1
|
Personius KE, Siebert D, Koch DW, Udin SB. Blockage of neuromuscular glutamate receptors impairs reinnervation following nerve crush in adult mice. Front Cell Neurosci 2022; 16:1000218. [PMID: 36212695 PMCID: PMC9535682 DOI: 10.3389/fncel.2022.1000218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 09/02/2022] [Indexed: 11/29/2022] Open
Abstract
Motor axons in peripheral nerves are capable of regeneration following injury. However, complete recovery of motor function is rare, particularly when reinnervation is delayed. We have previously found that glutamate receptors play a crucial role in the successful innervation of muscle during mouse development. In particular, blocking N-methyl-D-aspartate (NMDA) receptor activity delays the normal elimination of excess innervation of each neuromuscular junction. Here, we use behavioral, immunohistochemical, electrophysiological, and calcium imaging methods to test whether glutamate receptors play a similar role in the transition from polyneuronal to mono-innervation and in recovery of function following peripheral nerve injury in mature muscle.
Collapse
Affiliation(s)
- Kirkwood E. Personius
- Program in Neuroscience, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, United States
- Department of Rehabilitation Science, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States
- *Correspondence: Kirkwood E. Personius,
| | - Danielle Siebert
- Program in Neuroscience, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, United States
| | - Dennis W. Koch
- Department of Kinesiology, Canisius College, Buffalo, NY, United States
| | - Susan B. Udin
- Program in Neuroscience, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, United States
- Department of Physiology and Biophysics, School of Medicine and Biomedical Sciences, Buffalo, NY, United States
| |
Collapse
|
2
|
Assis AD, Chiarotto GB, da Silva NS, Simões GF, Oliveira ALR. Pregabalin synchronizes the regeneration of nerve and muscle fibers optimizing the gait recovery of MDX dystrophic mice. FASEB J 2022; 36:e22511. [PMID: 35998000 DOI: 10.1096/fj.202200411rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 08/04/2022] [Accepted: 08/09/2022] [Indexed: 12/24/2022]
Abstract
Duchenne muscular dystrophy (DMD) is an X-linked genetic disorder induced by mutations in the dystrophin gene, leading to a degeneration of muscle fibers, triggering retrograde immunomodulatory, and degenerative events in the central nervous system. Thus, neuroprotective drugs such as pregabalin (PGB) can improve motor function by modulating plasticity, together with anti-inflammatory effects. The present work aimed to study the effects of PGB on axonal regeneration after axotomy in dystrophic and non-dystrophic mice. For that, MDX and C57BL/10 mouse strains were subjected to peripheral nerve damage and were treated with PGB (30 mg/kg/day, i.p.) for 28 consecutive days. The treatment was carried out in mice as soon as they completed 5 weeks of life, 1 week before the lesion, corresponding to the peak period of muscle degeneration in the MDX strain. Six-week-old mice were submitted to unilateral sciatic nerve crush and were sacrificed in the 9th week of age. The ipsi and contralateral sciatic nerves were processed for immunohistochemistry and qRT-PCR, evaluating the expression of proteins and gene transcripts related to neuronal and Schwann cell activity. Cranial tibial muscles were dissected for evaluation of neuromuscular junctions using α-bungarotoxin, and the myelinated axons of the sciatic nerve were analyzed by morphometry. The recovery of motor function was monitored throughout the treatment through tests of forced locomotion (rotarod) and spontaneous walking track test (Catwalk system). The results show that treatment with PGB reduced the retrograde cyclic effects of muscle degeneration/regeneration on the nervous system. This fact was confirmed after peripheral nerve injury, showing better adaptation and response of neurons and glia for rapid axonal regeneration, with efficient muscle targeting and regain of function. No side effects of PGB treatment were observed, and the expression of pro-regenerative proteins in neurons and Schwann cells was upregulated. Morphometry of the axons was in line with the preservation of motor endplates, resulting in enhanced performance of dystrophic animals. Overall, the present data indicate that pregabalin is protective and enhances regeneration of the SNP during the development of DMD, improving motor function, which can, in turn, be translated to the clinic.
Collapse
Affiliation(s)
- Alex Dias Assis
- Laboratory of Nerve Regeneration, University of Campinas - UNICAMP, Campinas, Brazil
| | | | | | | | | |
Collapse
|
3
|
Fralish Z, Lotz EM, Chavez T, Khodabukus A, Bursac N. Neuromuscular Development and Disease: Learning From in vitro and in vivo Models. Front Cell Dev Biol 2021; 9:764732. [PMID: 34778273 PMCID: PMC8579029 DOI: 10.3389/fcell.2021.764732] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 10/06/2021] [Indexed: 01/02/2023] Open
Abstract
The neuromuscular junction (NMJ) is a specialized cholinergic synaptic interface between a motor neuron and a skeletal muscle fiber that translates presynaptic electrical impulses into motor function. NMJ formation and maintenance require tightly regulated signaling and cellular communication among motor neurons, myogenic cells, and Schwann cells. Neuromuscular diseases (NMDs) can result in loss of NMJ function and motor input leading to paralysis or even death. Although small animal models have been instrumental in advancing our understanding of the NMJ structure and function, the complexities of studying this multi-tissue system in vivo and poor clinical outcomes of candidate therapies developed in small animal models has driven the need for in vitro models of functional human NMJ to complement animal studies. In this review, we discuss prevailing models of NMDs and highlight the current progress and ongoing challenges in developing human iPSC-derived (hiPSC) 3D cell culture models of functional NMJs. We first review in vivo development of motor neurons, skeletal muscle, Schwann cells, and the NMJ alongside current methods for directing the differentiation of relevant cell types from hiPSCs. We further compare the efficacy of modeling NMDs in animals and human cell culture systems in the context of five NMDs: amyotrophic lateral sclerosis, myasthenia gravis, Duchenne muscular dystrophy, myotonic dystrophy, and Pompe disease. Finally, we discuss further work necessary for hiPSC-derived NMJ models to function as effective personalized NMD platforms.
