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Mandeville R, Sanchez B, Johnston B, Bazarek S, Thum JA, Birmingham A, See RHB, Leochico CFD, Kumar V, Dowlatshahi AS, Brown J, Stashuk D, Rutkove SB. A scoping review of current and emerging techniques for evaluation of peripheral nerve health, degeneration, and regeneration: part 1, neurophysiology. J Neural Eng 2023; 20:041001. [PMID: 37279730 DOI: 10.1088/1741-2552/acdbeb] [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: 01/18/2023] [Accepted: 06/06/2023] [Indexed: 06/08/2023]
Abstract
Peripheral neuroregeneration research and therapeutic options are expanding exponentially. With this expansion comes an increasing need to reliably evaluate and quantify nerve health. Valid and responsive measures that can serve as biomarkers of the nerve status are essential for both clinical and research purposes for diagnosis, longitudinal follow-up, and monitoring the impact of any intervention. Furthermore, such biomarkers can elucidate regeneration mechanisms and open new avenues for research. Without these measures, clinical decision-making falls short, and research becomes more costly, time-consuming, and sometimes infeasible. As a companion to Part 2, which is focused on non-invasive imaging, Part 1 of this two-part scoping review systematically identifies and critically examines many current and emerging neurophysiological techniques that have the potential to evaluate peripheral nerve health, particularly from the perspective of regenerative therapies and research.
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Affiliation(s)
- Ross Mandeville
- Department of Neurology, Beth Israel Deaconess Medical Center, Boston, MA 02215, United States of America
| | - Benjamin Sanchez
- Department Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112, United States of America
| | - Benjamin Johnston
- Department of Neurosurgery, Brigham and Women's Hospital, Boston, MA 02115, United States of America
| | - Stanley Bazarek
- Department of Neurosurgery, Brigham and Women's Hospital, Boston, MA 02115, United States of America
| | - Jasmine A Thum
- Department of Neurosurgery, Massachusetts General Hospital, Boston, MA 02114, United States of America
| | - Austin Birmingham
- Department of Neurosurgery, Massachusetts General Hospital, Boston, MA 02114, United States of America
| | - Reiner Henson B See
- Department of Neurology, Massachusetts General Hospital, Boston, MA 02114, United States of America
| | - Carl Froilan D Leochico
- Department of Physical Medicine and Rehabilitation, St. Luke's Medical Center, Global City, Taguig, The Philippines
- Department of Rehabilitation Medicine, Philippine General Hospital, University of the Philippines Manila, Manila, The Philippines
| | - Viksit Kumar
- Department of Radiology, Massachusetts General Hospital, Boston, MA 02114, United States of America
| | - Arriyan S Dowlatshahi
- Department of Surgery, Beth Israel Deaconess Medical Center, Boston, MA 02215, United States of America
| | - Justin Brown
- Department of Neurosurgery, Massachusetts General Hospital, Boston, MA 02114, United States of America
| | - Daniel Stashuk
- Department of Systems Design Engineering, University of Waterloo, Ontario N2L 3G1, Canada
| | - Seward B Rutkove
- Department of Neurology, Beth Israel Deaconess Medical Center, Boston, MA 02215, United States of America
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McGregor C, Sabatier M, English A. Early regeneration of axons following peripheral nerve injury is enhanced if p75 NTR is eliminated from the surrounding pathway. Eur J Neurosci 2020; 53:663-672. [PMID: 32812660 DOI: 10.1111/ejn.14943] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 08/03/2020] [Accepted: 08/12/2020] [Indexed: 11/30/2022]
Abstract
The common neurotrophin receptor, p75NTR , has been proposed to be an inhibitor of axon regeneration after peripheral nerve injury, but whether this effect is on the regenerating axons, immune cells migrating into the injury site, or cells in the pathway surrounding the axons is not clear. Cut nerves in mice expressing fluorescent proteins in axons were repaired with grafts from non-fluorescent hosts to study axon elongation when p75NTR was eliminated separately from axons and immune cells in the proximal stump of cut nerves, from cells in the regeneration pathway, or both. Two weeks later, axons from wild type mice regenerating into grafts devoid of p75NTR had elongated more than twice as far as axons in grafts from wild type mice. No enhancement of regeneration of axons in p75NTR knockout mice was observed, whether nerves were repaired with grafts from wild type mice or from p75NTR knockout mice. To evaluate whether inhibition of p75NTR could be used to improve regeneration, nerves in wild type mice repaired without grafts were exposed to a specific inhibitor of the p75NTR receptor, LM11A-31, at the time of nerve repair. This local blockade of p75NTR resulted in successful regeneration of axons of nearly three times as many motoneurons and reinnervation of twice as many muscle fibers by regenerating motor axons as untreated controls. Expression of p75NTR surrounding regenerating axons contributes to poor regeneration during the first 2 weeks after peripheral nerve injury. Inhibition of p75NTR might be a therapeutic target for treatments of peripheral nerve injuries.
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Affiliation(s)
- Claire McGregor
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA
| | - Manning Sabatier
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA
| | - Arthur English
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA
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Taylor SA, Sherlock C, Ridall G, Fearnhead P. Motor unit number estimation via sequential Monte Carlo. Comput Stat Data Anal 2020. [DOI: 10.1016/j.csda.2019.106845] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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McGregor CE, Irwin AM, English AW. The Val66Met BDNF Polymorphism and Peripheral Nerve Injury: Enhanced Regeneration in Mouse Met-Carriers Is Not Further Improved With Activity-Dependent Treatment. Neurorehabil Neural Repair 2019; 33:407-418. [PMID: 31068076 DOI: 10.1177/1545968319846131] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Activity-dependent treatments to enhance peripheral nerve regeneration after injury have shown great promise, and clinical trials implementing them have begun. Success of these treatments requires activity-dependent release of brain-derived neurotrophic factor (BDNF). A single nucleotide polymorphism (SNP) in the bdnf gene known as Val66Met, which is found in nearly one third of the human population, results in defective activity-dependent BDNF secretion and could impact the effectiveness of these therapies. Here, we used a mouse model of this SNP to test the efficacy of treadmill exercise in enhancing axon regeneration in animals both heterozygous (V/M) and homozygous (M/M) for the SNP. Axon regeneration was studied 4 weeks after complete transection and repair of the sciatic nerve in both male and female animals, using both electrophysiological and histological outcome measures. Regeneration was enhanced significantly without treatment in V/M mice, compared with wild type (V/V) controls. Unlike V/V mice, treatment of both V/M and M/M mice with treadmill exercise did not result in enhanced regeneration. These results were recapitulated in vitro using dissociated neurons containing the light-sensitive cation channel, channelrhodopsin. Three days after plating, neurites of neurons from V/M and M/M mice were longer than those of V/V neurons. In neurons from V/V mice, but not those from V/M or M/M animals, longer neurites were found after optogenetic stimulation. Taken together, Met-carriers possess an intrinsically greater capacity to regenerate axons in peripheral nerves, but this cannot be enhanced further by activity-dependent treatments.
