1
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Collins BC, Shapiro JB, Scheib MM, Musci RV, Verma M, Kardon G. Three-dimensional imaging studies in mice identify cellular dynamics of skeletal muscle regeneration. Dev Cell 2024; 59:1457-1474.e5. [PMID: 38569550 PMCID: PMC11153043 DOI: 10.1016/j.devcel.2024.03.017] [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: 04/25/2023] [Revised: 12/06/2023] [Accepted: 03/08/2024] [Indexed: 04/05/2024]
Abstract
The function of many organs, including skeletal muscle, depends on their three-dimensional structure. Muscle regeneration therefore requires not only reestablishment of myofibers but also restoration of tissue architecture. Resident muscle stem cells (SCs) are essential for regeneration, but how SCs regenerate muscle architecture is largely unknown. We address this problem using genetic labeling of mouse SCs and whole-mount imaging to reconstruct, in three dimensions, muscle regeneration. Unexpectedly, we found that myofibers form via two distinct phases of fusion and the residual basement membrane of necrotic myofibers is critical for promoting fusion and orienting regenerated myofibers. Furthermore, the centralized myonuclei characteristic of regenerated myofibers are associated with myofibrillogenesis and endure months post injury. Finally, we elucidate two cellular mechanisms for the formation of branched myofibers, a pathology characteristic of diseased muscle. We provide a synthesis of the cellular events of regeneration and show that these differ from those used during development.
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Affiliation(s)
- Brittany C Collins
- Department of Human Genetics, University of Utah, Salt Lake City, UT, USA
| | - Jacob B Shapiro
- Department of Human Genetics, University of Utah, Salt Lake City, UT, USA
| | - Mya M Scheib
- Department of Human Genetics, University of Utah, Salt Lake City, UT, USA
| | - Robert V Musci
- Department of Human Genetics, University of Utah, Salt Lake City, UT, USA
| | - Mayank Verma
- Department of Pediatrics, Division of Neurology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Gabrielle Kardon
- Department of Human Genetics, University of Utah, Salt Lake City, UT, USA.
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2
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Harriot AD, Altair Morris T, Vanegas C, Kallenbach J, Pinto K, Joca HC, Moutin MJ, Shi G, Ursitti JA, Grosberg A, Ward CW. Detyrosinated microtubule arrays drive myofibrillar malformations in mdx muscle fibers. Front Cell Dev Biol 2023; 11:1209542. [PMID: 37691825 PMCID: PMC10485621 DOI: 10.3389/fcell.2023.1209542] [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: 04/20/2023] [Accepted: 08/09/2023] [Indexed: 09/12/2023] Open
Abstract
Altered myofibrillar structure is a consequence of dystrophic pathology that impairs skeletal muscle contractile function and increases susceptibility to contraction injury. In murine Duchenne muscular dystrophy (mdx), myofibrillar alterations are abundant in advanced pathology (>4 months), an age where we formerly established densified microtubule (MT) arrays enriched in detyrosinated (deTyr) tubulin as negative disease modifiers impacting cell mechanics and mechanotransduction. Given the essential role of deTyr-enriched MT arrays in myofibrillar growth, maintenance, and repair, we examined the increased abundance of these arrays as a potential mechanism for these myofibrillar alterations. Here we find an increase in deTyr-tubulin as an early event in dystrophic pathology (4 weeks) with no evidence myofibrillar alterations. At 16 weeks, we show deTyr-enriched MT arrays significantly densified and co-localized to areas of myofibrillar malformation. Profiling the enzyme complexes responsible for deTyr-tubulin, we identify vasohibin 2 (VASH2) and small vasohibin binding protein (SVBP) significantly elevated in the mdx muscle at 4 weeks. Using the genetic increase in VASH2/SVBP expression in 4 weeks wild-type mice we find densified deTyr-enriched MT arrays that co-segregate with myofibrillar malformations similar to those in the 16 weeks mdx. Given that no changes in sarcomere organization were identified in fibers expressing sfGFP as a control, we conclude that disease-dependent densification of deTyr-enriched MT arrays underscores the altered myofibrillar structure in dystrophic skeletal muscle fibers.
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Affiliation(s)
- Anicca D. Harriot
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Tessa Altair Morris
- Center for Complex Biological Systems, Edwards Lifesciences Foundation Cardiovascular Innovation and Research Center, and the NSF-Simons Center for Multiscale Cell Fate Research, University of California, Irvine, Irvine, CA, United States
| | - Camilo Vanegas
- Department of Orthopedics, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Jacob Kallenbach
- Department of Orthopedics, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Kaylie Pinto
- Department of Molecular Medicine, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Humberto C. Joca
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Marie-Jo Moutin
- INSERM U1216 Centre National de la Recherche Scientifique, Grenoble Institut Neurosciences, University Grenoble Alpes, Grenoble, France
| | - Guoli Shi
- Department of Orthopedics, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Jeanine A. Ursitti
- Department of Orthopedics, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Anna Grosberg
- Center for Complex Biological Systems, Edwards Lifesciences Foundation Cardiovascular Innovation and Research Center, and the NSF-Simons Center for Multiscale Cell Fate Research, University of California, Irvine, Irvine, CA, United States
- Department of Biomedical Engineering, Sue and Bill Gross Stem Cell Research, University of California, Irvine, Irvine, CA, United States
- Department of Chemical and Biomolecular Engineering, Sue and Bill Gross Stem Cell Research, University of California, Irvine, Irvine, CA, United States
| | - Christopher W. Ward
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, United States
- Department of Orthopedics, University of Maryland School of Medicine, Baltimore, MD, United States
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3
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Pizza FX, Buckley KH. Regenerating Myofibers after an Acute Muscle Injury: What Do We Really Know about Them? Int J Mol Sci 2023; 24:12545. [PMID: 37628725 PMCID: PMC10454182 DOI: 10.3390/ijms241612545] [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: 07/12/2023] [Revised: 08/02/2023] [Accepted: 08/04/2023] [Indexed: 08/27/2023] Open
Abstract
Injury to skeletal muscle through trauma, physical activity, or disease initiates a process called muscle regeneration. When injured myofibers undergo necrosis, muscle regeneration gives rise to myofibers that have myonuclei in a central position, which contrasts the normal, peripheral position of myonuclei. Myofibers with central myonuclei are called regenerating myofibers and are the hallmark feature of muscle regeneration. An important and underappreciated aspect of muscle regeneration is the maturation of regenerating myofibers into a normal sized myofiber with peripheral myonuclei. Strikingly, very little is known about processes that govern regenerating myofiber maturation after muscle injury. As knowledge of myofiber formation and maturation during embryonic, fetal, and postnatal development has served as a foundation for understanding muscle regeneration, this narrative review discusses similarities and differences in myofiber maturation during muscle development and regeneration. Specifically, we compare and contrast myonuclear positioning, myonuclear accretion, myofiber hypertrophy, and myofiber morphology during muscle development and regeneration. We also discuss regenerating myofibers in the context of different types of myofiber necrosis (complete and segmental) after muscle trauma and injurious contractions. The overall goal of the review is to provide a framework for identifying cellular and molecular processes of myofiber maturation that are unique to muscle regeneration.
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Affiliation(s)
- Francis X. Pizza
- Department of Exercise and Rehabilitation Sciences, University of Toledo, Toledo, OH 43606, USA
| | - Kole H. Buckley
- Division of Gastroenterology and Hepatology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA;
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4
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Schneidereit D, Nübler S, Friedrich O. Second Harmonic Generation Morphometry of Muscle Cytoarchitecture in Living Cells. Methods Mol Biol 2023; 2644:267-285. [PMID: 37142928 DOI: 10.1007/978-1-0716-3052-5_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The architectural structure of cells is essential for the cells' function, which becomes especially apparent in the highly "structure functionally" tuned skeletal muscle cells. Here, structural changes in the microstructure can have a direct impact on performance parameters, such as isometric or tetanic force production. The microarchitecture of the actin-myosin lattice in muscle cells can be detected noninvasively in living cells and in 3D by using second harmonic generation (SHG) microscopy, forgoing the need to alter samples by introducing fluorescent probes into them. Here, we provide tools and step-by-step protocols to guide the processes of obtaining SHG microscopy image data from samples, as well as extracting characteristic values from the image data to quantify the cellular microarchitecture using characteristic patterns of myofibrillar lattice alignments.
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Affiliation(s)
- Dominik Schneidereit
- Institute of Medical Biotechnology, Department of Chemical and Biological Engineering, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany.
| | - Stefanie Nübler
- Institute of Medical Biotechnology, Department of Chemical and Biological Engineering, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Oliver Friedrich
- Institute of Medical Biotechnology, Department of Chemical and Biological Engineering, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
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5
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Pharmacological inhibition of HDAC6 improves muscle phenotypes in dystrophin-deficient mice by downregulating TGF-β via Smad3 acetylation. Nat Commun 2022; 13:7108. [PMID: 36402791 PMCID: PMC9675748 DOI: 10.1038/s41467-022-34831-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 11/01/2022] [Indexed: 11/21/2022] Open
Abstract
The absence of dystrophin in Duchenne muscular dystrophy disrupts the dystrophin-associated glycoprotein complex resulting in skeletal muscle fiber fragility and atrophy, associated with fibrosis as well as microtubule and neuromuscular junction disorganization. The specific, non-conventional cytoplasmic histone deacetylase 6 (HDAC6) was recently shown to regulate acetylcholine receptor distribution and muscle atrophy. Here, we report that administration of the HDAC6 selective inhibitor tubastatin A to the Duchenne muscular dystrophy, mdx mouse model increases muscle strength, improves microtubule, neuromuscular junction, and dystrophin-associated glycoprotein complex organization, and reduces muscle atrophy and fibrosis. Interestingly, we found that the beneficial effects of HDAC6 inhibition involve the downregulation of transforming growth factor beta signaling. By increasing Smad3 acetylation in the cytoplasm, HDAC6 inhibition reduces Smad2/3 phosphorylation, nuclear translocation, and transcriptional activity. These findings provide in vivo evidence that Smad3 is a new target of HDAC6 and implicate HDAC6 as a potential therapeutic target in Duchenne muscular dystrophy.
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6
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Ashida Y, Himori K, Tokuda N, Naito A, Yamauchi N, Takenaka-Ninagawa N, Aoki Y, Sakurai H, Yamada T. Dissociation of SH3 and cysteine rich domain 3 and junctophilin 1 from dihydropyridine receptor in dystrophin-deficient muscles. Am J Physiol Cell Physiol 2022; 323:C885-C895. [PMID: 35912995 DOI: 10.1152/ajpcell.00163.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The disruption of excitation-contraction (EC) coupling and subsequent reduction in Ca2+ release from the sarcoplasmic reticulum (SR) have been shown to account for muscle weakness seen in patients with Duchenne muscular dystrophy (DMD). Here, we examined the mechanisms underlying EC uncoupling in skeletal muscles from mdx52 and DMD-null/NSG mice, animal models for DMD, focusing on the SH3 and cysteine rich domain 3 (STAC3) and junctophilin 1 (JP1), which link the dihydropyridine receptor (DHPR) in the transverse tubule and the ryanodine receptor 1 in the SR. The isometric plantarflexion torque normalized to muscle weight of whole plantar flexor muscles was depressed in mdx52 and DMD-null/NSG mice compared to their control mice. This was accompanied by increased autolysis of calpain-1, decreased levels of STAC3 and JP1 content, and dissociation of STAC3 and JP1 from DHPR-α1s in gastrocnemius muscles. Moreover, in vitro mechanistic experiments demonstrated that STAC3 and JP1 underwent Ca2+-dependent proteolysis which was less pronounced in dystrophin-deficient muscles where calpastatin, the endogenous calpain inhibitor, was upregulated. Eccentric contractions further enhanced autolysis of calpain-1 and proteolysis of STAC3 and JP1 that were associated with severe torque depression in gastrocnemius muscles from DMD-null/NSG mice. These data suggest that Ca2+-dependent proteolysis of STAC3 and JP1 may be an essential factor causing muscle weakness due to EC coupling failure in dystrophin-deficient muscles.
