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Liu Y, Lin W. Morphological and functional alterations of neuromuscular synapses in a mouse model of ACTA1 congenital myopathy. Hum Mol Genet 2024; 33:233-244. [PMID: 37883471 PMCID: PMC10800017 DOI: 10.1093/hmg/ddad183] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 10/09/2023] [Accepted: 10/20/2023] [Indexed: 10/28/2023] Open
Abstract
Mutations in skeletal muscle α-actin (Acta1) cause myopathies. In a mouse model of congenital myopathy, heterozygous Acta1 (H40Y) knock-in (Acta1+/Ki) mice exhibit features of human nemaline myopathy, including premature lethality, severe muscle weakness, reduced mobility, and the presence of nemaline rods in muscle fibers. In this study, we investigated the impact of Acta1 (H40Y) mutation on the neuromuscular junction (NMJ). We found that the NMJs were markedly fragmented in Acta1+/Ki mice. Electrophysiological analysis revealed a decrease in amplitude but increase in frequency of miniature end-plate potential (mEPP) at the NMJs in Acta1+/Ki mice, compared with those in wild type (Acta1+/+) mice. Evoked end-plate potential (EPP) remained similar at the NMJs in Acta1+/Ki and Acta1+/+ mice, but quantal content was increased at the NMJs in Acta1+/Ki, compared with Acta1+/+ mice, suggesting a homeostatic compensation at the NMJs in Acta1+/Ki mice to maintain normal levels of neurotransmitter release. Furthermore, short-term synaptic plasticity of the NMJs was compromised in Acta1+/Ki mice. Together, these results demonstrate that skeletal Acta1 H40Y mutation, albeit muscle-origin, leads to both morphological and functional defects at the NMJ.
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Affiliation(s)
- Yun Liu
- Department of Neuroscience, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd, Dallas, TX 75390-9111, United States
| | - Weichun Lin
- Department of Neuroscience, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd, Dallas, TX 75390-9111, United States
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2
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Li L, Chen S, Yokoyama H, Kaburagi H, Hirai T, Tsuji K, Enomoto M, Wakabayashi Y, Okawa A. Remodeling of Neuromuscular Junctions in Target Muscle Following Nerve Regeneration in Mice After Delayed Peripheral Nerve Repair. Neuroscience 2023; 524:197-208. [PMID: 37201862 DOI: 10.1016/j.neuroscience.2023.05.008] [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: 07/31/2022] [Revised: 05/05/2023] [Accepted: 05/10/2023] [Indexed: 05/20/2023]
Abstract
Peripheral nerve injury (PNI) induces severe functional loss in extremities. Progressive denervation and atrophy occur in the muscles if the nerve repair is delayed for long periods of the time. To overcome these difficulties, detailed mechanisms should be determined for neuromuscular junction (NMJ) degeneration in target muscles after PNI and regeneration after nerve repair. We established two models of end-to-end neurorrhaphy and allogeneic nerve grafting in the chronic phase after common peroneal nerve injury in female mice (n = 100 in total). We evaluated motor function, histology, and gene expression in the target muscles during their regeneration processes and compared the models. We found that the functional recovery with allogeneic nerve grafting was superior to that with end-to-end neurorrhaphy, and the number of reinnervated NMJs and Schwann cells was increased at 12 weeks after allograft. In addition, NMJ- and Schwann cell-related molecules showed high expression in the target muscle in the allograft model. These results suggest that Schwann cell migrating from the allograft might play a crucial role in nerve regeneration in the chronic phase after PNI. The relationship between the NMJ and Schwann cells should be further investigated in the target muscle.
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Affiliation(s)
- Leyang Li
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo, Tokyo 113-8519, Japan; Department of Traumatic Orthopaedics, The Affiliated Yantai Yuhuangding Hospital of Qingdao University, Yantai, China.
| | - Su Chen
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo, Tokyo 113-8519, Japan.
| | - Hiroyuki Yokoyama
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo, Tokyo 113-8519, Japan.
| | - Hidetoshi Kaburagi
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo, Tokyo 113-8519, Japan.
| | - Takashi Hirai
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo, Tokyo 113-8519, Japan.
| | - Kunikazu Tsuji
- Department of Cartilage Regeneration, Tokyo Medical and Dental University, Tokyo, Japan.
| | - Mitsuhiro Enomoto
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo, Tokyo 113-8519, Japan.
| | - Yoshiaki Wakabayashi
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo, Tokyo 113-8519, Japan.
| | - Atsushi Okawa
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo, Tokyo 113-8519, Japan.
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3
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Hoffman DB, Basten AM, Sorensen JR, Raymond-Pope CJ, Lillquist TJ, Call JA, Corona BT, Greising SM. Response of terminal Schwann cells following volumetric muscle loss injury. Exp Neurol 2023; 365:114431. [PMID: 37142114 PMCID: PMC10227691 DOI: 10.1016/j.expneurol.2023.114431] [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: 01/16/2023] [Revised: 04/04/2023] [Accepted: 04/27/2023] [Indexed: 05/06/2023]
Abstract
An often-overlooked component of traumatic skeletal muscle injuries is the impact on the nervous system and resultant innervation of the affected muscles. Recent work in a rodent model of volumetric muscle loss (VML) injury demonstrated a progressive, secondary loss of neuromuscular junction (NMJ) innervation, supporting a role of NMJ dysregulation in chronic functional deficits. Terminal Schwann cells (tSCs) are known to be vital for the maintenance of NMJ structure and function, in addition to guiding repair and regeneration after injury. However, the tSC response to a traumatic muscle injury such as VML is not known. Thus, a study was conducted to investigate the effect of VML on tSC morphological characteristics and neurotrophic signaling proteins in adult male Lewis rats that underwent VML injury to the tibialis anterior muscle using a temporal design with outcome assessments at 3, 7, 14, 21, and 48 days post-injury. The following salient observations were made; first, although there is a loss of innervation over time, the number of tSCs per NMJ increases, significantly so at 48 days post-injury compared to control. The degree of NMJ fragmentation was positively correlated with tSC number after injury. Moreover, neurotrophic factors such as NRG1 and BDNF are elevated after injury through at least 48 days. These results were unanticipated and in contrast to neurodegenerative disease models, in which there is a reduction in tSC number that precedes denervation. However, we found that while there are more tSCs per NMJ after injury, they cover a significantly smaller percent of the post-synaptic endplate area compared to control. These findings support a sustained increase in neurotrophic activity and tSC number after VML, which is a maladaptive response occurring in parallel to other aspects of the VML injury, such as over-accumulation of collagen and aberrant inflammatory signaling.
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Affiliation(s)
- Daniel B Hoffman
- School of Kinesiology, University of Minnesota, Minneapolis, MN 55455, United States of America
| | - Alec M Basten
- School of Kinesiology, University of Minnesota, Minneapolis, MN 55455, United States of America
| | - Jacob R Sorensen
- School of Kinesiology, University of Minnesota, Minneapolis, MN 55455, United States of America
| | | | - Thomas J Lillquist
- School of Kinesiology, University of Minnesota, Minneapolis, MN 55455, United States of America
| | - Jarrod A Call
- Department of Physiology and Pharmacology, University of Georgia, Athens, GA 30602, United States of America
| | - Benjamin T Corona
- School of Medicine, Wake Forest University, Winston-Salem, NC 27101, United States of America
| | - Sarah M Greising
- School of Kinesiology, University of Minnesota, Minneapolis, MN 55455, United States of America.
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4
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Lee YI, Cacciani N, Wen Y, Zhang X, Hedström Y, Thompson W, Larsson L. Direct electrical stimulation impacts on neuromuscular junction morphology on both stimulated and unstimulated contralateral soleus. J Cachexia Sarcopenia Muscle 2023. [PMID: 37060275 DOI: 10.1002/jcsm.13235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 03/06/2023] [Accepted: 03/15/2023] [Indexed: 04/16/2023] Open
Abstract
BACKGROUND There is increasing evidence of crosstalk between organs. The neuromuscular junction (NMJ) is a peripheral chemical synapse whose function and morphology are sensitive to acetylcholine (ACh) release and muscle depolarization. In an attempt to improve our understanding of NMJ plasticity and muscle crosstalk, the effects of unilateral direct electrical stimulation of a hindlimb muscle on the NMJ were investigated in rats exposed long-term post-synaptic neuromuscular blockade. METHODS Sprague Dawley rats were subjected to post-synaptic blockade of neuromuscular transmission by systemic administration of α-cobrotoxin and mechanically ventilated for up to 8 days and compared with untreated sham operated controls and animals exposed to unilateral chronic electrical stimulation 12 h/day for 5 or 8 days. RESULTS NMJs produced axonal and glial sprouts (growth of processes that extend beyond the confines of the synapse defined by high-density aggregates of acetylcholine receptors [AChRs]) in response to post-synaptic neuromuscular blockade, but less than reported after peripheral denervation or pre-synaptic blockade. Direct electrical soleus muscle stimulation reduced the terminal Schwann cell (tSC) and axonal sprouting in both stimulated and non-stimulated contralateral soleus. Eight days chronic stimulation reduced (P < 0.001) the number of tSC sprouts on stimulated and non-stimulated soleus from 6.7 ± 0.5 and 6.9 ± 0.5 sprouts per NMJ, respectively, compared with 10.3 ± 0.9 tSC per NMJ (P < 0.001) in non-stimulated soleus from rats immobilized for 8 days. A similar reduction of axonal sprouts (P < 0.001) was observed in stimulated and non-stimulated contralateral soleus in response to chronic electrical stimulation. RNAseq-based gene expression analyses confirmed a restoring effect on both stimulated and unstimulated contralateral muscle. The cross-over effect was paralleled by increased cytokine/chemokine levels in stimulated and contralateral unstimulated muscle as well as in plasma. CONCLUSIONS Motor axon terminals and terminal Schwann cells at NMJs of rats subjected to post-synaptic neuromuscular blockade exhibited sprouting responses. These axonal and glial responses were likely dampened by a muscle-derived myokines released in an activity-dependent manner with both local and systemic effects.
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Affiliation(s)
- Young Il Lee
- Department of Biology, Texas A&M University, College Station, TX, USA
- Department of Pharmacology & Therapeutics, College of Medicine, University of Florida Myology Institute, University of Florida, Gainesville, FL, USA
| | - Nicola Cacciani
- Department of Physiology and Pharmacology, Basic and Clinical Muscle Biology Group, Karolinska Institutet, Stockholm, Sweden
| | - Ya Wen
- Department of Physiology and Pharmacology, Basic and Clinical Muscle Biology Group, Karolinska Institutet, Stockholm, Sweden
| | - Xiang Zhang
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Yvette Hedström
- Department of Physiology and Pharmacology, Basic and Clinical Muscle Biology Group, Karolinska Institutet, Stockholm, Sweden
| | - Wesley Thompson
- Department of Biology, Texas A&M University, College Station, TX, USA
- Section of Molecular Cell and Developmental Biology, The University of Texas, Austin, TX, USA
| | - Lars Larsson
- Department of Physiology and Pharmacology, Basic and Clinical Muscle Biology Group, Karolinska Institutet, Stockholm, Sweden
- Department of Clinical Neuroscience, Section of Clinical Neurophysiology, Karolinska Institutet, Stockholm, Sweden
- Viron Molecular Medicine Institute, Boston, MA, USA
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5
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Muscle 4EBP1 activation modifies the structure and function of the neuromuscular junction in mice. Nat Commun 2022; 13:7792. [PMID: 36526657 PMCID: PMC9758177 DOI: 10.1038/s41467-022-35547-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 12/09/2022] [Indexed: 12/23/2022] Open
Abstract
Dysregulation of mTOR complex 1 (mTORC1) activity drives neuromuscular junction (NMJ) structural instability during aging; however, downstream targets mediating this effect have not been elucidated. Here, we investigate the roles of two mTORC1 phosphorylation targets for mRNA translation, ribosome protein S6 kinase 1 (S6K1) and eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1), in regulating NMJ structural instability induced by aging and sustained mTORC1 activation. While myofiber-specific deletion of S6k1 has no effect on NMJ structural integrity, 4EBP1 activation in murine muscle induces drastic morphological remodeling of the NMJ with enhancement of synaptic transmission. Mechanistically, structural modification of the NMJ is attributed to increased satellite cell activation and enhanced post-synaptic acetylcholine receptor (AChR) turnover upon 4EBP1 activation. Considering that loss of post-synaptic myonuclei and reduced NMJ turnover are features of aging, targeting 4EBP1 activation could induce NMJ renewal by expanding the pool of post-synaptic myonuclei as an alternative intervention to mitigate sarcopenia.