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Manuel M, Chardon M, Tysseling V, Heckman CJ. Scaling of Motor Output, From Mouse to Humans. Physiology (Bethesda) 2019; 34:5-13. [PMID: 30540233 DOI: 10.1152/physiol.00021.2018] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Appropriate scaling of motor output from mouse to humans is essential. The motoneurons that generate all motor output are, however, very different in rodents compared with humans, being smaller and much more excitable. In contrast, feline motoneurons are more similar to those in humans. These scaling differences need to be taken into account for the use of rodents for translational studies of motor output.
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Affiliation(s)
- Marin Manuel
- Centre de Neurophysique, Physiologie, et Pathologie, UMR 8119 CNRS/Université Paris Descartes , Paris , France
| | - Matthieu Chardon
- Physiology, Northwestern University Feinberg School of Medicine , Chicago, Illinois
| | - Vicki Tysseling
- Physical Therapy and Human Movement Sciences, Physiology, Northwestern University Feinberg School of Medicine , Chicago, Illinois
| | - C J Heckman
- Physiology, Physical Medicine and Rehabilitation, Physical Therapy and Human Movement Sciences, Northwestern University Feinberg School of Medicine , Chicago, Illinois
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Wang L, Gao J, Liu J, Siedlak SL, Torres S, Fujioka H, Huntley ML, Jiang Y, Ji H, Yan T, Harland M, Termsarasab P, Zeng S, Jiang Z, Liang J, Perry G, Hoppel C, Zhang C, Li H, Wang X. Mitofusin 2 Regulates Axonal Transport of Calpastatin to Prevent Neuromuscular Synaptic Elimination in Skeletal Muscles. Cell Metab 2018; 28:400-414.e8. [PMID: 30017354 PMCID: PMC6125186 DOI: 10.1016/j.cmet.2018.06.011] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 03/08/2018] [Accepted: 06/14/2018] [Indexed: 01/06/2023]
Abstract
Skeletal muscles undergo atrophy in response to diseases and aging. Here we report that mitofusin 2 (Mfn2) acts as a dominant suppressor of neuromuscular synaptic loss to preserve skeletal muscles. Mfn2 is reduced in spinal cords of transgenic SOD1G93A and aged mice. Through preserving neuromuscular synapses, increasing neuronal Mfn2 prevents skeletal muscle wasting in both SOD1G93A and aged mice, whereas deletion of neuronal Mfn2 produces neuromuscular synaptic dysfunction and skeletal muscle atrophy. Neuromuscular synaptic loss after sciatic nerve transection can also be alleviated by Mfn2. Mfn2 coexists with calpastatin largely in mitochondria-associated membranes (MAMs) to regulate its axonal transport. Genetic inactivation of calpastatin abolishes Mfn2-mediated protection of neuromuscular synapses. Our results suggest that, as a potential key component of a novel and heretofore unrecognized mechanism of cytoplasmic protein transport, Mfn2 may play a general role in preserving neuromuscular synapses and serve as a common therapeutic target for skeletal muscle atrophy.
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Affiliation(s)
- Luwen Wang
- Department of Pathology, Case Western Reserve University, Cleveland, OH, USA
| | - Ju Gao
- Department of Pathology, Case Western Reserve University, Cleveland, OH, USA
| | - Jingyi Liu
- Department of Pathology, Case Western Reserve University, Cleveland, OH, USA
| | - Sandra L Siedlak
- Department of Pathology, Case Western Reserve University, Cleveland, OH, USA
| | - Sandy Torres
- Department of Pathology, Case Western Reserve University, Cleveland, OH, USA
| | - Hisashi Fujioka
- Electron Microscopy Core Facility, Case Western Reserve University, Cleveland, OH, USA
| | - Mikayla L Huntley
- Department of Pathology, Case Western Reserve University, Cleveland, OH, USA
| | - Yinfei Jiang
- Department of Pathology, Case Western Reserve University, Cleveland, OH, USA
| | - Haiyan Ji
- Department of Pathology, Case Western Reserve University, Cleveland, OH, USA
| | - Tingxiang Yan
- Department of Pathology, Case Western Reserve University, Cleveland, OH, USA
| | - Micah Harland
- Department of Pathology, Case Western Reserve University, Cleveland, OH, USA
| | - Pichet Termsarasab
- Department of Pathology, Case Western Reserve University, Cleveland, OH, USA
| | - Sophia Zeng
- Department of Pathology, Case Western Reserve University, Cleveland, OH, USA
| | - Zhen Jiang
- Department of Pathology, Case Western Reserve University, Cleveland, OH, USA
| | - Jingjing Liang
- Department of Epidemiology and Biostatistics, Case Western Reserve University, Cleveland, OH, USA
| | - George Perry
- College of Sciences, University of Texas at San Antonio, San Antonio, TX, USA
| | - Charles Hoppel
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA
| | - Cheng Zhang
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN, USA
| | - Hu Li
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN, USA
| | - Xinglong Wang
- Department of Pathology, Case Western Reserve University, Cleveland, OH, USA; Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA.
