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Garcia-Ramirez DL, McGrath JR, Ha NT, Wheel JH, Atoche SJ, Yao L, Stachowski NJ, Giszter SF, Dougherty KJ. Covert actions of epidural stimulation on spinal locomotor circuits. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.18.599598. [PMID: 38948733 PMCID: PMC11213016 DOI: 10.1101/2024.06.18.599598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Spinal circuitry produces the rhythm and patterning of locomotion. However, both descending and sensory inputs are required to initiate and adapt locomotion to the environment. Spinal cord injury (SCI) disrupts descending controls of the spinal cord, producing paralysis. Epidural stimulation (ES) is a promising clinical therapy for motor control recovery and is capable of reactivating the lumbar spinal locomotor networks, yet little is known about the effects of ES on locomotor neurons. Previously, we found that both sensory afferent pathways and serotonin exert mixed excitatory and inhibitory actions on lumbar interneurons involved in the generation of the locomotor rhythm, identified by the transcription factor Shox2. However, after chronic complete SCI, sensory afferent inputs to Shox2 interneurons become almost exclusively excitatory and Shox2 interneurons are supersensitive to serotonin. Here, we investigated the effects of ES on these SCI-induced changes. Inhibitory input from sensory pathways to Shox2 interneurons was maintained and serotonin supersensitivity was not observed in SCI mice that received daily sub-motor threshold ES. Interestingly, the effects of ES were maintained for at least three weeks after the ES was discontinued. In contrast, the effects of ES were not observed in Shox2 interneurons from mice that received ES after the establishment of the SCI-induced changes. Our results demonstrate mechanistic actions of ES at the level of identified spinal locomotor circuit neurons and the effectiveness of early treatment with ES on preservation of spinal locomotor circuitry after SCI, suggesting possible therapeutic benefits prior to the onset of motor rehabilitation.
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Dominguez-Bajo A, Clotman F. Potential Roles of Specific Subclasses of Premotor Interneurons in Spinal Cord Function Recovery after Traumatic Spinal Cord Injury in Adults. Cells 2024; 13:652. [PMID: 38667267 PMCID: PMC11048910 DOI: 10.3390/cells13080652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Revised: 04/04/2024] [Accepted: 04/05/2024] [Indexed: 04/28/2024] Open
Abstract
The differential expression of transcription factors during embryonic development has been selected as the main feature to define the specific subclasses of spinal interneurons. However, recent studies based on single-cell RNA sequencing and transcriptomic experiments suggest that this approach might not be appropriate in the adult spinal cord, where interneurons show overlapping expression profiles, especially in the ventral region. This constitutes a major challenge for the identification and direct targeting of specific populations that could be involved in locomotor recovery after a traumatic spinal cord injury in adults. Current experimental therapies, including electrical stimulation, training, pharmacological treatments, or cell implantation, that have resulted in improvements in locomotor behavior rely on the modulation of the activity and connectivity of interneurons located in the surroundings of the lesion core for the formation of detour circuits. However, very few publications clarify the specific identity of these cells. In this work, we review the studies where premotor interneurons were able to create new intraspinal circuits after different kinds of traumatic spinal cord injury, highlighting the difficulties encountered by researchers, to classify these populations.
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Affiliation(s)
- Ana Dominguez-Bajo
- Université catholique de Louvain, Louvain Institute of Biomolecular Science and Technology (LIBST), Animal Molecular and Cellular Biology Group (AMCB), Place Croix du Sud 4–5, 1348 Louvain la Neuve, Belgium
| | - Frédéric Clotman
- Université catholique de Louvain, Louvain Institute of Biomolecular Science and Technology (LIBST), Animal Molecular and Cellular Biology Group (AMCB), Place Croix du Sud 4–5, 1348 Louvain la Neuve, Belgium
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3
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Yang J, Zhang Y, Cai Z, Zou J, Li S, Miao G, Lin H, Zhao X, Tan M. Inhibition of spastin impairs motor function recovery after spinal cord injury. Brain Res Bull 2023; 205:110806. [PMID: 37918696 DOI: 10.1016/j.brainresbull.2023.110806] [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: 05/17/2023] [Revised: 10/09/2023] [Accepted: 10/30/2023] [Indexed: 11/04/2023]
Abstract
Promoting axonal regeneration is an effective strategy for recovery from traumatic spinal cord injury (SCI). Spastin, a microtubule-severing protein, modulates axonal outgrowth and branch formation by regulating microtubule dynamics. However, the exact role of spastin during recovery from SCI remains unknown. Therefore, we utilized a hemisection injury model of the mouse spinal cord and explored the effect of spastin using a spastin inhibitor, spastazoline. Results showed that spastazoline significantly suppressed the microtubule-severing activity of spastin in COS-7 cells and inhibited the promoting effect of spastin on neurite outgrowth in primarily cultured hippocampal neurons. The protein expression level of spastin was significantly upregulated in the injured spinal cord. Injured mice showed impaired motor functions, which included increased toe-off angle and foot fault steps and decreased stride length and Basso mouse scale score. Notably, these motor function impairments were aggravated by the application of spastazoline. Inhibition of spastin exacerbated neurogenesis impairment, as demonstrated by neuronal nuclei antigen staining, the inflammatory response, as shown by Iba-1 and GFAP staining, and axonal regeneration impairment, as shown by 5-hydroxytryptamine staining. Furthermore, mass spectrometry analysis revealed that the inhibition of spastin resulted in numerous dysregulated differentially expressed proteins that were closely associated with vesicle organization and transport. Taken together, our data suggest that spastin is critical for recovery from SCI and may be a potential target for the treatment of SCI.
