eccentric exercise may introduce. This review summarizes the current knowledge about the anatomy, composition and adaptability of the MTJ, and discusses reasons why strain injuries can be prevented by eccentric exercise.
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Affiliation(s)
- Jens Rithamer Jakobsen
- Section of Sports Traumatology, M51, A Part of IOC Research Center, Bispebjerg and Frederiksberg Hospital, Copenhagen University Hospital, Copenhagen, Denmark
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13
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B. Knudsen A, Mackey AL, Jakobsen JR, Krogsgaard MR. No demonstrable ultrastructural adaptation of the human myotendinous junction to immobilization or 4 weeks of heavy resistance training. TRANSLATIONAL SPORTS MEDICINE 2021. [DOI: 10.1002/tsm2.243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Andreas B. Knudsen
- Department of Sports Traumatology M51 Bispebjerg and Frederiksberg HospitalIOC Research Center Copenhagen Copenhagen Denmark
| | - Abigail Louise Mackey
- Institute of Sports Medicine Department of Orthopedic Surgery M Bispebjerg and Frederiksberg HospitalIOC Research Center Copenhagen Copenhagen Denmark
- Xlab Center for Healthy Aging Department of Biomedical Sciences Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
| | - Jens Rithamer Jakobsen
- Department of Sports Traumatology M51 Bispebjerg and Frederiksberg HospitalIOC Research Center Copenhagen Copenhagen Denmark
| | - Michael Rindom Krogsgaard
- Department of Sports Traumatology M51 Bispebjerg and Frederiksberg HospitalIOC Research Center Copenhagen Copenhagen Denmark
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May CA, Bramke S. In the human, true myocutaneous junctions of skeletal muscle fibers are limited to the face. J Anat 2021; 239:445-450. [PMID: 33641167 PMCID: PMC8273604 DOI: 10.1111/joa.13419] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 01/22/2021] [Accepted: 02/15/2021] [Indexed: 12/21/2022] Open
Abstract
Within the panniculus carnosus‐associated skeletal muscles in the human, the palmaris brevis and the platysma showed myotendinous/myofascial junctions with clear distance to the corium and the specific connection collagen type XXII. The orbicularis oris muscle, in contrast, contained bundles of striated muscle fibers reaching the corium at two distinct levels: the predominant inner ending was connected to the elastic network of the inner corium and the outer ending was within the more superficial collagen network. At both locations, the striated muscle fibers showed brush‐like cytoplasmic protrusions connecting a network which was not oriented toward the muscle fibers. Collagen type XXII was not present.
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Affiliation(s)
| | - Silvia Bramke
- Department of Anatomy, Medical Faculty Carl Gustav Carus, TU Dresden, Dresden, Germany
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15
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Greising SM, Wang VM. Cross-talk with skeletal muscle and its nexus with regenerative rehabilitation. Connect Tissue Res 2021; 62:1-3. [PMID: 33269630 DOI: 10.1080/03008207.2020.1834909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Sarah M Greising
- School of Kinesiology, University of Minnesota , Minneapolis, MN, USA
| | - Vincent M Wang
- Department of Biomedical Engineering and Mechanics, Virginia Tech , Blacksburg, VA, USA
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16
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Narayanan N, Calve S. Extracellular matrix at the muscle - tendon interface: functional roles, techniques to explore and implications for regenerative medicine. Connect Tissue Res 2021; 62:53-71. [PMID: 32856502 PMCID: PMC7718290 DOI: 10.1080/03008207.2020.1814263] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The muscle-tendon interface is an anatomically specialized region that is involved in the efficient transmission of force from muscle to tendon. Due to constant exposure to loading, the interface is susceptible to injury. Current treatment methods do not meet the socioeconomic demands of reduced recovery time without compromising the risk of reinjury, requiring the need for developing alternative strategies. The extracellular matrix (ECM) present in muscle, tendon, and at the interface of these tissues consists of unique molecules that play significant roles in homeostasis and repair. Better, understanding the function of the ECM during development, injury, and aging has the potential to unearth critical missing information that is essential for accelerating the repair at the muscle-tendon interface. Recently, advanced techniques have emerged to explore the ECM for identifying specific roles in musculoskeletal biology. Simultaneously, there is a tremendous increase in the scope for regenerative medicine strategies to address the current clinical deficiencies. Advancements in ECM research can be coupled with the latest regenerative medicine techniques to develop next generation therapies that harness ECM for treating defects at the muscle-tendon interface. The current work provides a comprehensive review on the role of muscle and tendon ECM to provide insights about the role of ECM in the muscle-tendon interface and discusses the latest research techniques to explore the ECM to gathered information for developing regenerative medicine strategies.
