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Hernandez-Morato I, Koss S, Honzel E, Pitman MJ. Netrin-1 as A neural guidance protein in development and reinnervation of the larynx. Ann Anat 2024; 254:152247. [PMID: 38458575 DOI: 10.1016/j.aanat.2024.152247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 02/01/2024] [Accepted: 03/05/2024] [Indexed: 03/10/2024]
Abstract
Neural guidance proteins participate in motor neuron migration, axonal projection, and muscle fiber innervation during development. One of the guidance proteins that participates in axonal pathfinding is Netrin-1. Despite the well-known role of Netrin-1 in embryogenesis of central nervous tissue, it is still unclear how the expression of this guidance protein contributes to primary innervation of the periphery, as well as reinnervation. This is especially true in the larynx where Netrin-1 is upregulated within the intrinsic laryngeal muscles after nerve injury and where blocking of Netrin-1 alters the pattern of reinnervation of the intrinsic laryngeal muscles. Despite this consistent finding, it is unknown how Netrin-1 expression contributes to guidance of the axons towards the larynx. Improved knowledge of Netrin-1's role in nerve regeneration and reinnervation post-injury in comparison to its role in primary innervation during embryological development, may provide insights in the search for therapeutics to treat nerve injury. This paper reviews the known functions of Netrin-1 during the formation of the central nervous system and during cranial nerve primary innervation. It also describes the role of Netrin-1 in the formation of the larynx and during recurrent laryngeal reinnervation following nerve injury in the adult.
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Affiliation(s)
- Ignacio Hernandez-Morato
- Department of Otolaryngology-Head & Neck Surgery, The Center for Voice and Swallowing, Columbia University College of Physicians and Surgeons, New York, NY, United States; Department of Anatomy and Embryology, School of Medicine, Complutense University of Madrid, Madrid, Madrid, Spain.
| | - Shira Koss
- ENT Associates of Nassau County, Levittown, NY, United States
| | - Emily Honzel
- Department of Otolaryngology-Head & Neck Surgery, The Center for Voice and Swallowing, Columbia University College of Physicians and Surgeons, New York, NY, United States
| | - Michael J Pitman
- Department of Otolaryngology-Head & Neck Surgery, The Center for Voice and Swallowing, Columbia University College of Physicians and Surgeons, New York, NY, United States
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2
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Pennington-FitzGerald W, Joshi A, Honzel E, Hernandez-Morato I, Pitman MJ, Moayedi Y. Development and Application of Automated Vocal Fold Tracking Software in a Rat Surgical Model. Laryngoscope 2024; 134:340-346. [PMID: 37543969 DOI: 10.1002/lary.30930] [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: 01/24/2023] [Revised: 06/21/2023] [Accepted: 07/15/2023] [Indexed: 08/08/2023]
Abstract
OBJECTIVE The rat is a widely used model for studying vocal fold (VF) function after recurrent laryngeal nerve injury, but common techniques for evaluating rat VF motion remain subjective and imprecise. To address this, we developed a software package, called RatVocalTracker1.0 (RVT1.0), to quantify VF motion and tested it on rats with iatrogenic unilateral vocal fold paralysis (VFP). METHODS A deep neural network was trained to identify the positions of the VFs and arytenoid cartilages (ACs) in transoral laryngoscope videos of the rat glottis. Software was developed to estimate glottic midline, VF displacement, VF velocity, and AC angle. The software was applied to laryngoscope videos of adult rats before and after right recurrent and superior laryngeal nerve transection (N = 15; 6M, 9F). All software calculated metrics were compared before and after injury and validated against manually calculated metrics. RESULTS RVT1.0 accurately tracked and quantified VF displacement, VF velocity, and AC angle. Significant differences were found before and after surgery for all RVT1.0 calculated metrics. There was strong agreement between programmatically and manually calculated measures. Automated analysis was also more efficient than nearly all manual methods. CONCLUSION This approach provides fast, accurate assessment of VF motion in rats with minimal labor and allows for quantitative comparison of lateral differences in movement. Through this novel analysis method, we can differentiate healthy movement from unilateral VFP. RVT1.0 is open-source and will be a valuable tool for researchers using the rat model for laryngology research. LEVEL OF EVIDENCE NA Laryngoscope, 134:340-346, 2024.
