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Closing the Gap between the Auditory Nerve and Cochlear Implant Electrodes: Which Neurotrophin Cocktail Performs Best for Axonal Outgrowth and Is Electrical Stimulation Beneficial? Int J Mol Sci 2023; 24:ijms24032013. [PMID: 36768339 PMCID: PMC9916558 DOI: 10.3390/ijms24032013] [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: 11/29/2022] [Revised: 01/12/2023] [Accepted: 01/14/2023] [Indexed: 01/22/2023] Open
Abstract
Neurotrophins promote neurite outgrowth of auditory neurons and may help closing the gap to cochlear implant (CI) electrodes to enhance electrical hearing. The best concentrations and mix of neurotrophins for this nerve regrowth are unknown. Whether electrical stimulation (ES) during outgrowth is beneficial or may direct axons is another open question. Auditory neuron explant cultures of distinct cochlear turns of 6-7 days old mice were cultured for four days. We tested different concentrations and combinations of BDNF and NT-3 and quantified the numbers and lengths of neurites with an advanced automated analysis. A custom-made 24-well electrical stimulator based on two bulk CIs served to test different ES strategies. Quantification of receptors trkB, trkC, p75NTR, and histological analysis helped to analyze effects. We found 25 ng/mL BDNF to perform best, especially in basal neurons, a negative influence of NT-3 in combined BDNF/NT-3 scenarios, and tonotopic changes in trk and p75NTR receptor stainings. ES largely impeded neurite outgrowth and glia ensheathment in an amplitude-dependent way. Apical neurons showed slight benefits in neurite numbers and length with ES at 10 and 500 µA. We recommend BDNF as a potent drug to enhance the man-machine interface, but CIs should be better activated after nerve regrowth.
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Ma W, Yang JW, Wang XB, Luo T, Zhou L, Lagares A, Li H, Liang Z, Liu KP, Zang CH, Li CY, Wu Z, Guo JH, Zhou XF, Li LY. Negative regulation by proBDNF signaling of peripheral neurogenesis in the sensory ganglia of adult rats. Biomed Pharmacother 2021; 144:112273. [PMID: 34700232 DOI: 10.1016/j.biopha.2021.112273] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 09/27/2021] [Accepted: 09/27/2021] [Indexed: 12/31/2022] Open
Abstract
Neurogenesis in the adult brain is well recognized and plays a critical role in the maintenance of brain function and homeostasis. However, whether neurogenesis also occurs in the adult peripheral nervous system remains unknown. Here, using sensory ganglia (dorsal root ganglia, DRGs) as a model, we show that neurogenesis also occurs in the peripheral nervous system, but in a manner different from that in the central nervous system. Satellite glial cells (SGCs) express the neuronal precursor markers Nestin, POU domain, class 4, transcription factor 1, and p75 pan-neurotrophin receptor. Following sciatic nerve injury, the suppression of endogenous proBDNF by proBDNF antibodies resulted in the transformation of proliferating SGCs into doublecortin-positive cells in the DRGs. Using purified SGCs migrating out from the DRGs, the inhibition of endogenous proBDNF promoted the conversion of SGCs into neuronal phenotypes in vitro. Our findings suggest that SGCs are neuronal precursors, and that proBDNF maintains the SGC phenotype. Furthermore, the suppression of proBDNF signaling is necessary for neuronal phenotype acquisition by SGCs. Thus, we propose that peripheral neurogenesis may occur via the direct conversion of SGCs into neurons, and that this process is negatively regulated by proBDNF.
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Affiliation(s)
- Wei Ma
- Institute of Neuroscience, Kunming Medical University, Kunming 650500, Yunnan, China
| | - Jin-Wei Yang
- Second Department of General Surgery, First People's Hospital of Yunnan Province, Kunming 650032, Yunnan, China
| | - Xian-Bin Wang
- Institute of Neuroscience, Kunming Medical University, Kunming 650500, Yunnan, China; Department of Rehabilitation Medicine, Guizhou Medical University, Guiyang 550000, Guizhou, China
| | - Tao Luo
- Institute of Neuroscience, Kunming Medical University, Kunming 650500, Yunnan, China; Medical college of Panzhihua University, Panzhihua 617000, Sichuan, China
| | - Lei Zhou
- The Key Laboratory of Stem Cell and Regenerative Medicine of Yunnan Province, Institute of Molecular and Clinical Medicine, Kunming Medical University, Kunming 650500, Yunnan, China
| | - Alfonso Lagares
- Department of Neurosurgery, Hospital 12 de Octubre, Instituto de Investigación imas12, Universidad Complutense de Madrid, Madrid, Spain
| | - Hongyun Li
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, NSW 2050, Australia
| | - Zhang Liang
- Institute of Neuroscience, Kunming Medical University, Kunming 650500, Yunnan, China
| | - Kuang-Pin Liu
- Institute of Neuroscience, Kunming Medical University, Kunming 650500, Yunnan, China
| | - Cheng-Hao Zang
- Second Department of General Surgery, First People's Hospital of Yunnan Province, Kunming 650032, Yunnan, China
| | - Chun-Yan Li
- Institute of Neuroscience, Kunming Medical University, Kunming 650500, Yunnan, China
| | - Zhen Wu
- Second Department of General Surgery, First People's Hospital of Yunnan Province, Kunming 650032, Yunnan, China
| | - Jian-Hui Guo
- Second Department of General Surgery, First People's Hospital of Yunnan Province, Kunming 650032, Yunnan, China.
| | - Xin-Fu Zhou
- School of Pharmacy and Medical Sciences, Sansom Institute, Faculty of Health Sciences, University of South Australia, Adelaide, SA 5000, Australia.
| | - Li-Yan Li
- Institute of Neuroscience, Kunming Medical University, Kunming 650500, Yunnan, China.
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Lu Y, Shan Q, Ling M, Ni XA, Mao SS, Yu B, Cao QQ. Identification of key genes involved in axon regeneration and Wallerian degeneration by weighted gene co-expression network analysis. Neural Regen Res 2021; 17:911-919. [PMID: 34472493 PMCID: PMC8530115 DOI: 10.4103/1673-5374.322473] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Peripheral nerve injury repair requires a certain degree of cooperation between axon regeneration and Wallerian degeneration. Therefore, investigating how axon regeneration and degeneration work together to repair peripheral nerve injury may uncover the molecular mechanisms and signal cascades underlying peripheral nerve repair and provide potential strategies for improving the low axon regeneration capacity of the central nervous system. In this study, we applied weighted gene co-expression network analysis to identify differentially expressed genes in proximal and distal sciatic nerve segments from rats with sciatic nerve injury. We identified 31 and 15 co-expression modules from the proximal and distal sciatic nerve segments, respectively. Functional enrichment analysis revealed that the differentially expressed genes in proximal modules promoted regeneration, while the differentially expressed genes in distal modules promoted neurodegeneration. Next, we constructed hub gene networks for selected modules and identified a key hub gene, Kif22, which was up-regulated in both nerve segments. In vitro experiments confirmed that Kif22 knockdown inhibited proliferation and migration of Schwann cells by modulating the activity of the extracellular signal-regulated kinase signaling pathway. Collectively, our findings provide a comparative framework of gene modules that are co-expressed in injured proximal and distal sciatic nerve segments, and identify Kif22 as a potential therapeutic target for promoting peripheral nerve injury repair via Schwann cell proliferation and migration. All animal experiments were approved by the Institutional Animal Ethics Committee of Nantong University, China (approval No. S20210322-008) on March 22, 2021.