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Affiliation(s)
- Yuki Ashida
- Graduate School of Health Sciences, Sapporo Medical University, Sapporo, Japan.,Research Fellow of Japan Society for the Promotion of Science, Tokyo, Japan
| | - Koichi Himori
- Graduate School of Health Sciences, Sapporo Medical University, Sapporo, Japan.,Research Fellow of Japan Society for the Promotion of Science, Tokyo, Japan
| | - Nao Tokuda
- Graduate School of Health Sciences, Sapporo Medical University, Sapporo, Japan
| | - Azuma Naito
- Graduate School of Health Sciences, Sapporo Medical University, Sapporo, Japan
| | - Nao Yamauchi
- Graduate School of Health Sciences, Sapporo Medical University, Sapporo, Japan
| | | | - Yoshitsugu Aoki
- Department of Molecular Therapy, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Hidetoshi Sakurai
- Center for iPS Cell Research and Application (CiRA), Kyoto University, Kyoto, Japan
| | - Takashi Yamada
- Graduate School of Health Sciences, Sapporo Medical University, Sapporo, Japan
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7
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Chan S, Kueh SLL, Morley JW, Head SI. Sarcoplasmic reticulum calcium handling in unbranched, immediately post-necrotic fast-twitch mdx fibres is similar to wild-type littermates. Exp Physiol 2022; 107:601-614. [PMID: 35471703 DOI: 10.1113/ep090057] [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: 09/13/2021] [Accepted: 04/19/2022] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS Central question: What are the early effects of dystrophin deficiency on SR Ca2+ handling in the mdx mouse? MAIN FINDING In the mdx mouse, Ca2+ handling by the SR is little affected by the absence of dystrophin when looking at fibres without branches that have just regenerated following massive myonecrosis. This has important implications for our understanding of Ca2+ pathology in the mdx mouse. ABSTRACT There is a variety of results in the literature regarding the effects of dystrophin deficiency on the Ca2+ -handling properties of the SR in mdx mice, an animal model of Duchenne muscular dystrophy. One possible source of variation is the presence of branched fibres. Fibre branching, a consequence of degenerative-regenerative processes such as muscular dystrophy, has in itself a significant influence on the function of the SR. In our present study we attempt to detect early effects of dystrophin deficiency on SR Ca2+ handling by using unbranched fibres from the immediate post-necrotic stage in mdx mice (just regenerated following massive necrosis). Using kinetically-corrected Fura-2 fluorescence signals measured during twitch and tetanus, we analysed the amplitude, rise time and decay time of Δ[Ca2+ ]i in unfatigued and fatigued fibres. Decay was also resolved into SR pump and SR leak components. Fibres from mdx mice were similar in all respects to fibres from wt littermates apart from: (i) a smaller amplitude of the initial spike of Δ[Ca2+ ]i during a tetanus; and (ii) a mitigation of the fall in Δ[Ca2+ ]i amplitude during the course of fatigue. Our findings suggest that the early effects of a loss of dystrophin on SR Ca2+ handling in mdx mice are subtle, and emphasise the importance of distinguishing between Ca2+ pathology that is due to lack of dystrophin and Ca2+ pathology that is due to muscle degeneration. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Stephen Chan
- School of Medicine, Western Sydney University, Campbelltown, New South Wales, Australia.,Department of Physiology, Faculty of Science, Mahidol University, Ratchatewi, Bangkok, Thailand
| | - Sindy L L Kueh
- School of Medicine, Western Sydney University, Campbelltown, New South Wales, Australia
| | - John W Morley
- School of Medicine, Western Sydney University, Campbelltown, New South Wales, Australia
| | - Stewart I Head
- School of Medicine, Western Sydney University, Campbelltown, New South Wales, Australia
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8
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Kiriaev L, Kueh S, Morley JW, North KN, Houweling PJ, Head SI. Lifespan Analysis of Dystrophic mdx Fast-Twitch Muscle Morphology and Its Impact on Contractile Function. Front Physiol 2021; 12:771499. [PMID: 34950049 PMCID: PMC8689589 DOI: 10.3389/fphys.2021.771499] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Accepted: 11/08/2021] [Indexed: 11/13/2022] Open
Abstract
Duchenne muscular dystrophy is caused by the absence of the protein dystrophin from skeletal muscle and is characterized by progressive cycles of necrosis/regeneration. Using the dystrophin deficient mdx mouse model, we studied the morphological and contractile chronology of dystrophic skeletal muscle pathology in fast-twitch Extensor Digitorum Longus muscles from animals 4–22 months of age containing 100% regenerated muscle fibers. Catastrophically, the older age groups lost ∼80% of their maximum force after one eccentric contraction (EC) of 20% strain with the greatest loss of ∼92% recorded in senescent 22-month-old mdx mice. In old age groups, there was minimal force recovery ∼24% after 120 min, correlated with a dramatic increase in the number and complexity of branched fibers. This data supports our two-phase model where a “tipping point” is reached when branched fibers rupture irrevocably on EC. These findings have important implications for pre-clinical drug studies and genetic rescue strategies.
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Affiliation(s)
- Leonit Kiriaev
- Myogenica Laboratory, School of Medicine, Western Sydney University, Sydney, NSW, Australia
- *Correspondence: Leonit Kiriaev,
| | - Sindy Kueh
- Myogenica Laboratory, School of Medicine, Western Sydney University, Sydney, NSW, Australia
| | - John W. Morley
- Myogenica Laboratory, School of Medicine, Western Sydney University, Sydney, NSW, Australia
| | - Kathryn N. North
- Muscle Research Group, Murdoch Children’s Research Institute, Melbourne, VIC, Australia
| | - Peter J. Houweling
- Muscle Research Group, Murdoch Children’s Research Institute, Melbourne, VIC, Australia
| | - Stewart I. Head
- Myogenica Laboratory, School of Medicine, Western Sydney University, Sydney, NSW, Australia
- Muscle Research Group, Murdoch Children’s Research Institute, Melbourne, VIC, Australia
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9
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Geist Hauserman J, Stavusis J, Joca HC, Robinett JC, Hanft L, Vandermeulen J, Zhao R, Stains JP, Konstantopoulos K, McDonald KS, Ward C, Kontrogianni-Konstantopoulos A. Sarcomeric deficits underlie MYBPC1-associated myopathy with myogenic tremor. JCI Insight 2021; 6:e147612. [PMID: 34437302 PMCID: PMC8525646 DOI: 10.1172/jci.insight.147612] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 08/25/2021] [Indexed: 12/02/2022] Open
Abstract
Myosin binding protein-C slow (sMyBP-C) comprises a subfamily of cytoskeletal proteins encoded by MYBPC1 that is expressed in skeletal muscles where it contributes to myosin thick filament stabilization and actomyosin cross-bridge regulation. Recently, our group described the causal association of dominant missense pathogenic variants in MYBPC1 with an early-onset myopathy characterized by generalized muscle weakness, hypotonia, dysmorphia, skeletal deformities, and myogenic tremor, occurring in the absence of neuropathy. To mechanistically interrogate the etiologies of this MYBPC1-associated myopathy in vivo, we generated a knock-in mouse model carrying the E248K pathogenic variant. Using a battery of phenotypic, behavioral, and physiological measurements spanning neonatal to young adult life, we found that heterozygous E248K mice faithfully recapitulated the onset and progression of generalized myopathy, tremor occurrence, and skeletal deformities seen in human carriers. Moreover, using a combination of biochemical, ultrastructural, and contractile assessments at the level of the tissue, cell, and myofilaments, we show that the loss-of-function phenotype observed in mutant muscles is primarily driven by disordered and misaligned sarcomeres containing fragmented and out-of-register internal membranes that result in reduced force production and tremor initiation. Collectively, our findings provide mechanistic insights underscoring the E248K-disease pathogenesis and offer a relevant preclinical model for therapeutic discovery.
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Affiliation(s)
- Janelle Geist Hauserman
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Janis Stavusis
- Latvian Biomedical Research and Study Centre, Riga, Latvia
| | - Humberto C. Joca
- Department of Orthopedics, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Joel C. Robinett
- Department of Medical Pharmacology and Physiology, University of Missouri, School of Medicine Columbia, Missouri, USA
| | - Laurin Hanft
- Department of Medical Pharmacology and Physiology, University of Missouri, School of Medicine Columbia, Missouri, USA
| | - Jack Vandermeulen
- Department of Orthopedics, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Runchen Zhao
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland, USA
| | - Joseph P. Stains
- Department of Orthopedics, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | | | - Kerry S. McDonald
- Department of Medical Pharmacology and Physiology, University of Missouri, School of Medicine Columbia, Missouri, USA
| | - Christopher Ward
- Department of Orthopedics, University of Maryland School of Medicine, Baltimore, Maryland, USA
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10
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Kiriaev L, Kueh S, Morley JW, Houweling PJ, Chan S, North KN, Head SI. Dystrophin-negative slow-twitch soleus muscles are not susceptible to eccentric contraction induced injury over the lifespan of the mdx mouse. Am J Physiol Cell Physiol 2021; 321:C704-C720. [PMID: 34432537 DOI: 10.1152/ajpcell.00122.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 08/09/2021] [Indexed: 11/22/2022]
Abstract
Duchenne muscular dystrophy (DMD) is the second most common fatal genetic disease in humans and is characterized by the absence of a functional copy of the protein dystrophin from skeletal muscle. In dystrophin-negative humans and rodents, regenerated skeletal muscle fibers show abnormal branching. The number of fibers with branches and the complexity of branching increases with each cycle of degeneration/regeneration. Previously, using the mdx mouse model of DMD, we have proposed that once the number and complexity of branched fibers present in dystrophic fast-twitch EDL muscle surpasses a stable level, we term the "tipping point," the branches, in and of themselves, mechanically weaken the muscle by rupturing when subjected to high forces during eccentric contractions. Here, we use the slow-twitch soleus muscle from the dystrophic mdx mouse to study prediseased "periambulatory" dystrophy at 2-3 wk, the peak regenerative "adult" phase at 6-9 wk, and "old" at 58-112 wk. Using isolated mdx soleus muscles, we examined contractile function and response to eccentric contraction correlated with the amount and complexity of regenerated branched fibers. The intact muscle was enzymatically dispersed into individual fibers in order to count fiber branching and some muscles were optically cleared to allow laser scanning confocal microscopy. We demonstrate throughout the lifespan of the mdx mouse that dystrophic slow-twitch soleus muscle is no more susceptible to eccentric contraction-induced injury than age-matched littermate controls and that this is correlated with a reduction in the number and complexity of branched fibers compared with fast-twitch dystrophic EDL muscles.
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MESH Headings
- Age Factors
- Animals
- Disease Models, Animal
- Dystrophin/deficiency
- Dystrophin/genetics
- Kinetics
- Male
- Mice, Inbred mdx
- Muscle Contraction
- Muscle Fibers, Fast-Twitch/metabolism
- Muscle Fibers, Fast-Twitch/pathology
- Muscle Fibers, Slow-Twitch/metabolism
- Muscle Fibers, Slow-Twitch/pathology
- Muscle Strength
- Muscular Dystrophy, Duchenne/genetics
- Muscular Dystrophy, Duchenne/metabolism
- Muscular Dystrophy, Duchenne/pathology
- Muscular Dystrophy, Duchenne/physiopathology
- Mutation
- Mice
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Affiliation(s)
- Leonit Kiriaev
- School of Medicine, Western Sydney University, Sydney, New South Wales, Australia
- School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Sindy Kueh
- School of Medicine, Western Sydney University, Sydney, New South Wales, Australia
- School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - John W Morley
- School of Medicine, Western Sydney University, Sydney, New South Wales, Australia
- School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Peter J Houweling
- Murdoch Children's Research Institute, Melbourne, Victoria, Australia
| | - Stephen Chan
- School of Medicine, Western Sydney University, Sydney, New South Wales, Australia
- School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Kathryn N North
- Murdoch Children's Research Institute, Melbourne, Victoria, Australia
| | - Stewart I Head
- School of Medicine, Western Sydney University, Sydney, New South Wales, Australia
- Murdoch Children's Research Institute, Melbourne, Victoria, Australia
- School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
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11
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Saclier M, Ben Larbi S, My Ly H, Moulin E, Mounier R, Chazaud B, Juban G. Interplay between myofibers and pro-inflammatory macrophages controls muscle damage in mdx mice. J Cell Sci 2021; 134:272022. [PMID: 34471933 DOI: 10.1242/jcs.258429] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 07/30/2021] [Indexed: 12/18/2022] Open
Abstract
Duchenne muscular dystrophy is a genetic muscle disease characterized by chronic inflammation and fibrosis mediated by a pro-fibrotic macrophage population expressing pro-inflammatory markers. Our aim was to characterize cellular events leading to the alteration of macrophage properties and to modulate macrophage inflammatory status using the gaseous mediator hydrogen sulfide (H2S). Using co-culture experiments, we first showed that myofibers derived from mdx mice strongly skewed the polarization of resting macrophages towards a pro-inflammatory phenotype. Treatment of mdx mice with NaHS, an H2S donor, reduced the number of pro-inflammatory macrophages in skeletal muscle, which was associated with a decreased number of nuclei per fiber, as well as reduced myofiber branching and fibrosis. Finally, we established the metabolic sensor AMP-activated protein kinase (AMPK) as a critical NaHS target in muscle macrophages. These results identify an interplay between myofibers and macrophages where dystrophic myofibers contribute to the maintenance of a highly inflammatory environment sustaining a pro-inflammatory macrophage status, which in turn favors myofiber damage, myofiber branching and establishment of fibrosis. Our results also highlight the use of H2S donors as a potential therapeutic strategy to improve the dystrophic muscle phenotype by dampening chronic inflammation. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Marielle Saclier
- Department of Biosciences, University of Milan, 20133 Milan, Italy
| | - Sabrina Ben Larbi
- Institut NeuroMyoGène, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U1217, Université de Lyon, 69008 Lyon, France
| | - Ha My Ly
- Institut NeuroMyoGène, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U1217, Université de Lyon, 69008 Lyon, France
| | - Eugénie Moulin
- Institut NeuroMyoGène, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U1217, Université de Lyon, 69008 Lyon, France
| | - Rémi Mounier
- Institut NeuroMyoGène, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U1217, Université de Lyon, 69008 Lyon, France
| | - Bénédicte Chazaud
- Institut NeuroMyoGène, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U1217, Université de Lyon, 69008 Lyon, France
| | - Gaëtan Juban
- Institut NeuroMyoGène, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U1217, Université de Lyon, 69008 Lyon, France
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12
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Ben Larbi S, Saclier M, Fessard A, Juban G, Chazaud B. Histological Analysis of Tibialis Anterior Muscle of DMDmdx4Cv Mice from 1 to 24 Months. J Neuromuscul Dis 2021; 8:513-524. [PMID: 33843691 DOI: 10.3233/jnd-200562] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
BACKGROUND The mdx-C57/B6 mouse model does not show the clinical signs of Duchenne muscular dystrophy (DMD), although muscles exhibit hallmarks of permanent regeneration and alterations in muscle function. The DMDmdx4Cv strain exhibits very few revertant dystrophin positive myofibers, making that model suitable for studies on gene and cell therapies. OBJECTIVE The study appraises the histological evolution of the Tibialis Anterior muscle of WT and DMD mdx4Cv mutant from 1 to 24 months. METHODS Histological analysis included a series of immunostainings of muscle sections for assessing tissue features (fibrosis, lipid deposition, necrosis) and cellular characteristics (size of myofibers, number and distribution of myonuclei, number of satellite cells, vessels, macrophages). RESULTS None of the investigated cell types (satellite cells, endothelial cells, macrophages) showed variations in their density within the tissue in both WT and DMD mdx4Cv muscle. However, analyzing their number per myofiber showed that in DMD mdx4Cv, myofiber capillarization was increased from 1 to 6 months as compared with WT muscle, then dropped from 12 months. Macrophage number did not vary in WT muscle and peaked at 6 months in DMD mdx4Cv muscle. The number of satellite cells per myofiber did not vary in WT muscle while it remained high in DMD mdx4Cv muscle, starting to decrease from 12 months and being significantly lower at 24 months of age. Myofiber size was not different in DMD mdx4Cv from WT except at 24 months, when it strongly decreased in DMD mdx4Cv muscle. Necrosis and lipid deposition were rare in DMD mdx4Cv muscle. Fibrosis did not increase with age in DMD mdx4Cv muscle and was higher than in WT at 6 and 12 months of age. CONCLUSIONS As a whole, the results show a strong decrease of the myofiber size at 24 months, and an increased capillarization until 6 months of age in DMD mdx4Cv as compared with the WT. Thus, DMD mdx4Cv mice poorly recapitulates histological DMD features, and its use should take into account the age of the animals according to the purpose of the investigation.