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Affiliation(s)
- Jie Yang
- Department of Orthopaedics, the First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - Yunlong Zhang
- Department of Orthopaedics, the First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - Zhenbin Cai
- Department of Orthopaedics, the First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - Jianyu Zou
- Department of Orthopaedics, the First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - Shaojin Li
- Department of Orthopaedics, the First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - Guiqiang Miao
- Department of Orthopedics, Foshan Fosun Chancheng Hospital, Foshan 528010, China
| | - Hongsheng Lin
- Department of Orthopaedics, the First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - Xiaodong Zhao
- Department of Orthopedics, Foshan Fosun Chancheng Hospital, Foshan 528010, China.
| | - Minghui Tan
- Department of Orthopaedics, the First Affiliated Hospital of Jinan University, Guangzhou 510630, China.
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4
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Dougherty KJ. Distinguishing subtypes of spinal locomotor neurons to inform circuit function and dysfunction. Curr Opin Neurobiol 2023; 82:102763. [PMID: 37611531 PMCID: PMC10578609 DOI: 10.1016/j.conb.2023.102763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 06/30/2023] [Accepted: 07/22/2023] [Indexed: 08/25/2023]
Abstract
Locomotion is a complex motor task executed by spinal neurons. Given the diversity of spinal cord neurons, linking neuronal cell type to function is a challenge. Molecular identification of broad spinal interneuronal classes provided a great advance. Recent studies have used other classifiers, including location, electrophysiological properties, and connectivity, in addition to gene profiling, to narrow the acuity with which groups of neurons can be related to specific functions. However, there are also functional populations without a clear identifier, as exemplified by rhythm generating neurons. Other considerations, including experience or plasticity, add a layer of complexity to the definition of functional subpopulations of spinal neurons, but spinal cord injury may provide insight.
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Affiliation(s)
- Kimberly J Dougherty
- Marion Murray Spinal Cord Research Center, Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA.
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5
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Punjani N, Deska-Gauthier D, Hachem LD, Abramian M, Fehlings MG. Neuroplasticity and regeneration after spinal cord injury. NORTH AMERICAN SPINE SOCIETY JOURNAL 2023; 15:100235. [PMID: 37416090 PMCID: PMC10320621 DOI: 10.1016/j.xnsj.2023.100235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 06/05/2023] [Accepted: 06/05/2023] [Indexed: 07/08/2023]
Abstract
Spinal cord injury (SCI) is a debilitating condition with significant personal, societal, and economic burden. The highest proportion of traumatic injuries occur at the cervical level, which results in severe sensorimotor and autonomic deficits. Following the initial physical damage associated with traumatic injuries, secondary pro-inflammatory, excitotoxic, and ischemic cascades are initiated further contributing to neuronal and glial cell death. Additionally, emerging evidence has begun to reveal that spinal interneurons undergo subtype specific neuroplastic circuit rearrangements in the weeks to months following SCI, contributing to or hindering functional recovery. The current therapeutic guidelines and standards of care for SCI patients include early surgery, hemodynamic regulation, and rehabilitation. Additionally, preclinical work and ongoing clinical trials have begun exploring neuroregenerative strategies utilizing endogenous neural stem/progenitor cells, stem cell transplantation, combinatorial approaches, and direct cell reprogramming. This review will focus on emerging cellular and noncellular regenerative therapies with an overview of the current available strategies, the role of interneurons in plasticity, and the exciting research avenues enhancing tissue repair following SCI.