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Affiliation(s)
| | - Abhinav Joshi
- The Center for Voice and Swallowing, Department of Otolaryngology-Head & Neck Surgery, Columbia University Irving Medical Center, New York, New York, U.S.A
| | - Emily Honzel
- College of Physicians and Surgeons, Columbia University, New York, New York, U.S.A
| | - Ignacio Hernandez-Morato
- The Center for Voice and Swallowing, Department of Otolaryngology-Head & Neck Surgery, Columbia University Irving Medical Center, New York, New York, U.S.A
| | - Michael J Pitman
- The Center for Voice and Swallowing, Department of Otolaryngology-Head & Neck Surgery, Columbia University Irving Medical Center, New York, New York, U.S.A
| | - Yalda Moayedi
- The Center for Voice and Swallowing, Department of Otolaryngology-Head & Neck Surgery, Columbia University Irving Medical Center, New York, New York, U.S.A
- Department of Neurology, Columbia University, New York, New York, U.S.A
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3
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Lever TE, Kloepper A, Welby L, Haney M, Fudge S, Seiller C, Kington S, Ballenger B, Nichols NL. Minimally Invasive Murine Laryngoscopy for Close-Up Imaging of Laryngeal Motion during Breathing and Swallowing. J Vis Exp 2023:10.3791/66089. [PMID: 38108389 PMCID: PMC11101017 DOI: 10.3791/66089] [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] [Indexed: 12/19/2023] Open
Abstract
The larynx is an essential organ in mammals with three primary functions - breathing, swallowing, and vocalizing. A wide range of disorders are known to impair laryngeal function, which results in difficulty breathing (dyspnea), swallowing impairment (dysphagia), and/or voice impairment (dysphonia). Dysphagia, in particular, can lead to aspiration pneumonia and associated morbidity, recurrent hospitalization, and early mortality. Despite these serious consequences, existing treatments for laryngeal dysfunction are largely aimed at surgical and behavioral interventions that unfortunately do not typically restore normal laryngeal function, thus highlighting the urgent need for innovative solutions. To bridge this gap, we have been developing an experimental endoscopic approach to investigate laryngeal dysfunction in murine (i.e., mouse and rat) models. However, endoscopy in rodents is quite challenging due to their small size relative to current endoscope technology, anatomical differences in the upper airway, and the necessity for anesthesia to optimally access the larynx. Here, we describe a novel transoral laryngoscopy approach that permits close-up, unobstructed video imaging of laryngeal motion in mice and rats. Critical steps in the protocol include precise anesthesia management (to prevent overdosing that abolishes swallowing and/or risks respiratory distress-related mortality) and micromanipulator control of the endoscope (for stable video recording of laryngeal motion by a single researcher for subsequent quantification). Importantly, the protocol can be performed over time in the same animals to study the impact of various pathological conditions specifically on laryngeal function. A novel advantage of this protocol is the ability to visualize airway protection during swallowing, which is not possible in humans due to epiglottic inversion over the laryngeal inlet that obstructs the glottis from view. Rodents therefore provide a unique opportunity to specifically investigate the mechanisms of normal versus pathological laryngeal airway protection for the ultimate purpose of discovering treatments to effectively restore normal laryngeal function.
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Affiliation(s)
- Teresa E Lever
- Department of Otolaryngology - Head and Neck Surgery, University of Missouri School of Medicine; Department of Biomedical Sciences, University of Missouri College of Veterinary Medicine;
| | - Ashley Kloepper
- Department of Otolaryngology - Head and Neck Surgery, University of Missouri School of Medicine
| | - Lauren Welby
- Division of Otolaryngology - Head and Neck Surgery, Texas A&M Health Science Center College of Medicine - Baylor Scott & White
| | - Megan Haney
- Department of Veterinary Pathobiology, University of Missouri College of Veterinary Medicine
| | - Shakera Fudge
- Department of Veterinary Pathobiology, University of Missouri College of Veterinary Medicine
| | - Chase Seiller
- Department of Medicine, University of Missouri School of Medicine
| | - Sophia Kington
- Department of Biomedical Sciences, University of Missouri College of Veterinary Medicine
| | | | - Nicole L Nichols
- Department of Biomedical Sciences, University of Missouri College of Veterinary Medicine
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Hernández-Morato I, Yu VX, Pitman MJ. A review of the peripheral proprioceptive apparatus in the larynx. Front Neuroanat 2023; 17:1114817. [PMID: 36910514 PMCID: PMC9998684 DOI: 10.3389/fnana.2023.1114817] [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: 12/02/2022] [Accepted: 01/19/2023] [Indexed: 03/14/2023] Open
Abstract
The larynx is an organ of the upper airway that participates in breathing, glutition, voice production, and airway protection. These complex functions depend on vocal fold (VF) movement, facilitated in turn by the action of the intrinsic laryngeal muscles (ILM). The necessary precise and near-instantaneous modulation of each ILM contraction relies on proprioceptive innervation of the larynx. Dysfunctional laryngeal proprioception likely contributes to disorders such as laryngeal dystonia, dysphagia, vocal fold paresis, and paralysis. While the proprioceptive system in skeletal muscle derived from somites is well described, the proprioceptive circuitry that governs head and neck structures such as VF has not been so well characterized. For over two centuries, researchers have investigated the question of whether canonical proprioceptive organs, muscle spindles, and Golgi tendon organs, exist in the ILM, with variable findings. The present work is a state-of-the-art review of the peripheral component of laryngeal proprioception, including current knowledge of canonical and possible alternative proprioceptive circuitry elements in the larynx.
