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Holmes TC, Popp NM, Hintz CF, Dobrzycki I, Schmitz CJ, Schwichtenberg KA, Gonzalez-Rothi EJ, Sundberg CW, Streeter KA. Sex differences in spontaneous respiratory recovery following chronic C2 hemisection. J Appl Physiol (1985) 2024; 137:166-180. [PMID: 38867665 PMCID: PMC11381122 DOI: 10.1152/japplphysiol.00040.2024] [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: 01/16/2024] [Revised: 05/10/2024] [Accepted: 06/05/2024] [Indexed: 06/14/2024] Open
Abstract
Respiratory deficits after C2 hemisection (C2Hx) have been well documented through single-sex investigations. Although ovarian sex hormones enable enhanced respiratory recovery observed in females 2 wk post-C2Hx, it remains unknown if sex impacts spontaneous respiratory recovery at chronic time points. We conducted a longitudinal study to provide a comprehensive sex-based characterization of respiratory neuromuscular recovery for 8 wk after C2Hx. We recorded ventilation and chronic diaphragm electromyography (EMG) output in awake, behaving animals, phrenic motor output in anesthetized animals, and performed diaphragm muscle histology in chronically injured male and female rodents. Our results show that females expressed a greater recovery of tidal volume and minute ventilation compared with males during subacute and chronic time points. Eupneic diaphragm EMG amplitude during wakefulness and phrenic motor amplitude are similar between sexes at all time points after injury. Our data also suggest that females have a greater reduction in ipsilateral diaphragm EMG amplitude during spontaneous deep breaths (e.g., sighs) compared with males. Finally, we show evidence for atrophy and remodeling of the fast, fatigable fibers ipsilateral to injury in females, but not in males. To our knowledge, the data presented here represent the first study to report sex-dependent differences in spontaneous respiratory recovery and diaphragm muscle morphology following chronic C2Hx. These data highlight the need to study both sexes to inform evidence-based therapeutic interventions in respiratory recovery after spinal cord injury (SCI).NEW & NOTEWORTHY In response to chronic C2 hemisection, female rodents display increased tidal volume during eupneic breathing compared with males. Females show a greater reduction in diaphragm electromyography (EMG) amplitude during spontaneous deep breaths (e.g., sighs) and atrophy and remodeling of fast, fatigable diaphragm fibers. Given that most rehabilitative interventions occur in the subacute to chronic stages of injury, these results highlight the importance of considering sex when developing and evaluating therapeutics after spinal cord injury.
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Affiliation(s)
- Taylor C Holmes
- Exercise and Rehabilitation Science Program, Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin, United States
| | - Nicole M Popp
- Exercise and Rehabilitation Science Program, Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin, United States
| | - Carley F Hintz
- Exercise and Rehabilitation Science Program, Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin, United States
| | - Isabell Dobrzycki
- Exercise and Rehabilitation Science Program, Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin, United States
- Athletic and Human Performance Research Center, Marquette University, Milwaukee, Wisconsin, United States
| | - Carolyn J Schmitz
- Exercise and Rehabilitation Science Program, Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin, United States
| | - Kaylyn A Schwichtenberg
- Exercise and Rehabilitation Science Program, Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin, United States
| | - Elisa J Gonzalez-Rothi
- Department of Physical Therapy, University of Florida, Gainesville, Florida, United States
| | - Christopher W Sundberg
- Exercise and Rehabilitation Science Program, Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin, United States
- Athletic and Human Performance Research Center, Marquette University, Milwaukee, Wisconsin, United States
| | - Kristi A Streeter
- Exercise and Rehabilitation Science Program, Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin, United States
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Wang W, Yong J, Marciano P, O’Hare Doig R, Mao G, Clark J. The Translation of Nanomedicines in the Contexts of Spinal Cord Injury and Repair. Cells 2024; 13:569. [PMID: 38607008 PMCID: PMC11011097 DOI: 10.3390/cells13070569] [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: 02/11/2024] [Revised: 03/16/2024] [Accepted: 03/20/2024] [Indexed: 04/13/2024] Open
Abstract
PURPOSE OF THIS REVIEW Manipulating or re-engineering the damaged human spinal cord to achieve neuro-recovery is one of the foremost challenges of modern science. Addressing the restricted permission of neural cells and topographically organised neural tissue for self-renewal and spontaneous regeneration, respectively, is not straightforward, as exemplified by rare instances of translational success. This review assembles an understanding of advances in nanomedicine for spinal cord injury (SCI) and related clinical indications of relevance to attempts to design, engineer, and target nanotechnologies to multiple molecular networks. RECENT FINDINGS Recent research provides a new understanding of the health benefits and regulatory landscape of nanomedicines based on a background of advances in mRNA-based nanocarrier vaccines and quantum dot-based optical imaging. In relation to spinal cord pathology, the extant literature details promising advances in nanoneuropharmacology and regenerative medicine that inform the present understanding of the nanoparticle (NP) biocompatibility-neurotoxicity relationship. In this review, the conceptual bases of nanotechnology and nanomaterial chemistry covering organic and inorganic particles of sizes generally less than 100 nm in diameter will be addressed. Regarding the centrally active nanotechnologies selected for this review, attention is paid to NP physico-chemistry, functionalisation, delivery, biocompatibility, biodistribution, toxicology, and key molecular targets and biological effects intrinsic to and beyond the spinal cord parenchyma. SUMMARY The advance of nanotechnologies for the treatment of refractory spinal cord pathologies requires an in-depth understanding of neurobiological and topographical principles and a consideration of additional complexities involving the research's translational and regulatory landscapes.
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Affiliation(s)
- Wenqian Wang
- School of Chemical Engineering, University of New South Wales (UNSW), Kensington, NSW 2052, Australia; (W.W.); (J.Y.); (G.M.)
| | - Joel Yong
- School of Chemical Engineering, University of New South Wales (UNSW), Kensington, NSW 2052, Australia; (W.W.); (J.Y.); (G.M.)
| | - Paul Marciano
- Adelaide Medical School, University of Adelaide, Adelaide, SA 5005, Australia; (P.M.); (R.O.D.)
- Neil Sachse Centre for Spinal Cord Research, Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA 5000, Australia
| | - Ryan O’Hare Doig
- Adelaide Medical School, University of Adelaide, Adelaide, SA 5005, Australia; (P.M.); (R.O.D.)
- Neil Sachse Centre for Spinal Cord Research, Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA 5000, Australia
| | - Guangzhao Mao
- School of Chemical Engineering, University of New South Wales (UNSW), Kensington, NSW 2052, Australia; (W.W.); (J.Y.); (G.M.)
| | - Jillian Clark
- Adelaide Medical School, University of Adelaide, Adelaide, SA 5005, Australia; (P.M.); (R.O.D.)
- Neil Sachse Centre for Spinal Cord Research, Lifelong Health Theme, South Australian Health and Medical Research Institute, North Terrace, Adelaide, SA 5000, Australia
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3
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Jensen VN, Huffman EE, Jalufka FL, Pritchard AL, Baumgartner S, Walling I, C. Gibbs H, McCreedy DA, Alilain WJ, Crone SA. V2a neurons restore diaphragm function in mice following spinal cord injury. Proc Natl Acad Sci U S A 2024; 121:e2313594121. [PMID: 38442182 PMCID: PMC10945804 DOI: 10.1073/pnas.2313594121] [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] [Accepted: 01/15/2024] [Indexed: 03/07/2024] Open
Abstract
The specific roles that different types of neurons play in recovery from injury is poorly understood. Here, we show that increasing the excitability of ipsilaterally projecting, excitatory V2a neurons using designer receptors exclusively activated by designer drugs (DREADDs) restores rhythmic bursting activity to a previously paralyzed diaphragm within hours, days, or weeks following a C2 hemisection injury. Further, decreasing the excitability of V2a neurons impairs tonic diaphragm activity after injury as well as activation of inspiratory activity by chemosensory stimulation, but does not impact breathing at rest in healthy animals. By examining the patterns of muscle activity produced by modulating the excitability of V2a neurons, we provide evidence that V2a neurons supply tonic drive to phrenic circuits rather than increase rhythmic inspiratory drive at the level of the brainstem. Our results demonstrate that the V2a class of neurons contribute to recovery of respiratory function following injury. We propose that altering V2a excitability is a potential strategy to prevent respiratory motor failure and promote recovery of breathing following spinal cord injury.
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Affiliation(s)
- Victoria N. Jensen
- Neuroscience Graduate Program, University of Cincinnati College of Medicine, Cincinnati, OH45219
| | - Emily E. Huffman
- Department of Neuroscience, University of Kentucky College of Medicine, Lexington, KY40536
- Spinal Cord and Brain Injury Research Center, University of Kentucky College of Medicine, Lexington, KY40536
| | - Frank L. Jalufka
- Department of Biology, Texas A&M University, College Station, TX77843
| | - Anna L. Pritchard
- Department of Biomedical Engineering, Texas A&M University, College Station, TX77843
| | - Sarah Baumgartner
- Division of Neurosurgery, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH45229
| | - Ian Walling
- Neuroscience Graduate Program, University of Cincinnati College of Medicine, Cincinnati, OH45219
- Medical Scientist Training Program, University of Cincinnati College of Medicine, Cincinnati, OH45267
| | - Holly C. Gibbs
- Department of Biomedical Engineering, Texas A&M University, College Station, TX77843
- Microscopy and Imaging Center, Texas A&M University, College Station, TX77843
| | - Dylan A. McCreedy
- Department of Biology, Texas A&M University, College Station, TX77843
- Department of Biomedical Engineering, Texas A&M University, College Station, TX77843
- Texas A&M Institute for Neuroscience, Texas A&M University, College Station, TX77843
| | - Warren J. Alilain
- Department of Neuroscience, University of Kentucky College of Medicine, Lexington, KY40536
- Spinal Cord and Brain Injury Research Center, University of Kentucky College of Medicine, Lexington, KY40536
| | - Steven A. Crone
- Division of Neurosurgery, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH45229
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH45229
- Department of Neurosurgery, University of Cincinnati College of Medicine, Cincinnati, OH45267
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Yu D, Zeng X, Aljuboori ZS, Dennison R, Wu L, Anderson JA, Teng YD. T12-L3 Nerve Transfer-Induced Locomotor Recovery in Rats with Thoracolumbar Contusion: Essential Roles of Sensory Input Rerouting and Central Neuroplasticity. Cells 2023; 12:2804. [PMID: 38132124 PMCID: PMC10741684 DOI: 10.3390/cells12242804] [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: 10/09/2023] [Revised: 11/28/2023] [Accepted: 12/05/2023] [Indexed: 12/23/2023] Open
Abstract
Locomotor recovery after spinal cord injury (SCI) remains an unmet challenge. Nerve transfer (NT), the connection of a functional/expendable peripheral nerve to a paralyzed nerve root, has long been clinically applied, aiming to restore motor control. However, outcomes have been inconsistent, suggesting that NT-induced neurological reinstatement may require activation of mechanisms beyond motor axon reinnervation (our hypothesis). We previously reported that to enhance rat locomotion following T13-L1 hemisection, T12-L3 NT must be performed within timeframes optimal for sensory nerve regrowth. Here, T12-L3 NT was performed for adult female rats with subacute (7-9 days) or chronic (8 weeks) mild (SCImi: 10 g × 12.5 mm) or moderate (SCImo: 10 g × 25 mm) T13-L1 thoracolumbar contusion. For chronic injuries, T11-12 implantation of adult hMSCs (1-week before NT), post-NT intramuscular delivery of FGF2, and environmentally enriched/enlarged (EEE) housing were provided. NT, not control procedures, qualitatively improved locomotion in both SCImi groups and animals with subacute SCImo. However, delayed NT did not produce neurological scale upgrading conversion for SCImo rats. Ablation of the T12 ventral/motor or dorsal/sensory root determined that the T12-L3 sensory input played a key role in hindlimb reanimation. Pharmacological, electrophysiological, and trans-synaptic tracing assays revealed that NT strengthened integrity of the propriospinal network, serotonergic neuromodulation, and the neuromuscular junction. Besides key outcomes of thoracolumbar contusion modeling, the data provides the first evidence that mixed NT-induced locomotor efficacy may rely pivotally on sensory rerouting and pro-repair neuroplasticity to reactivate neurocircuits/central pattern generators. The finding describes a novel neurobiology mechanism underlying NT, which can be targeted for development of innovative neurotization therapies.
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Affiliation(s)
- Dou Yu
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA 02129, USA
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
- Laboratory of SCI, Stem Cell and Recovery Neurobiology Research, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Mass General Brigham, Harvard Medical School, Boston, MA 02129, USA
| | - Xiang Zeng
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA 02129, USA
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
- Laboratory of SCI, Stem Cell and Recovery Neurobiology Research, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Mass General Brigham, Harvard Medical School, Boston, MA 02129, USA
| | - Zaid S. Aljuboori
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA 02129, USA
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
- Laboratory of SCI, Stem Cell and Recovery Neurobiology Research, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Mass General Brigham, Harvard Medical School, Boston, MA 02129, USA
| | - Rachel Dennison
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA 02129, USA
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
- Laboratory of SCI, Stem Cell and Recovery Neurobiology Research, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Mass General Brigham, Harvard Medical School, Boston, MA 02129, USA
| | - Liquan Wu
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA 02129, USA
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
- Laboratory of SCI, Stem Cell and Recovery Neurobiology Research, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Mass General Brigham, Harvard Medical School, Boston, MA 02129, USA
| | - Jamie A. Anderson
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA 02129, USA
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
- Laboratory of SCI, Stem Cell and Recovery Neurobiology Research, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Mass General Brigham, Harvard Medical School, Boston, MA 02129, USA
| | - Yang D. Teng
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA 02129, USA
- Department of Neurosurgery, Harvard Medical School, Boston, MA 02115, USA
- Laboratory of SCI, Stem Cell and Recovery Neurobiology Research, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Mass General Brigham, Harvard Medical School, Boston, MA 02129, USA
- Neurotrauma Recovery Research, Spaulding Rehabilitation Hospital Network, Mass General Brigham, Harvard Medical School, Boston, MA 02129, USA
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5
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Milton AJ, Kwok JC, McClellan J, Randall SG, Lathia JD, Warren PM, Silver DJ, Silver J. Recovery of Forearm and Fine Digit Function After Chronic Spinal Cord Injury by Simultaneous Blockade of Inhibitory Matrix Chondroitin Sulfate Proteoglycan Production and the Receptor PTPσ. J Neurotrauma 2023; 40:2500-2521. [PMID: 37606910 PMCID: PMC10698859 DOI: 10.1089/neu.2023.0117] [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] [Indexed: 08/23/2023] Open
Abstract
Spinal cord injuries (SCI), for which there are limited effective treatments, result in enduring paralysis and hypoesthesia, in part because of the inhibitory microenvironment that develops and limits regeneration/sprouting, especially during chronic stages. Recently, we discovered that targeted enzymatic removal of the inhibitory chondroitin sulfate proteoglycan (CSPG) component of the extracellular and perineuronal net (PNN) matrix via Chondroitinase ABC (ChABC) rapidly restored robust respiratory function to the previously paralyzed hemi-diaphragm after remarkably long times post-injury (up to 1.5 years) following a cervical level 2 lateral hemi-transection. Importantly, ChABC treatment at cervical level 4 in this chronic model also elicited improvements in gross upper arm function. In the present study, we focused on arm and hand function, seeking to highlight and optimize crude as well as fine motor control of the forearm and digits at lengthy chronic stages post-injury. However, instead of using ChABC, we utilized a novel and more clinically relevant systemic combinatorial treatment strategy designed to simultaneously reduce and overcome inhibitory CSPGs. Following a 3-month upper cervical spinal hemi-lesion using adult female Sprague Dawley rats, we show that the combined treatment had a profound effect on functional recovery of the chronically paralyzed forelimb and paw, as well as on precision movements of the digits. The regenerative and immune system related events that we describe deepen our basic understanding of the crucial role of CSPG-mediated inhibition via the PTPσ receptor in constraining functional synaptic plasticity at lengthy time points following SCI, hopefully leading to clinically relevant translational benefits.