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Affiliation(s)
- Sabrina Ben Larbi
- Institut NeuroMyoGène, Université Claude Bernard Lyon 1, CNRS UMR 2310, INSERM U1217, Université Lyon, Villeurbanne, France
| | | | - Aurélie Fessard
- Institut NeuroMyoGène, Université Claude Bernard Lyon 1, CNRS UMR 2310, INSERM U1217, Université Lyon, Villeurbanne, France
| | - Gaëtan Juban
- Institut NeuroMyoGène, Université Claude Bernard Lyon 1, CNRS UMR 2310, INSERM U1217, Université Lyon, Villeurbanne, France
| | - Bénédicte Chazaud
- Institut NeuroMyoGène, Université Claude Bernard Lyon 1, CNRS UMR 2310, INSERM U1217, Université Lyon, Villeurbanne, France
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13
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Abstract
Muscle cell fusion is a multistep process involving cell migration, adhesion, membrane remodeling and actin-nucleation pathways to generate multinucleated myotubes. However, molecular brakes restraining cell-cell fusion events have remained elusive. Here we show that transforming growth factor beta (TGFβ) pathway is active in adult muscle cells throughout fusion. We find TGFβ signaling reduces cell fusion, regardless of the cells' ability to move and establish cell-cell contacts. In contrast, inhibition of TGFβ signaling enhances cell fusion and promotes branching between myotubes in mouse and human. Exogenous addition of TGFβ protein in vivo during muscle regeneration results in a loss of muscle function while inhibition of TGFβR2 induces the formation of giant myofibers. Transcriptome analyses and functional assays reveal that TGFβ controls the expression of actin-related genes to reduce cell spreading. TGFβ signaling is therefore requisite to limit mammalian myoblast fusion, determining myonuclei numbers and myofiber size.
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14
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Garcia-Pelagio KP, Pratt SJP, Lovering RM. Effects of myofiber isolation technique on sarcolemma biomechanics. Biotechniques 2020; 69:388-391. [PMID: 33000629 PMCID: PMC7686532 DOI: 10.2144/btn-2020-0087] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Isolated myofibers are commonly used to understand the function of skeletal muscle in vivo. This can involve single isolated myofibers obtained from dissection or from enzymatic dissociation. Isolation via dissection allows control of sarcomere length and preserves tendon attachment but is labor-intensive, time-consuming and yields few viable myofibers. In contrast, enzymatic dissociation is fast and facile, produces hundreds of myofibers, and more importantly reduces the number of muscles/animals needed for studies. Biomechanical properties of the sarcolemma have been studied using myofibers from the extensor digitorum longus, but this has been limited to dissected myofibers, making data collection slow and difficult. We have modified this tool to perform biomechanical measurements of the sarcolemma in dissociated myofibers from the flexor digitorum brevis.
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Affiliation(s)
- Karla P Garcia-Pelagio
- Departmento de Física, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Stephen JP Pratt
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Richard M Lovering
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.,Department of Orthopedics, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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15
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Lovering RM, Iyer SR, Edwards B, Davies KE. Alterations of neuromuscular junctions in Duchenne muscular dystrophy. Neurosci Lett 2020; 737:135304. [PMID: 32818587 DOI: 10.1016/j.neulet.2020.135304] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 08/09/2020] [Accepted: 08/11/2020] [Indexed: 12/18/2022]
Abstract
The focus of this review is on Duchenne muscular dystrophy (DMD), which is caused by the absence of the protein dystrophin and is characterized as a neuromuscular disease in which muscle weakness, increased susceptibility to muscle injury, and inadequate repair appear to underlie the pathology. Considerable attention has been dedicated to studying muscle fiber damage, but data show that both human patients and animal models for DMD present with fragmented neuromuscular junction (NMJ) morphology. In addition to pre- and post-synaptic abnormalities, studies indicate increased susceptibility of the NMJ to contraction-induced injury, with corresponding functional changes in neuromuscular transmission and nerve-evoked electromyographic activity. Such findings suggest that alterations in the NMJ of dystrophic muscle may play a role in muscle weakness via impairment of neuromuscular transmission. Further work is needed to fully understand the role of the NMJ in the weakness, susceptibility to injury, and progressive wasting associated with DMD.
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Affiliation(s)
- Richard M Lovering
- Departments of Orthopaedics and Physiology, University of Maryland School of Medicine, Baltimore, MD, USA; University of Maryland School of Medicine, Baltimore, MD, USA.
| | - Shama R Iyer
- Departments of Orthopaedics and Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Benjamin Edwards
- MDUK Oxford Neuromuscular Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Kay E Davies
- MDUK Oxford Neuromuscular Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
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16
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Xu S, Tang S, Li X, Iyer SR, Lovering RM. Abnormalities in Brain and Muscle Microstructure and Neurochemistry of the DMD Rat Measured by in vivo Diffusion Tensor Imaging and High Resolution Localized 1H MRS. Front Neurosci 2020; 14:739. [PMID: 32760246 PMCID: PMC7372970 DOI: 10.3389/fnins.2020.00739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 06/22/2020] [Indexed: 12/03/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is an X-linked disorder caused by the lack of dystrophin with progressive degeneration of skeletal muscles. Most studies regarding DMD understandably focus on muscle, but dystrophin is also expressed in the central nervous system, potentially resulting in cognitive and behavioral changes. Animal models are being used for developing more comprehensive neuromonitoring protocols and clinical image acquisition procedures. The recently developed DMD rat is an animal model that parallels the progressive muscle wasting seen in DMD. Here, we studied the brain and temporalis muscle structure and neurochemistry of wild type (WT) and dystrophic (DMD) rats using magnetic resonance imaging and spectroscopy. Both structural and neurochemistry alterations were observed in the DMD rat brain and the temporalis muscle. There was a decrease in absolute brain volume (WT = 1579 mm3; DMD = 1501 mm3; p = 0.039, Cohen’s d = 1.867), but not normalized (WT = 4.27; DMD = 4.02; p = 0.306) brain volume. Diffusion tensor imaging (DTI) revealed structural alterations in the DMD temporalis muscle, with increased mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD). In the DMD rat thalamus, DTI revealed an increase in fractional anisotropy (FA) and a decrease in RD. Smaller normalized brain volume correlated to severity of muscle dystrophy (r = −0.975). Neurochemical changes in the DMD rat brain included increased GABA and NAA in the prefrontal cortex, and GABA in the hippocampus. Such findings could indicate disturbed motor and sensory signaling, resulting in a dysfunctional GABAergic neurotransmission, and an unstable osmoregulation in the dystrophin-null brain.
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Affiliation(s)
- Su Xu
- Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD, United States.,Center for Advanced Imaging Research, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Shiyu Tang
- Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD, United States.,Center for Advanced Imaging Research, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Xin Li
- Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Shama R Iyer
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Richard M Lovering
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD, United States
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17
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Barzilai-Tutsch H, Genin O, Pines M, Halevy O. Early pathological signs in young dysf -/- mice are improved by halofuginone. Neuromuscul Disord 2020; 30:472-482. [PMID: 32451154 DOI: 10.1016/j.nmd.2020.04.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 03/14/2020] [Accepted: 04/03/2020] [Indexed: 01/09/2023]
Abstract
Dysferlinopathies are a non-lethal group of late-onset muscular dystrophies. Here, we evaluated the fusion ability of primary myoblasts from young dysf-/- mice and the muscle histopathology prior to, and during early stages of disease onset. The ability of primary myoblasts of 5-week-old dysf-/- mice to form large myotubes was delayed compared to their wild-type counterparts, as evaluated by scanning electron microscopy. However, their fusion activity, as reflected by the presence of actin filaments connecting several cells, was enhanced by the antifibrotic drug halofuginone. Early dystrophic signs were already apparent in 4-week-old dysf-/- mice; their collagen level was double that in wild-type mice and continued to rise until 5 months of age. Continuous treatment with halofuginone from 4 weeks to 5 months of age reduced muscle fibrosis in a phosphorylated-Smad3 inhibition-related manner. Halofuginone also enhanced myofiber hypertrophy, reduced the percentage of centrally nucleated myofibers, and increased muscle performance. Together, the data suggest an inhibitory effect of halofuginone on the muscle histopathology at very early stages of dysferlinopathy, and enhancement of muscle performance. These results offer new opportunities for early pharmaceutical treatment in dysferlinopathies with favorable outcomes at later stages of life.
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Affiliation(s)
- Hila Barzilai-Tutsch
- Department of Animal Sciences, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel
| | - Olga Genin
- Institute of Animal Science, the Volcani Center, Bet Dagan 52505, Israel
| | - Mark Pines
- Institute of Animal Science, the Volcani Center, Bet Dagan 52505, Israel
| | - Orna Halevy
- Department of Animal Sciences, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel.
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18
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Kwon H, de Morentin MM, Nagy JA, Rutkove SB, Sanchez B. Approximate complex electrical potential distribution in the monodomain model with unequal conductivity and relative permittivity anisotropy ratios. Physiol Meas 2019; 40:085008. [PMID: 31408853 DOI: 10.1088/1361-6579/ab3aa1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Electrical conductivity and relative permittivity are properties that indicate muscle health and they have different values parallel and perpendicular to the direction of the myofiber, a concept known as anisotropy. When the intrinsic electrical properties of muscle have ratios of anisotropy that are different then there is no analytical solution that can describe the electrical potential distribution in the tissue. APPROACH Here, we present approximate analytical solutions to monodomain equations with unequal anisotropy ratios. For this, we base our analysis on perturbation theory where the electrical potential is approximated by the sum of the zeroth- and first-order terms of an infinite series. MAIN RESULTS The validity of the approach is confirmed using experimental data for healthy and diseased muscle available online. SIGNIFICANCE A better understanding of electrical potential distribution in anisotropic skeletal muscle tissue will allow the development of improved diagnostic tools for neuromuscular diseases.
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Affiliation(s)
- H Kwon
- College of Science and Technology, Yonsei University, Wonju 26493, Republic of Korea
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19
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Murach KA, Dungan CM, Peterson CA, McCarthy JJ. Muscle Fiber Splitting Is a Physiological Response to Extreme Loading in Animals. Exerc Sport Sci Rev 2019; 47:108-115. [PMID: 30640746 DOI: 10.1249/jes.0000000000000181] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Skeletal muscle fiber branching and splitting typically is associated with damage and regeneration and is considered pathological when observed during loading-induced hypertrophy. We hypothesize that fiber splitting is a nonpathological component of extreme loading and hypertrophy, which is primarily supported by evidence in animals, and propose that the mechanisms and consequences of fiber splitting deserve further exploration.
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Affiliation(s)
- Kevin A Murach
- Center for Muscle Biology.,Department of Rehabilitation Sciences, and
| | - Cory M Dungan
- Center for Muscle Biology.,Department of Rehabilitation Sciences, and
| | | | - John J McCarthy
- Center for Muscle Biology.,Department of Physiology, University of Kentucky, Lexington, KY
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20
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Iyer SR, Shah SB, Ward CW, Stains JP, Spangenburg EE, Folker ES, Lovering RM. Differential YAP nuclear signaling in healthy and dystrophic skeletal muscle. Am J Physiol Cell Physiol 2019; 317:C48-C57. [PMID: 30995108 DOI: 10.1152/ajpcell.00432.2018] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Mechanical forces regulate muscle development, hypertrophy, and homeostasis. Force-transmitting structures allow mechanotransduction at the sarcolemma, cytoskeleton, and nuclear envelope. There is growing evidence that Yes-associated protein (YAP) serves as a nuclear relay of mechanical signals and can induce a range of downstream signaling cascades. Dystrophin is a sarcolemma-associated protein, and its absence underlies the pathology in Duchenne muscular dystrophy. We tested the hypothesis that the absence of dystrophin in muscle would result in reduced YAP signaling in response to loading. Following in vivo contractile loading in muscles of healthy (wild-type; WT) mice and mice lacking dystrophin (mdx), we performed Western blots of whole and fractionated muscle homogenates to examine the ratio of phospho (cytoplasmic) YAP to total YAP and nuclear YAP, respectively. We show that in vivo contractile loading induced a robust increase in YAP expression and its nuclear localization in WT muscles. Surprisingly, in mdx muscles, active YAP expression was constitutively elevated and unresponsive to load. Results from qRT-PCR analysis support the hyperactivation of YAP in vivo in mdx muscles, as evidenced by increased gene expression of YAP downstream targets. In vitro assays of isolated myofibers plated on substrates with high stiffness showed YAP nuclear labeling for both genotypes, indicating functional YAP signaling in mdx muscles. We conclude that while YAP signaling can occur in the absence of dystrophin, dystrophic muscles have altered mechanotransduction, whereby constitutively active YAP results in a failure to respond to load, which could be attributed to the increased state of "pre-stress" with increased cytoskeletal and extracellular matrix stiffness.