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Affiliation(s)
- Ignacio Hernández-Morato
- Department of Otolaryngology-Head and Neck Surgery, Columbia University Irving Medical Center, New York, NY, United States
| | - Victoria X Yu
- Department of Otolaryngology-Head and Neck Surgery, Columbia University Irving Medical Center, New York, NY, United States
| | - Michael J Pitman
- Department of Otolaryngology-Head and Neck Surgery, Columbia University Irving Medical Center, New York, NY, United States
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5
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Kemfack AM, Hernandez-Morato I, Moayedi Y, Pitman MJ. An optimized method for high-quality RNA extraction from distinctive intrinsic laryngeal muscles in the rat model. Sci Rep 2022; 12:21665. [PMID: 36522411 PMCID: PMC9755529 DOI: 10.1038/s41598-022-25643-y] [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: 03/23/2022] [Accepted: 12/02/2022] [Indexed: 12/23/2022] Open
Abstract
Challenges related to high-quality RNA extraction from post-mortem tissue have limited RNA-sequencing (RNA-seq) application in certain skeletal muscle groups, including the intrinsic laryngeal muscles (ILMs). The present study identified critical factors contributing to substandard RNA extraction from the ILMs and established a suitable method that permitted high-throughput analysis. Here, standard techniques for tissue processing were adapted, and an effective means to control confounding effects during specimen preparation was determined. The experimental procedure consistently provided sufficient intact total RNA (N = 68) and RIN ranging between 7.0 and 8.6, which was unprecedented using standard RNA purification protocols. This study confirmed the reproducibility of the workflow through repeated trials at different postnatal time points and across the distinctive ILMs. High-throughput diagnostics from 90 RNA samples indicated no sequencing alignment scores below 70%, validating the extraction strategy. Significant differences between the standard and experimental conditions suggest circumvented challenges and broad applicability to other skeletal muscles. This investigation remains ongoing given the prospect of therapeutic insights to voice, swallowing, and airway disorders. The present methodology supports pioneering global transcriptome investigations in the larynx previously unfounded in literature.
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Affiliation(s)
- Angela M Kemfack
- Department of Otolaryngology-Head & Neck Surgery, Columbia University College of Physicians and Surgeons, New York, NY, 10032, USA
| | - Ignacio Hernandez-Morato
- Department of Otolaryngology-Head & Neck Surgery, Columbia University College of Physicians and Surgeons, New York, NY, 10032, USA.
| | - Yalda Moayedi
- Department of Otolaryngology-Head & Neck Surgery, Columbia University College of Physicians and Surgeons, New York, NY, 10032, USA
- Department of Neurology, Irving Medical Center, Columbia University College of Physicians and Surgeons, New York, NY, USA
| | - Michael J Pitman
- Department of Otolaryngology-Head & Neck Surgery, Columbia University College of Physicians and Surgeons, New York, NY, 10032, USA
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6
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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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7
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Caplan IF, Hernandez-Morato I, Pitman MJ. Temporal expression of Laminin-111 in the developing rat larynx. Neurosci Lett 2022; 781:136658. [PMID: 35483501 PMCID: PMC9194551 DOI: 10.1016/j.neulet.2022.136658] [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] [Received: 09/01/2021] [Revised: 04/08/2022] [Accepted: 04/22/2022] [Indexed: 12/31/2022]
Abstract
Laminin-111 is a basement membrane protein that participates in motor innervation and reinnervation. During axonal pathfinding, laminin-111 interacts with netrin-1 (NTN1) and changes its attractant growth cone properties into repulsion. While previous models of recurrent laryngeal nerve (RLN) transection show increased Laminin-111 and NTN1 production after injury, developmental expression in the larynx has not been defined. This study investigates the expression of laminin-111 in laryngeal muscles during primary laryngeal innervation of Sprague Dawley rats. Adult larynges and embryos were sectioned for immunohistochemistry with βIII-Tubulin, laminin subunit α-1 (LAMA1), NTN1, and α-bungarotoxin. Sections were processed for single-molecule inexpensive RNA fluorescence in situ hybridization analysis of LAMA1 mRNA. LAMA1 expression increased in all intrinsic laryngeal muscles, except the medial thyroarytenoid (MTA), at E20.5. At E20.5 there was increased expression in the lateral thyroarytenoid (LTA) and posterior cricoarytenoid (PCA) compared to the MTA. NTN1 upregulation was limited to the LTA and lateral cricoarytenoid (LCA) at E16.5 without any increase in the MTA or PCA. LAMA1 and NTN1 expression did not strictly follow expected patterns relative to the known timing of innervation and does not appear to be acting similarly to its role following RLN injury. These differences between developmental and post-injury innervation provide targets for investigations of therapeutics after nerve injury.
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Affiliation(s)
- Ian F. Caplan
- Columbia University Irving Medical Center/New York Presbyterian, Department of Otolaryngology Head & Neck Surgery, New York, NY, USA
| | - Ignacio Hernandez-Morato
- Columbia University Irving Medical Center/New York Presbyterian, Department of Otolaryngology Head & Neck Surgery, New York, NY, USA,Corresponding author at: Columbia University Irving Medical Center, Otolaryngology-Head and Neck Surgery, 180 Fort Washington Avenue, Rm 860 8th Floor. Harkness Pavilion, New York, NY 10032, USA. (I. Hernandez-Morato)
| | - Michael J. Pitman
- Columbia University Irving Medical Center/New York Presbyterian, Department of Otolaryngology Head & Neck Surgery, New York, NY, USA,Columbia University Irving Medical Center/New York Presbyterian, The Center for Voice and Swallowing, Department of Otolaryngology Head & Neck Surgery, New York, NY, USA
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8
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Laryngeal Paralysis Recovered Two Years after a Head Trauma by Growth Hormone Treatment and Neurorehabilitation. REPORTS 2021. [DOI: 10.3390/reports4030019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The aim of this study was to describe the cognitive and speech results obtained after growth hormone (GH) treatment and neurorehabilitation in a man who suffered a traumatic brain injury (TBI). Seventeen months after the accident, the patient was treated with growth hormone (GH), together with neurostimulation and speech therapy. At admission, the flexible laryngoscopy revealed that the left vocal cord was paralyzed, in the paramedian position, a situation compatible with a recurrent nerve injury. Clinical and rehabilitation assessments revealed a prompt improvement in speech and cognitive functions and, following completion of treatment, endoscopic examination showed recovery of vocal cord mobility. These results, together with previous results from our group, indicate that GH treatment is safe and effective for helping neurorehabilitation in chronic speech impairment due to central laryngeal paralysis, as well as impaired cognitive functions.
