1
|
Schellino R, Boido M, Vrijbloed JW, Fariello RG, Vercelli A. Synergistically Acting on Myostatin and Agrin Pathways Increases Neuromuscular Junction Stability and Endurance in Old Mice. Aging Dis 2024; 15:893-910. [PMID: 37548943 PMCID: PMC10917542 DOI: 10.14336/ad.2023.0713-1] [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: 04/08/2023] [Accepted: 07/13/2023] [Indexed: 08/08/2023] Open
Abstract
Sarcopenia is the primary cause of impaired motor performance in the elderly. The current prevailing approach to counteract such condition is increasing the muscle mass through inhibition of the myostatin system: however, this strategy only moderately improves muscular strength, not being able to sustain the innervation of the hypertrophic muscle per se, leading to a progressive worsening of motor performances. Thus, we proposed the administration of ActR-Fc-nLG3, a protein that combines the soluble activin receptor, a strong myostatin inhibitor, with the C-terminal agrin nLG3 domain. This compound has the potential of reinforcing neuro-muscular stability to the hypertrophic muscle. We previously demonstrated an enhancement of motor endurance and ACh receptor aggregation in young mice after ActR-Fc-nLG3 administration. Now we extended these observations by demonstrating that also in aged (2 years-old) mice, long-term administration of ActR-Fc-nLG3 increases in a sustained way both motor endurance and muscle strength, compared with ActR-Fc, a myostatin inhibitor, alone. Histological data demonstrate that the administration of this biological improves neuromuscular stability and fiber innervation maintenance, preventing muscle fiber atrophy and inducing only moderate hypertrophy. Moreover, at the postsynaptic site we observe an increased folding in the soleplate, a likely anatomical substrate for improved neurotransmission efficiency in the NMJ, that may lead to enhanced motor endurance. We suggest that ActR-Fc-nLG3 may become a valid option for treating sarcopenia and possibly other disorders of striatal muscles.
Collapse
Affiliation(s)
- Roberta Schellino
- Department of Neuroscience Rita Levi-Montalcini, University of Turin, Turin 10126, Italy
- Neuroscience Institute Cavalieri Ottolenghi, University of Turin, Orbassano, 10043 Italy
| | - Marina Boido
- Department of Neuroscience Rita Levi-Montalcini, University of Turin, Turin 10126, Italy
- Neuroscience Institute Cavalieri Ottolenghi, University of Turin, Orbassano, 10043 Italy
| | | | | | - Alessandro Vercelli
- Department of Neuroscience Rita Levi-Montalcini, University of Turin, Turin 10126, Italy
- Neuroscience Institute Cavalieri Ottolenghi, University of Turin, Orbassano, 10043 Italy
| |
Collapse
|
2
|
Gessler L, Huraskin D, Jian Y, Eiber N, Hu Z, Prószyński T, Hashemolhosseini S. The YAP1/TAZ-TEAD transcriptional network regulates gene expression at neuromuscular junctions in skeletal muscle fibers. Nucleic Acids Res 2024; 52:600-624. [PMID: 38048326 PMCID: PMC10810223 DOI: 10.1093/nar/gkad1124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 11/06/2023] [Accepted: 11/09/2023] [Indexed: 12/06/2023] Open
Abstract
We examined YAP1/TAZ-TEAD signaling pathway activity at neuromuscular junctions (NMJs) of skeletal muscle fibers in adult mice. Our investigations revealed that muscle-specific knockouts of Yap1 or Taz, or both, demonstrate that these transcriptional coactivators regulate synaptic gene expression, the number and morphology of NMJs, and synaptic nuclei. Yap1 or Taz single knockout mice display reduced grip strength, fragmentation of NMJs, and accumulation of synaptic nuclei. Yap1/Taz muscle-specific double knockout mice do not survive beyond birth and possess almost no NMJs, the few detectable show severely impaired morphology and are organized in widened endplate bands; and with motor nerve endings being mostly absent. Myogenic gene expression is significantly impaired in the denervated muscles of knockout mice. We found that Tead1 and Tead4 transcription rates were increased upon incubation of control primary myotubes with AGRN-conditioned medium. Reduced AGRN-dependent acetylcholine receptor clustering and synaptic gene transcription were observed in differentiated primary Tead1 and Tead4 knockout myotubes. In silico analysis of previously reported genomic occupancy sites of TEAD1/4 revealed evolutionary conserved regions of potential TEAD binding motifs in key synaptic genes, the relevance of which was functionally confirmed by reporter assays. Collectively, our data suggest a role for YAP1/TAZ-TEAD1/TEAD4 signaling, particularly through TAZ-TEAD4, in regulating synaptic gene expression and acetylcholine receptor clustering at NMJs.