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Affiliation(s)
- Shama R Iyer
- Department of Orthopaedics, University of Maryland School of Medicine , Baltimore, Maryland
| | - Sameer B Shah
- Department of Orthopaedic Surgery, University of California San Diego , La Jolla, California.,Department of Bioengineering, University of California San Diego , La Jolla, California
| | - Christopher W Ward
- Department of Orthopaedics, University of Maryland School of Medicine , Baltimore, Maryland
| | - Joseph P Stains
- Department of Orthopaedics, University of Maryland School of Medicine , Baltimore, Maryland
| | - Espen E Spangenburg
- Department of Physiology, East Carolina Diabetes and Obesity Institute, East Carolina University , Greenville, North Carolina
| | - Eric S Folker
- Department of Biology, Boston College , Chestnut Hill, Massachusetts
| | - Richard M Lovering
- Department of Orthopaedics, University of Maryland School of Medicine , Baltimore, Maryland.,Department of Physiology, University of Maryland School of Medicine , Baltimore, Maryland
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21
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Ahn B, Ranjit R, Premkumar P, Pharaoh G, Piekarz KM, Matsuzaki S, Claflin DR, Riddle K, Judge J, Bhaskaran S, Satara Natarajan K, Barboza E, Wronowski B, Kinter M, Humphries KM, Griffin TM, Freeman WM, Richardson A, Brooks SV, Van Remmen H. Mitochondrial oxidative stress impairs contractile function but paradoxically increases muscle mass via fibre branching. J Cachexia Sarcopenia Muscle 2019; 10:411-428. [PMID: 30706998 PMCID: PMC6463475 DOI: 10.1002/jcsm.12375] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 11/12/2018] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Excess reactive oxygen species (ROS) and muscle weakness occur in parallel in multiple pathological conditions. However, the causative role of skeletal muscle mitochondrial ROS (mtROS) on neuromuscular junction (NMJ) morphology and function and muscle weakness has not been directly investigated. METHODS We generated mice lacking skeletal muscle-specific manganese-superoxide dismutase (mSod2KO) to increase mtROS using a cre-Lox approach driven by human skeletal actin. We determined primary functional parameters of skeletal muscle mitochondrial function (respiration, ROS, and calcium retention capacity) using permeabilized muscle fibres and isolated muscle mitochondria. We assessed contractile properties of isolated skeletal muscle using in situ and in vitro preparations and whole lumbrical muscles to elucidate the mechanisms of contractile dysfunction. RESULTS The mSod2KO mice, contrary to our prediction, exhibit a 10-15% increase in muscle mass associated with an ~50% increase in central nuclei and ~35% increase in branched fibres (P < 0.05). Despite the increase in muscle mass of gastrocnemius and quadriceps, in situ sciatic nerve-stimulated isometric maximum-specific force (N/cm2 ), force per cross-sectional area, is impaired by ~60% and associated with increased NMJ fragmentation and size by ~40% (P < 0.05). Intrinsic alterations of components of the contractile machinery show elevated markers of oxidative stress, for example, lipid peroxidation is increased by ~100%, oxidized glutathione is elevated by ~50%, and oxidative modifications of myofibrillar proteins are increased by ~30% (P < 0.05). We also find an approximate 20% decrease in the intracellular calcium transient that is associated with specific force deficit. Excess superoxide generation from the mitochondrial complexes causes a deficiency of succinate dehydrogenase and reduced complex-II-mediated respiration and adenosine triphosphate generation rates leading to severe exercise intolerance (~10 min vs. ~2 h in wild type, P < 0.05). CONCLUSIONS Increased skeletal muscle mtROS is sufficient to elicit NMJ disruption and contractile abnormalities, but not muscle atrophy, suggesting new roles for mitochondrial oxidative stress in maintenance of muscle mass through increased fibre branching.
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Affiliation(s)
- Bumsoo Ahn
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, USA
| | - Rojina Ranjit
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, USA
| | - Pavithra Premkumar
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, USA
| | - Gavin Pharaoh
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, USA.,Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, USA
| | - Katarzyna M Piekarz
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, USA.,Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, USA
| | - Satoshi Matsuzaki
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, USA
| | - Dennis R Claflin
- Department of Surgery, Section of Plastic Surgery, University of Michigan, Ann Arbor, USA
| | - Kaitlyn Riddle
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, USA
| | - Jennifer Judge
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, USA
| | - Shylesh Bhaskaran
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, USA
| | | | - Erika Barboza
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, USA
| | - Benjamin Wronowski
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, USA
| | - Michael Kinter
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, USA
| | - Kenneth M Humphries
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, USA.,Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, USA.,Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, Oklahoma City, USA
| | - Timothy M Griffin
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, USA.,Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, USA.,Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, USA.,Oklahoma City VA Medical Center, Oklahoma City, USA.,Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, Oklahoma City, USA
| | - Willard M Freeman
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, USA.,Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, Oklahoma City, USA
| | - Arlan Richardson
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, USA.,Oklahoma City VA Medical Center, Oklahoma City, USA.,Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, Oklahoma City, USA
| | - Susan V Brooks
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, USA
| | - Holly Van Remmen
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, USA.,Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, USA.,Oklahoma City VA Medical Center, Oklahoma City, USA.,Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, Oklahoma City, USA
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22
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Nanoscale remodeling of ryanodine receptor cluster size underlies cerebral microvascular dysfunction in Duchenne muscular dystrophy. Proc Natl Acad Sci U S A 2018; 115:E9745-E9752. [PMID: 30181262 PMCID: PMC6187127 DOI: 10.1073/pnas.1804593115] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is a hereditary neuromuscular disease that results from mutations in the gene encoding dystrophin. The effects of the disease on cardiac and skeletal muscle have been intensely investigated, but much less is known about how DMD impacts vascular smooth muscle cells (SMCs). Using superresolution nanoscopy, we demonstrate that clusters of ryanodine receptors (RyR2s) on the sarcoplasmic reticulum (SR) of cerebral artery SMCs from the mdx mouse model of DMD are larger compared with controls. Increased RyR2 cluster size is associated with augmented SR Ca2+ release and Ca2+-activated K+ channel activity, resulting in impaired vasoconstriction of cerebral microvessels. Our findings demonstrate that remodeling of RyR2 clusters at the molecular level results in cerebral microvascular dysfunction during DMD. Duchenne muscular dystrophy (DMD) results from mutations in the gene encoding dystrophin which lead to impaired function of skeletal and cardiac muscle, but little is known about the effects of the disease on vascular smooth muscle cells (SMCs). Here we used the mdx mouse model to study the effects of mutant dystrophin on the regulation of cerebral artery and arteriole SMC contractility, focusing on an important Ca2+-signaling pathway composed of type 2 ryanodine receptors (RyR2s) on the sarcoplasmic reticulum (SR) and large-conductance Ca2+-activated K+ (BK) channels on the plasma membrane. Nanoscale superresolution image analysis revealed that RyR2 and BKα were organized into discrete clusters, and that the mean size of RyR2 clusters that colocalized with BKα was larger in SMCs from mdx mice (∼62 RyR2 monomers) than in controls (∼40 RyR2 monomers). We further found that the frequency and signal mass of spontaneous, transient Ca2+-release events through SR RyR2s (“Ca2+ sparks”) were greater in SMCs from mdx mice. Patch-clamp electrophysiological recordings indicated a corresponding increase in Ca2+-dependent BK channel activity. Using pressure myography, we found that cerebral pial arteries and parenchymal arterioles from mdx mice failed to develop appreciable spontaneous myogenic tone. Inhibition of RyRs with tetracaine and blocking of BK channels with paxilline restored myogenic tone to control levels, demonstrating that enhanced RyR and BK channel activity is responsible for the diminished pressure-induced constriction of arteries and arterioles from mdx mice. We conclude that increased size of RyR2 protein clusters in SMCs from mdx mice increases Ca2+ spark and BK channel activity, resulting in cerebral microvascular dysfunction.
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23
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Kiriaev L, Kueh S, Morley JW, North KN, Houweling PJ, Head SI. Branched fibers from old fast-twitch dystrophic muscles are the sites of terminal damage in muscular dystrophy. Am J Physiol Cell Physiol 2018; 314:C662-C674. [PMID: 29412689 DOI: 10.1152/ajpcell.00161.2017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A striking pathological feature of dystrophinopathies is the presence of morphologically abnormal branched skeletal muscle fibers. The deterioration of muscle contractile function in Duchenne muscular dystrophy is accompanied by both an increase in number and complexity of these branched fibers. We propose that when number and complexity of branched fibers reaches a critical threshold, or "tipping point," the branches in and of themselves are the site of contraction-induced rupture. In the present study, we use the dystrophic mdx mouse and littermate controls to study the prediseased dystrophic fast-twitch extensor digitorum longus (EDL) muscle at 2-3 wk, the peak myonecrotic phase at 6-9 wk, and finally, "old," at 58-112 wk. Using a combination of isolated muscle function contractile measurements coupled with single-fiber imaging and confocal microscope imaging of cleared whole muscles, we identified a distinct pathophysiology, acute fiber rupture at branch nodes, which occurs in "old" fast-twitch EDL muscle approaching the end stage of the dystrophinopathy muscle disease, where the EDL muscles are entirely composed of complexed branched fibers. This evidence supports our concept of "tipping point" where the number and extent of fiber branching reach a level where the branching itself terminally compromises muscle function, irrespective of the absence of dystrophin.
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Affiliation(s)
- Leonit Kiriaev
- School of Medical Sciences, University of New South Wales , Sidney, New South Wales , Australia
| | - Sindy Kueh
- School of Medical Sciences, University of New South Wales , Sidney, New South Wales , Australia.,School of Medicine, Western Sydney University, Penrith, New South Wales , Australia
| | - John W Morley
- School of Medicine, Western Sydney University, Penrith, New South Wales , Australia
| | - Kathryn N North
- Murdoch Children's Research Institute , Melbourne, Victoria , Australia
| | - Peter J Houweling
- Murdoch Children's Research Institute , Melbourne, Victoria , Australia
| | - Stewart I Head
- School of Medical Sciences, University of New South Wales , Sidney, New South Wales , Australia.,School of Medicine, Western Sydney University, Penrith, New South Wales , Australia
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24
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Schneidereit D, Nübler S, Prölß G, Reischl B, Schürmann S, Müller OJ, Friedrich O. Optical prediction of single muscle fiber force production using a combined biomechatronics and second harmonic generation imaging approach. LIGHT, SCIENCE & APPLICATIONS 2018; 7:79. [PMID: 30374401 PMCID: PMC6199289 DOI: 10.1038/s41377-018-0080-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 09/19/2018] [Accepted: 09/24/2018] [Indexed: 05/22/2023]
Abstract
Skeletal muscle is an archetypal organ whose structure is tuned to match function. The magnitude of order in muscle fibers and myofibrils containing motor protein polymers determines the directed force output of the summed force vectors and, therefore, the muscle's power performance on the structural level. Structure and function can change dramatically during disease states involving chronic remodeling. Cellular remodeling of the cytoarchitecture has been pursued using noninvasive and label-free multiphoton second harmonic generation (SHG) microscopy. Hereby, structure parameters can be extracted as a measure of myofibrillar order and thus are suggestive of the force output that a remodeled structure can still achieve. However, to date, the parameters have only been an indirect measure, and a precise calibration of optical SHG assessment for an exerted force has been elusive as no technology in existence correlates these factors. We engineered a novel, automated, high-precision biomechatronics system into a multiphoton microscope allows simultaneous isometric Ca2+-graded force or passive viscoelasticity measurements and SHG recordings. Using this MechaMorph system, we studied force and SHG in single EDL muscle fibers from wt and mdx mice; the latter serves as a model for compromised force and abnormal myofibrillar structure. We present Ca2+-graded isometric force, pCa-force curves, passive viscoelastic parameters and 3D structure in the same fiber for the first time. Furthermore, we provide a direct calibration of isometric force to morphology, which allows noninvasive prediction of the force output of single fibers from only multiphoton images, suggesting a potential application in the diagnosis of myopathies.
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Affiliation(s)
- Dominik Schneidereit
- Institute of Medical Biotechnology, Friedrich-Alexander-University (FAU) Erlangen-Nürnberg, Paul-Gordan-Str. 3, 91052 Erlangen, Germany
- Erlangen Graduate School in Advanced Optical Technologies (SAOT), FAU Erlangen-Nürnberg, Paul-Gordan-Str. 7, 91052 Erlangen, Germany
| | - Stefanie Nübler
- Institute of Medical Biotechnology, Friedrich-Alexander-University (FAU) Erlangen-Nürnberg, Paul-Gordan-Str. 3, 91052 Erlangen, Germany
- Erlangen Graduate School in Advanced Optical Technologies (SAOT), FAU Erlangen-Nürnberg, Paul-Gordan-Str. 7, 91052 Erlangen, Germany
| | - Gerhard Prölß
- Institute of Medical Biotechnology, Friedrich-Alexander-University (FAU) Erlangen-Nürnberg, Paul-Gordan-Str. 3, 91052 Erlangen, Germany
| | - Barbara Reischl
- Institute of Medical Biotechnology, Friedrich-Alexander-University (FAU) Erlangen-Nürnberg, Paul-Gordan-Str. 3, 91052 Erlangen, Germany
| | - Sebastian Schürmann
- Institute of Medical Biotechnology, Friedrich-Alexander-University (FAU) Erlangen-Nürnberg, Paul-Gordan-Str. 3, 91052 Erlangen, Germany
- Erlangen Graduate School in Advanced Optical Technologies (SAOT), FAU Erlangen-Nürnberg, Paul-Gordan-Str. 7, 91052 Erlangen, Germany
- Muscle Research Center Erlangen (MURCE), Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Oliver J Müller
- Department of Internal Medicine III, University of Kiel, Arnold-Heller-Str. 3, 24105 Kiel, Germany
- DZHK (German Center for Cardiovascular Research) Partner Site Hamburg/Kiel/Lübeck, Kiel, Germany
| | - Oliver Friedrich
- Institute of Medical Biotechnology, Friedrich-Alexander-University (FAU) Erlangen-Nürnberg, Paul-Gordan-Str. 3, 91052 Erlangen, Germany
- Erlangen Graduate School in Advanced Optical Technologies (SAOT), FAU Erlangen-Nürnberg, Paul-Gordan-Str. 7, 91052 Erlangen, Germany
- Muscle Research Center Erlangen (MURCE), Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
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Pratt SJP, Iyer SR, Shah SB, Lovering RM. Imaging Analysis of the Neuromuscular Junction in Dystrophic Muscle. Methods Mol Biol 2018; 1687:57-72. [PMID: 29067656 DOI: 10.1007/978-1-4939-7374-3_5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Duchenne muscular dystrophy (DMD), caused by the absence of the protein dystrophin, is characterized as a neuromuscular disease in which muscle weakness, increased susceptibility to muscle injury, and inadequate repair appear to underlie the pathology. Considerable attention has been dedicated to studying muscle fiber damage, but there is little information to determine if damage from contraction-induced injury also occurs at or near the nerve terminal axon. Interestingly, both human patients and the mouse model for DMD (the mdx mouse) present fragmented neuromuscular junction (NMJ) morphology. Studies of mdx mice have revealed presynaptic and postsynaptic abnormalities, nerve terminal discontinuity, as well as increased susceptibility of the NMJ to contraction-induced injury with corresponding functional changes in neuromuscular transmission and nerve-evoked electromyography. Focusing on the NMJ as a contributor to functional deficits in the muscle represents a paradigm shift from the more prevalent myocentric perspectives. Further studies are needed to determine the extent to which the nerve-muscle interaction is disrupted in DMD and the role of the NMJ in the dystrophic progression. This chapter lists the tools needed for nerve terminal and NMJ structural analysis using fluorescence imaging, and provides a step-by-step outline for how to stain, image, and analyze the NMJ in skeletal muscle, with specific attention to mdx muscle.
