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Myelination of Axons Corresponds with Faster Transmission Speed in the Prefrontal Cortex of Developing Male Rats. eNeuro 2018; 5:eN-NWR-0203-18. [PMID: 30225359 PMCID: PMC6140121 DOI: 10.1523/eneuro.0203-18.2018] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 08/13/2018] [Accepted: 08/14/2018] [Indexed: 12/31/2022] Open
Abstract
Myelination of prefrontal circuits during adolescence is thought to lead to enhanced cognitive processing and improved behavioral control. However, while standard neuroimaging techniques commonly used in human and animal studies can measure large white matter bundles and residual conduction speed, they cannot directly measure myelination of individual axons or how fast electrical signals travel along these axons. Here we focused on a specific population of prefrontal axons to directly measure conduction velocity and myelin microstructure in developing male rats. An in vitro electrophysiological approach enabled us to isolate monosynaptic projections from the anterior branches of the corpus callosum (corpus callosum-forceps minor, CCFM) to the anterior cingulate subregion of the medial prefrontal cortex (Cg1) and to measure the speed and direction of action potentials propagating along these axons. We found that a large number of axons projecting from the CCFM to neurons in Layer V of Cg1 are ensheathed with myelin between pre-adolescence [postnatal day (PD)15] and mid-adolescence (PD43). This robust increase in axonal myelination is accompanied by a near doubling of transmission speed. As there was no age difference in the diameter of these axons, myelin is likely the driving force behind faster transmission of electrical signals in older animals. These developmental changes in axonal microstructure and physiology may extend to other axonal populations as well, and could underlie some of the improvements in cognitive processing between childhood and adolescence.
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152
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Naughton SX, Hernandez CM, Beck WD, Poddar I, Yanasak N, Lin PC, Terry AV. Repeated exposures to diisopropylfluorophosphate result in structural disruptions of myelinated axons and persistent impairments of axonal transport in the brains of rats. Toxicology 2018; 406-407:92-103. [DOI: 10.1016/j.tox.2018.06.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 05/02/2018] [Accepted: 06/08/2018] [Indexed: 01/17/2023]
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153
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Changes in white matter in mice resulting from low-frequency brain stimulation. Proc Natl Acad Sci U S A 2018; 115:E6339-E6346. [PMID: 29915074 DOI: 10.1073/pnas.1802160115] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Recent reports have begun to elucidate mechanisms by which learning and experience produce white matter changes in the brain. We previously reported changes in white matter surrounding the anterior cingulate cortex in humans after 2-4 weeks of meditation training. We further found that low-frequency optogenetic stimulation of the anterior cingulate in mice increased time spent in the light in a light/dark box paradigm, suggesting decreased anxiety similar to what is observed following meditation training. Here, we investigated the impact of this stimulation at the cellular level. We found that laser stimulation in the range of 1-8 Hz results in changes to subcortical white matter projection fibers in the corpus callosum. Specifically, stimulation resulted in increased oligodendrocyte proliferation, accompanied by a decrease in the g-ratio within the corpus callosum underlying the anterior cingulate cortex. These results suggest that low-frequency stimulation can result in activity-dependent remodeling of myelin, giving rise to enhanced connectivity and altered behavior.
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154
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Positive changes in femoral nerve morphometry in older rats following aerobic training. Exp Gerontol 2018; 110:92-97. [PMID: 29803871 DOI: 10.1016/j.exger.2018.05.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 05/14/2018] [Accepted: 05/18/2018] [Indexed: 11/24/2022]
Abstract
The objective of the present study was to analyze alterations of the femoral nerve of aged rats subjected to aerobic training. Wistar rats (12-mo of age) were divided in to two groups: S group (sedentary) and T group (trained). The exercise protocol were 16 weeks long. The groups were sacrificed at 16 months. Ultrafine sections of the femoral nerve have been used. There was no change in the body weight between the groups. T group showed a significant increase in myelinated fiber area, axon diameter, myelin sheath thickness and myelin fiber number compared with sedentary controls. In exercised trained animals, histograms of the frequency distribution of myelinated axons according to their areas showed increased number of medium and large fibers in relation to small fibers, which decreased in number. Aerobic training animals, showed the distribution of myelinated fiber population according to their area being bimodal, with the distribution shifted to the right, indicating increased fiber area. The T group showed a percent damage of large myelinated fibers significantly lower compared to controls. No significant difference was observed between the groups for the g-ratio. The T group also showed a significant increase in the number of microtubules and neurofilaments in myelinated fibers, which was not observed in S group. In conclusion, aerobic training improves nerve structure without evidence of nerve damage and produces an attenuation on the modifications in femoral nerve that develop in old age.
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155
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Lin T, Qiu S, Yan L, Zhu S, Zheng C, Zhu Q, Liu X. Miconazole enhances nerve regeneration and functional recovery after sciatic nerve crush injury. Muscle Nerve 2018; 57:821-828. [PMID: 29211920 DOI: 10.1002/mus.26033] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 11/28/2017] [Accepted: 12/02/2017] [Indexed: 12/13/2022]
Abstract
INTRODUCTION Improving axonal outgrowth and remyelination is crucial for peripheral nerve regeneration. Miconazole appears to enhance remyelination in the central nervous system. In this study we assess the effect of miconazole on axonal regeneration using a sciatic nerve crush injury model in rats. METHODS Fifty Sprague-Dawley rats were divided into control and miconazole groups. Nerve regeneration and myelination were determined using histological and electrophysiological assessment. Evaluation of sensory and motor recovery was performed using the pinprick assay and sciatic functional index. The Cell Counting Kit-8 assay and Western blotting were used to assess the proliferation and neurotrophic expression of RSC 96 Schwann cells. RESULTS Miconazole promoted axonal regrowth, increased myelinated nerve fibers, improved sensory recovery and walking behavior, enhanced stimulated amplitude and nerve conduction velocity, and elevated proliferation and neurotrophic expression of RSC 96 Schwann cells. DISCUSSION Miconazole was beneficial for nerve regeneration and functional recovery after peripheral nerve injury. Muscle Nerve 57: 821-828, 2018.
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Affiliation(s)
- Tao Lin
- Department of Orthopedic and Microsurgery, The First Affiliated Hospital of Sun Yat-sen University, No. 58 Zhongshan Second Road, Guangzhou, 5180080, PR China
| | - Shuai Qiu
- Department of Orthopedic and Microsurgery, The First Affiliated Hospital of Sun Yat-sen University, No. 58 Zhongshan Second Road, Guangzhou, 5180080, PR China
| | - Liwei Yan
- Department of Orthopedic and Microsurgery, The First Affiliated Hospital of Sun Yat-sen University, No. 58 Zhongshan Second Road, Guangzhou, 5180080, PR China
| | - Shuang Zhu
- Department of Orthopedic and Microsurgery, The First Affiliated Hospital of Sun Yat-sen University, No. 58 Zhongshan Second Road, Guangzhou, 5180080, PR China
| | - Canbin Zheng
- Department of Orthopedic and Microsurgery, The First Affiliated Hospital of Sun Yat-sen University, No. 58 Zhongshan Second Road, Guangzhou, 5180080, PR China
| | - Qingtang Zhu
- Department of Orthopedic and Microsurgery, The First Affiliated Hospital of Sun Yat-sen University, No. 58 Zhongshan Second Road, Guangzhou, 5180080, PR China
| | - Xiaolin Liu
- Department of Orthopedic and Microsurgery, The First Affiliated Hospital of Sun Yat-sen University, No. 58 Zhongshan Second Road, Guangzhou, 5180080, PR China
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156
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Lucia FS, Pacheco-Torres J, González-Granero S, Canals S, Obregón MJ, García-Verdugo JM, Berbel P. Transient Hypothyroidism During Lactation Arrests Myelination in the Anterior Commissure of Rats. A Magnetic Resonance Image and Electron Microscope Study. Front Neuroanat 2018; 12:31. [PMID: 29755326 PMCID: PMC5935182 DOI: 10.3389/fnana.2018.00031] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2018] [Accepted: 04/09/2018] [Indexed: 12/14/2022] Open
Abstract
Thyroid hormone deficiency at early postnatal ages affects the cytoarchitecture and function of neocortical and telencephalic limbic areas, leading to impaired associative memory and in a wide spectrum of neurological and mental diseases. Neocortical areas project interhemispheric axons mostly through the corpus callosum and to a lesser extent through the anterior commissure (AC), while limbic areas mostly project through the AC and hippocampal commissures. Functional magnetic resonance data from children with late diagnosed congenital hypothyroidism and abnormal verbal memory processing, suggest altered ipsilateral and contralateral telencephalic connections. Gestational hypothyroidism affects AC development but the possible effect of transient and chronic postnatal hypothyroidism, as occurs in late diagnosed neonates with congenital hypothyroidism and in children growing up in iodine deficient areas, still remains unknown. We studied AC development using in vivo magnetic resonance imaging and electron microscopy in hypothyroid and control male rats. Four groups of methimazole (MMI) treated rats were studied. One group was MMI-treated from postnatal day (P) 0 to P21; some of these rats were also treated with L-thyroxine (T4) from P15 to P21, as a model for early transient hypothyroidism. Other rats were MMI-treated from P0 to P150 and from embryonic day (E) 10 to P170, as a chronic hypothyroidism group. The results were compared with age paired control rats. The normalized T2 signal using magnetic resonance image was higher in MMI-treated rats and correlated with the number and percentage of myelinated axons. Using electron microscopy, we observed decreased myelinated axon number and density in transient and chronic hypothyroid rats at P150, unmyelinated axon number increased slightly in chronic hypothyroid rats. In MMI-treated rats, the myelinated axon g-ratio and conduction velocity was similar to control rats, but with a decrease in conduction delays. These data show that early postnatal transient and chronic hypothyroidism alters AC maturation that may affect the transfer of information through the AC. The alterations cannot be recovered after delayed T4-treatment. Our data support the neurocognitive delay found in late T4-treated children with congenital hypothyroidism.
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Affiliation(s)
- Federico S. Lucia
- Departamento de Histología y Anatomía, Facultad de Medicina, Universidad Miguel Hernández, Sant Joan d’Alacant, Alicante, Spain
| | - Jesús Pacheco-Torres
- Instituto de Neurociencias de Alicante, Consejo Superior de Investigaciones Científicas, Universidad Miguel Hernández, Alicante, Spain
| | - Susana González-Granero
- Laboratorio de Neurobiología Comparada, Instituto Cavanilles de Biodiversidad y Biología Evolutiva, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, Universitat de València, Valencia, Spain
| | - Santiago Canals
- Instituto de Neurociencias de Alicante, Consejo Superior de Investigaciones Científicas, Universidad Miguel Hernández, Alicante, Spain
| | - María-Jesús Obregón
- Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain
| | - José M. García-Verdugo
- Laboratorio de Neurobiología Comparada, Instituto Cavanilles de Biodiversidad y Biología Evolutiva, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, Universitat de València, Valencia, Spain
| | - Pere Berbel
- Departamento de Histología y Anatomía, Facultad de Medicina, Universidad Miguel Hernández, Sant Joan d’Alacant, Alicante, Spain
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157
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Collins LN, Hill DL, Brunjes PC. Myelination of the developing lateral olfactory tract and anterior commissure. J Comp Neurol 2018; 526:1843-1858. [PMID: 29665005 DOI: 10.1002/cne.24452] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 03/20/2018] [Accepted: 03/21/2018] [Indexed: 12/15/2022]
Abstract
Both the lateral olfactory tract (LOT) and anterior limb of the anterior commissure (AC) carry olfactory information. The LOT forms the projection from the olfactory bulb to the ipsilateral olfactory cortices, while the AC carries odor information across the midline to the contralateral olfactory cortex and bulb. The LOT and AC differ on a number of dimensions, including early development and functional onset. The present work, examining their myelination in mice, reveals additional important differences. For example, the LOT initiates myelination 3-4 days earlier than the AC, evidenced by both an earlier increase in myelin basic protein staining seen with immunohistochemistry and an earlier appearance of myelinated fibers using electron microscopy. While both exhibit a period of rapid myelination, it occurs 4-5 days earlier in the LOT than the AC. The tracts also respond differently to early sensory restriction. Unilateral naris occlusion from the day after birth to postnatal day 30 had no consistent effects on the AC but resulted in significantly thinner myelin sheaths relative to axon caliber in the LOT. Finally, the two tracts differ structurally (the LOT contains larger, more densely packed axons with significantly thicker myelin sheaths resulting in a conduction velocity that is more than twice as fast as the AC). The findings indicate that these two large, accessible tracts provide an important means for studying brain maturation due to basic differences in both the timing of their maturation and general organization.
