1
|
Jeon SM, Pradeep A, Chang D, McDonough L, Chen Y, Latremoliere A, Crawford LK, Caterina MJ. Skin Reinnervation by Collateral Sprouting Following Spared Nerve Injury in Mice. J Neurosci 2024; 44:e1494232024. [PMID: 38471780 PMCID: PMC11007315 DOI: 10.1523/jneurosci.1494-23.2024] [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: 08/07/2023] [Revised: 01/15/2024] [Accepted: 02/03/2024] [Indexed: 03/14/2024] Open
Abstract
Following peripheral nerve injury, denervated tissues can be reinnervated via regeneration of injured neurons or collateral sprouting of neighboring uninjured afferents into denervated territory. While there has been substantial focus on mechanisms underlying regeneration, collateral sprouting has received less attention. Here, we used immunohistochemistry and genetic neuronal labeling to define the subtype specificity of sprouting-mediated reinnervation of plantar hindpaw skin in the mouse spared nerve injury (SNI) model, in which productive regeneration cannot occur. Following initial loss of cutaneous afferents in the tibial nerve territory, we observed progressive centripetal reinnervation by multiple subtypes of neighboring uninjured fibers into denervated glabrous and hairy plantar skin of male mice. In addition to dermal reinnervation, CGRP-expressing peptidergic fibers slowly but continuously repopulated denervated epidermis, Interestingly, GFRα2-expressing nonpeptidergic fibers exhibited a transient burst of epidermal reinnervation, followed by a trend towards regression. Presumptive sympathetic nerve fibers also sprouted into denervated territory, as did a population of myelinated TrkC lineage fibers, though the latter did so inefficiently. Conversely, rapidly adapting Aβ fiber and C fiber low threshold mechanoreceptor (LTMR) subtypes failed to exhibit convincing sprouting up to 8 weeks after nerve injury in males or females. Optogenetics and behavioral assays in male mice further demonstrated the functionality of collaterally sprouted fibers in hairy plantar skin with restoration of punctate mechanosensation without hypersensitivity. Our findings advance understanding of differential collateral sprouting among sensory neuron subpopulations and may guide strategies to promote the progression of sensory recovery or limit maladaptive sensory phenomena after peripheral nerve injury.
Collapse
Affiliation(s)
- Sang-Min Jeon
- Department of Neurosurgery, Neurosurgery Pain Research Institute, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
| | - Aishwarya Pradeep
- Department of Neurosurgery, Neurosurgery Pain Research Institute, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
| | - Dennis Chang
- Department of Neurosurgery, Neurosurgery Pain Research Institute, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
| | - Leah McDonough
- Department of Neurosurgery, Neurosurgery Pain Research Institute, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
| | - Yijia Chen
- Department of Neurosurgery, Neurosurgery Pain Research Institute, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
| | - Alban Latremoliere
- Department of Neurosurgery, Neurosurgery Pain Research Institute, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
- Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
| | - LaTasha K Crawford
- Department of Pathological Sciences, University of Wisconsin-Madison School of Veterinary Medicine, Madison, Wisconsin 53706
| | - Michael J Caterina
- Department of Neurosurgery, Neurosurgery Pain Research Institute, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
- Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
- Department of Biological Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
| |
Collapse
|
2
|
Jeon SM, Pradeep A, Chang D, McDonough L, Chen Y, Latremoliere A, Crawford LK, Caterina MJ. SKIN REINNERVATION BY COLLATERAL SPROUTING FOLLOWING SPARED NERVE INJURY IN MICE. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.12.557420. [PMID: 37745384 PMCID: PMC10515828 DOI: 10.1101/2023.09.12.557420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
Following peripheral nerve injury, denervated tissues can be reinnervated via regeneration of injured neurons or via collateral sprouting of neighboring uninjured afferents into the denervated territory. While there has been substantial focus on mechanisms underlying regeneration, collateral sprouting has received relatively less attention. In this study, we used immunohistochemistry and genetic neuronal labeling to define the subtype specificity of sprouting-mediated reinnervation of plantar hind paw skin in the mouse spared nerve injury (SNI) model, in which productive regeneration cannot occur. Following an initial loss of cutaneous afferents in the tibial nerve territory, we observed progressive centripetal reinnervation by multiple subtypes of neighboring uninjured fibers into denervated glabrous and hairy plantar skin. In addition to dermal reinnervation, CGRP-expressing peptidergic fibers slowly but continuously repopulated the denervated epidermis, Interestingly, GFRα2-expressing nonpeptidergic fibers exhibited a transient burst of epidermal reinnervation, followed by trend towards regression. Presumptive sympathetic nerve fibers also sprouted into the denervated territory, as did a population of myelinated TrkC lineage fibers, though the latter did so less efficiently. Conversely, rapidly adapting Aβ fiber and C fiber low threshold mechanoreceptor (LTMR) subtypes failed to exhibit convincing collateral sprouting up to 8 weeks after nerve injury. Optogenetics and behavioral assays further demonstrated the functionality of collaterally sprouted fibers in hairy plantar skin with restoration of punctate mechanosensation without hypersensitivity. Our findings advance understanding of differential collateral sprouting among sensory neuron subpopulations and may guide strategies to promote the progression of sensory recovery or limit maladaptive sensory phenomena after peripheral nerve injury. Significance Statement Following nerve injury, whereas one mechanism for tissue reinnervation is regeneration of injured neurons, another, less well studied mechanism is collateral sprouting of nearby uninjured neurons. In this study, we examined collateral sprouting in denervated mouse skin and showed that it involves some, but not all neuronal subtypes. Despite such heterogeneity, a significant degree of restoration of punctate mechanical sensitivity is achieved. These findings highlight the diversity of collateral sprouting among peripheral neuron subtypes and reveal important differences between pre- and post-denervation skin that might be appealing targets for therapeutic correction to enhance functional recovery from denervation and prevent unwanted sensory phenomena such as pain or numbness.