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Affiliation(s)
- Stephen J P Pratt
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore School of Medicine, Baltimore, MD, USA
| | - Shama R Iyer
- Department of Orthopaedics, University of Maryland, Baltimore School of Medicine, 100 Penn St., AHB, Room 540, Baltimore, MD, 21201, USA
| | - Sameer B Shah
- Departments of Orthopaedic Surgery and Bioengineering, University of California San Diego, La Jolla, CA, 92093, USA
- Research Division, Veterans Administration San Diego Healthcare System, San Diego, CA, 92121, USA
| | - Richard M Lovering
- Department of Orthopaedics, University of Maryland, Baltimore School of Medicine, 100 Penn St., AHB, Room 540, Baltimore, MD, 21201, USA.
- Department of Physiology, University of Maryland, Baltimore School of Medicine, Baltimore, MD, USA.
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Mavrogeni S, Pons R, Nikas I, Papadopoulos G, Verganelakis DA, Kolovou G, Chrousos GP. Brain and heart magnetic resonance imaging/spectroscopy in duchenne muscular dystrophy. Eur J Clin Invest 2017; 47. [PMID: 28981141 DOI: 10.1111/eci.12842] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2017] [Accepted: 10/02/2017] [Indexed: 01/04/2023]
Abstract
Duchenne muscular dystrophy (DMD) is an X-linked muscle disorder characterized by progressive and irreversible loss of muscular function. As muscular disease progresses, the repair mechanisms cannot compensate for cellular damage, leading inevitably to necrosis and progressive replacement by fibrous and fatty tissue. Cardiomyopathy and respiratory failure are the main causes of death in DMD. In addition to the well-described muscle and heart disease, cognitive dysfunction affects around 30% of DMD boys. Myocardial fibrosis, assessed by late gadolinium enhancement (LGE), using cardiovascular magnetic resonance imaging (CMR), is an early marker of heart involvement in both DMD patients and female carriers. In parallel, brain MRI identifies smaller total brain volume, smaller grey matter volume, lower white matter fractional anisotropy and higher white matter radial diffusivity in DMD patients. The in vivo brain evaluation of mdx mice, a surrogate animal model of DMD, showed an increased inorganic phosphate (P(i))/phosphocreatine (PCr) and pH. In this paper, we propose a holistic approach using techniques of magnetic resonance imaging, spectroscopy and diffusion tensor imaging as a tool to create a "heart and brain imaging map" in DMD patients that could potentially facilitate the patients' risk stratification and also future research studies in the field.
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Affiliation(s)
| | - Roser Pons
- 1st Department of Pediatrics, National and Kapodistrian University of Athens, Aghia Sophia Children's Hospital, Athens, Greece
| | - Ioannis Nikas
- 1st Department of Pediatrics, National and Kapodistrian University of Athens, Aghia Sophia Children's Hospital, Athens, Greece
| | - George Papadopoulos
- 1st Department of Pediatrics, National and Kapodistrian University of Athens, Aghia Sophia Children's Hospital, Athens, Greece
| | - Dimitrios A Verganelakis
- 1st Department of Pediatrics, National and Kapodistrian University of Athens, Aghia Sophia Children's Hospital, Athens, Greece
| | | | - George P Chrousos
- 1st Department of Pediatrics, National and Kapodistrian University of Athens, Aghia Sophia Children's Hospital, Athens, Greece
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Peter AK, Miller G, Capote J, DiFranco M, Solares-Pérez A, Wang EL, Heighway J, Coral-Vázquez RM, Vergara J, Crosbie-Watson RH. Nanospan, an alternatively spliced isoform of sarcospan, localizes to the sarcoplasmic reticulum in skeletal muscle and is absent in limb girdle muscular dystrophy 2F. Skelet Muscle 2017; 7:11. [PMID: 28587652 PMCID: PMC5461684 DOI: 10.1186/s13395-017-0127-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 05/12/2017] [Indexed: 12/26/2022] Open
Abstract
Background Sarcospan (SSPN) is a transmembrane protein that interacts with the sarcoglycans (SGs) to form a tight subcomplex within the dystrophin-glycoprotein complex that spans the sarcolemma and interacts with laminin in the extracellular matrix. Overexpression of SSPN ameliorates Duchenne muscular dystrophy in murine models. Methods Standard cloning approaches were used to identify nanospan, and nanospan-specific polyclonal antibodies were generated and validated. Biochemical isolation of skeletal muscle membranes and two-photon laser scanning microscopy were used to analyze nanospan localization in muscle from multiple murine models. Duchenne muscular dystrophy biopsies were analyzed by immunoblot analysis of protein lysates as well as indirect immunofluorescence analysis of muscle cryosections. Results Nanospan is an alternatively spliced isoform of sarcospan. While SSPN has four transmembrane domains and is a core component of the sarcolemmal dystrophin-glycoprotein complex, nanospan is a type II transmembrane protein that does not associate with the dystrophin-glycoprotein complex. We demonstrate that nanospan is enriched in the sarcoplasmic reticulum (SR) fractions and is not present in the T-tubules. SR fractions contain membranes from three distinct structural regions: a region flanking the T-tubules (triadic SR), a SR region across the Z-line (ZSR), and a longitudinal SR region across the M-line (LSR). Analysis of isolated murine muscles reveals that nanospan is mostly associated with the ZSR and triadic SR, and only minimally with the LSR. Furthermore, nanospan is absent from the SR of δ-SG-null (Sgcd−/−) skeletal muscle, a murine model for limb girdle muscular dystrophy 2F. Analysis of skeletal muscle biopsies from Duchenne muscular dystrophy patients reveals that nanospan is preferentially expressed in type I (slow) fibers in both control and Duchenne samples. Furthermore, nanospan is significantly reduced in Duchenne biopsies. Conclusions Alternative splicing of proteins from the SG-SSPN complex produces δ-SG3, microspan, and nanospan that localize to the ZSR and the triadic SR, where they may play a role in regulating resting calcium levels as supported by previous studies (Estrada et al., Biochem Biophys Res Commun 340:865–71, 2006). Thus, alternative splicing of SSPN mRNA generates three protein isoforms (SSPN, microspan, and nanospan) that differ in the number of transmembrane domains affecting subcellular membrane association into distinct protein complexes. Electronic supplementary material The online version of this article (doi:10.1186/s13395-017-0127-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Angela K Peter
- Department of Integrative Biology and Physiology, University of California, Los Angeles, 610 Charles E. Young Drive East, Terasaki Life Sciences Building, Los Angeles, CA, 90095, USA.,Present Address: Biofrontiers Institute, Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO, USA
| | - Gaynor Miller
- Department of Integrative Biology and Physiology, University of California, Los Angeles, 610 Charles E. Young Drive East, Terasaki Life Sciences Building, Los Angeles, CA, 90095, USA.,Present Address: Department of Oncology and Metabolism, University of Sheffield, Sheffield, UK
| | - Joana Capote
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, 610 Charles E. Young Drive East, Terasaki Life Sciences Building, Los Angeles, CA, 90095, USA.,Center for Duchenne Muscular Dystrophy, University of California, Los Angeles, Los Angeles, CA, USA
| | - Marino DiFranco
- Center for Duchenne Muscular Dystrophy, University of California, Los Angeles, Los Angeles, CA, USA.,Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Alhondra Solares-Pérez
- Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Mexico City, Mexico
| | - Emily L Wang
- Department of Integrative Biology and Physiology, University of California, Los Angeles, 610 Charles E. Young Drive East, Terasaki Life Sciences Building, Los Angeles, CA, 90095, USA
| | - Jim Heighway
- Cancer Communications and Consultancy Ltd, Knutsford, Cheshire, UK
| | - Ramón M Coral-Vázquez
- Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Mexico City, Mexico
| | - Julio Vergara
- Center for Duchenne Muscular Dystrophy, University of California, Los Angeles, Los Angeles, CA, USA.,Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Rachelle H Crosbie-Watson
- Department of Integrative Biology and Physiology, University of California, Los Angeles, 610 Charles E. Young Drive East, Terasaki Life Sciences Building, Los Angeles, CA, 90095, USA. .,Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, 610 Charles E. Young Drive East, Terasaki Life Sciences Building, Los Angeles, CA, 90095, USA. .,Center for Duchenne Muscular Dystrophy, University of California, Los Angeles, Los Angeles, CA, USA. .,Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA, USA.
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28
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Manning J, Buckley MM, O'Halloran KD, O'Malley D. Combined XIL-6R and urocortin-2 treatment restores MDX diaphragm muscle force. Muscle Nerve 2017; 56:E134-E140. [PMID: 28294390 DOI: 10.1002/mus.25644] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 02/23/2017] [Accepted: 03/07/2017] [Indexed: 12/22/2022]
Abstract
INTRODUCTION Duchenne muscular dystrophy (DMD) is characterized by progressive muscle degeneration leading to immobility, respiratory failure, and premature death. As chronic inflammation and stress are implicated in DMD pathology, the efficacy of an anti-inflammatory and anti-stress intervention strategy in ameliorating diaphragm dysfunction was investigated. METHODS Diaphragm muscle contractile function was compared in wild-type and dystrophin-deficient mdx mice treated with saline, anti-interleukin-6 receptor antibodies (xIL-6R), the corticotrophin-releasing factor receptor 2 (CRFR2) agonist, urocortin 2, or both xIL-6R and urocortin 2. RESULTS Combined treatment with xIL-6R and urocortin 2 rescued impaired force in mdx diaphragms. Mechanical work production and muscle shortening was also improved by combined drug treatment. DISCUSSION Treatment which neutralizes peripheral IL-6 signaling and stimulates CRFR2 recovers force-generating capacity and the ability to perform mechanical work in mdx diaphragm muscle. These findings may be important in the search for therapeutic targets in DMD. Muscle Nerve 56: E134-E140, 2017.
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Affiliation(s)
- Jennifer Manning
- Department of Physiology, Western Gateway Building, University College Cork, Cork, Ireland
| | - Maria M Buckley
- Department of Physiology, Western Gateway Building, University College Cork, Cork, Ireland
| | - Ken D O'Halloran
- Department of Physiology, Western Gateway Building, University College Cork, Cork, Ireland
| | - Dervla O'Malley
- Department of Physiology, Western Gateway Building, University College Cork, Cork, Ireland
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29
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Iyer SR, Shah SB, Valencia AP, Schneider MF, Hernández-Ochoa EO, Stains JP, Blemker SS, Lovering RM. Altered nuclear dynamics in MDX myofibers. J Appl Physiol (1985) 2016; 122:470-481. [PMID: 27979987 DOI: 10.1152/japplphysiol.00857.2016] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Revised: 12/02/2016] [Accepted: 12/06/2016] [Indexed: 01/17/2023] Open
Abstract
Duchenne muscular dystrophy (DMD) is a genetic disorder in which the absence of dystrophin leads to progressive muscle degeneration and weakness. Although the genetic basis is known, the pathophysiology of dystrophic skeletal muscle remains unclear. We examined nuclear movement in wild-type (WT) and muscular dystrophy mouse model for DMD (MDX) (dystrophin-null) mouse myofibers. We also examined expression of proteins in the linkers of nucleoskeleton and cytoskeleton (LINC) complex, as well as nuclear transcriptional activity via histone H3 acetylation and polyadenylate-binding nuclear protein-1. Because movement of nuclei is not only LINC dependent but also microtubule dependent, we analyzed microtubule density and organization in WT and MDX myofibers, including the application of a unique 3D tool to assess microtubule core structure. Nuclei in MDX myofibers were more mobile than in WT myofibers for both distance traveled and velocity. MDX muscle shows reduced expression and labeling intensity of nesprin-1, a LINC protein that attaches the nucleus to the microtubule and actin cytoskeleton. MDX nuclei also showed altered transcriptional activity. Previous studies established that microtubule structure at the cortex is disrupted in MDX myofibers; our analyses extend these findings by showing that microtubule structure in the core is also disrupted. In addition, we studied malformed MDX myofibers to better understand the role of altered myofiber morphology vs. microtubule architecture in the underlying susceptibility to injury seen in dystrophic muscles. We incorporated morphological and microtubule architectural concepts into a simplified finite element mathematical model of myofiber mechanics, which suggests a greater contribution of myofiber morphology than microtubule structure to muscle biomechanical performance.NEW & NOTEWORTHY Microtubules provide the means for nuclear movement but show altered organization in the muscular dystrophy mouse model (MDX) (dystrophin-null) muscle. Here, MDX myofibers show increased nuclear movement, altered transcriptional activity, and altered linkers of nucleoskeleton and cytoskeleton complex expression compared with healthy myofibers. Microtubule architecture was incorporated in finite element modeling of passive stretch, revealing a role of fiber malformation, commonly found in MDX muscle. The results suggest that alterations in microtubule architecture in MDX muscle affect nuclear movement, which is essential for muscle function.