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Affiliation(s)
- L N Collins
- Department Psychology, University of Virginia, Charlottesville, Virginia
| | - D L Hill
- Department Psychology, University of Virginia, Charlottesville, Virginia
| | - P C Brunjes
- Department Psychology, University of Virginia, Charlottesville, Virginia
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158
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Cohen-Adad J. Microstructural imaging in the spinal cord and validation strategies. Neuroimage 2018; 182:169-183. [PMID: 29635029 DOI: 10.1016/j.neuroimage.2018.04.009] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 03/02/2018] [Accepted: 04/06/2018] [Indexed: 12/13/2022] Open
Abstract
In vivo histology using magnetic resonance imaging (MRI) is a newly emerging research field that aims to non-invasively characterize tissue microstructure. The implications of in vivo histology are many, from discovering novel biomarkers to studying human development, to providing tools for disease diagnosis and monitoring the effects of novel treatments on tissue. This review focuses on quantitative MRI (qMRI) techniques that are used to map spinal cord microstructure. Opening with a rationale for non-invasive imaging of the spinal cord, this article continues with a brief overview of the existing MRI techniques for axon and myelin imaging, followed by the specific challenges and potential solutions for acquiring and processing such data. The final part of this review focuses on histological validation, with suggested tissue preparation, acquisition and processing protocols for large-scale microscopy.
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Affiliation(s)
- J Cohen-Adad
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada; Functional Neuroimaging Unit, CRIUGM, Université de Montréal, Montreal, QC, Canada.
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159
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Zaimi A, Wabartha M, Herman V, Antonsanti PL, Perone CS, Cohen-Adad J. AxonDeepSeg: automatic axon and myelin segmentation from microscopy data using convolutional neural networks. Sci Rep 2018; 8:3816. [PMID: 29491478 PMCID: PMC5830647 DOI: 10.1038/s41598-018-22181-4] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 02/06/2018] [Indexed: 01/03/2023] Open
Abstract
Segmentation of axon and myelin from microscopy images of the nervous system provides useful quantitative information about the tissue microstructure, such as axon density and myelin thickness. This could be used for instance to document cell morphometry across species, or to validate novel non-invasive quantitative magnetic resonance imaging techniques. Most currently-available segmentation algorithms are based on standard image processing and usually require multiple processing steps and/or parameter tuning by the user to adapt to different modalities. Moreover, only a few methods are publicly available. We introduce AxonDeepSeg, an open-source software that performs axon and myelin segmentation of microscopic images using deep learning. AxonDeepSeg features: (i) a convolutional neural network architecture; (ii) an easy training procedure to generate new models based on manually-labelled data and (iii) two ready-to-use models trained from scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results show high pixel-wise accuracy across various species: 85% on rat SEM, 81% on human SEM, 95% on mice TEM and 84% on macaque TEM. Segmentation of a full rat spinal cord slice is computed and morphological metrics are extracted and compared against the literature. AxonDeepSeg is freely available at https://github.com/neuropoly/axondeepseg .
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Affiliation(s)
- Aldo Zaimi
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada
| | - Maxime Wabartha
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada
- Ecole Centrale de Lille, Lille, France
| | - Victor Herman
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada
- Ecole Centrale de Lille, Lille, France
| | - Pierre-Louis Antonsanti
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada
- Ecole Centrale de Nantes, Nantes, France
| | - Christian S Perone
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada
| | - Julien Cohen-Adad
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada.
- Functional Neuroimaging Unit, CRIUGM, Université de Montréal, Montreal, QC, Canada.
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160
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Melbourne A, Toussaint N, Owen D, Simpson I, Anthopoulos T, De Vita E, Atkinson D, Ourselin S. NiftyFit: a Software Package for Multi-parametric Model-Fitting of 4D Magnetic Resonance Imaging Data. Neuroinformatics 2018; 14:319-37. [PMID: 26972806 PMCID: PMC4896995 DOI: 10.1007/s12021-016-9297-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Multi-modal, multi-parametric Magnetic Resonance (MR) Imaging is becoming an increasingly sophisticated tool for neuroimaging. The relationships between parameters estimated from different individual MR modalities have the potential to transform our understanding of brain function, structure, development and disease. This article describes a new software package for such multi-contrast Magnetic Resonance Imaging that provides a unified model-fitting framework. We describe model-fitting functionality for Arterial Spin Labeled MRI, T1 Relaxometry, T2 relaxometry and Diffusion Weighted imaging, providing command line documentation to generate the figures in the manuscript. Software and data (using the nifti file format) used in this article are simultaneously provided for download. We also present some extended applications of the joint model fitting framework applied to diffusion weighted imaging and T2 relaxometry, in order to both improve parameter estimation in these models and generate new parameters that link different MR modalities. NiftyFit is intended as a clear and open-source educational release so that the user may adapt and develop their own functionality as they require.
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Affiliation(s)
- Andrew Melbourne
- Centre for Medical Image Computing, University College London, London, UK.
| | - Nicolas Toussaint
- Centre for Medical Image Computing, University College London, London, UK
| | - David Owen
- Centre for Medical Image Computing, University College London, London, UK
| | - Ivor Simpson
- Centre for Medical Image Computing, University College London, London, UK
| | | | - Enrico De Vita
- Academic Neuroradiological Unit, UCL Institute of Neurology, London, UK
| | - David Atkinson
- Medical Physics, University College Hospital, London, UK
| | - Sebastien Ourselin
- Centre for Medical Image Computing, University College London, London, UK
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161
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Ramalho BDS, Almeida FMD, Sales CM, de Lima S, Martinez AMB. Injection of bone marrow mesenchymal stem cells by intravenous or intraperitoneal routes is a viable alternative to spinal cord injury treatment in mice. Neural Regen Res 2018; 13:1046-1053. [PMID: 29926832 PMCID: PMC6022457 DOI: 10.4103/1673-5374.233448] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In spite of advances in surgical care and rehabilitation, the consequences of spinal cord injury (SCI) are still challenging. Several experimental therapeutic strategies have been studied in the SCI field, and recent advances have led to the development of therapies that may act on the inhibitory microenvironment. Assorted lineages of stem cells are considered a good treatment for SCI. This study investigated the effect of systemic transplantation of mesenchymal stem cells (MSCs) in a compressive SCI model. Here we present results of the intraperitoneal route, which has not been used previously for MSC administration after compressive SCI. We used adult female C57BL/6 mice that underwent laminectomy at the T9 level, followed by spinal cord compression for 1 minute with a 30-g vascular clip. The animals were divided into five groups: sham (anesthesia and laminectomy but without compression injury induction), MSC i.p. (intraperitoneal injection of 8 × 105 MSCs in 500 µL of DMEM at 7 days after SCI), MSC i.v. (intravenous injection of 8 × 105 MSCs in 500 µL of DMEM at 7 days after SCI), DMEM i.p. (intraperitoneal injection of 500 µL of DMEM at 7 days after SCI), DMEM i.v. (intravenous injection of 500 µL of DMEM at 7 days after SCI). The effects of MSCs transplantation in white matter sparing were analyzed by luxol fast blue staining. The number of preserved fibers was counted in semithin sections stained with toluidine blue and the presence of trophic factors was analyzed by immunohistochemistry. In addition, we analyzed the locomotor performance with Basso Mouse Scale and Global Mobility Test. Our results showed white matter preservation and a larger number of preserved fibers in the MSC groups than in the DMEM groups. Furthermore, the MSC groups had higher levels of trophic factors (brain-derived neurotrophic factor, nerve growth factor, neurotrophin-3 and neurotrophin-4) in the spinal cord and improved locomotor performance. Our results indicate that injection of MSCs by either intraperitoneal or intravenous routes results in beneficial outcomes and can be elected as a choice for SCI treatment.
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Affiliation(s)
- Bruna Dos Santos Ramalho
- Laboratório de Neurodegeneração e Reparo, Departamento de Patologia - Faculdade de Medicina, HUCFF, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Fernanda Martins de Almeida
- Laboratório de Neurodegeneração e Reparo, Departamento de Patologia - Faculdade de Medicina, HUCFF, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Conrado Mendonça Sales
- Laboratório de Neurodegeneração e Reparo, Departamento de Patologia - Faculdade de Medicina, HUCFF, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Silmara de Lima
- Laboratório de Neurodegeneração e Reparo, Departamento de Patologia - Faculdade de Medicina, HUCFF, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Ana Maria Blanco Martinez
- Laboratório de Neurodegeneração e Reparo, Departamento de Patologia - Faculdade de Medicina, HUCFF, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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162
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Saller MM, Huettl RE, Mayer JM, Feuchtinger A, Krug C, Holzbach T, Volkmer E. Validation of a novel animal model for sciatic nerve repair with an adipose-derived stem cell loaded fibrin conduit. Neural Regen Res 2018; 13:854-861. [PMID: 29863016 PMCID: PMC5998632 DOI: 10.4103/1673-5374.232481] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Despite the regenerative capabilities of peripheral nerves, severe injuries or neuronal trauma of critical size impose immense hurdles for proper restoration of neuro-muscular circuitry. Autologous nerve grafts improve re-establishment of connectivity, but also comprise substantial donor site morbidity. We developed a rat model which allows the testing of different cell applications, i.e., mesenchymal stem cells, to improve nerve regeneration in vivo. To mimic inaccurate alignment of autologous nerve grafts with the injured nerve, a 20 mm portion of the sciatic nerve was excised, and sutured back in place in reversed direction. To validate the feasibility of our novel model, a fibrin gel conduit containing autologous undifferentiated adipose-derived stem cells was applied around the coaptation sites and compared to autologous nerve grafts. After evaluating sciatic nerve function for 16 weeks postoperatively, animals were sacrificed, and gastrocnemius muscle weight was determined along with morphological parameters (g-ratio, axon density & diameter) of regenerating axons. Interestingly, the addition of undifferentiated adipose-derived stem cells resulted in a significantly improved re-myelination, axon ingrowth and functional outcome, when compared to animals without a cell seeded conduit. The presented model thus displays several intriguing features: it imitates a certain mismatch in size, distribution and orientation of axons within the nerve coaptation site. The fibrin conduit itself allows for an easy application of cells and, as a true critical-size defect model, any observed improvement relates directly to the performed intervention. Since fibrin and adipose-derived stem cells have been approved for human applications, the technique can theoretically be performed on humans. Thus, we suggest that the model is a powerful tool to investigate cell mediated assistance of peripheral nerve regeneration.
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Affiliation(s)
- Maximilian M Saller
- Experimental Surgery and Regenerative Medicine (ExperiMed), Department of General, Trauma and Reconstructive Surgery, Ludwig-Maximilians-University (LMU), Munich, Germany
| | - Rosa-Eva Huettl
- Max-Planck-Institute of Psychiatry, Department of Stress Neurobiology and Neurogenetics, Munich, Germany
| | - Julius M Mayer
- Experimental Surgery and Regenerative Medicine (ExperiMed), Department of General, Trauma and Reconstructive Surgery, Ludwig-Maximilians-University (LMU); Department of Hand-, Plastic- and Aesthetic Surgery, Ludwig-Maximilians-University (LMU), Munich, Germany
| | - Annette Feuchtinger
- Research Unit Analytical Pathology, Munich, Helmholtz Zentrum Muenchen-German Research Center for Environmental Health (GmbH), Neuherberg, Germany
| | - Christian Krug
- Department of Hand-, Plastic- and Aesthetic Surgery, Ludwig-Maximilians-University (LMU), Munich, Germany; Department of Hand and Plastic Surgery, Spital Thurgau AG, Frauenfeld, Switzerland
| | - Thomas Holzbach
- Department of Hand-, Plastic- and Aesthetic Surgery, Ludwig-Maximilians-University (LMU), Munich, Germany; Department of Hand and Plastic Surgery, Spital Thurgau AG, Frauenfeld, Switzerland
| | - Elias Volkmer
- Experimental Surgery and Regenerative Medicine (ExperiMed), Department of General, Trauma and Reconstructive Surgery, Ludwig-Maximilians-University (LMU); Department of Hand-, Plastic- and Aesthetic Surgery, Ludwig-Maximilians-University (LMU), Munich, Germany
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163
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West KL, Kelm ND, Carson RP, Alexander DC, Gochberg DF, Does MD. Experimental studies of g-ratio MRI in ex vivo mouse brain. Neuroimage 2017; 167:366-371. [PMID: 29208572 DOI: 10.1016/j.neuroimage.2017.11.064] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2017] [Revised: 11/26/2017] [Accepted: 11/29/2017] [Indexed: 12/13/2022] Open
Abstract
This study aimed to experimentally evaluate a previously proposed MRI method for mapping axonal g-ratio (ratio of axon diameters, measured to the inner and outer boundary of myelin). MRI and electron microscopy were used to study excised and fixed brains of control mice and three mouse models of abnormal white matter. The results showed that g-ratio measured with MRI correlated with histological measures of myelinated axon g-ratio, but with a bias that is likely due to the presence of non-myelinated axons. The results also pointed to cases where the MRI g-ratio model simplifies to be primarily a function of total myelin content.