Collapse
|
3
|
Schwaiger C, Haider T, Endmayr V, Zrzavy T, Gruber VE, Ricken G, Simonovska A, Hametner S, Schwab JM, Höftberger R. Dynamic induction of the myelin-associated growth inhibitor Nogo-A in perilesional plasticity regions after human spinal cord injury. Brain Pathol 2023; 33:e13098. [PMID: 35698271 PMCID: PMC9836369 DOI: 10.1111/bpa.13098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Accepted: 05/29/2022] [Indexed: 01/21/2023] Open
Abstract
The myelin-associated inhibitor Nogo-A (Reticulon 4, RTN4) restricts axonal outgrowth, plasticity, and neural circuitry formation in experimental models of spinal cord injury (SCI) and is targeted in clinical interventions starting treatment within 4 weeks post-SCI. Specifically, Nogo-A expressed by oligodendroglia restricts compensatory neurite sprouting. To interrogate the hypothesis of an inducible, lesion reactive Nogo-A expression over time, we analyzed the spatiotemporal Nogo-A expression at the spinal lesion core (region of tissue necrosis and axonal damage/pruning) and perilesional rim (region of plasticity formation). Spinal cord specimens of SCI subjects (n = 22) were compared to neuropathologically unaltered controls (n = 9). Nogo-A expression was investigated ranging from acute (0-3 days), early subacute (4-21 days), late subacute (22-90 days) to early chronic-chronic (91 days to 1.5 years after SCI) stages after SCI. Nogo-A expression in controls is confined to motoneurons in the anterior horn and to oligodendrocytes in gray and white matter. After SCI, the number of Nogo-A+ and TPPP/p25+ oligodendrocytes (i) inclined at the organizing perilesional rim specifically, (ii) increased further over time, and (iii) peaked at chronic stages after SCI. By contrast, at the lesion core, the number of Nogo-A+ and TPPP/p25+ oligodendrocytes did not increase. Increasing numbers of Nogo-A+ oligodendrocytes coincided with oligodendrogenesis corroborated by Nogo-A coexpression of Ki67+ , TPPP/p25+ proliferating oligodendrocytes. Nogo-A oligodendrocyte expression emerges at perilesional (plasticity) regions over time and suggests an extended therapeutical window for anti-Nogo-A pathway targeting interventions beyond 4 weeks in patients after SCI.
Collapse
Affiliation(s)
- Carmen Schwaiger
- Division of Neuropathology and Neurochemistry, Department of NeurologyMedical University of ViennaViennaAustria
| | - Thomas Haider
- Department of Orthopedics and Trauma SurgeryMedical University of ViennaViennaAustria
| | - Verena Endmayr
- Division of Neuropathology and Neurochemistry, Department of NeurologyMedical University of ViennaViennaAustria
| | - Tobias Zrzavy
- Department of NeurologyMedical University of ViennaViennaAustria
| | - Victoria E. Gruber
- Department of Pediatrics and Adolescent MedicineMedical University of Vienna (Affiliated Partner of the ERN EpiCARE)ViennaAustria
| | - Gerda Ricken
- Division of Neuropathology and Neurochemistry, Department of NeurologyMedical University of ViennaViennaAustria
| | - Anika Simonovska
- Center for Medical Physics and Biomedical EngineeringMedical University of ViennaViennaAustria
| | - Simon Hametner
- Division of Neuropathology and Neurochemistry, Department of NeurologyMedical University of ViennaViennaAustria
| | - Jan M. Schwab
- The Belford Center for Spinal Cord Injury and Departments of Neurology, Physical Medicine and Rehabilitation and NeurosciencesThe Ohio State UniversityColumbusOhioUSA
| | - Romana Höftberger
- Division of Neuropathology and Neurochemistry, Department of NeurologyMedical University of ViennaViennaAustria
| |
Collapse
|
4
|
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.
