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Taylor CE, Mendenhall LE, Sunshine MD, Wilson JN, Calulot CM, Sun RC, Johnson LA, Alilain WJ. Sex and APOE genotype influence respiratory function under hypoxic and hypoxic-hypercapnic conditions. J Neurophysiol 2024; 132:23-33. [PMID: 38748407 DOI: 10.1152/jn.00255.2023] [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: 06/30/2023] [Revised: 04/12/2024] [Accepted: 05/08/2024] [Indexed: 06/12/2024] Open
Abstract
The apolipoprotein E (APOE) gene has been studied due to its influence on Alzheimer's disease (AD) development and work in an APOE mouse model recently demonstrated impaired respiratory motor plasticity following spinal cord injury (SCI). Individuals with AD often copresent with obstructive sleep apnea (OSA) characterized by cessations in breathing during sleep. Despite the prominence of APOE genotype and sex as factors in AD progression, little is known about the impact of these variables on respiratory control. Ventilation is tightly regulated across many systems, with respiratory rhythm formation occurring in the brainstem but modulated in response to chemoreception. Alterations within these modulatory systems may result in disruptions of appropriate respiratory control and ultimately, disease. Using mice expressing two different humanized APOE alleles, we characterized how sex and the presence of APOE3 or APOE4 influences ventilation during baseline breathing (normoxia) and during respiratory challenges. We show that sex and APOE genotype influence breathing during hypoxic challenge, which may have clinical implications in the context of AD and OSA. In addition, female mice, while responding robustly to hypoxia, were unable to recover to baseline respiratory levels, emphasizing sex differences in disordered breathing.NEW & NOTEWORTHY This study is the first to use whole body plethysmography (WBP) to measure the impact of APOE alleles on breathing under normoxia and during adverse respiratory challenges in a targeted replacement Alzheimer's model. Both sex and genotype were shown to affect breathing under normoxia, hypoxic challenge, and hypoxic-hypercapnic challenge. This work has important implications regarding the impact of genetics on respiratory control as well as applications pertaining to conditions of disordered breathing including sleep apnea and neurotrauma.
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Affiliation(s)
- Chase E Taylor
- Department of Neuroscience, University of Kentucky, Lexington, Kentucky, United States
- Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, Kentucky, United States
| | - Laura E Mendenhall
- Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, Kentucky, United States
| | - Michael D Sunshine
- Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, Kentucky, United States
| | - Jessica N Wilson
- Department of Neuroscience, University of Kentucky, Lexington, Kentucky, United States
- Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, Kentucky, United States
| | - Chris M Calulot
- Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, Kentucky, United States
| | - Ramon C Sun
- Department of Biochemistry & Molecular Biology, College of Medicine, University of Florida, Gainesville, Florida, United States
- Department of Biochemistry, University of Florida, Gainesville, Florida, United States
- Center for Advanced Spatial Biomolecule Research, University of Florida, Gainesville, Florida, United States
| | - Lance A Johnson
- Department of Physiology, University of Kentucky, Lexington, Kentucky, United States
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, Kentucky, United States
| | - Warren J Alilain
- Department of Neuroscience, University of Kentucky, Lexington, Kentucky, United States
- Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, Kentucky, United States
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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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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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Cheng L, Sami A, Ghosh B, Urban MW, Heinsinger NM, Liang SS, Smith GM, Wright MC, Li S, Lepore AC. LAR inhibitory peptide promotes recovery of diaphragm function and multiple forms of respiratory neural circuit plasticity after cervical spinal cord injury. Neurobiol Dis 2020; 147:105153. [PMID: 33127470 PMCID: PMC7726004 DOI: 10.1016/j.nbd.2020.105153] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 09/14/2020] [Accepted: 10/25/2020] [Indexed: 12/18/2022] Open
Abstract