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Sharp PS, Tyreman N, Jones KE, Gordon T. Crush injury to motor nerves in the G93A transgenic mouse model of amyotrophic lateral sclerosis promotes muscle reinnervation and survival of functionally intact nerve-muscle contacts. Neurobiol Dis 2018; 113:33-44. [PMID: 29409912 DOI: 10.1016/j.nbd.2018.01.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 01/19/2018] [Accepted: 01/28/2018] [Indexed: 12/13/2022] Open
Abstract
Selective survival of small motor nerve fibers and their neuromuscular contacts in the SOD1G93A transgenic mouse model of amyotrophic lateral sclerosis (ALS) suggests that smaller regenerated nerve fibers are more able to sustain reformed nerve-muscle connections as functionally intact motor units (MUs). The sciatic nerve was crushed unilaterally in SOD1G93A transgenic mice at 40 days of age and contractile forces of reinnervated muscles and their MUs were recorded at 90 days in order to determine the capacities of the nerves to regenerate and to form and retain functional neuromuscular connections. Reduced MU numbers in fast-twitch tibialis anterior, extensor digitorum longus and medial gastrocnemius muscles and the lesser reductions in slow-twitch soleus muscle of SOD1G93A transgenic mice were reversed in reinnervated muscles: there were more reinnervated MUs and their contractile forces and the muscle forces and weights increased. In line with the contrasting ability of only small not large nerve fibers to sprout to form enlarged MUs in the SOD1G93A transgenic mouse, the smaller regenerating nerve fibers formed enlarged MUs that were better able to survive. Because nerve fibers with and without muscle contacts were severed by the sciatic nerve crush injury, the conditioning lesion is untenable as the explanation for improved maintenance of reinnervated neuromuscular junctions. Elevated neurotrophic factor expression in axotomized motoneurons and/or denervated Schwann cells and the synapse withdrawal from axotomized motoneurons are other factors that, in addition to reduced size of nerve fibers reinnervating muscles, may account for increased survival and size of reinnervated MUs in ALS.
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Affiliation(s)
- P S Sharp
- Department of Psychology, and Sheffield Institute for Translational Neuroscience, Department of Neuroscience, University of Sheffield, Sheffield, United Kingdom
| | - N Tyreman
- Centre for Neuroscience, University of Alberta Edmonton, T6G 2S2, Canada
| | - K E Jones
- Centre for Neuroscience, University of Alberta Edmonton, T6G 2S2, Canada
| | - T Gordon
- Centre for Neuroscience, University of Alberta Edmonton, T6G 2S2, Canada; Faculty of Rehabilitation Medicine, University of Alberta Edmonton, T6G 2S2, Canada; Department of Surgery, Division of Plastic Reconstructive Surgery, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada.
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Yan Y, Hunter DA, Schellhardt L, Ee X, Snyder-Warwick AK, Moore AM, Mackinnon SE, Wood MD. Nerve stepping stone has minimal impact in aiding regeneration across long acellular nerve allografts. Muscle Nerve 2017; 57:260-267. [PMID: 28380694 DOI: 10.1002/mus.25659] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/02/2017] [Indexed: 12/13/2022]
Abstract
INTRODUCTION Acellular nerve allografts (ANAs) yield less consistent favorable outcomes compared with autografts for long gap reconstructions. We evaluated whether a hybrid ANA can improve 6-cm gap reconstruction. METHODS Rat sciatic nerve was transected and repaired with either 6-cm hybrid or control ANAs. Hybrid ANAs were generated using a 1-cm cellular isograft between 2.5-cm ANAs, whereas control ANAs had no isograft. Outcomes were assessed by graft gene and marker expression (n = 4; at 4 weeks) and motor recovery and nerve histology (n = 10; at 20 weeks). RESULTS Hybrid ANAs modified graft gene and marker expression and promoted modest axon regeneration across the 6-cm defect compared with control ANA (P < 0.05), but yielded no muscle recovery. Control ANAs had no appreciable axon regeneration across the 6-cm defect. DISCUSSION A hybrid ANA confers minimal motor recovery benefits for regeneration across long gaps. Clinically, the authors will continue to reconstruct long nerve gaps with autografts. Muscle Nerve 57: 260-267, 2018.
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Affiliation(s)
- Ying Yan
- Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8238, St. Louis, Missouri, 63110, USA
| | - Daniel A Hunter
- Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8238, St. Louis, Missouri, 63110, USA
| | - Lauren Schellhardt
- Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8238, St. Louis, Missouri, 63110, USA
| | - Xueping Ee
- Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8238, St. Louis, Missouri, 63110, USA
| | - Alison K Snyder-Warwick
- Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8238, St. Louis, Missouri, 63110, USA
| | - Amy M Moore
- Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8238, St. Louis, Missouri, 63110, USA
| | - Susan E Mackinnon
- Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8238, St. Louis, Missouri, 63110, USA
| | - Matthew D Wood
- Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8238, St. Louis, Missouri, 63110, USA
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Udina E, Putman CT, Harris LR, Tyreman N, Cook VE, Gordon T. Compensatory axon sprouting for very slow axonal die-back in a transgenic model of spinal muscular atrophy type III. J Physiol 2017; 595:1815-1829. [PMID: 27891608 PMCID: PMC5330916 DOI: 10.1113/jp273404] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 11/15/2016] [Indexed: 01/13/2023] Open
Abstract
KEY POINTS Smn+/- transgenic mouse is a model of the mildest form of spinal muscular atrophy. Although there is a loss of spinal motoneurons in 11-month-old animals, muscular force is maintained. This maintained muscular force is mediated by reinnervation of the denervated fibres by surviving motoneurons. The spinal motoneurons in these animals do not show an increased susceptibility to death after nerve injury and they retain their regenerative capacity. We conclude that the hypothesized immaturity of the neuromuscular system in this model cannot explain the loss of motoneurons by systematic die-back. ABSTRACT Spinal muscular atrophy (SMA) is a common autosomal recessive disorder in humans and is the leading genetic cause of infantile death. Patients lack the SMN1 gene with the severity of the disease depending on the number of copies of the highly homologous SMN2 gene. Although motoneuron death in the Smn+/- transgenic mouse model of the mildest form of SMA, SMA type III, has been reported, we have used retrograde tracing of sciatic and femoral motoneurons in the hindlimb with recording of muscle and motor unit isometric forces to count the number of motoneurons with intact neuromuscular connections. Thereby, we investigated whether incomplete maturation of the neuromuscular system induced by survival motoneuron protein (SMN) defects is responsible for die-back of axons relative to survival of motoneurons. First, a reduction of ∼30% of backlabelled motoneurons began relatively late, at 11 months of age, with a significant loss of 19% at 7 months. Motor axon die-back was affirmed by motor unit number estimation. Loss of functional motor units was fully compensated by axonal sprouting to retain normal contractile force in four hindlimb muscles (three fast-twitch and one slow-twitch) innervated by branches of the sciatic nerve. Second, our evaluation of whether axotomy of motoneurons in the adult Smn+/- transgenic mouse increases their susceptibility to cell death demonstrated that all the motoneurons survived and they sustained their capacity to regenerate their nerve fibres. It is concluded the systematic die-back of motoneurons that innervate both fast- and slow-twitch muscle fibres is not related to immaturity of the neuromuscular system in SMA.