Collapse
Affiliation(s)
- Lea Gessler
- Institute of Biochemistry, Medical Faculty, Friedrich-Alexander-University of Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Danyil Huraskin
- Institute of Biochemistry, Medical Faculty, Friedrich-Alexander-University of Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Yongzhi Jian
- Institute of Biochemistry, Medical Faculty, Friedrich-Alexander-University of Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Nane Eiber
- Institute of Biochemistry, Medical Faculty, Friedrich-Alexander-University of Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Zhaoyong Hu
- Nephrology Division, Department of Medicine, Baylor College of Medicine, Houston, TX, USA
| | - Tomasz J Prószyński
- Łukasiewicz Research Network-PORT Polish Center for Technology Development, Wrocław, Poland
| | - Said Hashemolhosseini
- Institute of Biochemistry, Medical Faculty, Friedrich-Alexander-University of Erlangen-Nürnberg, 91054 Erlangen, Germany
- Muscle Research Center, Friedrich-Alexander-University of Erlangen-Nürnberg, 91054 Erlangen, Germany
| |
Collapse
|
3
|
Yamaguchi T, Kouzaki K, Sasaki K, Nakazato K. Alterations in neuromuscular junction morphology with ageing and endurance training modulate neuromuscular transmission and myofibre composition. J Physiol 2024. [PMID: 38173183 DOI: 10.1113/jp285143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Accepted: 12/12/2023] [Indexed: 01/05/2024] Open
Abstract
Both ageing and exercise training affect the neuromuscular junction (NMJ) structure. Morphological alterations in the NMJ have been considered to influence neuromuscular transmission and myofibre properties, but the direct link between the morphology and function has yet to be established. We measured the neuromuscular transmission, myofibre composition and NMJ structure of 5-month-old (young) and 24-month-old untrained (aged control) and trained (aged trained) mice. Aged trained mice were subjected to 2 months of endurance training before the measurement. Neuromuscular transmission was evaluated in vivo as the ratio of ankle plantar flexion torque evoked by the sciatic nerve stimulation to that by direct muscle stimulation. The torque ratio was significantly lower in aged mice than in young and aged trained mice at high-frequency stimulations, showing a significant positive correlation with voluntary grip strength. The degree of pre- to post-synaptic overlap of the NMJ was also significantly lower in aged mice and positively correlated with the torque ratio. We also found that the proportion of fast-twitch fibres in the soleus muscle decreased with age, and that age-related denervation occurred preferentially in fast-twitch fibres. Age-related denervation and a shift in myofibre composition were partially prevented by endurance training. These results suggest that age-related deterioration of the NMJ structure impairs neuromuscular transmission and alters myofibre composition, but these alterations can be prevented by structural amelioration of NMJ with endurance training. Our findings highlight the importance of the NMJ as a major determinant of age-related deterioration of skeletal muscles and the clinical significance of endurance training as a countermeasure. KEY POINTS: The neuromuscular junction (NMJ) plays an essential role in neuromuscular transmission and the maintenance of myofibre properties. We show that neuromuscular transmission is impaired with ageing but recovered by endurance training, which contributes to alterations in voluntary strength. Neuromuscular transmission is associated with the degree of pre- to post-synaptic overlap of the NMJ. Age-related denervation of fast-twitch fibres and a shift in myofibre composition toward a slower phenotype are partially prevented by endurance training. Our study provides substantial evidence that age-related and exercise-induced alterations in neuromuscular transmission and myofibre properties are associated with morphological changes in the NMJ.
Collapse
Affiliation(s)
- Tatsuhiro Yamaguchi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
- Japan Society for the Promotion of Science, Tokyo, Japan
| | - Karina Kouzaki
- Graduate School of Health and Sport Science, Nippon Sport Science University, Tokyo, Japan
| | - Kazushige Sasaki
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | - Koichi Nakazato
- Graduate School of Health and Sport Science, Nippon Sport Science University, Tokyo, Japan
| |
Collapse
|
4
|
Jaime D, Fish LA, Madigan LA, Xi C, Piccoli G, Ewing MD, Blaauw B, Fallon JR. The MuSK-BMP pathway maintains myofiber size in slow muscle through regulation of Akt-mTOR signaling. Skelet Muscle 2024; 14:1. [PMID: 38172960 PMCID: PMC10763067 DOI: 10.1186/s13395-023-00329-9] [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: 02/21/2023] [Accepted: 10/19/2023] [Indexed: 01/05/2024] Open
Abstract
Myofiber size regulation is critical in health, disease, and aging. MuSK (muscle-specific kinase) is a BMP (bone morphogenetic protein) co-receptor that promotes and shapes BMP signaling. MuSK is expressed at all neuromuscular junctions and is also present extrasynaptically in the mouse soleus, whose predominantly oxidative fiber composition is akin to that of human muscle. To investigate the role of the MuSK-BMP pathway in vivo, we generated mice lacking the BMP-binding MuSK Ig3 domain. These ∆Ig3-MuSK mice are viable and fertile with innervation levels comparable to wild type. In 3-month-old mice, myofibers are smaller in the slow soleus, but not in the fast tibialis anterior (TA). Transcriptomic analysis revealed soleus-selective decreases in RNA metabolism and protein synthesis pathways as well as dysregulation of IGF1-Akt-mTOR pathway components. Biochemical analysis showed that Akt-mTOR signaling is reduced in soleus but not TA. We propose that the MuSK-BMP pathway acts extrasynaptically to maintain myofiber size in slow muscle by promoting protein synthetic pathways including IGF1-Akt-mTOR signaling. These results reveal a novel mechanism for regulating myofiber size in slow muscle and introduce the MuSK-BMP pathway as a target for promoting muscle growth and combatting atrophy.
