1
|
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.
Collapse
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
| |
Collapse
|
2
|
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.
Collapse
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
| |
Collapse
|
3
|
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.
Collapse
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
| |
Collapse
|
4
|
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.
Collapse
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
| |
Collapse
|
5
|
Montalbano MB, Hernández-Morato I, Tian L, Yu VX, Dodhia S, Martinez J, Pitman MJ. Recurrent Laryngeal Nerve Reinnervation in Rats Posttransection: Neurotrophic Factor Expression over Time. Otolaryngol Head Neck Surg 2019; 161:111-117. [PMID: 30776993 DOI: 10.1177/0194599819831289] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVE Recurrent laryngeal nerve (RLN) injury causes vocal fold paralysis from which functional recovery is typically absent due to nonselective reinnervation. This study investigates expression of axon guidance cues and their modulators relative to the chronology of reinnervation by examining the expression of glial-derived neurotrophic factor (GDNF), netrin 1, and laminin 111 (LAMA1) in nonpooled laryngeal muscles. This study is the first to describe the post-RLN injury expression pattern of LAMA1, a target of particular interest as it has been shown to switch netrin 1-mediated growth cone attraction to repulsion. STUDY DESIGN Animal experiment (rat model). SETTING Basic science laboratory. METHODS The right RLNs of 64 female Sprague-Dawley rats were transected, with sacrifice at 1, 3, 7, 21, 28, and 56 days postinjury (DPI). Single-animal messenger RNA was isolated from the ipsilateral posterior cricoarytenoid (PCA), lateral thyroarytenoid (LTA), and medial thyroarytenoid (MTA) for quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis. Immunostaining for LAMA1 expression was performed in the same muscles. RESULTS LAMA1 was elevated in the PCA at 3 to 56 DPI, LTA at 7 DPI, and MTA at 14 and 28 DPI. This correlates with the chronology of laryngeal reinnervation. Using a new protocol, single-animal muscle qRT-PCR possible and expression results for GDNF and netrin 1 were similar to previous pooled investigations. CONCLUSION Reliable qRT-PCR is possible with single rat laryngeal muscles. The expression of netrin 1 and LAMA1 is chronologically coordinated with muscle innervation in the LTA and MTA. This suggests that LAMA1 may influence netrin 1 to repel axons and delay LTA and MTA reinnervation.
Collapse
Affiliation(s)
- Michael B Montalbano
- 1 Columbia University College of Physicians and Surgeons, New York, New York, USA
| | | | - Likun Tian
- 1 Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Victoria X Yu
- 1 Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Sonam Dodhia
- 2 Columbia University Medical Center/New York Presbyterian, New York, New York, USA
| | - Jose Martinez
- 3 Columbia University Medical Scientist Training Program, New York, New York, USA
| | - Michael J Pitman
- 2 Columbia University Medical Center/New York Presbyterian, New York, New York, USA
| |
Collapse
|
6
|
Hernandez-Morato I, Tian L, Montalbano M, Pitman MJ. Expression of trophic factors receptors during reinnervation after recurrent laryngeal nerve injury. Laryngoscope 2019; 129:2537-2542. [PMID: 30811036 DOI: 10.1002/lary.27649] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 08/21/2018] [Accepted: 09/04/2018] [Indexed: 11/10/2022]
Abstract
OBJECTIVE An injury of the recurrent laryngeal nerve (RLN) triggers axonal regeneration but results in a poor functional recovery. Netrin-1 and glial cell-derived neurotrophic factor (GDNF) expression are up-regulated in laryngeal muscles during RLN regeneration, but the role of their receptors produced in the nucleus ambiguus is unknown. The aim of this work was to determine the timing of the production of Netrin-1 and GDNF receptors during RLN regeneration and correlate this with the previously identified timing of up-regulation of their trophic factors in the laryngeal muscles. STUDY DESIGN Laboratory experiment with rat model. METHODS The right RLN was transected and dextran amine tracer applied. At 7, 14, and 21 days postinjury (DPI), brainstems were removed and harvested. Immunostaining was performed for Netrin-1 (deleted in colorectal carcinoma [DCC], UNC5A) and GDNF receptors (rearranged during transfection [Ret], glycosylphosphatidylinositol-linked cell surface receptors [GFRα1, GFRα2, GFRα3]). The timing and type of receptor production relative to injury as well as their position in the nucleus ambiguus was analyzed. RESULTS Netrin-1 UNC5A receptors were minimal in the nucleus ambiguus during RLN regeneration. DCC, the receptor that plays an attract role, was immunopositive from 7 to 21 DPI. All GDNF receptors, except GFRα2, were clearly positive from 7 to 14 DPI. No differences of production were observed according to the position of the motor neurons in the nucleus ambiguus. CONCLUSION An injury of the RLN leads to a higher production of Netrin-1 DCC and GDNF receptors in the nucleus ambiguus. The timing of receptor production is similar to up-regulation of their trophic factors in the laryngeal muscles. LEVEL OF EVIDENCE NA. Laryngoscope, 129:2537-2542, 2019.