Collapse
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.
| |
Collapse
|
5
|
Fakhri S, Abbaszadeh F, Moradi SZ, Cao H, Khan H, Xiao J. Effects of Polyphenols on Oxidative Stress, Inflammation, and Interconnected Pathways during Spinal Cord Injury. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2022; 2022:8100195. [PMID: 35035667 PMCID: PMC8759836 DOI: 10.1155/2022/8100195] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 12/11/2021] [Indexed: 02/05/2023]
Abstract
Despite the progression in targeting the complex pathophysiological mechanisms of neurodegenerative diseases (NDDs) and spinal cord injury (SCI), there is a lack of effective treatments. Moreover, conventional therapies suffer from associated side effects and low efficacy, raising the need for finding potential alternative therapies. In this regard, a comprehensive review was done regarding revealing the main neurological dysregulated pathways and providing alternative therapeutic agents following SCI. From the mechanistic point, oxidative stress and inflammatory pathways are major upstream orchestras of cross-linked dysregulated pathways (e.g., apoptosis, autophagy, and extrinsic mechanisms) following SCI. It urges the need for developing multitarget therapies against SCI complications. Polyphenols, as plant-derived secondary metabolites, have the potential of being introduced as alternative therapeutic agents to pave the way for treating SCI. Such secondary metabolites presented modulatory effects on neuronal oxidative stress, neuroinflammatory, and extrinsic axonal dysregulated pathways in the onset and progression of SCI. In the present review, the potential role of phenolic compounds as critical phytochemicals has also been revealed in regulating upstream dysregulated oxidative stress/inflammatory signaling mediators and extrinsic mechanisms of axonal regeneration after SCI in preclinical and clinical studies. Additionally, the coadministration of polyphenols and stem cells has shown a promising strategy for improving post-SCI complications.
Collapse
Affiliation(s)
- Sajad Fakhri
- Pharmaceutical Sciences Research Center, Health Institute, Kermanshah University of Medical Sciences, Kermanshah 6734667149, Iran
| | - Fatemeh Abbaszadeh
- Department of Neuroscience, Faculty of Advanced Technologies in Medical Sciences, Iran University of Medical Sciences, Tehran, Iran
- Neurobiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Seyed Zachariah Moradi
- Pharmaceutical Sciences Research Center, Health Institute, Kermanshah University of Medical Sciences, Kermanshah 6734667149, Iran
- Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah 6734667149, Iran
| | - Hui Cao
- Nutrition and Bromatology Group, Department of Analytical Chemistry and Food Science, Faculty of Food Science and Technology, University of Vigo-Ourense Campus, E-32004 Ourense, Spain
| | - Haroon Khan
- Department of Pharmacy, Abdul Wali Khan University Mardan, 23200, Pakistan
| | - Jianbo Xiao
- Nutrition and Bromatology Group, Department of Analytical Chemistry and Food Science, Faculty of Food Science and Technology, University of Vigo-Ourense Campus, E-32004 Ourense, Spain
- Institute of Food Safety and Nutrition, Jinan University, Guangzhou 510632, China
| |
Collapse
|
6
|
Varadarajan SG, Hunyara JL, Hamilton NR, Kolodkin AL, Huberman AD. Central nervous system regeneration. Cell 2022; 185:77-94. [PMID: 34995518 PMCID: PMC10896592 DOI: 10.1016/j.cell.2021.10.029] [Citation(s) in RCA: 82] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 10/26/2021] [Accepted: 10/27/2021] [Indexed: 02/06/2023]
Abstract
Neurons of the mammalian central nervous system fail to regenerate. Substantial progress has been made toward identifying the cellular and molecular mechanisms that underlie regenerative failure and how altering those pathways can promote cell survival and/or axon regeneration. Here, we summarize those findings while comparing the regenerative process in the central versus the peripheral nervous system. We also highlight studies that advance our understanding of the mechanisms underlying neural degeneration in response to injury, as many of these mechanisms represent primary targets for restoring functional neural circuits.
Collapse
Affiliation(s)
| | - John L Hunyara
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Natalie R Hamilton
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Alex L Kolodkin
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
| | - Andrew D Huberman
- Department of Neurobiology, Stanford University, Stanford, CA 94305, USA; Department of Ophthalmology, Stanford University, Stanford, CA 94305, USA.