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Suzuki H, Araki K, Matsui T, Tanaka Y, Uno K, Tomifuji M, Yamashita T, Satoh Y, Kobayashi Y, Shiotani A. TrkA inhibitor promotes motor functional regeneration of recurrent laryngeal nerve by suppression of sensory nerve regeneration. Sci Rep 2020; 10:16892. [PMID: 33037246 PMCID: PMC7547101 DOI: 10.1038/s41598-020-72288-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Accepted: 08/19/2020] [Indexed: 11/19/2022] Open
Abstract
Recurrent laryngeal nerve (RLN) injury, in which hoarseness and dysphagia arise as a result of impaired vocal fold movement, is a serious complication. Misdirected regeneration is an issue for functional regeneration. In this study, we demonstrated the effect of TrkA inhibitors, which blocks the NGF-TrkA pathway that acts on the sensory/automatic nerves thus preventing misdirected regeneration among motor and sensory nerves, and thereby promoting the regeneration of motor neurons to achieve functional recovery. RLN axotomy rat models were used in this study, in which cut ends of the nerve were bridged with polyglycolic acid-collagen tube with and without TrkA inhibitor (TrkAi) infiltration. Our study revealed significant improvement in motor nerve fiber regeneration and function, in assessment of vocal fold movement, myelinated nerve regeneration, compound muscle action potential, and prevention of laryngeal muscle atrophy. Retrograde labeling demonstrated fewer labeled neurons in the vagus ganglion, which confirmed reduced misdirected regeneration among motor and sensory fibers, and a change in distribution of the labeled neurons in the nucleus ambiguus. Our study demonstrated that TrkAi have a strong potential for clinical application in the treatment of RLN injury.
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Affiliation(s)
- Hiroshi Suzuki
- Department of Otolaryngology-Head and Neck Surgery, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama, 359-8513, Japan.,Department of Otolaryngology, Self-Defense Forces Central Hospital, Tokyo, Japan
| | - Koji Araki
- Department of Otolaryngology-Head and Neck Surgery, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama, 359-8513, Japan.
| | - Toshiyasu Matsui
- Department of Anatomy and Neurobiology, National Defense Medical College, Tokorozawa, Japan.,Laboratory of Veterinary Anatomy, Faculty of Veterinary Medicine, Okayama University of Science, Imabari, Japan
| | - Yuya Tanaka
- Department of Otolaryngology-Head and Neck Surgery, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama, 359-8513, Japan
| | - Kosuke Uno
- Department of Otolaryngology-Head and Neck Surgery, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama, 359-8513, Japan
| | - Masayuki Tomifuji
- Department of Otolaryngology-Head and Neck Surgery, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama, 359-8513, Japan
| | - Taku Yamashita
- Department of Otolaryngology-Head and Neck Surgery, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama, 359-8513, Japan.,Department of Otolaryngology-Head and Neck Surgery, Kitasato University School of Medicine, Sagamihara, Japan
| | - Yasushi Satoh
- Department of Biochemistry, National Defense Medical College, Tokorozawa, Japan
| | - Yasushi Kobayashi
- Department of Anatomy and Neurobiology, National Defense Medical College, Tokorozawa, Japan
| | - Akihiro Shiotani
- Department of Otolaryngology-Head and Neck Surgery, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama, 359-8513, Japan
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Mok A, Allen J, Haney MM, Deninger I, Ballenger B, Caywood V, Osman KL, Zitsch B, Hopewell BL, Thiessen A, Szewczyk M, Ohlhausen D, Newberry CI, Leary E, Lever TE. A Surgical Mouse Model for Advancing Laryngeal Nerve Regeneration Strategies. Dysphagia 2019; 35:419-437. [PMID: 31388736 DOI: 10.1007/s00455-019-10045-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 02/06/2019] [Accepted: 07/31/2019] [Indexed: 01/16/2023]
Abstract
Iatrogenic recurrent laryngeal nerve (RLN) injury is a morbid complication of anterior neck surgical procedures. Existing treatments are predominantly symptomatic, ranging from behavioral therapy to a variety of surgical approaches. Though laryngeal reinnervation strategies often provide muscle tone to the paralyzed vocal fold (VF), which may improve outcomes, there is no clinical intervention that reliably restores true physiologic VF movement. Moreover, existing interventions neglect the full cascade of molecular events that affect the entire neuromuscular pathway after RLN injury, including the intrinsic laryngeal muscles, synaptic connections within the central nervous system, and laryngeal nerve anastomoses. Systematic investigations of this pathway are essential to develop better RLN regenerative strategies. Our aim was to develop a translational mouse model for this purpose, which will permit longitudinal investigations of the pathophysiology of iatrogenic RLN injury and potential therapeutic interventions. C57BL/6J mice were divided into four surgical transection groups (unilateral RLN, n = 10; bilateral RLN, n = 2; unilateral SLN, n = 10; bilateral SLN, n = 10) and a sham surgical group (n = 10). Miniaturized transoral laryngoscopy was used to assess VF mobility over time, and swallowing was assessed using serial videofluoroscopy. Histological assays were conducted 3 months post-surgery for anatomical investigation of the larynx and laryngeal nerves. Eight additional mice underwent unilateral RLN crush injury, half of which received intraoperative vagal nerve stimulation (iVNS). These 8 mice underwent weekly transoral laryngoscopy to investigate VF recovery patterns. Unilateral RLN injury resulted in chronic VF immobility but only acute dysphagia. Bilateral RLN injury caused intraoperative asphyxiation and death. VF mobility was unaffected by SLN transection (unilateral or bilateral), and dysphagia (transient) was evident only after bilateral SLN transection. The sham surgery group retained normal VF mobility and swallow function. Mice that underwent RLN crush injury and iVNS treatment demonstrated accelerated and improved VF recovery. We successfully developed a mouse model of iatrogenic RLN injury with impaired VF mobility and swallowing function that can serve as a clinically relevant platform to develop translational neuroregenerative strategies for RLN injury.