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Affiliation(s)
- Naagarajan Narayanan
- Paul M. Rady Department of Mechanical Engineering, University of Colorado – Boulder, 1111 Engineering Drive, Boulder, Colorado 80309 – 0427
| | - Sarah Calve
- Paul M. Rady Department of Mechanical Engineering, University of Colorado – Boulder, 1111 Engineering Drive, Boulder, Colorado 80309 – 0427
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17
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Myotendinous junction adaptations to ladder-based resistance training: identification of a new telocyte niche. Sci Rep 2020; 10:14124. [PMID: 32839490 PMCID: PMC7445244 DOI: 10.1038/s41598-020-70971-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 08/04/2020] [Indexed: 12/31/2022] Open
Abstract
The present study shows chronic adjustments in the myotendinous junction (MTJ) in response to different ladder-based resistance training (LRT) protocols. Thirty adult male Wistar rats were divided into groups: sedentary (S), calisthenics (LRT without additional load [C]), and resistance-trained (LRT with extra weight [R]). We demonstrated longer lengths of sarcoplasmatic invaginations in the trained groups; however, evaginations were seen mainly in group R. We showed a greater thickness of sarcoplasmatic invaginations in groups C and R, in addition to greater evaginations in R. We also observed thinner basal lamina in trained groups. The support collagen layer (SCL) adjacent to the MTJ and the diameters of the transverse fibrils were larger in R. We also discovered a niche of telocytes in the MTJ with electron micrographs of the plantar muscle and with immunostaining with CD34+ in the gastrocnemius muscle near the blood vessels and pericytes. We concluded that the continuous adjustments in the MTJ ultrastructure were the result of tissue plasticity induced by LRT, which is causally related to muscle hypertrophy and, consequently, to the remodeling of the contact interface. Also, we reveal the existence of a collagen layer adjacent to MTJ and discover a new micro anatomic location of telocytes.
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18
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Rocha LC, Pimentel Neto J, de Sant'Ana JS, Jacob CDS, Barbosa GK, Krause Neto W, Watanabe IS, Ciena AP. Repercussions on sarcomeres of the myotendinous junction and the myofibrillar type adaptations in response to different trainings on vertical ladder. Microsc Res Tech 2020; 83:1190-1197. [PMID: 32500573 DOI: 10.1002/jemt.23510] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 04/14/2020] [Accepted: 04/16/2020] [Indexed: 12/25/2022]
Abstract
The myofibrillary types establish to the skeletal muscle functional and adaptive properties that influence the sarcomeric arrangement during muscle contraction and may have repercussions on an important related force transmission region of the locomotor apparatus, the myotendinous junction (MTJ). This study aimed to describe changes in myofibrillary type and sarcomeric lengths in the belly muscle and MTJ of the soleus and plantaris muscles associated with training protocols in vertical ladder. Thirty adults male Wistar rats were divided into three groups (n = 10): Control (CTR), No-load Training (NLT), and Load Training (LT). Morphoquantitative analysis of different fibers types and sarcomere lengths were performed in distinct regions of plantaris and soleus muscles. In the plantaris muscle with both trainings, there was an increase in the cross-sectional area (CSA) in Type I and II fibers (p < .0001) while sarcomeric lengths revealed greater lengths in the proximal and distal sarcomeres of NLT, although in the LT we found greater lengths in the belly and MTJ sarcomeres. The soleus muscle showed an increase in CSA muscle fiber only in the NLT (p < .0001) and revealed alterations in belly and MTJ sarcomere lengths with training. We concluded that plantaris muscle has an adaptive effect directly associated with training load, with hypertrophy in both trainings and sarcomere length inverse from belly and MTJ, in LT associated with increased force generation and transmission at the MTJ, although soleus muscle has a lower adaptive response to training stimuli with variation in the belly and distal sarcomere of the MTJ.