Collapse
Affiliation(s)
- Zachary Fralish
- Department of Biomedical Engineering, Pratt School of Engineering, Duke University, Durham, NC, United States
| | - Ethan M Lotz
- Department of Biomedical Engineering, Pratt School of Engineering, Duke University, Durham, NC, United States
| | - Taylor Chavez
- Department of Biomedical Engineering, Pratt School of Engineering, Duke University, Durham, NC, United States
| | - Alastair Khodabukus
- Department of Biomedical Engineering, Pratt School of Engineering, Duke University, Durham, NC, United States
| | - Nenad Bursac
- Department of Biomedical Engineering, Pratt School of Engineering, Duke University, Durham, NC, United States
| |
Collapse
|
4
|
The Neuromuscular Junction: Roles in Aging and Neuromuscular Disease. Int J Mol Sci 2021; 22:ijms22158058. [PMID: 34360831 PMCID: PMC8347593 DOI: 10.3390/ijms22158058] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 07/20/2021] [Accepted: 07/22/2021] [Indexed: 02/07/2023] Open
Abstract
The neuromuscular junction (NMJ) is a specialized synapse that bridges the motor neuron and the skeletal muscle fiber and is crucial for conversion of electrical impulses originating in the motor neuron to action potentials in the muscle fiber. The consideration of contributing factors to skeletal muscle injury, muscular dystrophy and sarcopenia cannot be restricted only to processes intrinsic to the muscle, as data show that these conditions incur denervation-like findings, such as fragmented NMJ morphology and corresponding functional changes in neuromuscular transmission. Primary defects in the NMJ also influence functional loss in motor neuron disease, congenital myasthenic syndromes and myasthenia gravis, resulting in skeletal muscle weakness and heightened fatigue. Such findings underscore the role that the NMJ plays in neuromuscular performance. Regardless of cause or effect, functional denervation is now an accepted consequence of sarcopenia and muscle disease. In this short review, we provide an overview of the pathologic etiology, symptoms, and therapeutic strategies related to the NMJ. In particular, we examine the role of the NMJ as a disease modifier and a potential therapeutic target in neuromuscular injury and disease.
Collapse
|
5
|
Zelada D, Bermedo-García F, Collao N, Henríquez JP. Motor function recovery: deciphering a regenerative niche at the neuromuscular synapse. Biol Rev Camb Philos Soc 2020; 96:752-766. [PMID: 33336525 PMCID: PMC7986695 DOI: 10.1111/brv.12675] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 11/20/2020] [Accepted: 11/25/2020] [Indexed: 12/13/2022]
Abstract
The coordinated movement of many organisms relies on efficient nerve–muscle communication at the neuromuscular junction (NMJ), a peripheral synapse composed of a presynaptic motor axon terminal, a postsynaptic muscle specialization, and non‐myelinating terminal Schwann cells. NMJ dysfunctions are caused by traumatic spinal cord or peripheral nerve injuries as well as by severe motor pathologies. Compared to the central nervous system, the peripheral nervous system displays remarkable regenerating abilities; however, this capacity is limited by the denervation time frame and depends on the establishment of permissive regenerative niches. At the injury site, detailed information is available regarding the cells, molecules, and mechanisms involved in nerve regeneration and repair. However, a regenerative niche at the final functional step of peripheral motor innervation, i.e. at the mature neuromuscular synapse, has not been deciphered. In this review, we integrate classic and recent evidence describing the cells and molecules that could orchestrate a dynamic ecosystem to accomplish successful NMJ regeneration. We propose that such a regenerative niche must ensure at least two fundamental steps for successful NMJ regeneration: the proper arrival of incoming regenerating axons to denervated postsynaptic muscle domains, and the resilience of those postsynaptic domains, in morphological and functional terms. We here describe and combine the main cellular and molecular responses involved in each of these steps as potential targets to help successful NMJ regeneration.