| |
Collapse
|
7
|
Lemaitre D, Court FA. New insights on the molecular mechanisms of collateral sprouting after peripheral nerve injury. Neural Regen Res 2021; 16:1760-1761. [PMID: 33510065 PMCID: PMC8328757 DOI: 10.4103/1673-5374.306069] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Dominique Lemaitre
- Universidad del Desarrollo, Facultad de Medicina, Centro de Fisiología Celular e Integrativa, Santiago, Chile
| | - Felipe A Court
- Center for Integrative Biology, Faculty of Sciences, Universidad Mayor; Geroscience Center for Brain Health and Metabolism (GERO), Santiago, Chile; The Buck Institute for Research on Aging, Novato, CA, USA
| |
Collapse
|
8
|
Vaquié A, Sauvain A, Duman M, Nocera G, Egger B, Meyenhofer F, Falquet L, Bartesaghi L, Chrast R, Lamy CM, Bang S, Lee SR, Jeon NL, Ruff S, Jacob C. Injured Axons Instruct Schwann Cells to Build Constricting Actin Spheres to Accelerate Axonal Disintegration. Cell Rep 2020; 27:3152-3166.e7. [PMID: 31189102 DOI: 10.1016/j.celrep.2019.05.060] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Revised: 04/11/2019] [Accepted: 05/17/2019] [Indexed: 01/26/2023] Open
Abstract
After a peripheral nerve lesion, distal ends of injured axons disintegrate into small fragments that are subsequently cleared by Schwann cells and later by macrophages. Axonal debris clearing is an early step of the repair process that facilitates regeneration. We show here that Schwann cells promote distal cut axon disintegration for timely clearing. By combining cell-based and in vivo models of nerve lesion with mouse genetics, we show that this mechanism is induced by distal cut axons, which signal to Schwann cells through PlGF mediating the activation and upregulation of VEGFR1 in Schwann cells. In turn, VEGFR1 activates Pak1, leading to the formation of constricting actomyosin spheres along unfragmented distal cut axons to mediate their disintegration. Interestingly, oligodendrocytes can acquire a similar behavior as Schwann cells by enforced expression of VEGFR1. These results thus identify controllable molecular cues of a neuron-glia crosstalk essential for timely clearing of damaged axons.
Collapse
Affiliation(s)
- Adrien Vaquié
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Alizée Sauvain
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Mert Duman
- Department of Biology, University of Fribourg, Fribourg, Switzerland; Department of Biology, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Gianluigi Nocera
- Department of Biology, University of Fribourg, Fribourg, Switzerland; Department of Biology, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Boris Egger
- Department of Biology, University of Fribourg, Fribourg, Switzerland; Bioimage Light Microscopy Facility, University of Fribourg, Fribourg, Switzerland
| | - Felix Meyenhofer
- Department of Biology, University of Fribourg, Fribourg, Switzerland; Department of Medicine, University of Fribourg, Fribourg, Switzerland; Bioimage Light Microscopy Facility, University of Fribourg, Fribourg, Switzerland
| | - Laurent Falquet
- Department of Biology, University of Fribourg, Fribourg, Switzerland; Department of Medicine, University of Fribourg, Fribourg, Switzerland; Bioinformatics Core Facility, University of Fribourg and Swiss Institute of Bioinformatics, Fribourg, Switzerland
| | - Luca Bartesaghi
- Departments of Neuroscience and Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Roman Chrast
- Departments of Neuroscience and Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | | | - Seokyoung Bang
- School of Mechanical and Aerospace Engineering, Seoul National University, Seoul, South Korea
| | - Seung-Ryeol Lee
- School of Mechanical and Aerospace Engineering, Seoul National University, Seoul, South Korea
| | - Noo Li Jeon
- School of Mechanical and Aerospace Engineering, Seoul National University, Seoul, South Korea
| | - Sophie Ruff
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Claire Jacob
- Department of Biology, University of Fribourg, Fribourg, Switzerland; Department of Biology, Johannes Gutenberg University Mainz, Mainz, Germany.
| |
Collapse
|
9
|
Lemaitre D, Hurtado ML, De Gregorio C, Oñate M, Martínez G, Catenaccio A, Wishart TM, Court FA. Collateral Sprouting of Peripheral Sensory Neurons Exhibits a Unique Transcriptomic Profile. Mol Neurobiol 2020; 57:4232-4249. [PMID: 32696431 DOI: 10.1007/s12035-020-01986-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 06/08/2020] [Indexed: 12/29/2022]
Abstract
Peripheral nerve injuries result in motor and sensory dysfunction which can be recovered by compensatory or regenerative processes. In situations where axonal regeneration of injured neurons is hampered, compensation by collateral sprouting from uninjured neurons contributes to target reinnervation and functional recovery. Interestingly, this process of collateral sprouting from uninjured neurons has been associated with the activation of growth-associated programs triggered by Wallerian degeneration. Nevertheless, the molecular alterations at the transcriptomic level associated with these compensatory growth mechanisms remain to be fully elucidated. We generated a surgical model of partial sciatic nerve injury in mice to mechanistically study degeneration-induced collateral sprouting from spared fibers in the peripheral nervous system. Using next-generation sequencing and Ingenuity Pathway Analysis, we described the sprouting-associated transcriptome of uninjured sensory neurons and compare it with the activated by regenerating neurons. In vitro approaches were used to functionally assess sprouting gene candidates in the mechanisms of axonal growth. Using a novel animal model, we provide the first description of the sprouting transcriptome observed in uninjured sensory neurons after nerve injury. This collateral sprouting-associated transcriptome differs from that seen in regenerating neurons, suggesting a molecular program distinct from axonal growth. We further demonstrate that genetic upregulation of novel sprouting-associated genes activates a specific growth program in vitro, leading to increased neuronal branching. These results contribute to our understanding of the molecular mechanisms associated with collateral sprouting in vivo. The data provided here will therefore be instrumental in developing therapeutic strategies aimed at promoting functional recovery after injury to the nervous system.