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Affiliation(s)
- Alexis Mok
- Department of Communication Science and Disorders, University of Missouri School of Health Professions, Columbia, MO, USA
| | - Jakob Allen
- Department of Medicine, University of Missouri School of Medicine, Columbia, MO, USA
| | - Megan M Haney
- Department of Veterinary Pathobiology, University of Missouri College of Veterinary Medicine, Columbia, MO, USA
| | - Ian Deninger
- Department of Otolaryngology - Head & Neck Surgery, University of Missouri School of Medicine, Columbia, MO, USA
| | - Brayton Ballenger
- Department of Otolaryngology - Head & Neck Surgery, University of Missouri School of Medicine, Columbia, MO, USA
| | - Victoria Caywood
- Department of Otolaryngology - Head & Neck Surgery, University of Missouri School of Medicine, Columbia, MO, USA
| | - Kate L Osman
- Department of Otolaryngology - Head & Neck Surgery, University of Missouri School of Medicine, Columbia, MO, USA
| | - Bradford Zitsch
- Department of Medicine, University of Missouri School of Medicine, Columbia, MO, USA
| | - Bridget L Hopewell
- Department of Otolaryngology - Head & Neck Surgery, University of Missouri School of Medicine, Columbia, MO, USA
| | - Aaron Thiessen
- Department of Otolaryngology - Head & Neck Surgery, University of Missouri School of Medicine, Columbia, MO, USA
| | - Marlena Szewczyk
- Department of Medicine, University of Missouri School of Medicine, Columbia, MO, USA
| | - Daniel Ohlhausen
- Department of Otolaryngology - Head & Neck Surgery, University of Missouri School of Medicine, Columbia, MO, USA
| | | | - Emily Leary
- Department of Orthopedic Surgery, University of Missouri School of Medicine, Columbia, MO, USA
| | - Teresa E Lever
- Department of Otolaryngology - Head & Neck Surgery, University of Missouri School of Medicine, Columbia, MO, USA. .,One Hospital Dr. MA314, Columbia, MO, 65212, USA.
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11
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Haney MM, Hamad A, Leary E, Bunyak F, Lever TE. Automated Quantification of Vocal Fold Motion in a Recurrent Laryngeal Nerve Injury Mouse Model. Laryngoscope 2018; 129:E247-E254. [PMID: 30478924 DOI: 10.1002/lary.27609] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 08/16/2018] [Accepted: 09/17/2018] [Indexed: 11/07/2022]
Abstract
OBJECTIVES/HYPOTHESIS The goal of this study was to objectively examine vocal fold (VF) motion dynamics after iatrogenic recurrent laryngeal nerve (RLN) injury in a mouse surgical model. Furthermore, we sought to identify a method of inducing injury with a consistent recovery pattern from which we can begin to evaluate spontaneous recovery and test therapeutic interventions. STUDY DESIGN Animal model. METHODS The right RLN in C57BL/6J mice was crushed for 30 seconds using an aneurysm clip with 1.3-N closing force. Transoral laryngoscopy enabled visualization of VF movement prior to surgery, immediately post-crush, and at two endpoints: 3 days (n = 5) and 2 weeks (n = 5). VF motion was quantified with our custom motion-analysis software. At each endpoint, RLN samples were collected for transmission electron microscopy for correlation with VF motion dynamics. RESULTS Our VF tracking software permitted automated quantification of several measures of VF dynamics, such as range and frequency of motion. By 2 weeks post-injury, the frequency of VF movement on the right (injured) side equaled the left, yet range of motion only partially recovered. These objective outcome measures enabled detection of VF dysfunction that persisted at 2 weeks post-crush. Transmission electron microscopy images revealed RLN degeneration 3 days post-crush and partial regeneration at 2 weeks, consistent with functional results obtained with automated VF tracking. CONCLUSIONS Our motion-analysis software provides novel objective, quantitative, and repeatable metrics to detect and describe subtle VF dysfunction in mice that corresponds with underlying RLN degeneration and recovery. Adaptation of our tracking software for use with human patients is underway. LEVEL OF EVIDENCE NA Laryngoscope, 129:E247-E254, 2019.