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Affiliation(s)
- Yan Lu
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu Province, China
| | - Qi Shan
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu Province, China
| | - Mei Ling
- School of Life Sciences, Nantong University, Nantong, Jiangsu Province, China
| | - Xi-An Ni
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu Province, China
| | - Su-Su Mao
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu Province, China
| | - Bin Yu
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu Province, China
| | - Qian-Qian Cao
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu Province, China
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The Delayed-Onset Mechanical Pain Behavior Induced by Infant Peripheral Nerve Injury Is Accompanied by Sympathetic Sprouting in the Dorsal Root Ganglion. BIOMED RESEARCH INTERNATIONAL 2020; 2020:9165475. [PMID: 32626770 PMCID: PMC7315272 DOI: 10.1155/2020/9165475] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 05/02/2020] [Accepted: 05/19/2020] [Indexed: 11/19/2022]
Abstract
Background Sympathetic sprouting in the dorsal root ganglion (DRG) following nerve injuries had been proved to induce adult neuropathic pain. However, it is unclear whether the abnormal sprouting occurs in infant nerve injury. Methods L5 spinal nerve ligation (SNL) or sham surgery was performed on adult rats and 10-day-old pups, and mechanical thresholds and heat hyperalgesia were analyzed on 3, 7, 14, 28, and 56 postoperative days. Tyrosine hydroxylase-labeled sympathetic fibers were observed at each time point, and 2 neurotrophin receptors (p75NTR and TrkA) were identified to explore the mechanisms of sympathetic sprouting. Results Adult rats rapidly developed mechanical and heat hyperalgesia from postoperative day 3, with concurrent sympathetic sprouting in DRG. In contrast, the pup rats did not show a significantly lower mechanical threshold until postoperative day 28, at which time the sympathetic sprouting became evident in the DRG. No heat hyperalgesia was presented in pup rats at any time point. There was a late expression of glial p75NTR in DRG of pups from postoperative day 28, which was parallel to the occurrence of sympathetic sprouting. The expression of TrkA did not show such a postoperative syncing change. Conclusion The delayed-onset mechanical allodynia in the infant nerve lesion was accompanied with parallel sympathetic sprouting in DRG. The late parallel expression of glial p75NTR injury may play an essential role in this process, which provides novel insight into the treatment of delayed adolescent neuropathic pain.
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Effect of Induction Time on the Proliferation and Differentiation of Induced Schwann-Like Cells from Adipose-Derived Stem Cells. Cell Mol Neurobiol 2020; 40:1105-1116. [DOI: 10.1007/s10571-020-00795-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2019] [Accepted: 01/18/2020] [Indexed: 12/15/2022]
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Li R, Li D, Wu C, Ye L, Wu Y, Yuan Y, Yang S, Xie L, Mao Y, Jiang T, Li Y, Wang J, Zhang H, Li X, Xiao J. Nerve growth factor activates autophagy in Schwann cells to enhance myelin debris clearance and to expedite nerve regeneration. Theranostics 2020; 10:1649-1677. [PMID: 32042328 PMCID: PMC6993217 DOI: 10.7150/thno.40919] [Citation(s) in RCA: 116] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2019] [Accepted: 10/27/2019] [Indexed: 12/12/2022] Open
Abstract
Rationale: Autophagy in Schwann cells (SCs) is crucial for myelin debris degradation and clearance following peripheral nerve injury (PNI). Nerve growth factor (NGF) plays an important role in reconstructing peripheral nerve fibers and promoting axonal regeneration. However, it remains unclear if NGF effect in enhancing nerve regeneration is mediated through autophagic clearance of myelin debris in SCs. Methods: In vivo, free NGF solution plus with/without pharmacological inhibitors were administered to a rat sciatic nerve crush injury model. In vitro, the primary Schwann cells (SCs) and its cell line were cultured in normal medium containing NGF, their capable of swallowing or clearing degenerated myelin was evaluated through supplement of homogenized myelin fractions. Results: Administration of exogenous NGF could activate autophagy in dedifferentiated SCs, accelerate myelin debris clearance and phagocytosis, as well as promote axon and myelin regeneration at early stage of PNI. These NGF effects were effectively blocked by autophagy inhibitors. In addition, inhibition of the p75 kD neurotrophin receptor (p75NTR) signal or inactivation of the AMP-activated protein kinase (AMPK) also inhibited the NGF effect as well. Conclusions: NGF effect on promoting early nerve regeneration is closely associated with its accelerating autophagic clearance of myelin debris in SCs, which probably regulated by the p75NTR/AMPK/mTOR axis. Our studies thus provide strong support that NGF may serve as a powerful pharmacological therapy for peripheral nerve injuries.
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The ProNGF/p75NTR pathway induces tau pathology and is a therapeutic target for FTLD-tau. Mol Psychiatry 2018; 23:1813-1824. [PMID: 29867188 DOI: 10.1038/s41380-018-0071-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2017] [Revised: 01/26/2018] [Accepted: 03/26/2018] [Indexed: 11/09/2022]
Abstract
Tau pathology is characterized as a form of frontotemporal lobar degeneration (FTLD) known as FTLD-tau. The underlying pathogenic mechanisms are not known and no therapeutic interventions are currently available. Here, we report that the neurotrophin receptor p75NTR plays a critical role in the pathogenesis of FTLD-tau. The expression of p75NTR and the precursor of nerve growth factor (proNGF) were increased in the brains of FTLD-tau patients and mice (P301L transgenic). ProNGF-induced tau phosphorylation via p75NTR in vitro, which was associated with the AKT/glycogen synthase kinase (GSK)3β pathway. Genetic reduction of p75NTR in P301L mice rescued the memory deficits, alleviated tau hyperphosphorylation and restored the activity of the AKT/GSK3β pathway. Treatment of the P301L mice with the soluble p75NTR extracellular domain (p75ECD-Fc), which can antagonize neurotoxic ligands of p75NTR, effectively improved memory behavior and suppressed tau pathology. This suggests that p75NTR plays a crucial role in tau paGSKthology and represents a potential druggable target for FTLD-tau and related tauopathies.
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p75NTR and TROY: Uncharted Roles of Nogo Receptor Complex in Experimental Autoimmune Encephalomyelitis. Mol Neurobiol 2018; 55:6329-6336. [PMID: 29294247 DOI: 10.1007/s12035-017-0841-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 12/14/2017] [Indexed: 12/11/2022]
Abstract
Multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), have been on the forefront of drug discovery for most of the myelin inhibitory molecules implicated in axonal regenerative process. Nogo-A along with its putative receptor NgR and co-receptor LINGO-1 has paved the way for the production of pharmaceutical agents such as monoclonal antibodies, which are already put into handful of clinical trials. On the other side, little progress has been made towards clarifying the role of neurotrophin receptor p75 (p75NTR) and TROY in disease progression, other key players of the Nogo receptor complex. Previous work of our lab has shown that their exact location and type of expression is harmonized in a phase-dependent manner. Here, in this review, we outline their façade in normal and diseased central nervous system (CNS) and suggest a role for p75NTR in chronic axonal regeneration whereas TROY in acute inflammation of EAE intercourse.
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Gonçalves NP, Vægter CB, Andersen H, Østergaard L, Calcutt NA, Jensen TS. Schwann cell interactions with axons and microvessels in diabetic neuropathy. Nat Rev Neurol 2017; 13:135-147. [PMID: 28134254 DOI: 10.1038/nrneurol.2016.201] [Citation(s) in RCA: 168] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The prevalence of diabetes worldwide is at pandemic levels, with the number of patients increasing by 5% annually. The most common complication of diabetes is peripheral neuropathy, which has a prevalence as high as 50% and is characterized by damage to neurons, Schwann cells and blood vessels within the nerve. The pathogenic mechanisms of diabetic neuropathy remain poorly understood, impeding the development of targeted therapies to treat nerve degeneration and its most disruptive consequences of sensory loss and neuropathic pain. Involvement of Schwann cells has long been proposed, and new research techniques are beginning to unravel a complex interplay between these cells, axons and microvessels that is compromised during the development of diabetic neuropathy. In this Review, we discuss the evolving concept of Schwannopathy as an integral factor in the pathogenesis of diabetic neuropathy, and how disruption of the interactions between Schwann cells, axons and microvessels contribute to the disease.