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Affiliation(s)
- Lara Caetano Rocha
- Laboratory of Morphology and Physical Activity (LAMAF), Institute of Biosciences, São Paulo State University (UNESP), Rio Claro, Brazil
| | - Jurandyr Pimentel Neto
- Laboratory of Morphology and Physical Activity (LAMAF), Institute of Biosciences, São Paulo State University (UNESP), Rio Claro, Brazil
| | - Jossei Soares de Sant'Ana
- Laboratory of Morphology and Physical Activity (LAMAF), Institute of Biosciences, São Paulo State University (UNESP), Rio Claro, Brazil
| | - Carolina Dos Santos Jacob
- Laboratory of Morphology and Physical Activity (LAMAF), Institute of Biosciences, São Paulo State University (UNESP), Rio Claro, Brazil
| | - Gabriela Klein Barbosa
- Laboratory of Morphology and Physical Activity (LAMAF), Institute of Biosciences, São Paulo State University (UNESP), Rio Claro, Brazil
| | - Walter Krause Neto
- Department of Physical Education, Laboratory of Morphoquantitative Studies and Immunohistochemistry, São Judas Tadeu University, São Paulo, Brazil
| | - Ii-Sei Watanabe
- Department of Anatomy, Institute of Biomedical Sciences-III, University of São Paulo (USP), São Paulo, Brazil
| | - Adriano Polican Ciena
- Laboratory of Morphology and Physical Activity (LAMAF), Institute of Biosciences, São Paulo State University (UNESP), Rio Claro, Brazil
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19
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Forsythe CM, Burtis MT, Pfeiffer DC, Spurling GR, Ashby DB. Acute brachialis muscle tear in a pediatric patient. Radiol Case Rep 2020; 15:498-501. [PMID: 32140195 PMCID: PMC7044504 DOI: 10.1016/j.radcr.2020.01.041] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 01/28/2020] [Accepted: 01/29/2020] [Indexed: 11/28/2022] Open
Abstract
Acute tears or ruptures of the brachialis muscle are rare events, with only 10 cases reported to date and all of which have been in adults. We report a case of an acute, complete tear of brachialis in an 8-year-old female that occurred while the patient was practicing a gymnastic move. Although rare, this case underscores the need to include brachialis tears in the differential diagnosis for musculoskeletal injuries at the elbow in all age groups.
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Affiliation(s)
- Charlie M. Forsythe
- WWAMI Medical Education Program (MD), University of Washington School of Medicine, 1959 NE Pacific St, Seattle, WA 98195, USA
| | - Michael T. Burtis
- St Joseph Regional Medical Center, 415 6th St, Lewiston, ID 83501, USA
| | - David C. Pfeiffer
- WWAMI Medical Education Program and Department of Biological Sciences, University of Idaho, 875 Perimeter Drive, Moscow, ID 83844-3051, USA
- Corresponding author.
| | | | - Dallen B. Ashby
- St Joseph Regional Medical Center, 415 6th St, Lewiston, ID 83501, USA
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20
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Jacob CDS, Rocha LC, Neto JP, Watanabe IS, Ciena AP. Effects of physical training on sarcomere lengths and muscle-tendon interface of the cervical region in an experimental model of menopause. Eur J Histochem 2019; 63:3038. [PMID: 31455072 PMCID: PMC6712362 DOI: 10.4081/ejh.2019.3038] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Accepted: 07/05/2019] [Indexed: 02/05/2023] Open
Abstract
The aim of this study was to describe the structural and ultrastructural aspects of the myotendinous junction (MTJ) and the proximal and distal sarcomeres of the sternomastoid of aged Wistar rats subjected to an experimental model of menopause and swimming training. A total of 20 female elderly rats were divided into the following four groups (n=5 in each group): sedentary/no-menopausal (SNM), trained/no-menopausal (TNM), sedentary/menopausal (SM), and trained/menopausal (TM). The MTJ samples were dissected and analyzed using transmission electron microscopy. We showed that the TNM Group rats exhibited changes in morphological characteristics as a consequence of physical exercise, which included an increase of 36.60% (P<0.001) in the evagination length of the MTJ and a reduction in the length of the distal (77.38%) (P<0.0001) and proximal (68.15%) (P<0.0001) sarcomeres. The SM Group exhibited a reduction of about 275.93% (P<0.001) in the muscle-tendon interface and in the lengths of distal sarcomeres (55.87%) (P<0.0001) compared with SNM Group. Our results suggest that the swimming training under experimental model of menopause promoted tissue reorganization and increased muscle-tendon interaction with a drastic development in the length and thickness of the sarcoplasmatic invaginations and evaginations. In addition, the sarcomeres exhibited different lengths and a reduction in both groups subjected to swimming training.
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Affiliation(s)
- Carolina Dos Santos Jacob
- Department of Physical Education, Laboratory of Morphology and Physical Activity, São Paulo State University "Julio de Mesquita Filho", Rio Claro.