Chondroitin sulfate proteoglycans (CSPGs), up-regulated in and around the lesion after traumatic spinal cord injury (SCI), are key extracellular matrix inhibitory molecules that limit axon growth and consequent recovery of function. CSPG-mediated inhibition occurs via interactions with axonal receptors, including leukocyte common antigen- related (LAR) phosphatase. We tested the effects of a novel LAR inhibitory peptide in rats after hemisection at cervical level 2, a SCI model in which bulbospinal inspiratory neural circuitry originating in the medullary rostral ventral respiratory group (rVRG) becomes disconnected from phrenic motor neuron (PhMN) targets in cervical spinal cord, resulting in persistent partial-to-complete diaphragm paralysis. LAR peptide was delivered by a soaked gelfoam, which was placed directly over the injury site immediately after C2 hemisection and replaced at 1 week post-injury. Axotomized rVRG axons originating in ipsilateral medulla or spared rVRG fibers originating in contralateral medulla were separately assessed by anterograde tracing via AAV2-mCherry injection into rVRG. At 8 weeks post-hemisection, LAR peptide significantly improved ipsilateral hemidiaphragm function, as assessed in vivo with electromyography recordings. LAR peptide promoted robust regeneration of ipsilateral-originating rVRG axons into and through the lesion site and into intact caudal spinal cord to reach PhMNs located at C3-C5 levels. Furthermore, regenerating rVRG axons re-established putative monosynaptic connections with their PhMNs targets. In addition, LAR peptide stimulated robust sprouting of both modulatory serotonergic axons and contralateral-originating rVRG fibers within the PhMN pool ipsilateral/ caudal to the hemisection. Our study demonstrates that targeting LAR-based axon growth inhibition promotes multiple forms of respiratory neural circuit plasticity and provides a new peptide-based therapeutic strategy to ameliorate the devastating respiratory consequences of SCI.
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Affiliation(s)
- Lan Cheng
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA 19107, United States of America
| | - Armin Sami
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA 19107, United States of America
| | - Biswarup Ghosh
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA 19107, United States of America
| | - Mark W Urban
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA 19107, United States of America
| | - Nicolette M Heinsinger
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA 19107, United States of America
| | - Sophia S Liang
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA 19107, United States of America
| | - 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 of America
| | - Megan C Wright
- Department of Biology, Arcadia University, Glenside, PA 19038, United States of America
| | - Shuxin Li
- Department of Anatomy and Cell Biology, Shriners Hospitals for Pediatric Research Center, Temple University School of Medicine, 3500 North Broad Street, Philadelphia, PA 19140-5104, United States of America
| | - Angelo C Lepore
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA 19107, United States of America.
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A Review of Different Stimulation Methods for Functional Reconstruction and Comparison of Respiratory Function after Cervical Spinal Cord Injury. Appl Bionics Biomech 2020; 2020:8882430. [PMID: 33014127 PMCID: PMC7519444 DOI: 10.1155/2020/8882430] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 07/30/2020] [Accepted: 09/07/2020] [Indexed: 11/27/2022] Open
Abstract
Background Spinal cord injury (SCI) is a common severe trauma in clinic, hundreds of thousands of people suffer from which every year in the world. In terms of injury location, cervical spinal cord injury (CSCI) has the greatest impact. After cervical spinal cord injury, the lack of innervated muscles is not enough to provide ventilation and other activities to complete the respiratory function. In addition to the decline of respiratory capacity, respiratory complications also have a serious impact on the life of patients. The most commonly used assisted breathing and cough equipment is the ventilator, but in recent years, the functional electrical stimulation method is being used gradually and widely. Methods About hundred related academic papers are cited for data analysis. They all have the following characteristics: (1) basic conditions of patients were reported, (2) patients had received nerve or muscle stimulation and the basic parameters, and (3) the results were evaluated based on some indicators. Results The papers mentioned above are classified as four kinds of stimulation methods: muscle electric/magnetic stimulation, spinal dural electric stimulation, intraspinal microstimulation, and infrared light stimulation. This paper describes the stimulation principle and application experiment. Finally, this paper will compare the indexes and effects of typical stimulation methods, as well as the two auxiliary methods: training and operation. Conclusions Although there is limited evidence for the treatment of respiratory failure by nerve or muscle stimulation after cervical spinal cord injury, the two techniques seem to be safe and effective. At the same time, light stimulation is gradually applied to clinical medicine with its strong advantages and becomes the development trend of nerve stimulation in the future.