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Dubuisson N, Versele R, Planchon C, Selvais CM, Noel L, Abou-Samra M, Davis-López de Carrizosa MA. Histological Methods to Assess Skeletal Muscle Degeneration and Regeneration in Duchenne Muscular Dystrophy. Int J Mol Sci 2022; 23:16080. [PMID: 36555721 PMCID: PMC9786356 DOI: 10.3390/ijms232416080] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 12/09/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is a progressive disease caused by the loss of function of the protein dystrophin. This protein contributes to the stabilisation of striated cells during contraction, as it anchors the cytoskeleton with components of the extracellular matrix through the dystrophin-associated protein complex (DAPC). Moreover, absence of the functional protein affects the expression and function of proteins within the DAPC, leading to molecular events responsible for myofibre damage, muscle weakening, disability and, eventually, premature death. Presently, there is no cure for DMD, but different treatments help manage some of the symptoms. Advances in genetic and exon-skipping therapies are the most promising intervention, the safety and efficiency of which are tested in animal models. In addition to in vivo functional tests, ex vivo molecular evaluation aids assess to what extent the therapy has contributed to the regenerative process. In this regard, the later advances in microscopy and image acquisition systems and the current expansion of antibodies for immunohistological evaluation together with the development of different spectrum fluorescent dyes have made histology a crucial tool. Nevertheless, the complexity of the molecular events that take place in dystrophic muscles, together with the rise of a multitude of markers for each of the phases of the process, makes the histological assessment a challenging task. Therefore, here, we summarise and explain the rationale behind different histological techniques used in the literature to assess degeneration and regeneration in the field of dystrophinopathies, focusing especially on those related to DMD.
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Affiliation(s)
- Nicolas Dubuisson
- Endocrinology, Diabetes and Nutrition Unit, Institute of Experimental and Clinical Research, Medical Sector, Université Catholique de Louvain (UCLouvain), Avenue Hippocrate 55, 1200 Brussels, Belgium
- Neuromuscular Reference Center, Cliniques Universitaires Saint-Luc (CUSL), Avenue Hippocrate 10, 1200 Brussels, Belgium
| | - Romain Versele
- Endocrinology, Diabetes and Nutrition Unit, Institute of Experimental and Clinical Research, Medical Sector, Université Catholique de Louvain (UCLouvain), Avenue Hippocrate 55, 1200 Brussels, Belgium
| | - Chloé Planchon
- Endocrinology, Diabetes and Nutrition Unit, Institute of Experimental and Clinical Research, Medical Sector, Université Catholique de Louvain (UCLouvain), Avenue Hippocrate 55, 1200 Brussels, Belgium
| | - Camille M. Selvais
- Endocrinology, Diabetes and Nutrition Unit, Institute of Experimental and Clinical Research, Medical Sector, Université Catholique de Louvain (UCLouvain), Avenue Hippocrate 55, 1200 Brussels, Belgium
| | - Laurence Noel
- Endocrinology, Diabetes and Nutrition Unit, Institute of Experimental and Clinical Research, Medical Sector, Université Catholique de Louvain (UCLouvain), Avenue Hippocrate 55, 1200 Brussels, Belgium
| | - Michel Abou-Samra
- Endocrinology, Diabetes and Nutrition Unit, Institute of Experimental and Clinical Research, Medical Sector, Université Catholique de Louvain (UCLouvain), Avenue Hippocrate 55, 1200 Brussels, Belgium
| | - María A. Davis-López de Carrizosa
- Endocrinology, Diabetes and Nutrition Unit, Institute of Experimental and Clinical Research, Medical Sector, Université Catholique de Louvain (UCLouvain), Avenue Hippocrate 55, 1200 Brussels, Belgium
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
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7
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Hulen J, Kenny D, Black R, Hallgren J, Hammond KG, Bredahl EC, Wickramasekara RN, Abel PW, Stessman HAF. KMT5B is required for early motor development. Front Genet 2022; 13:901228. [PMID: 36035149 PMCID: PMC9411648 DOI: 10.3389/fgene.2022.901228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 07/11/2022] [Indexed: 11/13/2022] Open
Abstract
Disruptive variants in lysine methyl transferase 5B (KMT5B/SUV4-20H1) have been identified as likely-pathogenic among humans with neurodevelopmental phenotypes including motor deficits (i.e., hypotonia and motor delay). However, the role that this enzyme plays in early motor development is largely unknown. Using a Kmt5b gene trap mouse model, we assessed neuromuscular strength, skeletal muscle weight (i.e., muscle mass), neuromuscular junction (NMJ) structure, and myofiber type, size, and distribution. Tests were performed over developmental time (postnatal days 17 and 44) to represent postnatal versus adult structures in slow- and fast-twitch muscle types. Prior to the onset of puberty, slow-twitch muscle weight was significantly reduced in heterozygous compared to wild-type males but not females. At the young adult stage, we identified decreased neuromuscular strength, decreased skeletal muscle weights (both slow- and fast-twitch), increased NMJ fragmentation (in slow-twitch muscle), and smaller myofibers in both sexes. We conclude that Kmt5b haploinsufficiency results in a skeletal muscle developmental deficit causing reduced muscle mass and body weight.
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Affiliation(s)
- Jason Hulen
- Department of Pharmacology and Neuroscience, School of Medicine, Creighton University, Omaha, NE, United States
| | - Dorothy Kenny
- Department of Pharmacology and Neuroscience, School of Medicine, Creighton University, Omaha, NE, United States
| | - Rebecca Black
- Department of Pharmacology and Neuroscience, School of Medicine, Creighton University, Omaha, NE, United States
| | - Jodi Hallgren
- Department of Pharmacology and Neuroscience, School of Medicine, Creighton University, Omaha, NE, United States
| | - Kelley G. Hammond
- Department of Exercise Science, College of Arts and Sciences, Creighton University, Omaha, NE, United States
| | - Eric C. Bredahl
- Department of Exercise Science, College of Arts and Sciences, Creighton University, Omaha, NE, United States
| | - Rochelle N. Wickramasekara
- Department of Pharmacology and Neuroscience, School of Medicine, Creighton University, Omaha, NE, United States
- Molecular Diagnostic Laboratory, Boys Town National Research Hospital, Omaha, NE, United States
| | - Peter W. Abel
- Department of Pharmacology and Neuroscience, School of Medicine, Creighton University, Omaha, NE, United States
| | - Holly A. F. Stessman
- Department of Pharmacology and Neuroscience, School of Medicine, Creighton University, Omaha, NE, United States
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8
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Wang ZM, Messi ML, Rodrigues ACZ, Delbono O. Skeletal muscle sympathetic denervation disrupts the neuromuscular junction postterminal organization: A single-cell quantitative approach. Mol Cell Neurosci 2022; 120:103730. [PMID: 35489637 PMCID: PMC9793435 DOI: 10.1016/j.mcn.2022.103730] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 03/28/2022] [Accepted: 04/12/2022] [Indexed: 12/30/2022] Open
Abstract
The sympathetic nervous system (SNS) regulates skeletal muscle motor innervation and stabilizes the NMJ in health, disease and aging. Previous studies using both chemical (6-hydroxydopamine, 6-OHDA) and microsurgically-induced sympathetic denervation examined the NMJ organization and transmission in the mouse; however, a detailed quantification of the postterminal on larger hindlimb muscles involved in gait mechanics and posture is lacking. The purpose of this study was to determine whether targets of the sympathetic neuron (SN) exhibiting different intrinsic composition such as the fast-twitch extensor digitorum longus (EDL) and the slow-twitch soleus muscles differ in their response to SN deprivation, and to develop a strategy to accurately quantify the impact of sympathectomy on the NMJ postterminal including those fibers located deeper in the muscle. This approach included muscle fixed ex vivo or through transcardial perfusion in mice treated with 6-OHDA or control ascorbic acid. We measured NMJ postterminal mean terminal total area, number of postterminal fragments, mean fragment area, and mean distance between fragments in free-floating alpha-bungarotoxin-stained in 1038 isolated muscle fibers. We found that muscle fiber sympathetic innervation plays a crucial role in the structural organization of the motorneuron-myofiber synapse postterminal and its deprivation leads to AChR cluster dispersion or shrinking as described in various neuromuscular diseases and aging.
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Affiliation(s)
- Zhong-Min Wang
- Department of Internal Medicine, Section on Gerontology and Geriatric Medicine, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States of America
| | - María Laura Messi
- Department of Internal Medicine, Section on Gerontology and Geriatric Medicine, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States of America
| | - Anna Carolina Zaia Rodrigues
- Department of Internal Medicine, Section on Gerontology and Geriatric Medicine, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States of America,the Neuroscience Program, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States of America
| | - Osvaldo Delbono
- Department of Internal Medicine, Section on Gerontology and Geriatric Medicine, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States of America,the Neuroscience Program, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States of America,Sticht Center for Healthy Aging and Alzheimer’s Prevention, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States of America,Corresponding author at: Wake Forest School of Medicine, Department of Internal Medicine, Gerontology, Medical Center Boulevard, Winston-Salem, NC 27157, United States of America. (O. Delbono)
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9
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Staunton CA, Owen ED, Hemmings K, Vasilaki A, McArdle A, Barrett-Jolley R, Jackson MJ. Skeletal muscle transcriptomics identifies common pathways in nerve crush injury and ageing. Skelet Muscle 2022; 12:3. [PMID: 35093178 PMCID: PMC8800362 DOI: 10.1186/s13395-021-00283-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 11/24/2021] [Indexed: 12/16/2022] Open
Abstract
Motor unit remodelling involving repeated denervation and re-innervation occurs throughout life. The efficiency of this process declines with age contributing to neuromuscular deficits. This study investigated differentially expressed genes (DEG) in muscle following peroneal nerve crush to model motor unit remodelling in C57BL/6 J mice. Muscle RNA was isolated at 3 days post-crush, RNA libraries were generated using poly-A selection, sequenced and analysed using gene ontology and pathway tools. Three hundred thirty-four DEG were found in quiescent muscle from (26mnth) old compared with (4-6mnth) adult mice and these same DEG were present in muscle from adult mice following nerve crush. Peroneal crush induced 7133 DEG in muscles of adult and 699 DEG in muscles from old mice, although only one DEG (ZCCHC17) was found when directly comparing nerve-crushed muscles from old and adult mice. This analysis revealed key differences in muscle responses which may underlie the diminished ability of old mice to repair following nerve injury.
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Affiliation(s)
- C A Staunton
- MRC- Versus Arthritis Research Centre for Integrated research into Musculoskeletal Ageing (CIMA), Department of Musculoskeletal and Ageing Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, L7 8TX, UK
| | - E D Owen
- MRC- Versus Arthritis Research Centre for Integrated research into Musculoskeletal Ageing (CIMA), Department of Musculoskeletal and Ageing Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, L7 8TX, UK
| | - K Hemmings
- MRC- Versus Arthritis Research Centre for Integrated research into Musculoskeletal Ageing (CIMA), Department of Musculoskeletal and Ageing Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, L7 8TX, UK
| | - A Vasilaki
- MRC- Versus Arthritis Research Centre for Integrated research into Musculoskeletal Ageing (CIMA), Department of Musculoskeletal and Ageing Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, L7 8TX, UK
| | - A McArdle
- MRC- Versus Arthritis Research Centre for Integrated research into Musculoskeletal Ageing (CIMA), Department of Musculoskeletal and Ageing Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, L7 8TX, UK
| | - R Barrett-Jolley
- MRC- Versus Arthritis Research Centre for Integrated research into Musculoskeletal Ageing (CIMA), Department of Musculoskeletal and Ageing Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, L7 8TX, UK
| | - M J Jackson
- MRC- Versus Arthritis Research Centre for Integrated research into Musculoskeletal Ageing (CIMA), Department of Musculoskeletal and Ageing Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, L7 8TX, UK.
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10
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Gutiérrez J, Gonzalez D, Escalona-Rivano R, Takahashi C, Brandan E. Reduced RECK levels accelerate skeletal muscle differentiation, improve muscle regeneration, and decrease fibrosis. FASEB J 2021; 35:e21503. [PMID: 33811686 DOI: 10.1096/fj.202001646rr] [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: 08/19/2020] [Revised: 02/07/2021] [Accepted: 02/19/2021] [Indexed: 12/15/2022]
Abstract
The muscle regeneration process requires a properly assembled extracellular matrix (ECM). Its homeostasis depends on the activity of different matrix-metalloproteinases (MMPs). The reversion-inducing-cysteine-rich protein with kazal motifs (RECK) is a membrane-anchored protein that negatively regulates the activity of different MMPs. However, the role of RECK in the process of skeletal muscle differentiation, regeneration, and fibrosis has not been elucidated. Here, we show that during skeletal muscle differentiation of C2C12 myoblasts and in satellite cells on isolated muscle fibers, RECK is transiently up regulated. C2C12 myoblasts with reduced RECK levels are more prone to enter the differentiation program, showing an accelerated differentiation process. Notch-1 signaling was reduced, while p38 and AKT signaling were augmented in myoblasts with decreased RECK levels. Overexpression of RECK restores the normal differentiation process but diminished the ability to form myotubes. Transient up-regulation of RECK occurs during skeletal muscle regeneration, which was accelerated in RECK-deficient mice (Reck±). RECK, MMPs and ECM proteins augmented in chronically damaged WT muscle, a model of muscle fibrosis. In this model, RECK ± mice showed diminished fibrosis compared to WT. These results strongly suggest that RECK is acting as a potential myogenic repressor during muscle formation and regeneration, emerging as a new player in these processes, and as a potential target to treat individuals with the muscle-wasting disease.