Collapse
Affiliation(s)
- Dominique Lemaitre
- Facultad de Medicina, Centro de Fisiología Celular e Integrativa, Universidad del Desarrollo, Santiago, Chile
| | | | - Cristian De Gregorio
- Centro de Medicina Regenerativa, Facultad de Medicina Clínica Alemana, Universidad del Desarrollo, Santiago, Chile
| | - Maritza Oñate
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Gabriela Martínez
- Biomedical Neuroscience Institute (BNI), Faculty of Medicine, University of Chile, Santiago, Chile.,Program of Cellular and Molecular Biology, Institute of Biomedical Sciences, Departamento de Neurología y Neurocirugía, Hospital Clínico, University of Chile, Santiago, Chile.,FONDAP Center for Geroscience (GERO) Brain Health and Metabolism, Santiago, Chile
| | - Alejandra Catenaccio
- Center for Integrative Biology, Faculty of Sciences, Universidad Mayor, Santiago, Chile
| | | | - Felipe A Court
- FONDAP Center for Geroscience (GERO) Brain Health and Metabolism, Santiago, Chile. .,Center for Integrative Biology, Faculty of Sciences, Universidad Mayor, Santiago, Chile. .,Buck Institute for Research on Aging, Novato, CA, 94945, USA.
| |
Collapse
|
10
|
Meehan CF, Ford TW, Kirkwood PA. Plasticity of thoracic interneurones rostral to a lateral spinal cord lesion. Exp Neurol 2020; 331:113361. [PMID: 32464119 DOI: 10.1016/j.expneurol.2020.113361] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 05/03/2020] [Accepted: 05/17/2020] [Indexed: 01/14/2023]
Abstract
The morphology and projections of ventral horn interneurones in the segment above an ipsilateral thoracic lateral spinal cord lesion were studied in the cat by intracellular injections of Neurobiotin at 6 to 18 weeks post-lesion and compared with previously published control data from uninjured spinal cords. The cell axons ascended, descended or both, mostly contralaterally and mostly spared by the lesion. Unusual morphological dendritic features were seen in the lesion group, mostly growth-related, including complex dendritic appendages, twisted or multiple-branched terminal dendrites, commissural dendrites, apparently swollen proximal dendrites and rostrocaudal asymmetries. Significant quantitative differences included more dendritic spines in the lesion group (3.4×) and smaller soma areas in the lesion group (with similar numbers of primary dendrites and rostrocaudal dendritic spans). Immunoreactivity to microtubule associated protein 2a/b was detected in the proximal, but not distal, dendrites of cells in the lesion group, corresponding to an overall decrease in immunoreactivity in the ventral horns on the lesion side compared to the other. For axon collaterals, significant increases for the lesion group were seen in the number of collaterals in the first 4 mm of axon and in the area of ventral/intermediate horn occupied by terminals, including increased innervation of some regions, among which were the intermediolateral columns. This dendritic and axonal plasticity makes the interneuones candidates for a role in detour circuits but also for a maladaptive role in autonomic hyperreflexia.
Collapse
Affiliation(s)
- Claire Francesca Meehan
- Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK.
| | - Timothy W Ford
- Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Peter A Kirkwood
- Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| |
Collapse
|
11
|
Improvement of motor function induced by skeletal muscle contraction in spinal cord-injured rats. Spine J 2019; 19:1094-1105. [PMID: 30583107 DOI: 10.1016/j.spinee.2018.12.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 12/19/2018] [Accepted: 12/19/2018] [Indexed: 02/03/2023]
Abstract
BACKGROUND The involvement of neurotrophic factors such as brain-derived neurotrophic factor (BDNF) in functional recovery after spinal cord injury (SCI) by treadmill training has been suggested. The precise mechanism is poorly understood. However, muscle-derived bioactive molecules (myokines) are known to be produced by muscle contraction. Although BDNF is a myokine and is considered to be a potential mediator of neuroplasticity following exercise, its contribution to motor function recovery after SCI has not yet been described in detail. PURPOSE To investigate the role of muscle contraction in motor function recovery after SCI, with a focus on BDNF. STUDY DESIGN Male Sprague-Dawley rats (aged 8-9 weeks) were used to establish the SCI model. Percutaneous electrical muscle stimulation (10 mA, 2 Hz, 10 minutes) was applied to both hindlimbs of the rats immediately after SCI. The stimulation was performed once per day for 4 weeks. The sham, SCI only (SCI), and SCI with electrical muscle stimulation (SCI+ES) groups were compared. METHODS Spinal cord injury was induced by dropping a 20 g rod with an apex diameter of 2 mm from a height of 25 mm onto the spine of an anesthetized rat at the T9 level. Motor function was assessed using the Basso-Beattie-Bresnahan Locomotor Scale, inclined plane test, and rotarod test. One week after injury, terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells were counted at the injury epicenter, and the level of BDNF was measured in both the spinal cord and the anterior tibial muscle. Four weeks after injury, the cavity volume of the epicenter and the level of phosphorylated growth-associated protein 43 in the spinal cord were measured. RESULTS Significantly improved Basso-Beattie-Bresnahan scores and inclined plane test results were observed in the SCI+ES group compared with those in the SCI group at 4 weeks post-SCI. We also observed a decrease in the cavity volume and an increase in phosphorylated growth-associated protein 43 levels in the SCI+ES group. Electrical muscle stimulation decreased the numbers of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells in the epicenter and increased the levels of BDNF in the spinal cord and lower limb muscles at 1 week post-SCI. CONCLUSIONS Electrical muscle stimulation improved motor function and increased BDNF levels in both the muscles and the spinal cords of rats subjected to SCI. Muscle contraction-induced BDNF expression might be involved in motor recovery during rehabilitation. CLINICAL RELEVANCE Our study provides experimental evidence for a possible therapeutic role of peripheral electrical muscle stimulation to enhance motor recovery after SCI.