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Affiliation(s)
- Adrianna J. Milton
- Department of Neurosciences, Case Western Reserve University, Cleveland, Ohio, USA
| | - Jessica C.F. Kwok
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- Institute of Experimental Medicine, Czech Academy of Science, Prague, Czech Republic
| | - Jacob McClellan
- Department of Neurosciences, Case Western Reserve University, Cleveland, Ohio, USA
| | - Sabre G. Randall
- Department of Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, USA
| | - Justin D. Lathia
- Department of Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, USA
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine at Case Western Reserve University, Cleveland, Ohio, USA
| | - Philippa M. Warren
- Department of Neurosciences, Case Western Reserve University, Cleveland, Ohio, USA
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Daniel J. Silver
- Department of Neurosciences, Case Western Reserve University, Cleveland, Ohio, USA
- Department of Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, USA
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine at Case Western Reserve University, Cleveland, Ohio, USA
| | - Jerry Silver
- Department of Neurosciences, Case Western Reserve University, Cleveland, Ohio, USA
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Kawamura K, Kobayashi M, Tomita K. Routine hypercapnic challenge after cervical spinal hemisection affects the size of phrenic motoneurons. Sci Rep 2023; 13:13905. [PMID: 37626145 PMCID: PMC10457361 DOI: 10.1038/s41598-023-40505-x] [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: 11/18/2022] [Accepted: 08/11/2023] [Indexed: 08/27/2023] Open
Abstract
After an individual experiences a cervical cord injury, the cell body's adaptation to the smaller size of phrenic motoneurons occurs within several weeks. It is not known whether a routine hypercapnic load can alter this adaptation of phrenic motoneurons. We investigated this question by using rats with high cervical cord hemisection. The rats were divided into four groups: control, hypercapnia, sham, and sham hypercapnia. Within 72 h post-hemisection, the hypercapnia groups began a hypercapnic challenge (20 min/day, 4 times/week for 3 weeks) with 7% CO2 under awake conditions. After the 3-week challenge, the phrenic motoneurons in all of the rats were retrogradely labeled with horseradish peroxidase, and the motoneuron sizes in each group were compared. The average diameter, cross-sectional area, and somal surface area of stained phrenic motoneurons as analyzed by software were significantly smaller in only the control group compared to the other groups. The histogram distribution was unimodal, with larger between-group size differences for motoneurons in the horizontal plane than in the transverse plane. Our findings indicate that a routine hypercapnic challenge may increase the input to phrenic motoneurons and alter the propensity for motoneuron adaptations.
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Affiliation(s)
- Kenta Kawamura
- Department of Physical Therapy, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-Machi, Inashiki-Gun, Ibaraki, 300-0394, Japan.
- Graduate School of Health Science, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-Machi, Inashiki-Gun, Ibaraki, 300-0394, Japan.
| | - Masaaki Kobayashi
- Graduate School of Health Science, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-Machi, Inashiki-Gun, Ibaraki, 300-0394, Japan
| | - Kazuhide Tomita
- Department of Physical Therapy, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-Machi, Inashiki-Gun, Ibaraki, 300-0394, Japan
- Graduate School of Health Science, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-Machi, Inashiki-Gun, Ibaraki, 300-0394, Japan
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7
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Michel-Flutot P, Lane MA, Lepore AC, Vinit S. Therapeutic Strategies Targeting Respiratory Recovery after Spinal Cord Injury: From Preclinical Development to Clinical Translation. Cells 2023; 12:1519. [PMID: 37296640 PMCID: PMC10252981 DOI: 10.3390/cells12111519] [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: 04/14/2023] [Revised: 05/15/2023] [Accepted: 05/29/2023] [Indexed: 06/12/2023] Open
Abstract
High spinal cord injuries (SCIs) lead to permanent functional deficits, including respiratory dysfunction. Patients living with such conditions often rely on ventilatory assistance to survive, and even those that can be weaned continue to suffer life-threatening impairments. There is currently no treatment for SCI that is capable of providing complete recovery of diaphragm activity and respiratory function. The diaphragm is the main inspiratory muscle, and its activity is controlled by phrenic motoneurons (phMNs) located in the cervical (C3-C5) spinal cord. Preserving and/or restoring phMN activity following a high SCI is essential for achieving voluntary control of breathing. In this review, we will highlight (1) the current knowledge of inflammatory and spontaneous pro-regenerative processes occurring after SCI, (2) key therapeutics developed to date, and (3) how these can be harnessed to drive respiratory recovery following SCIs. These therapeutic approaches are typically first developed and tested in relevant preclinical models, with some of them having been translated into clinical studies. A better understanding of inflammatory and pro-regenerative processes, as well as how they can be therapeutically manipulated, will be the key to achieving optimal functional recovery following SCIs.
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Affiliation(s)
- Pauline Michel-Flutot
- END-ICAP, UVSQ, Inserm, Université Paris-Saclay, 78000 Versailles, France;
- Department of Neuroscience, Jefferson Synaptic Biology Center, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA;
| | - Michael A. Lane
- Marion Murray Spinal Cord Research Center, Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA;
| | - Angelo C. Lepore
- Department of Neuroscience, Jefferson Synaptic Biology Center, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA;
| | - Stéphane Vinit
- END-ICAP, UVSQ, Inserm, Université Paris-Saclay, 78000 Versailles, France;
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8
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Wang W, Hassan MM, Mao G. Colloidal Perspective on Targeted Drug Delivery to the Central Nervous System. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:3235-3245. [PMID: 36825490 DOI: 10.1021/acs.langmuir.2c02949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
This article describes a new approach in targeted drug delivery to the central nervous system (CNS) in a significant departure from the predominant systematic drug administration attempting to penetrate the blood-brain barrier (BBB). Nanoparticles chemically conjugated to neural tract tracer proteins are capable of path-specific axonal retrograde transport, transneuronal transport, and anatomical tract flow to bypass the BBB. To celebrate the work by Dr. Bettye Washington Greene on the physical chemistry of colloidal particles, this article focuses on the physiochemical characteristics of the nanoparticles, various colloidal forces that impact the colloidal stability of nanoparticles in biological media, and surface chemistry strategies to avoid nanoparticle aggregation-induced poor therapeutic outcomes. The biological environment for the anatomical retrograde transport of neural tract tracers is examined to directly link factors impacting the colloidal stability of the new class of CNS-targeting nanoconjugates such as nanoconjugate size, shape, surface charge, surface chemistry, ionic strength, pH, and protein adsorption on the nanoparticle. We conclude with opportunities and challenges for future research.
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Affiliation(s)
- Wenqian Wang
- School of Chemical Engineering, University of New South Wales (UNSW Sydney), Sydney, New South Wales 2052, Australia
| | - Md Musfizur Hassan
- School of Chemical Engineering, University of New South Wales (UNSW Sydney), Sydney, New South Wales 2052, Australia
| | - Guangzhao Mao
- School of Chemical Engineering, University of New South Wales (UNSW Sydney), Sydney, New South Wales 2052, Australia
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9
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Pitts T, Iceman KE. Deglutition and the Regulation of the Swallow Motor Pattern. Physiology (Bethesda) 2023; 38:0. [PMID: 35998250 PMCID: PMC9707372 DOI: 10.1152/physiol.00005.2021] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 08/19/2022] [Accepted: 08/19/2022] [Indexed: 11/22/2022] Open
Abstract
Despite centuries of investigation, questions and controversies remain regarding the fundamental genesis and motor pattern of swallow. Two significant topics include inspiratory muscle activity during swallow (Schluckatmung, i.e., "swallow-breath") and anatomical boundaries of the swallow pattern generator. We discuss the long history of reports regarding the presence or absence of Schluckatmung and the possible advantages of and neural basis for such activity, leading to current theories and novel experimental directions.
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Affiliation(s)
- Teresa Pitts
- Department of Neurological Surgery, Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky
| | - Kimberly E Iceman
- Department of Neurological Surgery, Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky
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10
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Locke KC, Randelman ML, Hoh DJ, Zholudeva LV, Lane MA. Respiratory plasticity following spinal cord injury: perspectives from mouse to man. Neural Regen Res 2022; 17:2141-2148. [PMID: 35259820 PMCID: PMC9083159 DOI: 10.4103/1673-5374.335839] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 09/18/2021] [Accepted: 10/20/2021] [Indexed: 12/03/2022] Open
Abstract
The study of respiratory plasticity in animal models spans decades. At the bench, researchers use an array of techniques aimed at harnessing the power of plasticity within the central nervous system to restore respiration following spinal cord injury. This field of research is highly clinically relevant. People living with cervical spinal cord injury at or above the level of the phrenic motoneuron pool at spinal levels C3-C5 typically have significant impairments in breathing which may require assisted ventilation. Those who are ventilator dependent are at an increased risk of ventilator-associated co-morbidities and have a drastically reduced life expectancy. Pre-clinical research examining respiratory plasticity in animal models has laid the groundwork for clinical trials. Despite how widely researched this injury is in animal models, relatively few treatments have broken through the preclinical barrier. The three goals of this present review are to define plasticity as it pertains to respiratory function post-spinal cord injury, discuss plasticity models of spinal cord injury used in research, and explore the shift from preclinical to clinical research. By investigating current targets of respiratory plasticity research, we hope to illuminate preclinical work that can influence future clinical investigations and the advancement of treatments for spinal cord injury.
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Affiliation(s)
- Katherine C. Locke
- Department of Neurobiology & Anatomy, Drexel University, Philadelphia, PA, USA
- Marion Murray Spinal Cord Research Center, Philadelphia, PA, USA
| | - Margo L. Randelman
- Department of Neurobiology & Anatomy, Drexel University, Philadelphia, PA, USA
- Marion Murray Spinal Cord Research Center, Philadelphia, PA, USA
| | - Daniel J. Hoh
- Lillian S. Wells Department of Neurosurgery, University of Florida, Gainesville, FL, USA
| | - Lyandysha V. Zholudeva
- Marion Murray Spinal Cord Research Center, Philadelphia, PA, USA
- Cardiovascular Disease, Gladstone Institutes, San Francisco, CA, USA
| | - Michael A. Lane
- Department of Neurobiology & Anatomy, Drexel University, Philadelphia, PA, USA
- Marion Murray Spinal Cord Research Center, Philadelphia, PA, USA
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11
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Pitts T, Iceman KE, Huff A, Musselwhite MN, Frazure ML, Young KC, Greene CL, Howland DR. Laryngeal and swallow dysregulation following acute cervical spinal cord injury. J Neurophysiol 2022; 128:405-417. [PMID: 35830612 PMCID: PMC9359645 DOI: 10.1152/jn.00469.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Laryngeal function is vital to airway protection. While swallow is mediated by the brainstem, mechanisms underlying increased risk of dysphagia after cervical spinal cord injury (SCI) are unknown. We hypothesized that loss of descending phrenic drive affects swallow and breathing differently, and loss of ascending spinal afferent information alters swallow regulation. We recorded electromyograms from upper airway and chest wall muscles in freely breathing pentobarbital-anesthetized cats and rats. Inspiratory laryngeal activity increased ~two-fold following C2 lateral-hemisection. Ipsilateral to the injury, crural diaphragm EMG amplitude was reduced during breathing (62 ± 25% change post-injury), but no animal had complete termination of activity; 75% of animals increased contralateral diaphragm recruitment, but this did not reach significance. During swallow, laryngeal adductor and pharyngeal constrictor muscles increased activity, and diaphragm activity was bilaterally suppressed. This was unexpected because of the ipsilateral-specific response during breathing. Swallow-breathing coordination was also disrupted and more swallows occurred during early expiration. Finally, to determine if the chest wall is a major source of feedback for laryngeal regulation, we performed T1 total transections in rats. As in the C2 lateral-hemisection, inspiratory laryngeal recruitment was the first feature noted. In contrast to the C2 lateral-hemisection, diaphragmatic drive increased after T1 transection. Overall, we found that SCI alters laryngeal drive during swallow and breathing, and reduced swallow-related diaphragm activity. Our results show behavior-specific effects, suggesting SCI affects swallow more than breathing, and emphasizes the need for additional studies on the effects of ascending afferents from the spinal cord on laryngeal function.