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Affiliation(s)
- Jaime Gutiérrez
- Cellular Signaling and Differentiation Laboratory (CSDL), School of Medical Technology, Health Sciences Faculty, Universidad San Sebastian, Santiago, Chile.,Centro de Regeneración y Envejecimiento (CARE), Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - David Gonzalez
- Centro de Regeneración y Envejecimiento (CARE), Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Rodrigo Escalona-Rivano
- Cellular Signaling and Differentiation Laboratory (CSDL), School of Medical Technology, Health Sciences Faculty, Universidad San Sebastian, Santiago, Chile
| | - Chiaki Takahashi
- Oncology and Molecular Biology, Cancer and Stem Cell Research Program, Cancer Research Institute, Kanazawa University, Kanazawa, Japan
| | - Enrique Brandan
- Centro de Regeneración y Envejecimiento (CARE), Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.,Fundación Ciencia & Vida, Santiago, Chile
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11
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The emerging role of the sympathetic nervous system in skeletal muscle motor innervation and sarcopenia. Ageing Res Rev 2021; 67:101305. [PMID: 33610815 DOI: 10.1016/j.arr.2021.101305] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 01/06/2021] [Accepted: 02/15/2021] [Indexed: 12/30/2022]
Abstract
Examining neural etiologic factors'role in the decline of neuromuscular function with aging is essential to our understanding of the mechanisms underlying sarcopenia, the age-dependent decline in muscle mass, force and power. Innervation of the skeletal muscle by both motor and sympathetic axons has been established, igniting interest in determining how the sympathetic nervous system (SNS) affect skeletal muscle composition and function throughout the lifetime. Selective expression of the heart and neural crest derivative 2 gene in peripheral SNs increases muscle mass and force regulating skeletal muscle sympathetic and motor innervation; improving acetylcholine receptor stability and NMJ transmission; preventing inflammation and myofibrillar protein degradation; increasing autophagy; and probably enhancing protein synthesis. Elucidating the role of central SNs will help to define the coordinated response of the visceral and neuromuscular system to physiological and pathological challenges across ages. This review discusses the following questions: (1) Does the SNS regulate skeletal muscle motor innervation? (2) Does the SNS regulate presynaptic and postsynaptic neuromuscular junction (NMJ) structure and function? (3) Does sympathetic neuron (SN) regulation of NMJ transmission decline with aging? (4) Does maintenance of SNs attenuate aging sarcopenia? and (5) Do central SN group relays influence sympathetic and motor muscle innervation?
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12
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Pinto CG, Leite APS, Sartori AA, Tibúrcio FC, Barraviera B, Junior RSF, Filadelpho AL, de Carvalho SC, Matheus SMM. Heterologous fibrin biopolymer associated to a single suture stitch enables the return of neuromuscular junction to its mature pattern after peripheral nerve injury. Injury 2021; 52:731-737. [PMID: 33902866 DOI: 10.1016/j.injury.2020.10.070] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 09/26/2020] [Accepted: 10/15/2020] [Indexed: 02/07/2023]
Abstract
Denervation leads to severe atrophy of neuromuscular junction (NMJ) structure including decrease of the expression of fundamental proteins. Up to now, conventional suture has been the gold standard method used to correct this injury. Fibrin sealant is one of the alternatives proposed to optimize this method. This study verified if the association of fibrin sealant - Heterologous Fibrin Biopolymer (HFB) and a single suture stitch promotes return of morphology and NMJ structure to mature pattern after peripheral nerve injury. Forty Wistar rats were distributed into 4 groups: Sham-Control (SC), Denervated-Control (DC), Suture-Lesion (SL) and Suture-Lesion + HFB (SFS). In SC group only the right sciatic nerve identification was done. In DC, SL and SFS groups fixation of nerve stumps on musculature immediately after neurotmesis was performed. After seven days, stump reconnection with 3 stitches in SL and a single stitch associated with HFB in SFS were done. After sixty days right soleus muscles were prepared for nicotinic acetylcholine receptors (nAChRs) and nerve terminal confocal analyses, and for nAChRs (α1, ε e γ), S100, Agrin, LRP-4, MMP-3, Rapsyn western blotting analyses. SC group presented normal morphology. In DC group it was observed flattening of NMJ, fragmentation of nAChRs and tangled nerve terminals. The majority of the parameters of SL and SFS groups presented values in between SC and DC groups. There was an increase of relative planar area in these groups (SL and SFS) highlighting that there was less nAChRs fragmentation and the values of protein expression showed return of nAChRs to mature pattern. Use of HFB associated with a single suture stitch decreased surgical time, minimized suture injuries, did not alter nerve regeneration and presented potential to reestablish the NMJ apparatus. These consolidated results encourage surgeons to develop future clinical trials to install definitively this new approach both for reconstructive surgery and neurosurgery.
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Affiliation(s)
- Carina Guidi Pinto
- Graduate Program in Surgery and Translational Medicine, Medical School, São Paulo State University (Unesp), Botucatu, São Paulo, Brazil; Department of Structural and Functional Biology (Anatomy Sector), Institute of Biosciences, São Paulo State University (Unesp), Botucatu, São Paulo, Brazil
| | - Ana Paula Silveira Leite
- Graduate Program in Surgery and Translational Medicine, Medical School, São Paulo State University (Unesp), Botucatu, São Paulo, Brazil; Department of Structural and Functional Biology (Anatomy Sector), Institute of Biosciences, São Paulo State University (Unesp), Botucatu, São Paulo, Brazil
| | - Arthur Alves Sartori
- Department of Structural and Functional Biology (Anatomy Sector), Institute of Biosciences, São Paulo State University (Unesp), Botucatu, São Paulo, Brazil
| | - Felipe Cantore Tibúrcio
- Graduate Program in Surgery and Translational Medicine, Medical School, São Paulo State University (Unesp), Botucatu, São Paulo, Brazil; Department of Structural and Functional Biology (Anatomy Sector), Institute of Biosciences, São Paulo State University (Unesp), Botucatu, São Paulo, Brazil
| | - Benedito Barraviera
- Center for the Studies of Venoms and Venomous Animals (CEVAP), São Paulo State University (Unesp), Botucatu, São Paulo, Brazil
| | - Rui Seabra Ferreira Junior
- Center for the Studies of Venoms and Venomous Animals (CEVAP), São Paulo State University (Unesp), Botucatu, São Paulo, Brazil
| | - André Luis Filadelpho
- Department of Structural and Functional Biology (Anatomy Sector), Institute of Biosciences, São Paulo State University (Unesp), Botucatu, São Paulo, Brazil
| | | | - Selma Maria Michelin Matheus
- Department of Structural and Functional Biology (Anatomy Sector), Institute of Biosciences, São Paulo State University (Unesp), Botucatu, São Paulo, Brazil.
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13
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Zakyrjanova GF, Giniatullin AR, Mukhutdinova KA, Kuznetsova EA, Petrov AM. Early differences in membrane properties at the neuromuscular junctions of ALS model mice: Effects of 25-hydroxycholesterol. Life Sci 2021; 273:119300. [PMID: 33662433 DOI: 10.1016/j.lfs.2021.119300] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2020] [Revised: 02/13/2021] [Accepted: 02/25/2021] [Indexed: 12/11/2022]
Abstract
AIMS Plasma hyperlipidemia is a protective factor in amyotrophic lateral sclerosis (ALS) while cholesterol-lowering drugs aggravate the pathology. We hypothesize that this phenomenon can be linked with membrane lipid alterations in the neuromuscular junctions (NMJs) occurring before motor neuron loss. METHODS Neurotransmitter release in parallel with lipid membrane properties in diaphragm NMJs of SOD1G93A (mSOD) mice at nine weeks of age (pre-onset stage) were assessed. KEY FINDINGS Despite on slight changes in spontaneous and evoked quantum release of acetylcholine, extracellular levels of choline at resting conditions, an indicator of non-quantum release, were significantly increased in mSOD mice. The use of lipid-sensitive fluorescent probes points to lipid raft disruption in the NMJs of mSOD mice. However, content of cholesterol, a key raft component was unchanged implying another pathway responsible for the loss of raft integrity. In the mSOD mice we found marked increase in levels of raft-destabilizing lipid ceramide. This was accompanied by enhanced ability to uptake of exogenous ceramide in NMJs. Acute and chronic administration of 25-hydroxycholesterol, whose levels increase due to hypercholesterolemia, recovered early alterations in membrane properties. Furthermore, chronic treatment with 25-hydroxycholesterol prevented increase in ceramide and extracellular choline levels as well as suppressed lipid peroxidation of NMJ membranes and fragmentation of end plates. SIGNIFICANCE Thus, lipid raft disruption likely due to ceramide accumulation could be early event in ALS which may trigger neuromuscular abnormalities. Cholesterol derivative 25-hydroxycholesterol may serve as a molecule restoring the membrane and functional properties of NMJs at the early stage.
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Affiliation(s)
- Guzel F Zakyrjanova
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky Street, box 30, Kazan 420111, Russia; Institute of Neuroscience, Kazan State Medial University, 49 Butlerova Street, Kazan, 420012, Russia
| | - Arthur R Giniatullin
- Department of Normal Physiology, Kazan State Medial University, 49 Butlerova Street, Kazan 420012, Russia
| | - Kamilla A Mukhutdinova
- Institute of Neuroscience, Kazan State Medial University, 49 Butlerova Street, Kazan, 420012, Russia
| | - Eva A Kuznetsova
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky Street, box 30, Kazan 420111, Russia
| | - Alexey M Petrov
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky Street, box 30, Kazan 420111, Russia; Institute of Neuroscience, Kazan State Medial University, 49 Butlerova Street, Kazan, 420012, Russia.
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14
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Cossins J, Webster R, Maxwell S, Rodríguez Cruz PM, Knight R, Llewelyn JG, Shin JY, Palace J, Beeson D. Congenital myasthenic syndrome due to a TOR1AIP1 mutation: a new disease pathway for impaired synaptic transmission. Brain Commun 2020; 2:fcaa174. [PMID: 33215087 PMCID: PMC7660151 DOI: 10.1093/braincomms/fcaa174] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 07/24/2020] [Accepted: 08/12/2020] [Indexed: 02/06/2023] Open
Abstract
Congenital myasthenic syndromes are inherited disorders characterized by fatiguable muscle weakness resulting from impaired signal transmission at the neuromuscular junction. Causative mutations have been identified in genes that can affect the synaptic function or structure. We identified a homozygous frameshift deletion c.127delC, p. Pro43fs in TOR1AIP1 in two siblings with limb-girdle weakness and impaired transmission at the neuromuscular synapse. TOR1AIP1 encodes the inner nuclear membrane protein lamin-associated protein 1. On muscle biopsy from the index case, lamin-associated protein 1 was absent from myonuclei. A mouse model with lamin-associated protein 1 conditionally knocked out in striated muscle was used to analyse the role of lamin-associated protein 1 in synaptic dysfunction. Model mice develop fatiguable muscle weakness as demonstrated by using an inverted screen hang test. Electromyography on the mice revealed a decrement on repetitive nerve stimulation. Ex vivo analysis of hemi-diaphragm preparations showed both miniature and evoked end-plate potential half-widths were prolonged which was associated with upregulation of the foetal acetylcholine receptor γ subunit. Neuromuscular junctions on extensor digitorum longus muscles were enlarged and fragmented, and the number of subsynaptic nuclei was significantly increased. Following these findings, electromyography was performed on cases of other nuclear envelopathies caused by mutations in LaminA/C or emerin, but decrement on repetitive nerve stimulation or other indications of defective neuromuscular transmission were not seen. Thus, this report highlights the first nuclear membrane protein in which defective function can lead to impaired synaptic transmission.
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Affiliation(s)
- Judith Cossins
- Neurosciences Group, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
| | - Richard Webster
- Neurosciences Group, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
| | - Susan Maxwell
- Neurosciences Group, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
| | - Pedro M Rodríguez Cruz
- Neurosciences Group, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
| | - Ravi Knight
- Department of Clinical Neurology, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - John Gareth Llewelyn
- Neurology Department, University Hospital of Wales, Heath Park, Cardiff CF14 4XW, UK
| | - Ji-Yeon Shin
- Department of Medicine, Columbia University Medical Centre, New York, NY 10032, USA
| | - Jacqueline Palace
- Department of Clinical Neurology, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - David Beeson
- Neurosciences Group, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
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15
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Lifetime analysis of mdx skeletal muscle reveals a progressive pathology that leads to myofiber loss. Sci Rep 2020; 10:17248. [PMID: 33057110 PMCID: PMC7560899 DOI: 10.1038/s41598-020-74192-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 09/23/2020] [Indexed: 02/06/2023] Open
Abstract
The muscular dystrophy X-linked mouse (mdx) is the most commonly used preclinical model for Duchenne muscular dystrophy. Although disease progression in the mouse does not perfectly model the human disease, it shares many pathological features. Early characterizations of the model reported severe pathology through early adulthood followed by disease stabilization. As a result, research in the mdx mouse has largely focused on early adulthood. The overarching goal of this study is to improve the understanding of the mdx mouse model by tracking pathological features of the disease throughout life. We performed a thorough characterization of myofiber pathology in mdx mice from 2 weeks to 2 years of age. We report that individual mdx muscle fibers undergo progressive hypertrophy that continues through the lifespan. Despite massive hypertrophy on the myofiber level, we report no hypertrophy on the muscle level. These seemingly contradictory findings are explained by previously underappreciated myofiber loss in mdx mice. We conclude that due to myofiber loss, in combination with the progressive nature of other pathological features, aged mdx muscle tissue provides reliable benchmarks for disease progression that may be valuable in testing the efficacy of therapeutics for Duchenne muscular dystrophy.
