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Bermedo-García F, Zelada D, Martínez E, Tabares L, Henríquez JP. Functional regeneration of the murine neuromuscular synapse relies on long-lasting morphological adaptations. BMC Biol 2022; 20:158. [PMID: 35804361 PMCID: PMC9270767 DOI: 10.1186/s12915-022-01358-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 05/05/2022] [Indexed: 12/04/2022] Open
Abstract
Background In a broad variety of species, muscle contraction is controlled at the neuromuscular junction (NMJ), the peripheral synapse composed of a motor nerve terminal, a muscle specialization, and non-myelinating terminal Schwann cells. While peripheral nerve damage leads to successful NMJ reinnervation in animal models, muscle fiber reinnervation in human patients is largely inefficient. Interestingly, some hallmarks of NMJ denervation and early reinnervation in murine species, such as fragmentation and poly-innervation, are also phenotypes of aged NMJs or even of unaltered conditions in other species, including humans. We have reasoned that rather than features of NMJ decline, such cellular responses could represent synaptic adaptations to accomplish proper functional recovery. Here, we have experimentally tackled this idea through a detailed comparative study of the short- and long-term consequences of irreversible (chronic) and reversible (partial) NMJ denervation in the convenient cranial levator auris longus muscle. Results Our findings reveal that irreversible muscle denervation results in highly fragmented postsynaptic domains and marked ectopic acetylcholine receptor clustering along with significant terminal Schwann cells sprouting and progressive detachment from the NMJ. Remarkably, even though reversible nerve damage led to complete reinnervation after 11 days, we found that more than 30% of NMJs are poly-innervated and around 65% of postsynaptic domains are fragmented even 3 months after injury, whereas synaptic transmission is fully recovered two months after nerve injury. While postsynaptic stability was irreversibly decreased after chronic denervation, this parameter was only transiently affected by partial NMJ denervation. In addition, we found that a combination of morphometric analyses and postsynaptic stability determinations allows discriminating two distinct forms of NMJ fragmentation, stable-smooth and unstable-blurred, which correlate with their regeneration potential. Conclusions Together, our data unveil that reversible nerve damage imprints a long-lasting reminiscence in the NMJ that results in the rearrangement of its cellular components. Instead of being predictive of NMJ decline, these traits may represent an efficient adaptive response for proper functional recovery. As such, these features are relevant targets to be considered in strategies aimed to restore motor function in detrimental conditions for peripheral innervation. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-022-01358-4.
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Affiliation(s)
- Francisca Bermedo-García
- Laboratory of Neuromuscular Studies (NeSt Lab), Group for the Study of Developmental Processes (GDeP), Department of Cell Biology, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile
| | - Diego Zelada
- Laboratory of Neuromuscular Studies (NeSt Lab), Group for the Study of Developmental Processes (GDeP), Department of Cell Biology, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile
| | - Esperanza Martínez
- Laboratory of Neuromuscular Studies (NeSt Lab), Group for the Study of Developmental Processes (GDeP), Department of Cell Biology, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile
| | - Lucía Tabares
- Department of Medical Physiology and Biophysics, School of Medicine, Universidad de Sevilla, Sevilla, Spain
| | - Juan Pablo Henríquez
- Laboratory of Neuromuscular Studies (NeSt Lab), Group for the Study of Developmental Processes (GDeP), Department of Cell Biology, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile.