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Affiliation(s)
- Teresa Pitts
- Kentucky Spinal Cord Injury Center, Department of Neurological Surgery, University of Louisville, Louisville, KY, United States
| | - Kimberly E Iceman
- Kentucky Spinal Cord Injury Center, Department of Neurological Surgery, University of Louisville, Louisville, KY, United States
| | - Alyssa Huff
- Center for Integrative Brain Research, Seattle Children's Hospital, Seattle, WA, United States
| | - Matthew Nicholas Musselwhite
- Kentucky Spinal Cord Injury Center, Department of Neurological Surgery, University of Louisville, Louisville, KY, United States
| | - Michael L Frazure
- Kentucky Spinal Cord Injury Center, Department of Neurological Surgery, University of Louisville, Louisville, KY, United States
| | - Kellyanna C Young
- Kentucky Spinal Cord Injury Center, Department of Neurological Surgery, University of Louisville, Louisville, KY, United States
| | - Clinton L Greene
- Kentucky Spinal Cord Injury Center, Department of Neurological Surgery, University of Louisville, Louisville, KY, United States
| | - Dena Ruth Howland
- Kentucky Spinal Cord Injury Center, Department of Neurological Surgery, University of Louisville, Louisville, KY, United States.,Research Service, Robley Rex VA Medical Center, Louisville, KY, United States
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12
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Bajjig A, Michel-Flutot P, Migevent T, Cayetanot F, Bodineau L, Vinit S, Vivodtzev I. Diaphragmatic Activity and Respiratory Function Following C3 or C6 Unilateral Spinal Cord Contusion in Mice. BIOLOGY 2022; 11:biology11040558. [PMID: 35453757 PMCID: PMC9031817 DOI: 10.3390/biology11040558] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 04/01/2022] [Accepted: 04/04/2022] [Indexed: 06/12/2023]
Abstract
The majority of spinal cord injuries (SCIs) are cervical (cSCI), leading to a marked reduction in respiratory capacity. We aimed to investigate the effect of hemicontusion models of cSCI on both diaphragm activity and respiratory function to serve as preclinical models of cervical SCI. Since phrenic motoneuron pools are located at the C3-C5 spinal level, we investigated two models of preclinical cSCI mimicking human forms of injury, namely, one above (C3 hemicontusion-C3HC) and one below phrenic motoneuron pools (C6HC) in wild-type swiss OF-1 mice, and we compared their effects on respiratory function using whole-body plethysmography and on diaphragm activity using electromyography (EMG). At 7 days post-surgery, both C3HC and C6HC damaged spinal cord integrity above the lesion level, suggesting that C6HC potentially alters C5 motoneurons. Although both models led to decreased diaphragmatic EMG activity in the injured hemidiaphragm compared to the intact one (-46% and -26% in C3HC and C6HC, respectively, both p = 0.02), only C3HC led to a significant reduction in tidal volume and minute ventilation compared to sham surgery (-25% and -20% vs. baseline). Moreover, changes in EMG amplitude between respiratory bursts were observed post-C3HC, reflecting a change in phrenic motoneuronal excitability. Hence, C3HC and C6HC models induced alteration in respiratory function proportionally to injury level, and the C3HC model is a more appropriate model for interventional studies aiming to restore respiratory function in cSCI.
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Affiliation(s)
- Afaf Bajjig
- Inserm, UMR_S1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Sorbonne Université, 75013 Paris, France; (A.B.); (T.M.); (F.C.); (L.B.)
| | - Pauline Michel-Flutot
- Inserm, END-ICAP, Université Paris-Saclay, UVSQ, 78000 Versailles, France; (P.M.-F.); (S.V.)
| | - Tiffany Migevent
- Inserm, UMR_S1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Sorbonne Université, 75013 Paris, France; (A.B.); (T.M.); (F.C.); (L.B.)
| | - Florence Cayetanot
- Inserm, UMR_S1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Sorbonne Université, 75013 Paris, France; (A.B.); (T.M.); (F.C.); (L.B.)
| | - Laurence Bodineau
- Inserm, UMR_S1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Sorbonne Université, 75013 Paris, France; (A.B.); (T.M.); (F.C.); (L.B.)
| | - Stéphane Vinit
- Inserm, END-ICAP, Université Paris-Saclay, UVSQ, 78000 Versailles, France; (P.M.-F.); (S.V.)
| | - Isabelle Vivodtzev
- Inserm, UMR_S1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Sorbonne Université, 75013 Paris, France; (A.B.); (T.M.); (F.C.); (L.B.)
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13
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Effects of Chronic High-Frequency rTMS Protocol on Respiratory Neuroplasticity Following C2 Spinal Cord Hemisection in Rats. BIOLOGY 2022; 11:biology11030473. [PMID: 35336846 PMCID: PMC8945729 DOI: 10.3390/biology11030473] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 03/14/2022] [Accepted: 03/16/2022] [Indexed: 11/22/2022]
Abstract
Simple Summary High spinal cord injuries (SCIs) are known to lead to permanent diaphragmatic paralysis, and to induce deleterious post-traumatic inflammatory processes following cervical spinal cord injury. We used a noninvasive therapeutic tool (repetitive transcranial magnetic stimulation (rTMS)), to harness plasticity in spared descending respiratory circuit and reduce the inflammatory processes. Briefly, the results obtained in this present study suggest that chronic high-frequency rTMS can ameliorate respiratory dysfunction and elicit neuronal plasticity with a reduction in deleterious post-traumatic inflammatory processes in the cervical spinal cord post-SCI. Thus, this therapeutic tool could be adopted and/or combined with other therapeutic interventions in order to further enhance beneficial outcomes. Abstract High spinal cord injuries (SCIs) lead to permanent diaphragmatic paralysis. The search for therapeutics to induce functional motor recovery is essential. One promising noninvasive therapeutic tool that could harness plasticity in a spared descending respiratory circuit is repetitive transcranial magnetic stimulation (rTMS). Here, we tested the effect of chronic high-frequency (10 Hz) rTMS above the cortical areas in C2 hemisected rats when applied for 7 days, 1 month, or 2 months. An increase in intact hemidiaphragm electromyogram (EMG) activity and excitability (diaphragm motor evoked potentials) was observed after 1 month of rTMS application. Interestingly, despite no real functional effects of rTMS treatment on the injured hemidiaphragm activity during eupnea, 2 months of rTMS treatment strengthened the existing crossed phrenic pathways, allowing the injured hemidiaphragm to increase its activity during the respiratory challenge (i.e., asphyxia). This effect could be explained by a strengthening of respiratory descending fibers in the ventrolateral funiculi (an increase in GAP-43 positive fibers), sustained by a reduction in inflammation in the C1–C3 spinal cord (reduction in CD68 and Iba1 labeling), and acceleration of intracellular plasticity processes in phrenic motoneurons after chronic rTMS treatment. These results suggest that chronic high-frequency rTMS can ameliorate respiratory dysfunction and elicit neuronal plasticity with a reduction in deleterious post-traumatic inflammatory processes in the cervical spinal cord post-SCI. Thus, this therapeutic tool could be adopted and/or combined with other therapeutic interventions in order to further enhance beneficial outcomes.
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14
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Malone IG, Kelly MN, Nosacka RL, Nash MA, Yue S, Xue W, Otto KJ, Dale EA. Closed-Loop, Cervical, Epidural Stimulation Elicits Respiratory Neuroplasticity after Spinal Cord Injury in Freely Behaving Rats. eNeuro 2022; 9:ENEURO.0426-21.2021. [PMID: 35058311 PMCID: PMC8856702 DOI: 10.1523/eneuro.0426-21.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 12/08/2021] [Accepted: 12/24/2021] [Indexed: 11/28/2022] Open
Abstract
Over half of all spinal cord injuries (SCIs) are cervical, which can lead to paralysis and respiratory compromise, causing significant morbidity and mortality. Effective treatments to restore breathing after severe upper cervical injury are lacking; thus, it is imperative to develop therapies to address this. Epidural stimulation has successfully restored motor function after SCI for stepping, standing, reaching, grasping, and postural control. We hypothesized that closed-loop stimulation triggered via healthy hemidiaphragm EMG activity has the potential to elicit functional neuroplasticity in spinal respiratory pathways after cervical SCI (cSCI). To test this, we delivered closed-loop, electrical, epidural stimulation (CLES) at the level of the phrenic motor nucleus (C4) for 3 d after C2 hemisection (C2HS) in freely behaving rats. A 2 × 2 Latin Square experimental design incorporated two treatments, C2HS injury and CLES therapy resulting in four groups of adult, female Sprague Dawley rats: C2HS + CLES (n = 8), C2HS (n = 6), intact + CLES (n = 6), intact (n = 6). In stimulated groups, CLES was delivered for 12-20 h/d for 3 d. After C2HS, 3 d of CLES robustly facilitated the slope of stimulus-response curves of ipsilesional spinal motor evoked potentials (sMEPs) versus nonstimulated controls. To our knowledge, this is the first demonstration of CLES eliciting respiratory neuroplasticity after C2HS in freely behaving animals. These findings suggest CLES as a promising future therapy to address respiratory deficiency associated with cSCI.
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Affiliation(s)
- Ian G Malone
- Department of Electrical and Computer Engineering, University of Florida, Gainesville, FL 32611
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL 32611
| | - Mia N Kelly
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL 32611
- Department of Physical Therapy, University of Florida, Gainesville, FL 32611
| | - Rachel L Nosacka
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL 32611
| | - Marissa A Nash
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL 32611
| | - Sijia Yue
- Department of Biostatistics, University of Florida, Gainesville, FL 32611
| | - Wei Xue
- Department of Biostatistics, University of Florida, Gainesville, FL 32611
| | - Kevin J Otto
- Department of Electrical and Computer Engineering, University of Florida, Gainesville, FL 32611
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL 32611
- McKnight Brain Institute, University of Florida, Gainesville, FL 32611
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL 32611
- Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611
- Department of Neurology, University of Florida, Gainesville, FL 32611
- Department of Neuroscience, University of Florida, Gainesville, FL 32611
| | - Erica A Dale
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL 32611
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL 32611
- McKnight Brain Institute, University of Florida, Gainesville, FL 32611
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15
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Chiu TT, Lee KZ. Impact of cervical spinal cord injury on the relationship between the metabolism and ventilation in rats. J Appl Physiol (1985) 2021; 131:1799-1814. [PMID: 34647826 DOI: 10.1152/japplphysiol.00472.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cervical spinal cord injury typically results in respiratory impairments. Clinical and animal studies have demonstrated that respiratory function can spontaneously and partially recover over time after injury. However, it remains unclear whether respiratory recovery is associated with alterations in metabolism. The present study was designed to comprehensively examine ventilation and metabolism in a rat model of spinal cord injury. Adult male rats received sham (i.e., laminectomy) or unilateral mid-cervical contusion injury (height of impact rod: 6.25 or 12.5 mm). Breathing patterns and whole body metabolism (O2 consumption and CO2 production) were measured using a whole body plethysmography system conjugated with flow controllers and gas analyzer at the acute (1 day postinjury), subchronic (2 wk postinjury), and chronic (8 wk postinjury) injury stages. The results demonstrated that mid-cervical contusion caused a significant reduction in the tidal volume. Although the tidal volume of contused animals can gradually recover, it remains lower than that of uninjured animals at the chronic injury stage. Although O2 consumption and CO2 production were similar between uninjured and contused animals at the acute injury stage, these two metabolic parameters were significantly reduced in contused animals at the subchronic to chronic injury stages. Additionally, the relationships between ventilation, metabolism, and body temperature were altered by cervical spinal cord injury. These results suggest that cervical spinal cord injury causes a complicated reconfiguration of ventilation and metabolism that may enable injured animals to maintain a suitable homeostasis for adapting to the pathophysiological consequences of injury.NEW & NOTEWORTHY Ventilation and metabolism are tightly coupled to maintain appropriate energy expenditure under physiological conditions. Our findings demonstrate that cervical spinal cord injury results in the differential reduction of ventilation and metabolism at the various injury stages and leads to alterations in the relationship between ventilation and metabolism. These results from an animal model provide fundamental knowledge for understanding how cervical spinal cord injury impacts energy homeostasis.
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Affiliation(s)
- Tzu-Ting Chiu
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
| | - Kun-Ze Lee
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan.,Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung, Taiwan
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16
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Allen LL, Nichols NL, Asa ZA, Emery AT, Ciesla MC, Santiago JV, Holland AE, Mitchell GS, Gonzalez-Rothi EJ. Phrenic motor neuron survival below cervical spinal cord hemisection. Exp Neurol 2021; 346:113832. [PMID: 34363808 PMCID: PMC9065093 DOI: 10.1016/j.expneurol.2021.113832] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 07/31/2021] [Accepted: 08/02/2021] [Indexed: 02/04/2023]
Abstract
Cervical spinal cord injury (cSCI) severs bulbospinal projections to respiratory motor neurons, paralyzing respiratory muscles below the injury. C2 spinal hemisection (C2Hx) is a model of cSCI often used to study spontaneous and induced plasticity and breathing recovery post-injury. One key assumption is that C2Hx dennervates motor neurons below the injury, but does not affect their survival. However, a recent study reported substantial bilateral motor neuron death caudal to C2Hx. Since phrenic motor neuron (PMN) death following C2Hx would have profound implications for therapeutic strategies designed to target spared neural circuits, we tested the hypothesis that C2Hx minimally impacts PMN survival. Using improved retrograde tracing methods, we observed no loss of PMNs at 2- or 8-weeks post-C2Hx. We also observed no injury-related differences in ChAT or NeuN immunolabeling within labelled PMNs. Although we found no evidence of PMN loss following C2Hx, we cannot rule out neuronal loss in other motor pools. These findings address an essential prerequisite for studies that utilize C2Hx as a model to explore strategies for inducing plasticity and/or regeneration within the phrenic motor system, as they provide important insights into the viability of phrenic motor neurons as therapeutic targets after high cervical injury.
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Affiliation(s)
- Latoya L Allen
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Nicole L Nichols
- Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65211, USA
| | - Zachary A Asa
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | | | - Marissa C Ciesla
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Juliet V Santiago
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Ashley E Holland
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Gordon S Mitchell
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Elisa J Gonzalez-Rothi
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA.
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17
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Randelman M, Zholudeva LV, Vinit S, Lane MA. Respiratory Training and Plasticity After Cervical Spinal Cord Injury. Front Cell Neurosci 2021; 15:700821. [PMID: 34621156 PMCID: PMC8490715 DOI: 10.3389/fncel.2021.700821] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 08/11/2021] [Indexed: 12/30/2022] Open
Abstract
While spinal cord injuries (SCIs) result in a vast array of functional deficits, many of which are life threatening, the majority of SCIs are anatomically incomplete. Spared neural pathways contribute to functional and anatomical neuroplasticity that can occur spontaneously, or can be harnessed using rehabilitative, electrophysiological, or pharmacological strategies. With a focus on respiratory networks that are affected by cervical level SCI, the present review summarizes how non-invasive respiratory treatments can be used to harness this neuroplastic potential and enhance long-term recovery. Specific attention is given to "respiratory training" strategies currently used clinically (e.g., strength training) and those being developed through pre-clinical and early clinical testing [e.g., intermittent chemical stimulation via altering inhaled oxygen (hypoxia) or carbon dioxide stimulation]. Consideration is also given to the effect of training on non-respiratory (e.g., locomotor) networks. This review highlights advances in this area of pre-clinical and translational research, with insight into future directions for enhancing plasticity and improving functional outcomes after SCI.