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16
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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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17
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Morphological remodeling during recovery of the neuromuscular junction from terminal Schwann cell ablation in adult mice. Sci Rep 2020; 10:11132. [PMID: 32636481 PMCID: PMC7341867 DOI: 10.1038/s41598-020-67630-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 06/09/2020] [Indexed: 12/22/2022] Open
Abstract
Schwann cells (SCs) are integral to the formation and function of the peripheral nervous system (PNS). Exemplifying their importance, the loss or dysfunction of SCs is a feature of a myriad of diseases and conditions that compromise the PNS. Thus, it remains essential to understand the rules that govern the proliferation, differentiation and reconnection of Schwann cells with peripheral axons. Here, we examined the consequences of locally and acutely ablating terminal Schwann cells (tSCs) at the adult mouse neuromuscular junction (NMJ) by using mice expressing diphtheria toxin receptor (DTR) preferentially in tSCs compared to myelinating SCs followed by local application of diphtheria toxin (DTX). After DTX application, tSCs died but, importantly and contrary to expectations, their associated motor axons did not fully degenerate. Within 3 weeks, tSCs returned and reestablished coverage of the synapse with increased numbers. Furthermore, the post-synaptic muscle fibers displayed increased distinct clusters of acetylcholine receptors and axon terminals exhibited numerous terminal varicosities. The lack of degeneration of bare motor axon terminals and the morphological remodeling that occurs upon the return of tSCs to the NMJ may have wider implications for the mechanisms governing tSC occupancy of the adult NMJ and for conditions that adversely affect tSCs.
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18
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Lee YI, Rimer M. Wesley J. Thompson (1947-2019). Front Mol Neurosci 2020; 13:91. [PMID: 32595450 PMCID: PMC7303338 DOI: 10.3389/fnmol.2020.00091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 04/30/2020] [Indexed: 11/16/2022] Open
Affiliation(s)
- Young Il Lee
- Department of Biology, Texas A&M University, College Station, TX, United States
| | - Mendell Rimer
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University Health Science Center, Bryan, TX, United States
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19
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Hastings RL, Massopust RT, Haddix SG, Lee YI, Thompson WJ. Exclusive vital labeling of myonuclei for studying myonuclear arrangement in mouse skeletal muscle tissue. Skelet Muscle 2020; 10:15. [PMID: 32381068 PMCID: PMC7204059 DOI: 10.1186/s13395-020-00233-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 04/23/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The arrangement of myonuclei in skeletal muscle tissue has long been used as a biomarker for muscle health, but there is a dearth of in vivo exploration of potential effects of myonuclear organization on the function and regeneration of skeletal muscle because traditional nuclear stains are performed on postmortem tissue. Therefore, we sought a transgenic method to produce a selective and persistent myonuclear label in whole muscles of living mice. METHODS We bred together a mouse line with skeletal muscle fiber-selective expression of Cre recombinase and a second mouse line with a Cre-inducible fluorescently tagged histone protein to generate a mouse line that produces a myonuclear label suitable for vital imaging and histology of fixed tissue. We tested the effectiveness of this vital label in three conditions known to generate abnormal myonuclear positioning. First, we injured myofibers of young mice with cardiotoxin. Second, this nuclear label was bred into a murine model of Duchenne muscular dystrophy. Finally, we examined old mice from this line that have undergone the natural aging process. Welch's t test was used to compare wild type and transgenic mice. RESULTS The resulting mouse line transgenically produces a vital red fluorescent label of myonuclei, which facilitates their in vivo imaging in skeletal muscle tissue. Transgenic fluorescent labeling of myonuclei has no significant effect on skeletal muscle function, as determined by twitch and tetanic force recordings. In each muscle examined, including those under damaged, dystrophic, and aged conditions, the labeled myonuclei exhibit morphology consistent with established literature, and reveal a specialized arrangement of subsynaptic myonuclei at the neuromuscular junction. CONCLUSIONS Taken together, our results demonstrate that this mouse line provides a versatile tool to selectively visualize myonuclei within both living and fixed preparations of healthy, injured, diseased, and aged muscles.
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Affiliation(s)
- Robert Louis Hastings
- Texas A&M Institute for Neuroscience, College Station, TX, USA.
- Department of Biology, Texas A&M University, College Station, TX, USA.
| | - Ryan T Massopust
- Texas A&M Institute for Neuroscience, College Station, TX, USA
- Department of Biology, Texas A&M University, College Station, TX, USA
| | - Seth G Haddix
- Texas A&M Institute for Neuroscience, College Station, TX, USA
- Department of Biology, Texas A&M University, College Station, TX, USA
| | - Young Il Lee
- Department of Biology, Texas A&M University, College Station, TX, USA
| | - Wesley J Thompson
- Texas A&M Institute for Neuroscience, College Station, TX, USA
- Department of Biology, Texas A&M University, College Station, TX, USA
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20
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Jablonka-Shariff A, Lu CY, Campbell K, Monk KR, Snyder-Warwick AK. Gpr126/Adgrg6 contributes to the terminal Schwann cell response at the neuromuscular junction following peripheral nerve injury. Glia 2019; 68:1182-1200. [PMID: 31873966 DOI: 10.1002/glia.23769] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 12/03/2019] [Accepted: 12/10/2019] [Indexed: 12/12/2022]
Abstract
Gpr126/Adgrg6 is an adhesion G protein-coupled receptor essential for Schwann cell (SC) myelination with important contributions to repair after nerve crush injury. Despite critical functions in myelinating SCs, the role of Gpr126 within nonmyelinating terminal Schwann cells (tSCs) at the neuromuscular junction (NMJ), is not known. tSCs have important functions in synaptic maintenance and reinnervation, and after injury tSCs extend cytoplasmic processes to guide regenerating axons to the denervated NMJ. In this study, we show that Gpr126 is expressed in tSCs, and that absence of Gpr126 in SCs (SC-specific Gpr126 knockout, cGpr126) results in a NMJ maintenance defect in the hindlimbs of aged mice, but not in young adult mice. After nerve transection and repair, cGpr126 mice display delayed NMJ reinnervation, altered tSC morphology with decreased S100β expression, and reduced tSC cytoplasmic process extensions. The immune response promoting reinnervation at the NMJ following nerve injury is also altered with decreased macrophage infiltration, Tnfα, and anomalous cytokine expression compared to NMJs of control mice. In addition, Vegfa expression is decreased in muscle, suggesting that cGpr126 non-cell autonomously modulates angiogenesis after nerve injury. In sum, cGpr126 mice demonstrated delayed NMJ reinnervation and decreased muscle mass following nerve transection and repair compared to control littermates. The integral function of Gpr126 in tSCs at the NMJ provides the framework for new therapeutic targets for neuromuscular disease.
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Affiliation(s)
- Albina Jablonka-Shariff
- Division of Plastic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, Missouri
| | - Chuieng-Yi Lu
- Division of Plastic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, Missouri.,Division of Reconstructive Microsurgery, Department of Plastic Surgery, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan, Taiwan
| | - Katherine Campbell
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, Missouri
| | - Kelly R Monk
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri.,Vollum Institute, Oregon Health & Science University, Portland, Oregon
| | - Alison K Snyder-Warwick
- Division of Plastic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, Missouri
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21
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Neuromuscular Junction as an Entity of Nerve-Muscle Communication. Cells 2019; 8:cells8080906. [PMID: 31426366 PMCID: PMC6721719 DOI: 10.3390/cells8080906] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 08/13/2019] [Accepted: 08/14/2019] [Indexed: 12/11/2022] Open
Abstract
One of the crucial systems severely affected in several neuromuscular diseases is the loss of effective connection between muscle and nerve, leading to a pathological non-communication between the two tissues. The neuromuscular junction (NMJ) represents the critical region at the level of which muscle and nerve communicate. Defects in signal transmission between terminal nerve endings and muscle membrane is a common feature of several physio-pathologic conditions including aging and Amyotrophic Lateral Sclerosis (ALS). Nevertheless, controversy exists on whether pathological events beginning at the NMJ precede or follow loss of motor units. In this review, the role of NMJ in the physio-pathologic interplay between muscle and nerve is discussed.
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22
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Myasthenia Gravis: Pathogenic Effects of Autoantibodies on Neuromuscular Architecture. Cells 2019; 8:cells8070671. [PMID: 31269763 PMCID: PMC6678492 DOI: 10.3390/cells8070671] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 06/26/2019] [Accepted: 06/28/2019] [Indexed: 12/13/2022] Open
Abstract
Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction (NMJ). Autoantibodies target key molecules at the NMJ, such as the nicotinic acetylcholine receptor (AChR), muscle-specific kinase (MuSK), and low-density lipoprotein receptor-related protein 4 (Lrp4), that lead by a range of different pathogenic mechanisms to altered tissue architecture and reduced densities or functionality of AChRs, reduced neuromuscular transmission, and therefore a severe fatigable skeletal muscle weakness. In this review, we give an overview of the history and clinical aspects of MG, with a focus on the structure and function of myasthenic autoantigens at the NMJ and how they are affected by the autoantibodies' pathogenic mechanisms. Furthermore, we give a short overview of the cells that are implicated in the production of the autoantibodies and briefly discuss diagnostic challenges and treatment strategies.
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23
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Slater CR. 'Fragmentation' of NMJs: a sign of degeneration or regeneration? A long journey with many junctions. Neuroscience 2019; 439:28-40. [PMID: 31129203 DOI: 10.1016/j.neuroscience.2019.05.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 05/07/2019] [Accepted: 05/07/2019] [Indexed: 12/13/2022]
Abstract
Mammalian neuromuscular junctions (NMJs) often consist of curved bands of synaptic contact, about 3-6 μm wide, which resemble pretzels. This contrasts with the NMJs of most animal species which consist of a cluster of separate synaptic spots, each of which is also about 3-6 μm across. In a number of situations, including a variety of disease states as well as normal ageing, mammalian NMJs acquire a more 'fragmented' appearance that resembles somewhat that of other species. This 'fragmentation' of the NMJ has sometimes been interpreted as a 'disintegration' or 'degeneration', with the suggestion that it might be associated with impaired neuromuscular transmission. An alternative view is that NMJ fragmentation is the outcome of a normal process by which the NMJ is maintained in an effective state. In this highly personal commentary, I cite a number of examples of this and point out that although the 'pretzel' form arises during normal development as a result of the sculpting of an immature synaptic 'plaque', in virtually all situations where new synaptic contact is established in adult mammals this occurs by the addition of new synaptic 'spots' rather than by the extension, or neoformation, of 'pretzels'. Further, where appropriate studies have been performed, no evidence of a correlation between the degree of fragmentation and the efficacy of transmission has emerged. It may therefore be more appropriate to consider NMJ 'fragmentation' as a form of regeneration, rather than of degeneration. This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.
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Affiliation(s)
- Clarke R Slater
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK.
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24
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McArdle A, Pollock N, Staunton CA, Jackson MJ. Aberrant redox signalling and stress response in age-related muscle decline: Role in inter- and intra-cellular signalling. Free Radic Biol Med 2019; 132:50-57. [PMID: 30508577 PMCID: PMC6709668 DOI: 10.1016/j.freeradbiomed.2018.11.038] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 11/29/2018] [Accepted: 11/29/2018] [Indexed: 12/22/2022]
Abstract
Age-associated frailty is predominantly due to loss of muscle mass and function. The loss of muscle mass is also associated with a greater loss of muscle strength, suggesting that the remaining muscle fibres are weaker than those of adults. The mechanisms by which muscle is lost with age are unclear, but in this review we aim to pull together various strands of evidence to explain how muscle contractions support proteostasis in non-muscle tissues, particularly focussed on the production and potential transfer of Heat Shock Proteins (HSPs) and how this may fail during ageing, Furthermore we will identify logical approaches, based on this hypothesis, by which muscle loss in ageing may be reduced. Skeletal muscle generates superoxide and nitric oxide at rest and this generation is increased by contractile activity. In adults, this increased generation of reactive oxygen and nitrogen species (RONS) activate redox-sensitive transcription factors such as nuclear factor κB (NFκB), activator protein-1 (AP1) and heat shock factor 1 (HSF1), resulting in increases in cytoprotective proteins such as the superoxide dismutases, catalase and heat shock proteins that prevent oxidative damage to tissues and facilitate remodelling and proteostasis in both an intra- and inter-cellular manner. During ageing, the ability of skeletal muscle from aged organisms to respond to an increase in ROS generation by increased expression of cytoprotective proteins through activation of redox-sensitive transcription factors is severely attenuated. This age-related lack of physiological adaptations to the ROS induced by contractile activity appears to contribute to a loss of ROS homeostasis, increased oxidative damage and age-related dysfunction in skeletal muscle and potentially other tissues.