Collapse
Affiliation(s)
- Diego Zelada
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, Faculty of Biological Sciences, Center for Advanced Microscopy (CMA Bio-Bio), Universidad de Concepción, Casilla 160-C, Concepción, Chile
| | - Francisca Bermedo-García
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, Faculty of Biological Sciences, Center for Advanced Microscopy (CMA Bio-Bio), Universidad de Concepción, Casilla 160-C, Concepción, Chile
| | - Nicolás Collao
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, Faculty of Biological Sciences, Center for Advanced Microscopy (CMA Bio-Bio), Universidad de Concepción, Casilla 160-C, Concepción, Chile
| | - Juan P Henríquez
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, Faculty of Biological Sciences, Center for Advanced Microscopy (CMA Bio-Bio), Universidad de Concepción, Casilla 160-C, Concepción, Chile
| |
Collapse
|
6
|
Santosa KB, Keane AM, Jablonka-Shariff A, Vannucci B, Snyder-Warwick AK. Clinical relevance of terminal Schwann cells: An overlooked component of the neuromuscular junction. J Neurosci Res 2018; 96:1125-1135. [PMID: 29536564 PMCID: PMC6292684 DOI: 10.1002/jnr.24231] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 12/30/2017] [Accepted: 02/09/2018] [Indexed: 12/13/2022]
Abstract
The terminal Schwann cell (tSC), a type of nonmyelinating Schwann cell, is a significant yet relatively understudied component of the neuromuscular junction. In addition to reviewing the role tSCs play on formation, maintenance, and remodeling of the synapse, we review studies that implicate tSCs in neuromuscular diseases including spinal muscular atrophy, Miller-Fisher syndrome, and amyotrophic lateral sclerosis, among others. We also discuss the importance of these cells on degeneration and regeneration after nerve injury. Knowledge of tSC biology may improve our understanding of disease pathogenesis and help us identify new and innovative therapeutic strategies for the many patients who suffer from neuromuscular disorders and nerve injuries.
Collapse
Affiliation(s)
- Katherine B. Santosa
- Postdoctoral Research Fellow, Division of Plastic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, MO
| | - Alexandra M. Keane
- Medical Student, Washington University School of Medicine, St. Louis, MO
| | - Albina Jablonka-Shariff
- Research Scientist, Division of Plastic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, MO
| | - Bianca Vannucci
- Medical Student, Washington University School of Medicine, St. Louis, MO
| | - Alison K. Snyder-Warwick
- Assistant Professor, Division of Plastic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, MO
| |
Collapse
|
7
|
Abstract
The schwann cells of the peripheral nervous system are indispensable for the formation, maintenance, and modulation of synapses over the life cycle. They not only recognize neuron-glia signaling molecules, but also secrete gliotransmitters. Through these processes, they regulate neuronal excitability and thus the release of neurotransmitters from the nerve terminal at the neuromuscular junction. Gliotransmitters strongly affect nerve communication, and their secretion is mainly triggered by synchronized Ca2+ signaling, implicating Ca2+ waves in synapse function. Reciprocally, neurotransmitters released during synaptic activity can evoke increases in intracellular Ca2+ levels. A reconsideration of the interplay between the two main types of cells in the nervous system is due, as the concept of nervous system activity comprising only neuron-neuron and neuron-muscle action has become untenable. A more precise understanding of the roles of schwann cells in nerve-muscle signaling is required.
Collapse
Affiliation(s)
- Sujin Hyung
- Department of Mechanical and Aerospace Engineering, Seoul National University, San 56-1, Shilim-dong, Gwanak-gu, Seoul, 08826, Korea
- BK21 Plus Transformative Training Program for Creative Mechanical and Aerospace Engineers, Seoul National University, San 56-1, Shilim-dong, Gwanak-gu, Seoul, 08826, Korea
| | - Kyuhwan Jung
- Graduate Program of Nano Science and Technology, Graduate School of Yonsei University, 50-1 Yonsei Ro, Seodaemun-gu, Seoul, 03722, Korea
| | - Sung-Rae Cho
- Graduate Program of Nano Science and Technology, Graduate School of Yonsei University, 50-1 Yonsei Ro, Seodaemun-gu, Seoul, 03722, Korea
- Department and Research Institute of Rehabilitation Medicine, Yonsei University College of Medicine, 50-1 Yonsei Ro, Seodaemun-gu, Seoul, 03722, Korea
| | - Noo Li Jeon
- Department of Mechanical and Aerospace Engineering, Seoul National University, San 56-1, Shilim-dong, Gwanak-gu, Seoul, 08826, Korea
| |
Collapse
|
8
|
Tierney M, Garcia C, Bancone M, Sacco A, Personius KE. Innervation of dystrophic muscle after muscle stem cell therapy. Muscle Nerve 2016; 54:763-8. [PMID: 26998682 DOI: 10.1002/mus.25115] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/17/2016] [Indexed: 12/20/2022]
Abstract
INTRODUCTION Duchenne muscular dystrophy (DMD) is caused by loss of the structural protein, dystrophin, resulting in muscle fragility. Muscle stem cell (MuSC) transplantation is a potential therapy for DMD. It is unknown whether donor-derived muscle fibers are structurally innervated. METHODS Green fluorescent protein (GFP)-expressing MuSCs were transplanted into the tibials anterior of adult dystrophic mdx/mTR mice. Three weeks later the neuromuscular junction was labeled by immunohistochemistry. RESULTS The percent overlap between pre- and postsynaptic immunolabeling was greater in donor-derived GFP(+) myofibers, and fewer GFP(+) myofibers were identified as denervated compared with control GFP(-) fibers (P = 0.001 and 0.03). GFP(+) fibers also demonstrated acetylcholine receptor fragmentation and expanded endplate area, indicators of muscle reinnervation (P = 0.008 and 0.033). CONCLUSION It is unclear whether GFP(+) fibers are a result of de novo synthesis or fusion with damaged endogenous fibers. Either way, donor-derived fibers demonstrate clear histological innervation. Muscle Nerve 54: 763-768, 2016.