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Affiliation(s)
- Margo Randelman
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States.,Marion Murray Spinal Cord Research Center, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Lyandysha V Zholudeva
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States.,Marion Murray Spinal Cord Research Center, Drexel University College of Medicine, Philadelphia, PA, United States.,Gladstone Institutes, San Francisco, CA, United States
| | - Stéphane Vinit
- INSERM, END-ICAP, Université Paris-Saclay, UVSQ, Versailles, France
| | - Michael A Lane
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States.,Marion Murray Spinal Cord Research Center, Drexel University College of Medicine, Philadelphia, PA, United States
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18
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Malone IG, Nosacka RL, Nash MA, Otto KJ, Dale EA. Electrical epidural stimulation of the cervical spinal cord: implications for spinal respiratory neuroplasticity after spinal cord injury. J Neurophysiol 2021; 126:607-626. [PMID: 34232771 PMCID: PMC8409953 DOI: 10.1152/jn.00625.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 06/07/2021] [Accepted: 06/27/2021] [Indexed: 01/15/2023] Open
Abstract
Traumatic cervical spinal cord injury (cSCI) can lead to damage of bulbospinal pathways to the respiratory motor nuclei and consequent life-threatening respiratory insufficiency due to respiratory muscle paralysis/paresis. Reports of electrical epidural stimulation (EES) of the lumbosacral spinal cord to enable locomotor function after SCI are encouraging, with some evidence of facilitating neural plasticity. Here, we detail the development and success of EES in recovering locomotor function, with consideration of stimulation parameters and safety measures to develop effective EES protocols. EES is just beginning to be applied in other motor, sensory, and autonomic systems; however, there has only been moderate success in preclinical studies aimed at improving breathing function after cSCI. Thus, we explore the rationale for applying EES to the cervical spinal cord, targeting the phrenic motor nucleus for the restoration of breathing. We also suggest cellular/molecular mechanisms by which EES may induce respiratory plasticity, including a brief examination of sex-related differences in these mechanisms. Finally, we suggest that more attention be paid to the effects of specific electrical parameters that have been used in the development of EES protocols and how that can impact the safety and efficacy for those receiving this therapy. Ultimately, we aim to inform readers about the potential benefits of EES in the phrenic motor system and encourage future studies in this area.
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Affiliation(s)
- Ian G Malone
- Department of Electrical and Computer Engineering, University of Florida, Gainesville, Florida
- Breathing Research and Therapeutics Center (BREATHE), University of Florida, Gainesville, Florida
| | - Rachel L Nosacka
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida
| | - Marissa A Nash
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida
| | - Kevin J Otto
- Department of Electrical and Computer Engineering, University of Florida, Gainesville, Florida
- Breathing Research and Therapeutics Center (BREATHE), University of Florida, Gainesville, Florida
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida
- Department of Neuroscience, University of Florida, Gainesville, Florida
- Department of Neurology, University of Florida, Gainesville, Florida
- Department of Materials Science and Engineering, University of Florida, Gainesville, Florida
- McKnight Brain Institute, University of Florida, Gainesville, Florida
| | - Erica A Dale
- Breathing Research and Therapeutics Center (BREATHE), University of Florida, Gainesville, Florida
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida
- Department of Neuroscience, University of Florida, Gainesville, Florida
- McKnight Brain Institute, University of Florida, Gainesville, Florida
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19
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Lee KZ, Liou LM, Vinit S. Diaphragm Motor-Evoked Potential Induced by Cervical Magnetic Stimulation following Cervical Spinal Cord Contusion in the Rat. J Neurotrauma 2021; 38:2122-2140. [PMID: 33899506 DOI: 10.1089/neu.2021.0080] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Cervical spinal injury is typically associated with respiratory impairments due to damage to bulbospinal respiratory pathways and phrenic motoneurons. Magnetic stimulation is a non-invasive approach for the evaluation and modulation of the nervous system. The present study was designed to examine whether cervical magnetic stimulation can be applied to evaluate diaphragmatic motor outputs in a pre-clinical rat model of cervical spinal injury. The bilateral diaphragm was monitored in anesthetized rats using electromyogram at the acute, subchronic, and chronic stages following left mid-cervical contusion. The center of a figure-of-eight coil was placed 20 mm caudal to bregma to stimulate the cervical spinal cord. The results demonstrated that a single magnetic stimulation can evoke significant motor-evoked potentials in the diaphragms of uninjured animals when the animal's head was placed 30 mm right or left from the center of the coil. The spontaneous bursting of the diaphragm was significantly attenuated by contusion injury at all-time-points post-injury. However, the threshold of the diaphragmatic motor-evoked potential was reduced, and the amplitude of the diaphragmatic motor-evoked potential was enhanced in response to cervical magnetic stimulation at the acute injury stage. Moreover, the motor-evoked potentials of the bilateral diaphragm in animals with contusions were generally larger when the coil was placed at the left spinal cord at the subchronic and chronic injury stages. These results suggested that cervical magnetic stimulation can be used to examine the excitability of phrenic motor outputs post-injury, and magnetic stimulation applied more laterally may be more effective for triggering diaphragmatic motor-evoked potentials.
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Affiliation(s)
- Kun-Ze Lee
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
- Department of Biomedical Science and Environmental Biology, School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Li-Min Liou
- Department of Neurology, Kaohsiung Medical University Hospital, School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
- Department of Neurology, School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Stéphane Vinit
- Université Paris-Saclay, UVSQ, Inserm, END-ICAP, Versailles, France
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20
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Cheng L, Sami A, Ghosh B, Goudsward HJ, Smith GM, Wright MC, Li S, Lepore AC. Respiratory axon regeneration in the chronically injured spinal cord. Neurobiol Dis 2021; 155:105389. [PMID: 33975016 DOI: 10.1016/j.nbd.2021.105389] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 04/19/2021] [Accepted: 05/05/2021] [Indexed: 02/01/2023] Open
Abstract
Promoting the combination of robust regeneration of damaged axons and synaptic reconnection of these growing axon populations with appropriate neuronal targets represents a major therapeutic goal following spinal cord injury (SCI). A key impediment to achieving this important aim includes an intrinsic inability of neurons to extend axons in adult CNS, particularly in the context of the chronically-injured spinal cord. We tested whether an inhibitory peptide directed against phosphatase and tensin homolog (PTEN: a central inhibitor of neuron-intrinsic axon growth potential) could restore inspiratory diaphragm function by reconnecting critical respiratory neural circuitry in a rat model of chronic cervical level 2 (C2) hemisection SCI. We found that systemic delivery of PTEN antagonist peptide 4 (PAP4) starting at 8 weeks after C2 hemisection promoted substantial, long-distance regeneration of injured bulbospinal rostral Ventral Respiratory Group (rVRG) axons into and through the lesion and back toward phrenic motor neurons (PhMNs) located in intact caudal C3-C5 spinal cord. Despite this robust rVRG axon regeneration, PAP4 stimulated only minimal recovery of diaphragm function. Furthermore, re-lesion through the hemisection site completely removed PAP4-induced functional improvement, demonstrating that axon regeneration through the lesion was responsible for this partial functional recovery. Interestingly, there was minimal formation of putative excitatory monosynaptic connections between regrowing rVRG axons and PhMN targets, suggesting that (1) limited rVRG-PhMN synaptic reconnectivity was responsible at least in part for the lack of a significant functional effect, (2) chronically-injured spinal cord presents an obstacle to achieving synaptogenesis between regenerating axons and post-synaptic targets, and (3) addressing this challenge is a potentially-powerful strategy to enhance therapeutic efficacy in the chronic SCI setting. In conclusion, our study demonstrates a non-invasive and transient pharmacological approach in chronic SCI to repair the critically-important neural circuitry controlling diaphragmatic respiratory function, but also sheds light on obstacles to circuit plasticity presented by the chronically-injured spinal cord.
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Affiliation(s)
- Lan Cheng
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Armin Sami
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Biswarup Ghosh
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Hannah J Goudsward
- Department of Biology, Arcadia University, 450 S. Easton Rd., 220 Boyer Hall, Glenside, PA 19038, USA
| | - George M Smith
- Department of Neuroscience, Shriners Hospitals for Pediatric Research Center, Temple University School of Medicine, 3500 North Broad Street, Philadelphia, PA 19140-5104, USA
| | - Megan C Wright
- Department of Biology, Arcadia University, 450 S. Easton Rd., 220 Boyer Hall, Glenside, PA 19038, USA
| | - Shuxin Li
- Department of Neuroscience, Shriners Hospitals for Pediatric Research Center, Temple University School of Medicine, 3500 North Broad Street, Philadelphia, PA 19140-5104, USA
| | - Angelo C Lepore
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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21
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Gonzalez-Rothi EJ, Lee KZ. Intermittent hypoxia and respiratory recovery in pre-clinical rodent models of incomplete cervical spinal cord injury. Exp Neurol 2021; 342:113751. [PMID: 33974878 DOI: 10.1016/j.expneurol.2021.113751] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 04/24/2021] [Accepted: 05/06/2021] [Indexed: 10/21/2022]
Abstract
Impaired respiratory function is a common and devastating consequence of cervical spinal cord injury. Accordingly, the development of safe and effective treatments to restore breathing function is critical. Acute intermittent hypoxia has emerged as a promising therapeutic strategy to treat respiratory insufficiency in individuals with spinal cord injury. Since the original report by Bach and Mitchell (1996) concerning long-term facilitation of phrenic motor output elicited by brief, episodic exposure to reduced oxygen, a series of studies in animal models have led to the realization that acute intermittent hypoxia may have tremendous potential for inducing neuroplasticity and functional recovery in the injured spinal cord. Advances in our understanding of the neurobiology of acute intermittent hypoxia have prompted us to begin to explore its effects in human clinical studies. Here, we review the basic neurobiology of the control of breathing and the pathophysiology and respiratory consequences of two common experimental models of incomplete cervical spinal cord injury (i.e., high cervical hemisection and mid-cervical contusion). We then discuss the impact of acute intermittent hypoxia on respiratory motor function in these models: work that has laid the foundation for translation of this promising therapeutic strategy to clinical populations. Lastly, we examine the limitations of these animal models and intermittent hypoxia and discuss how future work in animal models may further advance the translation and therapeutic efficacy of this treatment.
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Affiliation(s)
- Elisa J Gonzalez-Rothi
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Kun-Ze Lee
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan; Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung, Taiwan.
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22
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Teng YD, Zafonte RD. Prelude to the special issue on novel neurocircuit, cellular and molecular targets for developing functional rehabilitation therapies of neurotrauma. Exp Neurol 2021; 341:113689. [PMID: 33745921 DOI: 10.1016/j.expneurol.2021.113689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 03/07/2021] [Indexed: 11/15/2022]
Abstract
The poor endogenous recovery capacity and other impediments to reinstating sensorimotor or autonomic function after adult neurotrauma have perplexed modern neuroscientists, bioengineers, and physicians for over a century. However, despite limited improvement in options to mitigate acute pathophysiological sequalae, the past 20 years have witnessed marked progresses in developing efficacious rehabilitation strategies for chronic spinal cord and brain injuries. The achievement is mainly attributable to research advancements in elucidating neuroplastic mechanisms for the potential to enhance clinical prognosis. Innovative cross-disciplinary studies have established novel therapeutic targets, theoretical frameworks, and regiments to attain treatment efficacy. This Special Issue contained eight papers that described experimental and human data along with literature reviews regarding the essential roles of the conventionally undervalued factors in neural repair: systemic inflammation, neural-respiratory inflammasome axis, modulation of glutamatergic and monoaminergic neurotransmission, neurogenesis, nerve transfer, recovery neurobiology components, and the spinal cord learning, respiration and central pattern generator neurocircuits. The focus of this work was on how to induce functional recovery from manipulating these underpinnings through their interactions with secondary injury events, peripheral and supraspinal inputs, neuromusculoskeletal network, and interventions (i.e., activity training, pharmacological adjuncts, electrical stimulation, and multimodal neuromechanical, brain-computer interface [BCI] and robotic assistance [RA] devices). The evidence suggested that if key neurocircuits are therapeutically reactivated, rebuilt, and/or modulated under proper sensory feedback, neurological function (e.g., cognition, respiration, limb movement, locomotion, etc.) will likely be reanimated after neurotrauma. The efficacy can be optimized by individualizing multimodal rehabilitation treatments via BCI/RA-integrated drug administration and neuromechanical protheses.
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Affiliation(s)
- Yang D Teng
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA, USA; Neurotrauma Recovery Research, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital Network, Mass General Brigham, and Harvard Medical School, Boston, MA, USA; Spaulding Research Institute, Spaulding Rehabilitation Hospital Network, Boston, MA, USA.
| | - Ross D Zafonte
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA, USA; Neurotrauma Recovery Research, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital Network, Mass General Brigham, and Harvard Medical School, Boston, MA, USA; Spaulding Research Institute, Spaulding Rehabilitation Hospital Network, Boston, MA, USA.