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Affiliation(s)
- Esther Udina
- Neuroscience and Mental Health Institute, Faculty of Medicine and DentistryUniversity of AlbertaEdmontonABCanadaT6G 2S2
- Institute of Neurosciences and Department of Cell Biology, Physiology and ImmunologyUniversitat Autònoma de Barcelona, and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED)BellaterraSpain
| | - Charles T. Putman
- Neuroscience and Mental Health Institute, Faculty of Medicine and DentistryUniversity of AlbertaEdmontonABCanadaT6G 2S2
- Exercise Biochemistry Laboratory, Faculty of Physical Education and RecreationUniversity of AlbertaEdmontonABCanadaT6G 2H9
| | - Luke R. Harris
- Neuroscience and Mental Health Institute, Faculty of Medicine and DentistryUniversity of AlbertaEdmontonABCanadaT6G 2S2
- Exercise Biochemistry Laboratory, Faculty of Physical Education and RecreationUniversity of AlbertaEdmontonABCanadaT6G 2H9
| | - Neil Tyreman
- Neuroscience and Mental Health Institute, Faculty of Medicine and DentistryUniversity of AlbertaEdmontonABCanadaT6G 2S2
| | - Victoria E. Cook
- Neuroscience and Mental Health Institute, Faculty of Medicine and DentistryUniversity of AlbertaEdmontonABCanadaT6G 2S2
- Exercise Biochemistry Laboratory, Faculty of Physical Education and RecreationUniversity of AlbertaEdmontonABCanadaT6G 2H9
| | - Tessa Gordon
- Neuroscience and Mental Health Institute, Faculty of Medicine and DentistryUniversity of AlbertaEdmontonABCanadaT6G 2S2
- Division of Rehabilitation and Physical Medicine of the Faculty of Medicine and DentistryUniversity of AlbertaEdmontonABCanadaT6G 2S2
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Gordon T, Borschel GH. The use of the rat as a model for studying peripheral nerve regeneration and sprouting after complete and partial nerve injuries. Exp Neurol 2017; 287:331-347. [DOI: 10.1016/j.expneurol.2016.01.014] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 01/14/2016] [Accepted: 01/15/2016] [Indexed: 02/06/2023]
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Selective Nerve Root Transection in the Rat Produces Permanent, Partial Nerve Injury Models with Variable Levels of Functional Deficit. Plast Reconstr Surg 2017; 139:94-103. [DOI: 10.1097/prs.0000000000002874] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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12
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Comparative outcome measures in peripheral regeneration studies. Exp Neurol 2016; 287:348-357. [PMID: 27094121 DOI: 10.1016/j.expneurol.2016.04.011] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Revised: 04/09/2016] [Accepted: 04/11/2016] [Indexed: 12/25/2022]
Abstract
Traumatic peripheral nerve injuries are common and often result in partial or permanent paralysis, numbness of the affected limb, and debilitating neuropathic pain. Experimental animal models of nerve injury have utilized a diversity of outcome measures to examine functional recovery following injury. Four primary categories of outcome measures of regenerative success including retrograde labeling with counts of regenerating neurons, immunohistochemistry and histomorphometry, reinnervation of target muscles, and behavioral analysis of recovery will be reviewed. Validity of different outcome measures are discussed in context of hindlimb, forelimb, and facial nerve injury models. Severity of nerve injury will be highlighted, and comparisons between nerve crush injury and more severe transection and neuroma-in-continuity nerve injury paradigms will be evaluated. The case is made that specific outcome measures may be more sensitive to assessing functional recovery following nerve injury than others. This will be discussed in the context of the lack of association between certain outcome measures of nerve regeneration. Examples of inaccurate conclusions from specific outcome measures will also be considered. Overall, researchers must therefore take care to select appropriate outcome measures for animal nerve injury studies dependant on the specific experimental interventions and scientific questions addressed.
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Abstract
Neuromuscular diseases can affect the survival of peripheral neurons, their axons extending to peripheral targets, their synaptic connections onto those targets, or the targets themselves. Examples include motor neuron diseases such as Amyotrophic Lateral Sclerosis, peripheral neuropathies such as Charcot-Marie-Tooth diseases, myasthenias, and muscular dystrophies. Characterizing these phenotypes in mouse models requires an integrated approach, examining both the nerve and muscle histologically, anatomically, and functionally by electrophysiology. Defects observed at these levels can be related back to onset, severity, and progression, as assessed by "Quality of life measures" including tests of gross motor performance such as gait or grip strength. This chapter describes methods for assessing neuromuscular disease models in mice, and how interpretation of these tests can be complicated by the inter-relatedness of the phenotypes.
