1
|
Bagheri H, Friedman H, Hadwen A, Jarweh C, Cooper E, Oprea L, Guerrier C, Khadra A, Collin A, Cohen-Adad J, Young A, Victoriano GM, Swire M, Jarjour A, Bechler ME, Pryce RS, Chaurand P, Cougnaud L, Vuckovic D, Wilion E, Greene O, Nishiyama A, Benmamar-Badel A, Owens T, Grouza V, Tuznik M, Liu H, Rudko DA, Zhang J, Siminovitch KA, Peterson AC. Myelin basic protein mRNA levels affect myelin sheath dimensions, architecture, plasticity, and density of resident glial cells. Glia 2024; 72:1893-1914. [PMID: 39023138 DOI: 10.1002/glia.24589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2024] [Revised: 05/29/2024] [Accepted: 06/23/2024] [Indexed: 07/20/2024]
Abstract
Myelin Basic Protein (MBP) is essential for both elaboration and maintenance of CNS myelin, and its reduced accumulation results in hypomyelination. How different Mbp mRNA levels affect myelin dimensions across the lifespan and how resident glial cells may respond to such changes are unknown. Here, to investigate these questions, we used enhancer-edited mouse lines that accumulate Mbp mRNA levels ranging from 8% to 160% of wild type. In young mice, reduced Mbp mRNA levels resulted in corresponding decreases in Mbp protein accumulation and myelin sheath thickness, confirming the previously demonstrated rate-limiting role of Mbp transcription in the control of initial myelin synthesis. However, despite maintaining lower line specific Mbp mRNA levels into old age, both MBP protein levels and myelin thickness improved or fully normalized at rates defined by the relative Mbp mRNA level. Sheath length, in contrast, was affected only when mRNA levels were very low, demonstrating that sheath thickness and length are not equally coupled to Mbp mRNA level. Striking abnormalities in sheath structure also emerged with reduced mRNA levels. Unexpectedly, an increase in the density of all glial cell types arose in response to reduced Mbp mRNA levels. This investigation extends understanding of the role MBP plays in myelin sheath elaboration, architecture, and plasticity across the mouse lifespan and illuminates a novel axis of glial cell crosstalk.
Collapse
Affiliation(s)
- Hooman Bagheri
- Department of Human Genetics, McGill University, Montreal, Quebec, Canada
| | - Hana Friedman
- Department of Human Genetics, McGill University, Montreal, Quebec, Canada
| | - Amanda Hadwen
- Department of Physiology, McGill University, Montreal, Quebec, Canada
| | - Celia Jarweh
- Department of Pharmacology & Therapeutics, McGill University, Montreal, Quebec, Canada
| | - Ellis Cooper
- Department of Physiology, McGill University, Montreal, Quebec, Canada
| | - Lawrence Oprea
- Integrated Program in Neuroscience, McGill University, Montréal, Quebec, Canada
| | | | - Anmar Khadra
- Integrated Program in Neuroscience, McGill University, Montréal, Quebec, Canada
| | - Armand Collin
- Institute of Biomedical Engineering, Ecole Polytechnique de Montreal, Montreal, Quebec, Canada
| | - Julien Cohen-Adad
- Institute of Biomedical Engineering, Ecole Polytechnique de Montreal, Montreal, Quebec, Canada
| | - Amanda Young
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
- Department of Neuroscience and Physiology, State University of New York Upstate Medical University, Syracuse, New York, USA
| | - Gerardo Mendez Victoriano
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
- Department of Neuroscience and Physiology, State University of New York Upstate Medical University, Syracuse, New York, USA
| | - Matthew Swire
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
- Department of Neuroscience and Physiology, State University of New York Upstate Medical University, Syracuse, New York, USA
| | - Andrew Jarjour
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
- Department of Neuroscience and Physiology, State University of New York Upstate Medical University, Syracuse, New York, USA
| | - Marie E Bechler
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
- Department of Neuroscience and Physiology, State University of New York Upstate Medical University, Syracuse, New York, USA
| | - Rachel S Pryce
- Department of Chemistry, Université de Montréal, Montreal, Quebec, Canada
| | - Pierre Chaurand
- Department of Chemistry, Université de Montréal, Montreal, Quebec, Canada
| | - Lise Cougnaud
- Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec, Canada
| | - Dajana Vuckovic
- Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec, Canada
| | - Elliott Wilion
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut, USA
| | - Owen Greene
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut, USA
| | - Akiko Nishiyama
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut, USA
- Institute for Systems Genomics, University of Connecticut, Storrs, Connecticut, USA
- The Connecticut Institute for Brain and Cognitive Sciences, University of Connecticut, Storrs, Connecticut, USA
| | - Anouk Benmamar-Badel
- Department of Neurobiology Research, Institute for Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Trevor Owens
- Department of Neurobiology Research, Institute for Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Vladimir Grouza
- McConnell Brain Imaging Centre, Montreal Neurological Institute and Hospital, Montreal, Quebec, Canada
- Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada
| | - Marius Tuznik
- McConnell Brain Imaging Centre, Montreal Neurological Institute and Hospital, Montreal, Quebec, Canada
- Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada
| | - Hanwen Liu