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Affiliation(s)
- Kathryn L West
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States; Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States
| | - Nathaniel D Kelm
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States; Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States
| | - Robert P Carson
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, United States; Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, United States
| | - Daniel C Alexander
- Center for Medical Image Computing, Department of Computer Science, University College London, London, United Kingdom
| | - Daniel F Gochberg
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States; Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States
| | - Mark D Does
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States; Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States; Department of Electrical Engineering, Vanderbilt University, Nashville, TN, United States.
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164
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Moore ME, Koenig AE, Hillgartner MA, Otap CC, Barnby E, MacGregor GG. Abnormal social behavior in mice with tyrosinemia type I is associated with an increase of myelin in the cerebral cortex. Metab Brain Dis 2017; 32:1829-1841. [PMID: 28712060 DOI: 10.1007/s11011-017-0071-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 07/11/2017] [Indexed: 12/26/2022]
Abstract
Hereditary tyrosinemia type I (HT1) is caused by mutations in the fumarylacetoacetate hydrolase (FAH) gene, the template for the final enzyme in the tyrosine catabolism pathway. If left untreated this deficiency of functional FAH leads to a buildup of toxic metabolites that can cause liver disease, kidney dysfunction and high mortality. The current treatment with the drug NTBC prevents the production of these metabolites and has consequently increased the survival rate in HT1 children. As a result of this increased survival, long term complications of HT1 are now being observed, including slower learning, impaired cognition and altered social behavior. We studied a mouse model of HT1 to gain insight into the effects of HT1 and treatment with NTBC on social behavior in mice. We showed that mice with HT1 display abnormal social behavior in that they spend more time in the absence of another mouse and do not discriminate between a novel mouse and an already familiar mouse. This altered behavior was due to HT1 and not treatment with NTBC. Quantification of cerebral cortex myelin in mice with HT1 showed a two to threefold increase in myelin expression. Our findings suggest that absence of FAH expression in the brain produces an altered brain biochemistry resulting in increased expression of myelin. This increase in myelination could lead to abnormal action potential velocity and altered neuronal connections that provide a mechanism for the altered learning, social behavior and cognitive issues recently seen in HT1.
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Affiliation(s)
- Marissa E Moore
- Department of Biological Sciences, University of Alabama in Huntsville, SST 361, 301 Sparkman Dr, Huntsville, AL, 35899, USA
| | - Ashton E Koenig
- Department of Biological Sciences, University of Alabama in Huntsville, SST 361, 301 Sparkman Dr, Huntsville, AL, 35899, USA
| | - Megan A Hillgartner
- Department of Biological Sciences, University of Alabama in Huntsville, SST 361, 301 Sparkman Dr, Huntsville, AL, 35899, USA
| | - Christopher C Otap
- Department of Biological Sciences, University of Alabama in Huntsville, SST 361, 301 Sparkman Dr, Huntsville, AL, 35899, USA
| | - Elizabeth Barnby
- College of Nursing, University of Alabama in Huntsville, 1610 Ben Graves Drive, Huntsville, AL, 35899, USA
| | - Gordon G MacGregor
- Department of Biological Sciences, University of Alabama in Huntsville, SST 361, 301 Sparkman Dr, Huntsville, AL, 35899, USA.
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165
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Kwon J, Kim M, Park H, Kang BM, Jo Y, Kim JH, James O, Yun SH, Kim SG, Suh M, Choi M. Label-free nanoscale optical metrology on myelinated axons in vivo. Nat Commun 2017; 8:1832. [PMID: 29184114 PMCID: PMC5705720 DOI: 10.1038/s41467-017-01979-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 10/29/2017] [Indexed: 01/10/2023] Open
Abstract
In the mammalian nervous system, myelin provides electrical insulation for the neural circuit by forming a highly organized, multilayered thin film around the axon fibers. Here, we investigate the spectral reflectance from this subcellular nanostructure and devise a new label-free technique based on a spectroscopic analysis of reflected light, enabling nanoscale imaging of myelinated axons in their natural living state. Using this technique, we demonstrate three-dimensional mapping of the axon diameter and sensing of dynamic changes in the substructure of myelin at nanoscale. We further reveal the prevalence of axon bulging in the brain cortex in vivo after mild compressive trauma. Our novel tool opens new avenues of investigation by creating unprecedented access to the nanostructural dynamics of live myelinated axons in health and disease.
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Affiliation(s)
- Junhwan Kwon
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | | | - Hyejin Park
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
- Department of Biological Science, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Bok-Man Kang
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Yongjae Jo
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Jae-Hwan Kim
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Oliver James
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
| | | | - Seong-Gi Kim
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Minah Suh
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Myunghwan Choi
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea.
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea.
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166
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Thapaliya K, Vegh V, Bollmann S, Barth M. Assessment of microstructural signal compartments across the corpus callosum using multi-echo gradient recalled echo at 7 T. Neuroimage 2017; 182:407-416. [PMID: 29183776 DOI: 10.1016/j.neuroimage.2017.11.029] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 11/06/2017] [Accepted: 11/15/2017] [Indexed: 12/18/2022] Open
Abstract
Quantitative assessment of tissue microstructure is important in studying human brain diseases and disorders in which white matter is implicated, as it has been linked to demyelination, re-myelination, and axonal damage in clinical conditions. Ultra-high field magnetic resonance imaging data obtained using a multi-echo gradient echo sequence has been shown to contain information on myelin, axonal and extracellular compartments in white matter. In this study, we aimed to assess the sensitivity of a three-compartment model to estimate the variation of corresponding compartment parameters (water fraction, relaxation time and frequency shift) of the corpus callosum sub-regions, which are known to have different tissue structure. Additionally, we computed the g-ratio using myelin and axonal water fractions and performed a voxel-by-voxel analysis in the corpus callosum. Based on data acquired for ten participants, we show that the myelin compartment water fraction and T2∗ is consistent across the corpus callosum sub-regions, whilst myelin frequency shift varies. The results show that the variation in water fraction, T2∗ and frequency shift for the myelin signal compartment across the corpus callosum is smaller than for the axonal and extracellular signal compartments. The computed g-ratio was comparable to previously published studies in the corpus callosum. Our study suggests that a multi-echo GRE approach in vivo combined with a complex three-compartment model is sensitive to microstructural parameter variations across the human corpus callosum.
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Affiliation(s)
- Kiran Thapaliya
- Centre for Advanced Imaging, The University of Queensland, Queensland, Australia
| | - Viktor Vegh
- Centre for Advanced Imaging, The University of Queensland, Queensland, Australia
| | - Steffen Bollmann
- Centre for Advanced Imaging, The University of Queensland, Queensland, Australia
| | - Markus Barth
- Centre for Advanced Imaging, The University of Queensland, Queensland, Australia.
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167
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Heath F, Hurley SA, Johansen-Berg H, Sampaio-Baptista C. Advances in noninvasive myelin imaging. Dev Neurobiol 2017; 78:136-151. [PMID: 29082667 PMCID: PMC5813152 DOI: 10.1002/dneu.22552] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 09/18/2017] [Accepted: 10/24/2017] [Indexed: 12/11/2022]
Abstract
Myelin is important for the normal development and healthy function of the nervous system. Recent developments in MRI acquisition and tissue modeling aim to provide a better characterization and more specific markers for myelin. This allows for specific monitoring of myelination longitudinally and noninvasively in the healthy brain as well as assessment of treatment and intervention efficacy. Here, we offer a nontechnical review of MRI techniques developed to specifically monitor myelin such as magnetization transfer (MT) and myelin water imaging (MWI). We further summarize recent studies that employ these methods to measure myelin in relation to development and aging, learning and experience, and neuropathology and psychiatric disorders. © 2017 The Authors. Developmental Neurobiology Published by Wiley Periodicals, Inc. Develop Neurobiol 78: 136–151, 2018
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Affiliation(s)
- Florence Heath
- Oxford Centre for Functional MRI of the Brain, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, United Kingdom
| | - Samuel A Hurley
- Oxford Centre for Functional MRI of the Brain, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, United Kingdom.,Departments of Neuroscience and Radiology, 1111 Highland Ave, University of Wisconsin - Madison, Madison, Wisconsin, 53705
| | - Heidi Johansen-Berg
- Oxford Centre for Functional MRI of the Brain, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, United Kingdom
| | - Cassandra Sampaio-Baptista
- Oxford Centre for Functional MRI of the Brain, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, United Kingdom
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168
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Jia M, Li C, Zheng Y, Ding X, Chen M, Ding J, Du R, Lu M, Hu G. Leonurine Exerts Antidepressant-Like Effects in the Chronic Mild Stress-Induced Depression Model in Mice by Inhibiting Neuroinflammation. Int J Neuropsychopharmacol 2017; 20:886-895. [PMID: 29016795 PMCID: PMC5737563 DOI: 10.1093/ijnp/pyx062] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 07/17/2017] [Accepted: 07/20/2017] [Indexed: 01/01/2023] Open
Abstract
Background Leonurine is an active alkaloid that is extracted from Traditional Chinese Medicine Herba leonuri. Emerging evidence indicates that leonurine produces neuroprotective effects in ischemic stroke, Parkinson's disease, and Alzheimer's disease. However, the effect of leonurine in neuropsychiatric disorders, especially in major depression, remains unknown. Methods We used the chronic mild stress mouse model to explore the antidepressant effects of leonurine and the potential mechanisms. Behavioral tests including sucrose preference test, forced swimming test, and tail suspension test were taken to evaluate depression symptoms. Moreover, the contents of monoamine neurotransmitters in hippocampus and prefrontal cortex were measured by high-performance liquid chromatography. Neuronal morphology was detected by transmission electron microscopy. Results Administration of leonurine (60 mg/kg) for 4 weeks significantly alleviated depression-like behaviors of chronic mild stress mice, including increased sucrose preference and reduced immobility time in forced swimming test and tail suspension test. We further found that leonurine (60 mg/kg) effectively restored the levels of 5-hydroxytryptamine, noradrenaline, and dopamine in the hippocampus and prefrontal cortex of chronic mild stress mice, accompanied by amelioration of hippocampal neuronal damage. Furthermore, leonurine (60 mg/kg) significantly inhibited the production of proinflammatory cytokine interleukin-1β, interleukin-6 and TNF-α, and suppressed the nuclear factor kappa B signaling pathway. Conclusions These findings demonstrate that leonurine exerts antidepressant-like effects, which may be mediated, at least in part, by improving monoamine neurotransmitters and inhibiting neuroinflammation. Our study provides insight into the potential of leonurine in depression therapy.
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Affiliation(s)
- Miaomiao Jia
- Department of Pharmacology, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China (Drs Jia, Li, Zheng, X. Ding, and Hu); Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, Jiangsu, China (Drs Chen, J. Ding, Du, Lu, and Hu)
| | - Chenxin Li
- Department of Pharmacology, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China (Drs Jia, Li, Zheng, X. Ding, and Hu); Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, Jiangsu, China (Drs Chen, J. Ding, Du, Lu, and Hu)
| | - Ying Zheng
- Department of Pharmacology, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China (Drs Jia, Li, Zheng, X. Ding, and Hu); Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, Jiangsu, China (Drs Chen, J. Ding, Du, Lu, and Hu)
| | - Xiaojing Ding
- Department of Pharmacology, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China (Drs Jia, Li, Zheng, X. Ding, and Hu); Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, Jiangsu, China (Drs Chen, J. Ding, Du, Lu, and Hu)
| | - Meng Chen
- Department of Pharmacology, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China (Drs Jia, Li, Zheng, X. Ding, and Hu); Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, Jiangsu, China (Drs Chen, J. Ding, Du, Lu, and Hu)
| | - Jianhua Ding
- Department of Pharmacology, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China (Drs Jia, Li, Zheng, X. Ding, and Hu); Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, Jiangsu, China (Drs Chen, J. Ding, Du, Lu, and Hu)
| | - Renhong Du
- Department of Pharmacology, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China (Drs Jia, Li, Zheng, X. Ding, and Hu); Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, Jiangsu, China (Drs Chen, J. Ding, Du, Lu, and Hu)
| | - Ming Lu
- Department of Pharmacology, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China (Drs Jia, Li, Zheng, X. Ding, and Hu); Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, Jiangsu, China (Drs Chen, J. Ding, Du, Lu, and Hu)
| | - Gang Hu
- Department of Pharmacology, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China (Drs Jia, Li, Zheng, X. Ding, and Hu); Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, Jiangsu, China (Drs Chen, J. Ding, Du, Lu, and Hu)
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169
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Kaller MS, Lazari A, Blanco-Duque C, Sampaio-Baptista C, Johansen-Berg H. Myelin plasticity and behaviour-connecting the dots. Curr Opin Neurobiol 2017; 47:86-92. [PMID: 29054040 PMCID: PMC5844949 DOI: 10.1016/j.conb.2017.09.014] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 08/29/2017] [Accepted: 09/21/2017] [Indexed: 12/31/2022]
Abstract
Changes in white matter and myelin are associated with learning during adulthood across species. The causal link between myelin plasticity and behaviour remains elusive. Preventing the differentiation of new OLs can impair learning within the first few hours. Myelin remodelling may occur through many different routes and mechanism. The functional arrangement of myelination along axons can be complex and diverse.