Collapse
Affiliation(s)
- Matthew Tierney
- Development, Aging and Regeneration Program, Sanford Children's Health Research Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Christina Garcia
- Department of Rehabilitation Science, School of Public Health and Health Professions, Kimball Tower, 3435 Main Street, Buffalo, New York, 14214-3079, USA
| | - Matthew Bancone
- Department of Rehabilitation Science, School of Public Health and Health Professions, Kimball Tower, 3435 Main Street, Buffalo, New York, 14214-3079, USA
| | - Alessandra Sacco
- Development, Aging and Regeneration Program, Sanford Children's Health Research Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Kirkwood E Personius
- Department of Rehabilitation Science, School of Public Health and Health Professions, Kimball Tower, 3435 Main Street, Buffalo, New York, 14214-3079, USA. .,Program in Neuroscience, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, USA.
| |
Collapse
|
9
|
Pratt SJP, Valencia AP, Le GK, Shah SB, Lovering RM. Pre- and postsynaptic changes in the neuromuscular junction in dystrophic mice. Front Physiol 2015; 6:252. [PMID: 26441672 PMCID: PMC4563167 DOI: 10.3389/fphys.2015.00252] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 08/28/2015] [Indexed: 01/05/2023] Open
Abstract
Duchenne muscular dystrophy (DMD) is a devastating neuromuscular disease in which weakness, increased susceptibility to muscle injury, and inadequate repair appear to underlie the pathology. While most attention has focused within the muscle fiber, we recently demonstrated in mdx mice (murine model for DMD) significant morphologic alterations at the motor endplate of the neuromuscular junction (NMJ) and corresponding NMJ transmission failure after injury. Here we extend these initial observations at the motor endplate to gain insight into the pre- vs. postsynaptic morphology, as well as the subsynaptic nuclei in healthy (WT) vs. mdx mice. We quantified the discontinuity and branching of the terminal nerve in adult mice. We report mdx- and age-dependent changes for discontinuity and an increase in branching when compared to WT. To examine mdx- and age-dependent changes in the relative localization of pre- and postsynaptic structures, we calculated NMJ occupancy, defined as the ratio of the footprint occupied by presynaptic vesicles vs. that of the underlying motor endplate. The normally congruent coupling between presynaptic and postsynaptic morphology was altered in mdx mice, independent of age. Finally we found an almost two-fold increase in the number of nuclei and an increase in density (nuclei/area) underlying the NMJ. These outcomes suggest substantial remodeling of the NMJ during dystrophic progression. This remodeling reflects plasticity in both pre- and postsynaptic contributors to NMJ structure, and thus perhaps also NM transmission and muscle function.
Collapse
Affiliation(s)
- Stephen J P Pratt
- Department of Orthopaedics, University of Maryland School of Medicine Baltimore, MD, USA
| | - Ana P Valencia
- Department of Orthopaedics, University of Maryland School of Medicine Baltimore, MD, USA ; Department of Kinesiology, University of Maryland School of Public Health College Park, MD, USA
| | - Gloribel K Le
- Department of Orthopaedics, University of Maryland School of Medicine Baltimore, MD, USA
| | - Sameer B Shah
- Departments of Orthopaedic Surgery and Bioengineering, University of California San Diego, La Jolla, CA, USA
| | - Richard M Lovering
- Department of Orthopaedics, University of Maryland School of Medicine Baltimore, MD, USA
| |
Collapse
|
10
|
Ko CP, Robitaille R. Perisynaptic Schwann Cells at the Neuromuscular Synapse: Adaptable, Multitasking Glial Cells. Cold Spring Harb Perspect Biol 2015; 7:a020503. [PMID: 26430218 PMCID: PMC4588062 DOI: 10.1101/cshperspect.a020503] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The neuromuscular junction (NMJ) is engineered to be a highly reliable synapse to carry the control of the motor commands of the nervous system over the muscles. Its development, organization, and synaptic properties are highly structured and regulated to support such reliability and efficacy. Yet, the NMJ is also highly plastic, able to react to injury and adapt to changes. This balance between structural stability and synaptic efficacy on one hand and structural plasticity and repair on another hand is made possible by the intricate regulation of perisynaptic Schwann cells, glial cells at this synapse. They regulate both the efficacy and structural plasticity of the NMJ in a dynamic, bidirectional manner owing to their ability to decode synaptic transmission and by their interactions via trophic-related factors.
Collapse
Affiliation(s)
- Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520
| | - Richard Robitaille
- Département de Neurosciences, Université de Montréal, Montréal, Québec H3C 3J7, Canada Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| |
Collapse
|
11
|
Schaakxs D, Kalbermatten DF, Raffoul W, Wiberg M, Kingham PJ. Regenerative cell injection in denervated muscle reduces atrophy and enhances recovery following nerve repair. Muscle Nerve 2013; 47:691-701. [DOI: 10.1002/mus.23662] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/27/2012] [Indexed: 12/17/2022]
Affiliation(s)
| | - Daniel F. Kalbermatten
- Department of Plastic; Reconstructive and Aesthetic Surgery; University Hospital of Basel; Basel; Switzerland
| | - Wassim Raffoul
- Division of Plastic; Reconstructive and Aesthetic Surgery; CHUV; University Hospital of Lausanne; Lausanne; Switzerland
| | | | - Paul J. Kingham
- Department of Integrative Medical Biology; Section for Anatomy; Umeå University; Umeå SE-901 87; Sweden
| |
Collapse
|
12
|
Personius KE, Parker SD. TrkB expression at the neuromuscular junction is reduced during aging. Muscle Nerve 2012. [PMID: 23180620 DOI: 10.1002/mus.23616] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
INTRODUCTION Full-length tyrosine kinase B (TrkB.FL) and truncated TrkB (TrkB.t1) receptors are colocalized with acetylcholine receptors (AChRs) at the neuromuscular junction. We have recently shown that reduced TrkB expression leads to age-related alterations in AChR structure, neurotransmission failure, and muscle weakness. METHODS We investigated whether TrkB expression is reduced in the soleus muscle during aging. RESULTS TrkB protein expression was decreased in senescent (24-month-old) compared with 3-12-month-old mice. Loss of TrkB expression was concurrent with age-related changes in AChR morphology. Changes in mRNA levels did not correlate with protein expression, because TrkB.FL copy number was increased in the senescent soleus. No change was seen in TrkB.t1 levels. CONCLUSIONS The results suggest that reduced TrkB expression during aging may result from reduced TrkB.FL mRNA translation or increased TrkB protein turnover. Thus, maintaining adequate TrkB signaling is a potential therapeutic tool to improve muscle function during senescence.