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Balch MHH, Harris H, Chugh D, Gnyawali S, Rink C, Nimjee SM, Arnold WD. Ischemic stroke-induced polyaxonal innervation at the neuromuscular junction is attenuated by robot-assisted mechanical therapy. Exp Neurol 2021; 343:113767. [PMID: 34044000 DOI: 10.1016/j.expneurol.2021.113767] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 04/30/2021] [Accepted: 05/22/2021] [Indexed: 01/12/2023]
Abstract
Ischemic stroke is a leading cause of disability world-wide. Mounting evidence supports neuromuscular pathology following stroke, yet mechanisms of dysfunction and therapeutic action remain undefined. The objectives of our study were to investigate neuromuscular pathophysiology following ischemic stroke and to evaluate the therapeutic effect of Robot-Assisted Mechanical massage Therapy (RAMT) on neuromuscular junction (NMJ) morphology. Using an ischemic stroke model in male rats, we demonstrated longitudinal losses of muscle contractility and electrophysiological estimates of motor unit number in paretic hindlimb muscles within 21 days of stroke. Histological characterization demonstrated striking pre- and postsynaptic alterations at the NMJ. Stroke prompted enlargement of motor axon terminals, acetylcholine receptor (AChR) area, and motor endplate size. Paretic muscle AChRs were also more homogenously distributed across motor endplates, exhibiting fewer clusters and less fragmentation. Most interestingly, NMJs in paretic muscle exhibited increased frequency of polyaxonal innervation. This finding of increased polyaxonal innervation in stroke-affected skeletal muscle suggests that reduction of motor unit number following stroke may be a spurious artifact due to overlapping of motor units rather than losses. Furthermore, we tested the effects of RAMT - which we recently showed to improve motor function and protect against subacute myokine disturbance - and found significant attenuation of stroke-induced NMJ alterations. RAMT not only normalized the post-stroke presentation of polyaxonal innervation but also mitigated postsynaptic expansion. These findings confirm complex neuromuscular pathophysiology after stroke, provide mechanistic direction for ongoing research, and inform development of future therapeutic strategies. SIGNIFICANCE: Ischemic stroke is a leading contributor to chronic disability, and there is growing evidence that neuromuscular pathology may contribute to the impact of stroke on physical function. Following ischemic stroke in a rat model, there are progressive declines of motor unit number estimates and muscle contractility. These changes are paralleled by striking pre- and postsynaptic maladaptive changes at the neuromuscular junction, including polyaxonal innervation. When administered to paretic hindlimb muscle, Robot-Assisted Mechanical massage Therapy - previously shown to improve motor function and protect against subacute myokine disturbance - prevents stroke-induced neuromuscular junction alterations. These novel observations provide insight into the neuromuscular response to cerebral ischemia, identify peripheral mechanisms of functional disability, and present a therapeutic rehabilitation strategy with clinical relevance.
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Affiliation(s)
- Maria H H Balch
- Department of Biomedical Education and Anatomy, The Ohio State University College of Medicine, Columbus, OH, USA; Department of Neurosurgery, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Hallie Harris
- Department of Neurosurgery, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Deepti Chugh
- Department of Neurology, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Surya Gnyawali
- Department of Neurosurgery, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Cameron Rink
- Department of Neurosurgery, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Shahid M Nimjee
- Department of Neurosurgery, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Department of Neuroscience, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - W David Arnold
- Department of Neurology, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Department of Physical Medicine and Rehabilitation, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Department of Neuroscience, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH, USA.
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Manthou ME, Gencheva D, Sinis N, Rink S, Papamitsou T, Abdulla D, Bendella H, Sarikcioglu L, Angelov DN. Facial Nerve Repair by Muscle-Vein Conduit in Rats: Functional Recovery and Muscle Reinnervation. Tissue Eng Part A 2020; 27:351-361. [PMID: 32731808 DOI: 10.1089/ten.tea.2020.0045] [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] [Indexed: 12/12/2022] Open
Abstract
The facial nerve is the most frequently damaged nerve in head and neck traumata. Repair of interrupted nerves is generally reinforced by fine microsurgical techniques; nevertheless, regaining all functions is the exception rather than the rule. The so-called "postparalytic syndrome," which includes synkinesia and altered blink reflexes, follows nerve injury. The purpose of this study was to examine if nerve-gap repair using an autologous vein filled with skeletal muscle would improve axonal regeneration, reduce neuromuscular junction polyinnervation, and improve the recovery of whisking in rats with transected and sutured right buccal branches of the facial nerve. Vibrissal motor performance was studied with the use of a video motion analysis. Immunofluorescence was used to visualize and analyze target muscle reinnervation. The results taken together indicate a positive effect of muscle-vein-combined conduit (MVCC) on the improvement of the whisking function after reparation of the facial nerve in rats. The findings support the recent suggestion that a venal graft with implantation of a trophic source, such as autologous denervated skeletal muscle, may promote the monoinnervation degree and ameliorate coordinated function of the corresponding muscles.