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Affiliation(s)
- Shama R Iyer
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland
| | - Sameer B Shah
- Departments of Orthopaedic Surgery and Bioengineering, University of California San Diego, La Jolla, California
| | - Ana P Valencia
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland
| | - Martin F Schneider
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Erick O Hernández-Ochoa
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Joseph P Stains
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland
| | - Silvia S Blemker
- Department of Biomedical Engineering and Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia; and
| | - Richard M Lovering
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland; .,Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
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30
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Allen DG, Whitehead NP, Froehner SC. Absence of Dystrophin Disrupts Skeletal Muscle Signaling: Roles of Ca2+, Reactive Oxygen Species, and Nitric Oxide in the Development of Muscular Dystrophy. Physiol Rev 2016; 96:253-305. [PMID: 26676145 DOI: 10.1152/physrev.00007.2015] [Citation(s) in RCA: 272] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Dystrophin is a long rod-shaped protein that connects the subsarcolemmal cytoskeleton to a complex of proteins in the surface membrane (dystrophin protein complex, DPC), with further connections via laminin to other extracellular matrix proteins. Initially considered a structural complex that protected the sarcolemma from mechanical damage, the DPC is now known to serve as a scaffold for numerous signaling proteins. Absence or reduced expression of dystrophin or many of the DPC components cause the muscular dystrophies, a group of inherited diseases in which repeated bouts of muscle damage lead to atrophy and fibrosis, and eventually muscle degeneration. The normal function of dystrophin is poorly defined. In its absence a complex series of changes occur with multiple muscle proteins showing reduced or increased expression or being modified in various ways. In this review, we will consider the various proteins whose expression and function is changed in muscular dystrophies, focusing on Ca(2+)-permeable channels, nitric oxide synthase, NADPH oxidase, and caveolins. Excessive Ca(2+) entry, increased membrane permeability, disordered caveolar function, and increased levels of reactive oxygen species are early changes in the disease, and the hypotheses for these phenomena will be critically considered. The aim of the review is to define the early damage pathways in muscular dystrophy which might be appropriate targets for therapy designed to minimize the muscle degeneration and slow the progression of the disease.
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Affiliation(s)
- David G Allen
- Sydney Medical School & Bosch Institute, University of Sydney, New South Wales, Australia; and Department of Physiology & Biophysics, University of Washington, Seattle, Washington
| | - Nicholas P Whitehead
- Sydney Medical School & Bosch Institute, University of Sydney, New South Wales, Australia; and Department of Physiology & Biophysics, University of Washington, Seattle, Washington
| | - Stanley C Froehner
- Sydney Medical School & Bosch Institute, University of Sydney, New South Wales, Australia; and Department of Physiology & Biophysics, University of Washington, Seattle, Washington
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Hernández-Ochoa EO, Vanegas C, Iyer SR, Lovering RM, Schneider MF. Alternating bipolar field stimulation identifies muscle fibers with defective excitability but maintained local Ca(2+) signals and contraction. Skelet Muscle 2016; 6:6. [PMID: 26855765 PMCID: PMC4743112 DOI: 10.1186/s13395-016-0076-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 01/05/2016] [Indexed: 11/25/2022] Open
Abstract
Background Most cultured enzymatically dissociated adult myofibers exhibit spatially uniform (UNI) contractile responses and Ca2+ transients over the entire myofiber in response to electric field stimuli of either polarity applied via bipolar electrodes. However, some myofibers only exhibit contraction and Ca2+ transients at alternating (ALT) ends in response to alternating polarity field stimulation. Here, we present for the first time the methodology for identification of ALT myofibers in primary cultures and isolated muscles, as well as a study of their electrophysiological properties. Results We used high-speed confocal microscopic Ca2+ imaging, electric field stimulation, microelectrode recordings, immunostaining, and confocal microscopy to characterize the properties of action potential-induced Ca2+ transients, contractility, resting membrane potential, and staining of T-tubule voltage-gated Na+ channel distribution applied to cultured adult myofibers. Here, we show for the first time, with high temporal and spatial resolution, that normal control myofibers with UNI responses can be converted to ALT response myofibers by TTX addition or by removal of Na+ from the bathing medium, with reappearance of the UNI response on return of Na+. Our results suggest disrupted excitability as the cause of ALT behavior and indicate that the ALT response is due to local depolarization-induced Ca2+ release, whereas the UNI response is triggered by action potential propagation over the entire myofiber. Consistent with this interpretation, local depolarizing monopolar stimuli give uniform (propagated) responses in UNI myofibers, but only local responses at the electrode in ALT myofibers. The ALT responses in electrically inexcitable myofibers are consistent with expectations of current spread between bipolar stimulating electrodes, entering (hyperpolarizing) one end of a myofiber and leaving (depolarizing) the other end of the myofiber. ALT responses were also detected in some myofibers within intact isolated whole muscles from wild-type and MDX mice, demonstrating that ALT responses can be present before enzymatic dissociation. Conclusions We suggest that checking for ALT myofiber responsiveness by looking at the end of a myofiber during alternating polarity stimuli provides a test for compromised excitability of myofibers, and could be used to identify inexcitable, damaged or diseased myofibers by ALT behavior in healthy and diseased muscle. Electronic supplementary material The online version of this article (doi:10.1186/s13395-016-0076-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Erick O Hernández-Ochoa
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, 108 N. Greene Street, Baltimore, MD 21201 USA
| | - Camilo Vanegas
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, 108 N. Greene Street, Baltimore, MD 21201 USA
| | - Shama R Iyer
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD 21201 USA
| | - Richard M Lovering
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD 21201 USA
| | - Martin F Schneider
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, 108 N. Greene Street, Baltimore, MD 21201 USA
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Pichavant C, Burkholder TJ, Pavlath GK. Decrease of myofiber branching via muscle-specific expression of the olfactory receptor mOR23 in dystrophic muscle leads to protection against mechanical stress. Skelet Muscle 2016; 6:2. [PMID: 26798450 PMCID: PMC4721043 DOI: 10.1186/s13395-016-0077-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 01/05/2016] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Abnormal branched myofibers within skeletal muscles are commonly found in diverse animal models of muscular dystrophy as well as in patients. Branched myofibers from dystrophic mice are more susceptible to break than unbranched myofibers suggesting that muscles containing a high percentage of these myofibers are more prone to injury. Previous studies showed ubiquitous over-expression of mouse olfactory receptor 23 (mOR23), a G protein-coupled receptor, in wild type mice decreased myofiber branching. Whether mOR23 over-expression specifically in skeletal muscle cells is sufficient to mitigate myofiber branching in dystrophic muscle is unknown. METHODS We created a novel transgenic mouse over-expressing mOR23 specifically in muscle cells and then bred with dystrophic (mdx) mice. Myofiber branching was analyzed in these two transgenic mice and membrane integrity was assessed by Evans blue dye fluorescence. RESULTS mOR23 over-expression in muscle led to a decrease of myofiber branching after muscle regeneration in non-dystrophic mouse muscles and reduced the severity of myofiber branching in mdx mouse muscles. Muscles from mdx mouse over-expressing mOR23 significantly exhibited less damage to eccentric contractions than control mdx muscles. CONCLUSIONS The decrease of myofiber branching in mdx mouse muscles over-expressing mOR23 reduced the amount of membrane damage induced by mechanical stress. These results suggest that modifying myofiber branching in dystrophic patients, while not preventing degeneration, could be beneficial for mitigating some of the effects of the disease process.
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Affiliation(s)
- Christophe Pichavant
- Department of Pharmacology, Emory University, Atlanta, GA USA ; Present address: Department of Genetics, Stanford University, Stanford, CA USA
| | - Thomas J Burkholder
- School of Applied Physiology, Georgia Institute of Technology, Atlanta, GA USA
| | - Grace K Pavlath
- Department of Pharmacology, Emory University, Atlanta, GA USA ; 1510 Clifton Road, Room 5024, Atlanta, GA 30322 USA
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Hernández-Ochoa EO, Pratt SJP, Lovering RM, Schneider MF. Critical Role of Intracellular RyR1 Calcium Release Channels in Skeletal Muscle Function and Disease. Front Physiol 2016; 6:420. [PMID: 26793121 PMCID: PMC4709859 DOI: 10.3389/fphys.2015.00420] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 12/21/2015] [Indexed: 01/25/2023] Open
Abstract
The skeletal muscle Ca2+ release channel, also known as ryanodine receptor type 1 (RyR1), is the largest ion channel protein known and is crucial for effective skeletal muscle contractile activation. RyR1 function is controlled by Cav1.1, a voltage gated Ca2+ channel that works mainly as a voltage sensor for RyR1 activity during skeletal muscle contraction and is also fine-tuned by Ca2+, several intracellular compounds (e.g., ATP), and modulatory proteins (e.g., calmodulin). Dominant and recessive mutations in RyR1, as well as acquired channel alterations, are the underlying cause of various skeletal muscle diseases. The aim of this mini review is to summarize several current aspects of RyR1 function, structure, regulation, and to describe the most common diseases caused by hereditary or acquired RyR1 malfunction.
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Affiliation(s)
- Erick O Hernández-Ochoa
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine Baltimore, MD, USA
| | - Stephen J P Pratt
- Department of Orthopaedics, University of Maryland School of Medicine Baltimore, MD, USA
| | - Richard M Lovering
- Department of Orthopaedics, University of Maryland School of Medicine Baltimore, MD, USA
| | - Martin F Schneider
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine Baltimore, MD, USA
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Pratt SJP, Valencia AP, Le GK, Shah SB, Lovering RM. Pre- and postsynaptic changes in the neuromuscular junction in dystrophic mice. Front Physiol 2015; 6:252. [PMID: 26441672 PMCID: PMC4563167 DOI: 10.3389/fphys.2015.00252] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 08/28/2015] [Indexed: 01/05/2023] Open
Abstract
Duchenne muscular dystrophy (DMD) is a devastating neuromuscular disease in which weakness, increased susceptibility to muscle injury, and inadequate repair appear to underlie the pathology. While most attention has focused within the muscle fiber, we recently demonstrated in mdx mice (murine model for DMD) significant morphologic alterations at the motor endplate of the neuromuscular junction (NMJ) and corresponding NMJ transmission failure after injury. Here we extend these initial observations at the motor endplate to gain insight into the pre- vs. postsynaptic morphology, as well as the subsynaptic nuclei in healthy (WT) vs. mdx mice. We quantified the discontinuity and branching of the terminal nerve in adult mice. We report mdx- and age-dependent changes for discontinuity and an increase in branching when compared to WT. To examine mdx- and age-dependent changes in the relative localization of pre- and postsynaptic structures, we calculated NMJ occupancy, defined as the ratio of the footprint occupied by presynaptic vesicles vs. that of the underlying motor endplate. The normally congruent coupling between presynaptic and postsynaptic morphology was altered in mdx mice, independent of age. Finally we found an almost two-fold increase in the number of nuclei and an increase in density (nuclei/area) underlying the NMJ. These outcomes suggest substantial remodeling of the NMJ during dystrophic progression. This remodeling reflects plasticity in both pre- and postsynaptic contributors to NMJ structure, and thus perhaps also NM transmission and muscle function.
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Affiliation(s)
- Stephen J P Pratt
- Department of Orthopaedics, University of Maryland School of Medicine Baltimore, MD, USA
| | - Ana P Valencia
- Department of Orthopaedics, University of Maryland School of Medicine Baltimore, MD, USA ; Department of Kinesiology, University of Maryland School of Public Health College Park, MD, USA
| | - Gloribel K Le
- Department of Orthopaedics, University of Maryland School of Medicine Baltimore, MD, USA
| | - Sameer B Shah
- Departments of Orthopaedic Surgery and Bioengineering, University of California San Diego, La Jolla, CA, USA
| | - Richard M Lovering
- Department of Orthopaedics, University of Maryland School of Medicine Baltimore, MD, USA
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Hollinger K, Selsby JT. PGC-1αgene transfer improves muscle function in dystrophic muscle following prolonged disease progress. Exp Physiol 2015; 100:1145-58. [DOI: 10.1113/ep085339] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 07/31/2015] [Indexed: 12/14/2022]
Affiliation(s)
- Katrin Hollinger
- Department of Animal Science; Iowa State University; Ames IA 50011 USA
| | - Joshua T. Selsby
- Department of Animal Science; Iowa State University; Ames IA 50011 USA
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Xu S, Shi D, Pratt SJP, Zhu W, Marshall A, Lovering RM. Abnormalities in brain structure and biochemistry associated with mdx mice measured by in vivo MRI and high resolution localized (1)H MRS. Neuromuscul Disord 2015; 25:764-72. [PMID: 26236031 DOI: 10.1016/j.nmd.2015.07.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 06/21/2015] [Accepted: 07/06/2015] [Indexed: 01/16/2023]
Abstract
Duchenne muscular dystrophy (DMD), an X-linked disorder caused by the lack of dystrophin, is characterized by the progressive wasting of skeletal muscles. To date, what is known about dystrophin function is derived from studies of dystrophin-deficient animals, with the most common model being the mdx mouse. Most studies on patients with DMD and in mdx mice have focused on skeletal muscle and the development of therapies to reverse, or at least slow, the severe muscle wasting and progressive degeneration. However, dystrophin is also expressed in the CNS. Both mdx mice and patients with DMD can have cognitive and behavioral changes, but studies in the dystrophic brain are limited. We examined the brain structure and metabolites of mature wild type (WT) and mdx mice using magnetic resonance imaging and spectroscopy (MRI/MRS). Both structural and metabolic alterations were observed in the mdx brain. Enlarged lateral ventricles were detected in mdx mice when compared to WT. Diffusion tensor imaging (DTI) revealed elevations in diffusion diffusivities in the prefrontal cortex and a reduction of fractional anisotropy in the hippocampus. Metabolic changes included elevations in phosphocholine and glutathione, and a reduction in γ-aminobutyric acid in the hippocampus. In addition, an elevation in taurine was observed in the prefrontal cortex. Such findings indicate a regional structural change, altered cellular antioxidant defenses, a dysfunction of GABAergic neurotransmission, and a perturbed osmoregulation in the brain lacking dystrophin.
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Affiliation(s)
- Su Xu
- Department of Diagnostic Radiology and Nuclear Medicine, School of Medicine, University of Maryland, Baltimore, MD, USA
| | - Da Shi
- Department of Diagnostic Radiology and Nuclear Medicine, School of Medicine, University of Maryland, Baltimore, MD, USA
| | - Stephen J P Pratt
- Department of Orthopaedics, School of Medicine, University of Maryland, Baltimore, MD, USA
| | - Wenjun Zhu
- Department of Diagnostic Radiology and Nuclear Medicine, School of Medicine, University of Maryland, Baltimore, MD, USA
| | - Andrew Marshall
- Department of Diagnostic Radiology and Nuclear Medicine, School of Medicine, University of Maryland, Baltimore, MD, USA
| | - Richard M Lovering
- Department of Orthopaedics, School of Medicine, University of Maryland, Baltimore, MD, USA.