Collapse
Affiliation(s)
- Kirkwood E Personius
- Program in Neuroscience, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, USA.
| | | |
Collapse
|
13
|
Neuron-glia interactions: the roles of Schwann cells in neuromuscular synapse formation and function. Biosci Rep 2012; 31:295-302. [PMID: 21517783 DOI: 10.1042/bsr20100107] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The NMJ (neuromuscular junction) serves as the ultimate output of the motor neurons. The NMJ is composed of a presynaptic nerve terminal, a postsynaptic muscle and perisynaptic glial cells. Emerging evidence has also demonstrated an existence of perisynaptic fibroblast-like cells at the NMJ. In this review, we discuss the importance of Schwann cells, the glial component of the NMJ, in the formation and function of the NMJ. During development, Schwann cells are closely associated with presynaptic nerve terminals and are required for the maintenance of the developing NMJ. After the establishment of the NMJ, Schwann cells actively modulate synaptic activity. Schwann cells also play critical roles in regeneration of the NMJ after nerve injury. Thus, Schwann cells are indispensable for formation and function of the NMJ. Further examination of the interplay among Schwann cells, the nerve and the muscle will provide insights into a better understanding of mechanisms underlying neuromuscular synapse formation and function.
Collapse
|
14
|
Kulakowski SA, Parker SD, Personius KE. Reduced TrkB expression results in precocious age-like changes in neuromuscular structure, neurotransmission, and muscle function. J Appl Physiol (1985) 2011; 111:844-52. [PMID: 21737823 DOI: 10.1152/japplphysiol.00070.2011] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Acute blockade of signaling through the tyrosine kinase receptor B (TrkB) attenuates neuromuscular transmission and fragments postsynaptic acetylcholine receptors (AChRs) in adult mice, suggesting that TrkB signaling is a key regulator of neuromuscular function. Using immunohistochemical, histological, and in vitro muscle contractile techniques, we tested the hypothesis that constitutively reduced TrkB expression would disrupt neuromuscular pre- and postsynaptic structure, neurotransmission, muscle fiber size, and muscle function in the soleus muscle of 6- to 8-mo-old TrkB⁺/⁻ mice compared with age-matched littermates. Age-like expansion of postsynaptic AChR area, AChR fragmentation, and denervation was observed in TrkB⁺/⁻ mice similar to that found in 24-mo-old wild-type mice. Neurotransmission failure was increased in TrkB⁺/⁻ mice, suggesting that these morphologic changes were sufficient to alter synaptic function. Reduced TrkB expression resulted in decreased muscle strength and fiber cross-sectional area. Immunohistochemical and muscle retrograde labeling experiments show that motor neuron number and size are unaffected in TrkB⁺/⁻ mice. These results suggest that TrkB- signaling at the neuromuscular junction plays a role in synaptic stabilization, neurotransmission, and muscle function and may impact the aging process of sarcopenia.
Collapse
Affiliation(s)
- Scott A Kulakowski
- Program in Neuroscience, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, USA
| | | | | |
Collapse
|
15
|
Stillwell E, Vitale J, Zhao Q, Beck A, Schneider J, Khadim F, Elson G, Altaf A, Yehia G, Dong JH, Liu J, Mark W, Bhaumik M, Grange R, Fraidenraich D. Blastocyst injection of wild type embryonic stem cells induces global corrections in mdx mice. PLoS One 2009; 4:e4759. [PMID: 19277212 PMCID: PMC2653195 DOI: 10.1371/journal.pone.0004759] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Accepted: 02/10/2009] [Indexed: 11/23/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is an incurable neuromuscular degenerative disease, caused by a mutation in the dystrophin gene. Mdx mice recapitulate DMD features. Here we show that injection of wild-type (WT) embryonic stem cells (ESCs) into mdx blastocysts produces mice with improved pathology and function. A small fraction of WT ESCs incorporates into the mdx mouse nonuniformly to upregulate protein levels of dystrophin in the skeletal muscle. The chimeric muscle shows reduced regeneration and restores dystrobrevin, a dystrophin-related protein, in areas with high and with low dystrophin content. WT ESC injection increases the amount of fat in the chimeras to reach WT levels. ESC injection without dystrophin does not prevent the appearance of phenotypes in the skeletal muscle or in the fat. Thus, dystrophin supplied by the ESCs reverses disease in mdx mice globally in a dose-dependent manner.