Collapse
|
12
|
Tang BL. Why is NMNAT Protective against Neuronal Cell Death and Axon Degeneration, but Inhibitory of Axon Regeneration? Cells 2019; 8:cells8030267. [PMID: 30901919 PMCID: PMC6468476 DOI: 10.3390/cells8030267] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Revised: 03/15/2019] [Accepted: 03/18/2019] [Indexed: 02/06/2023] Open
Abstract
Nicotinamide mononucleotide adenylyltransferase (NMNAT), a key enzyme for NAD+ synthesis, is well known for its activity in neuronal survival and attenuation of Wallerian degeneration. Recent investigations in invertebrate models have, however, revealed that NMNAT activity negatively impacts upon axon regeneration. Overexpression of Nmnat in laser-severed Drosophila sensory neurons reduced axon regeneration, while axon regeneration was enhanced in injured mechanosensory axons in C. elegansnmat-2 null mutants. These diametrically opposite effects of NMNAT orthologues on neuroprotection and axon regeneration appear counterintuitive as there are many examples of neuroprotective factors that also promote neurite outgrowth, and enhanced neuronal survival would logically facilitate regeneration. We suggest here that while NMNAT activity and NAD+ production activate neuroprotective mechanisms such as SIRT1-mediated deacetylation, the same mechanisms may also activate a key axonal regeneration inhibitor, namely phosphatase and tensin homolog (PTEN). SIRT1 is known to deacetylate and activate PTEN which could, in turn, suppress PI3 kinase–mTORC1-mediated induction of localized axonal protein translation, an important process that determines successful regeneration. Strategic tuning of Nmnat activity and NAD+ production in axotomized neurons may thus be necessary to promote initial survival without inhibiting subsequent regeneration.
Collapse
Affiliation(s)
- Bor Luen Tang
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, Singapore.
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117597, Singapore.
| |
Collapse
|
13
|
Tran AP, Warren PM, Silver J. The Biology of Regeneration Failure and Success After Spinal Cord Injury. Physiol Rev 2018. [PMID: 29513146 DOI: 10.1152/physrev.00017.2017] [Citation(s) in RCA: 497] [Impact Index Per Article: 82.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Since no approved therapies to restore mobility and sensation following spinal cord injury (SCI) currently exist, a better understanding of the cellular and molecular mechanisms following SCI that compromise regeneration or neuroplasticity is needed to develop new strategies to promote axonal regrowth and restore function. Physical trauma to the spinal cord results in vascular disruption that, in turn, causes blood-spinal cord barrier rupture leading to hemorrhage and ischemia, followed by rampant local cell death. As subsequent edema and inflammation occur, neuronal and glial necrosis and apoptosis spread well beyond the initial site of impact, ultimately resolving into a cavity surrounded by glial/fibrotic scarring. The glial scar, which stabilizes the spread of secondary injury, also acts as a chronic, physical, and chemo-entrapping barrier that prevents axonal regeneration. Understanding the formative events in glial scarring helps guide strategies towards the development of potential therapies to enhance axon regeneration and functional recovery at both acute and chronic stages following SCI. This review will also discuss the perineuronal net and how chondroitin sulfate proteoglycans (CSPGs) deposited in both the glial scar and net impede axonal outgrowth at the level of the growth cone. We will end the review with a summary of current CSPG-targeting strategies that help to foster axonal regeneration, neuroplasticity/sprouting, and functional recovery following SCI.