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Long-Distance Axon Regeneration Promotes Recovery of Diaphragmatic Respiratory Function after Spinal Cord Injury. eNeuro 2019; 6:ENEURO.0096-19.2019. [PMID: 31427403 PMCID: PMC6794082 DOI: 10.1523/eneuro.0096-19.2019] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 06/11/2019] [Accepted: 06/14/2019] [Indexed: 12/14/2022] Open
Abstract
Compromise in inspiratory breathing following cervical spinal cord injury (SCI) is caused by damage to descending bulbospinal axons originating in the rostral ventral respiratory group (rVRG) and consequent denervation and silencing of phrenic motor neurons (PhMNs) that directly control diaphragm activation. In a rat model of high-cervical hemisection SCI, we performed systemic administration of an antagonist peptide directed against phosphatase and tensin homolog (PTEN), a central inhibitor of neuron-intrinsic axon growth potential. PTEN antagonist peptide (PAP4) robustly restored diaphragm function, as determined with electromyography (EMG) recordings in living SCI animals. PAP4 promoted substantial, long-distance regeneration of injured rVRG axons through the lesion and back toward PhMNs located throughout the C3–C5 spinal cord. These regrowing rVRG axons also formed putative excitatory synaptic connections with PhMNs, demonstrating reconnection of rVRG-PhMN-diaphragm circuitry. Lastly, re-lesion through the hemisection site completely ablated functional recovery induced by PAP4. Collectively, our findings demonstrate that axon regeneration in response to systemic PAP4 administration promoted recovery of diaphragmatic respiratory function after cervical SCI.
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7
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Goulão M, Ghosh B, Urban MW, Sahu M, Mercogliano C, Charsar BA, Komaravolu S, Block CG, Smith GM, Wright MC, Lepore AC. Astrocyte progenitor transplantation promotes regeneration of bulbospinal respiratory axons, recovery of diaphragm function, and a reduced macrophage response following cervical spinal cord injury. Glia 2018; 67:452-466. [PMID: 30548313 DOI: 10.1002/glia.23555] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 09/10/2018] [Accepted: 10/11/2018] [Indexed: 02/06/2023]
Abstract
Stem/progenitor cell transplantation delivery of astrocytes is a potentially powerful strategy for spinal cord injury (SCI). Axon extension into SCI lesions that occur spontaneously or in response to experimental manipulations is often observed along endogenous astrocyte "bridges," suggesting that augmenting this response via astrocyte lineage transplantation can enhance axon regrowth. Given the importance of respiratory dysfunction post-SCI, we transplanted glial-restricted precursors (GRPs)-a class of lineage-restricted astrocyte progenitors-into the C2 hemisection model and evaluated effects on diaphragm function and the growth response of descending rostral ventral respiratory group (rVRG) axons that innervate phrenic motor neurons (PhMNs). GRPs survived long term and efficiently differentiated into astrocytes in injured spinal cord. GRPs promoted significant recovery of diaphragm electromyography amplitudes and stimulated robust regeneration of injured rVRG axons. Although rVRG fibers extended across the lesion, no regrowing axons re-entered caudal spinal cord to reinnervate PhMNs, suggesting that this regeneration response-although impressive-was not responsible for recovery. Within ipsilateral C3-5 ventral horn (PhMN location), GRPs induced substantial sprouting of spared fibers originating in contralateral rVRG and 5-HT axons that are important for regulating PhMN excitability; this sprouting was likely involved in functional effects of GRPs. Finally, GRPs reduced the macrophage response (which plays a key role in inducing axon retraction and limiting regrowth) both within the hemisection and at intact caudal spinal cord surrounding PhMNs. These findings demonstrate that astrocyte progenitor transplantation promotes significant plasticity of rVRG-PhMN circuitry and restoration of diaphragm function and suggest that these effects may be in part through immunomodulation.