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23
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Wollman LB, Streeter KA, Fusco AF, Gonzalez-Rothi EJ, Sandhu MS, Greer JJ, Fuller DD. Ampakines stimulate phrenic motor output after cervical spinal cord injury. Exp Neurol 2020; 334:113465. [PMID: 32949571 DOI: 10.1016/j.expneurol.2020.113465] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Revised: 08/31/2020] [Accepted: 09/14/2020] [Indexed: 12/21/2022]
Abstract
Activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors increases phrenic motor output. Ampakines are a class of drugs that are positive allosteric modulators of AMPA receptors. We hypothesized that 1) ampakines can stimulate phrenic activity after incomplete cervical spinal cord injury (SCI), and 2) pairing ampakines with brief hypoxia could enable sustained facilitation of phrenic bursting. Phrenic activity was recorded ipsilateral (IL) and contralateral (CL) to C2 spinal cord hemisection (C2Hx) in anesthetized adult rats. Two weeks after C2Hx, ampakine CX717 (15 mg/kg, i.v.) increased IL (61 ± 46% baseline, BL) and CL burst amplitude (47 ± 26%BL) in 8 of 8 rats. After 90 min, IL and CL bursting remained above baseline (BL) in 7 of 8 rats. Pairing ampakine with a single bout of acute hypoxia (5-min, arterial partial pressure of O2 ~ 50 mmHg) had a variable impact on phrenic bursting, with some rats showing a large facilitation that exceeded the response of the ampakine alone group. At 8 weeks post-C2Hx, 7 of 8 rats increased IL (115 ± 117%BL) and CL burst amplitude (45 ± 27%BL) after ampakine. The IL burst amplitude remained above BL for 90-min in 7 of 8 rats; CL bursting remained elevated in 6 of 8 rats. The sustained impact of ampakine at 8 weeks was not enhanced by hypoxia exposure. Intravenous vehicle (10% 2-Hydroxypropyl-β-cyclodextrin) did not increase phrenic bursting at either time point. We conclude that ampakines effectively stimulate neural drive to the diaphragm after cervical SCI. Pairing ampakines with a single hypoxic exposure did not consistently enhance phrenic motor facilitation.
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Affiliation(s)
- L B Wollman
- Department of Physical Therapy, University of Florida, Gainesville, FL 32610, United States of America; Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL 32610, United States of America
| | - K A Streeter
- Department of Physical Therapy, University of Florida, Gainesville, FL 32610, United States of America; Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL 32610, United States of America
| | - A F Fusco
- Department of Physical Therapy, University of Florida, Gainesville, FL 32610, United States of America
| | - E J Gonzalez-Rothi
- Department of Physical Therapy, University of Florida, Gainesville, FL 32610, United States of America; McKnight Brain Institute, University of Florida, Gainesville, Florida 32610, United States of America; Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL 32610, United States of America
| | - M S Sandhu
- Department of Physical Therapy, University of Florida, Gainesville, FL 32610, United States of America
| | - J J Greer
- Department of Physiology, University of Alberta, Edmonton, AB T6G2SE, Canada
| | - D D Fuller
- Department of Physical Therapy, University of Florida, Gainesville, FL 32610, United States of America; McKnight Brain Institute, University of Florida, Gainesville, Florida 32610, United States of America; Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL 32610, United States of America.
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24
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Ding SQ, Chen YQ, Chen J, Wang SN, Duan FX, Shi YJ, Hu JG, Lü HZ. Serum exosomal microRNA transcriptome profiling in subacute spinal cord injured rats. Genomics 2020; 112:5086-5100. [PMID: 32919018 DOI: 10.1016/j.ygeno.2019.09.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Revised: 08/27/2019] [Accepted: 09/23/2019] [Indexed: 12/11/2022]
Abstract
MicroRNAs (miRNAs) are involved in a series of pathology of spinal cord injury (SCI). Although, locally expressed miRNAs have advantages in studying the pathological mechanism, they cannot be used as biomarkers. The "free circulation" miRNAs can be used as biomarkers, but they have low concentration and poor stability in body fluids. Exosomal miRNAs in body fluids have many advantages comparing with free miRNAs. Therefore, we hypothesized that the specific miRNAs in the central nervous system might be transported to the peripheral circulation and concentrated in exosomes after injury. Using next-generation sequencing, miRNA profiles in serum exosomes of sham and subactue SCI rats were analyzed. The results showed that SCI can lead to changes of serum exosomal miRNAs. These changed miRNAs and their associated signaling pathways may explain the pathological mechanism of suacute SCI. More importantly, we found some valuable serum exosomal miRNAs for diagnosis and prognosis of SCI.
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Affiliation(s)
- Shu-Qin Ding
- Clinical Laboratory, The First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Anhui Key Laboratory of Tissue Transplantation, The First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China
| | - Yu-Qing Chen
- Clinical Laboratory, The First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Anhui Key Laboratory of Tissue Transplantation, The First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Department of Immunology, Bengbu Medical College, Anhui 233030, PR China
| | - Jing Chen
- Clinical Laboratory, The First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Anhui Key Laboratory of Tissue Transplantation, The First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Department of Immunology, Bengbu Medical College, Anhui 233030, PR China
| | - Sai-Nan Wang
- Clinical Laboratory, The First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Anhui Key Laboratory of Tissue Transplantation, The First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Department of Immunology, Bengbu Medical College, Anhui 233030, PR China
| | - Fei-Xiang Duan
- Clinical Laboratory, The First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Anhui Key Laboratory of Tissue Transplantation, The First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China
| | - Yu-Jiao Shi
- Clinical Laboratory, The First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Anhui Key Laboratory of Tissue Transplantation, The First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China
| | - Jian-Guo Hu
- Clinical Laboratory, The First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Anhui Key Laboratory of Tissue Transplantation, The First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China.
| | - He-Zuo Lü
- Clinical Laboratory, The First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Anhui Key Laboratory of Tissue Transplantation, The First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Department of Immunology, Bengbu Medical College, Anhui 233030, PR China.
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25
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Moradi K, Golbakhsh M, Haghighi F, Afshari K, Nikbakhsh R, Khavandi MM, Faghani S, Badripour A, Etemadi A, Ashraf-Ganjouei A, Bagheri S, Dehpour AR. Inhibition of phosphodiesterase IV enzyme improves locomotor and sensory complications of spinal cord injury via altering microglial activity: Introduction of Roflumilast as an alternative therapy. Int Immunopharmacol 2020; 86:106743. [PMID: 32619958 DOI: 10.1016/j.intimp.2020.106743] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 06/06/2020] [Accepted: 06/23/2020] [Indexed: 02/02/2023]
Abstract
Despite the great search for an effective approach to minimize secondary injury in spinal cord injury (SCI) setting, there have been limited advances. Roflumilast is a selective inhibitor of phosphodiesterase 4 with potent anti-inflammatory properties. Here, we sought to explore Roflumilast efficacy in the improvement of locomotor and sensory deficits of SCI. In an animal setting, 50 male rats were randomly assigned to five groups: an SCI group receiving Placebo, three SCI groups receiving Roflumilast at the doses of 0.25, 0.5, and 1 mg/kg prior to T9 vertebra laminectomy, and a sham-operated group. Locomotor, mechanical, and thermal activities were evaluated for 28 days. At the end of the study, spinal cord samples were taken to assess the relative ratio of microglial subtypes, including M1 and M2, histopathological changes, levels of pro-inflammatory (TNF-α and IL-1β) and anti-inflammatory (IL-10) biomarkers, and cAMP level. Repeated measure analysis revealed significant effect for time-treatment interaction on locomotion [F (24, 270) = 280.7, p < 0.001], thermal sensitivity [F (16, 180) = 4.35, p < 0.001], and mechanical sensitivity [F (16, 180) = 7.96, p < 0.001]. As expected, Roflumilast significantly increased the expression of spinal cAMP. H&E staining exhibited lesser histopathological disruptions in Roflumilast-treated rodents. We also observed a significant reduction in the M1/M2 ratio (p values < 0.001) as well as in pro-inflammatory biomarkers following the administration of Roflumilast to the injured rats. Furthermore, IL-10 level was increased in rodents receiving 1 mg/kg of the reagent. In conclusion, the increased spinal cAMP following Roflumilast therapy might attenuate neuroinflammation via altering microglial activity; therefore, it could be considered as an alternative therapeutic agent for SCI complications.
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Affiliation(s)
- Kamyar Moradi
- Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Brain and Spinal Cord Injury Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Mohammadreza Golbakhsh
- Department of Orthopedic Surgery, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran
| | - Farinaz Haghighi
- Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Khashayar Afshari
- Brain and Spinal Cord Injury Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Rajan Nikbakhsh
- Brain and Spinal Cord Injury Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran; Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mohammad Mahdi Khavandi
- Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Shahriar Faghani
- Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Abolfazl Badripour
- Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Brain and Spinal Cord Injury Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Ali Etemadi
- Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Amir Ashraf-Ganjouei
- Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Brain and Spinal Cord Injury Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Sayna Bagheri
- Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Brain and Spinal Cord Injury Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Ahmad Reza Dehpour
- Brain and Spinal Cord Injury Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran; Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
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26
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Ding SQ, Chen YQ, Chen J, Wang SN, Duan FX, Shi YJ, Hu JG, Lü HZ. Serum exosomal microRNA transcriptome profiling in subacute spinal cord injured rats. Genomics 2019; 112:2092-2105. [PMID: 31830526 DOI: 10.1016/j.ygeno.2019.12.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
MicroRNAs (miRNAs) are involved in a series of pathology of spinal cord injury (SCI). Although, locally expressed miRNAs have advantages in studying the pathological mechanism, they cannot be used as biomarkers. The "free circulation" miRNAs can be used as biomarkers, but they have low concentration and poor stability in body fluids. Exosomal miRNAs in body fluids have many advantages comparing with free miRNAs. Therefore, we hypothesized that the specific miRNAs in the central nervous system might be transported to the peripheral circulation and concentrated in exosomes after injury. Using next-generation sequencing, miRNA profiles in serum exosomes of sham and subactue SCI rats were analyzed. The results showed that SCI can lead to changes of serum exosomal miRNAs. These changed miRNAs and their associated signaling pathways may explain the pathological mechanism of suacute SCI. More importantly, we found some valuable serum exosomal miRNAs for diagnosis and prognosis of SCI.
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Affiliation(s)
- Shu-Qin Ding
- Clinical Laboratory, the First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Anhui Key Laboratory of Tissue Transplantation, the First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China
| | - Yu-Qing Chen
- Clinical Laboratory, the First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Anhui Key Laboratory of Tissue Transplantation, the First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Department of Immunology, Bengbu Medical College, Anhui 233030, PR China
| | - Jing Chen
- Clinical Laboratory, the First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Anhui Key Laboratory of Tissue Transplantation, the First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Department of Immunology, Bengbu Medical College, Anhui 233030, PR China
| | - Sai-Nan Wang
- Clinical Laboratory, the First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Anhui Key Laboratory of Tissue Transplantation, the First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Department of Immunology, Bengbu Medical College, Anhui 233030, PR China
| | - Fei-Xiang Duan
- Clinical Laboratory, the First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Anhui Key Laboratory of Tissue Transplantation, the First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China
| | - Yu-Jiao Shi
- Clinical Laboratory, the First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Anhui Key Laboratory of Tissue Transplantation, the First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China
| | - Jian-Guo Hu
- Clinical Laboratory, the First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Anhui Key Laboratory of Tissue Transplantation, the First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China.
| | - He-Zuo Lü
- Clinical Laboratory, the First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Anhui Key Laboratory of Tissue Transplantation, the First Affiliated Hospital of Bengbu Medical College, Anhui 233004, PR China; Department of Immunology, Bengbu Medical College, Anhui 233030, PR China.
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27
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Streeter KA, Sunshine MD, Patel SR, Gonzalez-Rothi EJ, Reier PJ, Baekey DM, Fuller DD. Mid-cervical interneuron networks following high cervical spinal cord injury. Respir Physiol Neurobiol 2019; 271:103305. [PMID: 31553921 DOI: 10.1016/j.resp.2019.103305] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 08/22/2019] [Accepted: 09/20/2019] [Indexed: 12/15/2022]
Abstract
Spinal interneuron (IN) networks can facilitate respiratory motor recovery after spinal cord injury (SCI). We hypothesized that excitatory synaptic connectivity between INs located immediately caudal to unilateral cervical SCI would be most prevalent in a contra- to ipsilateral direction. Adult rats were studied following chronic C2 spinal cord hemisection (C2Hx) injury. Rats were anesthetized and ventilated and a multi-electrode array was used to simultaneously record INs on both sides of the C4-5 spinal cord. The temporal firing relationship between IN pairs was evaluated using cross-correlation with directionality of synaptic connections inferred based on electrode location. During baseline recordings, the majority of detectable excitatory IN connections occurred in a contra- to- ipsilateral direction. However, acute respiratory stimulation with hypoxia abolished this directionality, while simultaneously increasing the detectable inhibitory connections within the ipsilateral cord. We conclude that propriospinal networks caudal to SCI can display a contralateral-to-ipsilateral directionality of synaptic connections and that these connections are modulated by acute exposure to hypoxia.
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Affiliation(s)
- K A Streeter
- Department of Physical Therapy, University of Florida, Gainesville, FL 32610, United States; McKnight Brain Institute, University of Florida, Gainesville, FL 32601, United States; Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL 32610, United States
| | - M D Sunshine
- Department of Physical Therapy, University of Florida, Gainesville, FL 32610, United States; Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL 32610, United States
| | - S R Patel
- Department of Physical Therapy, University of Florida, Gainesville, FL 32610, United States
| | - E J Gonzalez-Rothi
- Department of Physical Therapy, University of Florida, Gainesville, FL 32610, United States; McKnight Brain Institute, University of Florida, Gainesville, FL 32601, United States; Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL 32610, United States
| | - P J Reier
- Department of Neuroscience, University of Florida, Gainesville, FL, 32610, United States; McKnight Brain Institute, University of Florida, Gainesville, FL 32601, United States
| | - D M Baekey
- Department of Physiological Sciences, University of Florida, Gainesville, FL 32610, United States; Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL 32610, United States
| | - D D Fuller
- Department of Physical Therapy, University of Florida, Gainesville, FL 32610, United States; McKnight Brain Institute, University of Florida, Gainesville, FL 32601, United States; Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL 32610, United States.
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28
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Seven YB, Mitchell GS. Mechanisms of compensatory plasticity for respiratory motor neuron death. Respir Physiol Neurobiol 2019; 265:32-39. [PMID: 30625378 DOI: 10.1016/j.resp.2019.01.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 12/22/2018] [Accepted: 01/03/2019] [Indexed: 02/06/2023]
Abstract
Respiratory motor neuron death arises from multiple neurodegenerative and traumatic neuromuscular disorders. Despite motor neuron death, compensatory mechanisms minimize its functional impact by harnessing intrinsic mechanisms of compensatory respiratory plasticity. However, the capacity for compensation eventually reaches limits and pathology ensues. Initially, challenges to the system such as increased metabolic demand reveal sub-clinical pathology. With greater motor neuron loss, the eventual result is de-compensation, ventilatory failure, ventilator dependence and then death. In this brief review, we discuss recent advances in our understanding of mechanisms giving rise to compensatory respiratory plasticity in response to respiratory motor neuron death including: 1) increased central respiratory drive, 2) plasticity in synapses on spared phrenic motor neurons, 3) enhanced neuromuscular transmission and 4) shifts in respiratory muscle utilization from more affected to less affected motor pools. Some of these compensatory mechanisms may prolong breathing function, but hasten the demise of surviving motor neurons. Improved understanding of these mechanisms and their impact on survival of spared motor neurons will guide future efforts to develop therapeutic interventions that preserve respiratory function with neuromuscular injury/disease.