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Affiliation(s)
- Nayaab Punjani
- Division of Genetics and Development, Krembil Research Institute, University Health Network, Toronto, ON, Canada
- Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Dylan Deska-Gauthier
- Division of Genetics and Development, Krembil Research Institute, University Health Network, Toronto, ON, Canada
- Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Laureen D. Hachem
- Division of Genetics and Development, Krembil Research Institute, University Health Network, Toronto, ON, Canada
- Institute of Medical Science, University of Toronto, Toronto, ON, Canada
- Department of Surgery, Division of Neurosurgery and Spine Program, University of Toronto, Toronto, ON, Canada
| | - Madlene Abramian
- Division of Genetics and Development, Krembil Research Institute, University Health Network, Toronto, ON, Canada
- Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Michael G. Fehlings
- Division of Genetics and Development, Krembil Research Institute, University Health Network, Toronto, ON, Canada
- Institute of Medical Science, University of Toronto, Toronto, ON, Canada
- Department of Surgery, Division of Neurosurgery and Spine Program, University of Toronto, Toronto, ON, Canada
- Division of Neurosurgery, Krembil Neuroscience Centre, Toronto Western Hospital, University Health Network, Toronto, ON, Canada
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6
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Aceves M, Tucker A, Chen J, Vo K, Moses J, Amar Kumar P, Thomas H, Miranda D, Dampf G, Dietz V, Chang M, Lukose A, Jang J, Nadella S, Gillespie T, Trevino C, Buxton A, Pritchard AL, Green P, McCreedy DA, Dulin JN. Developmental stage of transplanted neural progenitor cells influences anatomical and functional outcomes after spinal cord injury in mice. Commun Biol 2023; 6:544. [PMID: 37208439 PMCID: PMC10199026 DOI: 10.1038/s42003-023-04893-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 05/02/2023] [Indexed: 05/21/2023] Open
Abstract
Neural progenitor cell (NPC) transplantation is a promising therapeutic strategy for replacing lost neurons following spinal cord injury (SCI). However, how graft cellular composition influences regeneration and synaptogenesis of host axon populations, or recovery of motor and sensory functions after SCI, is poorly understood. We transplanted developmentally-restricted spinal cord NPCs, isolated from E11.5-E13.5 mouse embryos, into sites of adult mouse SCI and analyzed graft axon outgrowth, cellular composition, host axon regeneration, and behavior. Earlier-stage grafts exhibited greater axon outgrowth, enrichment for ventral spinal cord interneurons and Group-Z spinal interneurons, and enhanced host 5-HT+ axon regeneration. Later-stage grafts were enriched for late-born dorsal horn interneuronal subtypes and Group-N spinal interneurons, supported more extensive host CGRP+ axon ingrowth, and exacerbated thermal hypersensitivity. Locomotor function was not affected by any type of NPC graft. These findings showcase the role of spinal cord graft cellular composition in determining anatomical and functional outcomes following SCI.
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Affiliation(s)
- Miriam Aceves
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA
- Texas A&M Institute for Neuroscience, Texas A&M University, College Station, TX, 77843, USA
| | - Ashley Tucker
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA
- Texas A&M Institute for Neuroscience, Texas A&M University, College Station, TX, 77843, USA
| | - Joseph Chen
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA
| | - Katie Vo
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA
| | - Joshua Moses
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA
| | | | - Hannah Thomas
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA
| | - Diego Miranda
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA
| | - Gabrielle Dampf
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA
| | - Valerie Dietz
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA
| | - Matthew Chang
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA
| | - Aleena Lukose
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA
| | - Julius Jang
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA
| | - Sneha Nadella
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA
| | - Tucker Gillespie
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA
| | - Christian Trevino
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA
| | - Andrew Buxton
- Department of Biomedical Engineering, Texas A&M University, College Station, TX, 77843, USA
| | - Anna L Pritchard
- Department of Biomedical Engineering, Texas A&M University, College Station, TX, 77843, USA
| | | | - Dylan A McCreedy
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA
- Texas A&M Institute for Neuroscience, Texas A&M University, College Station, TX, 77843, USA
- Department of Biomedical Engineering, Texas A&M University, College Station, TX, 77843, USA
| | - Jennifer N Dulin
- Department of Biology, Texas A&M University, College Station, TX, 77843, USA.
- Texas A&M Institute for Neuroscience, Texas A&M University, College Station, TX, 77843, USA.