Collapse
MESH Headings
- Animals
- Blastocyst
- Chimera
- Dystrophin/genetics
- Dystrophin/physiology
- Dystrophin-Associated Proteins/analysis
- Embryo Transfer
- Embryonic Stem Cells/transplantation
- Female
- Genetic Therapy/methods
- Lac Operon
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Inbred mdx
- Microinjections
- Muscle, Skeletal/chemistry
- Muscle, Skeletal/pathology
- Muscle, Skeletal/physiopathology
- Muscular Dystrophy, Animal/embryology
- Muscular Dystrophy, Animal/pathology
- Muscular Dystrophy, Animal/physiopathology
- Muscular Dystrophy, Animal/therapy
- Muscular Dystrophy, Duchenne
- Regeneration
Collapse
Affiliation(s)
- Elizabeth Stillwell
- Department of Cell Biology and Molecular Medicine, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey, United States of America
| | - Joseph Vitale
- Department of Cell Biology and Molecular Medicine, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey, United States of America
| | - Qingshi Zhao
- Department of Cell Biology and Molecular Medicine, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey, United States of America
| | - Amanda Beck
- Department of Cell Biology and Molecular Medicine, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey, United States of America
| | - Joel Schneider
- Department of Cell Biology and Molecular Medicine, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey, United States of America
| | - Farah Khadim
- Department of Cell Biology and Molecular Medicine, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey, United States of America
| | - Genie Elson
- Department of Cell Biology and Molecular Medicine, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey, United States of America
| | - Aneela Altaf
- Department of Cell Biology and Molecular Medicine, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey, United States of America
| | - Ghassan Yehia
- Department of Cell Biology and Molecular Medicine, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey, United States of America
| | - Jia-hui Dong
- Developmental Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
| | - Jing Liu
- Developmental Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
| | - Willie Mark
- Developmental Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
| | - Mantu Bhaumik
- Department of Pediatrics, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, New Jersey, United States of America
| | - Robert Grange
- Department of Human Nutrition, Foods and Exercise, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, United States of America
| | - Diego Fraidenraich
- Department of Cell Biology and Molecular Medicine, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey, United States of America
- * E-mail:
| |
Collapse
|
16
|
Ghedini PC, Viel TA, Honda L, Avellar MCW, Godinho RO, Lima-Landman MTR, Lapa AJ, Souccar C. Increased expression of acetylcholine receptors in the diaphragm muscle of MDX mice. Muscle Nerve 2009; 38:1585-94. [PMID: 19016551 DOI: 10.1002/mus.21183] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The absence of dystrophin in Duchenne muscular dystrophy (DMD) and in the mutant mdx mouse causes muscle degeneration and disruption of the neuromuscular junction. Based on evidence from the denervation-like properties of these muscles, we assessed the ligand-binding constants of nicotinic acetylcholine receptors (nAChRs) and the mRNA expression of individual subunits in membrane preparations of diaphragm muscles from adult (4-month-old) and aged (20-month-old) control and mdx mice. The concentration of nAChRs as determined by the maximal specific [(125)I]-alpha-bungarotoxin binding (Bmax) in the muscle membranes did not change with aging in both animal strains. When compared to age-matched control groups, the Bmax in mdx muscles was increased by 65% in adults, and by 103% in aged mice with no alteration of toxin affinity for nAChRs. Reverse-transcription polymerase chain reaction assays showed that mRNA transcripts for the nAChR alpha1, gamma, alpha7, and beta2, but not the epsilon subunits, were more abundant in mdx than in control muscles. The results indicate increased expression of extrajunctional nAChRs in the mdx diaphragm and reflect impairment of nAChR regulation in dystrophin-deficient muscles. These observations may be related to the resistance to nondepolarizing muscle relaxants and the high sensitivity to depolarizing agents reported in DMD patients.
Collapse
Affiliation(s)
- Paulo C Ghedini
- Department of Pharmacology, Natural Products Section, Universidade Federal de São Paulo, 04044-020, Rua Três de Maio 100, São Paulo, SP, Brazil
| | | | | | | | | | | | | | | |
Collapse
|
17
|
Feng Z, Ko CP. The Role of Glial Cells in the Formation and Maintenance of the Neuromuscular Junction. Ann N Y Acad Sci 2008; 1132:19-28. [DOI: 10.1196/annals.1405.016] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
18
|
Reliability of neuromuscular transmission and how it is maintained. HANDBOOK OF CLINICAL NEUROLOGY 2008; 91:27-101. [PMID: 18631840 DOI: 10.1016/s0072-9752(07)01502-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
19
|
McCarthy JJ, Esser KA, Andrade FH. MicroRNA-206 is overexpressed in the diaphragm but not the hindlimb muscle of mdx mouse. Am J Physiol Cell Physiol 2007; 293:C451-7. [PMID: 17459947 DOI: 10.1152/ajpcell.00077.2007] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
MicroRNAs are highly conserved, noncoding RNAs involved in posttranscriptional gene silencing. MicroRNAs have been shown to be involved in a range of biological processes, including myogenesis and muscle regeneration. The objective of this study was to test the hypothesis that microRNA expression is altered in dystrophic muscle, with the greatest change occurring, of the muscles examined, in the diaphragm. The expression of the muscle-enriched microRNAs was determined in the soleus, plantaris, and diaphragm muscles of control and dystrophin-deficient ( mdx) mice by semiquantitative PCR. In the soleus and plantaris, expression of the mature microRNA 133a (miR-133a) and miR-206, respectively, was decreased by ∼25%, whereas in the diaphragm, miR-206 expression increased by 4.5-fold relative to control. The increased expression of miR-206 in the mdx diaphragm was paralleled by a 4.4-fold increase in primary miRNA-206 (pri-miRNA-206) transcript level. Expression of Myod1 was elevated 2.7-fold only in the mdx diaphragm, consistent with an earlier finding demonstrating Myod1 can activate pri-miRNA-206 transcription. Transcript levels of Drosha and Dicer, major components of microRNA biogenesis pathway, were unchanged in mdx muscle, suggesting the pathway is not altered under dystrophic conditions. Previous in vitro analysis found miR-206 was capable of repressing utrophin expression; however, under dystrophic conditions, both utrophin transcript and protein levels were significantly increased by 69% and 3.9-fold, respectively, a finding inconsistent with microRNA regulation. These results are the first to report alterations in expression of muscle-enriched microRNAs in skeletal muscle of the mdx mouse, suggesting microRNAs may have a role in the pathophysiology of muscular dystrophy.