Myelin sheaths in the vertebrate nervous system enable faster impulse propagation, while myelinating glia provide vital support to axons. Once considered a static insulator, converging evidence now suggests that myelin in the central nervous system can be dynamically regulated by neuronal activity and continues to participate in nervous system plasticity beyond development. While the link between experience and myelination gains increased recognition, it is still unclear what role such adaptive myelination plays in facilitating and shaping behaviour. Additionally, fundamental mechanisms and principles underlying myelin remodelling remain poorly understood. In this review, we will discuss new insights into the link between myelin plasticity and behaviour, as well as mechanistic aspects of myelin remodelling that may help to elucidate this intriguing process.
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Affiliation(s)
- Malte Sebastian Kaller
- Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford OX1 2JD, United Kingdom.
| | - Alberto Lazari
- Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford OX1 2JD, United Kingdom
| | - Cristina Blanco-Duque
- Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford OX1 2JD, United Kingdom
| | - Cassandra Sampaio-Baptista
- Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford OX1 2JD, United Kingdom
| | - Heidi Johansen-Berg
- Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford OX1 2JD, United Kingdom
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170
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Jung W, Lee J, Shin HG, Nam Y, Zhang H, Oh SH, Lee J. Whole brain g-ratio mapping using myelin water imaging (MWI) and neurite orientation dispersion and density imaging (NODDI). Neuroimage 2017; 182:379-388. [PMID: 28962901 DOI: 10.1016/j.neuroimage.2017.09.053] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Revised: 08/23/2017] [Accepted: 09/24/2017] [Indexed: 10/18/2022] Open
Abstract
MR g-ratio, which measures the ratio of the aggregate volume of axons to that of fibers in a voxel, is a potential biomarker for white matter microstructures. In this study, a new approach for acquiring an in-vivo whole human brain g-ratio map is proposed. To estimate the g-ratio, myelin volume fraction and axonal volume fraction are acquired using multi-echo gradient echo myelin water imaging (GRE-MWI) and neurite orientation dispersion and density imaging (NODDI), respectively. In order to translate myelin water fraction measured in GRE-MWI into myelin volume fraction, a new scaling procedure is proposed and validated. This scaling approach utilizes geometric measures of myelin structure and, therefore, provides robustness over previous methods. The resulting g-ratio map reveals an expected range of g-ratios (0.71-0.85 in major fiber bundles) with a small inter-subject coefficient of variance (less than 2%). Additionally, a few fiber bundles (e.g. cortico-spinal tract and optic radiation) show different constituents of myelin volume fraction and axonal volume fraction, indicating potentials to utilize the measures for deciphering fiber tracking.
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Affiliation(s)
- Woojin Jung
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, South Korea
| | - Jingu Lee
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, South Korea
| | - Hyeong-Geol Shin
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, South Korea
| | - Yoonho Nam
- Department of Radiology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, South Korea
| | - Hui Zhang
- Department of Computer Science & Centre for Medical Image Computing, University College London, London, United Kingdom
| | - Se-Hong Oh
- Division of Biomedical Engineering, Hankuk University of Foreign Studies, Yongin, South Korea
| | - Jongho Lee
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, South Korea.
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171
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Mancini M, Giulietti G, Dowell N, Spanò B, Harrison N, Bozzali M, Cercignani M. Introducing axonal myelination in connectomics: A preliminary analysis of g-ratio distribution in healthy subjects. Neuroimage 2017; 182:351-359. [PMID: 28917698 DOI: 10.1016/j.neuroimage.2017.09.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 08/16/2017] [Accepted: 09/08/2017] [Indexed: 12/21/2022] Open
Abstract
Microstructural imaging and connectomics are two research areas that hold great potential for investigating brain structure and function. Combining these two approaches can lead to a better and more complete characterization of the brain as a network. The aim of this work is characterizing the connectome from a novel perspective using the myelination measure given by the g-ratio. The g-ratio is the ratio of the inner to the outer diameters of a myelinated axon, whose aggregated value can now be estimated in vivo using MRI. In two different datasets of healthy subjects, we reconstructed the structural connectome and then used the g-ratio estimated from diffusion and magnetization transfer data to characterize the network structure. Significant characteristics of g-ratio weighted graphs emerged. First, the g-ratio distribution across the edges of the graph did not show the power-law distribution observed using the number of streamlines as a weight. Second, connections involving regions related to motor and sensory functions were the highest in myelin content. We also observed significant differences in terms of the hub structure and the rich-club organization suggesting that connections involving hub regions present higher myelination than peripheral connections. Taken together, these findings offer a characterization of g-ratio distribution across the connectome in healthy subjects and lay the foundations for further investigating plasticity and pathology using a similar approach.
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Affiliation(s)
- Matteo Mancini
- Neuroimaging Laboratory, Santa Lucia Foundation, Rome, Italy; Department of Neuroscience, Brighton and Sussex Medical School, University of Sussex, Brighton, UK.
| | | | - Nicholas Dowell
- Department of Neuroscience, Brighton and Sussex Medical School, University of Sussex, Brighton, UK
| | - Barbara Spanò
- Neuroimaging Laboratory, Santa Lucia Foundation, Rome, Italy
| | - Neil Harrison
- Department of Neuroscience, Brighton and Sussex Medical School, University of Sussex, Brighton, UK
| | - Marco Bozzali
- Neuroimaging Laboratory, Santa Lucia Foundation, Rome, Italy; Department of Neuroscience, Brighton and Sussex Medical School, University of Sussex, Brighton, UK
| | - Mara Cercignani
- Neuroimaging Laboratory, Santa Lucia Foundation, Rome, Italy; Department of Neuroscience, Brighton and Sussex Medical School, University of Sussex, Brighton, UK
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172
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Campbell JSW, Leppert IR, Narayanan S, Boudreau M, Duval T, Cohen-Adad J, Pike GB, Stikov N. Promise and pitfalls of g-ratio estimation with MRI. Neuroimage 2017; 182:80-96. [PMID: 28822750 DOI: 10.1016/j.neuroimage.2017.08.038] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 07/28/2017] [Accepted: 08/12/2017] [Indexed: 12/13/2022] Open
Abstract
The fiber g-ratio is the ratio of the inner to the outer diameter of the myelin sheath of a myelinated axon. It has a limited dynamic range in healthy white matter, as it is optimized for speed of signal conduction, cellular energetics, and spatial constraints. In vivo imaging of the g-ratio in health and disease would greatly increase our knowledge of the nervous system and our ability to diagnose, monitor, and treat disease. MRI based g-ratio imaging was first conceived in 2011, and expanded to be feasible in full brain white matter with preliminary results in 2013. This manuscript reviews the growing g-ratio imaging literature and speculates on future applications. It details the methodology for imaging the g-ratio with MRI, and describes the known pitfalls and challenges in doing so.
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Affiliation(s)
- Jennifer S W Campbell
- Montreal Neurological Institute, McGill University, Montreal, QC, Canada; NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montréal, QC, Canada.
| | - Ilana R Leppert
- Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Sridar Narayanan
- Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Mathieu Boudreau
- Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Tanguy Duval
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montréal, QC, Canada
| | - Julien Cohen-Adad
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montréal, QC, Canada; Functional Neuroimaging Unit, CRIUGM, Université de Montréal, Montréal, QC, Canada
| | | | - Nikola Stikov
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montréal, Montréal, QC, Canada; Montreal Heart Institute, Université de Montréal, Montréal, QC, Canada
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173
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Gloviczki B, Török DG, Márton G, Gál L, Bodzay T, Pintér S, Nógrádi A. Delayed Spinal Cord–Brachial Plexus Reconnection after C7 Ventral Root Avulsion: The Effect of Reinnervating Motoneurons Rescued by Riluzole Treatment. J Neurotrauma 2017; 34:2364-2374. [DOI: 10.1089/neu.2016.4754] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Affiliation(s)
- Balázs Gloviczki
- Laboratory of Neural Regeneration, Department of Anatomy, Histology, and Embryology, University of Szeged, Szeged, Hungary
- Department of Traumatology, Sándor Péterfy Hospital, Budapest, Hungary
| | - Dénes G. Török
- Laboratory of Neural Regeneration, Department of Anatomy, Histology, and Embryology, University of Szeged, Szeged, Hungary
- Department of Traumatology, Albert Szent-Györgyi Clinical Centre, University of Szeged, Szeged, Hungary
| | - Gábor Márton
- Laboratory of Neural Regeneration, Department of Anatomy, Histology, and Embryology, University of Szeged, Szeged, Hungary
| | - László Gál
- Laboratory of Neural Regeneration, Department of Anatomy, Histology, and Embryology, University of Szeged, Szeged, Hungary
- Department of Neurophysiology, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Tamás Bodzay
- Department of Traumatology, Sándor Péterfy Hospital, Budapest, Hungary
| | - Sándor Pintér
- Laboratory of Neural Regeneration, Department of Anatomy, Histology, and Embryology, University of Szeged, Szeged, Hungary
- Department of Traumatology, Albert Szent-Györgyi Clinical Centre, University of Szeged, Szeged, Hungary
| | - Antal Nógrádi
- Laboratory of Neural Regeneration, Department of Anatomy, Histology, and Embryology, University of Szeged, Szeged, Hungary
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174
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Sharma P, Wright DK, Johnston LA, Powell KL, Wlodek ME, Shultz SR, O'Brien TJ, Gilby KL. Differences in white matter structure between seizure prone (FAST) and seizure resistant (SLOW) rat strains. Neurobiol Dis 2017; 104:33-40. [DOI: 10.1016/j.nbd.2017.04.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 03/20/2017] [Accepted: 04/27/2017] [Indexed: 02/09/2023] Open
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175
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Berman S, West KL, Does MD, Yeatman JD, Mezer AA. Evaluating g-ratio weighted changes in the corpus callosum as a function of age and sex. Neuroimage 2017; 182:304-313. [PMID: 28673882 DOI: 10.1016/j.neuroimage.2017.06.076] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Revised: 06/26/2017] [Accepted: 06/27/2017] [Indexed: 11/16/2022] Open
Abstract
Recent years have seen a growing interest in relating MRI measurements to the structural-biophysical properties of white matter fibers. The fiber g-ratio, defined as the ratio between the inner and outer radii of the axon myelin sheath, is an important structural property of white matter, affecting signal conduction. Recently proposed modeling methods that use a combination of quantitative-MRI signals, enable a measurement of the fiber g-ratio in vivo. Here we use an MRI-based g-ratio estimation to observe the variance of the g-ratio within the corpus callosum, and evaluate sex and age related differences. To estimate the g-ratio we used a model (Stikov et al., 2011; Duval et al., 2017) based on two different WM microstructure parameters: the relative amounts of myelin (myelin volume fraction, MVF) and fibers (fiber volume fraction, FVF) in a voxel. We derived the FVF from the fractional anisotropy (FA), and estimated the MVF by using the lipid and macromolecular tissue volume (MTV), calculated from the proton density (Mezer et al., 2013). In comparison to other methods of estimating the MVF, MTV represents a stable parameter with a straightforward route of acquisition. To establish our model, we first compared histological MVF measurements (West et al., 2016) with the MRI derived MTV. We then implemented our model on a large database of 92 subjects (44 males), aged 7 to 81, in order to evaluate age and sex related changes within the corpus callosum. Our results show that the MTV provides a good estimation of MVF for calculating g-ratio, and produced values from the corpus callosum that correspond to those found in animals ex vivo and are close to the theoretical optimum, as well as to published in vivo data. Our results demonstrate that the MTV derived g-ratio provides a simple and reliable in vivo g-ratio-weighted (GR*) measurement in humans. In agreement with theoretical predictions, and unlike other tissue parameters measured with MRI, the g-ratio estimations were found to be relatively stable with age, and we found no support for a significant sexual dimorphism with age.