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Affiliation(s)
- Miguel Goulão
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania.,Life and Health Sciences Research Institute (ICVS), School of Medicine, ICVS/3B's - PT Government Associate Laborator, University of Minho, Braga, Portugal
| | - Biswarup Ghosh
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Mark W Urban
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Malya Sahu
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Christina Mercogliano
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Brittany A Charsar
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Sreeya Komaravolu
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Cole G Block
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania
| | - George M Smith
- Department of Neuroscience, Shriners Hospitals Pediatric Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania
| | - Megan C Wright
- Department of Biology, Arcadia University, Glenside, Pennsylvania
| | - Angelo C Lepore
- Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania
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Local BDNF Delivery to the Injured Cervical Spinal Cord using an Engineered Hydrogel Enhances Diaphragmatic Respiratory Function. J Neurosci 2018; 38:5982-5995. [PMID: 29891731 DOI: 10.1523/jneurosci.3084-17.2018] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 05/16/2018] [Accepted: 05/17/2018] [Indexed: 02/07/2023] Open
Abstract
We developed an innovative biomaterial-based approach to repair the critical neural circuitry that controls diaphragm activation by locally delivering brain-derived neurotrophic factor (BDNF) to injured cervical spinal cord. BDNF can be used to restore respiratory function via a number of potential repair mechanisms; however, widespread BDNF biodistribution resulting from delivery methods such as systemic injection or lumbar puncture can lead to inefficient drug delivery and adverse side effects. As a viable alternative, we developed a novel hydrogel-based system loaded with polysaccharide-BDNF particles self-assembled by electrostatic interactions that can be safely implanted in the intrathecal space for achieving local BDNF delivery with controlled dosing and duration. Implantation of BDNF hydrogel after C4/C5 contusion-type spinal cord injury (SCI) in female rats robustly preserved diaphragm function, as assessed by in vivo recordings of compound muscle action potential and electromyography amplitudes. However, BDNF hydrogel did not decrease lesion size or degeneration of cervical motor neuron soma, suggesting that its therapeutic mechanism of action was not neuroprotection within spinal cord. Interestingly, BDNF hydrogel significantly preserved diaphragm innervation by phrenic motor neurons (PhMNs), as assessed by detailed neuromuscular junction morphological analysis and retrograde PhMN labeling from diaphragm using cholera toxin B. Furthermore, BDNF hydrogel enhanced the serotonergic axon innervation of PhMNs that plays an important role in modulating PhMN excitability. Our findings demonstrate that local BDNF hydrogel delivery is a robustly effective and safe strategy to restore diaphragm function after SCI. In addition, we demonstrate novel therapeutic mechanisms by which BDNF can repair respiratory neural circuitry.SIGNIFICANCE STATEMENT Respiratory compromise is a leading cause of morbidity and mortality following traumatic spinal cord injury (SCI). We used an innovative biomaterial-based drug delivery system in the form of a hydrogel that can be safely injected into the intrathecal space for achieving local delivery of brain-derived neurotrophic factor (BDNF) with controlled dosing and duration, while avoiding side effects associated with other delivery methods. In a clinically relevant rat model of cervical contusion-type SCI, BDNF hydrogel robustly and persistently improved diaphragmatic respiratory function by enhancing phrenic motor neuron (PhMN) innervation of the diaphragm neuromuscular junction and by increasing serotonergic innervation of PhMNs in ventral horn of the cervical spinal cord. These exciting findings demonstrate that local BDNF hydrogel delivery is a safe and robustly effective strategy to maintain respiratory function after cervical SCI.