Collapse
Affiliation(s)
- John J McCarthy
- Dept. of Physiology, University of Kentucky Medical Center, 800 Rose St., Lexington, KY 40536-0298, USA.
| | | | | |
Collapse
|
20
|
Berry SE, Liu J, Chaney EJ, Kaufman SJ. Multipotential mesoangioblast stem cell therapy in the mdx/utrn-/- mouse model for Duchenne muscular dystrophy. Regen Med 2007; 2:275-88. [PMID: 17511564 DOI: 10.2217/17460751.2.3.275] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Background: Duchenne muscular dystrophy is a progressive, lethal muscle-wasting disease for which there is no treatment. Materials & methods: We have isolated wild-type mesoangioblasts from aorta and tested their effectiveness in alleviating severe muscle disease in the dystrophin/utrophin knockout (mdx/utrn-/-) mouse model for Duchenne muscular dystrophy. Results: Mesoangioblast clones express Sca-1 and Flk-1 and differentiate into smooth and skeletal muscle, glial cells and adipocytes in vitro. Mesoangioblasts proliferate in vivo, incorporate into muscle fibers, form new fibers, and promote synthesis of dystrophin and utrophin. Muscle fibers that have incorporated mesoangioblasts, as well as surrounding fibers, are protected from damage, with approximately 50-fold less damage than fibers in muscle injected with saline. Some mesoangioblasts localize beneath the basal lamina and express c-met, whereas others differentiate into smooth muscle cells at the periphery of vessels and express α-smooth muscle actin. In mdx/utrn-/- muscle, some mesoangioblasts also form Schwann cells. Discussion & conclusion: Mesoangioblasts differentiate into multiple cell types damaged during the progression of severe muscle disease and protect fibers from damage. As such, they are good candidates for therapy of Duchenne muscular dystrophy and perhaps other neuromuscular diseases.
Collapse
Affiliation(s)
- Suzanne E Berry
- University of Illinois, Department of Cell and Developmental Biology, 601 South Goodwin Avenue, Urbana, IL 61801, USA
| | | | | | | |
Collapse
|
21
|
Marques MJ, Matsumura CY, Santo Neto H. Alterations in the permeability of dystrophic fibers during neuromuscular junction development. ACTA BIOLOGICA HUNGARICA 2007; 58:1-9. [PMID: 17385539 DOI: 10.1556/abiol.58.2007.1.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In the mdx mice, lack of dystrophin leads to increases in calcium influx and myonecrosis, followed by muscle regeneration. Synapse elimination is faster in mdx than in controls, suggesting that increases in calcium influx during development could be involved. In the present study, we evaluated whether dystrophic fibers display changes in permeability to Evans Blue Dye (EBD) during development of the neuromuscular junction. EBD is a sensitive label for the early detection of increased myofiber permeability and sarcolemmal damage. After intraperitoneal injection of EBD, sternomastoid (STN) and tibialis anterior (T. anterior) muscles were analyzed with fluorescence microscopy. At 01, 07 and 14 days of age, STN and TA mdx myofibers were not stained with EBD. At 21 days of age, positive labeling of TA and STN mdx myofibers was seen, suggesting permeability modification and myonecrosis. Adult muscles showed a decrease (T. anterior) or no changes (STN) in the amount of EBD-positive fibers. These results suggest that there is no sarcolemmal damage detected by EBD during development of dystrophic neuromuscular junctions and other factors may contribute to the earlier synapse elimination seen in dystrophic muscle.