Collapse
Grants
- R41 AG073144 NIA NIH HHS
- T32 MH020068 NIMH NIH HHS
- U01 NS064295, R41 AG073144, R21 NS112743, R21 AG073743, P30 GM103410, P30 RR031153, P20 RR018728, S10 RR02763, R25GM083270, 2T32AG041688, and T32 MH20068 NIH HHS
- P30 GM103410 NIGMS NIH HHS
- T32 AG041688 NIA NIH HHS
- P30 RR031153 NCRR NIH HHS
- U01 NS064295 NINDS NIH HHS
- R21 NS112743 NINDS NIH HHS
- P20 RR018728 NCRR NIH HHS
- R21 AG073743 NIA NIH HHS
- R25 GM083270 NIGMS NIH HHS
- National Institutes of Health
- Carney Institute for Brain Sciences
- ALS Finding a Cure
- AFM-Téléthon
Collapse
Affiliation(s)
- Diego Jaime
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
| | - Lauren A Fish
- Department of Neuroscience, Brown University, Providence, RI, 02912, USA
| | - Laura A Madigan
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
| | - Chengjie Xi
- Department of Neuroscience, Brown University, Providence, RI, 02912, USA
| | - Giorgia Piccoli
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Madison D Ewing
- Department of Neuroscience, Brown University, Providence, RI, 02912, USA
| | - Bert Blaauw
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Justin R Fallon
- Department of Neuroscience, Brown University, Providence, RI, 02912, USA.
- Carney Institute for Neuroscience, Brown University, Providence, RI, USA.
| |
Collapse
|
5
|
Cescon M, Gambarotta G, Calabrò S, Cicconetti C, Anselmi F, Kankowski S, Lang L, Basic M, Bleich A, Bolsega S, Steglich M, Oliviero S, Raimondo S, Bizzotto D, Haastert-Talini K, Ronchi G. Gut microbiota depletion delays somatic peripheral nerve development and impairs neuromuscular junction maturation. Gut Microbes 2024; 16:2363015. [PMID: 38845453 PMCID: PMC11164225 DOI: 10.1080/19490976.2024.2363015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 05/29/2024] [Indexed: 06/12/2024] Open
Abstract
Gut microbiota is responsible for essential functions in human health. Several communication axes between gut microbiota and other organs via neural, endocrine, and immune pathways have been described, and perturbation of gut microbiota composition has been implicated in the onset and progression of an emerging number of diseases. Here, we analyzed peripheral nerves, dorsal root ganglia (DRG), and skeletal muscles of neonatal and young adult mice with the following gut microbiota status: a) germ-free (GF), b) gnotobiotic, selectively colonized with 12 specific gut bacterial strains (Oligo-Mouse-Microbiota, OMM12), or c) natural complex gut microbiota (CGM). Stereological and morphometric analyses revealed that the absence of gut microbiota impairs the development of somatic median nerves, resulting in smaller diameter and hypermyelinated axons, as well as in smaller unmyelinated fibers. Accordingly, DRG and sciatic nerve transcriptomic analyses highlighted a panel of differentially expressed developmental and myelination genes. Interestingly, the type III isoform of Neuregulin1 (NRG1), known to be a neuronal signal essential for Schwann cell myelination, was overexpressed in young adult GF mice, with consequent overexpression of the transcription factor Early Growth Response 2 (Egr2), a fundamental gene expressed by Schwann cells at the onset of myelination. Finally, GF status resulted in histologically atrophic skeletal muscles, impaired formation of neuromuscular junctions, and deregulated expression of related genes. In conclusion, we demonstrate for the first time a gut microbiota regulatory impact on proper development of the somatic peripheral nervous system and its functional connection to skeletal muscles, thus suggesting the existence of a novel 'Gut Microbiota-Peripheral Nervous System-axis.'