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Affiliation(s)
- Robert W Burgess
- The Jackson Laboratory, 600 Main Street, Bar Harbor, ME, 04609, USA.
| | - Gregory A Cox
- The Jackson Laboratory, 600 Main Street, Bar Harbor, ME, 04609, USA
| | - Kevin L Seburn
- The Jackson Laboratory, 600 Main Street, Bar Harbor, ME, 04609, USA
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Nerve cross-bridging to enhance nerve regeneration in a rat model of delayed nerve repair. PLoS One 2015; 10:e0127397. [PMID: 26016986 PMCID: PMC4446033 DOI: 10.1371/journal.pone.0127397] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 04/14/2015] [Indexed: 01/21/2023] Open
Abstract
There are currently no available options to promote nerve regeneration through chronically denervated distal nerve stumps. Here we used a rat model of delayed nerve repair asking of prior insertion of side-to-side cross-bridges between a donor tibial (TIB) nerve and a recipient denervated common peroneal (CP) nerve stump ameliorates poor nerve regeneration. First, numbers of retrogradely-labelled TIB neurons that grew axons into the nerve stump within three months, increased with the size of the perineurial windows opened in the TIB and CP nerves. Equal numbers of donor TIB axons regenerated into CP stumps either side of the cross-bridges, not being affected by target neurotrophic effects, or by removing the perineurium to insert 5-9 cross-bridges. Second, CP nerve stumps were coapted three months after inserting 0-9 cross-bridges and the number of 1) CP neurons that regenerated their axons within three months or 2) CP motor nerves that reinnervated the extensor digitorum longus (EDL) muscle within five months was determined by counting and motor unit number estimation (MUNE), respectively. We found that three but not more cross-bridges promoted the regeneration of axons and reinnervation of EDL muscle by all the CP motoneurons as compared to only 33% regenerating their axons when no cross-bridges were inserted. The same 3-fold increase in sensory nerve regeneration was found. In conclusion, side-to-side cross-bridges ameliorate poor regeneration after delayed nerve repair possibly by sustaining the growth-permissive state of denervated nerve stumps. Such autografts may be used in human repair surgery to improve outcomes after unavoidable delays.
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Elzinga K, Tyreman N, Ladak A, Savaryn B, Olson J, Gordon T. Brief electrical stimulation improves nerve regeneration after delayed repair in Sprague Dawley rats. Exp Neurol 2015; 269:142-53. [PMID: 25842267 DOI: 10.1016/j.expneurol.2015.03.022] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 03/23/2015] [Accepted: 03/25/2015] [Indexed: 01/09/2023]
Abstract
Functional recovery after peripheral nerve injury and surgical repair declines with time and distance because the injured neurons without target contacts (chronic axotomy) progressively lose their regenerative capacity and chronically denervated Schwann cells (SCs) atrophy and fail to support axon regeneration. Findings that brief low frequency electrical stimulation (ES) accelerates axon outgrowth and muscle reinnervation after immediate nerve surgery in rats and human patients suggest that ES might improve regeneration after delayed nerve repair. To test this hypothesis, common peroneal (CP) neurons were chronically axotomized and/or tibial (TIB) SCs and ankle extensor muscles were chronically denervated by transection and ligation in rats. The CP and TIB nerves were cross-sutured after three months and subjected to either sham or one hour 20Hz ES. Using retrograde tracing, we found that ES significantly increased the numbers of both motor and sensory neurons that regenerated their axons after a three month period of chronic CP axotomy and/or chronic TIB SC denervation. Muscle and motor unit forces recorded to determine the numbers of neurons that reinnervated gastrocnemius muscle demonstrated that ES significantly increased the numbers of motoneurons that reinnervated chronically denervated muscles. We conclude that electrical stimulation of chronically axotomized motor and sensory neurons is effective in accelerating axon outgrowth into chronically denervated nerve stumps and improving target reinnervation after delayed nerve repair. Possible mechanisms for the efficacy of ES in promoting axon regeneration and target reinnervation after delayed nerve repair include the upregulation of neurotrophic factors.
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Affiliation(s)
- Kate Elzinga
- Division of Plastic Surgery, University of Alberta, Edmonton, Alberta, Canada
| | - Neil Tyreman
- Center for Neuroscience, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Adil Ladak
- Division of Plastic Surgery, University of Alberta, Edmonton, Alberta, Canada
| | - Bohdan Savaryn
- Division of Plastic Surgery, University of Alberta, Edmonton, Alberta, Canada
| | - Jaret Olson
- Division of Plastic Surgery, University of Alberta, Edmonton, Alberta, Canada
| | - Tessa Gordon
- Center for Neuroscience, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
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Kemp SWP, Szynkaruk M, Stanoulis KN, Wood MD, Liu EH, Willand MP, Morlock L, Naidoo J, Williams NS, Ready JM, Mangano TJ, Beggs S, Salter MW, Gordon T, Pieper AA, Borschel GH. Pharmacologic rescue of motor and sensory function by the neuroprotective compound P7C3 following neonatal nerve injury. Neuroscience 2014; 284:202-216. [PMID: 25313000 DOI: 10.1016/j.neuroscience.2014.10.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 10/03/2014] [Accepted: 10/03/2014] [Indexed: 12/12/2022]
Abstract
Nerve injuries cause pain, paralysis and numbness that can lead to major disability, and newborns often sustain nerve injuries during delivery that result in lifelong impairment. Without a pharmacologic agent to enhance functional recovery from these injuries, clinicians rely solely on surgery and rehabilitation to treat patients. Unfortunately, patient outcomes remain poor despite application of the most advanced microsurgical and rehabilitative techniques. We hypothesized that the detrimental effects of traumatic neonatal nerve injury could be mitigated with pharmacologic neuroprotection, and tested whether the novel neuroprotective agent P7C3 would block peripheral neuron cell death and enhance functional recovery in a rat neonatal nerve injury model. Administration of P7C3 after sciatic nerve crush injury doubled motor and sensory neuron survival, and also promoted axon regeneration in a dose-dependent manner. Treatment with P7C3 also enhanced behavioral and muscle functional recovery, and reversed pathological mobilization of spinal microglia after injury. Our findings suggest that the P7C3 family of neuroprotective compounds may provide a basis for the development of a new neuroprotective drug to enhance recovery following peripheral nerve injury.