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Affiliation(s)
- Shai Berman
- The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Kathryn L West
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA; Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
| | - Mark D Does
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA; Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
| | - Jason D Yeatman
- Institute for Learning & Brain Sciences and Department of Speech & Hearing Sciences, University of Washington, Seattle, WA, USA
| | - Aviv A Mezer
- The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel.
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176
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Lin M, He H, Tong Q, Ding Q, Yan X, Feiweier T, Zhong J. Effect of myelin water exchange on DTI-derived parameters in diffusion MRI: Elucidation of TE dependence. Magn Reson Med 2017; 79:1650-1660. [PMID: 28656631 DOI: 10.1002/mrm.26812] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Revised: 05/09/2017] [Accepted: 06/03/2017] [Indexed: 12/19/2022]
Abstract
PURPOSE Water exchange exists between different neuronal compartments of brain tissue but is often ignored in most diffusion models. The goal of the current study was to demonstrate the dependence of diffusion measurements on echo time (TE) in the human brain and to investigate the underlying effects of myelin water exchange. METHODS Five healthy subjects were examined with single-shot pulsed-gradient spin-echo echo-planar imaging with fixed duration (δ) and separation (Δ) of diffusion gradient pulses and a set of varying TEs. The effects of water exchange and intrinsic T2 difference in cellular environments were investigated with Monte Carlo simulations. RESULTS Both in vivo measurements and simulations showed that fractional anisotropy (FA) and axial diffusivity (AD) had positive correlations with TE, while radial diffusivity (RD) showed a negative correlation, which is consistent with a previous study. The simulation results further indicated the sensitivity of TE dependence to the change of g-ratio. CONCLUSION The exchange between myelin and intra/extra-axonal water pools often plays a non-negligible role in the observed TE dependence of diffusion parameters, which may accompany or alter the effect of intrinsic T2 in causing such dependence. The TE dependence may potentially serve as a biomarker for demyelination processes (e.g., in multiple sclerosis and Alzheimer's disease). Magn Reson Med 79:1650-1660, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Mu Lin
- Center for Brain Imaging Science and Technology, Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering and Instrumental Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Hongjian He
- Center for Brain Imaging Science and Technology, Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering and Instrumental Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Qiqi Tong
- Center for Brain Imaging Science and Technology, Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering and Instrumental Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Qiuping Ding
- Center for Brain Imaging Science and Technology, Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering and Instrumental Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Xu Yan
- MR Collaboration NE Asia, Siemens Healthcare, Shanghai, China
| | | | - Jianhui Zhong
- Center for Brain Imaging Science and Technology, Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering and Instrumental Science, Zhejiang University, Hangzhou, Zhejiang, China.,Department of Imaging Sciences, University of Rochester, Rochester, New York, USA
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177
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Resistance wheel exercise from mid-life has minimal effect on sciatic nerves from old mice in which sarcopenia was prevented. Biogerontology 2017; 18:769-790. [PMID: 28597407 DOI: 10.1007/s10522-017-9714-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 05/31/2017] [Indexed: 12/16/2022]
Abstract
The ability of resistance exercise, initiated from mid-life, to prevent age-related changes in old sciatic nerves, was investigated in male and female C57BL/6J mice. Aging is associated with cellular changes in old sciatic nerves and also loss of skeletal muscle mass and function (sarcopenia). Mature adult mice aged 15 months (M) were subjected to increasing voluntary resistance wheel exercise (RWE) over a period of 8 M until 23 M of age. This prevented sarcopenia in the old 23 M aged male and female mice. Nerves of control sedentary (SED) males at 3, 15 and 23 M of age, showed a decrease in the myelinated axon numbers at 15 and 23 M, a decreased g-ratio and a significantly increased proportion of myelinated nerves containing electron-dense aggregates at 23 M. Myelinated axon and nerve diameter, and axonal area, were increased at 15 M compared with 3 and 23 M. Exercise increased myelinated nerve profiles containing aggregates at 23 M. S100 protein, detected with immunoblotting was increased in sciatic nerves of 23 M old SED females, but not males, compared with 15 M, with no effect of exercise. Other neuronal proteins showed no significant alterations with age, gender or exercise. Overall the RWE had no cellular impact on the aging nerves, apart from an increased number of old nerves containing aggregates. Thus the relationship between cellular changes in aging nerves, and their sustained capacity for stimulation of old skeletal muscles to help maintain healthy muscle mass in response to exercise remains unclear.
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178
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Jang YJ, Lee JH, Seo TB, Oh SH. Lidocaine/multivalent ion complex as a potential strategy for prolonged local anesthesia. Eur J Pharm Biopharm 2017; 115:113-121. [DOI: 10.1016/j.ejpb.2017.02.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 01/31/2017] [Accepted: 02/13/2017] [Indexed: 01/17/2023]
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179
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Models for Studying Myelination, Demyelination and Remyelination. Neuromolecular Med 2017; 19:181-192. [DOI: 10.1007/s12017-017-8442-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 05/17/2017] [Indexed: 10/19/2022]
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180
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Adipose-Derived Stem Cells Enhance Axonal Regeneration through Cross-Facial Nerve Grafting in a Rat Model of Facial Paralysis. Plast Reconstr Surg 2017; 138:387-396. [PMID: 27465163 DOI: 10.1097/prs.0000000000002351] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND Cross-face nerve grafting combined with functional muscle transplantation has become the standard in reconstructing an emotionally controlled smile in complete irreversible facial palsy. However, the efficacy of this procedure depends on the ability of regenerating axons to breach two nerve coaptations and reinnervate endplates in denervated muscle. The current study tested the hypothesis that adipose-derived stem cells would enhance axonal regeneration through a cross-facial nerve graft and thereby enhance recovery of the facial nerve function. METHODS Twelve rats underwent transection of the right facial nerve, and cross-facial nerve grafting using the sciatic nerve as an interpositional graft, with coaptations to the ipsilateral and contralateral buccal branches, was carried out. Rats were divided equally into two groups: a grafted but nontreated control group and a grafted and adipose-derived stem cell-treated group. Three months after surgery, biometric and electrophysiologic assessments of vibrissae movements were performed. Histologically, the spectra of fiber density, myelin sheath thickness, fiber diameter, and g ratio of the nerve were analyzed. Immunohistochemical staining was performed for the evaluation of acetylcholine in the neuromuscular junctions. RESULTS The data from the biometric and electrophysiologic analysis of vibrissae movements, immunohistochemical analysis, and histologic assessment of the nerve showed that adipose-derived stem cells significantly enhanced axonal regeneration through the graft. CONCLUSION These observations suggest that adipose-derived stem cells could be a clinically translatable route toward new methods to enhance recovery after cross-facial nerve grafting.
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181
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Xu T, Foxley S, Kleinnijenhuis M, Chen WC, Miller KL. The effect of realistic geometries on the susceptibility-weighted MR signal in white matter. Magn Reson Med 2017; 79:489-500. [PMID: 28394030 PMCID: PMC6585669 DOI: 10.1002/mrm.26689] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 02/05/2017] [Accepted: 03/04/2017] [Indexed: 12/15/2022]
Abstract
PURPOSE To investigate the effect of realistic microstructural geometry on the susceptibility-weighted MR signal in white matter (WM), with application to demyelination. METHODS Previous work has modeled susceptibility-weighted signals under the assumption that axons are cylindrical. In this study, we explored the implications of this assumption by considering the effect of more realistic geometries. A three-compartment WM model incorporating relevant properties based on the literature was used to predict the MR signal. Myelinated axons were modeled with several cross-sectional geometries of increasing realism: nested circles, warped/elliptical circles, and measured axonal geometries from electron micrographs. Signal simulations from the different microstructural geometries were compared with measured signals from a cuprizone mouse model with varying degrees of demyelination. RESULTS Simulation results suggest that axonal geometry affects the MR signal. Predictions with realistic models were significantly different compared with circular models under the same microstructural tissue properties, for simulations with and without diffusion. CONCLUSION The geometry of axons affects the MR signal significantly. Literature estimates of myelin susceptibility, which are based on fitting biophysical models to the MR signal, are likely to be biased by the assumed geometry, as will any derived microstructural properties. Magn Reson Med 79:489-500, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Tianyou Xu
- Oxford Centre for Functional MRI of the Brain, University of Oxford, Oxford, United Kingdom
| | - Sean Foxley
- Oxford Centre for Functional MRI of the Brain, University of Oxford, Oxford, United Kingdom
| | - Michiel Kleinnijenhuis
- Oxford Centre for Functional MRI of the Brain, University of Oxford, Oxford, United Kingdom
| | - Way Cherng Chen
- Oxford Centre for Functional MRI of the Brain, University of Oxford, Oxford, United Kingdom.,Singapore Bioimaging Consortium, A*STAR, Singapore
| | - Karla L Miller
- Oxford Centre for Functional MRI of the Brain, University of Oxford, Oxford, United Kingdom
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182
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Chung T, Park JS, Kim S, Montes N, Walston J, Höke A. Evidence for dying-back axonal degeneration in age-associated skeletal muscle decline. Muscle Nerve 2017; 55:894-901. [PMID: 27464347 DOI: 10.1002/mus.25267] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Revised: 07/21/2016] [Accepted: 07/26/2016] [Indexed: 11/12/2022]
Abstract
INTRODUCTION Age-associated muscle strength decline is a major contributing factor to increased late-life functional decline and comorbidity, and is strongly associated with early mortality. Although all parts of the neuromuscular system seem to be affected by aging, dying-back of motor axons likely plays a major role. METHODS We compared the degeneration in ventral roots and neuromuscular junction denervation in young and aged mice and correlated the findings with strength and electrophysiological measures. RESULTS With normal aging, there is little decline in motor axon numbers in the ventral roots, but the neuromuscular junctions show marked partial denervation that is associated with increased jitter on stimulated single fiber electromyography and a decrease in muscle strength. CONCLUSIONS These findings suggest that dying-back axonal degeneration may be partially responsible for the electrophysiological and strength changes observed with aging. Muscle Nerve 55: 894-901, 2017.
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Affiliation(s)
- Tae Chung
- Department of Physical Medicine and Rehabilitation, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Jae Sung Park
- Department of Neurology, Johns Hopkins School of Medicine, Baltimore, Maryland, 21205, USA.,Department of Physical Education, Kongju National University, Gongju, Republic of Korea
| | - Sangri Kim
- Department of Neurology, Johns Hopkins School of Medicine, Baltimore, Maryland, 21205, USA
| | - Nataly Montes
- Department of Physical Medicine and Rehabilitation, VA Caribbean Healthcare System, San Juan, Puerto Rico
| | - Jeremy Walston
- Department of Medicine, Johns Hopkins, Baltimore, Maryland, USA
| | - Ahmet Höke
- Department of Neurology, Johns Hopkins School of Medicine, Baltimore, Maryland, 21205, USA
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183
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Sasaki RT, Grossi NG, Zeni RT, Saez DM, Gonçalves ID, da Silva MCP. Effect of Laser Photobiomodulation with Gradual or Constant Doses in the Regeneration of Rats' Mental Nerve After Lesion by Compression. Photomed Laser Surg 2017; 35:408-414. [PMID: 28358662 DOI: 10.1089/pho.2016.4210] [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] [Indexed: 01/12/2023] Open
Abstract
OBJECTIVE Assess morphologically the efficacy of constant dose (CD) or gradual dose (GD) in photobiomodulation therapy (PBMT) during the regeneration process of rats' mental nerve after compression lesion. MATERIALS AND METHODS Forty-eight male Wistar rats were used and divided into four groups (n = 12): negative control (NC): lesion by compression; positive control (PC): no lesion; GD: lesion by compression and PBMT with GD; and CD: lesion by compression and PBMT with CD. One day after the surgery, the groups GD and CD underwent PBMT daily in three equidistant points around the incision area. The parameters were wavelength of 808 nm, 100 mW, CD received treatment with 120 J/cm2, while GD underwent the protocol of application: 1st and 4th sessions: 80 J/cm2; 5th to 8th sessions: 90 J/cm2; 9th to 12th sessions: 100 J/cm2; 13th to 16th sessions: 110 J/cm2; and 17th to 20th sessions: 120 J/cm2. Euthanasias were performed at 3, 7, 14, and 21 days. Qualitative and quantitative analysis of the mental nerves were performed with ANOVA (analysis of variance) and Tukey tests (p ≤ 0.05). RESULTS It was observed that PBMT was able to accelerate the process of nerve regeneration presenting an increase in the number of myelinated fibers starting at 14 days of treatment for groups CD and GD, and at 21 days they were similar to PC. It was observed a better lamellar organization of myelin sheath at 7 days for GD and at 14 days for CD, similar to PC. Both GD and CD presented significant differences compared to NC and PC for thickness of the myelin sheath, outer perimeter, internal area, and number of myelin fibers. CONCLUSIONS PBMT presented positive effect on the regeneration of nerve starting at 14 days, and after 21 days there was no difference between GD and CD.