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Affiliation(s)
- Nádia P Gonçalves
- The International Diabetic Neuropathy Consortium (IDNC), Aarhus University, Nørrebrogade, 8000 Aarhus C, Denmark
| | - Christian B Vægter
- Danish Research Institute of Translational Neuroscience DANDRITE, Nordic-EMBL Partnership, Department of Biomedicine, Aarhus University, Ole Worms Alle 3, 8000 Aarhus C, Denmark
| | - Henning Andersen
- Department of Neurology, Danish Pain Research Center and IDNC, Aarhus University Hospital, Nørrebrogade, 8000 Aarhus C, Denmark
| | - Leif Østergaard
- Department of Neuroradiology and Center for Functionally Integrative Neuroscience, Aarhus University Hospital, Nørrebrogade, 8000 Aarhus C, Denmark
| | - Nigel A Calcutt
- Department of Pathology, University of California San Diego, Gilman Drive, La Jolla, California 92093, USA
| | - Troels S Jensen
- Department of Neurology, Danish Pain Research Center and IDNC, Aarhus University Hospital, Nørrebrogade, 8000 Aarhus C, Denmark
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Theotokis P, Touloumi O, Lagoudaki R, Nousiopoulou E, Kesidou E, Siafis S, Tselios T, Lourbopoulos A, Karacostas D, Grigoriadis N, Simeonidou C. Nogo receptor complex expression dynamics in the inflammatory foci of central nervous system experimental autoimmune demyelination. J Neuroinflammation 2016; 13:265. [PMID: 27724971 PMCID: PMC5057208 DOI: 10.1186/s12974-016-0730-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Accepted: 09/22/2016] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Nogo-A and its putative receptor NgR are considered to be among the inhibitors of axonal regeneration in the CNS. However, few studies so far have addressed the issue of local NgR complex multilateral localization within inflammation in an MS mouse model of autoimmune demyelination. METHODS Chronic experimental autoimmune encephalomyelitis (EAE) was induced in C57BL/6 mice. Analyses were performed on acute (days 18-22) and chronic (day 50) time points and compared to controls. The temporal and spatial expression of the Nogo receptor complex (NgR and coreceptors) was studied at the spinal cord using epifluorescent and confocal microscopy or real-time PCR. Data are expressed as cells/mm2, as mean % ± SEM, or as arbitrary units of integrated density. RESULTS Animals developed a moderate to severe EAE without mortality, followed by a progressive, chronic clinical course. NgR complex spatial expression varied during the main time points of EAE. NgR with coreceptors LINGO-1 and TROY was increased in the spinal cord in the acute phase whereas LINGO-1 and p75 signal seemed to be dominant in the chronic phase, respectively. NgR was detected on gray matter NeuN+ neurons of the spinal cord, within the white matter inflammatory foci (14.2 ± 4.3 % NgR+ inflammatory cells), and found to be colocalized with GAP-43+ axonal growth cones while no β-TubIII+, SMI-32+, or APP+ axons were found as NgR+. Among the NgR+ inflammatory cells, 75.6 ± 9.0 % were microglial/macrophages (lectin+), 49.6 ± 14.2 % expressed CD68 (phagocytic ED1+ cells), and no cells were Mac-3+. Of these macrophages/monocytes, only Arginase-1+/NgR+ but not iNOS+/NgR+ were present in lesions both in acute and chronic phases. CONCLUSIONS Our data describe in detail the expression of the Nogo receptor complex within the autoimmune inflammatory foci and suggest a possible immune action for NgR apart from the established inhibitory one on axonal growth. Its expression by inflammatory macrophages/monocytes could signify a possible role of these cells on axonal guidance and clearance of the lesioned area during inflammatory demyelination.
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MESH Headings
- Animals
- Antigens, Differentiation/metabolism
- Arginase/metabolism
- Central Nervous System/metabolism
- Central Nervous System/pathology
- Disease Models, Animal
- Encephalomyelitis, Autoimmune, Experimental/chemically induced
- Encephalomyelitis, Autoimmune, Experimental/complications
- Encephalomyelitis, Autoimmune, Experimental/immunology
- Encephalomyelitis, Autoimmune, Experimental/pathology
- Female
- Freund's Adjuvant/immunology
- Freund's Adjuvant/toxicity
- Gene Expression Regulation/drug effects
- Gene Expression Regulation/immunology
- Mice
- Mice, Inbred C57BL
- Myelin-Oligodendrocyte Glycoprotein/immunology
- Myelin-Oligodendrocyte Glycoprotein/toxicity
- Nerve Tissue Proteins/metabolism
- Nogo Proteins/genetics
- Nogo Proteins/metabolism
- Nogo Receptors/genetics
- Nogo Receptors/metabolism
- Peptide Fragments/immunology
- Peptide Fragments/toxicity
- Receptors, Nerve Growth Factor/genetics
- Receptors, Nerve Growth Factor/metabolism
- Receptors, Tumor Necrosis Factor/genetics
- Receptors, Tumor Necrosis Factor/metabolism
- Signal Transduction/drug effects
- Signal Transduction/immunology
- Signal Transduction/physiology
- Statistics, Nonparametric
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Affiliation(s)
- Paschalis Theotokis
- B’ Department of Neurology, Laboratory of Experimental Neurology and Neuroimmunology, AHEPA University Hospital, Aristotle University of Thessaloniki, Stilponos Kiriakides str. 1, 546 36 Thessaloniki, Central Macedonia Greece
| | - Olga Touloumi
- B’ Department of Neurology, Laboratory of Experimental Neurology and Neuroimmunology, AHEPA University Hospital, Aristotle University of Thessaloniki, Stilponos Kiriakides str. 1, 546 36 Thessaloniki, Central Macedonia Greece
| | - Roza Lagoudaki
- B’ Department of Neurology, Laboratory of Experimental Neurology and Neuroimmunology, AHEPA University Hospital, Aristotle University of Thessaloniki, Stilponos Kiriakides str. 1, 546 36 Thessaloniki, Central Macedonia Greece
| | - Evangelia Nousiopoulou
- B’ Department of Neurology, Laboratory of Experimental Neurology and Neuroimmunology, AHEPA University Hospital, Aristotle University of Thessaloniki, Stilponos Kiriakides str. 1, 546 36 Thessaloniki, Central Macedonia Greece
| | - Evangelia Kesidou
- B’ Department of Neurology, Laboratory of Experimental Neurology and Neuroimmunology, AHEPA University Hospital, Aristotle University of Thessaloniki, Stilponos Kiriakides str. 1, 546 36 Thessaloniki, Central Macedonia Greece
| | - Spyridon Siafis
- B’ Department of Neurology, Laboratory of Experimental Neurology and Neuroimmunology, AHEPA University Hospital, Aristotle University of Thessaloniki, Stilponos Kiriakides str. 1, 546 36 Thessaloniki, Central Macedonia Greece
| | - Theodoros Tselios
- Department of Chemistry, University of Patras, Rion, 265 04 Patras, Greece
| | - Athanasios Lourbopoulos
- B’ Department of Neurology, Laboratory of Experimental Neurology and Neuroimmunology, AHEPA University Hospital, Aristotle University of Thessaloniki, Stilponos Kiriakides str. 1, 546 36 Thessaloniki, Central Macedonia Greece
- Institute for Stroke and Dementia Research (ISD), Feodor-Lynen-Strasse 17, 81377 Munich, Germany
| | - Dimitrios Karacostas
- B’ Department of Neurology, Laboratory of Experimental Neurology and Neuroimmunology, AHEPA University Hospital, Aristotle University of Thessaloniki, Stilponos Kiriakides str. 1, 546 36 Thessaloniki, Central Macedonia Greece
| | - Nikolaos Grigoriadis
- B’ Department of Neurology, Laboratory of Experimental Neurology and Neuroimmunology, AHEPA University Hospital, Aristotle University of Thessaloniki, Stilponos Kiriakides str. 1, 546 36 Thessaloniki, Central Macedonia Greece
| | - Constantina Simeonidou
- Department of Experimental Physiology, Faculty of Medicine, Aristotle University of Thessaloniki, 546 36 Thessaloniki, Central Macedonia Greece
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Oprych K, Cotfas D, Choi D. Common olfactory ensheathing glial markers in the developing human olfactory system. Brain Struct Funct 2016; 222:1877-1895. [PMID: 27718014 PMCID: PMC5406434 DOI: 10.1007/s00429-016-1313-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 09/14/2016] [Indexed: 12/14/2022]
Abstract
The in situ immunocytochemical properties of olfactory ensheathing cells (OECs) have been well studied in several small to medium sized animal models including rats, mice, guinea pigs, cats and canines. However, we know very little about the antigenic characteristics of OECs in situ within the adult and developing human olfactory bulb and nerve roots. To address this gap in knowledge we undertook an immunocytochemical analysis of the 11–19 pcw human foetal olfactory system. Human foetal OECs in situ possessed important differences compared to rodents in the expression of key surface markers. P75NTR was not observed in OECs but was strongly expressed by human foetal Schwann cells and perineurial olfactory nerve fibroblasts surrounding OECs. We define OECs throughout the 11–19 pcw human olfactory system as S100/vimentin/SOX10+ with low expression of GFAP. Our results suggest that P75NTR is a robust marker that could be utilised with cell sorting techniques to generate enriched OEC cultures by first removing P75NTR expressing Schwann cells and fibroblasts, and subsequently to isolate OECs after P75NTR upregulation in vitro. O4 and PSA-NCAM were not found to be suitable surface antigens for OEC purification owing to their ambiguous and heterogeneous expression. Our results highlight the importance of corroborating cell markers when translating cell therapies from animal models to the clinic.