Collapse
Affiliation(s)
- Ignacio Hernandez-Morato
- Department of Otolaryngology-Head and Neck Surgery, Columbia University Medical Center, New York, New York, U.S.A
| | - Likun Tian
- Department of Otolaryngology-Head and Neck Surgery, Columbia University Medical Center, New York, New York, U.S.A
| | - Michael Montalbano
- Department of Otolaryngology-Head and Neck Surgery, Columbia University Medical Center, New York, New York, U.S.A
| | - Michael J Pitman
- Department of Otolaryngology-Head and Neck Surgery, Columbia University Medical Center, New York, New York, U.S.A
| |
Collapse
|
7
|
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]
|
8
|
Hernandez-Morato I, Pitman MJ, Sharma S. Muscle specific nucleus ambiguus neurons isolation and culturing. J Neurosci Methods 2016; 273:33-39. [PMID: 27475929 DOI: 10.1016/j.jneumeth.2016.07.014] [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] [Received: 02/11/2016] [Revised: 07/14/2016] [Accepted: 07/21/2016] [Indexed: 11/16/2022]
Abstract
BACKGROUND Peripheral nerve injury leads to a regenerative state. However, the reinnervation process is highly non-selective. Growing axons are often misrouted and establish aberrant synapsis to abductor or adductor muscles. Determining the complex properties of abductor and adductor motoneurons in a neuron culture, may lay the groundwork for future studies on axon guidance, leading to a clinical treatment for a selective reinnervation. NEW METHOD In the present study we develop a neuron culture protocol to isolate recurrent laryngeal nerve abductor and adductor motoneurons in order to study their unique properties. Comparison with existing methods the best period to perform the present protocol for postnatal rat cranial motoneurons isolation was determined. In addition, the method allows identification of specific motoneurons from other primary motoneurons and interneurons within brainstem. CONCLUSION The present protocol will allow investigators to perform targeted and novel studies of the mechanisms of peripheral nerve regeneration.
Collapse
Affiliation(s)
- Ignacio Hernandez-Morato
- Department of Cell Biology and Anatomy, New York Medical College, Basic Sciences Building, 15 Dana Road, Valhalla, New York 10595, United States; Department of Otolaryngology-Head and Neck Surgery, Columbia University, Medical Center, 630 West, 168th Street, New York, NY 10032, United States.
| | - Michael J Pitman
- Department of Otolaryngology-Head and Neck Surgery, Columbia University, Medical Center, 630 West, 168th Street, New York, NY 10032, United States; Department of Otolaryngology, New York Eye and Ear Infirmary of Mount Sinai, 310E, 14th Street, 6th Floor, New York Eye and Ear Infirmary, New York, NY 10003, United States
| | - Sansar Sharma
- Department of Cell Biology and Anatomy, New York Medical College, Basic Sciences Building, 15 Dana Road, Valhalla, New York 10595, United States
| |
Collapse
|
9
|
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]
|
10
|
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
| |
Collapse
|
11
|
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
| |
Collapse
|
12
|
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.
Collapse
Affiliation(s)
- G Berdugo-Vega
- Department of Human Anatomy and Embryology I, School of Medicine, Complutense University of Madrid, Madrid, Spain
| | | | | | | | | | | |
Collapse
|