Collapse
Affiliation(s)
- Maria Julia Marques
- Departamento de Anatomia, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo 13083-970, Brazil.
| | | | | |
Collapse
|
22
|
Marques MJ, Pertille A, Carvalho CLT, Santo Neto H. Acetylcholine Receptor Organization at the Dystrophic Extraocular Muscle Neuromuscular Junction. Anat Rec (Hoboken) 2007; 290:846-54. [PMID: 17492672 DOI: 10.1002/ar.20525] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Spared extraocular muscles of dystrophic mice are not subjected to regeneration process and can be used to verify whether the lack of dystrophin per se could cause changes in acetylcholine receptor (AChR) distribution. In the present study, rectus and oblique (spared) and retractor bulbi (nonspared) muscles were dissected from adult control (C57Bl/10) and mdx mice. AChRs and nerve terminals were labeled with rhodamine-alpha-bungarotoxin and anti-NF200-IgG-FITC, respectively, and visualized by confocal microscopy. Rectus and oblique muscles presented 0.5% central nucleation, while retractor bulbi had central nucleation in 45% of muscle fibers. In mdx rectus, AChRs were distributed in branches in 99% of the junctions examined (n = 200), similar to that observed for controls. Nerve terminals covered the AChR branches in 100% of the junctions examined. In control retractor bulbi, AChRs were distributed in regular branches. In mdx retractor bulbi, multiple fragmented islands of receptors were seen in 56% of the endplates examined (n = 200). These results suggest that the lack of dystrophin per se does not influence the distribution of acetylcholine receptors at the neuromuscular junction of spared extraocular muscles.
Collapse
MESH Headings
- Animals
- Bungarotoxins
- Disease Models, Animal
- Dystrophin/deficiency
- Dystrophin/genetics
- Dystrophin/metabolism
- Fluorescent Antibody Technique
- Fluorescent Dyes
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Inbred mdx
- Microscopy, Confocal
- Muscle, Skeletal/innervation
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscular Dystrophy, Animal/metabolism
- Muscular Dystrophy, Animal/pathology
- Muscular Dystrophy, Duchenne/metabolism
- Muscular Dystrophy, Duchenne/pathology
- Neurofilament Proteins/metabolism
- Neuromuscular Junction/metabolism
- Presynaptic Terminals/metabolism
- Receptors, Cholinergic/metabolism
- Regeneration
- Rhodamines
Collapse
Affiliation(s)
- Maria Julia Marques
- Departamento de Anatomia, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Campinas, São Paulo 13083-970, Brazil. marques@.unicamp.br
| | | | | | | |
Collapse
|
23
|
Personius KE, Sawyer RP. Variability and failure of neurotransmission in the diaphragm of mdx mice. Neuromuscul Disord 2006; 16:168-77. [PMID: 16483776 DOI: 10.1016/j.nmd.2006.01.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2005] [Revised: 12/16/2005] [Accepted: 01/06/2006] [Indexed: 11/18/2022]
Abstract
Loss of specific muscle force and evidence of myopathy are present in the diaphragm of mdx mice by 4 weeks of age. The neuromuscular junction of dystrophic muscle also shows structural abnormalities at this age. Whether these structural alterations result in neural transmission abnormalities is currently unclear, particularly at physiological firing frequencies. Thus, we investigated the extent of neurotransmission variability and failure during 35 and 100 Hz stimulation in the diaphragm of 6 to 8-month-old mdx mice in comparison to age-matched controls. Neurotransmission failure was similar across groups at both stimulation frequencies, despite the presence of disrupted post-synaptic acetylcholine receptors (AChRs). Neural transmission variability, however, measured by comparing variation in force production during direct muscle stimulation compared to variation in force production during phrenic nerve stimulation was significantly greater in dystrophic muscle. Together, these results suggest that neurotransmission is maintained at physiologic firing frequencies in dystrophic muscle, but the precision of neurotransmission is attenuated. A reduced density of functional AChRs likely underlies the increase in neurotransmission variability.
Collapse
Affiliation(s)
- Kirkwood E Personius
- Department of Rehabilitation Science, School of Public Health and Health Professions, University at Buffalo, Kimball Tower Rm. 515, 3435 Main St., Buffalo, NY 14214-3079, USA.
| | | |
Collapse
|
24
|
Marques MJ, Pereira ECL, Minatel E, Neto HS. Nerve-terminal and Schwann-cell response after nerve injury in the absence of nitric oxide. Muscle Nerve 2006; 34:225-31. [PMID: 16708367 DOI: 10.1002/mus.20576] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Dystrophic muscles show alterations in the dystrophin-glycoprotein complex and a lack of neuronal nitric oxide (NO) synthase. In mdx mice, presynaptic expression of neuronal NO synthase is decreased, suggesting that presynaptic signaling may be altered in dystrophic muscle. In this study, we examined the nerve-terminal and Schwann-cell responses after a crush lesion in control and NO-deficient mice. Seven days after nerve crush, 24% of control neuromuscular junctions (n = 200) showed ultraterminal sprouts, whereas in NO-deficient mice this frequency was 28.5% (n = 217; P > 0.05 compared to controls; chi-square test). Schwann-cell response did not change in the absence of NO, after a nerve lesion of 7-day duration. Fourteen days after the lesion, nerve terminals sprouted and Schwann cells showed an extensive network of processes away from the synaptic site in controls. In the absence of NO, there was a dramatic decrease in nerve-terminal sprouting and Schwann-cell processes failed to extend away from the endplate. These results show that NO is involved in the nerve-terminal and Schwann-cell response to nerve injury. They also suggest that presynaptic molecular signaling may be impaired in dystrophic muscles, and this could influence the innervation and survival of newly formed myofibers generated by cell-mediated therapies.
Collapse
Affiliation(s)
- Maria Julia Marques
- Department of Anatomy, Institute of Biology, State University of Campinas (Unicamp), Campinas, SP 13083-970, Brazil.
| | | | | | | |
Collapse
|