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Affiliation(s)
- Anne McArdle
- MRC-Arthritis Research UK Centre for Integrated Research into Musculoskeletal Ageing (CIMA), Institute of Ageing and Chronic Disease, University of Liverpool, L7 8TX, United Kingdom.
| | - Natalie Pollock
- MRC-Arthritis Research UK Centre for Integrated Research into Musculoskeletal Ageing (CIMA), Institute of Ageing and Chronic Disease, University of Liverpool, L7 8TX, United Kingdom
| | - Caroline A Staunton
- MRC-Arthritis Research UK Centre for Integrated Research into Musculoskeletal Ageing (CIMA), Institute of Ageing and Chronic Disease, University of Liverpool, L7 8TX, United Kingdom
| | - Malcolm J Jackson
- MRC-Arthritis Research UK Centre for Integrated Research into Musculoskeletal Ageing (CIMA), Institute of Ageing and Chronic Disease, University of Liverpool, L7 8TX, United Kingdom
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Larsson L, Degens H, Li M, Salviati L, Lee YI, Thompson W, Kirkland JL, Sandri M. Sarcopenia: Aging-Related Loss of Muscle Mass and Function. Physiol Rev 2019; 99:427-511. [PMID: 30427277 DOI: 10.1152/physrev.00061.2017] [Citation(s) in RCA: 719] [Impact Index Per Article: 143.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Sarcopenia is a loss of muscle mass and function in the elderly that reduces mobility, diminishes quality of life, and can lead to fall-related injuries, which require costly hospitalization and extended rehabilitation. This review focuses on the aging-related structural changes and mechanisms at cellular and subcellular levels underlying changes in the individual motor unit: specifically, the perikaryon of the α-motoneuron, its neuromuscular junction(s), and the muscle fibers that it innervates. Loss of muscle mass with aging, which is largely due to the progressive loss of motoneurons, is associated with reduced muscle fiber number and size. Muscle function progressively declines because motoneuron loss is not adequately compensated by reinnervation of muscle fibers by the remaining motoneurons. At the intracellular level, key factors are qualitative changes in posttranslational modifications of muscle proteins and the loss of coordinated control between contractile, mitochondrial, and sarcoplasmic reticulum protein expression. Quantitative and qualitative changes in skeletal muscle during the process of aging also have been implicated in the pathogenesis of acquired and hereditary neuromuscular disorders. In experimental models, specific intervention strategies have shown encouraging results on limiting deterioration of motor unit structure and function under conditions of impaired innervation. Translated to the clinic, if these or similar interventions, by saving muscle and improving mobility, could help alleviate sarcopenia in the elderly, there would be both great humanitarian benefits and large cost savings for health care systems.
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Affiliation(s)
- Lars Larsson
- Department of Physiology and Pharmacology, Basic and Clinical Muscle Biology Group, Karolinska Institutet , Stockholm , Sweden ; Section of Clinical Neurophysiology, Department of Clinical Neuroscience, Karolinska Institutet , Stockholm , Sweden ; Department of Biobehavioral Health, The Pennsylvania State University , University Park, Pennsylvania ; School of Healthcare Science, Metropolitan University , Manchester , United Kingdom ; Institute of Sport Science and Innovations, Lithuanian Sports University , Kaunas , Lithuania ; Clinical Genetics Unit, Department of Woman and Child Health, University of Padova , Padova , Italy ; IRP Città della Speranza, Padova , Italy ; Department of Biology, Texas A&M University , College Station, Texas ; Robert and Arlene Kogod Center on Aging, Mayo Clinic , Rochester, Minnesota ; Department of Biomedical Science, Venetian Institute of Molecular Medicine, University of Padova , Padova , Italy
| | - Hans Degens
- Department of Physiology and Pharmacology, Basic and Clinical Muscle Biology Group, Karolinska Institutet , Stockholm , Sweden ; Section of Clinical Neurophysiology, Department of Clinical Neuroscience, Karolinska Institutet , Stockholm , Sweden ; Department of Biobehavioral Health, The Pennsylvania State University , University Park, Pennsylvania ; School of Healthcare Science, Metropolitan University , Manchester , United Kingdom ; Institute of Sport Science and Innovations, Lithuanian Sports University , Kaunas , Lithuania ; Clinical Genetics Unit, Department of Woman and Child Health, University of Padova , Padova , Italy ; IRP Città della Speranza, Padova , Italy ; Department of Biology, Texas A&M University , College Station, Texas ; Robert and Arlene Kogod Center on Aging, Mayo Clinic , Rochester, Minnesota ; Department of Biomedical Science, Venetian Institute of Molecular Medicine, University of Padova , Padova , Italy
| | - Meishan Li
- Department of Physiology and Pharmacology, Basic and Clinical Muscle Biology Group, Karolinska Institutet , Stockholm , Sweden ; Section of Clinical Neurophysiology, Department of Clinical Neuroscience, Karolinska Institutet , Stockholm , Sweden ; Department of Biobehavioral Health, The Pennsylvania State University , University Park, Pennsylvania ; School of Healthcare Science, Metropolitan University , Manchester , United Kingdom ; Institute of Sport Science and Innovations, Lithuanian Sports University , Kaunas , Lithuania ; Clinical Genetics Unit, Department of Woman and Child Health, University of Padova , Padova , Italy ; IRP Città della Speranza, Padova , Italy ; Department of Biology, Texas A&M University , College Station, Texas ; Robert and Arlene Kogod Center on Aging, Mayo Clinic , Rochester, Minnesota ; Department of Biomedical Science, Venetian Institute of Molecular Medicine, University of Padova , Padova , Italy
| | - Leonardo Salviati
- Department of Physiology and Pharmacology, Basic and Clinical Muscle Biology Group, Karolinska Institutet , Stockholm , Sweden ; Section of Clinical Neurophysiology, Department of Clinical Neuroscience, Karolinska Institutet , Stockholm , Sweden ; Department of Biobehavioral Health, The Pennsylvania State University , University Park, Pennsylvania ; School of Healthcare Science, Metropolitan University , Manchester , United Kingdom ; Institute of Sport Science and Innovations, Lithuanian Sports University , Kaunas , Lithuania ; Clinical Genetics Unit, Department of Woman and Child Health, University of Padova , Padova , Italy ; IRP Città della Speranza, Padova , Italy ; Department of Biology, Texas A&M University , College Station, Texas ; Robert and Arlene Kogod Center on Aging, Mayo Clinic , Rochester, Minnesota ; Department of Biomedical Science, Venetian Institute of Molecular Medicine, University of Padova , Padova , Italy
| | - Young Il Lee
- Department of Physiology and Pharmacology, Basic and Clinical Muscle Biology Group, Karolinska Institutet , Stockholm , Sweden ; Section of Clinical Neurophysiology, Department of Clinical Neuroscience, Karolinska Institutet , Stockholm , Sweden ; Department of Biobehavioral Health, The Pennsylvania State University , University Park, Pennsylvania ; School of Healthcare Science, Metropolitan University , Manchester , United Kingdom ; Institute of Sport Science and Innovations, Lithuanian Sports University , Kaunas , Lithuania ; Clinical Genetics Unit, Department of Woman and Child Health, University of Padova , Padova , Italy ; IRP Città della Speranza, Padova , Italy ; Department of Biology, Texas A&M University , College Station, Texas ; Robert and Arlene Kogod Center on Aging, Mayo Clinic , Rochester, Minnesota ; Department of Biomedical Science, Venetian Institute of Molecular Medicine, University of Padova , Padova , Italy
| | - Wesley Thompson
- Department of Physiology and Pharmacology, Basic and Clinical Muscle Biology Group, Karolinska Institutet , Stockholm , Sweden ; Section of Clinical Neurophysiology, Department of Clinical Neuroscience, Karolinska Institutet , Stockholm , Sweden ; Department of Biobehavioral Health, The Pennsylvania State University , University Park, Pennsylvania ; School of Healthcare Science, Metropolitan University , Manchester , United Kingdom ; Institute of Sport Science and Innovations, Lithuanian Sports University , Kaunas , Lithuania ; Clinical Genetics Unit, Department of Woman and Child Health, University of Padova , Padova , Italy ; IRP Città della Speranza, Padova , Italy ; Department of Biology, Texas A&M University , College Station, Texas ; Robert and Arlene Kogod Center on Aging, Mayo Clinic , Rochester, Minnesota ; Department of Biomedical Science, Venetian Institute of Molecular Medicine, University of Padova , Padova , Italy
| | - James L Kirkland
- Department of Physiology and Pharmacology, Basic and Clinical Muscle Biology Group, Karolinska Institutet , Stockholm , Sweden ; Section of Clinical Neurophysiology, Department of Clinical Neuroscience, Karolinska Institutet , Stockholm , Sweden ; Department of Biobehavioral Health, The Pennsylvania State University , University Park, Pennsylvania ; School of Healthcare Science, Metropolitan University , Manchester , United Kingdom ; Institute of Sport Science and Innovations, Lithuanian Sports University , Kaunas , Lithuania ; Clinical Genetics Unit, Department of Woman and Child Health, University of Padova , Padova , Italy ; IRP Città della Speranza, Padova , Italy ; Department of Biology, Texas A&M University , College Station, Texas ; Robert and Arlene Kogod Center on Aging, Mayo Clinic , Rochester, Minnesota ; Department of Biomedical Science, Venetian Institute of Molecular Medicine, University of Padova , Padova , Italy
| | - Marco Sandri
- Department of Physiology and Pharmacology, Basic and Clinical Muscle Biology Group, Karolinska Institutet , Stockholm , Sweden ; Section of Clinical Neurophysiology, Department of Clinical Neuroscience, Karolinska Institutet , Stockholm , Sweden ; Department of Biobehavioral Health, The Pennsylvania State University , University Park, Pennsylvania ; School of Healthcare Science, Metropolitan University , Manchester , United Kingdom ; Institute of Sport Science and Innovations, Lithuanian Sports University , Kaunas , Lithuania ; Clinical Genetics Unit, Department of Woman and Child Health, University of Padova , Padova , Italy ; IRP Città della Speranza, Padova , Italy ; Department of Biology, Texas A&M University , College Station, Texas ; Robert and Arlene Kogod Center on Aging, Mayo Clinic , Rochester, Minnesota ; Department of Biomedical Science, Venetian Institute of Molecular Medicine, University of Padova , Padova , Italy
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26
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Kang H, Tian L, Thompson WJ. Schwann cell guidance of nerve growth between synaptic sites explains changes in the pattern of muscle innervation and remodeling of synaptic sites following peripheral nerve injuries. J Comp Neurol 2019; 527:1388-1400. [PMID: 30620049 DOI: 10.1002/cne.24625] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Revised: 12/17/2018] [Accepted: 12/20/2018] [Indexed: 01/14/2023]
Abstract
Terminal Schwann cells (SCs) are nonmyelinating glia that are a prominent component of the neuromuscular junction (NMJ) where motor neurons form synapses onto muscle fibers. These cells play important roles not only in development and maintenance of the neuromuscular synapse but also restoring synaptic function after nerve damage. In response to muscle denervation, terminal SCs undergo dramatic changes in their gene expression patterns as well as in their morphology, such as extending elaborate processes into inter-junctional space. These SC processes serve as a path to guide axon terminal sprouts from nearby innervated junctions, promoting rapid reinnervation of denervated fibers. We studied the role of terminal SCs in synapse reformation by using two different fluorescent proteins to simultaneously label motor axons and SCs; we examined these junctions repeatedly in living animals using a fluorescence microscope. Here, we show that alterations in the patterns of muscle innervation following recovery from nerve injury can be explained by SC guidance of regenerating axons. In turn, this guidance leads to remodeling of the NMJ itself.
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Affiliation(s)
- Hyuno Kang
- Section of Molecular Cell and Developmental Biology, The University of Texas at Austin, Austin, Texas.,Gwangju Center, Korea Basic Science Institute, Gwangju, South Korea
| | - Le Tian
- Section of Molecular Cell and Developmental Biology, The University of Texas at Austin, Austin, Texas
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27
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Haddix SG, Lee YI, Kornegay JN, Thompson WJ. Cycles of myofiber degeneration and regeneration lead to remodeling of the neuromuscular junction in two mammalian models of Duchenne muscular dystrophy. PLoS One 2018; 13:e0205926. [PMID: 30379896 PMCID: PMC6209224 DOI: 10.1371/journal.pone.0205926] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Accepted: 10/03/2018] [Indexed: 12/02/2022] Open
Abstract
Mice lacking the sarcolemmal protein dystrophin, designated mdx, have been widely used as a model of Duchenne muscular dystrophy. Dystrophic mdx mice as they mature develop notable morphological abnormalities to their neuromuscular junctions, the peripheral cholinergic synapses responsible for activating muscle fibers. Most obviously the acetylcholine receptor aggregates are fragmented into small non-continuous, islands. This contrasts with wild type mice whose acetylcholine receptor aggregates are continuous and pretzel-shaped in appearance. We show here that these abnormalities in mdx mice are also present in a canine model of Duchenne muscular dystrophy and provide additional evidence to support the hypothesis that NMJ remodeling occurs due to myofiber degeneration and regeneration. Using a method to investigate synaptic AChR replacement, we show that neuromuscular junction remodeling in mdx animals is caused by muscle fiber degeneration and regeneration at the synaptic site and is mimicked by deliberate myofiber injury in wild type mice. Importantly, the innervating motor axon plays a crucial role in directing the remodeling of the neuromuscular junction in dystrophy, as has been recorded in aging and deliberate muscle fiber injury in wild type mice. The remodeling occurs repetitively through the life of the animal and the changes in junctions become greater with age.