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Blat Y, Blat S. Drug Discovery of Therapies for Duchenne Muscular Dystrophy. ACTA ACUST UNITED AC 2015; 20:1189-203. [PMID: 25975656 DOI: 10.1177/1087057115586535] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 04/21/2015] [Indexed: 01/16/2023]
Abstract
Duchenne muscular dystrophy (DMD) is a genetic, lethal, muscle disorder caused by the loss of the muscle protein, dystrophin, leading to progressive loss of muscle fibers and muscle weakness. Drug discovery efforts targeting DMD have used two main approaches: (1) the restoration of dystrophin expression or the expression of a compensatory protein, and (2) the mitigation of downstream pathological mechanisms, including dysregulated calcium homeostasis, oxidative stress, inflammation, fibrosis, and muscle ischemia. The aim of this review is to introduce the disease, its pathophysiology, and the available research tools to a drug discovery audience. This review will also detail the most promising therapies that are currently being tested in clinical trials or in advanced preclinical models.
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Affiliation(s)
| | - Shachar Blat
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA
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Hernández-Ochoa EO, Pratt SJP, Garcia-Pelagio KP, Schneider MF, Lovering RM. Disruption of action potential and calcium signaling properties in malformed myofibers from dystrophin-deficient mice. Physiol Rep 2015; 3:3/4/e12366. [PMID: 25907787 PMCID: PMC4425971 DOI: 10.14814/phy2.12366] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Duchenne muscular dystrophy (DMD), the most common and severe muscular dystrophy, is caused by the absence of dystrophin. Muscle weakness and fragility (i.e., increased susceptibility to damage) are presumably due to structural instability of the myofiber cytoskeleton, but recent studies suggest that the increased presence of malformed/branched myofibers in dystrophic muscle may also play a role. We have previously studied myofiber morphology in healthy wild-type (WT) and dystrophic (MDX) skeletal muscle. Here, we examined myofiber excitability using high-speed confocal microscopy and the voltage-sensitive indicator di-8-butyl-amino-naphthyl-ethylene-pyridinium-propyl-sulfonate (di-8-ANEPPS) to assess the action potential (AP) properties. We also examined AP-induced Ca2+ transients using high-speed confocal microscopy with rhod-2, and assessed sarcolemma fragility using elastimetry. AP recordings showed an increased width and time to peak in malformed MDX myofibers compared to normal myofibers from both WT and MDX, but no significant change in AP amplitude. Malformed MDX myofibers also exhibited reduced AP-induced Ca2+ transients, with a further Ca2+ transient reduction in the branches of malformed MDX myofibers. Mechanical studies indicated an increased sarcolemma deformability and instability in malformed MDX myofibers. The data suggest that malformed myofibers are functionally different from myofibers with normal morphology. The differences seen in AP properties and Ca2+ signals suggest changes in excitability and remodeling of the global Ca2+ signal, both of which could underlie reported weakness in dystrophic muscle. The biomechanical changes in the sarcolemma support the notion that malformed myofibers are more susceptible to damage. The high prevalence of malformed myofibers in dystrophic muscle may contribute to the progressive strength loss and fragility seen in dystrophic muscles.
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Affiliation(s)
- Erick O Hernández-Ochoa
- Department of Biochemistry & Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Stephen J P Pratt
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland
| | - Karla P Garcia-Pelagio
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Martin F Schneider
- Department of Biochemistry & Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Richard M Lovering
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryland
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Mázala DAG, Pratt SJP, Chen D, Molkentin JD, Lovering RM, Chin ER. SERCA1 overexpression minimizes skeletal muscle damage in dystrophic mouse models. Am J Physiol Cell Physiol 2015; 308:C699-709. [PMID: 25652448 DOI: 10.1152/ajpcell.00341.2014] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 02/01/2015] [Indexed: 02/04/2023]
Abstract
Duchenne muscular dystrophy (DMD) is characterized by progressive muscle wasting secondary to repeated muscle damage and inadequate repair. Elevations in intracellular free Ca²⁺ have been implicated in disease progression, and sarcoplasmic/endoplasmic reticulum Ca²⁺-ATPase 1 (SERCA1) overexpression has been shown to ameliorate the dystrophic phenotype in mdx mice. The purpose of this study was to assess the effects of SERCA1 overexpression in the more severe mdx/Utr(-/-) mouse model of DMD. Mice overexpressing SERCA1 were crossed with mdx/Utr ± mice to generate mdx/Utr(-/-)/+SERCA1 mice and compared with wild-type (WT), WT/+SERCA1, mdx/+SERCA1, and genotype controls. Mice were assessed at ∼12 wk of age for changes in Ca²⁺ handling, muscle mass, quadriceps torque, markers of muscle damage, and response to repeated eccentric contractions. SERCA1-overexpressing mice had a two- to threefold increase in maximal sarcoplasmic reticulum Ca²⁺-ATPase activity compared with WT which was associated with normalization in body mass for both mdx/+SERCA1 and mdx/Utr(-/-)/+SERCA1. Torque deficit in the quadriceps after eccentric injury was 2.7-fold greater in mdx/Utr(-/-) vs. WT mice, but only 1.5-fold greater in mdx/Utr(-/-)/+SERCA1 vs. WT mice, an attenuation of 44%. Markers of muscle damage (% centrally nucleated fibers, necrotic area, and serum creatine kinase levels) were higher in both mdx and mdx/Utr(-/-) vs. WT, and all were attenuated by overexpression of SERCA1. These data indicate that SERCA1 overexpression ameliorates functional impairments and cellular markers of damage in a more severe mouse model of DMD. These findings support targeting intracellular Ca²⁺ control as a therapeutic approach for DMD.
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Affiliation(s)
- Davi A G Mázala
- Department of Kinesiology, School of Public Health, University of Maryland, College Park, Maryand
| | - Stephen J P Pratt
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryand; and
| | - Dapeng Chen
- Department of Kinesiology, School of Public Health, University of Maryland, College Park, Maryand
| | - Jeffery D Molkentin
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Richard M Lovering
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryand; and
| | - Eva R Chin
- Department of Kinesiology, School of Public Health, University of Maryland, College Park, Maryand; Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, Maryand; and Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
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40
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Mázala DAG, Grange RW, Chin ER. The role of proteases in excitation-contraction coupling failure in muscular dystrophy. Am J Physiol Cell Physiol 2014; 308:C33-40. [PMID: 25298424 DOI: 10.1152/ajpcell.00267.2013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Duchenne muscular dystrophy (DMD) is one of the most frequent types of muscular dystrophy. Alterations in intracellular calcium (Ca(2+)) handling are thought to contribute to the disease severity in DMD, possibly due to the activation of Ca(2+)-activated proteases. The purpose of this study was twofold: 1) to determine whether prolonged excitation-contraction (E-C) coupling disruption following repeated contractions is greater in animals lacking both dystrophin and utrophin (mdx/Utr(-/-)) compared with mice lacking only dystrophin (mdx); and 2) to assess whether protease inhibition can prevent E-C coupling failure following repeated tetani in these dystrophic mouse models. Excitation-contraction coupling was assessed using Fura-2 ratio, as an index of intracellular free Ca(2+) concentration, in response to electrical stimulation of single muscle fibers from the flexor digitorum brevis muscle. Resting Fura-2 ratio was higher in dystrophic compared with control (Con) fibers, but peak Fura-2 ratios during stimulation were similar in dystrophic and Con fibers. One hour after a series of repeated tetani, peak Fura-2 ratios were reduced by 30 ± 5.6%, 23 ± 2%, and 36 ± 3.1% in mdx, mdx/Utr(+/-), and mdx/Utr(-/-), respectively, with the greatest reduction in mdx/Utr(-/-) fibers (P < 0.05). Protease inhibition attenuated this decrease in peak Fura-2 ratio. These data indicate that E-C coupling impairment after repeated contractions is greatest in fibers lacking both dystrophin and utrophin and that prevention of protease activation can mitigate the prolonged E-C coupling impairment. These data further suggest that acute protease inhibition may be useful in reducing muscle weakness in DMD.
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Affiliation(s)
- Davi A G Mázala
- Department of Kinesiology, School of Public Health, University of Maryland, College Park, Maryland; and
| | - Robert W Grange
- Department of Human Nutrition, Foods and Exercise, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - Eva R Chin
- Department of Kinesiology, School of Public Health, University of Maryland, College Park, Maryland; and
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Brinkmeier H, Ohlendieck K. Chaperoning heat shock proteins: Proteomic analysis and relevance for normal and dystrophin-deficient muscle. Proteomics Clin Appl 2014; 8:875-95. [DOI: 10.1002/prca.201400015] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Revised: 04/24/2014] [Accepted: 05/28/2014] [Indexed: 12/15/2022]
Affiliation(s)
| | - Kay Ohlendieck
- Department of Biology; National University of Ireland; Maynooth Co. Kildare Ireland
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42
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Pratt SJP, Shah SB, Ward CW, Kerr JP, Stains JP, Lovering RM. Recovery of altered neuromuscular junction morphology and muscle function in mdx mice after injury. Cell Mol Life Sci 2014; 72:153-64. [PMID: 24947322 PMCID: PMC4282693 DOI: 10.1007/s00018-014-1663-7] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Revised: 05/14/2014] [Accepted: 06/02/2014] [Indexed: 12/02/2022]
Abstract
Duchenne muscular dystrophy (DMD) is a devastating neuromuscular disease in which weakness, increased susceptibility to muscle injury, and inadequate repair underlie the pathology. While most attention has focused within the muscle fiber, we recently demonstrated significant alterations in the neuromuscular junction (NMJ) morphology and resulting neuromuscular transmission failure (NTF) 24 h after injury in mdx mice (murine model for DMD). Here we determine the contribution of NMJ morphology and NTF to the recovery of muscle contractile function post-injury. NMJ morphology and NTF rates were assessed day 0 (immediately after injury) and days 1, 7, 14 and 21 after quadriceps injury. Eccentric injury of the quadriceps resulted in a significant loss of maximal torque in both WT (39 ± 6 %) and mdx (76 ± 8 %) with a full recovery in WT by day 7 and in mdx by day 21. Post-injury alterations in NMJ morphology and NTF were found only in mdx, were limited to days 0 and 1, and were independent of changes in MuSK or AChR expression. Such early changes at the NMJ after injury are consistent with mechanical disruption rather than newly forming NMJs. Furthermore, we show that the dense microtubule network that underlies the NMJ is significantly reduced and disorganized in mdx compared to WT. These structural changes at the NMJ may play a role in the increased NMJ disruption and the exaggerated loss of nerve-evoked muscle force seen after injury to dystrophic muscles.
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Affiliation(s)
- Stephen J. P. Pratt
- Department of Orthopaedics, University of Maryland School of Medicine, 100 Penn St. AHB, Room 540, Baltimore, MD 21201 USA
| | - Sameer B. Shah
- Department of Orthopaedic Surgery and Bioengineering, University of California, San Diego, USA
| | | | - Jaclyn P. Kerr
- Department of Physiology, University of Maryland School of Medicine, Baltimore, USA
| | - Joseph P. Stains
- Department of Orthopaedics, University of Maryland School of Medicine, 100 Penn St. AHB, Room 540, Baltimore, MD 21201 USA
| | - Richard M. Lovering
- Department of Orthopaedics, University of Maryland School of Medicine, 100 Penn St. AHB, Room 540, Baltimore, MD 21201 USA
- Department of Physiology, University of Maryland School of Medicine, Baltimore, USA
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Faber RM, Hall JK, Chamberlain JS, Banks GB. Myofiber branching rather than myofiber hyperplasia contributes to muscle hypertrophy in mdx mice. Skelet Muscle 2014; 4:10. [PMID: 24910770 PMCID: PMC4047439 DOI: 10.1186/2044-5040-4-10] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2014] [Accepted: 05/06/2014] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Muscle hypertrophy in the mdx mouse model of Duchenne muscular dystrophy (DMD) can partially compensate for the loss of dystrophin by maintaining peak force production. Histopathology examination of the hypertrophic muscles suggests the hypertrophy primarily results from the addition of myofibers, and is accompanied by motor axon branching. However, it is unclear whether an increased number of innervated myofibers (myofiber hyperplasia) contribute to muscle hypertrophy in the mdx mice. METHODS To better understand the cellular mechanisms of muscle hypertrophy in mdx mice, we directly compared the temporal progression of the dystrophic pathology in the extensor digitorum longus (EDL) muscle to myofiber number, myofiber branching, and innervation, from 3 to 20 weeks of age. RESULTS We found that a 28% increase in the number of fibers in transverse sections of muscle correlated with a 31% increase in myofiber branching. Notably, the largest increases in myofiber number and myofiber branching occurred after 12 weeks of age when the proportion of myofibers with central nuclei had stabilized and the mdx mouse had reached maturity. The dystrophic pathology coincided with profound changes to innervation of the muscles that included temporary denervation of necrotic fibers, fragmentation of synapses, and ultra-terminal axon sprouting. However, there was little evidence of synapse formation in the mdx mice from 3 to 20 weeks of age. Only 4.4% of neuromuscular junctions extended ultra-terminal synapses, which failed to mature, and the total number of neuromuscular junctions remained constant. CONCLUSIONS Muscle hypertrophy in mdx mice results from myofiber branching rather than myofiber hyperplasia.