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Affiliation(s)
- Karen Oprych
- Department of Brain, Repair and Rehabilitation, Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, UK.
| | - Daniel Cotfas
- Department of Brain, Repair and Rehabilitation, Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, UK
| | - David Choi
- Department of Brain, Repair and Rehabilitation, Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, UK.,National Hospital for Neurology and Neurosurgery, Queen Square, London, WC1N 3BG, UK
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12
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Wang L, Wang J, Ma D, Taylor JS, Chan SO. Isoform-specific localization of Nogo protein in the optic pathway of mouse embryos. J Comp Neurol 2016; 524:2322-34. [DOI: 10.1002/cne.23953] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Revised: 12/23/2015] [Accepted: 12/28/2015] [Indexed: 02/04/2023]
Affiliation(s)
- Liqing Wang
- Department of Neurology; the Third Affiliated Hospital of Sun Yat-Sen University; Guangzhou Guangdong 510630 China
| | - Jun Wang
- Department of Anatomy and Embryology; School of Basic Medical Sciences, Peking University; Beijing 100191 China
| | - Ding Ma
- School of Biomedical Sciences; The Chinese University of Hong Kong, Shatin, N.T; Hong Kong China
| | - Jeremy S.H. Taylor
- Department of Physiology; Anatomy and Genetics, Le Gros Clark Building, Oxford OX1 3QX; United Kingdom
| | - Sun-On Chan
- School of Biomedical Sciences; The Chinese University of Hong Kong, Shatin, N.T; Hong Kong China
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13
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Reactive Transformation and Increased BDNF Signaling by Hippocampal Astrocytes in Response to MK-801. PLoS One 2015; 10:e0145651. [PMID: 26700309 PMCID: PMC4689377 DOI: 10.1371/journal.pone.0145651] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 12/07/2015] [Indexed: 11/26/2022] Open
Abstract
MK-801, also known as dizocilpine, is a noncompetitive N-methyl-D-aspartic acid (NMDA) receptor antagonist that induces schizophrenia-like symptoms. While astrocytes have been implicated in the pathophysiology of psychiatric disorders, including schizophrenia, astrocytic responses to MK-801 and their significance to schizotypic symptoms are unclear. Changes in the expression levels of glial fibrillary acid protein (GFAP), a marker of astrocyte activation in response to a variety of pathogenic stimuli, were examined in the hippocampus of rats treated with the repeated MK-801 injection (0.5 mg/10ml/kg body weight for 6 days) and in primary cultured hippocampal astrocytes incubated with MK-801 (5 or 20 μM for 24 h). Moreover, the expression levels of BDNF and its receptors TrkB and p75 were examined in MK-801-treated astrocyte cultures. MK-801 treatment enhanced GFAP expression in the rat hippocampus and also increased the levels of GFAP protein and mRNA in hippocampal astrocytes in vitro. Treatment of cultured hippocampal astrocytes with MK-801 enhanced protein and mRNA levels of BDNF, TrkB, and p75. Collectively, our results suggest that hippocampal astrocytes may contribute to the pathophysiology of schizophrenia symptoms associated with NMDA receptor hypofunction by reactive transformation and altered BDNF signaling.
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Differential levels of p75NTR ectodomain in CSF and blood in patients with Alzheimer's disease: a novel diagnostic marker. Transl Psychiatry 2015; 5:e650. [PMID: 26440538 PMCID: PMC4930124 DOI: 10.1038/tp.2015.146] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Revised: 07/20/2015] [Accepted: 07/29/2015] [Indexed: 01/21/2023] Open
Abstract
Alzheimer's disease (AD) is the primary cause of dementia in the elderly. The ectodomain of p75 neurotrophin receptor (p75NTR-ECD) has been suggested to play important roles in regulating beta-amyloid (Aβ) deposition and in protecting neurons from the toxicity of soluble Aβ. However, whether and how the serum and cerebrospinal fluid (CSF) levels of p75NTR-ECD change in patients with AD are not well documented. In the present study, we determined the concentrations of serum p75NTR-ECD in an AD group, a Parkinson disease group and a stroke group, as well as in a group of elderly controls without neurological disorders (EC). We also determined the levels of CSF p75NTR-ECD in a subset of the AD and EC groups. Our data showed that a distinct p75NTR-ECD profile characterized by a decreased CSF level and an increased serum level was present concomitantly with AD patients but not with other diseases. p75NTR-ECD levels in both the serum and CSF were strongly correlated with Mini-Mental State Examination (MMSE) scores and showed sound differential diagnostic value for AD. Moreover, when combining CSF Aβ42, CSF Aβ42/40, CSF ptau181 or CSF ptau181/Aβ42 with CSF p75NTR-ECD, the area under the receiver operating characteristic curve (AUC) and diagnostic accuracies improved. These findings indicate that p75NTR-ECD can serve as a specific biomarker for AD and the determination of serum and CSF p75NTR-ECD levels is likely to be helpful in monitoring AD progression.
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Siebert JR, Eade AM, Osterhout DJ. Biomaterial Approaches to Enhancing Neurorestoration after Spinal Cord Injury: Strategies for Overcoming Inherent Biological Obstacles. BIOMED RESEARCH INTERNATIONAL 2015; 2015:752572. [PMID: 26491685 PMCID: PMC4600545 DOI: 10.1155/2015/752572] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 07/22/2015] [Indexed: 01/14/2023]
Abstract
While advances in technology and medicine have improved both longevity and quality of life in patients living with a spinal cord injury, restoration of full motor function is not often achieved. This is due to the failure of repair and regeneration of neuronal connections in the spinal cord after injury. In this review, the complicated nature of spinal cord injury is described, noting the numerous cellular and molecular events that occur in the central nervous system following a traumatic lesion. In short, postinjury tissue changes create a complex and dynamic environment that is highly inhibitory to the process of neural regeneration. Strategies for repair are outlined with a particular focus on the important role of biomaterials in designing a therapeutic treatment that can overcome this inhibitory environment. The importance of considering the inherent biological response of the central nervous system to both injury and subsequent therapeutic interventions is highlighted as a key consideration for all attempts at improving functional recovery.