Collapse
Affiliation(s)
- Matilde Cescon
- Department of Molecular Medicine, University of Padova, Padova, Italy
| | - Giovanna Gambarotta
- Department of Clinical and Biological Sciences & Neuroscience Institute Cavalieri Ottolenghi (NICO), University of Torino, Orbassano, Italy
| | - Sonia Calabrò
- Department of Molecular Medicine, University of Padova, Padova, Italy
- Department of Biology, University of Padova, Padova, Italy
| | - Chiara Cicconetti
- Department of Life Sciences and Systems Biology, University of Torino, Torino, Italy
| | - Francesca Anselmi
- Department of Life Sciences and Systems Biology, University of Torino, Torino, Italy
| | - Svenja Kankowski
- Institute of Neuroanatomy and Cell Biology, Hannover Medical School, Hannover, Lower-Saxony, Germany
| | - Luisa Lang
- Institute of Neuroanatomy and Cell Biology, Hannover Medical School, Hannover, Lower-Saxony, Germany
| | - Marijana Basic
- Institute for Laboratory Animal Science and Central Animal Facility, Hannover Medical School, Hannover, Lower-Saxony, Germany
| | - Andre Bleich
- Institute for Laboratory Animal Science and Central Animal Facility, Hannover Medical School, Hannover, Lower-Saxony, Germany
| | - Silvia Bolsega
- Institute for Laboratory Animal Science and Central Animal Facility, Hannover Medical School, Hannover, Lower-Saxony, Germany
| | - Matthias Steglich
- Research Core Unit Genomics, Hannover Medical School, Hannover, Lower-Saxony, Germany
| | - Salvatore Oliviero
- Department of Life Sciences and Systems Biology, University of Torino, Torino, Italy
| | - Stefania Raimondo
- Department of Clinical and Biological Sciences & Neuroscience Institute Cavalieri Ottolenghi (NICO), University of Torino, Orbassano, Italy
| | - Dario Bizzotto
- Department of Molecular Medicine, University of Padova, Padova, Italy
| | - Kirsten Haastert-Talini
- Institute of Neuroanatomy and Cell Biology, Hannover Medical School, Hannover, Lower-Saxony, Germany
- Centre for Systems Neuroscience (ZSN), Hannover Medical School, Hannover, Lower-Saxony, Germany
| | - Giulia Ronchi
- Department of Clinical and Biological Sciences & Neuroscience Institute Cavalieri Ottolenghi (NICO), University of Torino, Orbassano, Italy
| |
Collapse
|
6
|
Gambarotto L, Metti S, Corpetti M, Baraldo M, Sabatelli P, Castagnaro S, Cescon M, Blaauw B, Bonaldo P. Sustained oral spermidine supplementation rescues functional and structural defects in COL6-deficient myopathic mice. Autophagy 2023; 19:3221-3229. [PMID: 37528588 PMCID: PMC10621270 DOI: 10.1080/15548627.2023.2241125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/03/2023] Open
Abstract
COL6 (collagen type VI)-related myopathies (COL6-RM) are a distinct group of inherited muscle disorders caused by mutations of COL6 genes and characterized by early-onset muscle weakness, for which no cure is available yet. Key pathophysiological features of COL6-deficient muscles involve impaired macroautophagy/autophagy, mitochondrial dysfunction, neuromuscular junction fragmentation and myofiber apoptosis. Targeting autophagy by dietary means elicited beneficial effects in both col6a1 null (col6a1-/-) mice and COL6-RM patients. We previously demonstrated that one-month per os administration of the nutraceutical spermidine reactivates autophagy and ameliorates myofiber defects in col6a1-/- mice but does not elicit functional improvement. Here we show that a 100-day-long spermidine regimen is able to rescue muscle strength in col6a1-/- mice, with also a beneficial impact on mitochondria and neuromuscular junction integrity, without any noticeable side effects. Altogether, these data provide a rationale for the application of spermidine in prospective clinical trials for COL6-RM.Abbreviations: AChR: acetylcholine receptor; BTX: bungarotoxin; CNF: centrally nucleated fibers; Colch: colchicine; COL6: collagen type VI; COL6-RM: COL6-related myopathies; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; NMJ: neuromuscular junction; Spd: spermidine; SQSTM1/p62: sequestosome 1; TA: tibialis anterior; TOMM20: translocase of outer mitochondrial membrane 20; TUNEL: terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling.
