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Kitamura I, Frazure M, Iceman K, Koike T, Pitts T. Stochastic electrical stimulation of the thoracic or cervical regions with surface electrodes facilitates swallow in rats. Front Neurol 2024; 15:1390524. [PMID: 39045426 PMCID: PMC11263167 DOI: 10.3389/fneur.2024.1390524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Accepted: 06/20/2024] [Indexed: 07/25/2024] Open
Abstract
Introduction Aspiration pneumonia, a leading cause of mortality, poses an urgent challenge in contemporary society. Neuromuscular electrical stimulation (NMES) has been commonly used in dysphagia rehabilitation. However, given that NMES at motor threshold targets only specific muscles, it carries a potential risk of further compromising functions related to swallowing, respiration, and airway protection. Considering that the swallow motor pattern is orchestrated by the entire swallow pattern generator (the neural mechanism governing a sequence of swallow actions), a rehabilitation approach that centrally facilitates the entire circuit through sensory nerve stimulation is desirable. In this context, we propose a novel stimulation method using surface electrodes placed on the back to promote swallowing. Methods The efficacy of the proposed method in promoting swallowing was evaluated by electrically stimulating sensory nerves in the back or neck. Probabilistic stimulus was applied to either the back or neck of male and female rats. Swallows were evoked by an oral water stimulus, and electromyographic (EMG) activity of the mylohyoid, thyroarytenoid, and thyropharyngeus muscles served as the primary outcome measure. Results Gaussian frequency stimulation applied to the skin surface of the thoracic back elicited significant increases in EMG amplitude of all three swallow-related muscles. Neck stimulation elicited a significant increase in EMG amplitude of the thyroarytenoid during swallow, but not the mylohyoid or thyropharyngeus muscles. Discussion While the targeted thoracic spinal segments T9-T10 have been investigated for enhancing respiration, the promotion of swallowing through back stimulation has not been previously studied. Furthermore, this study introduces a new probabilistic stimulus based on Gaussian distribution. Probabilistic stimuli have been reported to excel in nerve stimulation in previous research. The results demonstrate that back stimulation effectively facilitated swallow more than neck stimulation and suggest potential applications for swallowing rehabilitation.
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Affiliation(s)
- In Kitamura
- Department of Mechanical and Intelligent Systems Engineering, The University of Electro-Communications, Chōfu, Tokyo, Japan
| | - Michael Frazure
- Department of Physiology, School of Medicine, University of Louisville, Louisville, KY, United States
| | - Kimberly Iceman
- Department of Speech, Language, and Hearing Sciences and Dalton Cardiovascular Center, University of Missouri, Columbia, MO, United States
| | - Takuji Koike
- Department of Mechanical and Intelligent Systems Engineering, The University of Electro-Communications, Chōfu, Tokyo, Japan
| | - Teresa Pitts
- Department of Speech, Language, and Hearing Sciences and Dalton Cardiovascular Center, University of Missouri, Columbia, MO, United States
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2
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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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3
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Galer EL, Huang R, Madhavan M, Wang E, Zhou Y, Leiter JC, Lu DC. Cervical Epidural Electrical Stimulation Increases Respiratory Activity through Somatostatin-Expressing Neurons in the Dorsal Cervical Spinal Cord in Rats. J Neurosci 2023; 43:419-432. [PMID: 36639888 PMCID: PMC9864577 DOI: 10.1523/jneurosci.1958-21.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 09/21/2022] [Accepted: 09/29/2022] [Indexed: 12/12/2022] Open
Abstract
We tested the hypothesis that dorsal cervical epidural electrical stimulation (CEES) increases respiratory activity in male and female anesthetized rats. Respiratory frequency and minute ventilation were significantly increased when CEES was applied dorsally to the C2-C6 region of the cervical spinal cord. By injecting pseudorabies virus into the diaphragm and using c-Fos activity to identify neurons activated during CEES, we found neurons in the dorsal horn of the cervical spinal cord in which c-Fos and pseudorabies were co-localized, and these neurons expressed somatostatin (SST). Using dual viral infection to express the inhibitory Designer Receptors Exclusively Activated by Designer Drugs (DREADD), hM4D(Gi), selectively in SST-positive cells, we inhibited SST-expressing neurons by administering Clozapine N-oxide (CNO). During CNO-mediated inhibition of SST-expressing cervical spinal neurons, the respiratory excitation elicited by CEES was diminished. Thus, dorsal cervical epidural stimulation activated SST-expressing neurons in the cervical spinal cord, likely interneurons, that communicated with the respiratory pattern generating network to effect changes in ventilation.SIGNIFICANCE STATEMENT A network of pontomedullary neurons within the brainstem generates respiratory behaviors that are susceptible to modulation by a variety of inputs; spinal sensory and motor circuits modulate and adapt this output to meet the demands placed on the respiratory system. We explored dorsal cervical epidural electrical stimulation (CEES) excitation of spinal circuits to increase ventilation in rats. We identified dorsal somatostatin (SST)-expressing neurons in the cervical spinal cord that were activated (c-Fos-positive) by CEES. CEES no longer stimulated ventilation during inhibition of SST-expressing spinal neuronal activity, thereby demonstrating that spinal SST neurons participate in the activation of respiratory circuits affected by CEES. This work establishes a mechanistic foundation to repurpose a clinically accessible neuromodulatory therapy to activate respiratory circuits and stimulate ventilation.