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Affiliation(s)
- Justin R. Siebert
- Lake Erie College of Osteopathic Medicine at Seton Hill, Greensburg, PA 15601, USA
| | - Amber M. Eade
- Lake Erie College of Osteopathic Medicine at Seton Hill, Greensburg, PA 15601, USA
| | - Donna J. Osterhout
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY 13210, USA
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16
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Meeker RB, Williams KS. The p75 neurotrophin receptor: at the crossroad of neural repair and death. Neural Regen Res 2015; 10:721-5. [PMID: 26109945 PMCID: PMC4468762 DOI: 10.4103/1673-5374.156967] [Citation(s) in RCA: 114] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/07/2015] [Indexed: 12/14/2022] Open
Abstract
The strong repair and pro-survival functions of neurotrophins at their primary receptors, TrkA, TrkB and TrkC, have made them attractive candidates for treatment of nervous system injury and disease. However, difficulties with the clinical implementation of neurotrophin therapies have prompted the search for treatments that are stable, easier to deliver and allow more precise regulation of neurotrophin actions. Recently, the p75 neurotrophin receptor (p75NTR) has emerged as a potential target for pharmacological control of neurotrophin activity, supported in part by studies demonstrating 1) regulation of neural plasticity in the mature nervous system, 2) promotion of adult neurogenesis and 3) increased expression in neurons, macrophages, microglia, astrocytes and/or Schwann cells in response to injury and neurodegenerative diseases. Although the receptor has no intrinsic catalytic activity it interacts with and modulates the function of TrkA, TrkB, and TrkC, as well as sortilin and the Nogo receptor. This provides substantial cellular and molecular diversity for regulation of neuron survival, neurogenesis, immune responses and processes that support neural function. Upregulation of the p75NTR under pathological conditions places the receptor in a key position to control numerous processes necessary for nervous system recovery. Support for this possibility has come from recent studies showing that small, non-peptide p75NTR ligands can selectively modify pro-survival and repair functions. While a great deal remains to be discovered about the wide ranging functions of the p75NTR, studies summarized in this review highlight the immense potential for development of novel neuroprotective and neurorestorative therapies.
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Affiliation(s)
- Rick B Meeker
- Department of Neurology, University of North Carolina, Chapel Hill, NC, USA
| | - Kimberly S Williams
- Curriculum in Neurobiology, University of North Carolina, Chapel Hill, NC, USA
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Freidin M, Asche-Godin S, Abrams CK. Gene expression profiling studies in regenerating nerves in a mouse model for CMT1X: uninjured Cx32-knockout peripheral nerves display expression profile of injured wild type nerves. Exp Neurol 2015; 263:339-49. [PMID: 25447941 PMCID: PMC4262134 DOI: 10.1016/j.expneurol.2014.10.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 10/13/2014] [Accepted: 10/18/2014] [Indexed: 11/20/2022]
Abstract
X-linked Charcot-Marie-Tooth disease (CMT1X) is an inherited peripheral neuropathy caused by mutations in GJB1, the human gene for Connexin32 (Cx32). This present study uses Ilumina Ref8-v2 BeadArray to examine the expression profiles of injured and uninjured sciatic nerves at 5, 7, and 14 days post-crush injury (dpi) from Wild Type (WT) and Cx32-knockout (Cx32KO) mice to identify the genes and signaling pathways that are dysregulated in the absence of Schwann cell Cx32. Given the assumption that loss of Schwann cell Cx32 disrupts the regeneration and maintenance of myelinated nerve leading to a demyelinating neuropathy in CMT1X, we initially hypothesized that nerve crush injury would result in significant increases in differential gene expression in Cx32KO mice relative to WT nerves. However, microarray analysis revealed a striking collapse in the number of differentially expressed genes at 5 and 7 dpi in Cx32KO nerves relative to WT, while uninjured and 14 dpi time points showed large numbers of differentially regulated genes. Further comparisons within each genotype showed limited changes in Cx32KO gene expression following crush injury when compared to uninjured Cx32KO nerves. By contrast, WT nerves exhibited robust changes in gene expression at 5 and 7 dpi with no significant differences in gene expression by 14dpi relative to uninjured WT nerve samples. Taken together, these data suggest that the gene expression profile in uninjured Cx32KO sciatic nerve strongly resembles that of a WT nerve following injury and that loss of Schwann cell Cx32 leads to a basal state of gene expression similar to that of an injured WT nerve. These findings support a role for Cx32 in non-myelinating and regenerating populations of Schwann cells in normal axonal maintenance in re-myelination, and regeneration of peripheral nerve following injury. Disruption of Schwann cell-axonal communication in CMT1X may cause dysregulation of signaling pathways that are essential for the maintenance of intact myelinated peripheral nerves and to establish the necessary conditions for successful regeneration and remyelination following nerve injury.
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Affiliation(s)
- Mona Freidin
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Samantha Asche-Godin
- Department of Neurology, State University of New York, Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Charles K Abrams
- Department of Neurology, State University of New York, Downstate Medical Center, Brooklyn, NY 11203, USA
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Ameliorative Effects of p75NTR-ED-Fc on Axonal Regeneration and Functional Recovery in Spinal Cord-Injured Rats. Mol Neurobiol 2014; 52:1821-1834. [DOI: 10.1007/s12035-014-8972-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2014] [Accepted: 10/29/2014] [Indexed: 11/25/2022]
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19
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Qu Q, Chen J, Wang Y, Gui W, Wang L, Fan Z, Jiang T. Structural characterization of the self-association of the death domain of p75(NTR.). PLoS One 2013; 8:e57839. [PMID: 23472109 PMCID: PMC3589453 DOI: 10.1371/journal.pone.0057839] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Accepted: 01/26/2013] [Indexed: 01/19/2023] Open
Abstract
The neurotrophin receptor p75(NTR) conveys multiple signals via its intracellular death domain. However, how the death domain is activated and interacts with downstream adaptors remains unclear. Here, we report two crystal structures of the p75(NTR) death domain in the form of a non-covalent asymmetric dimer and a Cys379-Cys379 disulfide bond linked symmetric dimer, respectively. These two dimer arrangements have not previously been observed in other death domain-containing proteins. Further analysis shows that both the Cys379-Cys379 disulfide linked and non-covalent full-length p75(NTR) dimers are present on the cell surface. These observations suggest that various oligomers may exist simultaneously on the cell surface, and that p75(NTR) activation and signalling may be modulated by neurotrophins or other factors via inducing a shift of the equilibrium between different oligomeric states.
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Affiliation(s)
- Qianhui Qu
- National Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- Graduate University of Chinese Academy of Sciences, Beijing, China
| | - Jun Chen
- Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- Graduate University of Chinese Academy of Sciences, Beijing, China
| | - Yizhi Wang
- National Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- Graduate University of Chinese Academy of Sciences, Beijing, China
| | - Wenjun Gui
- National Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- Graduate University of Chinese Academy of Sciences, Beijing, China
| | - Li Wang
- Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- Graduate University of Chinese Academy of Sciences, Beijing, China
| | - Zusen Fan
- Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Tao Jiang
- National Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- * E-mail:
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20
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Sun Y, Lim Y, Li F, Liu S, Lu JJ, Haberberger R, Zhong JH, Zhou XF. ProBDNF collapses neurite outgrowth of primary neurons by activating RhoA. PLoS One 2012; 7:e35883. [PMID: 22558255 PMCID: PMC3338794 DOI: 10.1371/journal.pone.0035883] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 03/23/2012] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Neurons extend their dendrites and axons to build functional neural circuits, which are regulated by both positive and negative signals during development. Brain-derived neurotrophic factor (BDNF) is a positive regulator for neurite outgrowth and neuronal survival but the functions of its precursor (proBDNF) are less characterized. METHODOLOGY/PRINCIPAL FINDINGS Here we show that proBDNF collapses neurite outgrowth in murine dorsal root ganglion (DRG) neurons and cortical neurons by activating RhoA via the p75 neurotrophin receptor (p75NTR). We demonstrated that the receptor proteins for proBDNF, p75NTR and sortilin, were highly expressed in cultured DRG or cortical neurons. ProBDNF caused a dramatic neurite collapse in a dose-dependent manner and this effect was about 500 fold more potent than myelin-associated glycoprotein. Neutralization of endogenous proBDNF by using antibodies enhanced neurite outgrowth in vitro and in vivo, but this effect was lost in p75NTR(-/-) mice. The neurite outgrowth of cortical neurons from p75NTR deficient (p75NTR(-/-)) mice was insensitive to proBDNF. There was a time-dependent reduction of length and number of filopodia in response to proBDNF which was accompanied with a polarized RhoA activation in growth cones. Moreover, proBDNF treatment of cortical neurons resulted in a time-dependent activation of RhoA but not Cdc42 and the effect was absent in p75NTR(-/-) neurons. Rho kinase (ROCK) and the collapsin response mediator protein-2 (CRMP-2) were also involved in the proBDNF action. CONCLUSIONS proBDNF has an opposing role in neurite outgrowth to that of mature BDNF. Our observations suggest that proBDNF collapses neurites outgrowth and filopodial growth cones by activating RhoA through the p75NTR signaling pathway.