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Affiliation(s)
- S W P Kemp
- Department of Surgery, Division of Plastic and Reconstructive Surgery, The Hospital for Sick Children, Toronto, ON, Canada; The Hospital for Sick Children Research Institute, Program in Neuroscience and Mental Health, Toronto, ON, Canada.
| | - M Szynkaruk
- Department of Surgery, Division of Plastic and Reconstructive Surgery, The Hospital for Sick Children, Toronto, ON, Canada
| | - K N Stanoulis
- Department of Surgery, Division of Plastic and Reconstructive Surgery, The Hospital for Sick Children, Toronto, ON, Canada
| | - M D Wood
- Department of Surgery, Division of Plastic and Reconstructive Surgery, The Hospital for Sick Children, Toronto, ON, Canada; The Hospital for Sick Children Research Institute, Program in Neuroscience and Mental Health, Toronto, ON, Canada
| | - E H Liu
- Department of Surgery, Division of Plastic and Reconstructive Surgery, The Hospital for Sick Children, Toronto, ON, Canada
| | - M P Willand
- Department of Surgery, Division of Plastic and Reconstructive Surgery, The Hospital for Sick Children, Toronto, ON, Canada; The Hospital for Sick Children Research Institute, Program in Neuroscience and Mental Health, Toronto, ON, Canada
| | - L Morlock
- Department of Biochemistry, UT Southwestern Medical Center, Dallas, TX, USA
| | - J Naidoo
- Department of Biochemistry, UT Southwestern Medical Center, Dallas, TX, USA
| | - N S Williams
- Department of Biochemistry, UT Southwestern Medical Center, Dallas, TX, USA
| | - J M Ready
- Department of Biochemistry, UT Southwestern Medical Center, Dallas, TX, USA
| | - T J Mangano
- Psychoactive Drug Screening Program, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - S Beggs
- The Hospital for Sick Children Research Institute, Program in Neuroscience and Mental Health, Toronto, ON, Canada
| | - M W Salter
- The Hospital for Sick Children Research Institute, Program in Neuroscience and Mental Health, Toronto, ON, Canada
| | - T Gordon
- Department of Surgery, Division of Plastic and Reconstructive Surgery, The Hospital for Sick Children, Toronto, ON, Canada; The Hospital for Sick Children Research Institute, Program in Neuroscience and Mental Health, Toronto, ON, Canada
| | - A A Pieper
- Departments of Psychiatry, Neurology and Veterans Affairs, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
| | - G H Borschel
- Department of Surgery, Division of Plastic and Reconstructive Surgery, The Hospital for Sick Children, Toronto, ON, Canada; The Hospital for Sick Children Research Institute, Program in Neuroscience and Mental Health, Toronto, ON, Canada; University of Toronto, Department of Surgery and Institute of Biomaterials and Biomedical Engineering, Toronto, ON, Canada.
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17
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Kemp SWP, Phua PD, Stanoulis KN, Wood MD, Liu EH, Gordon T, Borschel GH. Functional recovery following peripheral nerve injury in the transgenic Thy1
-GFP rat. J Peripher Nerv Syst 2013; 18:220-31. [DOI: 10.1111/jns5.12035] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 05/25/2013] [Accepted: 05/31/2013] [Indexed: 11/27/2022]
Affiliation(s)
- Stephen W. P. Kemp
- Department of Surgery, Division of Plastic and Reconstructive Surgery; The Hospital for Sick Children; Toronto Ontario Canada
- The Hospital for Sick Children Research Institute Program in Neuroscience and Mental Health; Toronto Ontario Canada
| | - Peter D. Phua
- Department of Surgery, Division of Plastic and Reconstructive Surgery; The Hospital for Sick Children; Toronto Ontario Canada
| | - Krisanne N. Stanoulis
- Department of Surgery, Division of Plastic and Reconstructive Surgery; The Hospital for Sick Children; Toronto Ontario Canada
| | - Matthew D. Wood
- The Hospital for Sick Children Research Institute Program in Neuroscience and Mental Health; Toronto Ontario Canada
| | - Edward H. Liu
- Department of Surgery, Division of Plastic and Reconstructive Surgery; The Hospital for Sick Children; Toronto Ontario Canada
| | - Tessa Gordon
- Department of Surgery, Division of Plastic and Reconstructive Surgery; The Hospital for Sick Children; Toronto Ontario Canada
- The Hospital for Sick Children Research Institute Program in Neuroscience and Mental Health; Toronto Ontario Canada
- Division of Plastic and Reconstructive Surgery; University of Toronto; Toronto Ontario Canada
| | - Gregory H. Borschel
- Department of Surgery, Division of Plastic and Reconstructive Surgery; The Hospital for Sick Children; Toronto Ontario Canada
- The Hospital for Sick Children Research Institute Program in Neuroscience and Mental Health; Toronto Ontario Canada
- Division of Plastic and Reconstructive Surgery; University of Toronto; Toronto Ontario Canada
- University of Toronto Institute of Biomaterials and Biomedical Engineering; Toronto Ontario Canada
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Wood MD, Gordon T, Kemp SW, Liu EH, Kim H, Shoichet MS, Borschel GH. Functional motor recovery is improved due to local placement of GDNF microspheres after delayed nerve repair. Biotechnol Bioeng 2013; 110:1272-81. [DOI: 10.1002/bit.24800] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Revised: 11/19/2012] [Accepted: 11/23/2012] [Indexed: 12/11/2022]
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19
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Outcome measures of peripheral nerve regeneration. Ann Anat 2011; 193:321-33. [DOI: 10.1016/j.aanat.2011.04.008] [Citation(s) in RCA: 171] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Revised: 04/14/2011] [Accepted: 04/18/2011] [Indexed: 01/25/2023]
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Abstract
The postsurgical period during which neurons remain without target connections (chronic axotomy) and distal nerve stumps and target muscles are denervated (chronic denervation) deleteriously affects functional recovery. An autologous nerve graft and cross-suture paradigm in Sprague Dawley rats was used to systematically and independently control time of motoneuron axotomy, denervation of distal nerve sheaths, and muscle denervation to determine relative contributions of each factor to recovery failure. Tibial (TIB) nerve was cross-sutured to common peroneal (CP) nerve via a contralateral 15 mm nerve autograft to reinnervate the tibialis anterior (TA) muscle immediately or after prolonging TIB axotomy, CP autograft denervation, or TA muscle denervation. Numbers of motoneurons that reinnervated TA muscle declined exponentially from 99 ± 15 to asymptotic mean (± SE) values of 35 ± 1, 41 ± 10, and 13 ± 5, respectively. Enlarged reinnervated motor units fully compensated for reduced motoneuron numbers after prolonged axotomy and autograft denervation, but the maximal threefold enlargement did not compensate for the severe loss of regenerating nerves through chronically denervated nerve stumps and for failure of reinnervated muscle fibers to recover from denervation atrophy. Muscle force, weight, and cross-sectional area declined. Our results demonstrate that chronic denervation of the distal stump plays a key role in reduced nerve regeneration, but the denervated muscle is also a contributing factor. That chronic Schwann cell denervation within the nerve autograft reduced regeneration less than after the denervation of both CP nerve stump and TA muscle, argues that chronic muscle denervation negatively impacts nerve regeneration.