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Affiliation(s)
- Erika L Galer
- Department of Neurosurgery, University of California Los Angeles, Los Angeles 90095, California
- Department of Molecular Cellular and Integrative Physiology, University of California Los Angeles, Los Angeles 90095, California
| | - Ruyi Huang
- Department of Neurosurgery, University of California Los Angeles, Los Angeles 90095, California
| | - Meghna Madhavan
- Department of Neurosurgery, University of California Los Angeles, Los Angeles 90095, California
| | - Emily Wang
- Department of Neurosurgery, University of California Los Angeles, Los Angeles 90095, California
| | - Yan Zhou
- Department of Neurosurgery, University of California Los Angeles, Los Angeles 90095, California
| | - James C Leiter
- Department of Neurosurgery, University of California Los Angeles, Los Angeles 90095, California
- Research Service, White River Junction VA Medical Center, White River Junction 05009, Vermont
| | - Daniel C Lu
- Department of Neurosurgery, University of California Los Angeles, Los Angeles 90095, California
- Department of Molecular Cellular and Integrative Physiology, University of California Los Angeles, Los Angeles 90095, California
- Brain Research Institute, University of California Los Angeles, Los Angeles 90095, California
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4
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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: 0] [Impact Index Per Article: 0] [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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Huang R, Worrell J, Garner E, Wang S, Homsey T, Xu B, Galer EL, Zhou Y, Tavakol S, Daneshvar M, Le T, Vinters HV, Salamon N, McArthur DL, Nuwer MR, Wu I, Leiter JC, Lu DC. Epidural electrical stimulation of the cervical spinal cord opposes opioid-induced respiratory depression. J Physiol 2022; 600:2973-2999. [PMID: 35639046 DOI: 10.1113/jp282664] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 03/25/2022] [Indexed: 02/02/2023] Open
Abstract
Opioid overdose suppresses brainstem respiratory circuits, causes apnoea and may result in death. Epidural electrical stimulation (EES) at the cervical spinal cord facilitated motor activity in rodents and humans, and we hypothesized that EES of the cervical spinal cord could antagonize opioid-induced respiratory depression in humans. Eighteen patients requiring surgical access to the dorsal surface of the spinal cord between C2 and C7 received EES or sham stimulation for up to 90 s at 5 or 30 Hz during complete (OFF-State) or partial suppression (ON-State) of respiration induced by remifentanil. During the ON-State, 30 Hz EES at C4 and 5 Hz EES at C3/4 increased tidal volume and decreased the end-tidal carbon dioxide level compared to pre-stimulation control levels. EES of 5 Hz at C5 and C7 increased respiratory frequency compared to pre-stimulation control levels. In the OFF-State, 30 Hz cervical EES at C3/4 terminated apnoea and induced rhythmic breathing. In cadaveric tissue obtained from a brain bank, more neurons expressed both the neurokinin 1 receptor (NK1R) and somatostatin (SST) in the cervical spinal levels responsive to EES (C3/4, C6 and C7) compared to a region non-responsive to EES (C2). Thus, the capacity of cervical EES to oppose opioid depression of respiration may be mediated by NK1R+/SST+ neurons in the dorsal cervical spinal cord. This study provides proof of principle that cervical EES may provide a novel therapeutic approach to augment respiratory activity when the neural function of the central respiratory circuits is compromised by opioids or other pathological conditions. KEY POINTS: Epidural electrical stimulation (EES) using an implanted spinal cord stimulator (SCS) is an FDA-approved method to manage chronic pain. We tested the hypothesis that cervical EES facilitates respiration during administration of opioids in 18 human subjects who were treated with low-dose remifentanil that suppressed respiration (ON-State) or high-dose remifentanil that completely inhibited breathing (OFF-State) during the course of cervical surgery. Dorsal cervical EES of the spinal cord augmented the respiratory tidal volume or increased the respiratory frequency, and the response to EES varied as a function of the stimulation frequency (5 or 30 Hz) and the cervical level stimulated (C2-C7). Short, continuous cervical EES restored a cyclic breathing pattern (eupnoea) in the OFF-State, suggesting that cervical EES reversed the opioid-induced respiratory depression. These findings add to our understanding of respiratory pattern modulation and suggest a novel mechanism to oppose the respiratory depression caused by opioids.