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Affiliation(s)
- Yasin B Seven
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, 32610, USA
| | - Gordon S Mitchell
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, 32610, USA.
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29
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Satkunendrarajah K, Karadimas SK, Laliberte AM, Montandon G, Fehlings MG. Cervical excitatory neurons sustain breathing after spinal cord injury. Nature 2018; 562:419-422. [DOI: 10.1038/s41586-018-0595-z] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 08/14/2018] [Indexed: 11/09/2022]
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30
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The Neuroplastic and Therapeutic Potential of Spinal Interneurons in the Injured Spinal Cord. Trends Neurosci 2018; 41:625-639. [PMID: 30017476 DOI: 10.1016/j.tins.2018.06.004] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 06/06/2018] [Accepted: 06/12/2018] [Indexed: 12/25/2022]
Abstract
The central nervous system is not a static, hard-wired organ. Examples of neuroplasticity, whether at the level of the synapse, the cell, or within and between circuits, can be found during development, throughout the progression of disease, or after injury. One essential component of the molecular, anatomical, and functional changes associated with neuroplasticity is the spinal interneuron (SpIN). Here, we draw on recent multidisciplinary studies to identify and interrogate subsets of SpINs and their roles in locomotor and respiratory circuits. We highlight some of the recent progress that elucidates the importance of SpINs in circuits affected by spinal cord injury (SCI), especially those within respiratory networks; we also discuss potential ways that spinal neuroplasticity can be therapeutically harnessed for recovery.
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31
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Bezdudnaya T, Hormigo KM, Marchenko V, Lane MA. Spontaneous respiratory plasticity following unilateral high cervical spinal cord injury in behaving rats. Exp Neurol 2018; 305:56-65. [PMID: 29596845 DOI: 10.1016/j.expneurol.2018.03.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 01/23/2018] [Accepted: 03/23/2018] [Indexed: 01/25/2023]
Abstract
Unilateral cervical C2 hemisection (C2Hx) is a classic model of spinal cord injury (SCI) for studying respiratory dysfunction and plasticity. However, most previous studies were performed under anesthesia, which significantly alters respiratory network. Therefore, the goal of this work was to assess spontaneous diaphragm recovery post-C2Hx in awake, freely behaving animals. Adult rats were chronically implanted with diaphragm EMG electrodes and recorded during 8 weeks post-C2Hx. Our results reveal that ipsilateral diaphragm activity partially recovers within days post-injury and reaches pre-injury amplitude in a few weeks. However, the full extent of spontaneous ipsilateral recovery is significantly attenuated by anesthesia (ketamine/xylazine, isoflurane, and urethane). This suggests that the observed recovery may be attributed in part to activation of NMDA receptors which are suppressed by anesthesia. Despite spontaneous recovery in awake animals, ipsilateral hemidiaphragm dysfunction still persists: i) Inspiratory bursts during basal (slow) breathing exhibit an altered pattern, ii) the amplitude of sighs - or augmented breaths - is significantly decreased, and iii) the injured hemidiaphragm exhibits spontaneous events of hyperexcitation. The results from this study offer an under-appreciated insight into spontaneous diaphragm activity and recovery following high cervical spinal cord injury in awake animals.
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Affiliation(s)
- Tatiana Bezdudnaya
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA 19129, USA.
| | - Kristiina M Hormigo
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA 19129, USA
| | - Vitaliy Marchenko
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA 19129, USA
| | - Michael A Lane
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA 19129, USA
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Urban MW, Ghosh B, Strojny LR, Block CG, Blazejewski SM, Wright MC, Smith GM, Lepore AC. Cell-type specific expression of constitutively-active Rheb promotes regeneration of bulbospinal respiratory axons following cervical SCI. Exp Neurol 2018; 303:108-119. [PMID: 29453976 DOI: 10.1016/j.expneurol.2018.02.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 02/09/2018] [Accepted: 02/12/2018] [Indexed: 12/27/2022]
Abstract
Damage to respiratory neural circuitry and consequent loss of diaphragm function is a major cause of morbidity and mortality in individuals suffering from traumatic cervical spinal cord injury (SCI). Repair of CNS axons after SCI remains a therapeutic challenge, despite current efforts. SCI disrupts inspiratory signals originating in the rostral ventral respiratory group (rVRG) of the medulla from their phrenic motor neuron (PhMN) targets, resulting in loss of diaphragm function. Using a rat model of cervical hemisection SCI, we aimed to restore rVRG-PhMN-diaphragm circuitry by stimulating regeneration of injured rVRG axons via targeted induction of Rheb (ras homolog enriched in brain), a signaling molecule that regulates neuronal-intrinsic axon growth potential. Following C2 hemisection, we performed intra-rVRG injection of an adeno-associated virus serotype-2 (AAV2) vector that drives expression of a constitutively-active form of Rheb (cRheb). rVRG neuron-specific cRheb expression robustly increased mTOR pathway activity within the transduced rVRG neuron population ipsilateral to the hemisection, as assessed by levels of phosphorylated ribosomal S6 kinase. By co-injecting our novel AAV2-mCherry/WGA anterograde/trans-synaptic axonal tracer into rVRG, we found that cRheb expression promoted regeneration of injured rVRG axons into the lesion site, while we observed no rVRG axon regrowth with AAV2-GFP control. AAV2-cRheb also significantly reduced rVRG axonal dieback within the intact spinal cord rostral to the lesion. However, cRheb expression did not promote any recovery of ipsilateral hemi-diaphragm function, as assessed by inspiratory electromyography (EMG) burst amplitudes. This lack of functional recovery was likely because regrowing rVRG fibers did not extend back into the caudal spinal cord to synaptically reinnervate PhMNs that we retrogradely-labeled with cholera toxin B from the ipsilateral hemi-diaphragm. Our findings demonstrate that enhancing neuronal-intrinsic axon growth capacity can promote regeneration of injured bulbospinal respiratory axons after SCI, but this strategy may need to be combined with other manipulations to achieve reconnection of damaged neural circuitry and ultimately recovery of diaphragm function.
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Affiliation(s)
- Mark W Urban
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, 233 South 10th Street, BLSB 245, Philadelphia, PA 19107, United States.
| | - Biswarup Ghosh
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, 233 South 10th Street, BLSB 245, Philadelphia, PA 19107, United States.
| | - Laura R Strojny
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, 233 South 10th Street, BLSB 245, Philadelphia, PA 19107, United States
| | - Cole G Block
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, 233 South 10th Street, BLSB 245, Philadelphia, PA 19107, United States
| | - Sara M Blazejewski
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, 233 South 10th Street, BLSB 245, Philadelphia, PA 19107, United States.
| | - Megan C Wright
- Department of Biology, Arcadia University, 450 S. Easton Rd., 220 Boyer Hall, Glenside, PA 19038, United States.
| | - George M Smith
- Department of Neuroscience, Shriners Hospitals for Pediatric Research Center, Temple University School of Medicine, 3500 North Broad Street, Philadelphia, PA 19140-5104, United States.
| | - Angelo C Lepore
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College, Thomas Jefferson University, 233 South 10th Street, BLSB 245, Philadelphia, PA 19107, United States.
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Bezdudnaya T, Marchenko V, Zholudeva LV, Spruance VM, Lane MA. Supraspinal respiratory plasticity following acute cervical spinal cord injury. Exp Neurol 2017; 293:181-189. [PMID: 28433644 PMCID: PMC5510885 DOI: 10.1016/j.expneurol.2017.04.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 04/06/2017] [Accepted: 04/10/2017] [Indexed: 12/20/2022]
Abstract
Impaired breathing is a devastating result of high cervical spinal cord injuries (SCI) due to partial or full denervation of phrenic motoneurons, which innervate the diaphragm - a primary muscle of respiration. Consequently, people with cervical level injuries often become dependent on assisted ventilation and are susceptible to secondary complications. However, there is mounting evidence for limited spontaneous recovery of respiratory function following injury, demonstrating the neuroplastic potential of respiratory networks. Although many studies have shown such plasticity at the level of the spinal cord, much less is known about the changes occurring at supraspinal levels post-SCI. The goal of this study was to determine functional reorganization of respiratory neurons in the medulla acutely (>4h) following high cervical SCI. Experiments were conducted in decerebrate, unanesthetized, vagus intact and artificially ventilated rats. In this preparation, spontaneous recovery of ipsilateral phrenic nerve activity was observed within 4 to 6h following an incomplete, C2 hemisection (C2Hx). Electrophysiological mapping of the ventrolateral medulla showed a reorganization of inspiratory and expiratory sites ipsilateral to injury. These changes included i) decreased respiratory activity within the caudal ventral respiratory group (cVRG; location of bulbospinal expiratory neurons); ii) increased proportion of expiratory phase activity within the rostral ventral respiratory group (rVRG; location of inspiratory bulbo-spinal neurons); iii) increased respiratory activity within ventral reticular nuclei, including lateral reticular (LRN) and paragigantocellular (LPGi) nuclei. We conclude that disruption of descending and ascending connections between the medulla and spinal cord leads to immediate functional reorganization within the supraspinal respiratory network, including neurons within the ventral respiratory column and adjacent reticular nuclei.
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Affiliation(s)
- Tatiana Bezdudnaya
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA 19129, USA
| | - Vitaliy Marchenko
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA 19129, USA
| | - Lyandysha V Zholudeva
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA 19129, USA
| | - Victoria M Spruance
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA 19129, USA
| | - Michael A Lane
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA 19129, USA.
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Zholudeva LV, Karliner JS, Dougherty KJ, Lane MA. Anatomical Recruitment of Spinal V2a Interneurons into Phrenic Motor Circuitry after High Cervical Spinal Cord Injury. J Neurotrauma 2017; 34:3058-3065. [PMID: 28548606 DOI: 10.1089/neu.2017.5045] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
More than half of all spinal cord injuries (SCIs) occur at the cervical level, often resulting in impaired respiration. Despite this devastating outcome, there is substantial evidence for endogenous neuroplasticity after cervical SCI. Spinal interneurons are widely recognized as being an essential anatomical component of this plasticity by contributing to novel neuronal pathways that can result in functional improvement. The identity of spinal interneurons involved with respiratory plasticity post-SCI, however, has remained largely unknown. Using a transgenic Chx10-eGFP mouse line (Strain 011391-UCD), the present study is the first to demonstrate the recruitment of excitatory interneurons into injured phrenic circuitry after a high cervical SCI. Diaphragm electromyography and anatomical analysis were used to confirm lesion-induced functional deficits and document extent of the lesion, respectively. Transneuronal tracing with pseudorabies virus (PRV) was used to identify interneurons within the phrenic circuitry. There was a robust increase in the number of PRV-labeled V2a interneurons ipsilateral to the C2 hemisection, demonstrating that significant numbers of these excitatory spinal interneurons were anatomically recruited into the phrenic motor pathway two weeks after injury, a time known to correspond with functional phrenic plasticity. Understanding this anatomical spinal plasticity and the neural substrates associated with functional compensation or recovery post-SCI in a controlled, experimental setting may help shed light onto possible cellular therapeutic candidates that can be targeted to enhance spontaneous recovery.
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Affiliation(s)
- Lyandysha V Zholudeva
- 1 Department of Neurobiology and Anatomy, College of Medicine, Drexel University , Philadelphia, Pennsylvania.,2 The Spinal Cord Research Center, College of Medicine, Drexel University , Philadelphia, Pennsylvania
| | - Jordyn S Karliner
- 1 Department of Neurobiology and Anatomy, College of Medicine, Drexel University , Philadelphia, Pennsylvania.,2 The Spinal Cord Research Center, College of Medicine, Drexel University , Philadelphia, Pennsylvania.,3 Department of Neuroscience, Ursinus College , Collegeville, Pennsylvania
| | - Kimberly J Dougherty
- 1 Department of Neurobiology and Anatomy, College of Medicine, Drexel University , Philadelphia, Pennsylvania.,2 The Spinal Cord Research Center, College of Medicine, Drexel University , Philadelphia, Pennsylvania
| | - Michael A Lane
- 1 Department of Neurobiology and Anatomy, College of Medicine, Drexel University , Philadelphia, Pennsylvania.,2 The Spinal Cord Research Center, College of Medicine, Drexel University , Philadelphia, Pennsylvania
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Gonzalez-Rothi EJ, Streeter KA, Hanna MH, Stamas AC, Reier PJ, Baekey DM, Fuller DD. High-frequency epidural stimulation across the respiratory cycle evokes phrenic short-term potentiation after incomplete cervical spinal cord injury. J Neurophysiol 2017; 118:2344-2357. [PMID: 28615341 DOI: 10.1152/jn.00913.2016] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 06/13/2017] [Accepted: 06/14/2017] [Indexed: 01/15/2023] Open
Abstract
C2 spinal hemilesion (C2Hx) paralyzes the ipsilateral diaphragm, but recovery is possible through activation of "crossed spinal" synaptic inputs to ipsilateral phrenic motoneurons. We tested the hypothesis that high-frequency epidural stimulation (HF-ES) would potentiate ipsilateral phrenic output after subacute and chronic C2Hx. HF-ES (300 Hz) was applied to the ventrolateral C4 or T2 spinal cord ipsilateral to C2Hx in anesthetized and mechanically ventilated adult rats. Stimulus duration was 60 s, and currents ranged from 100 to 1,000 µA. Bilateral phrenic nerve activity and ipsilateral hypoglossal (XII) nerve activity were recorded before and after HF-ES. Higher T2 stimulus currents potentiated ipsilateral phasic inspiratory activity at both 2 and 12 wk post-C2Hx, whereas higher stimulus currents delivered at C4 potentiated ipsilateral phasic phrenic activity only at 12 wk (P = 0.028). Meanwhile, tonic output in the ipsilateral phrenic nerve reached 500% of baseline values at the high currents with no difference between 2 and 12 wk. HF-ES did not trigger inspiratory burst-frequency changes. Similar responses occurred following T2 HF-ES. Increases in contralateral phrenic and XII nerve output were induced by C4 and T2 HF-ES at higher currents, but the relative magnitude of these changes was small compared with the ipsilateral phrenic response. We conclude that following incomplete cervical spinal cord injury, HF-ES of the ventrolateral midcervical or thoracic spinal cord can potentiate efferent phrenic motor output with little impact on inspiratory burst frequency. However, the substantial increases in tonic output indicate that the uninterrupted 60-s stimulation paradigm used is unlikely to be useful for respiratory muscle activation after spinal injury.NEW & NOTEWORTHY Previous studies reported that high-frequency epidural stimulation (HF-ES) activates the diaphragm following acute spinal transection. This study examined HF-ES and phrenic motor output following subacute and chronic incomplete cervical spinal cord injury. Short-term potentiation of phrenic bursting following HF-ES illustrates the potential for spinal stimulation to induce respiratory neuroplasticity. Increased tonic phrenic output indicates that alternatives to the continuous stimulation paradigm used in this study will be required for respiratory muscle activation after spinal cord injury.