Collapse
Affiliation(s)
- Amanda Phuong Tran
- Department of Neurosciences, Case Western Reserve University , Cleveland, Ohio ; and School of Biomedical Sciences, University of Leeds , Leeds , United Kingdom
| | - Philippa Mary Warren
- Department of Neurosciences, Case Western Reserve University , Cleveland, Ohio ; and School of Biomedical Sciences, University of Leeds , Leeds , United Kingdom
| | - Jerry Silver
- Department of Neurosciences, Case Western Reserve University , Cleveland, Ohio ; and School of Biomedical Sciences, University of Leeds , Leeds , United Kingdom
| |
Collapse
|
14
|
Feng L, Gan H, Zhao W, Liu Y. Effect of transplantation of olfactory ensheathing cell conditioned medium induced bone marrow stromal cells on rats with spinal cord injury. Mol Med Rep 2017; 16:1661-1668. [PMID: 28656221 PMCID: PMC5562047 DOI: 10.3892/mmr.2017.6811] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 02/16/2017] [Indexed: 12/21/2022] Open
Abstract
Spinal cord injury is a serious threat to human health and various techniques have been deployed to ameliorate or cure its effects. Stem cells transplantation is one of the promising methods. The primary aim of the present study was to investigate the effect of the transplantation of olfactory ensheathing cell (OEC) conditioned medium-induced bone marrow stromal cells (BMSCs) on spinal cord injury. Rat spinal cord compression injury animal models were generated, and the rats divided into the following three groups: Group A, (control) Dulbecco's modified Eagle's medium-treated group; group B, normal BMSC-treated group; group C, OEC conditioned medium-induced BMSC-treated group. The animals were sacrificed at 2, 4 and 8 weeks following transplantation for hematoxylin and eosin staining, and fluorescence staining of neurofilament protein, growth associated protein-43 and neuron-specific nuclear protein. The cavity area of the spinal cord injury was significantly reduced at 2 and 4 weeks following transplantation in group C, and a significant difference between the Basso, Beattie and Bresnahan score in group C and groups A and B was observed. Regenerated nerve fibers were observed in groups B and C; however, a greater number of regenerated nerve fibers were observed in group C. BMSCs induced by OEC conditioned medium survived in vivo, significantly reduced the cavity area of spinal cord injury, promoted nerve fiber regeneration following spinal cord injury and facilitated recovery of motor function. The present study demonstrated a novel method to repair spinal cord injury by using induced BMSCs, with satisfactory results.
Collapse
Affiliation(s)
- Linjie Feng
- Department of Orthopedics, North China University of Science and Technology Affiliated Hospital, Tangshan, Hebei 063000, P.R. China
| | - Hongquan Gan
- Department of Orthopedics, North China University of Science and Technology Affiliated Hospital, Tangshan, Hebei 063000, P.R. China
| | - Wenguo Zhao
- Department of Orthopedics, North China University of Science and Technology Affiliated Hospital, Tangshan, Hebei 063000, P.R. China
| | - Yingjie Liu
- Department of Orthopedics, North China University of Science and Technology Affiliated Hospital, Tangshan, Hebei 063000, P.R. China
| |
Collapse
|
15
|
Quan Q, Chang B, Meng HY, Liu RX, Wang Y, Lu SB, Peng J, Zhao Q. Use of electrospinning to construct biomaterials for peripheral nerve regeneration. Rev Neurosci 2016; 27:761-768. [PMID: 27428846 DOI: 10.1515/revneuro-2016-0032] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 05/26/2016] [Indexed: 12/16/2022]
Abstract
AbstractA number of limitations associated with the use of hollow nerve guidance conduits (NGCs) require further discussion. Most importantly, the functional recovery outcomes after the placement of hollow NGCs are poor even after the successful bridging of peripheral nerve injuries. However, nerve regeneration scaffolds built using electric spinning have several advantages that may improve functional recovery. Thus, the present study summarizes recent developments in this area, including the key cells that are combined with the scaffold and associated with nerve regeneration, the structure and configuration of the electrospinning design (which determines the performance of the electrospinning scaffold), the materials the electrospinning fibers are composed of, and the methods used to control the morphology of a single fiber. Additionally, this study also discusses the processes underlying peripheral nerve regeneration. The primary goals of the present review were to evaluate and consolidate the findings of studies that used scaffolding biomaterials built by electrospinning used for peripheral nerve regeneration support. It is amazing that the field of peripheral nerve regeneration continues to consistently produce such a wide variety of innovative techniques and novel types of equipment, because the introduction of every new process creates an opportunity for advances in materials for nerve repair.