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MESH Headings
- Adaptor Proteins, Vesicular Transport/genetics
- Adaptor Proteins, Vesicular Transport/metabolism
- Animals
- Antibodies/pharmacology
- Brain-Derived Neurotrophic Factor/antagonists & inhibitors
- Brain-Derived Neurotrophic Factor/pharmacology
- Brain-Derived Neurotrophic Factor/physiology
- Cells, Cultured
- Ganglia, Spinal/cytology
- Ganglia, Spinal/drug effects
- Ganglia, Spinal/physiology
- Gene Expression Regulation, Developmental/physiology
- Mice
- Mice, Knockout
- Nerve Fibers/drug effects
- Nerve Fibers/physiology
- Neurites/drug effects
- Neurites/physiology
- Protein Precursors/pharmacology
- Protein Precursors/physiology
- Pseudopodia/drug effects
- Pseudopodia/physiology
- Receptors, Nerve Growth Factor/deficiency
- Receptors, Nerve Growth Factor/genetics
- Signal Transduction/physiology
- Time-Lapse Imaging
- rho GTP-Binding Proteins/agonists
- rho GTP-Binding Proteins/genetics
- rho GTP-Binding Proteins/metabolism
- rhoA GTP-Binding Protein
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Affiliation(s)
- Ying Sun
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Yoon Lim
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
- Division of Health Science, Sansom Institute, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, Australia
| | - Fang Li
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Shen Liu
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
- Division of Health Science, Sansom Institute, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, Australia
| | - Jian-Jun Lu
- Division of Health Science, Sansom Institute, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, Australia
| | - Rainer Haberberger
- Department of Anatomy and Histology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Jin-Hua Zhong
- Division of Health Science, Sansom Institute, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, Australia
| | - Xin-Fu Zhou
- Division of Health Science, Sansom Institute, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, Australia
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21
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Brown A, Weaver LC. The dark side of neuroplasticity. Exp Neurol 2011; 235:133-41. [PMID: 22116043 DOI: 10.1016/j.expneurol.2011.11.004] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 10/04/2011] [Accepted: 11/07/2011] [Indexed: 12/19/2022]
Abstract
Whether dramatic or modest, recovery of neurological function after spinal cord injury (SCI) is greatly due to neuroplasticity--the process by which the nervous system responds to injury by establishing new synaptic connections or by altering the strength of existing synapses. However, the same neuroplasticity that allows locomotor function to recover also produces negative consequences such as pain and dysfunction of organs controlled by the autonomic nervous system. In this review we focus specifically on structural neuroplasticity (the growth of new synaptic connections) after SCI and on the consequent development of pain and autonomic dysreflexia, a condition of episodic hypertension. Neuroplasticity after SCI is stimulated by the deafferentation of spinal neurons below the lesion and by the expression of growth-promoting neurotrophins such as nerve growth factor (NGF). A broad range of therapeutic strategies that affect neuroplasticity is being developed for the treatment of SCI. At one end of the spectrum are therapeutic strategies that directly or indirectly increase NGF in the injured spinal cord, and have the most robust effects on neuroplasticity. At the other end of the spectrum are neuroprotective strategies focused on supporting and rescuing uninjured, or partially injured, axons; these might limit the deafferentation stimulus for neuroplasticity. In the middle of this spectrum are strategies that block axon growth inhibitors without necessarily providing a growth stimulus. The literature supports the view that the negative consequences of neuroplasticity develop more commonly with therapies that directly stimulate nerve growth than they develop in the untreated injured cord. Compared to these conditions, neuroplasticity with negative outcomes is less prevalent after treatments that that neutralize axon growth inhibitors, and least apparent after strategies that promote neuroprotection.
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Affiliation(s)
- Arthur Brown
- Spinal Cord Injury Laboratory, Robarts Research Institute, University of Western Ontario, London, Ontario, Canada.
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22
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Mi S, Lee X, Hu Y, Ji B, Shao Z, Yang W, Huang G, Walus L, Rhodes K, Gong BJ, Miller RH, Pepinsky RB. Death receptor 6 negatively regulates oligodendrocyte survival, maturation and myelination. Nat Med 2011; 17:816-21. [PMID: 21725297 DOI: 10.1038/nm.2373] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2010] [Accepted: 04/06/2011] [Indexed: 12/11/2022]
Abstract
Survival and differentiation of oligodendrocytes are important for the myelination of central nervous system (CNS) axons during development and crucial for myelin repair in CNS demyelinating diseases such as multiple sclerosis. Here we show that death receptor 6 (DR6) is a negative regulator of oligodendrocyte maturation. DR6 is expressed strongly in immature oligodendrocytes and weakly in mature myelin basic protein (MBP)-positive oligodendrocytes. Overexpression of DR6 in oligodendrocytes leads to caspase 3 (casp3) activation and cell death. Attenuation of DR6 function leads to enhanced oligodendrocyte maturation, myelination and downregulation of casp3. Treatment with a DR6 antagonist antibody promotes remyelination in both lysolecithin-induced demyelination and experimental autoimmune encephalomyelitis (EAE) models. Consistent with the DR6 antagoinst antibody studies, DR6-null mice show enhanced remyelination in both demyelination models. These studies reveal a pivotal role for DR6 signaling in immature oligodendrocyte maturation and myelination that may provide new therapeutic avenues for the treatment of demyelination disorders such as multiple sclerosis.
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Affiliation(s)
- Sha Mi
- Biogen Idec, Cambridge, Massachusetts, USA.
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Gueye Y, Ferhat L, Sbai O, Bianco J, Ould-Yahoui A, Bernard A, Charrat E, Chauvin JP, Risso JJ, Féron F, Rivera S, Khrestchatisky M. Trafficking and secretion of matrix metalloproteinase-2 in olfactory ensheathing glial cells: A role in cell migration? Glia 2011; 59:750-70. [DOI: 10.1002/glia.21146] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Accepted: 12/20/2010] [Indexed: 02/06/2023]
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Remahl S, Angeria M, Remahl IN, Carlstedt T, Risling M. Observations at the CNS-PNS Border of Ventral Roots Connected to a Neuroma. Front Neurol 2010; 1:136. [PMID: 21188264 PMCID: PMC3008941 DOI: 10.3389/fneur.2010.00136] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Accepted: 09/28/2010] [Indexed: 01/15/2023] Open
Abstract
Previous studies have shown that numerous sprouts originating from a neuroma, after nerve injury in neonatal animals, can invade spinal nerve roots. However, no study with a focus on how such sprouts behave when they reach the border between the central and peripheral nervous system (CNS–PNS border) has been published. In this study we have in detail examined the CNS–PNS border of ventral roots in kittens with light and electron microscopy after early postnatal sciatic nerve resection. A transient ingrowth of substance P positive axons was observed into the CNS, but no spouts remained 6 weeks after the injury. Using serial sections and electron microscopy it was possible to identify small bundles of unmyelinated axons that penetrated from the root fascicles for a short distance into the CNS. These axons ended blindly, sometimes with a growth cone-like terminal swelling filled with vesicles. The axon bundles were accompanied by p75 positive cells in both the root fascicles and the pia mater, but not in the CNS. It may thus be suggested that neurotrophin presenting p75 positive cells could facilitate axonal growth into the pia mater and that the lack of such cells in the CNS compartment might contribute to the failure of growth into the CNS. A maldevelopment of myelin sheaths at the CNS–PNS border of motor axons was observed and it seems possible that this could have consequences for the propagation of action potential across this region after neonatal nerve injury. Thus, in this first detailed study on the behavior of recurrent sprouts at the CNS–PNS border.