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Affiliation(s)
- Elisa J Gonzalez-Rothi
- McKnight Brain Institute, Department of Physical Therapy, College of Public Health and Health Professions, University of Florida, Gainesville, Florida;
| | - Kristi A Streeter
- McKnight Brain Institute, Department of Physical Therapy, College of Public Health and Health Professions, University of Florida, Gainesville, Florida
| | - Marie H Hanna
- McKnight Brain Institute, Department of Physical Therapy, College of Public Health and Health Professions, University of Florida, Gainesville, Florida
| | - Anna C Stamas
- McKnight Brain Institute, Department of Physical Therapy, College of Public Health and Health Professions, University of Florida, Gainesville, Florida
| | - Paul J Reier
- Department of Neuroscience, College of Medicine, University of Florida, Gainesville, Florida; and
| | - David M Baekey
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida
| | - David D Fuller
- McKnight Brain Institute, Department of Physical Therapy, College of Public Health and Health Professions, University of Florida, Gainesville, Florida
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Vagal Control of Breathing Pattern after Midcervical Contusion in Rats. J Neurotrauma 2017; 34:734-745. [DOI: 10.1089/neu.2016.4645] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
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Hormigo KM, Zholudeva LV, Spruance VM, Marchenko V, Cote MP, Vinit S, Giszter S, Bezdudnaya T, Lane MA. Enhancing neural activity to drive respiratory plasticity following cervical spinal cord injury. Exp Neurol 2017; 287:276-287. [PMID: 27582085 PMCID: PMC5121051 DOI: 10.1016/j.expneurol.2016.08.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 07/20/2016] [Accepted: 08/26/2016] [Indexed: 02/07/2023]
Abstract
Cervical spinal cord injury (SCI) results in permanent life-altering sensorimotor deficits, among which impaired breathing is one of the most devastating and life-threatening. While clinical and experimental research has revealed that some spontaneous respiratory improvement (functional plasticity) can occur post-SCI, the extent of the recovery is limited and significant deficits persist. Thus, increasing effort is being made to develop therapies that harness and enhance this neuroplastic potential to optimize long-term recovery of breathing in injured individuals. One strategy with demonstrated therapeutic potential is the use of treatments that increase neural and muscular activity (e.g. locomotor training, neural and muscular stimulation) and promote plasticity. With a focus on respiratory function post-SCI, this review will discuss advances in the use of neural interfacing strategies and activity-based treatments, and highlights some recent results from our own research.
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Affiliation(s)
- Kristiina M Hormigo
- Spinal Cord Research Center, Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA, USA
| | - Lyandysha V Zholudeva
- Spinal Cord Research Center, Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA, USA
| | - Victoria M Spruance
- Spinal Cord Research Center, Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA, USA
| | - Vitaliy Marchenko
- Spinal Cord Research Center, Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA, USA
| | - Marie-Pascale Cote
- Spinal Cord Research Center, Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA, USA
| | - Stephane Vinit
- Université de Versailles Saint-Quentin-en-Yvelines, INSERM U1179 End:icap, UFR des Sciences de la Santé - Simone Veil, Montigny-le-Bretonneux, France
| | - Simon Giszter
- Spinal Cord Research Center, Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA, USA
| | - Tatiana Bezdudnaya
- Spinal Cord Research Center, Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA, USA
| | - Michael A Lane
- Spinal Cord Research Center, Department of Neurobiology and Anatomy, College of Medicine, Drexel University, 2900 W Queen Lane, Philadelphia, PA, USA.
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Navarrete-Opazo A, Dougherty BJ, Mitchell GS. Enhanced recovery of breathing capacity from combined adenosine 2A receptor inhibition and daily acute intermittent hypoxia after chronic cervical spinal injury. Exp Neurol 2017; 287:93-101. [PMID: 27079999 PMCID: PMC5193117 DOI: 10.1016/j.expneurol.2016.03.026] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 02/29/2016] [Accepted: 03/31/2016] [Indexed: 01/16/2023]
Abstract
Daily acute intermittent hypoxia (dAIH) improves breathing capacity after C2 spinal hemisection (C2HS) in rats. Since C2HS disrupts spinal serotonergic innervation below the injury, adenosine-dependent mechanisms underlie dAIH-induced functional recovery 2weeks post-injury. We hypothesized that dAIH-induced functional recovery converts from an adenosine-dependent to a serotonin-dependent, adenosine-constrained mechanism with chronic injury. Eight weeks post-C2HS, rats began dAIH (10, 5-min episodes, 10.5% O2; 5-min intervals; 7days) followed by AIH 3× per week (3×wAIH) for 8 additional weeks with/without systemic A2A receptor inhibition (KW6002) on each AIH exposure day. Tidal volume (VT) and bilateral diaphragm (Dia) and T2 external intercostal motor activity were assessed in unanesthetized rats breathing air and during maximum chemoreflex stimulation (MCS: 7% CO2, 10.5% O2). Nine weeks post-C2HS, dAIH increased VT versus time controls (p<0.05), an effect enhanced by KW6002 (p<0.05). dAIH increased bilateral Dia activity (p<0.05), and KW6002 enhanced this effect in contralateral (p<0.05) and ipsilateral Dia activity (p<0.001), but not T2 inspiratory activity. Functional benefits of combined AIH plus systemic A2A receptor inhibition were maintained for 4weeks. Thus, in rats with chronic injuries: 1) dAIH improves VT and bilateral diaphragm activity; 2) VT recovery is enhanced by A2A receptor inhibition; and 3) functional recovery with A2A receptor inhibition and AIH "reminders" last 4weeks. Combined dAIH and A2A receptor inhibition may be a simple, safe, and effective strategy to accelerate/enhance functional recovery of breathing capacity in patients with respiratory impairment from chronic spinal injury.
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Affiliation(s)
- A Navarrete-Opazo
- Department of Comparative Biosciences, University of Wisconsin, Madison, WI 53706, USA; Teletón Children Rehabilitation Institute, Alameda 4620, Santiago, Chile
| | - B J Dougherty
- Department of Comparative Biosciences, University of Wisconsin, Madison, WI 53706, USA
| | - G S Mitchell
- Department of Comparative Biosciences, University of Wisconsin, Madison, WI 53706, USA; Department of Physical Therapy, University of Florida, Gainesville, FL 32610, USA.
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Developmental plasticity in the neural control of breathing. Exp Neurol 2017; 287:176-191. [DOI: 10.1016/j.expneurol.2016.05.032] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Revised: 05/13/2016] [Accepted: 05/26/2016] [Indexed: 12/14/2022]
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Respiratory neuroplasticity – Overview, significance and future directions. Exp Neurol 2017; 287:144-152. [DOI: 10.1016/j.expneurol.2016.05.022] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2016] [Accepted: 05/17/2016] [Indexed: 01/10/2023]
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41
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Lee KZ, Chiang SC, Li YJ. Mild Acute Intermittent Hypoxia Improves Respiratory Function in Unanesthetized Rats With Midcervical Contusion. Neurorehabil Neural Repair 2016; 31:364-375. [DOI: 10.1177/1545968316680494] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Background. Mild intermittent hypoxia has been considered a potential approach to induce respiratory neuroplasticity. Objective. The purpose of the present study was to investigate whether mild acute intermittent hypoxia can improve breathing function in a clinically relevant spinal cord injury animal model. Methods. Adult male rats received laminectomy or unilateral contusion at the C3-C4 spinal cord using a MASCIS Impactor (height: 6.25 or 12.5 mm). At 4 weeks postinjury, the breathing patterns of unanesthetized rats were measured by whole body plethysmography before, during and after 10 episodes of 5 minutes of hypoxia (10% O2, 4% CO2, balance N2) with 5 minutes of normoxia intervals. Results. The results demonstrated that cervical contusion resulted in reduction in breathing capacity and number of phrenic motoneurons. Acute hypoxia induced significant increases in frequency and tidal volume in sham surgery and contused animals. In addition, there was a progressive decline in the magnitude of hypoxic ventilatory response during intermittent hypoxia. Further, the tidal volume was significantly enhanced in contused but not sham surgery rats at 15 and 30 minutes postintermittent hypoxia, suggesting intermittent hypoxia can bring about long-term facilitation of tidal volume following cervical spinal contusion. Conclusions. These results suggest that mild acute intermittent hypoxia can elicit differential forms of respiratory plasticity in sham surgery versus contused animals, and may be a promising neurorehabilitation approach to improve respiratory function after cervical spinal cord injury.
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Affiliation(s)
- Kun-Ze Lee
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
- Center for Neuroscience, National Sun Yat-sen University, Kaohsiung, Taiwan
- Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung, Taiwan
- Doctoral Degree Program in Marine Biotechnology, National Sun Yat-sen University and Academia Sinica, Taiwan
- Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Shu-Chi Chiang
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
| | - Yu-Jie Li
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
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Komnenov D, Solarewicz JZ, Afzal F, Nantwi KD, Kuhn DM, Mateika JH. Intermittent hypoxia promotes recovery of respiratory motor function in spinal cord-injured mice depleted of serotonin in the central nervous system. J Appl Physiol (1985) 2016; 121:545-57. [DOI: 10.1152/japplphysiol.00448.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 07/05/2016] [Indexed: 12/22/2022] Open
Abstract
We examined the effect of repeated daily exposure to intermittent hypoxia (IH) on the recovery of respiratory and limb motor function in mice genetically depleted of central nervous system serotonin. Electroencephalography, diaphragm activity, ventilation, core body temperature, and limb mobility were measured in spontaneously breathing wild-type (Tph2+/+) and tryptophan hydroxylase 2 knockout (Tph2−/−) mice. Following a C2 hemisection, the mice were exposed daily to IH (i.e., twelve 4-min episodes of 10% oxygen interspersed with 4-min normoxic periods followed by a 90-min end-recovery period) or normoxia (i.e., sham protocol, 21% oxygen) for 10 consecutive days. Diaphragm activity recovered to prehemisection levels in the Tph2+/+ and Tph2−/− mice following exposure to IH but not normoxia [Tph2+/+ 1.3 ± 0.2 (SE) vs. 0.3 ± 0.2; Tph2−/− 1.06 ± 0.1 vs. 0.3 ± 0.1, standardized to prehemisection values, P < 0.01]. Likewise, recovery of tidal volume and breathing frequency was evident, although breathing frequency values did not return to prehemisection levels within the time frame of the protocol. Partial recovery of limb motor function was also evident 2 wk after spinal cord hemisection. However, recovery was not dependent on IH or the presence of serotonin in the central nervous system. We conclude that IH promotes recovery of respiratory function but not basic motor tasks. Moreover, we conclude that spontaneous or treatment-induced recovery of respiratory and motor limb function is not dependent on serotonin in the central nervous system in a mouse model of spinal cord injury.
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Affiliation(s)
- Dragana Komnenov
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - Julia Z. Solarewicz
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - Fareeza Afzal
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - Kwaku D. Nantwi
- Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, Michigan
| | - Donald M. Kuhn
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, Michigan; and
| | - Jason H. Mateika
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
- Department of Internal Medicine, Wayne State University School of Medicine, Detroit, Michigan
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Braegelmann KM, Streeter KA, Fields DP, Baker TL. Plasticity in respiratory motor neurons in response to reduced synaptic inputs: A form of homeostatic plasticity in respiratory control? Exp Neurol 2016; 287:225-234. [PMID: 27456270 DOI: 10.1016/j.expneurol.2016.07.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2016] [Revised: 06/16/2016] [Accepted: 07/20/2016] [Indexed: 12/31/2022]
Abstract
For most individuals, the respiratory control system produces a remarkably stable and coordinated motor output-recognizable as a breath-from birth until death. Very little is understood regarding the processes by which the respiratory control system maintains network stability in the presence of changing physiological demands and network properties that occur throughout life. An emerging principle of neuroscience is that neural activity is sensed and adjusted locally to assure that neurons continue to operate in an optimal range, yet to date, it is unknown whether such homeostatic plasticity is a feature of the neurons controlling breathing. Here, we review the evidence that local mechanisms sense and respond to perturbations in respiratory neural activity, with a focus on plasticity in respiratory motor neurons. We discuss whether these forms of plasticity represent homeostatic plasticity in respiratory control. We present new analyses demonstrating that reductions in synaptic inputs to phrenic motor neurons elicit a compensatory enhancement of phrenic inspiratory motor output, a form of plasticity termed inactivity-induced phrenic motor facilitation (iPMF), that is proportional to the magnitude of activity deprivation. Although the physiological role of iPMF is not understood, we hypothesize that it has an important role in protecting the drive to breathe during conditions of prolonged or intermittent reductions in respiratory neural activity, such as following spinal cord injury or during central sleep apnea.
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Affiliation(s)
- K M Braegelmann
- Department of Comparative Biosciences, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706, United States
| | - K A Streeter
- Department of Comparative Biosciences, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706, United States
| | - D P Fields
- Department of Comparative Biosciences, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706, United States
| | - T L Baker
- Department of Comparative Biosciences, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706, United States.