Collapse
|
16
|
Schwann Cell Exosomes Mediate Neuron–Glia Communication and Enhance Axonal Regeneration. Cell Mol Neurobiol 2016; 36:429-36. [DOI: 10.1007/s10571-015-0314-3] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 11/24/2015] [Indexed: 12/30/2022]
|
17
|
Pawar K, Cummings BJ, Thomas A, Shea LD, Levine A, Pfaff S, Anderson AJ. Biomaterial bridges enable regeneration and re-entry of corticospinal tract axons into the caudal spinal cord after SCI: Association with recovery of forelimb function. Biomaterials 2015; 65:1-12. [PMID: 26134079 PMCID: PMC4523232 DOI: 10.1016/j.biomaterials.2015.05.032] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 05/18/2015] [Indexed: 12/16/2022]
Abstract
Severed axon tracts fail to exhibit robust or spontaneous regeneration after spinal cord injury (SCI). Regeneration failure reflects a combination of factors, including the growth state of neuronal cell bodies and the regeneration-inhibitory environment of the central nervous system. However, while spared circuitry can be retrained, target reinnervation depends on longitudinally directed regeneration of transected axons. This study describes a biodegradable implant using poly(lactide-co-glycolide) (PLG) bridges as a carrier scaffold to support regeneration after injury. In order to detect regeneration of descending neuronal tracts into the bridge, and beyond into intact caudal parenchyma, we developed a mouse cervical implantation model and employed Crym:GFP transgenic mice. Characterization of Crym:GFP mice revealed that descending tracts, including the corticospinal tract, were labeled by green fluorescent protein (GFP), while ascending sensory neurons and fibers were not. Robust co-localization between GFP and neurofilament-200 (NF-200) as well as GFP and GAP-43 was observed at both the rostral and caudal bridge/tissue interface. No evidence of similar regeneration was observed in mice that received gelfoam at the lesion site as controls. Minimal co-localization between GFP reporter labeling and macrophage markers was observed. Taken together, these data suggest that axons originating from descending fiber tracts regenerated, entered into the PLG bridge at the rostral margin, continued through the bridge site, and exited to re-enter host tissue at the caudal edge of the intact bridge. Finally, regeneration through implanted bridges was associated with a reduction in ipsilateral forelimb errors on a horizontal ladder task.
Collapse
Affiliation(s)
- Kiran Pawar
- Institute for Memory Impairments and Neurological Disorders (iMIND), University of California, Irvine, CA, USA
| | - Brian J Cummings
- Institute for Memory Impairments and Neurological Disorders (iMIND), University of California, Irvine, CA, USA; Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, USA; Department of Physical Medicine and Rehabilitation, University of California, Irvine, CA, USA; Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA
| | - Aline Thomas
- Department of Chemical and Biological Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, USA
| | - Lonnie D Shea
- Department of Chemical and Biological Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, USA
| | | | | | - Aileen J Anderson
- Institute for Memory Impairments and Neurological Disorders (iMIND), University of California, Irvine, CA, USA; Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, USA; Department of Physical Medicine and Rehabilitation, University of California, Irvine, CA, USA; Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA.
| |
Collapse
|
18
|
Jones TA, Adkins DL. Motor System Reorganization After Stroke: Stimulating and Training Toward Perfection. Physiology (Bethesda) 2015; 30:358-70. [PMID: 26328881 PMCID: PMC4556825 DOI: 10.1152/physiol.00014.2015] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Stroke instigates regenerative responses that reorganize connectivity patterns among surviving neurons. The new connectivity patterns can be suboptimal for behavioral function. This review summarizes current knowledge on post-stroke motor system reorganization and emerging strategies for shaping it with manipulations of behavior and cortical activity to improve functional outcome.
Collapse
Affiliation(s)
- Theresa A Jones
- Psychology Department, Neuroscience Institute, University of Texas at Austin, Austin, Texas; and
| | - DeAnna L Adkins
- Neurosciences Department, and Health Sciences & Research Department, Colleges of Medicine & Health Professions, Medical University of South Carolina, Charleston, South Carolina
| |
Collapse
|
19
|
Plasticity of intact rubral projections mediates spontaneous recovery of function after corticospinal tract injury. J Neurosci 2015; 35:1443-57. [PMID: 25632122 DOI: 10.1523/jneurosci.3713-14.2015] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Axons in the adult CNS fail to regenerate after injury, and therefore recovery from spinal cord injury (SCI) is limited. Although full recovery is rare, a modest degree of spontaneous recovery is observed consistently in a broad range of clinical and nonclinical situations. To define the mechanisms mediating spontaneous recovery of function after incomplete SCI, we created bilaterally complete medullary corticospinal tract lesions in adult mice, eliminating a crucial pathway for voluntary skilled movement. Anatomic and pharmacogenetic tools were used to identify the pathways driving spontaneous functional recovery in wild-type and plasticity-sensitized mice lacking Nogo receptor 1. We found that plasticity-sensitized mice recovered 50% of normal skilled locomotor function within 5 weeks of lesion. This significant, yet incomplete, spontaneous recovery was accompanied by extensive sprouting of intact rubrofugal and rubrospinal projections with the emergence of a de novo circuit between the red nucleus and the nucleus raphe magnus. Transient silencing of this rubro-raphe circuit in vivo via activation of the inhibitory DREADD (designer receptor exclusively activated by designer drugs) receptor hM4di abrogated spontaneous functional recovery. These data highlight the pivotal role of uninjured motor circuit plasticity in supporting functional recovery after trauma, and support a focus of experimental strategies on enhancing intact circuit rearrangement to promote functional recovery after SCI.
Collapse
|