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Affiliation(s)
- Seth G. Haddix
- Texas A&M Institute for Neuroscience, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
| | - Young il Lee
- Texas A&M Institute for Neuroscience, Texas A&M University, College Station, Texas, United States of America
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
| | - Joe N. Kornegay
- Texas A&M Institute for Neuroscience, Texas A&M University, College Station, Texas, United States of America
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, Texas, United States of America
| | - Wesley J. Thompson
- Texas A&M Institute for Neuroscience, Texas A&M University, College Station, Texas, United States of America
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
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28
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Affiliation(s)
- Lei Li
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Wen-Cheng Xiong
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
- Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio 44106, USA
| | - Lin Mei
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
- Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio 44106, USA
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29
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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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30
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Klose A, Liu W, Paris ND, Forman S, Krolewski JJ, Nastiuk KL, Chakkalakal JV. Castration induces satellite cell activation that contributes to skeletal muscle maintenance. JCSM RAPID COMMUNICATIONS 2018; 1:e00040. [PMID: 29782610 PMCID: PMC5959044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
BACKGROUND Sarcopenia, the age-related loss of skeletal muscle, is a side effect of androgen deprivation therapy (ADT) for prostate cancer patients. Resident stem cells of skeletal muscle, satellite cells (SCs), are an essential source of progenitors for the growth and regeneration of skeletal muscle. Decreased androgen signaling and deficits in the number and function of SCs are features of aging. Although androgen signaling is known to regulate skeletal muscle, the cellular basis for ADT-induced exacerbation of sarcopenia is unknown. Furthermore, the consequences of androgen deprivation on SC fate in adult skeletal muscle remain largely unexplored. METHODS We examined SC fate in an androgen-deprived environment using immunofluorescence and fluorescence-activated cell sorting (FACS) with SC-specific markers in young castrated mice. To study the effects of androgen deprivation on SC function and skeletal muscle regenerative capacity, young castrated mice were subjected to experimental regenerative paradigms. SC-derived-cell contributions to skeletal muscle maintenance were examined in castrated Pax7CreER/+; ROSA26mTmG/+ mice. SCs were depleted in Pax7CreER/+; ROSA26DTA/+ mice to ascertain the consequences of SC ablation in sham and castrated skeletal muscles. Confocal immunofluorescence analysis of neuromuscular junctions (NMJs), and assessment of skeletal muscle physiology, contractile properties, and integrity were conducted. RESULTS Castration led to SC activation, however this did not result in a decline in SC function or skeletal muscle regenerative capacity. Surprisingly, castration induced SC-dependent maintenance of young skeletal muscle. The functional dependence of skeletal muscles on SCs in young castrated mice was demonstrated by an increase in SC-derived-cell fusion within skeletal muscle fibers. SC depletion was associated with further atrophy and functional decline, as well as the induction of partial innervation and the loss of NMJ-associated myonuclei in skeletal muscles from castrated mice. CONCLUSION The maintenance of skeletal muscles in young castrated mice relies on the cellular contributions of SCs. Considering the well-described age-related decline in SCs, the results in this study highlight the need to devise strategies that promote SC maintenance and activity to attenuate or reverse the progression of sarcopenia in elderly androgen-deprived individuals.
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Affiliation(s)
- Alanna Klose
- Department of Orthopaedics and Rehabilitation, Center for Musculoskeletal Research, University of Rochester Medical Center, Rochester, NY USA
| | - Wenxuan Liu
- Department of Orthopaedics and Rehabilitation, Center for Musculoskeletal Research, University of Rochester Medical Center, Rochester, NY USA
| | - Nicole D. Paris
- Department of Orthopaedics and Rehabilitation, Center for Musculoskeletal Research, University of Rochester Medical Center, Rochester, NY USA
| | - Sophie Forman
- Department of Orthopaedics and Rehabilitation, Center for Musculoskeletal Research, University of Rochester Medical Center, Rochester, NY USA
| | - John J. Krolewski
- Department of Cancer Genetics & Genomics, and Center for Personalized Medicine, Roswell Park Cancer Institute; Buffalo, NY USA
| | - Kent L. Nastiuk
- Department of Cancer Genetics & Genomics, and Department of Urology, Roswell Park Cancer Institute; Buffalo, NY USA
| | - Joe V. Chakkalakal
- Department of Orthopaedics and Rehabilitation, Center for Musculoskeletal Research, University of Rochester Medical Center, Rochester, NY USA
- Stem Cell and Regenerative Medicine Institute, University of Rochester Medical Center, Rochester, NY USA
- The Rochester Aging Research Center, University of Rochester Medical Center, Rochester, NY USA
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31
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Willadt S, Nash M, Slater C. Age-related changes in the structure and function of mammalian neuromuscular junctions. Ann N Y Acad Sci 2017; 1412:41-53. [PMID: 29291259 DOI: 10.1111/nyas.13521] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 09/07/2017] [Accepted: 09/12/2017] [Indexed: 12/17/2022]
Abstract
As mammals age, their neuromuscular junctions (NMJs) change their form, with an increasingly complex system of axonal branches innervating increasingly fragmented regions of postsynaptic differentiation. It has been suggested that this remodeling is associated with impairment of neuromuscular transmission and that this contributes to age-related muscle weakness in mammals, including humans. Here, we review previous work on NMJ aging, most of which has focused on either structure or function, as well as a new study aimed at seeking correlation between the structure and function of individual NMJs. While it is clear that extensive structural changes occur as part of the aging process, it is much less certain how, if at all, these are correlated with an impairment of function. This leaves open the question of whether loss of NMJ function is a significant cause of age-related muscle weakness.
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Affiliation(s)
- Silvia Willadt
- Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Mark Nash
- Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Clarke Slater
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK
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Liu W, Klose A, Forman S, Paris ND, Wei-LaPierre L, Cortés-Lopéz M, Tan A, Flaherty M, Miura P, Dirksen RT, Chakkalakal JV. Loss of adult skeletal muscle stem cells drives age-related neuromuscular junction degeneration. eLife 2017; 6. [PMID: 28583253 PMCID: PMC5462534 DOI: 10.7554/elife.26464] [Citation(s) in RCA: 109] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 05/20/2017] [Indexed: 01/04/2023] Open
Abstract
Neuromuscular junction degeneration is a prominent aspect of sarcopenia, the age-associated loss of skeletal muscle integrity. Previously, we showed that muscle stem cells activate and contribute to mouse neuromuscular junction regeneration in response to denervation (Liu et al., 2015). Here, we examined gene expression profiles and neuromuscular junction integrity in aged mouse muscles, and unexpectedly found limited denervation despite a high level of degenerated neuromuscular junctions. Instead, degenerated neuromuscular junctions were associated with reduced contribution from muscle stem cells. Indeed, muscle stem cell depletion was sufficient to induce neuromuscular junction degeneration at a younger age. Conversely, prevention of muscle stem cell and derived myonuclei loss was associated with attenuation of age-related neuromuscular junction degeneration, muscle atrophy, and the promotion of aged muscle force generation. Our observations demonstrate that deficiencies in muscle stem cell fate and post-synaptic myogenesis provide a cellular basis for age-related neuromuscular junction degeneration and associated skeletal muscle decline. DOI:http://dx.doi.org/10.7554/eLife.26464.001
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Affiliation(s)
- Wenxuan Liu
- Department of Orthopaedics and Rehabilitation, Center for Musculoskeletal Research, University of Rochester Medical Center, Rochester, United States.,Department of Biomedical Genetics, University of Rochester Medical Center, Rochester, United States
| | - Alanna Klose
- Department of Orthopaedics and Rehabilitation, Center for Musculoskeletal Research, University of Rochester Medical Center, Rochester, United States
| | - Sophie Forman
- Department of Biology, University of Rochester, Rochester, United States
| | - Nicole D Paris
- Department of Orthopaedics and Rehabilitation, Center for Musculoskeletal Research, University of Rochester Medical Center, Rochester, United States
| | - Lan Wei-LaPierre
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, United States
| | | | - Aidi Tan
- Bioinformatics Division and Center for Synthetic and Systems Biology, Tsinghua University, Beijing, China.,TNLIST/Department of Automation, Tsinghua University, Beijing, China
| | - Morgan Flaherty
- Department of Biomedical Genetics, University of Rochester Medical Center, Rochester, United States
| | - Pedro Miura
- Department of Biology, University of Nevada, Reno, United States
| | - Robert T Dirksen
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, United States
| | - Joe V Chakkalakal
- Department of Orthopaedics and Rehabilitation, Center for Musculoskeletal Research, University of Rochester Medical Center, Rochester, United States.,Stem Cell and Regenerative Medicine Institute, University of Rochester Medical Center, Rochester, United States.,The Rochester Aging Research Center, University of Rochester Medical Center, Rochester, United States
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33
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Tu H, Zhang D, Corrick RM, Muelleman RL, Wadman MC, Li YL. Morphological Regeneration and Functional Recovery of Neuromuscular Junctions after Tourniquet-Induced Injuries in Mouse Hindlimb. Front Physiol 2017; 8:207. [PMID: 28428759 PMCID: PMC5382216 DOI: 10.3389/fphys.2017.00207] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 03/21/2017] [Indexed: 02/04/2023] Open
Abstract
Tourniquet application and its subsequent release cause serious injuries to the skeletal muscle, nerve, and neuromuscular junction (NMJ) due to mechanical compression and ischemia-reperfusion (IR). Monitoring structural and functional repair of the NMJ, nerve, and skeletal muscle after tourniquet-induced injuries is beneficial in exploring potential cellular and molecular mechanisms responsible for tourniquet-induced injuries, and for establishing effective therapeutic interventions. Here, we observed long-term morphological and functional changes of the NMJ in a murine model of tourniquet-induced hindlimb injuries. Unilateral hindlimbs of C57/BL6 mice were subjected to 3 h of tourniquet by placing an orthodontic rubber band, followed by varied periods of tourniquet release (1 day, 3 days, 1 week, 2 weeks, 4 weeks, and 6 weeks). NMJ morphology in the gastrocnemius muscle was imaged, and the endplate potential (EPP) was recorded to evaluate NMJ function. In NMJs, nicotinic acetylcholine receptor (nAChR) clusters normally displayed an intact, pretzel-like shape, and all nAChR clusters were innervated (100%) by motor nerve terminals. During 3 h of tourniquet application and varied periods of tourniquet release, NMJs in the gastrocnemius muscle were characterized by morphological and functional changes. At 1 day and 3 days of tourniquet release, nAChR clusters retained normal, pretzel-like shapes, whereas motor nerve terminals were completely destroyed and no EPPs recorded. From 1 to 6 weeks of tourniquet release, motor nerve terminals gradually regenerated, even reaching that seen in sham mice, whereas nAChR clusters were gradually fragmented with prolongation of tourniquet release. Additionally, the amplitude of EPPs gradually increased with prolongation of tourniquet release. However, even at 6 weeks after tourniquet release, the amplitude of EPPs did not restore to the level seen in sham mice (13.9 ± 1.1 mV, p < 0.05 vs. sham mice, 29.8 ± 1.0 mV). The data suggest that tourniquet application and subsequent release impair the structure and function of NMJs. Morphological change in motor nerve terminals is faster than in nAChR clusters in NMJs. Slow restoration of fragmented nAChR clusters possibly dampens neuromuscular transmission during the long phase following tourniquet release.
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Affiliation(s)
- Huiyin Tu
- Department of Emergency Medicine, University of Nebraska Medical CenterOmaha, NE, USA
| | - Dongze Zhang
- Department of Emergency Medicine, University of Nebraska Medical CenterOmaha, NE, USA
| | - Ryan M Corrick
- Department of Emergency Medicine, University of Nebraska Medical CenterOmaha, NE, USA
| | - Robert L Muelleman
- Department of Emergency Medicine, University of Nebraska Medical CenterOmaha, NE, USA
| | - Michael C Wadman
- Department of Emergency Medicine, University of Nebraska Medical CenterOmaha, NE, USA
| | - Yu-Long Li
- Department of Emergency Medicine, University of Nebraska Medical CenterOmaha, NE, USA.,Department of Cellular and Integrative Physiology, Nebraska Medical CenterOmaha, NE, USA
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Anderson JE, Do MKQ, Daneshvar N, Suzuki T, Dort J, Mizunoya W, Tatsumi R. The role of semaphorin3A in myogenic regeneration and the formation of functional neuromuscular junctions on new fibres. Biol Rev Camb Philos Soc 2016; 92:1389-1405. [PMID: 27296513 DOI: 10.1111/brv.12286] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 05/10/2016] [Accepted: 05/16/2016] [Indexed: 01/03/2023]
Abstract
Current research on skeletal muscle injury and regeneration highlights the crucial role of nerve-muscle interaction in the restoration of innervation during that process. Activities of muscle satellite or stem cells, recognized as the 'currency' of myogenic repair, have a pivotal role in these events, as shown by ongoing research. More recent investigation of myogenic signalling events reveals intriguing roles for semaphorin3A (Sema3A), secreted by activated satellite cells, in the muscle environment during development and regeneration. For example, Sema3A makes important contributions to regulating the formation of blood vessels, balancing bone formation and bone remodelling, and inflammation, and was recently implicated in the establishment of fibre-type distribution through effects on myosin heavy chain gene expression. This review highlights the active or potential contributions of satellite-cell-derived Sema3A to regulation of the processes of motor neurite ingrowth into a regenerating muscle bed. Successful restoration of functional innervation during muscle repair is essential; this review emphasizes the integrative role of satellite-cell biology in the progressive coordination of adaptive cellular and tissue responses during the injury-repair process in voluntary muscle.