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Lee KZ. Phrenic motor outputs in response to bronchopulmonary C-fibre activation following chronic cervical spinal cord injury. J Physiol 2016; 594:6009-6024. [PMID: 27106483 DOI: 10.1113/jp272287] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 04/19/2016] [Indexed: 01/20/2023] Open
Abstract
KEY POINTS Activation of bronchopulmonary C-fibres, the main chemosensitive afferents in the lung, can induce pulmonary chemoreflexes to modulate respiratory activity. Following chronic cervical spinal cord injury, bronchopulmonary C-fibre activation-induced inhibition of phrenic activity was exaggerated. Supersensitivity of phrenic motor outputs to the inhibitory effect of bronchopulmonary C-fibre activation is due to a shift of phrenic motoneuron types and slow recovery of phrenic motoneuron discharge in cervical spinal cord-injured animals. These data suggest that activation of bronchopulmonary C-fibres may retard phrenic output recovery following cervical spinal cord injury. The alteration of phenotype and discharge pattern of phrenic motoneuron enables us to understand the impact of spinal cord injury on spinal respiratory activity. ABSTRACT Cervical spinal injury interrupts bulbospinal pathways and results in cessation of phrenic bursting ipsilateral to the lesion. The ipsilateral phrenic activity can partially recover over weeks to months following injury due to the activation of latent crossed spinal pathways and exhibits a greater capacity to increase activity during respiratory challenges than the contralateral phrenic nerve. However, whether the bilateral phrenic nerves demonstrate differential responses to respiratory inhibitory inputs is unclear. Accordingly, the present study examined bilateral phrenic bursting in response to capsaicin-induced pulmonary chemoreflexes, a robust respiratory inhibitory stimulus. Bilateral phrenic nerve activity was recorded in anaesthetized and mechanically ventilated adult rats at 8-9 weeks after C2 hemisection (C2Hx) or C2 laminectomy. Intra-jugular capsaicin (1.5 μg kg-1 ) injection was performed to activate the bronchopulmonary C-fibres to evoke pulmonary chemoreflexes. The present results indicate that capsaicin-induced prolongation of expiratory duration was significantly attenuated in C2Hx animals. However, ipsilateral phrenic activity was robustly reduced after capsaicin treatment compared to uninjured animals. Single phrenic fibre recording experiments demonstrated that C2Hx animals had a higher proportion of late-inspiratory phrenic motoneurons that were relatively sensitive to capsaicin treatment compared to early-inspiratory phrenic motoneurons. Moreover, late-inspiratory phrenic motoneurons in C2Hx animals had a weaker discharge frequency and slower recovery time than uninjured animals. These results suggest bilateral phrenic nerves differentially respond to bronchopulmonary C-fibre activation following unilateral cervical hemisection, and the severe inhibition of phrenic bursting is due to a shift in the discharge pattern of phrenic motoneurons.
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Affiliation(s)
- Kun-Ze Lee
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan. .,Centre for Neuroscience, National Sun Yat-sen University, Kaohsiung, Taiwan. .,Doctoral Degree Program in Marine Biotechnology, National Sun Yat-sen University and Academia Sinica, Taiwan. .,Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung, Taiwan. .,Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung, Taiwan.
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Mateika JH, Komnenov D. Intermittent hypoxia initiated plasticity in humans: A multipronged therapeutic approach to treat sleep apnea and overlapping co-morbidities. Exp Neurol 2016; 287:113-129. [PMID: 27170208 DOI: 10.1016/j.expneurol.2016.05.011] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 03/18/2016] [Accepted: 05/03/2016] [Indexed: 10/21/2022]
Abstract
Over the past three decades exposure to intermittent hypoxia (IH) has generally been considered a stimulus associated with a number of detrimental outcomes. However, there is sufficient evidence to link IH to many beneficial outcomes but they have largely been ignored, particularly in the field of sleep medicine in the United States. Recent reviews have postulated that this apparent contradiction is related to the severity and duration of exposure to IH; mild forms of IH initiate beneficial outcomes while severe forms of IH are coupled to detrimental consequences. In the present review we explore the role that IH has in initiating respiratory plasticity and the potential this form of plasticity has to mitigate obstructive sleep apnea (OSA) in humans. In taking this approach, we address the possibility that IH could serve as an adjunct therapy coupled with continuous positive airway pressure (CPAP) to treat OSA. Our working hypothesis is that exposure to mild IH leads to respiratory plasticity that manifests in increased stability of the upper airway, which could ultimately reduce the CPAP required to treat OSA. In turn, this reduction could increase CPAP compliance and extend the length of treatment each night, which might improve the magnitude of outcome measures. Improved treatment compliance coupled with the direct effect that IH has on numerous overlapping conditions (i.e. asthma, chronic obstructive pulmonary disease, spinal cord injury) may well lead to substantial improvements that exceed outcomes following treatment with CPAP alone. Overall, this review will consider evidence from the published literature which suggests that IH could serve as an effective multipronged therapeutic approach to treat sleep apnea and its overlapping co-morbidities.
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Affiliation(s)
- Jason H Mateika
- John D. Dingell Veterans Affairs Medical Center, Detroit, MI 48201, United States; Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, United States; Department of Internal Medicine, Wayne State University School of Medicine, Detroit, MI 48201, United States.
| | - Dragana Komnenov
- John D. Dingell Veterans Affairs Medical Center, Detroit, MI 48201, United States; Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, United States
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Gonzalez-Rothi EJ, Armstrong GT, Cerreta AJ, Fitzpatrick GM, Reier PJ, Lane MA, Judge AR, Fuller DD. Forelimb muscle plasticity following unilateral cervical spinal cord injury. Muscle Nerve 2016; 53:475-8. [PMID: 26662579 PMCID: PMC4733411 DOI: 10.1002/mus.25007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/04/2015] [Indexed: 12/22/2022]
Abstract
INTRODUCTION Motor dysfunction and muscle atrophy are well documented in the lower extremity after spinal cord injury. However, the extent and time course of myoplastic changes in forelimb musculature is not clear. METHODS Forelimb muscle morphology and fiber type were evaluated after high cervical hemilesion injury in rats. RESULTS There was significant atrophy of the ipsilateral extensor carpi radialis longus (ECRL) muscle at 2 weeks postinjury, which was subsequently reversed at 8 weeks postinjury. The triceps muscle showed minimal evidence of atrophy after spinal injury. No significant changes in fiber type were observed. CONCLUSIONS These findings indicate a robust capacity for spontaneous myoplasticity after C2 hemisection injury but highlight differential capacity for plasticity within the forelimb muscles.
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Affiliation(s)
- Elisa J. Gonzalez-Rothi
- Department of Physical Therapy, College of Public Health and Health Professions, McKnight Brain Institute, University of Florida, P.O. Box 100154, 100 S. Newell Drive, Gainesville, FL 32610, USA
| | - Gregory T. Armstrong
- Department of Physical Therapy, College of Public Health and Health Professions, McKnight Brain Institute, University of Florida, P.O. Box 100154, 100 S. Newell Drive, Gainesville, FL 32610, USA
| | - Anthony J. Cerreta
- Department of Physical Therapy, College of Public Health and Health Professions, McKnight Brain Institute, University of Florida, P.O. Box 100154, 100 S. Newell Drive, Gainesville, FL 32610, USA
| | - Garrett M. Fitzpatrick
- Department of Physical Therapy, College of Public Health and Health Professions, McKnight Brain Institute, University of Florida, P.O. Box 100154, 100 S. Newell Drive, Gainesville, FL 32610, USA
| | - Paul J. Reier
- Department of Neuroscience, College of Medicine, McKnight Brain Institute, University of Florida, P.O. Box 100154, 100 S. Newell Drive, Gainesville, FL 32610, USA
| | - Michael A. Lane
- Department of Neuroscience, College of Medicine, McKnight Brain Institute, University of Florida, P.O. Box 100154, 100 S. Newell Drive, Gainesville, FL 32610, USA
| | - Andrew R. Judge
- Department of Physical Therapy, College of Public Health and Health Professions, McKnight Brain Institute, University of Florida, P.O. Box 100154, 100 S. Newell Drive, Gainesville, FL 32610, USA
| | - David D. Fuller
- Department of Physical Therapy, College of Public Health and Health Professions, McKnight Brain Institute, University of Florida, P.O. Box 100154, 100 S. Newell Drive, Gainesville, FL 32610, USA
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Reorganization of Respiratory Descending Pathways following Cervical Spinal Partial Section Investigated by Transcranial Magnetic Stimulation in the Rat. PLoS One 2016; 11:e0148180. [PMID: 26828648 PMCID: PMC4734706 DOI: 10.1371/journal.pone.0148180] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 01/14/2016] [Indexed: 01/24/2023] Open
Abstract
High cervical spinal cord injuries lead to permanent respiratory deficits. One preclinical model of respiratory insufficiency in adult rats is the C2 partial injury which causes unilateral diaphragm paralysis. This model allows the investigation of a particular population of respiratory bulbospinal axons which cross the midline at C3-C6 spinal segment, namely the crossed phrenic pathway. Transcranial magnetic stimulation (TMS) is a non-invasive technique that can be used to study supraspinal descending respiratory pathways in the rat. Interestingly, a lateral C2 injury does not affect the amplitude and latency of the largest motor-evoked potential recorded from the diaphragm (MEPdia) ipsilateral to the injury in response to a single TMS pulse, compared to a sham animal. Although the rhythmic respiratory activity on the contralateral diaphragm is preserved at 7 days post-injury, no diaphragm activity can be recorded on the injured side. However, a profound reorganization of the MEPdia evoked by TMS can be observed. The MEPdia is reduced on the non-injured rather than the injured side. This suggests an increase in ipsilateral phrenic motoneurons excitability. Moreover, correlations between MEPdia amplitude and spontaneous contralateral diaphragmatic activity were observed. The larger diaphragm activity correlated with a larger MEPdia on the injured side, and a smaller MEPdia on the non-injured side. This suggests, for the first time, the occurrence of a functional neuroplasticity process involving changes in motoneuron excitability balance between the injured and non-injured sides at a short post-lesional delay.
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Hsu SH, Lee KZ. Effects of serotonergic agents on respiratory recovery after cervical spinal injury. J Appl Physiol (1985) 2015; 119:1075-87. [DOI: 10.1152/japplphysiol.00329.2015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 09/07/2015] [Indexed: 12/18/2022] Open
Abstract
Unilateral cervical spinal cord hemisection (i.e., C2Hx) usually interrupts the bulbospinal respiratory pathways and results in respiratory impairment. It has been demonstrated that activation of the serotonin system can promote locomotor recovery after spinal cord injury. The present study was designed to investigate whether serotonergic activation can improve respiratory function during the chronic injury state. Bilateral diaphragm electromyogram and tidal volume were measured in anesthetized and spontaneously breathing adult rats at 8 wk post-C2Hx or C2laminectomy. A bolus intravenous injection of a serotonin precursor [5-hydroxytryptophan (5-HTP), 10 mg/kg], a serotonin reuptake inhibitor (fluoxetine, 10 mg/kg), or a potent agonist for serotonin 2A receptors (TCB-2, 0.05 mg/kg) was used to activate the serotonergic system. Present results demonstrated that 5-HTP and TCB-2, but not fluoxetine, significantly increased the inspiratory activity of the diaphragm electromyogram ipsilateral to the lesion for at least 30 min in C2Hx animals, but not in animals that received sham surgery. However, the tidal volume was not increased after administration of 5-HTP or TCB-2, indicating that the enhancement of ipsilateral diaphragm activity is not associated with improvement of the tidal volume. These results suggest that exogenous activation of the serotonergic system can specifically enhance the ipsilateral diaphragmatic motor outputs, but this approach may not be sufficient to improve respiratory functional recovery following chronic cervical spinal injury.
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Affiliation(s)
- Shih-Hui Hsu
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
| | - Kun-Ze Lee
- Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
- Center for Neuroscience, National Sun Yat-sen University, Kaohsiung, Taiwan
- Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung, Taiwan
- Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung, Taiwan; and
- Doctoral Degree Program in Marine Biotechnology, National Sun Yat-sen University and Academia Sinica, Kaohsiung, Taiwan
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Abstract
Acute intermittent hypoxia (AIH) induces a form of spinal motor plasticity known as phrenic long-term facilitation (pLTF); pLTF is a prolonged increase in phrenic motor output after AIH has ended. In anesthetized rats, we demonstrate that pLTF requires activity of the novel PKC isoform, PKCθ, and that the relevant PKCθ is within phrenic motor neurons. Whereas spinal PKCθ inhibitors block pLTF, inhibitors targeting other PKC isoforms do not. PKCθ is highly expressed in phrenic motor neurons, and PKCθ knockdown with intrapleural siRNAs abolishes pLTF. Intrapleural siRNAs targeting PKCζ, an atypical PKC isoform expressed in phrenic motor neurons that underlies a distinct form of phrenic motor plasticity, does not affect pLTF. Thus, PKCθ plays a critical role in spinal AIH-induced respiratory motor plasticity, and the relevant PKCθ is localized within phrenic motor neurons. Intrapleural siRNA delivery has considerable potential as a therapeutic tool to selectively manipulate plasticity in vital respiratory motor neurons.
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Hoy KC, Alilain WJ. Acute theophylline exposure modulates breathing activity through a cervical contusion. Exp Neurol 2015; 271:72-6. [PMID: 25979115 DOI: 10.1016/j.expneurol.2015.04.024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Revised: 04/21/2015] [Accepted: 04/24/2015] [Indexed: 01/25/2023]
Abstract
Cervical spinal contusion injuries are the most common form of spinal cord injury (>50%) observed in humans. These injuries can result in the impaired ability to breathe. In this study we examine the role of theophylline in the rescue of breathing behavior after a cervical spinal contusion. Previous research in the C2 hemisection model has shown that acute administration of theophylline can rescue phrenic nerve activity and diaphragmatic EMG on the side ipsilateral to injury. However, this effect is dependent on intact and uninjured pathways. In this study we utilized a cervical contusion injury model that more closely mimics the human condition. This injury model can determine the effectiveness of therapeutic interventions, in this case theophylline, on the isolated contused pathways of the spinal cord. Three weeks after a 150 kD C3/4 unilateral contusion subjects received a 15 mg/kg dose of theophylline prior to a contralateral C2 hemisection. Subjects that received theophylline were able to effectively utilize damaged pathways to breathe for up to 2 min, while subjects treated with saline were unable to support ventilation. Through these experiments, we demonstrate that theophylline can make injured pathways that mediate breathing more effective and therefore, suggest a potential therapeutic role in the critical time points immediately after injury.
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Affiliation(s)
- Kevin C Hoy
- Department of Neurosciences, MetroHealth Medical Center, Case Western Reserve University School of Medicine, Cleveland, OH 44109, USA
| | - Warren J Alilain
- Department of Neurosciences, MetroHealth Medical Center, Case Western Reserve University School of Medicine, Cleveland, OH 44109, USA.
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