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Affiliation(s)
- Megan M Haney
- Department of Veterinary Pathobiology , University of Missouri, Columbia, Missouri, U.S.A
| | - Ali Hamad
- Department of Electrical Engineering and Computer Science , University of Missouri, Columbia, Missouri, U.S.A
| | - Emily Leary
- Department of Orthopaedic Biostatistics , University of Missouri, Columbia, Missouri, U.S.A
| | - Filiz Bunyak
- Department of Electrical Engineering and Computer Science , University of Missouri, Columbia, Missouri, U.S.A
| | - Teresa E Lever
- Department of Otolaryngology-Head and Neck Surgery , University of Missouri, Columbia, Missouri, U.S.A
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12
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Ballester A, Gould F, Bond L, Stricklen B, Ohlemacher J, Gross A, DeLozier K, Buddington R, Buddington K, Danos N, German R. Maturation of the Coordination Between Respiration and Deglutition with and Without Recurrent Laryngeal Nerve Lesion in an Animal Model. Dysphagia 2018; 33:627-635. [PMID: 29476275 DOI: 10.1007/s00455-018-9881-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 02/15/2018] [Indexed: 01/02/2023]
Abstract
The timing of the occurrence of a swallow in a respiratory cycle is critical for safe swallowing, and changes with infant development. Infants with damage to the recurrent laryngeal nerve, which receives sensory information from the larynx and supplies the intrinsic muscles of the larynx, experience a significant incidence of dysphagia. Using our validated infant pig model, we determined the interaction between this nerve damage and the coordination between respiration and swallowing during postnatal development. We recorded 23 infant pigs at two ages (neonatal and older, pre-weaning) feeding on milk with barium using simultaneous high-speed videofluoroscopy and measurements of thoracic movement. With a complete linear model, we tested for changes with maturation, and whether these changes are the same in control and lesioned individuals. We found (1) the timing of swallowing and respiration coordination changes with maturation; (2) no overall effect of RLN lesion on the timing of coordination, but (3) a greater magnitude of maturational change occurs with RLN injury. We also determined that animals with no surgical intervention did not differ from animals that had surgery for marker placement and a sham procedure for nerve lesion. The coordination between respiration and swallowing changes in normal, intact individuals to provide increased airway protection prior to weaning. Further, in animals with an RLN lesion, the maturation process has a larger effect. Finally, these results suggest a high level of brainstem sensorimotor interactions with respect to these two functions.
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Affiliation(s)
- Ashley Ballester
- Department of Anatomy and Neurobiology, NEOMED, Rootstown, OH, 44272, USA.,Division of Obstetrics and Gynecology, Akron General Hospital, Akron, OH, USA
| | - François Gould
- Department of Anatomy and Neurobiology, NEOMED, Rootstown, OH, 44272, USA
| | - Laura Bond
- Department of Anatomy and Neurobiology, NEOMED, Rootstown, OH, 44272, USA
| | - Bethany Stricklen
- Department of Anatomy and Neurobiology, NEOMED, Rootstown, OH, 44272, USA
| | - Jocelyn Ohlemacher
- Department of Anatomy and Neurobiology, NEOMED, Rootstown, OH, 44272, USA
| | - Andrew Gross
- Department of Anatomy and Neurobiology, NEOMED, Rootstown, OH, 44272, USA
| | - Katherine DeLozier
- Department of Anatomy and Neurobiology, NEOMED, Rootstown, OH, 44272, USA
| | - Randall Buddington
- School of Health Studies, University of Memphis, Memphis, TN, 38152, USA
| | - Karyl Buddington
- Department of Biological Sciences, University of Memphis, Memphis, TN, 38152, USA
| | | | - Rebecca German
- Department of Anatomy and Neurobiology, NEOMED, Rootstown, OH, 44272, USA.
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13
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Uludag M, Aygun N, Kartal K, Besler E, Isgor A. Innervation of the human posterior cricoarytenoid muscle by the external branch of the superior laryngeal nerve. Head Neck 2017; 39:2200-2207. [PMID: 28815834 DOI: 10.1002/hed.24896] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Revised: 04/17/2017] [Accepted: 06/15/2017] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND The posterior cricoarytenoid muscle is the abductor muscle for the vocal cords and is innerved by the recurrent laryngeal nerve (RLN). The purpose of this study was to present our determination if the external branch of the superior laryngeal nerve (SLN) contributes to the motor innervation of the posterior cricoarytenoid muscle. METHODS We performed electromyographies (EMGs) via needle electrodes on 47 posterior cricoarytenoid muscles from 28 patients during thyroidectomy (9 lobectomies and 19 total thyroidectomies) with intraoperative neural monitoring. The RLN, vagus nerve, and external branch of the SLN were stimulated intraoperatively and the responses were evaluated by EMG. RESULTS Positive EMG responses were obtained from 16 (34%) of 47 posterior cricoarytenoid muscles after external branch of the SLN stimulation. The EMG of the posterior cricoarytenoid muscle was unilaterally positive in 8 of 19 patients (42%) with total thyroidectomy, and 2 of 19 patients (10.5%) were bilaterally positive. CONCLUSION The external branch of the SLN contributes to the ipsilateral posterior cricoarytenoid muscle innervation in one-third of the cases. This contribution is usually unilateral, but is occasionally bilateral.