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Guertin PA. New avenues for reducing intensive care needs in patients with chronic spinal cord injury. World J Crit Care Med 2016; 5:201-203. [PMID: 27896143 PMCID: PMC5109918 DOI: 10.5492/wjccm.v5.i4.201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 07/05/2016] [Accepted: 08/15/2016] [Indexed: 02/06/2023] Open
Abstract
Relatively soon after their accident, patients suffering a spinal cord injury (SCI) begin generally experiencing the development of significant, often life-threatening secondary complications. Many of which are associated with chronic physical inactivity-related immune function problems and increasing susceptibility to infection that repeatedly requires intensive care treatment. Therapies capable of repairing the spinal cord or restoring ambulation would normally prevent many of these problems but, as of now, there is no cure for SCI. Thus, management strategies and antibiotics remain the standard of care although antimicrobial resistance constitutes a significant challenge for patients with chronic SCI facing recurrent infections of the urinary tract and respiratory systems. Identifying alternative therapies capable of safe and potent actions upon these serious health concerns should therefore be considered a priority. This editorial presents some of the novel approaches currently in development for the prevention of specific infections after SCI. Among them, brain-permeable small molecule therapeutics acting centrally on spinal cord circuits that can augment respiratory capabilities or bladder functions. If eventually approved by regulatory authorities, some of these new avenues may potentially become clinically-relevant therapies capable of indirectly preventing the occurrence and/or severity of these life-threatening complications in people with paraplegic or tetraplegic injuries.
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Neuroprotective and Neurorestorative Processes after Spinal Cord Injury: The Case of the Bulbospinal Respiratory Neurons. Neural Plast 2016; 2016:7692602. [PMID: 27563469 PMCID: PMC4987469 DOI: 10.1155/2016/7692602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 06/29/2016] [Indexed: 11/18/2022] Open
Abstract
High cervical spinal cord injuries interrupt the bulbospinal respiratory pathways projecting to the cervical phrenic motoneurons resulting in important respiratory defects. In the case of a lateralized injury that maintains the respiratory drive on the opposite side, a partial recovery of the ipsilateral respiratory function occurs spontaneously over time, as observed in animal models. The rodent respiratory system is therefore a relevant model to investigate the neuroplastic and neuroprotective mechanisms that will trigger such phrenic motoneurons reactivation by supraspinal pathways. Since part of this recovery is dependent on the damaged side of the spinal cord, the present review highlights our current understanding of the anatomical neuroplasticity processes that are developed by the surviving damaged bulbospinal neurons, notably axonal sprouting and rerouting. Such anatomical neuroplasticity relies also on coordinated molecular mechanisms at the level of the axotomized bulbospinal neurons that will promote both neuroprotection and axon growth.
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11
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Charsar BA, Urban MW, Lepore AC. Harnessing the power of cell transplantation to target respiratory dysfunction following spinal cord injury. Exp Neurol 2016; 287:268-275. [PMID: 27531634 DOI: 10.1016/j.expneurol.2016.08.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 07/29/2016] [Accepted: 08/12/2016] [Indexed: 12/13/2022]
Abstract
The therapeutic benefit of cell transplantation has been assessed in a host of central nervous system (CNS) diseases, including disorders of the spinal cord such as traumatic spinal cord injury (SCI). The promise of cell transplantation to preserve and/or restore normal function can be aimed at a variety of therapeutic mechanisms, including replacement of lost or damaged CNS cell types, promotion of axonal regeneration or sprouting, neuroprotection, immune response modulation, and delivery of gene products such as neurotrophic factors, amongst other possibilities. Despite significant work in the field of transplantation in models of SCI, limited attention has been directed at harnessing the therapeutic potential of cell grafting for preserving respiratory function after SCI, despite the critical role pulmonary compromise plays in patient outcome in this devastating disease. Here, we will review the limited number of studies that have demonstrated the therapeutic potential of intraspinal transplantation of a variety of cell types for addressing respiratory dysfunction in SCI.
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Affiliation(s)
- Brittany A Charsar
- Department of Neuroscience, Farber Institute for Neurosciences, Sidney Kimmel Medical College, Thomas Jefferson University, 900 Walnut Street, JHN 418, Philadelphia, PA, 19107, United States
| | - Mark W Urban
- Department of Neuroscience, Farber Institute for Neurosciences, Sidney Kimmel Medical College, Thomas Jefferson University, 900 Walnut Street, JHN 418, Philadelphia, PA, 19107, United States
| | - Angelo C Lepore
- Department of Neuroscience, Farber Institute for Neurosciences, Sidney Kimmel Medical College, Thomas Jefferson University, 900 Walnut Street, JHN 418, Philadelphia, PA, 19107, United States.
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12
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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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