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Affiliation(s)
- Judy E Anderson
- Department of Biological Sciences, Faculty of Science, University of Manitoba, Winnipeg, R3T 2N2, Canada
| | - Mai-Khoi Q Do
- Department of Animal and Marine Bioresource Sciences, Graduate School of Agriculture, Kyushu University, Higashi-ku Fukuoka, 8128581, Japan
| | - Nasibeh Daneshvar
- Department of Biological Sciences, Faculty of Science, University of Manitoba, Winnipeg, R3T 2N2, Canada
| | - Takahiro Suzuki
- Department of Animal and Marine Bioresource Sciences, Graduate School of Agriculture, Kyushu University, Higashi-ku Fukuoka, 8128581, Japan
| | - Junio Dort
- Department of Biological Sciences, Faculty of Science, University of Manitoba, Winnipeg, R3T 2N2, Canada
| | - Wataru Mizunoya
- Department of Animal and Marine Bioresource Sciences, Graduate School of Agriculture, Kyushu University, Higashi-ku Fukuoka, 8128581, Japan
| | - Ryuichi Tatsumi
- Department of Animal and Marine Bioresource Sciences, Graduate School of Agriculture, Kyushu University, Higashi-ku Fukuoka, 8128581, Japan
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van der Pijl EM, van Putten M, Niks EH, Verschuuren JJGM, Aartsma-Rus A, Plomp JJ. Characterization of neuromuscular synapse function abnormalities in multiple Duchenne muscular dystrophy mouse models. Eur J Neurosci 2016; 43:1623-35. [PMID: 27037492 DOI: 10.1111/ejn.13249] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 03/22/2016] [Accepted: 03/23/2016] [Indexed: 11/30/2022]
Abstract
Duchenne muscular dystrophy (DMD) is an X-linked myopathy caused by dystrophin deficiency. Dystrophin is present intracellularly at the sarcolemma, connecting actin to the dystrophin-associated glycoprotein complex. Interestingly, it is enriched postsynaptically at the neuromuscular junction (NMJ), but its synaptic function is largely unknown. Utrophin, a dystrophin homologue, is also concentrated at the NMJ, and upregulated in DMD. It is possible that the absence of dystrophin at NMJs in DMD causes neuromuscular transmission defects that aggravate muscle weakness. We studied NMJ function in mdx mice (lacking dystrophin) and wild type mice. In addition, mdx/utrn(+/-) and mdx/utrn(-/-) mice (lacking utrophin) were used to investigate influences of utrophin levels. The three Duchenne mouse models showed muscle weakness when comparatively tested in vivo, with mdx/utrn(-/-) mice being weakest. Ex vivo muscle contraction and electrophysiological studies showed a reduced safety factor of neuromuscular transmission in all models. NMJs had ~ 40% smaller miniature endplate potential amplitudes compared with wild type, indicating postsynaptic sensitivity loss for the neurotransmitter acetylcholine. However, nerve stimulation-evoked endplate potential amplitudes were unchanged. Consequently, quantal content (i.e. the number of acetylcholine quanta released per nerve impulse) was considerably increased. Such a homeostatic compensatory increase in neurotransmitter release is also found at NMJs in myasthenia gravis, where autoantibodies reduce acetylcholine receptors. However, high-rate nerve stimulation induced exaggerated endplate potential rundown. Study of NMJ morphology showed that fragmentation of acetylcholine receptor clusters occurred in all models, being most severe in mdx/utrn(-/-) mice. Overall, we showed mild 'myasthenia-like' neuromuscular synaptic dysfunction in several Duchenne mouse models, which possibly affects muscle weakness and degeneration.
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Affiliation(s)
- Elizabeth M van der Pijl
- Department of Neurology, Leiden University Medical Centre, Research Building S5-P, P.O. Box 9600 2300 RC, Leiden, The Netherlands
| | - Maaike van Putten
- Department of Human Genetics, Leiden University Medical Centre, Leiden, The Netherlands
| | - Erik H Niks
- Department of Neurology, Leiden University Medical Centre, Research Building S5-P, P.O. Box 9600 2300 RC, Leiden, The Netherlands
| | - Jan J G M Verschuuren
- Department of Neurology, Leiden University Medical Centre, Research Building S5-P, P.O. Box 9600 2300 RC, Leiden, The Netherlands
| | - Annemieke Aartsma-Rus
- Department of Human Genetics, Leiden University Medical Centre, Leiden, The Netherlands
| | - Jaap J Plomp
- Department of Neurology, Leiden University Medical Centre, Research Building S5-P, P.O. Box 9600 2300 RC, Leiden, The Netherlands
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Willadt S, Nash M, Slater CR. Age-related fragmentation of the motor endplate is not associated with impaired neuromuscular transmission in the mouse diaphragm. Sci Rep 2016; 6:24849. [PMID: 27094316 PMCID: PMC4837408 DOI: 10.1038/srep24849] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Accepted: 04/05/2016] [Indexed: 02/04/2023] Open
Abstract
As mammals age, their neuromuscular junctions (NMJs) gradually change their form, acquiring an increasingly fragmented appearance consisting of numerous isolated regions of synaptic differentiation. It has been suggested that this remodelling is associated with impairment of neuromuscular transmission, and that this contributes to age-related muscle weakness in mammals, including humans. The underlying hypothesis, that increasing NMJ fragmentation is associated with impaired transmission, has never been directly tested. Here, by comparing the structure and function of individual NMJs, we show that neuromuscular transmission at the most highly fragmented NMJs in the diaphragms of old (26-28 months) mice is, if anything, stronger than in middle-aged (12-14 months) mice. We suggest that NMJ fragmentation per se is not a reliable indicator of impaired neuromuscular transmission.
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Affiliation(s)
- Silvia Willadt
- Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Mark Nash
- Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Clarke R. Slater
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
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Neuregulin1 displayed on motor axons regulates terminal Schwann cell-mediated synapse elimination at developing neuromuscular junctions. Proc Natl Acad Sci U S A 2016; 113:E479-87. [PMID: 26755586 DOI: 10.1073/pnas.1519156113] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Synaptic connections in the nervous system are rearranged during development and in adulthood as a feature of growth, plasticity, aging, and disease. Glia are implicated as active participants in these changes. Here we investigated a signal that controls the participation of peripheral glia, the terminal Schwann cells (SCs), at the neuromuscular junction (NMJ) in mice. Transgenic manipulation of the levels of membrane-tethered neuregulin1 (NRG1-III), a potent activator of SCs normally presented on motor axons, alters the rate of loss of motor inputs at NMJs during developmental synapse elimination. In addition, NMJs of adult transgenic mice that expressed excess axonal NRG1-III exhibited continued remodeling, in contrast to the more stable morphologies of controls. In fact, synaptic SCs of these adult mice with NRG1-III overexpression exhibited behaviors evident in wild type neonates during synapse elimination, including an affinity for the postsynaptic myofiber surface and phagocytosis of nerve terminals. Given that levels of NRG1-III expression normally peak during the period of synapse elimination, our findings identify axon-tethered NRG1 as a molecular determinant for SC-driven neuromuscular synaptic plasticity.
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Schwann Cell and Axon: An Interlaced Unit—From Action Potential to Phenotype Expression. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 949:183-201. [DOI: 10.1007/978-3-319-40764-7_9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Gorski JP, Huffman NT, Vallejo J, Brotto L, Chittur SV, Breggia A, Stern A, Huang J, Mo C, Seidah NG, Bonewald L, Brotto M. Deletion of Mbtps1 (Pcsk8, S1p, Ski-1) Gene in Osteocytes Stimulates Soleus Muscle Regeneration and Increased Size and Contractile Force with Age. J Biol Chem 2015; 291:4308-22. [PMID: 26719336 DOI: 10.1074/jbc.m115.686626] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Indexed: 12/28/2022] Open
Abstract
Conditional deletion of Mbtps1 (cKO) protease in bone osteocytes leads to an age-related increase in mass (12%) and in contractile force (30%) in adult slow twitch soleus muscles (SOL) with no effect on fast twitch extensor digitorum longus muscles. Surprisingly, bone from 10-12-month-old cKO animals was indistinguishable from controls in size, density, and morphology except for a 25% increase in stiffness. cKO SOL exhibited increased expression of Pax7, Myog, Myod1, Notch, and Myh3 and 6-fold more centralized nuclei, characteristics of postnatal regenerating muscle, but only in type I myosin heavy chain-expressing cells. Increased expression of gene pathways mediating EGF receptor signaling, circadian exercise, striated muscle contraction, and lipid and carbohydrate oxidative metabolism were also observed in cKO SOL. This muscle phenotype was not observed in 3-month-old mice. Although Mbtps1 mRNA and protein expression was reduced in cKO bone osteocytes, no differences in Mbtps1 or cre recombinase expression were observed in cKO SOL, explaining this age-related phenotype. Understanding bone-muscle cross-talk may provide a fresh and novel approach to prevention and treatment of age-related muscle loss.
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Affiliation(s)
- Jeff P Gorski
- From the Department of Oral and Craniofacial Sciences, University of Missouri-Kansas City Center of Excellence in the Study of Dental and Musculoskeletal Tissues, School of Dentistry,
| | - Nichole T Huffman
- From the Department of Oral and Craniofacial Sciences, University of Missouri-Kansas City Center of Excellence in the Study of Dental and Musculoskeletal Tissues, School of Dentistry
| | - Julian Vallejo
- Muscle Biology Research Group, School of Nursing and Health Studies, and
| | - Leticia Brotto
- Muscle Biology Research Group, School of Nursing and Health Studies, and
| | - Sridar V Chittur
- Center for Functional Genomics, University at Albany, Rensselaer, New York 12144
| | | | - Amber Stern
- School of Computing and Engineering, University of Missouri-Kansas City, Kansas City, Missouri 64108, Engineering Systems, Inc., Charlotte, North Carolina 28277, and
| | - Jian Huang
- Muscle Biology Research Group, School of Nursing and Health Studies, and
| | - Chenglin Mo
- Muscle Biology Research Group, School of Nursing and Health Studies, and
| | - Nabil G Seidah
- Institut de Recherches Cliniques Montreal, Montreal, Quebec H2W IR7, Canada
| | - Lynda Bonewald
- From the Department of Oral and Craniofacial Sciences, University of Missouri-Kansas City Center of Excellence in the Study of Dental and Musculoskeletal Tissues, School of Dentistry
| | - Marco Brotto
- Muscle Biology Research Group, School of Nursing and Health Studies, and
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Ko CP, Robitaille R. Perisynaptic Schwann Cells at the Neuromuscular Synapse: Adaptable, Multitasking Glial Cells. Cold Spring Harb Perspect Biol 2015; 7:a020503. [PMID: 26430218 PMCID: PMC4588062 DOI: 10.1101/cshperspect.a020503] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The neuromuscular junction (NMJ) is engineered to be a highly reliable synapse to carry the control of the motor commands of the nervous system over the muscles. Its development, organization, and synaptic properties are highly structured and regulated to support such reliability and efficacy. Yet, the NMJ is also highly plastic, able to react to injury and adapt to changes. This balance between structural stability and synaptic efficacy on one hand and structural plasticity and repair on another hand is made possible by the intricate regulation of perisynaptic Schwann cells, glial cells at this synapse. They regulate both the efficacy and structural plasticity of the NMJ in a dynamic, bidirectional manner owing to their ability to decode synaptic transmission and by their interactions via trophic-related factors.
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Affiliation(s)
- Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520
| | - Richard Robitaille
- Département de Neurosciences, Université de Montréal, Montréal, Québec H3C 3J7, Canada Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec H3C 3J7, Canada
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41
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Wong SP, Rowley JE, Redpath AN, Tilman JD, Fellous TG, Johnson JR. Pericytes, mesenchymal stem cells and their contributions to tissue repair. Pharmacol Ther 2015; 151:107-20. [PMID: 25827580 DOI: 10.1016/j.pharmthera.2015.03.006] [Citation(s) in RCA: 128] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2014] [Accepted: 03/18/2015] [Indexed: 12/13/2022]
Abstract
Regenerative medicine using mesenchymal stem cells for the purposes of tissue repair has garnered considerable public attention due to the potential of returning tissues and organs to a normal, healthy state after injury or damage has occurred. To achieve this, progenitor cells such as pericytes and bone marrow-derived mesenchymal stem cells can be delivered exogenously, mobilised and recruited from within the body or transplanted in the form organs and tissues grown in the laboratory from stem cells. In this review, we summarise the recent evidence supporting the use of endogenously mobilised stem cell populations to enhance tissue repair along with the use of mesenchymal stem cells and pericytes in the development of engineered tissues. Finally, we conclude with an overview of currently available therapeutic options to manipulate endogenous stem cells to promote tissue repair.