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Affiliation(s)
- Sten Remahl
- Department of Neuroscience, Karolinska Institutet Stockholm Sweden
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25
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Turner BJ, Ackerley S, Davies KE, Talbot K. Dismutase-competent SOD1 mutant accumulation in myelinating Schwann cells is not detrimental to normal or transgenic ALS model mice. Hum Mol Genet 2009; 19:815-24. [DOI: 10.1093/hmg/ddp550] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Kramer F, Stöver T, Warnecke A, Diensthuber M, Lenarz T, Wissel K. BDNF mRNA expression is significantly upregulated in vestibular schwannomas and correlates with proliferative activity. J Neurooncol 2009; 98:31-9. [PMID: 19937367 DOI: 10.1007/s11060-009-0063-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2009] [Accepted: 11/09/2009] [Indexed: 01/20/2023]
Abstract
The expression of neurotrophic factors, such as artemin, glial cell line-derived neurotrophic factor (GDNF), neurturin, transforming growth factors (TGF)-beta1/beta2 and brain-derived neurotrophic factor (BDNF), is enhanced in vestibular schwannomas compared to peripheral nerves. Furthermore, this upregulation may correlate with mitotic activity. Vestibular schwannoma arising from Schwann cells of the vestibular nerve are mostly benign and slow-growing. Most of the pathogenic mechanisms regulating the vestibular schwannoma growth process are unknown. An impaired growth regulation and imbalance between mitosis and apoptosis can be assumed. However, molecular mechanisms interfering with regulation of the vestibular schwannoma growth also modulated by mitogenic factors have to be identified. Neurotrophic factors are involved in regulation of developmental processes in neuronal tissues and regeneration after peripheral nerve trauma and also reveal mitogenic effects on glial cell populations. Gene expression profiles of artemin, BDNF, GDNF, TGF-beta1/beta2 and Ret were determined in the vestibular schwannoma in comparison to the peripheral nerve tissues by using semiquantitative RT-PCR. The expression data were correlated to the proliferation-associated Ki-67 labelling index. A significant higher BDNF expression was observed in the vestibular schwannoma, whereas gene expression of artemin and GDNF was upregulated in peripheral nerves. The correlation between LI and BDNF, TGF-beta1 and Ret was found to be significant in the vestibular schwannoma. Our results demonstrate a coherence between BDNF expression and proliferative activity in the vestibular schwannoma. Based on these results, we propose a pivotal role for BDNF in modulating the vestibular schwannoma growth.
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Affiliation(s)
- Frauke Kramer
- Department of Gynecology and Obstetrics, Hannover Medical School, Hannover, Germany
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27
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Li F, Li L, Song XY, Zhong JH, Luo XG, Xian CJ, Zhou XF. Preconditioning selective ventral root injury promotes plasticity of ascending sensory neurons in the injured spinal cord of adult rats - possible roles of brain-derived
neurotrophic factor, TrkB and p75 neurotrophin receptor. Eur J Neurosci 2009; 30:1280-96. [DOI: 10.1111/j.1460-9568.2009.06920.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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28
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Chen Y, Zeng J, Cen L, Chen Y, Wang X, Yao G, Wang W, Qi W, Kong K. Multiple roles of the p75 neurotrophin receptor in the nervous system. J Int Med Res 2009; 37:281-8. [PMID: 19383220 DOI: 10.1177/147323000903700201] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The p75 neurotrophin receptor (p75NTR) is a transmembrane protein that binds nerve growth factor (NGF) and has multiple functions in the nervous system where it is expressed widely during the developmental stages of life, although expression decreases dramatically by adulthood. Expression of p75NTR can increase in pathological states related to neural cell death. p75NTR is a member of the tumour necrosis factor (TNF) receptor family and it consists of intracellular, transmembrane and extracellular domains which are different from other TNF receptors. Either by interacting with tropomyosin receptor kinase (Trk) receptors or via the independent binding of neurotrophin, p75NTR can induce neurite outgrowth and cellular survival or cell apoptosis through several complicated signal transduction pathways. Most of these signalling pathways remain to be elucidated. By interacting with different cellular factors, p75NTR can induce neuron growth cone collapse or regrowth. p75NTR is also expressed in a variety of glial populations. The many functions of p75NTR require further study.
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Affiliation(s)
- Y Chen
- Department of Orthopaedics, The Second Affiliated Hospital, ShanTou University Medical College, Guangdong, China
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Song XY, Zhang FH, Zhou FH, Zhong J, Zhou XF. Deletion of p75NTR impairs regeneration of peripheral nerves in mice. Life Sci 2009; 84:61-8. [PMID: 19026664 DOI: 10.1016/j.lfs.2008.10.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2008] [Revised: 10/07/2008] [Accepted: 10/29/2008] [Indexed: 01/11/2023]
Abstract
AIMS After peripheral nerve injury, p75NTR was upregulated in Schwann cells of the Wallerian degenerative nerves and in motor neurons but down-regulated in the injured sensory neurons. As p75NTR in neurons mediates signals of both neurotrophins and inhibitory factors, it is regarded as a therapeutic target for the treatment of neurodegeneration. However, its physiological function in the nerve regeneration is not fully understood. In the present study, we aimed to examine the role of p75NTR in the regeneration of peripheral nerves. MAIN METHODS In p75NTR knockout mice (exon III deletion), the sciatic nerves and facial nerves on one side were crushed and regenerating neurons in the facial nuclei and in the dorsal root ganglia were labelled by Fast Blue. The regenerating fibres in the sciatic nerve were also labelled by an anterograde tracer and by immunohistochemistry. KEY FINDINGS The results showed that the axonal growth of injured axons in the sciatic nerve of p75NTR mutant mice was significantly retarded. The number of regenerated neurons in the dorsal root ganglia and in the facial nuclei in p75NTR mutant mice was significantly reduced. Immunohistochemical staining of regenerating axons also showed the reduction in nerve regeneration in p75NTR mutant mice. SIGNIFICANCE Our data suggest that p75NTR plays an important role in the regeneration of injured peripheral nerves.
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Affiliation(s)
- Xing-Yun Song
- Department of Physiology and Centre for Neuroscience, Flinders University, GPO Box 2100, Adelaide 5001, Australia
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Bannerman P, Ara J, Hahn A, Hong L, McCauley E, Friesen K, Pleasure D. Peripheral nerve regeneration is delayed in neuropilin 2-deficient mice. J Neurosci Res 2008; 86:3163-9. [PMID: 18615644 PMCID: PMC2574585 DOI: 10.1002/jnr.21766] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Peripheral nerve transection or crush induces expression of class 3 semaphorins by epineurial and perineurial cells at the injury site and of the neuropilins neuropilin-1 and neuropilin-2 by Schwann and perineurial cells in the nerve segment distal to the injury. Neuropilin-dependent class 3 semaphorin signaling guides axons during neural development, but the significance of this signaling system for regeneration of adult peripheral nerves is not known. To test the hypothesis that neuropilin-2 facilitates peripheral-nerve axonal regeneration, we crushed sciatic nerves of adult neuropilin-2-deficient and littermate control mice. Axonal regeneration through the crush site and into the distal nerve segment, repression by the regenerating axons of Schwann cell p75 neurotrophin receptor expression, remyelination of the regenerating axons, and recovery of normal gait were all significantly slower in the neuropilin-2-deficient mice than in the control mice. Thus, neuropilin-2 facilitates peripheral-nerve axonal regeneration.