Collapse
Affiliation(s)
- Lisa Gambarotto
- Department of Molecular Medicine, University of Padova, Padova, Italy
- Department of Biology, University of Padova, Padova, Italy
| | - Samuele Metti
- Department of Molecular Medicine, University of Padova, Padova, Italy
| | - Matteo Corpetti
- Department of Molecular Medicine, University of Padova, Padova, Italy
| | - Martina Baraldo
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Patrizia Sabatelli
- CNR-Institute of Molecular Genetics ”Luigi Luca Cavalli-Sforza”, Unit of Bologna, Bologna, Italy
| | - Silvia Castagnaro
- Department of Molecular Medicine, University of Padova, Padova, Italy
| | - Matilde Cescon
- Department of Molecular Medicine, University of Padova, Padova, Italy
| | - Bert Blaauw
- Department of Biomedical Sciences, University of Padova, Padova, Italy
- Venetian Institute of Molecular Medicine, Padova, Italy
| | - Paolo Bonaldo
- Department of Molecular Medicine, University of Padova, Padova, Italy
| |
Collapse
|
7
|
Fish LA, Ewing MD, Jaime D, Rich KA, Xi C, Wang X, Feder RE, Wharton KA, Rich MM, Arnold WD, Fallon JR. The MuSK-BMP pathway regulates synaptic Nav1.4 localization and muscle excitability. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.24.563837. [PMID: 37961580 PMCID: PMC10634800 DOI: 10.1101/2023.10.24.563837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
The neuromuscular junction (NMJ) is the linchpin of nerve-evoked muscle contraction. Broadly considered, the function of the NMJ is to transduce a nerve action potential into a muscle fiber action potential (MFAP). Efficient information transfer requires both cholinergic signaling, responsible for the generation of endplate potentials (EPPs), and excitation, the activation of postsynaptic voltage-gated sodium channels (Nav1.4) to trigger MFAPs. In contrast to the cholinergic apparatus, the signaling pathways that organize Nav1.4 and muscle fiber excitability are poorly characterized. Muscle-specific kinase (MuSK), in addition to its Ig1 domain-dependent role as an agrin-LRP4 receptor, is also a BMP co-receptor that binds BMPs via its Ig3 domain and shapes BMP-induced signaling and transcriptional output. Here we probed the function of the MuSK-BMP pathway at the NMJ using mice lacking the MuSK Ig3 domain ('ΔIg3-MuSK'). Synapses formed normally in ΔIg3-MuSK animals, but the postsynaptic apparatus was fragmented from the first weeks of life. Anatomical denervation was not observed at any age examined. Moreover, spontaneous and nerve-evoked acetylcholine release, AChR density, and endplate currents were comparable to WT. However, trains of nerve-evoked MFAPs in ΔIg3-MuSK muscle were abnormal as revealed by increased jitter and blocking in single fiber electromyography. Further, nerve-evoked compound muscle action potentials (CMAPs), as well as twitch and tetanic muscle torque force production, were also diminished. Finally, Nav1.4 levels were reduced at ΔIg3-MuSK synapses but not at the extrajunctional sarcolemma, indicating that the observed excitability defects are the result of impaired localization of this voltage-gated ion channel at the NMJ. We propose that MuSK plays two distinct roles at the NMJ: as an agrin-LRP4 receptor necessary for establishing and maintaining cholinergic signaling, and as a BMP co-receptor required for maintaining proper Nav1.4 density, nerve-evoked muscle excitability and force production. The MuSK-BMP pathway thus emerges as a target for modulating excitability and functional innervation, which are defective in conditions such as congenital myasthenic syndromes and aging.
Collapse
Affiliation(s)
- L. A. Fish
- Neuroscience Graduate Program, Brown University, Providence, RI 02912
- Carney Institute for Brain Science, Brown University, Providence, RI 02912
| | - M. D. Ewing
- Department of Neuroscience, Brown University, Providence, RI 02912
| | - D. Jaime
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI 02912
| | - K. A. Rich
- Neuroscience Graduate Program, Ohio State University, Columbus, OH 43210
| | - C. Xi
- Biotechnology Graduate Program, Brown University, Brown University, Providence, RI 02912
| | - X. Wang
- Department of Neuroscience Cell Biology and Physiology, Wright State University, Dayton, OH 45435
| | - R. E. Feder
- Department of Neuroscience, Brown University, Providence, RI 02912
| | - K. A. Wharton
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI 02912
| | - M. M. Rich
- Department of Neuroscience Cell Biology and Physiology, Wright State University, Dayton, OH 45435
| | - W. D. Arnold
- NextGen Precision Health Institute, University of Missouri, Columbia, MO 62511
| | - J. R. Fallon
- Carney Institute for Brain Science, Brown University, Providence, RI 02912
- Department of Neuroscience, Brown University, Providence, RI 02912
| |
Collapse
|
8
|
Alhindi A, Shand M, Smith HL, Leite AS, Huang YT, van der Hoorn D, Ridgway Z, Faller KME, Jones RA, Gillingwater TH, Chaytow H. Neuromuscular junction denervation and terminal Schwann cell loss in the hTDP-43 overexpression mouse model of amyotrophic lateral sclerosis. Neuropathol Appl Neurobiol 2023; 49:e12925. [PMID: 37465879 DOI: 10.1111/nan.12925] [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: 03/01/2023] [Revised: 06/30/2023] [Accepted: 07/11/2023] [Indexed: 07/20/2023]
Abstract
AIMS Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with complex aetiology. Despite evidence of neuromuscular junction (NMJ) denervation and 'dying-back' pathology in models of SOD1-dependent ALS, evidence in other genetic forms of ALS is limited by a lack of suitable animal models. TDP-43, a key mediator protein in ALS, is overexpressed in neurons in Thy1-hTDP-43WT mice. We therefore aimed to comprehensively analyse NMJ pathology in this model of ALS. METHODS Expression of TDP-43 was assessed via western blotting. Immunohistochemistry techniques, alongside NMJ-morph quantification, were used to analyse motor neuron number, NMJ denervation status and terminal Schwann cell morphology. RESULTS We present a time course of progressive, region-specific motor neuron pathology in Thy1-hTDP-43WT mice. Thy1-driven hTDP-43 expression increased steadily, correlating with developing hindlimb motor weakness and associated motor neuron loss in the spinal cord with a median survival of 21 days. Pronounced NMJ denervation was observed in hindlimb muscles, mild denervation in cranial muscles but no evidence of denervation in either forelimb or trunk muscles. NMJ pathology was restricted to motor nerve terminals, with denervation following the same time course as motor neuron loss. Terminal Schwann cells were lost from NMJs in hindlimb muscles, directly correlating with denervation status. CONCLUSIONS Thy1-hTDP-43WT mice represent a severe model of ALS, with NMJ pathology/denervation of distal muscles and motor neuron loss, as observed in ALS patients. This model therefore provides an ideal platform to investigate mechanisms of dying-back pathology, as well as NMJ-targeting disease-modifying therapies in ALS.