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21
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Gordon T, Tyreman N. Sprouting capacity of lumbar motoneurons in normal and hemisected spinal cords of the rat. J Physiol 2010; 588:2745-68. [PMID: 20519315 DOI: 10.1113/jphysiol.2010.190389] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Nerve sprouting to reinnervate partially denervated muscles is important in several disease and injury states. To examine the effectiveness of sprouting of active and inactive motor units (MUs) and the basis for a limit to sprouting, one of three rat lumbar spinal roots was cut under normal conditions and when the spinal cord was hemisected at T12. Muscle and MU isometric contractile forces were recorded and muscle fibres in glycogen-depleted single muscle units enumerated 23 to 380 days after surgery. Enlargement of intact MUs by sprouting was effective in compensating for up to 80% loss of innervation. For injuries that removed >70-80% of the intact MUs, muscle contractile force and weight dropped sharply. For partial denervation of <70%, all MUs increased contractile force by the same factor in both normally active muscles and muscles whose activity was reduced by T12 hemisection. Direct measurements of MU size by counting glycogen-depleted muscle fibres in physiologically and histochemically defined muscle units, provided direct evidence for a limit in MU size, whether or not the activity of the muscles was reduced by spinal cord hemisection. Analysis of spatial distribution of muscle fibres within the outer boundaries of the muscle unit demonstrated a progressive increase in fibres within the territory to the limit of sprouting when most of the muscle unit fibres were adjacent to each other. We conclude that the upper limit of MU enlargement may be explained by the reinnervation of denervated muscle fibres by axon sprouts within the spatial territory of the muscle unit, formerly distributed in a mosaic pattern.
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Affiliation(s)
- T Gordon
- Department of Surgery, Division of Plastic Surgery, The Hospital for Sick Children, 555 University Ave., Toronto, Ontario, Canada.
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22
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van Dijk JP, Schelhaas HJ, Van Schaik IN, Janssen HMHA, Stegeman DF, Zwarts MJ. Monitoring disease progression using high-density motor unit number estimation in amyotrophic lateral sclerosis. Muscle Nerve 2010; 42:239-44. [PMID: 20544934 DOI: 10.1002/mus.21680] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Johannes P van Dijk
- Department of Neurology, Clinical Neurophysiology-920, Radboud University Nijmegen Medical Centre, Donders Institute for Brain, Cognition and Behaviour, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.
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Gordon T, Tyreman N, Li S, Putman C, Hegedus J. Functional over-load saves motor units in the SOD1-G93A transgenic mouse model of amyotrophic lateral sclerosis. Neurobiol Dis 2010; 37:412-22. [DOI: 10.1016/j.nbd.2009.10.021] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Revised: 09/23/2009] [Accepted: 10/22/2009] [Indexed: 01/26/2023] Open
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Abstract
Neuromuscular diseases can affect the survival of peripheral neurons, their axons extending to peripheral targets, their synaptic connections onto those targets, or the targets themselves. Examples include motor neuron diseases such as amyotrophic lateral sclerosis, peripheral neuropathies, such as Charcot-Marie-Tooth diseases, myasthenias, and muscular dystrophies. Characterizing these phenotypes in mouse models requires an integrated approach, examining both the nerve and the muscle histologically, anatomically, and functionally by electrophysiology. Defects observed at these levels can be related back to onset, severity, and progression, as assessed by "quality-of-life measures" including tests of gross motor performance such as gait or grip strength. This chapter describes methods for assessing neuromuscular disease models in mice, and how interpretation of these tests can be complicated by the inter-relatedness of the phenotypes.