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Affiliation(s)
- Robson Tetsuo Sasaki
- 1 Department of Morphology and Genetics, Federal University of São Paulo (EPM/UNIFESP) , São Paulo, Brazil
| | - Natália Garrido Grossi
- 2 Department of Human Anatomy, São Leopoldo Mandic Institute and Research Center , Campinas, Brazil
| | - Rafael Tardeli Zeni
- 2 Department of Human Anatomy, São Leopoldo Mandic Institute and Research Center , Campinas, Brazil
| | - Daniel Martinez Saez
- 1 Department of Morphology and Genetics, Federal University of São Paulo (EPM/UNIFESP) , São Paulo, Brazil
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184
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Abstract
Quantitative magnetic resonance imaging can be combined with advanced biophysical models to measure microstructural features of white matter. Non-invasive microstructural imaging has the potential to revolutionize neuroscience, and acquiring these measures in clinically feasible times would greatly improve patient monitoring and clinical studies of drug efficacy. However, a good understanding of microstructural imaging techniques is essential to set realistic expectations and to prevent over-interpretation of results. This review explains the methodology behind microstructural modeling and imaging, and gives an overview of the breakthroughs and challenges associated with it.
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185
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Koestinger G, Martin KAC, Roth S, Rusch ES. Synaptic connections formed by patchy projections of pyramidal cells in the superficial layers of cat visual cortex. Brain Struct Funct 2017; 222:3025-3042. [PMID: 28243762 PMCID: PMC5585309 DOI: 10.1007/s00429-017-1384-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2016] [Accepted: 02/07/2017] [Indexed: 11/30/2022]
Abstract
The present study is the first to describe quantitatively the patterns of synaptic connections made by the patchy network of pyramidal cell axons in the superficial layers of cat V1 in relation to the orientation map. Intrinsic signal imaging of the orientation map was combined with 3D morphological reconstructions of physiologically-characterized neurons at light and electron microscope levels. A Similarity Index (SI) expressed the similarity of the orientation domain of a given bouton cluster to that of its parent dendritic tree. Six pyramidal cells whose axons had a wide range of SIs were examined. Boutons were sampled from five local and five distal clusters, and from the linear segments that link the clusters. The synaptic targets were reconstructed by serial section electron microscopy. Of the 233 synapses examined, 182 synapses were formed with spiny neurons, the remainder with smooth neurons. The proportion of smooth neurons that were synaptic targets varied greatly (from 0 to 50%) between the cluster samples, but was not correlated with the SI. The postsynaptic density sizes were similar for synapses in local and distal clusters, regardless of their SI. This heterogeneity in the synaptic targets of single cells within the superficial layers is a network feature well-suited for context-dependent processing.
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Affiliation(s)
- German Koestinger
- Institute of Neuroinformatics, UZH/ETH, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Kevan A C Martin
- Institute of Neuroinformatics, UZH/ETH, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Stephan Roth
- Institute of Neuroinformatics, UZH/ETH, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Elisha S Rusch
- Institute of Neuroinformatics, UZH/ETH, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
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186
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Mingasson T, Duval T, Stikov N, Cohen-Adad J. AxonPacking: An Open-Source Software to Simulate Arrangements of Axons in White Matter. Front Neuroinform 2017; 11:5. [PMID: 28197091 PMCID: PMC5281605 DOI: 10.3389/fninf.2017.00005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 01/13/2017] [Indexed: 11/24/2022] Open
Abstract
HIGHLIGHTSAxonPacking: Open-source software for simulating white matter microstructure. Validation on a theoretical disk packing problem. Reproducible and stable for various densities and diameter distributions. Can be used to study interplay between myelin/fiber density and restricted fraction.
Quantitative Magnetic Resonance Imaging (MRI) can provide parameters that describe white matter microstructure, such as the fiber volume fraction (FVF), the myelin volume fraction (MVF) or the axon volume fraction (AVF) via the fraction of restricted water (fr). While already being used for clinical application, the complex interplay between these parameters requires thorough validation via simulations. These simulations required a realistic, controlled and adaptable model of the white matter axons with the surrounding myelin sheath. While there already exist useful algorithms to perform this task, none of them combine optimisation of axon packing, presence of myelin sheath and availability as free and open source software. Here, we introduce a novel disk packing algorithm that addresses these issues. The performance of the algorithm is tested in term of reproducibility over 50 runs, resulting density, and stability over iterations. This tool was then used to derive multiple values of FVF and to study the impact of this parameter on fr and MVF in light of the known microstructure based on histology sample. The standard deviation of the axon density over runs was lower than 10−3 and the expected hexagonal packing for monodisperse disks was obtained with a density close to the optimal density (obtained: 0.892, theoretical: 0.907). Using an FVF ranging within [0.58, 0.82] and a mean inter-axon gap ranging within [0.1, 1.1] μm, MVF ranged within [0.32, 0.44] and fr ranged within [0.39, 0.71], which is consistent with the histology. The proposed algorithm is implemented in the open-source software AxonPacking (https://github.com/neuropoly/axonpacking) and can be useful for validating diffusion models as well as for enabling researchers to study the interplay between microstructure parameters when evaluating qMRI methods.
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Affiliation(s)
- Tom Mingasson
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique MontrealMontreal, QC, Canada; Signal Processing Department, École Centrale de NantesNantes, France
| | - Tanguy Duval
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal Montreal, QC, Canada
| | - Nikola Stikov
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique MontrealMontreal, QC, Canada; Department of Biomedical Engineering, Montreal Heart Institute, University of MontrealMontreal, QC, Canada
| | - Julien Cohen-Adad
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique MontrealMontreal, QC, Canada; Functional Neuroimaging Unit, Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal (CRIUGM), Université de MontréalMontreal, QC, Canada
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187
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Duval T, Le Vy S, Stikov N, Campbell J, Mezer A, Witzel T, Keil B, Smith V, Wald LL, Klawiter E, Cohen-Adad J. g-Ratio weighted imaging of the human spinal cord in vivo. Neuroimage 2017; 145:11-23. [PMID: 27664830 PMCID: PMC5179300 DOI: 10.1016/j.neuroimage.2016.09.018] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 08/22/2016] [Accepted: 09/08/2016] [Indexed: 12/13/2022] Open
Abstract
The fiber g-ratio is defined as the ratio of the inner to the outer diameter of the myelin sheath. This ratio provides a measure of the myelin thickness that complements axon morphology (diameter and density) for assessment of demyelination in diseases such as multiple sclerosis. Previous work has shown that an aggregate g-ratio map can be computed using a formula that combines axon and myelin density measured with quantitative MRI. In this work, we computed g-ratio weighted maps in the cervical spinal cord of nine healthy subjects. We utilized the 300mT/m gradients from the CONNECTOM scanner to estimate the fraction of restricted water (fr) with high accuracy, using the CHARMED model. Myelin density was estimated using the lipid and macromolecular tissue volume (MTV) method, derived from normalized proton density (PD) mapping. The variability across spinal level, laterality and subject were assessed using a three-way ANOVA. The average g-ratio value obtained in the white matter was 0.76+/-0.03, consistent with previous histology work. Coefficients of variation of fr and MTV were respectively 4.3% and 13.7%. fr and myelin density were significantly different across spinal tracts (p=3×10-7 and 0.004 respectively) and were positively correlated in the white matter (r=0.42), suggesting shared microstructural information. The aggregate g-ratio did not show significant differences across tracts (p=0.6). This study suggests that fr and myelin density can be measured in vivo with high precision and that they can be combined to produce a g-ratio-weighted map robust to free water pool contamination from cerebrospinal fluid or veins. Potential applications include the study of early demyelination in multiple sclerosis, and the quantitative assessment of remyelination drugs.
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Affiliation(s)
- T Duval
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada
| | - S Le Vy
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada; Functional Neuroimaging Unit, CRIUGM, Université de Montréal, Montréal, QC, Canada
| | - N Stikov
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada; Montreal Heart Institute, Montreal, QC, Canada
| | - J Campbell
- Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - A Mezer
- Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University of Jerusalem, Jerusalem, Israel
| | - T Witzel
- A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States
| | - B Keil
- A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States
| | - V Smith
- A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States
| | - L L Wald
- A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States
| | - E Klawiter
- A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States
| | - J Cohen-Adad
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada; Functional Neuroimaging Unit, CRIUGM, Université de Montréal, Montréal, QC, Canada.
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188
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Ziago EKM, Fazan VPS, Iyomasa MM, Sousa LG, Yamauchi PY, da Silva EA, Borie E, Fuentes R, Dias FJ. Analysis of the variation in low-level laser energy density on the crushed sciatic nerves of rats: a morphological, quantitative, and morphometric study. Lasers Med Sci 2017; 32:369-378. [PMID: 28063018 DOI: 10.1007/s10103-016-2126-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 12/06/2016] [Indexed: 01/17/2023]
Abstract
The objective of this study was to evaluate three energy densities of low-level laser therapy (LLLT, GaAlAs, 780 nm, 40 mW, 0.04 cm2) for the treatment of lesions to peripheral nerves using the sciatic nerve of rats injured via crushing model (15 kgf, 5.2 MPa). Thirty Wistar rats (♂, 200-250 g) were divided into five groups (n = 6): C-control, not injured, and irradiated; L0-injured nerve without irradiation; L4-injured nerve irradiated with LLLT 4 J/cm2 (0.16 J); L10-injured nerve irradiated with LLLT 10 J/cm2 (0.4 J); and L50-injured nerve irradiated with LLLT 50 J/cm2 (2 J). The animals were sacrificed 2 weeks after the injury via perfusion with glutaraldehyde (2.5%, 0.1 M sodium cacodylate buffer). The nerve tissue was embedded in historesin, cut (3 μm), mounted on slides, and stained (Sudan black and neutral red). The morphological and quantitative analysis (myelin and blood capillary densities) and morphometric parameters (maximum and minimum diameters of nerve fibers, axon diameter, G-ratio, myelin sheath thickness) were assessed using the ImageJ software. ANOVA (parametric) or Kruskal-Wallis (nonparametric) tests were used for the statistical analysis. Groups L0, L4, L10, and L50 exhibited diminished values of all the quantitative and morphometric parameters in comparison to the control group. The morphological, quantitative, and morphometric data revealed improvement after injury in groups L4, L10, and L50 (irradiated groups) compared to the injured-only group (L0); the best results, in general, were observed for the L10 group after 15 days of nerve injury.
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Affiliation(s)
| | | | | | - Luiz Gustavo Sousa
- School of Dentistry, University of São Paulo, USP, Ribeirão Preto, Brazil
| | | | | | - Eduardo Borie
- Department of Integral Dentistry, CICO - Research Centre in Dental Sciences, Dental School, Universidad de La Frontera, Temuco, Chile
| | - Ramón Fuentes
- Department of Integral Dentistry, CICO - Research Centre in Dental Sciences, Dental School, Universidad de La Frontera, Temuco, Chile
| | - Fernando José Dias
- School of Medicine, University of São Paulo, USP, Ribeirão Preto, Brazil. .,Department of Integral Dentistry, CICO - Research Centre in Dental Sciences, Dental School, Universidad de La Frontera, Temuco, Chile.