Collapse
Affiliation(s)
- Abrar Alhindi
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh, UK
- Faculty of Medicine, Department of Anatomy, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Megan Shand
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh, UK
| | - Hannah L Smith
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh, UK
| | - Ana S Leite
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh, UK
- School of Medicine, UNESP-São Paulo State University, Botucatu, Sao Paulo, Brazil
| | - Yu-Ting Huang
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh, UK
| | - Dinja van der Hoorn
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh, UK
| | - Zara Ridgway
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh, UK
| | - Kiterie M E Faller
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh, UK
- Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, UK
| | - Ross A Jones
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh, UK
| | - Thomas H Gillingwater
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh, UK
| | - Helena Chaytow
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, Edinburgh, UK
| |
Collapse
|
9
|
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.
Collapse
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
| |
Collapse
|
10
|
Cahalan SD, Perkins JD, Boehm I, Jones RA, Gillingwater TH, Piercy RJ. A method to identify, dissect and stain equine neuromuscular junctions for morphological analysis. J Anat 2022; 241:1133-1147. [PMID: 36087283 PMCID: PMC9558161 DOI: 10.1111/joa.13747] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Revised: 08/05/2022] [Accepted: 08/08/2022] [Indexed: 12/23/2022] Open
Abstract
Morphological study of the neuromuscular junction (NMJ), a specialised peripheral synapse formed between a lower motor neuron and skeletal muscle fibre, has significantly contributed to the understanding of synaptic biology and neuromuscular disease pathogenesis. Rodent NMJs are readily accessible, and research into conditions such as amyotrophic lateral sclerosis (ALS), Charcot–Marie–Tooth disease (CMT), and spinal muscular atrophy (SMA) has relied heavily on experimental work in these small mammals. However, given that nerve length dependency is an important feature of many peripheral neuropathies, these rodent models have clear shortcomings; large animal models might be preferable, but their size presents novel anatomical challenges. Overcoming these constraints to study the NMJ morphology of large mammalian distal limb muscles is of prime importance to increase cross‐species translational neuromuscular research potential, particularly in the study of long motor units. In the past, NMJ phenotype analysis of large muscle bodies within the equine distal pelvic limb, such as the tibialis cranialis, or within muscles of high fibrous content, such as the soleus, has posed a distinct experimental hurdle. We optimised a technique for NMJ location and dissection from equine pelvic limb muscles. Using a quantification method validated in smaller species, we demonstrate their morphology and show that equine NMJs can be reliably dissected, stained and analysed. We reveal that the NMJs within the equine soleus have distinctly different morphologies when compared to the extensor digitorum longus and tibialis cranialis muscles. Overall, we demonstrate that equine distal pelvic limb muscles can be regionally dissected, with samples whole‐mounted and their innervation patterns visualised. These methods will allow the localisation and analysis of neuromuscular junctions within the muscle bodies of large mammals to identify neuroanatomical and neuropathological features.
Collapse
Affiliation(s)
- Stephen D Cahalan
- Comparative Neuromuscular Diseases Laboratory, Department of Clinical Science and Services, Royal Veterinary College, London, UK
| | - Justin D Perkins
- Comparative Neuromuscular Diseases Laboratory, Department of Clinical Science and Services, Royal Veterinary College, London, UK
| | - Ines Boehm
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neuron Disease Research, University of Edinburgh, Edinburgh, UK.,Biozentrum, University of Basel, Basel, Switzerland
| | - Ross A Jones
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neuron Disease Research, University of Edinburgh, Edinburgh, UK
| | - Thomas H Gillingwater
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neuron Disease Research, University of Edinburgh, Edinburgh, UK
| | - Richard J Piercy
- Comparative Neuromuscular Diseases Laboratory, Department of Clinical Science and Services, Royal Veterinary College, London, UK
| |
Collapse
|
11
|
Cahalan SD, Boehm I, Jones RA, Piercy RJ. Recognising the potential of large animals for modelling neuromuscular junction physiology and disease. J Anat 2022; 241:1120-1132. [PMID: 36056593 PMCID: PMC9558152 DOI: 10.1111/joa.13749] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 08/05/2022] [Accepted: 08/08/2022] [Indexed: 12/28/2022] Open
Abstract
The aetiology and pathophysiology of many diseases of the motor unit remain poorly understood and the role of the neuromuscular junction (NMJ) in this group of disorders is particularly overlooked, especially in humans, when these diseases are comparatively rare. However, elucidating the development, function and degeneration of the NMJ is essential to uncover its contribution to neuromuscular disorders, and to explore potential therapeutic avenues to treat these devastating diseases. Until now, an understanding of the role of the NMJ in disease pathogenesis has been hindered by inherent differences between rodent and human NMJs: stark contrasts in body size and corresponding differences in associated axon length underpin some of the translational issues in animal models of neuromuscular disease. Comparative studies in large mammalian models, including examination of naturally occurring, highly prevalent animal diseases and evaluation of their treatment, might provide more relevant insights into the pathogenesis and therapy of equivalent human diseases. This review argues that large animal models offer great potential to enhance our understanding of the neuromuscular system in health and disease, and in particular, when dealing with diseases for which nerve length dependency might underly the pathogenesis.