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Progressive motor unit loss in the G93A mouse model of amyotrophic lateral sclerosis is unaffected by gender. Muscle Nerve 2009; 39:318-27. [DOI: 10.1002/mus.21160] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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26
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Hegedus J, Jones KE, Gordon T. Development and use of the incremental twitch subtraction MUNE method in mice. ACTA ACUST UNITED AC 2009; 60:209-17. [DOI: 10.1016/s1567-424x(08)00022-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/15/2023]
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27
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Gordon T, Ly V, Hegedus J, Tyreman N. Early detection of denervated muscle fibers in hindlimb muscles after sciatic nerve transection in wild type mice and in the G93A mouse model of amyotrophic lateral sclerosis. Neurol Res 2008; 31:28-42. [PMID: 18768111 DOI: 10.1179/174313208x332977] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
The cell adhesion molecule N-CAM is localized to the adult neuromuscular junction but is also expressed in the extrajunctional membrane of denervated muscles concurrent with extrajunctional acetylcholine receptors. Here we used N-CAM immunohistochemistry to determine whether we could detect early denervation in hindlimb muscles of the G93A transgenic mouse model of amyotrophic lateral sclerosis (ALS). In denervated wild type mouse muscles, N-CAM immunoreactivity on the sarcolemma of all fiber types and within the sarcoplasm of only type IIA fibers was detected at day 2: approximately 30% of the muscle fibers in cross-section were fully circumscribed by N-CAM immunoreactivity and approximately 25% of fibers were incompletely circumscribed. The proportion of the latter fibers remained constant over the next 8 days as the proportions of the former fibers increased exponentially. Thereafter, fully circumscribed muscle fibers increased to a maximum by 30 days with a concomitant fall in the incompletely circumscribed fibers. Hence, early muscle denervation was detected by the incomplete circumscription of fiber membranes by N-CAM immunoreactivity with full circumscription and intracellular localization indicating more long-term denervation. In the G93A transgenic mouse, rapid denervation of fast-twitch muscles was readily detected by a corresponding proportion of muscle fibers in cross-section with positive N-CAM immunoreactivity. The proportions of incompletely and completely circumscribed muscle fibers corresponded well with the rate of decline in intact motor units and reduced muscle contractile forces. Progressively more fully circumscribed muscle fibers became evident with age. We conclude that the N-CAM immunoreactivity on muscle fiber membranes in muscle cross-sections provides a sensitive means of detecting early muscle fiber denervation.
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Affiliation(s)
- T Gordon
- Division of Physical Medicine and Rehabilitation/Centre for Neuroscience, Faculty of Medicine, University of Alberta, Edmonton, Alta T6G 2S2, Canada.
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Hegedus J, Putman CT, Tyreman N, Gordon T. Preferential motor unit loss in the SOD1 G93A transgenic mouse model of amyotrophic lateral sclerosis. J Physiol 2008; 586:3337-51. [PMID: 18467368 DOI: 10.1113/jphysiol.2007.149286] [Citation(s) in RCA: 182] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The present study investigated motor unit (MU) loss in a murine model of familial amyotrophic lateral sclerosis (ALS). The fast-twitch tibialis anterior (TA) and medial gastrocnemius (MG) muscles of transgenic SOD1(G93A) and SOD1(WT) mice were studied during the presymptomatic phase of disease progression at 60 days of age. Whole muscle maximum isometric twitch and tetanic forces were 80% lower (P < 0.01) in the TA muscles of SOD1(G93A) compared to SOD1(WT) mice. Enumeration of total MU numbers within TA muscles showed a 60% reduction (P < 0.01) within SOD1(G93A) mice (38 +/- 7) compared with SOD1(WT) controls (95 +/- 12); this was attributed to a lower proportion of the most forceful fast-fatigable (FF) MU in SOD1(G93A) mice, as seen by a significant (P < 0.01) leftward shift in the cumulative frequency histogram of single MU forces. Similar patterns of MU loss and corresponding decreases in isometric twitch force were observed in the MG. Immunocytochemical analyses of the entire cross-sectional area (CSA) of serial sections of TA muscles stained with anti-neural cell adhesion molecule (NCAM) and various monoclonal antibodies for myosin heavy chain (MHC) isoforms showed respective 65% (P < 0.01) and 28% (P < 0.05) decreases in the number of innervated IIB and IID/X muscle fibres in SOD1(G93A), which paralleled the 60% decrease (P < 0.01) in the force generating capacity of individual fibres. The loss of fast MUs was partially compensated by activity-dependent fast-to-slower fibre type transitions, as determined by increases (P < 0.04) in the CSA and proportion of IIA fibres (from 4% to 14%) and IID/X fibres (from 31% to 39%), and decreases (P < 0.001) in the CSA and proportion of type IIB fibres (from 65% to 44%). We conclude that preferential loss of IIB fibres is incomplete at 60 days of age, and is consistent with a selective albeit gradual loss of FF MUs that is not fully compensated by sprouting of the remaining motoneurons that innervate type IIA or IID/X muscle fibres. Our findings indicate that disease progression in fast-twitch muscles of SOD1(G93A) mice involves parallel processes: (1) gradual selective motor axon die-back of the FF motor units that contain large type IIB muscle fibres, and of fatigue-intermediate motor units that innervate type IID/X muscle fibres, and (2) activity-dependent conversion of motor units to those innervated by smaller motor axons innervating type IIA fatigue-resistant muscle fibres.
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Affiliation(s)
- J Hegedus
- Centre for Neuroscience, 525 Heritage Medical Research Centre, Faculty of Medicine, University of Alberta, Edmonton, AB, Canada
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Hegedus J, Putman CT, Gordon T. Time course of preferential motor unit loss in the SOD1G93A mouse model of amyotrophic lateral sclerosis. Neurobiol Dis 2007; 28:154-64. [PMID: 17766128 DOI: 10.1016/j.nbd.2007.07.003] [Citation(s) in RCA: 238] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2007] [Revised: 06/28/2007] [Accepted: 07/01/2007] [Indexed: 11/24/2022] Open
Abstract
Electromyographical analyses of pre-symptomatic motor unit loss in the SOD1 G93A transgenic mouse model of amyotrophic lateral sclerosis (ALS) have yielded contradictory findings as to the onset and time course. We recorded hindlimb muscle and motor unit isometric forces to determine motor unit number and size throughout the life span of the mice. Motor unit numbers in fast-twitch tibialis anterior, extensor digitorum longus and medial gastrocnemius muscles declined from 40 days of age, 50 days before reported overt symptoms and motoneuron loss. Motor unit numbers fell after overt symptoms in the slow-twitch soleus muscle. Muscle forces declined in parallel with motor unit numbers, indicating little or no functional compensation by sprouting. Early muscle-specific decline was due to selective preferential vulnerability of large, fast motor units, innervated by large motoneurons. Large motoneurons are hence the most vulnerable in ALS with die-back occurring prior to overt symptoms. We conclude that size of motoneurons, their axons, and their motor unit size are important determinants of motoneuron susceptibility in ALS.
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Affiliation(s)
- J Hegedus
- Centre for Neuroscience, University of Alberta, Edmonton, AB, Canada T6G 2S2
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