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Affiliation(s)
- Rachel M Faber
- Department of Neurology, University of Washington, Seattle, WA 98195-7720, USA
| | - John K Hall
- Department of Neurology, University of Washington, Seattle, WA 98195-7720, USA
| | - Jeffrey S Chamberlain
- Department of Neurology, University of Washington, Seattle, WA 98195-7720, USA ; Department of Biochemistry, University of Washington, Seattle, WA 98195-7720, USA ; Department of Medicine, University of Washington, Seattle, WA 98195-7720, USA
| | - Glen B Banks
- Department of Neurology, University of Washington, Seattle, WA 98195-7720, USA
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Pichavant C, Pavlath GK. Incidence and severity of myofiber branching with regeneration and aging. Skelet Muscle 2014; 4:9. [PMID: 24855558 PMCID: PMC4030050 DOI: 10.1186/2044-5040-4-9] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Accepted: 05/01/2014] [Indexed: 11/30/2022] Open
Abstract
Background Myofibers with an abnormal branching cytoarchitecture are commonly found in muscular dystrophy and in regenerated or aged nondystrophic muscles. Such branched myofibers from dystrophic mice are more susceptible to damage than unbranched myofibers in vitro, suggesting that muscles containing a high percentage of these myofibers are more prone to injury. Little is known about the regulation of myofiber branching. Methods To gain insights into the formation and fate of branched myofibers, we performed in-depth analyses of single myofibers isolated from dystrophic and nondystrophic (myotoxin-injured or aged) mouse muscles. The proportion of branched myofibers, the number of branches per myofiber and the morphology of the branches were assessed. Results Aged dystrophic mice exhibited the most severe myofiber branching as defined by the incidence of branched myofibers and the number of branches per myofiber, followed by myotoxin-injured, wild-type muscles and then aged wild-type muscles. In addition, the morphology of the branched myofibers differed among the various models. In response to either induced or ongoing muscle degeneration, branching was restricted to regenerated myofibers containing central nuclei. In myotoxin-injured muscles, the amount of branched myofibers remained stable over time. Conclusion We suggest that myofiber branching is a consequence of myofiber remodeling during muscle regeneration. Our present study lays valuable groundwork for identifying the molecular pathways leading to myofiber branching in dystrophy, trauma and aging. Decreasing myofiber branching in dystrophic patients may improve muscle resistance to mechanical stress.
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Affiliation(s)
- Christophe Pichavant
- Department of Pharmacology, Rollins Research Center, Emory University, 1510 Clifton Road, Atlanta, GA 30322, USA
| | - Grace K Pavlath
- Department of Pharmacology, Rollins Research Center, Emory University, 1510 Clifton Road, Atlanta, GA 30322, USA
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45
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Rouède D, Coumailleau P, Schaub E, Bellanger JJ, Blanchard-Desce M, Tiaho F. Myofibrillar misalignment correlated to triad disappearance of mdx mouse gastrocnemius muscle probed by SHG microscopy. BIOMEDICAL OPTICS EXPRESS 2014; 5:858-875. [PMID: 24688819 PMCID: PMC3959848 DOI: 10.1364/boe.5.000858] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 01/15/2014] [Accepted: 01/19/2014] [Indexed: 06/03/2023]
Abstract
We show that the canonical single frequency sarcomeric SHG intensity pattern (SHG-IP) of control muscles is converted to double frequency sarcomeric SHG-IP in preserved mdx mouse gastrocnemius muscles in the vicinity of necrotic fibers. These double frequency sarcomeric SHG-IPs are often spatially correlated to double frequency sarcomeric two-photon excitation fluorescence (TPEF) emitted from Z-line and I-bands and to one centered spot SHG angular intensity pattern (SHG-AIP) suggesting that these patterns are signature of myofibrillar misalignement. This latter is confirmed with transmission electron microscopy (TEM). Moreover, a good spatial correlation between SHG signature of myofibrillar misalignment and triad reduction is established. Theoretical simulation of sarcomeric SHG-IP is used to demonstrate the correlation between change of SHG-IP and -AIP and myofibrillar misalignment. The extreme sensitivity of SHG microscopy to reveal the submicrometric organization of A-band thick filaments is highlighted. This report is a first step toward future studies aimed at establishing live SHG signature of myofibrillar misalignment involving excitation contraction defects due to muscle damage and disease.
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Affiliation(s)
- Denis Rouède
- IPR, CNRS, UMR-CNRS UR1- 6251, Université de Rennes1, Campus de Beaulieu, Rennes, F-35000, France
| | - Pascal Coumailleau
- IRSET, INSERM, U1085, Université de Rennes1, Campus de Beaulieu, Rennes, F-35000, France
| | - Emmanuel Schaub
- IPR, CNRS, UMR-CNRS UR1- 6251, Université de Rennes1, Campus de Beaulieu, Rennes, F-35000, France
| | | | | | - François Tiaho
- IRSET, INSERM, U1085, Université de Rennes1, Campus de Beaulieu, Rennes, F-35000, France
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46
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Park KH, Weisleder N, Zhou J, Gumpper K, Zhou X, Duann P, Ma J, Lin PH. Assessment of calcium sparks in intact skeletal muscle fibers. J Vis Exp 2014:e50898. [PMID: 24638093 DOI: 10.3791/50898] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Maintaining homeostatic Ca(2+) signaling is a fundamental physiological process in living cells. Ca(2+) sparks are the elementary units of Ca(2+) signaling in the striated muscle fibers that appear as highly localized Ca(2+) release events mediated by ryanodine receptor (RyR) Ca(2+) release channels on the sarcoplasmic reticulum (SR) membrane. Proper assessment of muscle Ca(2+) sparks could provide information on the intracellular Ca(2+) handling properties of healthy and diseased striated muscles. Although Ca(2+) sparks events are commonly seen in resting cardiomyocytes, they are rarely observed in resting skeletal muscle fibers; thus there is a need for methods to generate and analyze sparks in skeletal muscle fibers. Detailed here is an experimental protocol for measuring Ca(2+) sparks in isolated flexor digitorm brevis (FDB) muscle fibers using fluorescent Ca(2+) indictors and laser scanning confocal microscopy. In this approach, isolated FDB fibers are exposed to transient hypoosmotic stress followed by a return to isotonic physiological solution. Under these conditions, a robust Ca(2+) sparks response is detected adjacent to the sarcolemmal membrane in young healthy FDB muscle fibers. Altered Ca(2+) sparks response is detected in dystrophic or aged skeletal muscle fibers. This approach has recently demonstrated that membrane-delimited signaling involving cross-talk between inositol (1,4,5)-triphosphate receptor (IP3R) and RyR contributes to Ca(2+) spark activation in skeletal muscle. In summary, our studies using osmotic stress induced Ca(2+) sparks showed that this intracellular response reflects a muscle signaling mechanism in physiology and aging/disease states, including mouse models of muscle dystrophy (mdx mice) or amyotrophic lateral sclerosis (ALS model).
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Affiliation(s)
- Ki Ho Park
- Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center
| | - Noah Weisleder
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center
| | - Jingsong Zhou
- Department of Molecular Biophysics and Physiology, Rush University Medical Center
| | - Kristyn Gumpper
- Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center
| | - Xinyu Zhou
- Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center
| | - Pu Duann
- Department of Internal Medicine, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center
| | - Jianjie Ma
- Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center
| | - Pei-Hui Lin
- Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center;
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47
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Zhang Y, King OD, Rahimov F, Jones TI, Ward CW, Kerr JP, Liu N, Emerson CP, Kunkel LM, Partridge TA, Wagner KR. Human skeletal muscle xenograft as a new preclinical model for muscle disorders. Hum Mol Genet 2014; 23:3180-8. [PMID: 24452336 DOI: 10.1093/hmg/ddu028] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Development of novel therapeutics requires good animal models of disease. Disorders for which good animal models do not exist have very few drugs in development or clinical trial. Even where there are accepted, albeit imperfect models, the leap from promising preclinical drug results to positive clinical trials commonly fails, including in disorders of skeletal muscle. The main alternative model for early drug development, tissue culture, lacks both the architecture and, usually, the metabolic fidelity of the normal tissue in vivo. Herein, we demonstrate the feasibility and validity of human to mouse xenografts as a preclinical model of myopathy. Human skeletal muscle biopsies transplanted into the anterior tibial compartment of the hindlimbs of NOD-Rag1(null) IL2rγ(null) immunodeficient host mice regenerate new vascularized and innervated myofibers from human myogenic precursor cells. The grafts exhibit contractile and calcium release behavior, characteristic of functional muscle tissue. The validity of the human graft as a model of facioscapulohumeral muscular dystrophy is demonstrated in disease biomarker studies, showing that gene expression profiles of xenografts mirror those of the fresh donor biopsies. These findings illustrate the value of a new experimental model of muscle disease, the human muscle xenograft in mice, as a feasible and valid preclinical tool to better investigate the pathogenesis of human genetic myopathies and to more accurately predict their response to novel therapeutics.
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Affiliation(s)
- Yuanfan Zhang
- The Hugo W. Moser Research Institute, Kennedy Krieger Institute, Baltimore, MD 21205, USA Graduate Program in Cellular and Molecular Medicine and
| | - Oliver D King
- Wellstone Program, Departments of Cell and Developmental Biology and Neurology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | | | - Takako I Jones
- Wellstone Program, Departments of Cell and Developmental Biology and Neurology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | | | - Jaclyn P Kerr
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA and
| | - Naili Liu
- The Hugo W. Moser Research Institute, Kennedy Krieger Institute, Baltimore, MD 21205, USA
| | - Charles P Emerson
- Wellstone Program, Departments of Cell and Developmental Biology and Neurology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | - Louis M Kunkel
- Program in Genomics, Division of Genetics, and The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Terence A Partridge
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC 20010, USA
| | - Kathryn R Wagner
- The Hugo W. Moser Research Institute, Kennedy Krieger Institute, Baltimore, MD 21205, USA Graduate Program in Cellular and Molecular Medicine and Departments of Neurology and Neuroscience, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
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48
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Head SI, Houweling PJ, Chan S, Chen G, Hardeman EC. Properties of regenerated mouse extensor digitorum longus muscle following notexin injury. Exp Physiol 2014; 99:664-74. [PMID: 24414176 DOI: 10.1113/expphysiol.2013.077289] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Muscles of mdx mice are known to be more susceptible to contraction-induced damage than wild-type muscle. However, it is not clear whether this is because of dystrophin deficiency or because of the abnormal branching morphology of dystrophic muscle fibres. This distinction has an important bearing on our traditional understanding of the function of dystrophin as a mechanical stabilizer of the sarcolemma. In this study, we address the question: 'Does dystrophin-positive, regenerated muscle containing branched fibres also show an increased susceptibility to contraction-induced damage?' We produced a model of fibre branching by injecting dystrophin-positive extensor digitorum longus muscles with notexin. The regenerated muscle was examined at 21 days postinjection. Notexin-injected muscle contained 29% branched fibres and was not more susceptible to damage from mild eccentric contractions than contralateral saline-injected control muscle. Regenerated muscles also had greater mass, greater cross-sectional area and lower specific force than control muscles. We conclude that the number of branched fibres in this regenerated muscle is below the threshold needed to increase susceptibility to damage. However, it would serve as an ideal control for muscles of young mdx mice, allowing for clearer differentiation of the effects of dystrophin deficiency from the effects of fibre regeneration and morphology.
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Affiliation(s)
- S I Head
- * Faculty of Medicine, The University of New South Wales, Sydney, NSW 2052, Australia.
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49
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Muir LA, Nguyen QG, Hauschka SD, Chamberlain JS. Engraftment potential of dermal fibroblasts following in vivo myogenic conversion in immunocompetent dystrophic skeletal muscle. MOLECULAR THERAPY-METHODS & CLINICAL DEVELOPMENT 2014; 1:14025. [PMID: 25558461 PMCID: PMC4280788 DOI: 10.1038/mtm.2014.25] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Autologous dermal fibroblasts (dFbs) are promising candidates for enhancing muscle regeneration in Duchenne muscular dystrophy (DMD) due to their ease of isolation, immunological compatibility, and greater proliferative potential than DMD satellite cells. We previously showed that mouse fibroblasts, after MyoD-mediated myogenic reprogramming in vivo, engraft in skeletal muscle and supply dystrophin. Assessing the therapeutic utility of this system requires optimization of conversion and transplantation conditions and quantitation of engraftment so that these parameters can be correlated with possible functional improvements. Here, we derived dFbs from transgenic mice carrying mini-dystrophin, transduced them by lentivirus carrying tamoxifen-inducible MyoD, and characterized their myogenic and engraftment potential. After cell transplantation into the muscles of immunocompetent dystrophic mdx4cv mice, tamoxifen treatment drove myogenic conversion and fusion into myofibers that expressed high levels of mini-dystrophin. Injecting 50,000 cells/µl (1 × 106 total cells) resulted in a peak of ~600 mini-dystrophin positive myofibers in tibialis anterior muscle single cross-sections. However, extensor digitorum longus muscles with up to 30% regional engraftment showed no functional improvements; similar limitations were obtained with whole muscle mononuclear cells. Despite the current lack of physiological improvement, this study suggests a viable initial strategy for using a patient-accessible dermal cell population to enhance skeletal muscle regeneration in DMD.
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Affiliation(s)
- Lindsey A Muir
- Program in Molecular and Cellular Biology, University of Washington ; Department of Neurology, University of Washington
| | | | | | - Jeffrey S Chamberlain
- Department of Neurology, University of Washington ; Department of Biochemistry, University of Washington ; Department of Medicine, University of Washington
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50
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Dysferlin stabilizes stress-induced Ca2+ signaling in the transverse tubule membrane. Proc Natl Acad Sci U S A 2013; 110:20831-6. [PMID: 24302765 DOI: 10.1073/pnas.1307960110] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Dysferlinopathies, most commonly limb girdle muscular dystrophy 2B and Miyoshi myopathy, are degenerative myopathies caused by mutations in the DYSF gene encoding the protein dysferlin. Studies of dysferlin have focused on its role in the repair of the sarcolemma of skeletal muscle, but dysferlin's association with calcium (Ca(2+)) signaling proteins in the transverse (t-) tubules suggests additional roles. Here, we reveal that dysferlin is enriched in the t-tubule membrane of mature skeletal muscle fibers. Following experimental membrane stress in vitro, dysferlin-deficient muscle fibers undergo extensive functional and structural disruption of the t-tubules that is ameliorated by reducing external [Ca(2+)] or blocking L-type Ca(2+) channels with diltiazem. Furthermore, we demonstrate that diltiazem treatment of dysferlin-deficient mice significantly reduces eccentric contraction-induced t-tubule damage, inflammation, and necrosis, which resulted in a concomitant increase in postinjury functional recovery. Our discovery of dysferlin as a t-tubule protein that stabilizes stress-induced Ca(2+) signaling offers a therapeutic avenue for limb girdle muscular dystrophy 2B and Miyoshi myopathy patients.
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