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189
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Singh S, Pelegri AA, Shreiber DI. Estimating axonal strain and failure following white matter stretch using contactin-associated protein as a fiduciary marker. J Biomech 2017; 51:32-41. [DOI: 10.1016/j.jbiomech.2016.11.055] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 11/16/2016] [Accepted: 11/19/2016] [Indexed: 01/08/2023]
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190
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Xiu Y, Cheng GH, Peng C, Wang Y, Li YD, Chao FL, Tang Y. Ultrastructural abnormalities and loss of myelinated fibers in the corpus callosum of demyelinated mice induced by cuprizone. J Neurosci Res 2016; 95:1677-1689. [DOI: 10.1002/jnr.23997] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 11/01/2016] [Accepted: 11/21/2016] [Indexed: 01/03/2023]
Affiliation(s)
- Yun Xiu
- Institute of Life Science; Chongqing Medical University; Chongqing People's Republic of China
- Department of Histology and Embryology, Faculty of Basic Medical Sciences; Chongqing Medical University; Chongqing People's Republic of China
| | - Guo-hua Cheng
- Department of Histology and Embryology, Faculty of Basic Medical Sciences; Chongqing Medical University; Chongqing People's Republic of China
| | - Chao Peng
- Department of Histology and Embryology, Faculty of Basic Medical Sciences; Chongqing Medical University; Chongqing People's Republic of China
| | - Yun Wang
- Department of Histology and Embryology, Faculty of Basic Medical Sciences; Chongqing Medical University; Chongqing People's Republic of China
| | - Yong-de Li
- Department of Histology and Embryology, Faculty of Basic Medical Sciences; Chongqing Medical University; Chongqing People's Republic of China
| | - Feng-lei Chao
- Department of Histology and Embryology, Faculty of Basic Medical Sciences; Chongqing Medical University; Chongqing People's Republic of China
| | - Yong Tang
- Department of Histology and Embryology, Faculty of Basic Medical Sciences; Chongqing Medical University; Chongqing People's Republic of China
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191
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Yoshizawa H, Senda D, Natori Y, Tanaka R, Mizuno H, Hayashi A. End-to-Side Neurorrhaphy as Schwann Cells Provider to Acellular Nerve Allograft and Its Suitable Application. PLoS One 2016; 11:e0167507. [PMID: 27907118 PMCID: PMC5132318 DOI: 10.1371/journal.pone.0167507] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 11/15/2016] [Indexed: 11/23/2022] Open
Abstract
Axonal regeneration relies on support from proliferating host Schwann cells (SCs), and previous studies on acellular nerve allografts (ANGs) suggest that axons can regenerate into ANGs within a limited distance. Numerous studies have demonstrated that the supplementation of ANGs with exogenous factors, such as cultured SCs, stem cells, and growth factors, promote nerve regeneration in ANGs. However, there are several problems associated with their utilization. In this study, we investigated whether end-to-side (ETS) neurorrhaphy, which is an axonal provider, could be useful as an SC provider to support axonal elongation in ANGs. We found that ETS neurorrhaphy effectively promoted SC migration into ANGs when an epineurium window combined with partial neurectomy was performed, and the effectiveness increased when it was applied bilaterally. When we transplanted ANGs containing migrated SCs via ETS neurorrhaphy (hybrid ANGs) to the nerve gap, hybrid ANGs increased the number of regenerated axons and facilitated rapid axonal elongation, particularly when ETS neurorrhaphy was applied to both edges of the graft. This approach may represent a novel application of ETS neurorrhaphy and lead to the development of hybrid ANGs, making ANGs more practical in a clinical setting.
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Affiliation(s)
- Hidekazu Yoshizawa
- Department of Plastic and Reconstructive Surgery, Juntendo University School of Medicine, Tokyo, Japan
| | - Daiki Senda
- Department of Plastic and Reconstructive Surgery, Juntendo University School of Medicine, Tokyo, Japan
| | - Yuhei Natori
- Department of Plastic and Reconstructive Surgery, Juntendo University School of Medicine, Tokyo, Japan
| | - Rica Tanaka
- Department of Plastic and Reconstructive Surgery, Juntendo University School of Medicine, Tokyo, Japan
| | - Hiroshi Mizuno
- Department of Plastic and Reconstructive Surgery, Juntendo University School of Medicine, Tokyo, Japan
| | - Ayato Hayashi
- Department of Plastic and Reconstructive Surgery, Juntendo University School of Medicine, Tokyo, Japan
- * E-mail:
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192
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Cercignani M, Giulietti G, Dowell NG, Gabel M, Broad R, Leigh PN, Harrison NA, Bozzali M. Characterizing axonal myelination within the healthy population: a tract-by-tract mapping of effects of age and gender on the fiber g-ratio. Neurobiol Aging 2016; 49:109-118. [PMID: 27792897 PMCID: PMC5156474 DOI: 10.1016/j.neurobiolaging.2016.09.016] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Revised: 09/22/2016] [Accepted: 09/22/2016] [Indexed: 11/21/2022]
Abstract
The g-ratio, equal to the ratio of the inner-to-outer diameter of a myelinated axon, is associated with the speed of conduction, and thus reflects axonal function and integrity. It is now possible to estimate an “aggregate” g-ratio in vivo using MRI. The aim of this study was to assess the variation of the MRI-derived fiber g-ratio in the brain of healthy individuals, and to characterize its variation across the lifespan. Thirty-eight healthy participants, aged between 20 and 76, were recruited. Whole-brain g-ratio maps were computed and analyzed voxel-wise. Median tract g-ratio values were also extracted. No significant effect of gender was found, whereas age was found to be significantly associated with the g-ratio within the white matter. The tract-specific analysis showed this relationship to follow a nearly-linear increase, although the slope appears to slow down slightly after the 6th decade of life. The most likely interpretation is a subtle but consistent reduction in myelin throughout adulthood, with the density of axons beginning to decrease between the 4th and 5th decade.
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Affiliation(s)
- Mara Cercignani
- Department of Neuroscience, Clinical Imaging Sciences Centre, Brighton and Sussex Medical School, University of Sussex, Brighton, East Sussex, UK; Neuroimaging Laboratory, Santa Lucia Foundation, Rome, Italy.
| | | | - Nick G Dowell
- Department of Neuroscience, Clinical Imaging Sciences Centre, Brighton and Sussex Medical School, University of Sussex, Brighton, East Sussex, UK
| | - Matt Gabel
- Department of Neuroscience, Clinical Imaging Sciences Centre, Brighton and Sussex Medical School, University of Sussex, Brighton, East Sussex, UK
| | - Rebecca Broad
- Neuroimaging Laboratory, Santa Lucia Foundation, Rome, Italy
| | - P Nigel Leigh
- Neuroimaging Laboratory, Santa Lucia Foundation, Rome, Italy
| | - Neil A Harrison
- Department of Neuroscience, Clinical Imaging Sciences Centre, Brighton and Sussex Medical School, University of Sussex, Brighton, East Sussex, UK
| | - Marco Bozzali
- Neuroimaging Laboratory, Santa Lucia Foundation, Rome, Italy
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193
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Kaizawa Y, Kakinoki R, Ikeguchi R, Ohta S, Noguchi T, Takeuchi H, Oda H, Yurie H, Matsuda S. A Nerve Conduit Containing a Vascular Bundle and Implanted With Bone Marrow Stromal Cells and Decellularized Allogenic Nerve Matrix. Cell Transplant 2016; 26:215-228. [PMID: 27657936 DOI: 10.3727/096368916x692951] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Cells, scaffolds, growth factors, and vascularity are essential for nerve regeneration. Previously, we reported that the insertion of a vascular bundle and the implantation of bone marrow-derived mesenchymal stem cells (BM-MSCs) into a nerve conduit promoted peripheral nerve regeneration. In this study, the efficacy of nerve conduits containing a vascular bundle, BM-MSCs, and thermally decellularized allogenic nerve matrix (DANM) was investigated using a rat sciatic nerve model with a 20-mm defect. Lewis rats were used as the sciatic nerve model and for the preparation of BM-MSCs, and Dark Agouti rats were used for the preparation of the DANM. The revascularization and the immunogenicity of the DANM were investigated histologically. The regeneration of nerves through nerve conduits containing vessels, BM-MSCs, and DANM (VBD group) was evaluated based on electrophysiological, morphometric, and reinnervated muscle weight measurements and compared with that of vessel-containing conduits that were implanted with BM-MSCs (VB group). The DANM that was implanted into vessel-containing tubes (VCTs) was revascularized by neovascular vessels that originated from the inserted vascular bundle 5-7 days after surgery. The number of CD8+ cells found in the DANM in the VCT was significantly smaller than that detected in the untreated allogenic nerve segment. The regenerated nerve in the VBD group was significantly superior to that in the VB group with regard to the amplitude of the compound muscle action potential detected in the pedal adductor muscle; the number, diameter, and myelin thickness of the myelinated axons; and the tibialis anterior muscle weight at 12 and 24 weeks. The additional implantation of the DANM into the BM-MSC-implanted VCT optimized the axonal regeneration through the conduit. Nerve conduits constructed with vascularity, cells, and scaffolds could be an effective strategy for the treatment of peripheral nerve injuries with significant segmental defects.
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194
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Olfactory ensheathing glia cell therapy and tubular conduit enhance nerve regeneration after mouse sciatic nerve transection. Brain Res 2016; 1650:243-251. [PMID: 27641994 DOI: 10.1016/j.brainres.2016.09.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 09/02/2016] [Accepted: 09/15/2016] [Indexed: 02/06/2023]
Abstract
The regenerative potential of the peripheral nervous system (PNS) is widely known, but functional recovery, particularly in humans, is seldom complete. Therefore, it is necessary to resort to strategies that induce or potentiate the PNS regeneration. Our main objective was to test the effectiveness of Olfactory Ensheathing Cells (OEC) transplantation into a biodegradable conduit as a therapeutic strategy to improve the repair outcome after nerve injury. Sciatic nerve transection was performed in C57BL/6 mice; proximal and distal stumps of the nerve were sutured into the collagen conduit. Two groups were analyzed: DMEM (acellular grafts) and OEC (1×105/2μL). Locomotor function was assessed weekly by Sciatic Function Index (SFI) and Global Mobility Test (GMT). After eight weeks the sciatic nerve was dissected for morphological analysis. Our results showed that the OEC group exhibited many clusters of regenerated nerve fibers, a higher number of myelinated fibers and myelin area compared to DMEM group. The G-ratio analysis of the OEC group showed significantly more fibers on the most suitable sciatic nerve G-ratio index. Motor recovery was accelerated in the OEC group. These data provide evidence that the OEC therapy can improve sciatic nerve functional and morphological recovery and can be potentially translated to the clinical setting.
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195
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Shrager P, Youngman M. Preferential conduction block of myelinated axons by nitric oxide. J Neurosci Res 2016; 95:1402-1414. [PMID: 27614087 DOI: 10.1002/jnr.23918] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 08/04/2016] [Accepted: 08/22/2016] [Indexed: 12/14/2022]
Abstract
Conduction block by nitric oxide (NO) was examined in myelinated and unmyelinated axons from both the central nervous system and peripheral nervous system. In rat vagus nerves, mouse optic nerves at P12-P23, adult and developing mouse sciatic nerves, and mouse spinal cords, myelinated fibers were preferentially blocked reversibly by concentrations of NO similar to those encountered in inflammatory lesions. The possibility that these differences between myelinated and unmyelinated axons are due to the normal developmental substitution of Na+ channel subtype Nav 1.6 for Nav 1.2 at nodes of Ranvier was tested by repeating experiments on mice null for Nav 1.6. Results were unchanged in this mutant. In shiverer optic nerve, which has only scattered regions with nodes of Ranvier, only the fastest component of the compound action potential was reduced. NO was compared with three other methods of blocking conduction: low Na+ , high K+ , and tetrodotoxin (TTX). In each of these three cases, unmyelinated axons lost conduction simultaneously with myelinated fibers. From changes in conduction velocity in myelinated axons as they were blocked, it was ascertained that NO acted most similarly to TTX. It was concluded that NO likely interacts with axonal Na+ channels through an intermediate that is associated with myelin. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Peter Shrager
- Department of Neuroscience, University of Rochester Medical Center, Rochester, New York
| | - Margaret Youngman
- Department of Neuroscience, University of Rochester Medical Center, Rochester, New York
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196
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Suzuki A, Iinuma M, Hayashi S, Sato Y, Azuma K, Kubo KY. Maternal chewing during prenatal stress ameliorates stress-induced hypomyelination, synaptic alterations, and learning impairment in mouse offspring. Brain Res 2016; 1651:36-43. [PMID: 27613358 DOI: 10.1016/j.brainres.2016.09.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 08/12/2016] [Accepted: 09/05/2016] [Indexed: 01/24/2023]
Abstract
Maternal chewing during prenatal stress attenuates both the development of stress-induced learning deficits and decreased cell proliferation in mouse hippocampal dentate gyrus. Hippocampal myelination affects spatial memory and the synaptic structure is a key mediator of neuronal communication. We investigated whether maternal chewing during prenatal stress ameliorates stress-induced alterations of hippocampal myelin and synapses, and impaired development of spatial memory in adult offspring. Pregnant mice were divided into control, stress, and stress/chewing groups. Stress was induced by placing mice in a ventilated restraint tube, and was initiated on day 12 of pregnancy and continued until delivery. Mice in the stress/chewing group were given a wooden stick to chew during restraint. In 1-month-old pups, spatial memory was assessed in the Morris water maze, and hippocampal oligodendrocytes and synapses in CA1 were assayed by immunohistochemistry and electron microscopy. Prenatal stress led to impaired learning ability, and decreased immunoreactivity of myelin basic protein (MBP) and 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) in the hippocampal CA1 in adult offspring. Numerous myelin sheath abnormalities were observed. The G-ratio [axonal diameter to axonal fiber diameter (axon plus myelin sheath)] was increased and postsynaptic density length was decreased in the hippocampal CA1 region. Maternal chewing during stress attenuated the prenatal stress-induced impairment of spatial memory, and the decreased MBP and CNPase immunoreactivity, increased G-ratios, and decreased postsynaptic-density length in the hippocampal CA1 region. These findings suggest that chewing during prenatal stress in dams could be an effective coping strategy to prevent hippocampal behavioral and morphologic impairments in their offspring.