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21
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Serner A, Mosler AB, Tol JL, Bahr R, Weir A. Mechanisms of acute adductor longus injuries in male football players: a systematic visual video analysis. Br J Sports Med 2018; 53:158-164. [PMID: 30006458 DOI: 10.1136/bjsports-2018-099246] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 05/28/2018] [Accepted: 06/09/2018] [Indexed: 11/03/2022]
Abstract
BACKGROUND Change of direction and kicking have been described as the main actions resulting in adductor longus injury. Video descriptions of inciting events are lacking. OBJECTIVE Perform a standardised visual video analysis of a series of acute adductor longus injuries in football. STUDY DESIGN Cross-sectional. METHODS Video footage was reviewed by players, and assessed independently by five sports medicine professionals. Inciting events were described and categorised using standardised scoring, including playing situation, player/opponent behaviour, movement and body positions. RESULTS Videos of acute adductor longus injuries in 17 professional male football players were analysed. Most injuries occurred in non-contact situations (71%), following a quick reaction to a change in play (53%). Injury actions were: change of direction (35%), kicking (29%), reaching (24%) and jumping (12%). Change of direction and reaching injuries were categorised as closed chain movements (59%), characterised by hip extension and abduction with external rotation. Kicking and jumping injuries were categorised as open chain (41%), characterised by a change from hip extension to hip flexion, and hip abduction to adduction, with external rotation. CONCLUSION Acute adductor longus injuries in football occur in a variety of situations. Player actions can be categorised into closed (change of direction and reaching) and open (kicking and jumping) chain movements involving triplanar hip motion. A rapid muscle activation during a rapid muscle lengthening appears to be the fundamental injury mechanism for acute adductor longus injuries.
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Affiliation(s)
- Andreas Serner
- Aspetar Sports Groin Pain Centre/Research dept./Rehabilitation dept./Sports Medicine dept./Aspetar Sports Injury and Illness Prevention Programme (ASPREV), Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar.,Sports Orthopaedic Research Center-Copenhagen (SORC-C), Arthroscopic Center Amager, Department of Orthopaedic Surgery, Copenhagen University Hospital, Amager-Hvidovre, Denmark
| | - Andrea Britt Mosler
- Aspetar Sports Groin Pain Centre/Research dept./Rehabilitation dept./Sports Medicine dept./Aspetar Sports Injury and Illness Prevention Programme (ASPREV), Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar.,La Trobe Sport and Exercise Medicine Research Centre, School of Allied Health, La Trobe University, Melbourne, Victoria, Australia
| | - Johannes L Tol
- Aspetar Sports Groin Pain Centre/Research dept./Rehabilitation dept./Sports Medicine dept./Aspetar Sports Injury and Illness Prevention Programme (ASPREV), Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar.,Academic Center for Evidence Based Medicine, Academic Medical Center, Amsterdam, The Netherlands
| | - Roald Bahr
- Aspetar Sports Groin Pain Centre/Research dept./Rehabilitation dept./Sports Medicine dept./Aspetar Sports Injury and Illness Prevention Programme (ASPREV), Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar.,Oslo Sports Trauma Research Centre, Norwegian School of Sports Sciences, Oslo, Norway
| | - Adam Weir
- Aspetar Sports Groin Pain Centre/Research dept./Rehabilitation dept./Sports Medicine dept./Aspetar Sports Injury and Illness Prevention Programme (ASPREV), Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar.,Erasmus MC Center for Groin Injuries, Department of Orthopaedics, Erasmus MC University Medical Centre, Rotterdam, The Netherlands
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22
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Nielsen KB, Lal NN, Sheard PW. Age-related remodelling of the myotendinous junction in the mouse soleus muscle. Exp Gerontol 2018; 104:52-59. [PMID: 29421351 DOI: 10.1016/j.exger.2018.01.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 12/18/2017] [Accepted: 01/18/2018] [Indexed: 11/19/2022]
Abstract
The age-related loss of muscle mass and function predominantly affect muscles of the lower limbs and have largely been associated with decline in muscle fibre size and number, although the exact mechanisms underlying these losses are poorly understood. In addition, consistent reports that the loss of muscle strength exceeds that which can be explained by declines in muscle mass has widened the search for causes of sarcopenia to include supporting tissues such as the extracellular matrix and tendons. Although the changes to both muscle and tendon with age are well characterised, little work has focused on the interface between these two tissues, the myotendinous junction (MTJ). Given the crucial role for this structure in force transfer between muscle and tendon, we asked whether the myotendinous junction underwent structural changes with age in lower limb muscle. We used whole muscle to assess gross muscle and tendon morphology, and immunohistochemistry to determine fibre and MTJ profile number in young (6 months), middle aged (18 months) and elderly (24 months) C57BL/6 female mice. MTJ length was quantified using serial cross sections of the soleus muscle. We found an apparent 3.5-fold increase in MTJ profiles per cross section with no increase in fibre number in old mice, and found this to be a result of a doubling in length of the MTJ region with age. This coincided with an increase in proximal tendon length (31%), as well as an increase in collagen deposition between 6 and 24-months of age consistent with an expansion of the fibre termination area. These findings uncover a previously undescribed effect of ageing on the MTJ and open up new lines of investigation into the role of this structure in the age-related loss of muscle function.
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Affiliation(s)
| | - Navneet N Lal
- Department of Physiology, University of Otago, New Zealand
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