Collapse
Affiliation(s)
- Stephen D Cahalan
- Comparative Neuromuscular Diseases Laboratory, Department of Clinical Science and Services, Royal Veterinary College, University of London, London, UK
| | - Ines Boehm
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK.,Biozentrum University of Basel, Basel, Switzerland
| | - Ross A Jones
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK
| | - Richard J Piercy
- Comparative Neuromuscular Diseases Laboratory, Department of Clinical Science and Services, Royal Veterinary College, University of London, London, UK
| |
Collapse
|
12
|
Angiogenesis is critical for the exercise-mediated enhancement of axon regeneration following peripheral nerve injury. Exp Neurol 2022; 353:114029. [DOI: 10.1016/j.expneurol.2022.114029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 02/17/2022] [Accepted: 02/27/2022] [Indexed: 11/21/2022]
|
13
|
Villarroel-Campos D, Schiavo G, Sleigh JN. Dissection, in vivo imaging and analysis of the mouse epitrochleoanconeus muscle. J Anat 2021; 241:1108-1119. [PMID: 34121181 PMCID: PMC9558155 DOI: 10.1111/joa.13478] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 05/07/2021] [Accepted: 05/18/2021] [Indexed: 12/25/2022] Open
Abstract
Analysis of rodent muscles affords an opportunity to glean key insights into neuromuscular development and the detrimental impact of disease‐causing genetic mutations. Muscles of the distal leg, for instance the gastrocnemius and tibialis anterior, are commonly used in such studies with mice and rats. However, thin and flat muscles, which can be dissected, processed and imaged without major disruption to muscle fibres and nerve‐muscle contacts, are more suitable for accurate and detailed analyses of the peripheral motor nervous system. One such wholemount muscle is the predominantly fast twitch epitrochleoanconeus (ETA), which is located in the upper forelimb, innervated by the radial nerve, and contains relatively large and uniformly flat neuromuscular junctions (NMJs). To facilitate incorporation of the ETA into the experimental toolkit of the neuromuscular disease field, here, we describe a simple method for its rapid isolation (<5 min), supported by high‐resolution videos and step‐by‐step images. Furthermore, we outline how the ETA can be imaged in live, anaesthetised mice, to enable examination of dynamic cellular processes occurring at the NMJ and within intramuscular axons, including transport of organelles, such as mitochondria and signalling endosomes. Finally, we present reference data on wild‐type ETA fibre‐type composition in young adult, male C57BL6/J mice. Comparative neuroanatomical studies of different muscles in rodent models of disease can generate critical insights into pathogenesis and pathology; dissection of the wholemount ETA provides the possibility to diversify the repertoire of muscles analysed for this endeavour.
Collapse
Affiliation(s)
- David Villarroel-Campos
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK
| | - Giampietro Schiavo
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK.,UK Dementia Research Institute, University College London, London, UK
| | - James N Sleigh
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK.,UK Dementia Research Institute, University College London, London, UK
| |
Collapse
|
14
|
NMJ-Analyser identifies subtle early changes in mouse models of neuromuscular disease. Sci Rep 2021; 11:12251. [PMID: 34112844 PMCID: PMC8192785 DOI: 10.1038/s41598-021-91094-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 04/26/2021] [Indexed: 12/21/2022] Open
Abstract
The neuromuscular junction (NMJ) is the peripheral synapse formed between a motor neuron axon terminal and a muscle fibre. NMJs are thought to be the primary site of peripheral pathology in many neuromuscular diseases, but innervation/denervation status is often assessed qualitatively with poor systematic criteria across studies, and separately from 3D morphological structure. Here, we describe the development of ‘NMJ-Analyser’, to comprehensively screen the morphology of NMJs and their corresponding innervation status automatically. NMJ-Analyser generates 29 biologically relevant features to quantitatively define healthy and aberrant neuromuscular synapses and applies machine learning to diagnose NMJ degeneration. We validated this framework in longitudinal analyses of wildtype mice, as well as in four different neuromuscular disease models: three for amyotrophic lateral sclerosis (ALS) and one for peripheral neuropathy. We showed that structural changes at the NMJ initially occur in the nerve terminal of mutant TDP43 and FUS ALS models. Using a machine learning algorithm, healthy and aberrant neuromuscular synapses are identified with 95% accuracy, with 88% sensitivity and 97% specificity. Our results validate NMJ-Analyser as a robust platform for systematic and structural screening of NMJs, and pave the way for transferrable, and cross-comparison and high-throughput studies in neuromuscular diseases.