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Affiliation(s)
- Ruyi Huang
- Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Neuromotor Recovery and Rehabilitation Center, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Interdepartmental Program in Neuroscience, University of California, Los Angeles, CA, USA
| | - Jason Worrell
- Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Neuromotor Recovery and Rehabilitation Center, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Eric Garner
- Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Stephanie Wang
- Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Neuromotor Recovery and Rehabilitation Center, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Tali Homsey
- Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Neuromotor Recovery and Rehabilitation Center, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Bo Xu
- Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Neuromotor Recovery and Rehabilitation Center, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Erika L Galer
- Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Neuromotor Recovery and Rehabilitation Center, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Molecular, Cellular, Integrated Physiology Program, University of California, Los Angeles, CA, USA
| | - Yan Zhou
- Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Neuromotor Recovery and Rehabilitation Center, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Sherwin Tavakol
- Department of Neurosurgery, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Meelod Daneshvar
- University of California Fresno, Department of Surgery, Fresno, CA, USA
| | - Timothy Le
- Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Neuromotor Recovery and Rehabilitation Center, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Harry V Vinters
- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Brain Research Institute, University of California, Los Angeles, CA, USA
| | - Noriko Salamon
- Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - David L McArthur
- Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Marc R Nuwer
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Irene Wu
- Department of Anesthesiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - James C Leiter
- Department of Molecular and Systems Biology, Geisel School of Medicine, Lebanon, NH, USA
| | - Daniel C Lu
- Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Neuromotor Recovery and Rehabilitation Center, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Interdepartmental Program in Neuroscience, University of California, Los Angeles, CA, USA.,Brain Research Institute, University of California, Los Angeles, CA, USA
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6
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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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7
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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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8
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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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9
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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 DOI: 10.1152/jn.00625.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [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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Bezdudnaya T, Lane MA, Marchenko V. Pharmacological disinhibition enhances paced breathing following complete spinal cord injury in rats. Respir Physiol Neurobiol 2020; 282:103514. [PMID: 32750492 PMCID: PMC9793860 DOI: 10.1016/j.resp.2020.103514] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 07/12/2020] [Accepted: 07/29/2020] [Indexed: 12/30/2022]
Abstract
Respiratory dysfunction is one of the most devastating and life-threatening deficits that occurs following cervical spinal cord injury (SCI). Assisted breathing with mechanical ventilators is a necessary part of care for many cervical injured individuals, but it is also associated with increased risk of secondary complications such as infection, muscle atrophy and maladaptive plasticity. Pre-clinical studies with epidural stimulation (EDS) have identified it as an alternative/additional method to support adequate lung ventilation without mechanical assistance. The full potential of EDS, however, may be limited by spinal inhibitory mechanisms within the injured spinal cord. The goal of the present work is to assess the potential improvement for EDS in combination with pharmacological disinhibition of spinal circuits following complete high cervical SCI. All experiments were performed in decerebrate, unanesthetized, non-paralyzed (n = 13) and paralyzed (n = 8) adult Sprague-Dawley rats 6 h following a complete C1 transection. The combination of high-frequency EDS (HF-EDS) at the C4 spinal segment with intrathecal delivery of GABA and glycine receptors antagonists (GABAzine and strychnine, respectively) resulted in significantly increased phrenic motor output, tidal volume and amplitude of diaphragm electrical activity compared to HF-EDS alone. Thus, it appears that spinal fast inhibitory mechanisms limit phrenic motor output and present a new neuropharmacological target to improve paced breathing in individuals with cervical SCI.
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Affiliation(s)
- T Bezdudnaya
- Drexel University College of Medicine, Department of Neurobiology & Anatomy, 2900 W Queen Lane, Philadelphia, PA, 19129, United States
| | - M A Lane
- Drexel University College of Medicine, Department of Neurobiology & Anatomy, 2900 W Queen Lane, Philadelphia, PA, 19129, United States
| | - V Marchenko
- Drexel University College of Medicine, Department of Neurobiology & Anatomy, 2900 W Queen Lane, Philadelphia, PA, 19129, United States; Medical College of Wisconsin, Department of Anesthesiology, 8701 W Watertown Plank Rd, Wauwatosa, WI, 53226, United States.
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