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7
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Cheng J, Guan NN. A fresh look at propriospinal interneurons plasticity and intraspinal circuits remodeling after spinal cord injury. IBRO Neurosci Rep 2023. [DOI: 10.1016/j.ibneur.2023.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023] Open
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8
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Huang CX, Wang Z, Cheng J, Zhu Z, Guan NN, Song J. De novo establishment of circuit modules restores locomotion after spinal cord injury in adult zebrafish. Cell Rep 2022; 41:111535. [DOI: 10.1016/j.celrep.2022.111535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 08/12/2022] [Accepted: 09/29/2022] [Indexed: 11/03/2022] Open
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9
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Matson KJE, Russ DE, Kathe C, Hua I, Maric D, Ding Y, Krynitsky J, Pursley R, Sathyamurthy A, Squair JW, Levi BP, Courtine G, Levine AJ. Single cell atlas of spinal cord injury in mice reveals a pro-regenerative signature in spinocerebellar neurons. Nat Commun 2022; 13:5628. [PMID: 36163250 PMCID: PMC9513082 DOI: 10.1038/s41467-022-33184-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Accepted: 08/31/2022] [Indexed: 12/12/2022] Open
Abstract
After spinal cord injury, tissue distal to the lesion contains undamaged cells that could support or augment recovery. Targeting these cells requires a clearer understanding of their injury responses and capacity for repair. Here, we use single nucleus RNA sequencing to profile how each cell type in the lumbar spinal cord changes after a thoracic injury in mice. We present an atlas of these dynamic responses across dozens of cell types in the acute, subacute, and chronically injured spinal cord. Using this resource, we find rare spinal neurons that express a signature of regeneration in response to injury, including a major population that represent spinocerebellar projection neurons. We characterize these cells anatomically and observed axonal sparing, outgrowth, and remodeling in the spinal cord and cerebellum. Together, this work provides a key resource for studying cellular responses to injury and uncovers the spontaneous plasticity of spinocerebellar neurons, uncovering a potential candidate for targeted therapy. Matson et al. performed single nucleus sequencing of the “spared” spinal cord tissue distal to an injury in mice. They found that spinocerebellar neurons expressed a pro-regenerative gene signature and showed axon outgrowth after injury.
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Affiliation(s)
- Kaya J E Matson
- Spinal Circuits and Plasticity Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA.,Johns Hopkins University Department of Biology, Baltimore, MD, USA
| | - Daniel E Russ
- Division of Cancer Epidemiology and Genetics, Data Science Research Group, National Cancer Institute, NIH, Rockville, MD, USA
| | - Claudia Kathe
- Center for Neuroprosthetics and Brain Mind Institute, Faculty of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.,NeuroRestore, Department of Clinical Neuroscience, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
| | - Isabelle Hua
- Spinal Circuits and Plasticity Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Dragan Maric
- National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA
| | - Yi Ding
- Allen Institute for Brain Science, Seattle, WA, USA
| | - Jonathan Krynitsky
- Signal Processing and Instrumentation Section, Center for Information Technology, National Institutes of Health, Bethesda, MD, USA
| | - Randall Pursley
- Signal Processing and Instrumentation Section, Center for Information Technology, National Institutes of Health, Bethesda, MD, USA
| | - Anupama Sathyamurthy
- Spinal Circuits and Plasticity Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA.,Centre for Neuroscience, Indian Institute of Science, Bangalore, India
| | - Jordan W Squair
- Center for Neuroprosthetics and Brain Mind Institute, Faculty of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.,NeuroRestore, Department of Clinical Neuroscience, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
| | - Boaz P Levi
- Allen Institute for Brain Science, Seattle, WA, USA
| | - Gregoire Courtine
- Center for Neuroprosthetics and Brain Mind Institute, Faculty of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.,NeuroRestore, Department of Clinical Neuroscience, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
| | - Ariel J Levine
- Spinal Circuits and Plasticity Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA.
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10
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Garcia-Ramirez DL, Singh S, McGrath JR, Ha NT, Dougherty KJ. Identification of adult spinal Shox2 neuronal subpopulations based on unbiased computational clustering of electrophysiological properties. Front Neural Circuits 2022; 16:957084. [PMID: 35991345 PMCID: PMC9385948 DOI: 10.3389/fncir.2022.957084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 07/08/2022] [Indexed: 11/13/2022] Open
Abstract
Spinal cord neurons integrate sensory and descending information to produce motor output. The expression of transcription factors has been used to dissect out the neuronal components of circuits underlying behaviors. However, most of the canonical populations of interneurons are heterogeneous and require additional criteria to determine functional subpopulations. Neurons expressing the transcription factor Shox2 can be subclassified based on the co-expression of the transcription factor Chx10 and each subpopulation is proposed to have a distinct connectivity and different role in locomotion. Adult Shox2 neurons have recently been shown to be diverse based on their firing properties. Here, in order to subclassify adult mouse Shox2 neurons, we performed multiple analyses of data collected from whole-cell patch clamp recordings of visually-identified Shox2 neurons from lumbar spinal slices. A smaller set of Chx10 neurons was included in the analyses for validation. We performed k-means and hierarchical unbiased clustering approaches, considering electrophysiological variables. Unlike the categorizations by firing type, the clusters displayed electrophysiological properties that could differentiate between clusters of Shox2 neurons. The presence of clusters consisting exclusively of Shox2 neurons in both clustering techniques suggests that it is possible to distinguish Shox2+Chx10- neurons from Shox2+Chx10+ neurons by electrophysiological properties alone. Computational clusters were further validated by immunohistochemistry with accuracy in a small subset of neurons. Thus, unbiased cluster analysis using electrophysiological properties is a tool that can enhance current interneuronal subclassifications and can complement groupings based on transcription factor and molecular expression.