Collapse
|
15
|
Alhindi A, Boehm I, Chaytow H. Small junction, big problems: Neuromuscular junction pathology in mouse models of amyotrophic lateral sclerosis (ALS). J Anat 2021; 241:1089-1107. [PMID: 34101196 PMCID: PMC9558162 DOI: 10.1111/joa.13463] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 05/10/2021] [Accepted: 05/11/2021] [Indexed: 01/31/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a motor neuron disease with an extremely heterogeneous clinical and genetic phenotype. In our efforts to find therapies for ALS, the scientific community has developed a plethora of mouse models, each with their own benefits and drawbacks. The peripheral nervous system, specifically the neuromuscular junction (NMJ), is known to be affected in ALS patients and shows marked dysfunction across mouse models. Evidence of pathology at the NMJ includes denervated NMJs, changes in endplate size and loss of terminal Schwann cells. This review compares the temporal disease progression with severity of disease at the NMJ in mouse models with the most commonly mutated genes in ALS patients (SOD1, C9ORF72, TARDBP and FUS). Despite variability, early NMJ dysfunction seems to be a common factor in models with SOD1, TARDBP and FUS mutations, while C9ORF72 models do not appear to follow the same pattern of pathology. Further work into determining the timing of NMJ pathology, particularly in newer ALS mouse models, will confirm its pivotal role in ALS pathogenesis and therefore highlight the NMJ as a potential therapeutic target.
Collapse
Affiliation(s)
- Abrar Alhindi
- Edinburgh Medical School, Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Department of Anatomy, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK
| | - Ines Boehm
- Edinburgh Medical School, Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK
| | - Helena Chaytow
- Edinburgh Medical School, Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK
| |
Collapse
|
16
|
Alhindi A, Boehm I, Forsythe RO, Miller J, Skipworth RJE, Simpson H, Jones RA, Gillingwater TH. Terminal Schwann cells at the human neuromuscular junction. Brain Commun 2021; 3:fcab081. [PMID: 33977269 PMCID: PMC8093923 DOI: 10.1093/braincomms/fcab081] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 02/09/2021] [Accepted: 03/03/2021] [Indexed: 12/13/2022] Open
Abstract
Terminal Schwann cells are non-myelinating glial cells localized to the neuromuscular junction. They play an important role in regulating many aspects of neuromuscular junction form and function, in health and during disease. However, almost all previous studies of mammalian terminal Schwann cells have used rodent models. Despite a growing awareness of differences in the cellular and molecular anatomy of rodent and human neuromuscular junctions, it remains unclear as to whether these differences also extend to the terminal Schwann cells. Here, we have adapted immunohistochemical protocols to facilitate visualization and comparative morphometric analyses of terminal Schwann cells at the human and mouse neuromuscular junction. We labelled terminal Schwann cells in the peroneus brevis muscle in six adult mice and five humans with antibodies against S100 protein. All human neuromuscular junctions were associated with at least one terminal Schwann cell, consistent with findings from other species, with an average of ∼1.7 terminal Schwann cells per neuromuscular junction in both humans and mice. In contrast, human terminal Schwann cells were significantly smaller than those of mice (P ≤ 0.01), in keeping with differences in overall synaptic size. Human terminal Schwann cell cytoplasm extended significantly beyond the synaptic boundaries of the neuromuscular junction, whereas terminal Schwann cells in mice were largely restricted to the synapse. Moreover, there was a significant difference in the location of terminal Schwann cell nuclei (P ≤ 0.01), with human terminal Schwann cells having their nuclear compartment located beyond the perimeter of the synapse more than the mouse. Taken together, these findings demonstrate that terminal Schwann cells at the human neuromuscular junction have notable differences in their morphology and synaptic relationships compared to mice. These fundamental differences need to be considered when translating the findings of both neuromuscular junction biology and pathology from rodents to humans.
Collapse
Affiliation(s)
- Abrar Alhindi
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh EH16 4SB, UK.,Faculty of Medicine, Department of Anatomy, King Abdulaziz University, Jeddah 22252, Saudi Arabia
| | - Ines Boehm
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Rachael O Forsythe
- Clinical Surgery, Edinburgh Medical School, and Royal Infirmary of Edinburgh, Edinburgh EH16 4SA, UK
| | - Janice Miller
- Clinical Surgery, Edinburgh Medical School, and Royal Infirmary of Edinburgh, Edinburgh EH16 4SA, UK
| | - Richard J E Skipworth
- Clinical Surgery, Edinburgh Medical School, and Royal Infirmary of Edinburgh, Edinburgh EH16 4SA, UK
| | - Hamish Simpson
- Department of Orthopaedic Surgery, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Ross A Jones
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Thomas H Gillingwater
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh EH16 4SB, UK
| |
Collapse
|