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Affiliation(s)
- Ayumi Suzuki
- Department of Pediatric Dentistry, Asahi University School of Dentistry, 1851 Hozumi, Mizuho, Gifu 501-0296, Japan
| | - Mitsuo Iinuma
- Department of Pediatric Dentistry, Asahi University School of Dentistry, 1851 Hozumi, Mizuho, Gifu 501-0296, Japan
| | - Sakurako Hayashi
- Department of Pediatric Dentistry, Asahi University School of Dentistry, 1851 Hozumi, Mizuho, Gifu 501-0296, Japan
| | - Yuichi Sato
- Department of Molecular Diagnostics, Kitasato University School of Allied Health Science, Kitasato 1-15-1, Minamiku, Sagamihara, Kanagawa 252-0373, Japan
| | - Kagaku Azuma
- Department of Anatomy, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, Fukuoka 807-8555, Japan
| | - Kin-Ya Kubo
- Seijoh University Graduate School of Health Care Studies, 2-172, Fukinodai, Tokai, Aichi 476-8588, Japan.
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197
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Zaimi A, Duval T, Gasecka A, Côté D, Stikov N, Cohen-Adad J. AxonSeg: Open Source Software for Axon and Myelin Segmentation and Morphometric Analysis. Front Neuroinform 2016; 10:37. [PMID: 27594833 PMCID: PMC4990549 DOI: 10.3389/fninf.2016.00037] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 08/08/2016] [Indexed: 01/21/2023] Open
Abstract
Segmenting axon and myelin from microscopic images is relevant for studying the peripheral and central nervous system and for validating new MRI techniques that aim at quantifying tissue microstructure. While several software packages have been proposed, their interface is sometimes limited and/or they are designed to work with a specific modality (e.g., scanning electron microscopy (SEM) only). Here we introduce AxonSeg, which allows to perform automatic axon and myelin segmentation on histology images, and to extract relevant morphometric information, such as axon diameter distribution, axon density and the myelin g-ratio. AxonSeg includes a simple and intuitive MATLAB-based graphical user interface (GUI) and can easily be adapted to a variety of imaging modalities. The main steps of AxonSeg consist of: (i) image pre-processing; (ii) pre-segmentation of axons over a cropped image and discriminant analysis (DA) to select the best parameters based on axon shape and intensity information; (iii) automatic axon and myelin segmentation over the full image; and (iv) atlas-based statistics to extract morphometric information. Segmentation results from standard optical microscopy (OM), SEM and coherent anti-Stokes Raman scattering (CARS) microscopy are presented, along with validation against manual segmentations. Being fully-automatic after a quick manual intervention on a cropped image, we believe AxonSeg will be useful to researchers interested in large throughput histology. AxonSeg is open source and freely available at: https://github.com/neuropoly/axonseg.
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Affiliation(s)
- Aldo Zaimi
- Institute of Biomedical Engineering, Polytechnique Montreal Montreal, QC, Canada
| | - Tanguy Duval
- Institute of Biomedical Engineering, Polytechnique Montreal Montreal, QC, Canada
| | - Alicja Gasecka
- Institut Universitaire en Santé Mentale de QuébecQuebec, QC, Canada; Centre d'Optique, Photonique et Laser, Université LavalQuebec, QC, Canada
| | - Daniel Côté
- Institut Universitaire en Santé Mentale de QuébecQuebec, QC, Canada; Centre d'Optique, Photonique et Laser, Université LavalQuebec, QC, Canada
| | - Nikola Stikov
- Institute of Biomedical Engineering, Polytechnique MontrealMontreal, QC, Canada; Montreal Heart InstituteMontreal, QC, Canada
| | - Julien Cohen-Adad
- Institute of Biomedical Engineering, Polytechnique MontrealMontreal, QC, Canada; Functional Neuroimaging Unit, CRIUGM, Université de MontréalMontreal, QC, Canada
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198
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Szewczyk LM, Brozko N, Nagalski A, Röckle I, Werneburg S, Hildebrandt H, Wisniewska MB, Kuznicki J. ST8SIA2 promotes oligodendrocyte differentiation and the integrity of myelin and axons. Glia 2016; 65:34-49. [PMID: 27534376 PMCID: PMC5129544 DOI: 10.1002/glia.23048] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 07/18/2016] [Accepted: 08/01/2016] [Indexed: 12/19/2022]
Abstract
ST8SIA2 is a polysialyltransferase that attaches polysialic acid to the glycoproteins NCAM1 and CADM1. Polysialylation is involved in brain development and plasticity. ST8SIA2 is a schizophrenia candidate gene, and St8sia2−/− mice exhibit schizophrenia‐like behavior. We sought to identify new pathological consequences of ST8SIA2 deficiency. Our proteomic analysis suggested myelin impairment in St8sia2−/− mice. Histological and immune staining together with Western blot revealed that the onset of myelination was not delayed in St8sia2−/− mice, but the content of myelin was lower. Ultrastructure analysis of the corpus callosum showed thinner myelin sheaths, smaller and irregularly shaped axons, and white matter lesions in adult St8sia2−/− mice. Then we evaluated oligodendrocyte differentiation in vivo and in vitro. Fewer OLIG2+ cells in the cortex and corpus callosum, together with the higher percentage of undifferentiated oligodenroglia in St8sia2−/− mice suggested an impairment in oligodendrocyte generation. Experiment on primary cultures of oligodendrocyte precursor cells (OPCs) confirmed a cell‐autonomous effect of ST8SIA2 in oligodendroglia, and demonstrated that OPC to oligodendrocyte transition is inhibited in St8sia2−/− mice. Concluding, ST8SIA2‐mediated polysialylation influences on oligodendrocyte differentiation, and oligodendrocyte deficits in St8sia2 mice are a possible cause of the demyelination and degeneration of axons, resembling nerve fiber alterations in schizophrenia. GLIA 2016;65:34–49
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Affiliation(s)
- Lukasz Mateusz Szewczyk
- Laboratory of Neurodegeneration, International Institute of Molecular and Cell Biology, ul. Ks. Trojdena 4, Warszawa, 02-109, Poland.,Laboratory of Molecular Neurobiology, Centre of New Technologies, University of Warsaw, ul. Banacha 2C, Warszawa, 02-097, Poland.,Postgraduate School of Molecular Medicine, ul. Zwirki i Wigury 61, Warszawa, 02-091, Poland
| | - Nikola Brozko
- Laboratory of Molecular Neurobiology, Centre of New Technologies, University of Warsaw, ul. Banacha 2C, Warszawa, 02-097, Poland.,Postgraduate School of Molecular Medicine, ul. Zwirki i Wigury 61, Warszawa, 02-091, Poland
| | - Andrzej Nagalski
- Laboratory of Neurodegeneration, International Institute of Molecular and Cell Biology, ul. Ks. Trojdena 4, Warszawa, 02-109, Poland
| | - Iris Röckle
- Institute for Cellular Chemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, Hannover, 30625, Germany
| | - Sebastian Werneburg
- Institute for Cellular Chemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, Hannover, 30625, Germany
| | - Herbert Hildebrandt
- Institute for Cellular Chemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, Hannover, 30625, Germany
| | - Marta Barbara Wisniewska
- Laboratory of Neurodegeneration, International Institute of Molecular and Cell Biology, ul. Ks. Trojdena 4, Warszawa, 02-109, Poland.,Laboratory of Molecular Neurobiology, Centre of New Technologies, University of Warsaw, ul. Banacha 2C, Warszawa, 02-097, Poland
| | - Jacek Kuznicki
- Laboratory of Neurodegeneration, International Institute of Molecular and Cell Biology, ul. Ks. Trojdena 4, Warszawa, 02-109, Poland
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199
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Kurioka T, Lee MY, Heeringa AN, Beyer LA, Swiderski DL, Kanicki AC, Kabara LL, Dolan DF, Shore SE, Raphael Y. Selective hair cell ablation and noise exposure lead to different patterns of changes in the cochlea and the cochlear nucleus. Neuroscience 2016; 332:242-57. [PMID: 27403879 DOI: 10.1016/j.neuroscience.2016.07.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Revised: 06/14/2016] [Accepted: 07/01/2016] [Indexed: 01/21/2023]
Abstract
In experimental animal models of auditory hair cell (HC) loss, insults such as noise or ototoxic drugs often lead to secondary changes or degeneration in non-sensory cells and neural components, including reduced density of spiral ganglion neurons, demyelination of auditory nerve fibers and altered cell numbers and innervation patterns in the cochlear nucleus (CN). However, it is not clear whether loss of HCs alone leads to secondary degeneration in these neural components of the auditory pathway. To elucidate this issue, we investigated changes of central components after cochlear insults specific to HCs using diphtheria toxin receptor (DTR) mice expressing DTR only in HCs and exhibiting complete HC loss when injected with diphtheria toxin (DT). We showed that DT-induced HC ablation has no significant impacts on the survival of auditory neurons, central synaptic terminals, and myelin, despite complete HC loss and profound deafness. In contrast, noise exposure induced significant changes in synapses, myelin and CN organization even without loss of inner HCs. We observed a decrease of neuronal size in the auditory pathway, including peripheral axons, spiral ganglion neurons, and CN neurons, likely due to loss of input from the cochlea. Taken together, selective HC ablation and noise exposure showed different patterns of pathology in the auditory pathway and the presence of HCs is not essential for the maintenance of central synaptic connectivity and myelination.
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Affiliation(s)
- Takaomi Kurioka
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA; Department of Otorhinolaryngology-Head and Neck Surgery, National Defense Medical College, Tokorozawa, Saitama, Japan
| | - Min Young Lee
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Amarins N Heeringa
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Lisa A Beyer
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Donald L Swiderski
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Ariane C Kanicki
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Lisa L Kabara
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - David F Dolan
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Susan E Shore
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Yehoash Raphael
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA.
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200
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Chang KJ, Redmond SA, Chan JR. Remodeling myelination: implications for mechanisms of neural plasticity. Nat Neurosci 2016; 19:190-7. [PMID: 26814588 DOI: 10.1038/nn.4200] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2015] [Accepted: 10/12/2015] [Indexed: 02/08/2023]
Abstract
One of the most significant paradigm shifts in membrane remodeling is the emerging view that membrane transformation is not exclusively controlled by cytoskeletal rearrangement, but also by biophysical constraints, adhesive forces, membrane curvature and compaction. One of the most exquisite examples of membrane remodeling is myelination. The advent of myelin was instrumental in advancing the nervous system during vertebrate evolution. With more rapid and efficient communication between neurons, faster and more complex computations could be performed in a given time and space. Our knowledge of how myelin-forming oligodendrocytes select and wrap axons has been limited by insufficient spatial and temporal resolution. By virtue of recent technological advances, progress has clarified longstanding controversies in the field. Here we review insights into myelination, from target selection to axon wrapping and membrane compaction, and discuss how understanding these processes has unexpectedly opened new avenues of insight into myelination-centered mechanisms of neural plasticity.
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Affiliation(s)
- Kae-Jiun Chang
- Department of Neurology, University of California, San Francisco, California, USA
| | - Stephanie A Redmond
- Department of Neurology, University of California, San Francisco, California, USA.,Program in Neuroscience, University of California, San Francisco, California, USA
| | - Jonah R Chan
- Department of Neurology, University of California, San Francisco, California, USA.,Program in Neuroscience, University of California, San Francisco, California, USA
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