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Affiliation(s)
- Peter Bannerman
- Institute for Pediatric Regenerative Medicine, UC Davis School of Medicine, Sacramento CA
| | - Jahan Ara
- Dep’t of Pediatrics, Drexel University College of Medicine, Philadelphia PA
| | | | - Lindy Hong
- Institute for Pediatric Regenerative Medicine, UC Davis School of Medicine, Sacramento CA
| | - Erica McCauley
- Institute for Pediatric Regenerative Medicine, UC Davis School of Medicine, Sacramento CA
| | - Katie Friesen
- Institute for Pediatric Regenerative Medicine, UC Davis School of Medicine, Sacramento CA
| | - David Pleasure
- Institute for Pediatric Regenerative Medicine, UC Davis School of Medicine, Sacramento CA
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Duarte AG, Terminella L, Smith JT, Myers AC, Campbell G, Lick S. Restoration of Cough Reflex in Lung Transplant Recipients. Chest 2008; 134:310-316. [DOI: 10.1378/chest.07-2934] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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Feng SQ, Zhou XF, Rush RA, Ferguson IA. Graft of pre-injured sural nerve promotes regeneration of corticospinal tract and functional recovery in rats with chronic spinal cord injury. Brain Res 2008; 1209:40-8. [DOI: 10.1016/j.brainres.2008.02.075] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2008] [Revised: 02/25/2008] [Accepted: 02/26/2008] [Indexed: 11/28/2022]
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Ueda H. Peripheral mechanisms of neuropathic pain - involvement of lysophosphatidic acid receptor-mediated demyelination. Mol Pain 2008; 4:11. [PMID: 18377664 PMCID: PMC2365930 DOI: 10.1186/1744-8069-4-11] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2008] [Accepted: 04/01/2008] [Indexed: 01/23/2023] Open
Abstract
Recent advances in pain research provide a clear picture for the molecular mechanisms of acute pain; substantial information concerning plasticity that occurs during neuropathic pain has also become available. The peripheral mechanisms responsible for neuropathic pain are found in the altered gene/protein expression of primary sensory neurons. With damage to peripheral sensory fibers, a variety of changes in pain-related gene expression take place in dorsal root ganglion neurons. These changes, or plasticity, might underlie unique neuropathic pain-specific phenotype modifications - decreased unmyelinated-fiber functions, but increased myelinated A-fiber functions. Another characteristic change is observed in allodynia, the functional change of tactile to nociceptive perception. Throughout a series of studies, using novel nociceptive tests to characterize sensory-fiber or pain modality-specific nociceptive behaviors, it was demonstrated that communication between innocuous and noxious sensory fibers might play a role in allodynia mechanisms. Because neuropathic pain in peripheral and central demyelinating diseases develops as a result of aberrant myelination in experimental animals, demyelination seems to be a key mechanism of plasticity in neuropathic pain. More recently, we discovered that lysophosphatidic acid receptor activation initiates neuropathic pain, as well as possible peripheral mechanism of demyelination after nerve injury. These results lead to further hypotheses of physical communication between innocuous Abeta- and noxious C- or Adelta-fibers to influence the molecular mechanisms of allodynia.
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Affiliation(s)
- Hiroshi Ueda
- Division of Molecular Pharmacology and Neuroscience, Nagasaki University Graduate School of Biomedical Sciences, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
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Song XY, Li F, Zhang FH, Zhong JH, Zhou XF. Peripherally-derived BDNF promotes regeneration of ascending sensory neurons after spinal cord injury. PLoS One 2008; 3:e1707. [PMID: 18320028 PMCID: PMC2246162 DOI: 10.1371/journal.pone.0001707] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2007] [Accepted: 02/04/2008] [Indexed: 12/12/2022] Open
Abstract
Background The blood brain barrier (BBB) and truncated trkB receptor on astrocytes prevent the penetration of brain derived neurotrophic factor (BDNF) applied into the peripheral (PNS) and central nervous system (CNS) thus restrict its application in the treatment of nervous diseases. As BDNF is anterogradely transported by axons, we propose that peripherally derived and/or applied BDNF may act on the regeneration of central axons of ascending sensory neurons. Methodology/Principal Findings The present study aimed to test the hypothesis by using conditioning lesion of the sciatic nerve as a model to increase the expression of endogenous BDNF in sensory neurons and by injecting exogenous BDNF into the peripheral nerve or tissues. Here we showed that most of regenerating sensory neurons expressed BDNF and p-CREB but not p75NTR. Conditioning-lesion induced regeneration of ascending sensory neuron and the increase in the number of p-Erk positive and GAP-43 positive neurons was blocked by the injection of the BDNF antiserum in the periphery. Enhanced neurite outgrowth of dorsal root ganglia (DRG) neurons in vitro by conditioning lesion was also inhibited by the neutralization with the BDNF antiserum. The delivery of exogenous BDNF into the sciatic nerve or the footpad significantly increased the number of regenerating DRG neurons and regenerating sensory axons in the injured spinal cord. In a contusion injury model, an injection of BDNF into the footpad promoted recovery of motor functions. Conclusions/Significance Our data suggest that endogenous BDNF in DRG and spinal cord is required for the enhanced regeneration of ascending sensory neurons after conditioning lesion of sciatic nerve and peripherally applied BDNF may have therapeutic effects on the spinal cord injury.
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Affiliation(s)
- Xing-Yun Song
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Fang Li
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
- Department of Anatomy and Neurobiology, Xiangya School of Medicine, Central South University, Changsha, People's Republic of China
| | - Feng-He Zhang
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Jin-Hua Zhong
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Xin-Fu Zhou
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
- *E-mail:
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Cragnolini AB, Friedman WJ. The function of p75NTR in glia. Trends Neurosci 2008; 31:99-104. [PMID: 18199491 DOI: 10.1016/j.tins.2007.11.005] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2007] [Revised: 11/20/2007] [Accepted: 11/21/2007] [Indexed: 11/19/2022]
Abstract
The p75 neurotrophin receptor (p75(NTR)) is expressed on many cell types and can influence a variety of cellular functions. This receptor can mediate cell survival or cell death, can promote or inhibit axonal growth and can facilitate or attenuate proliferation, depending on the cell context. The emerging picture regarding p75(NTR) indicates that it can partner with different coreceptors to dictate specific responses. It then signals by recruiting intracellular binding proteins to activate different signaling pathways. The function of p75(NTR) has mainly been studied in neurons; however, it is also expressed in a variety of glial populations, especially during development and after injury, where its roles have been poorly defined. In this review, we will examine the potential roles for p75(NTR) in glial function.
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Affiliation(s)
- Andrea B Cragnolini
- Department of Biological Sciences, Rutgers University, Newark, NJ 07102, USA
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Loesch A, Cowen T. On the presence of neurotrophin p75 receptor on rat sympathetic cerebrovascular nerves. J Mol Histol 2007; 39:57-68. [PMID: 17671845 DOI: 10.1007/s10735-007-9126-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2007] [Accepted: 07/17/2007] [Indexed: 10/23/2022]
Abstract
Although the presence of neurotrophin p75 receptor on sympathetic nerves is a well-recognised feature, there is still a scarcity of details of the distribution of the receptor on cerebrovascular nerves. This study examined the distribution of p75 receptor on perivascular sympathetic nerves of the middle cerebral artery and the basilar artery of healthy young rats using immunohistochemical methods at the laser confocal microscope and transmission electron microscope levels. Immunofluorescence methods of detection of tyrosine hydroxylase (TH) in sympathetic nerves, p75 receptor associated with the nerves, and also S-100 protein in Schwann cells were applied in conjunction with confocal microscopy, while the pre-embedding single and double immunolabelling methods (ExtrAvidin and immuno-gold-silver) were applied for the electron microscopic examination. Immunofluorescence studies revealed "punctuate" distribution of the p75 receptor on sympathetic nerves including accompanying Schwann cells. Image analysis of the nerves showed that the level of co-localization of p75 receptor and TH was low. Immunolabelling applied at the electron microscope level also showed scarce co-localization of TH (which was intra-axonal) and p75. Immunoreactivity for p75 receptor was present on the cell membrane of perivascular axons and to a greater extent on the processes of accompanying Schwann cells. Some Schwann cell processes were adjacent to each other displaying strong immunoreactivity for p75 receptor; immunoreactivity was located on the extracellular sites of the adjacent cell membranes suggesting that the receptor was involved in cross talk between these. It is likely that variability of locations of p75 receptor detected in the study reflects diverse interactions of p75 receptor with axons and Schwann cells. It might also imply a diverse role for the receptor and/or the plasticity of sympathetic cerebrovascular nerves to neurotrophin signalling.
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Affiliation(s)
- Andrzej Loesch
- Department of Anatomy and Developmental Biology (Hampstead Campus), Royal Free and University College Medical School, University College London, Rowland Hill Street, London, NW3 2PF, UK.
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