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Affiliation(s)
- Suet-Ping Wong
- National Heart and Lung Institute, Imperial College London, United Kingdom
| | - Jessica E Rowley
- National Heart and Lung Institute, Imperial College London, United Kingdom
| | - Andia N Redpath
- National Heart and Lung Institute, Imperial College London, United Kingdom
| | - Jessica D Tilman
- National Heart and Lung Institute, Imperial College London, United Kingdom
| | - Tariq G Fellous
- National Heart and Lung Institute, Imperial College London, United Kingdom
| | - Jill R Johnson
- National Heart and Lung Institute, Imperial College London, United Kingdom
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42
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Marshall JL, Oh J, Chou E, Lee JA, Holmberg J, Burkin DJ, Crosbie-Watson RH. Sarcospan integration into laminin-binding adhesion complexes that ameliorate muscular dystrophy requires utrophin and α7 integrin. Hum Mol Genet 2014; 24:2011-22. [PMID: 25504048 DOI: 10.1093/hmg/ddu615] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is caused by mutations in the dystrophin gene that result in loss of the dystrophin-glycoprotein complex, a laminin receptor that connects the myofiber to its surrounding extracellular matrix. Utrophin, a dystrophin ortholog that is normally localized to the neuromuscular junction, is naturally upregulated in DMD muscle, which partially compensates for the loss of dystrophin. Transgenic overexpression of utrophin causes broad sarcolemma localization of utrophin, restoration of laminin binding and amelioration of disease in the mdx mouse model of DMD. We previously demonstrated that overexpression of sarcospan, a dystrophin- and utrophin-binding protein, ameliorates mdx muscular dystrophy. Sarcospan boosts levels of utrophin to therapeutic levels at the sarcolemma, where attachment to laminin is restored. However, understanding the compensatory mechanism is complicated by concomitant upregulation of α7β1 integrin, which also binds laminin. Similar to the effects of utrophin, transgenic overexpression of α7 integrin prevents DMD disease in mice and is accompanied by increased abundance of utrophin around the extra-synaptic sarcolemma. In order to investigate the mechanisms underlying sarcospan 'rescue' of muscular dystrophy, we created double-knockout mice to test the contributions of utrophin or α7 integrin. We show that sarcospan-mediated amelioration of muscular dystrophy in DMD mice is dependent on the presence of both utrophin and α7β1 integrin, even when they are individually expressed at therapeutic levels. Furthermore, we found that association of sarcospan into laminin-binding complexes is dependent on utrophin and α7β1 integrin.
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Affiliation(s)
- Jamie L Marshall
- Department of Integrative Biology and Physiology, Center for Duchenne Muscular Dystrophy
| | - Jennifer Oh
- Department of Integrative Biology and Physiology, Center for Duchenne Muscular Dystrophy
| | - Eric Chou
- Department of Integrative Biology and Physiology, Center for Duchenne Muscular Dystrophy
| | - Joy A Lee
- Department of Integrative Biology and Physiology, Center for Duchenne Muscular Dystrophy
| | - Johan Holmberg
- Department of Integrative Biology and Physiology, Center for Duchenne Muscular Dystrophy
| | - Dean J Burkin
- Department of Pharmacology, Center for Molecular Medicine, University of Nevada School of Medicine, Reno, NV 89557, USA
| | - Rachelle H Crosbie-Watson
- Department of Integrative Biology and Physiology, Center for Duchenne Muscular Dystrophy, Molecular Biology Institute, Department of Neurology, University of California, Los Angeles, CA 90095, USA and
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43
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Birbrair A, Zhang T, Wang ZM, Messi ML, Mintz A, Delbono O. Pericytes: multitasking cells in the regeneration of injured, diseased, and aged skeletal muscle. Front Aging Neurosci 2014; 6:245. [PMID: 25278877 PMCID: PMC4166895 DOI: 10.3389/fnagi.2014.00245] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 08/29/2014] [Indexed: 12/16/2022] Open
Abstract
Pericytes are perivascular cells that envelop and make intimate connections with adjacent capillary endothelial cells. Recent studies show that they may have a profound impact in skeletal muscle regeneration, innervation, vessel formation, fibrosis, fat accumulation, and ectopic bone formation throughout life. In this review, we summarize and evaluate recent advances in our understanding of pericytes' influence on adult skeletal muscle pathophysiology. We also discuss how further elucidating their biology may offer new approaches to the treatment of conditions characterized by muscle wasting.
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Affiliation(s)
- Alexander Birbrair
- Department of Internal Medicine-Gerontology, Wake Forest School of Medicine Winston-Salem, NC, USA ; Neuroscience Program, Wake Forest School of Medicine Winston-Salem, NC, USA
| | - Tan Zhang
- Department of Internal Medicine-Gerontology, Wake Forest School of Medicine Winston-Salem, NC, USA
| | - Zhong-Min Wang
- Department of Internal Medicine-Gerontology, Wake Forest School of Medicine Winston-Salem, NC, USA
| | - Maria L Messi
- Department of Internal Medicine-Gerontology, Wake Forest School of Medicine Winston-Salem, NC, USA
| | - Akiva Mintz
- Department of Neurosurgery, Wake Forest School of Medicine Winston-Salem, NC, USA
| | - Osvaldo Delbono
- Department of Internal Medicine-Gerontology, Wake Forest School of Medicine Winston-Salem, NC, USA ; Neuroscience Program, Wake Forest School of Medicine Winston-Salem, NC, USA
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44
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Falk DJ, Todd AG, Lee S, Soustek MS, ElMallah MK, Fuller DD, Notterpek L, Byrne BJ. Peripheral nerve and neuromuscular junction pathology in Pompe disease. Hum Mol Genet 2014; 24:625-36. [PMID: 25217571 DOI: 10.1093/hmg/ddu476] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Pompe disease is a systemic metabolic disorder characterized by lack of acid-alpha glucosidase (GAA) resulting in ubiquitous lysosomal glycogen accumulation. Respiratory and ambulatory dysfunction are prominent features in patients with Pompe yet the mechanism defining the development of muscle weakness is currently unclear. Transgenic animal models of Pompe disease mirroring the patient phenotype have been invaluable in mechanistic and therapeutic study. Here, we demonstrate significant pathological alterations at neuromuscular junctions (NMJs) of the diaphragm and tibialis anterior muscle as prominent features of disease pathology in Gaa knockout mice. Postsynaptic defects including increased motor endplate area and fragmentation were readily observed in Gaa(-/-) but not wild-type mice. Presynaptic neuropathic changes were also evident, as demonstrated by significant reduction in the levels of neurofilament proteins, and alterations in axonal fiber diameter and myelin thickness within the sciatic and phrenic nerves. Our data suggest the loss of NMJ integrity is a primary contributor to the decline in respiratory and ambulatory function in Pompe and arises from both pre- and postsynaptic pathology. These observations highlight the importance of systemic phenotype correction, specifically restoration of GAA to skeletal muscle and the nervous system for treatment of Pompe disease.
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Affiliation(s)
- Darin J Falk
- Department of Pediatrics Powell Gene Therapy Center
| | | | | | | | | | - David D Fuller
- Department of Physical Therapy, University of Florida, Gainesville, FL 32610, USA
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45
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Cellular players in skeletal muscle regeneration. BIOMED RESEARCH INTERNATIONAL 2014; 2014:957014. [PMID: 24779022 PMCID: PMC3980925 DOI: 10.1155/2014/957014] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2013] [Revised: 01/12/2014] [Accepted: 01/28/2014] [Indexed: 12/12/2022]
Abstract
Skeletal muscle, a tissue endowed with remarkable endogenous regeneration potential, is still under focused experimental investigation mainly due to treatment potential for muscle trauma and muscular dystrophies. Resident satellite cells with stem cell features were enthusiastically described quite a long time ago, but activation of these cells is not yet controlled by any medical interventions. However, after thorough reports of their existence, survival, activation, and differentiation there are still many questions to be answered regarding the intimate mechanism of tissue regeneration. This review delivers an up-to-date inventory of the main known key players in skeletal muscle repair, revealed by various models of tissue injuries in mechanical trauma, toxic lesions, and muscular dystrophy. A better understanding of the spatial and temporal relationships between various cell populations, with different physical or paracrine interactions and phenotype changes induced by local or systemic signalling, might lead to a more efficient approach for future therapies.
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46
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Nishimune H, Stanford JA, Mori Y. Role of exercise in maintaining the integrity of the neuromuscular junction. Muscle Nerve 2013; 49:315-24. [PMID: 24122772 DOI: 10.1002/mus.24095] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/06/2013] [Indexed: 01/16/2023]
Abstract
Physical activity plays an important role in preventing chronic disease in adults and the elderly. Exercise has beneficial effects on the nervous system, including at the neuromuscular junction (NMJ). Exercise causes hypertrophy of NMJs and improves recovery from peripheral nerve injuries, whereas decreased physical activity causes degenerative changes in NMJs. Recent studies have begun to elucidate molecular mechanisms underlying the beneficial effects of exercise. These mechanisms involve Bassoon, neuregulin-1, peroxisome proliferator-activated receptor gamma coactivator 1α, insulin-like growth factor-1, glial cell line-derived neurotrophic factor, neurotrophin 4, Homer, and nuclear factor of activated T cells c1. For example, NMJ denervation and active zone decreases have been observed in aged NMJs, but these age-dependent degenerative changes can be ameliorated by exercise. In this review we assess the effects of exercise on the maintenance and regeneration of NMJs and highlight recent insights into the molecular mechanisms underlying these exercise effects.
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Affiliation(s)
- Hiroshi Nishimune
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, 3901 Rainbow Boulevard, MS 3051, HLSIC Room 2073, Kansas City, Kansas, 66160, USA
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Sahashi K, Ling KKY, Hua Y, Wilkinson JE, Nomakuchi T, Rigo F, Hung G, Xu D, Jiang YP, Lin RZ, Ko CP, Bennett CF, Krainer AR. Pathological impact of SMN2 mis-splicing in adult SMA mice. EMBO Mol Med 2013; 5:1586-601. [PMID: 24014320 PMCID: PMC3799581 DOI: 10.1002/emmm.201302567] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 08/06/2013] [Accepted: 08/09/2013] [Indexed: 12/18/2022] Open
Abstract
Loss-of-function mutations in SMN1 cause spinal muscular atrophy (SMA), a leading genetic cause of infant mortality. The related SMN2 gene expresses suboptimal levels of functional SMN protein, due to a splicing defect. Many SMA patients reach adulthood, and there is also adult-onset (type IV) SMA. There is currently no animal model for adult-onset SMA, and the tissue-specific pathogenesis of post-developmental SMN deficiency remains elusive. Here, we use an antisense oligonucleotide (ASO) to exacerbate SMN2 mis-splicing. Intracerebroventricular ASO injection in adult SMN2-transgenic mice phenocopies key aspects of adult-onset SMA, including delayed-onset motor dysfunction and relevant histopathological features. SMN2 mis-splicing increases during late-stage disease, likely accelerating disease progression. Systemic ASO injection in adult mice causes peripheral SMN2 mis-splicing and affects prognosis, eliciting marked liver and heart pathologies, with decreased IGF1 levels. ASO dose–response and time-course studies suggest that only moderate SMN levels are required in the adult central nervous system, and treatment with a splicing-correcting ASO shows a broad therapeutic time window. We describe distinctive pathological features of adult-onset and early-onset SMA.
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48
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Punga AR, Ruegg MA. Signaling and aging at the neuromuscular synapse: lessons learnt from neuromuscular diseases. Curr Opin Pharmacol 2012; 12:340-6. [PMID: 22365504 DOI: 10.1016/j.coph.2012.02.002] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 01/26/2012] [Accepted: 02/02/2012] [Indexed: 12/30/2022]
Abstract
The neuromuscular junction (NMJ) is a specialized synapse between motor neurons and skeletal muscle with a complex signaling network that assures highly reliable neuromuscular transmission. Diseases of the NMJ cause skeletal muscle fatigue and include inherited and acquired disorders that affect presynaptic, intrasynaptic or postsynaptic components. Moreover, fragmentation of the NMJ contributes to sarcopenia, the loss of muscle mass during aging. Studies from recent years indicate that the formation and stabilization of NMJs differs between various muscles and that this difference affects their response under pathological conditions. This review summarizes the most important mechanisms involved in the development, maintenance and dysfunction of the NMJ and it discusses their significance in myasthenic disorders and aging and as targets for possible future treatment of NMJ dysfunction.
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Affiliation(s)
- Anna Rostedt Punga
- Institute of Neuroscience, Department of Clinical Neurophysiology, Uppsala University Hospital, Uppsala, Sweden
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49
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Changes in aging mouse neuromuscular junctions are explained by degeneration and regeneration of muscle fiber segments at the synapse. J Neurosci 2011; 31:14910-9. [PMID: 22016524 DOI: 10.1523/jneurosci.3590-11.2011] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Vertebrate neuromuscular junctions are highly stable synapses, retaining the morphology they achieve in early postnatal development throughout most of life. However, these synapses undergo dramatic change during aging. The acetylcholine receptors (AChRs) change from smooth gutters into fragmented islands, and the nerve terminals change similarly to be varicosities apposed to these islands. These changes have been attributed to a slow deterioration in mechanisms maintaining the synapse. We have used repeated, vital imaging to investigate how these changes occur in the sternomastoid muscle of aging mice. We have found, contrary to expectation, that individual junctions change infrequently, but change, when it occurs, is sudden and dramatic. The change mimics that reported previously for cases in which muscle fibers are deliberately damaged: most of the AChRs present disappear rapidly and are replaced by a new set of receptors that become fragmented. The fiber segment underneath the synapse has centrally located nuclei, showing that this segment has undergone necrosis, quickly regenerated, and been reinnervated with an altered synapse. We show that necrotic events are common in aged muscle and have likely been missed previously as a cause of the alterations in aging because central nuclei are a transient phenomenon and the necrotic events at the junction infrequent. However, the changes are permanent and accumulate over time. Interventions to reduce the neuromuscular changes during aging should likely focus on making muscle fibers resistant to injury.
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