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Affiliation(s)
- Mehmet Uludag
- Department of General Surgery, Sisli Hamidiye Etfal Training and Research Hospital, Istanbul, Turkey
| | - Nurcihan Aygun
- Department of General Surgery, Sisli Hamidiye Etfal Training and Research Hospital, Istanbul, Turkey
| | - Kinyas Kartal
- Department of General Surgery, Sisli Hamidiye Etfal Training and Research Hospital, Istanbul, Turkey
| | - Evren Besler
- Department of General Surgery, Sisli Hamidiye Etfal Training and Research Hospital, Istanbul, Turkey
| | - Adnan Isgor
- Department of General Surgery, Bahcesehir University Medical Faculty, Istanbul, Turkey
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14
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Hernandez-Morato I, Koss S, Sharma S, Pitman MJ. Influence of Netrin-1 on reinnervation of laryngeal muscles following recurrent laryngeal nerve injury. Neurosci Lett 2017; 653:244-249. [DOI: 10.1016/j.neulet.2017.05.033] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 04/16/2017] [Accepted: 05/16/2017] [Indexed: 10/19/2022]
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15
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Changes in neurotrophic factors of adult rat laryngeal muscles during nerve regeneration. Neuroscience 2016; 333:44-53. [DOI: 10.1016/j.neuroscience.2016.07.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 07/01/2016] [Accepted: 07/02/2016] [Indexed: 02/06/2023]
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16
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Hernandez-Morato I, Tewari I, Sharma S, Pitman MJ. Blockade of glial-derived neurotrophic factor in laryngeal muscles promotes appropriate reinnervation. Laryngoscope 2016; 126:E337-42. [DOI: 10.1002/lary.25953] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 01/14/2016] [Accepted: 02/04/2016] [Indexed: 11/08/2022]
Affiliation(s)
| | - Ishan Tewari
- Department of Anatomy and Cell Biology; New York Medical College; Valhalla New York
| | - Sansar Sharma
- Department of Anatomy and Cell Biology; New York Medical College; Valhalla New York
| | - Michael J. Pitman
- Department of Otolaryngology; New York Eye and Ear Infirmary of Mount Sinai; New York New York U.S.A
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17
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Wang B, Yuan J, Xu J, Xie J, Wang G, Dong P. Neurotrophin expression and laryngeal muscle pathophysiology following recurrent laryngeal nerve transection. Mol Med Rep 2015; 13:1234-42. [PMID: 26677138 PMCID: PMC4732864 DOI: 10.3892/mmr.2015.4684] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 11/19/2015] [Indexed: 11/05/2022] Open
Abstract
Laryngeal palsy often occurs as a result of recurrent laryngeal or vagal nerve injury during oncological surgery of the head and neck, affecting quality of life and increasing economic burden. Reinnervation following recurrent laryngeal nerve (RLN) injury is difficult despite development of techniques, such as neural anastomosis, nerve grafting and creation of a laryngeal muscle pedicle. In the present study, due to the limited availability of human nerve tissue for research, a rat model was used to investigate neurotrophin expression and laryngeal muscle pathophysiology in RLN injury. Twenty-five male Sprague-Dawley rats underwent right RLN transection with the excision of a 5-mm segment. Vocal fold movements, vocalization, histology and immunostaining were evaluated at different time-points (3, 6, 10 and 16 weeks). Although vocalization was restored, movement of the vocal fold failed to return to normal levels following RLN injury. The expression of brain‑derived neurotrophic factor and glial cell line-derived neurotrophic factor differed in the thyroarytenoid (TA) and posterior cricoarytenoid muscles. The number of axons did not increase to baseline levels over time. Furthermore, normal muscle function was unlikely with spontaneous reinnervation. During regeneration following RLN injury, differences in the expression levels of neurotrophic factors may have resulted in preferential reinnervation of the TA muscles. Data from the present study indicated that neurotrophic factors may be applied for restoring the function of the laryngeal nerve following recurrent injury.