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Affiliation(s)
| | | | | | | | - Kimberly J. Dougherty
- Department of Neurobiology and Anatomy, Marion Murray Spinal Cord Research Center, Drexel University College of Medicine, Philadelphia, PA, United States
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11
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Le Ray D, Guayasamin M. How Does the Central Nervous System for Posture and Locomotion Cope With Damage-Induced Neural Asymmetry? Front Syst Neurosci 2022; 16:828532. [PMID: 35308565 PMCID: PMC8927091 DOI: 10.3389/fnsys.2022.828532] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 02/07/2022] [Indexed: 12/28/2022] Open
Abstract
In most vertebrates, posture and locomotion are achieved by a biomechanical apparatus whose effectors are symmetrically positioned around the main body axis. Logically, motor commands to these effectors are intrinsically adapted to such anatomical symmetry, and the underlying sensory-motor neural networks are correspondingly arranged during central nervous system (CNS) development. However, many developmental and/or life accidents may alter such neural organization and acutely generate asymmetries in motor operation that are often at least partially compensated for over time. First, we briefly present the basic sensory-motor organization of posturo-locomotor networks in vertebrates. Next, we review some aspects of neural plasticity that is implemented in response to unilateral central injury or asymmetrical sensory deprivation in order to substantially restore symmetry in the control of posturo-locomotor functions. Data are finally discussed in the context of CNS structure-function relationship.
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12
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Walker JR, Detloff MR. Plasticity in Cervical Motor Circuits following Spinal Cord Injury and Rehabilitation. BIOLOGY 2021; 10:biology10100976. [PMID: 34681075 PMCID: PMC8533179 DOI: 10.3390/biology10100976] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 09/17/2021] [Accepted: 09/22/2021] [Indexed: 11/16/2022]
Abstract
Simple Summary Spinal cord injury results in a decreased quality of life and impacts hundreds of thousands of people in the US alone. This review discusses the underlying cellular mechanisms of injury and the concurrent therapeutic hurdles that impede recovery. It then describes the phenomena of neural plasticity—the nervous system’s ability to change. The primary focus of the review is on the impact of cervical spinal cord injury on control of the upper limbs. The neural plasticity that occurs without intervention is discussed, which shows new connections growing around the injury site and the involvement of compensatory movements. Rehabilitation-driven neural plasticity is shown to have the ability to guide connections to create more normal functions. Various novel stimulation and recording technologies are outlined for their role in further improving rehabilitative outcomes and gains in independence. Finally, the importance of sensory input, an often-overlooked aspect of motor control, is shown in driving neural plasticity. Overall, this review seeks to delineate the historical and contemporary research into neural plasticity following injury and rehabilitation to guide future studies. Abstract Neuroplasticity is a robust mechanism by which the central nervous system attempts to adapt to a structural or chemical disruption of functional connections between neurons. Mechanical damage from spinal cord injury potentiates via neuroinflammation and can cause aberrant changes in neural circuitry known as maladaptive plasticity. Together, these alterations greatly diminish function and quality of life. This review discusses contemporary efforts to harness neuroplasticity through rehabilitation and neuromodulation to restore function with a focus on motor recovery following cervical spinal cord injury. Background information on the general mechanisms of plasticity and long-term potentiation of the nervous system, most well studied in the learning and memory fields, will be reviewed. Spontaneous plasticity of the nervous system, both maladaptive and during natural recovery following spinal cord injury is outlined to provide a baseline from which rehabilitation builds. Previous research has focused on the impact of descending motor commands in driving spinal plasticity. However, this review focuses on the influence of physical therapy and primary afferent input and interneuron modulation in driving plasticity within the spinal cord. Finally, future directions into previously untargeted primary afferent populations are presented.
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