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Affiliation(s)
- Maria Eleni Manthou
- Department of Histology and Embryology, Medical Faculty, School of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece.,Department of Anatomy I, University of Cologne, Cologne, Germany
| | - Dilyana Gencheva
- Department of Anatomy I, University of Cologne, Cologne, Germany
| | - Nektarios Sinis
- Privatklinik für Plastische- und Ästhetische Chirurgie, Berlin Wilmersdorf, Germany
| | - Svenja Rink
- Department of Prosthetic Dentistry, School of Dental and Oral Medicine, University of Cologne, Cologne, Germany
| | - Theodora Papamitsou
- Department of Histology and Embryology, Medical Faculty, School of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Diana Abdulla
- Department I of Internal Medicine, Center for Integrated Oncology Aachen Bonn Cologne Duesseldorf, Faculty of Medicine and University Hospital of Cologne, University of Cologne, Cologne, Germany
| | - Habib Bendella
- Department of Neurosurgery, University of Witten/Herdecke, Cologne Merheim Medical Center (CMMC), Cologne, Germany
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Bendella H, Rink S, Manthou M, Papamitsou T, Nakamura M, Angelov DN, Sarikcioglu L. Effect of surgically guided axonal regrowth into a 3-way-conduit (isogeneic trifurcated aorta) on functional recovery after facial-nerve reconstruction: Experimental study in rats. Restor Neurol Neurosci 2019; 37:181-196. [PMID: 31006701 DOI: 10.3233/rnn-190899] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND The "post-paralytic syndrome" after facial nerve reconstruction has been attributed to (i) malfunctioning axonal guidance at the fascicular (branches) level, (ii) collateral branching of the transected axons at the lesion site, and (iii) intensive intramuscular terminal sprouting of regenerating axons which causes poly-innervation of the neuromuscular junctions (NMJ). OBJECTIVE The first two reasons were approached by an innovative technique which should provide the re-growing axons optimal conditions to elongate and selectively re-innervate their original muscle groups. METHODS The transected facial nerve trunk was inserted into a 3-way-conduit (from isogeneic rat abdominal aorta) which should "guide" the re-growing facial axons to the three main branches of the facial nerve (zygomatic, buccal and marginal mandibular). The effect of this method was tested also on hypoglossal axons after hypoglossal-facial anastomosis (HFA). Coaptational (classic) FFA (facial-facial anastomosis) and HFA served as controls. RESULTS When compared to their coaptation (classic) alternatives, both types of 3-way-conduit operations (FFA and HFA) promoted a trend for reduction in the collateral axonal branching (the proportion of double- or triple-labelled perikarya after retrograde tracing was slightly reduced). In contrast, poly-innervation of NMJ in the levator labii superioris muscle was increased and vibrissal (whisking) function was worsened. CONCLUSIONS The use of 3-way-conduit provides no advantages to classic coaptation. Should the latter be impossible (too large interstump defects requiring too long interpositional nerve grafts), this type of reconstruction may be applied. (230 words).
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Affiliation(s)
- Habib Bendella
- Department of Neurosurgery, University of Witten/Herdecke, Cologne Merheim Medical Center (CMMC), Cologne, Germany
| | - Svenja Rink
- Department of Prosthetic Dentistry, School of Dental and Oral Medicine, University of Cologne, Cologne, Germany
| | - Marilena Manthou
- Department of Histology and Embryology, Aristotle University Thessaloniki, Greece
| | - Theodora Papamitsou
- Department of Histology and Embryology, Aristotle University Thessaloniki, Greece
| | - Makoto Nakamura
- Department of Neurosurgery, University of Witten/Herdecke, Cologne Merheim Medical Center (CMMC), Cologne, Germany
| | | | - Levent Sarikcioglu
- Department of Anatomy, Akdeniz University Faculty of Medicine, Antalya, Turkey
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