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Affiliation(s)
- Baoxin Wang
- Department of Otolaryngology, Head and Neck Surgery, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201620, P.R. China
| | - Junjie Yuan
- Department of Orthopedics, Shanghai Fengxian District Central Hospital, Shanghai Jiao Tong University Affiliated Sixth People's Hospital South Campus, Shanghai 200011, P.R. China
| | - Jiafeng Xu
- School of Economics and Finance, Shanghai International Studies University, Shanghai 200083, P.R. China
| | - Jin Xie
- Department of Otolaryngology, Head and Neck Surgery, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201620, P.R. China
| | - Guoliang Wang
- Department of Otolaryngology, Head and Neck Surgery, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201620, P.R. China
| | - Pin Dong
- Department of Otolaryngology, Head and Neck Surgery, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201620, P.R. China
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Hernandez-Morato I, Isseroff TF, Sharma S, Pitman MJ. Differential expression of glial-derived neurotrophic factor in rat laryngeal muscles during reinnervation. Laryngoscope 2014; 124:2750-6. [DOI: 10.1002/lary.24759] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 04/26/2014] [Indexed: 11/11/2022]
Affiliation(s)
| | - Tova F. Isseroff
- Department of Otolaryngology; The New York Eye and Ear Infirmary; New York New York U.S.A
| | - Sansar Sharma
- Department of Anatomy and Cell Biology; New York Medical College; Valhalla New York
| | - Michael J. Pitman
- Department of Otolaryngology; The New York Eye and Ear Infirmary; New York New York U.S.A
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19
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Berdugo-Vega G, Arias-Gil G, Rodriguez-Niedenführ M, Davies DC, Vázquez T, Pascual-Font A. GFAP immunoreactivity within the rat nucleus ambiguus after laryngeal nerve injury. J Anat 2014; 225:492-501. [PMID: 25181319 DOI: 10.1111/joa.12231] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/24/2014] [Indexed: 11/30/2022] Open
Abstract
Changes that occur in astroglial populations of the nucleus ambiguus after recurrent (RLN) or superior (SLN) laryngeal nerve injury have hitherto not been fully characterised. In the present study, rat RLN and SLN were lesioned. After 3, 7, 14, 28 or 56 days of survival, the nucleus ambiguus was investigated by means of glial fibrillary acidic protein (GFAP) immunofluorescence or a combination of GFAP immunofluorescence and the application of retrograde tracers. GFAP immunoreactivity was significantly increased 3 days after RLN resection and it remained significantly elevated until after 28 days post injury (dpi). By 56 dpi it had returned to basal levels. In contrast, following RLN transection with repair, GFAP immunoreactivity was significantly elevated at 7 dpi and remained significantly elevated until 14 dpi. It had returned to basal levels by 28 dpi. Topographical analysis of the distribution of GFAP immunoreactivity revealed that after RLN injury, GFAP immunoreactivity was increased beyond the area of the nucleus ambiguus within which RLN motor neuron somata were located. GFAP immunoreactivity was also observed in the vicinity of neuronal somata that project into the uninjured SLN. Similarly, lesion of the SLN resulted in increased GFAP immunoreactivity around the neuronal somata projecting into it and also in the vicinity of the motor neuron somata projecting into the RLN. The increase in GFAP immunoreactivity outside of the region containing the motor neurons projecting into the injured nerve, may reflect the onset of a regenerative process attempting to compensate for impairment of one of the laryngeal nerves and may occur because of the dual innervation of the posterior cricoarytenoid muscle. This dual innervation of a very specialised muscle could provide a useful model system for studying the molecular mechanisms underlying axonal regeneration process and the results of the current study could provide the basis for studies into functional regeneration following laryngeal nerve injury, with subsequent application to humans.
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Affiliation(s)
- G Berdugo-Vega
- Department of Human Anatomy and Embryology I, School of Medicine, Complutense University of Madrid, Madrid, Spain
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20
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Zhao W, Xu W, Yang WW. Neuroregeneration in the nucleus ambiguus after recurrent laryngeal nerve avulsion in rats. Ann Otol Rhinol Laryngol 2014; 123:490-9. [PMID: 24627406 DOI: 10.1177/0003489414524170] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVES The objective was to investigate neuroregeneration, the origins of newborn cells and the proliferation of neuronal and glial cells in the nucleus ambiguus (NA) after ipsilateral recurrent laryngeal nerve (RLN) avulsion. METHODS All of the animals received a CM-Dil injection in the left lateral ventricle. Forty-five adult rats were subjected to a left RLN avulsion injury, while 9 rats were used as controls. 5-Bromo-2-deoxyuridine (BrdU) was injected intraperitoneally. Neuron quantification and immunohistochemical analysis were performed in the brain stems at different time points after RLN injury. RESULTS After RLN avulsion, CM-Dil labeled neural progenitor cells (NPCs) migrated to the ipsilateral NA and differentiated into astrocytes but not into neurons. In the NA, the neuronal cells re-expressed nestin. Only a small number of neuronal and glial cells in the NA showed BrdU immunoreactivity. CONCLUSIONS After RLN avulsion, the NPCs in the ependymal layer of the fourth ventricle or central canal are activated, migrate to the lesion in the NA and differentiate exclusively into astrocytes. The newborn neural stem cells in the NA may arise from the mature region neurons. The presence of both cell types in the NA may play a role in repairing RLN injuries.
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Hernández-Morato I, Berdugo-Vega G, Sañudo JR, Mchanwell S, Vázquez T, Valderrama-Canales FJ, Pascual-Font A. Somatotopic Changes in the Nucleus Ambiguus After Section and Regeneration of the Recurrent Laryngeal Nerve of the Rat. Anat Rec (Hoboken) 2014; 297:955-63. [DOI: 10.1002/ar.22877] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 12/10/2013] [Accepted: 12/18/2013] [Indexed: 11/06/2022]
Affiliation(s)
- Ignacio Hernández-Morato
- Department of Human Anatomy and Embryology I; School of Medicine, Complutense University of Madrid; Madrid Spain
| | - Gabriel Berdugo-Vega
- Department of Human Anatomy and Embryology I; School of Medicine, Complutense University of Madrid; Madrid Spain
| | - Jose R. Sañudo
- Department of Human Anatomy and Embryology I; School of Medicine, Complutense University of Madrid; Madrid Spain
| | - Stephen Mchanwell
- School of Medical Sciences Education Development; Newcastle University; Newcastle, NE2 4BW UK
| | - Teresa Vázquez
- Department of Human Anatomy and Embryology I; School of Medicine, Complutense University of Madrid; Madrid Spain
| | | | - Arán Pascual-Font
- Department of Human Anatomy and Embryology I; School of Medicine, Complutense University of Madrid; Madrid Spain
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