- McConnell Brain Imaging Centre, Montreal Neurological Institute and Hospital, Montreal, Quebec, Canada
- Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada
| | - David A Rudko
- McConnell Brain Imaging Centre, Montreal Neurological Institute and Hospital, Montreal, Quebec, Canada
- Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada
- Department of Biomedical Engineering, McGill University, Montreal, Quebec, Canada
| | - Jinyi Zhang
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
- Mount Sinai Hospital, Lunenfeld-Tanenbaum and Toronto General Hospital Research Institutes, Toronto, Ontario, Canada
| | - Katherine A Siminovitch
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
- Mount Sinai Hospital, Lunenfeld-Tanenbaum and Toronto General Hospital Research Institutes, Toronto, Ontario, Canada
| | - Alan C Peterson
- Department of Human Genetics, McGill University, Montreal, Quebec, Canada
- Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada
- Gerald Bronfman Department of Oncology, McGill University, Quebec, Canada
| |
Collapse
|
2
|
Richardson B, Goedert T, Quraishe S, Deinhardt K, Mudher A. How do neurons age? A focused review on the aging of the microtubular cytoskeleton. Neural Regen Res 2024; 19:1899-1907. [PMID: 38227514 DOI: 10.4103/1673-5374.390974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Accepted: 11/01/2023] [Indexed: 01/17/2024] Open
Abstract
Aging is the leading risk factor for Alzheimer's disease and other neurodegenerative diseases. We now understand that a breakdown in the neuronal cytoskeleton, mainly underpinned by protein modifications leading to the destabilization of microtubules, is central to the pathogenesis of Alzheimer's disease. This is accompanied by morphological defects across the somatodendritic compartment, axon, and synapse. However, knowledge of what occurs to the microtubule cytoskeleton and morphology of the neuron during physiological aging is comparatively poor. Several recent studies have suggested that there is an age-related increase in the phosphorylation of the key microtubule stabilizing protein tau, a modification, which is known to destabilize the cytoskeleton in Alzheimer's disease. This indicates that the cytoskeleton and potentially other neuronal structures reliant on the cytoskeleton become functionally compromised during normal physiological aging. The current literature shows age-related reductions in synaptic spine density and shifts in synaptic spine conformation which might explain age-related synaptic functional deficits. However, knowledge of what occurs to the microtubular and actin cytoskeleton, with increasing age is extremely limited. When considering the somatodendritic compartment, a regression in dendrites and loss of dendritic length and volume is reported whilst a reduction in soma volume/size is often seen. However, research into cytoskeletal change is limited to a handful of studies demonstrating reductions in and mislocalizations of microtubule-associated proteins with just one study directly exploring the integrity of the microtubules. In the axon, an increase in axonal diameter and age-related appearance of swellings is reported but like the dendrites, just one study investigates the microtubules directly with others reporting loss or mislocalization of microtubule-associated proteins. Though these are the general trends reported, there are clear disparities between model organisms and brain regions that are worthy of further investigation. Additionally, longitudinal studies of neuronal/cytoskeletal aging should also investigate whether these age-related changes contribute not just to vulnerability to disease but also to the decline in nervous system function and behavioral output that all organisms experience. This will highlight the utility, if any, of cytoskeletal fortification for the promotion of healthy neuronal aging and potential protection against age-related neurodegenerative disease. This review seeks to summarize what is currently known about the physiological aging of the neuron and microtubular cytoskeleton in the hope of uncovering mechanisms underpinning age-related risk to disease.
Collapse
Affiliation(s)
- Brad Richardson
- School of Biological Sciences, University of Southampton, Southampton, UK
| | - Thomas Goedert
- Institute of Developmental and Regenerative Medicine, University of Oxford, Oxford, UK
| | - Shmma Quraishe
- School of Biological Sciences, University of Southampton, Southampton, UK
| | - Katrin Deinhardt
- School of Biological Sciences, University of Southampton, Southampton, UK
| | - Amritpal Mudher
- School of Biological Sciences, University of Southampton, Southampton, UK
| |
Collapse
|
3
|
Osso LA, Hughes EG. Dynamics of mature myelin. Nat Neurosci 2024; 27:1449-1461. [PMID: 38773349 DOI: 10.1038/s41593-024-01642-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Accepted: 04/05/2024] [Indexed: 05/23/2024]
Abstract
Myelin, which is produced by oligodendrocytes, insulates axons to facilitate rapid and efficient action potential propagation in the central nervous system. Traditionally viewed as a stable structure, myelin is now known to undergo dynamic modulation throughout life. This Review examines these dynamics, focusing on two key aspects: (1) the turnover of myelin, involving not only the renewal of constituents but the continuous wholesale replacement of myelin membranes; and (2) the structural remodeling of pre-existing, mature myelin, a newly discovered form of neural plasticity that can be stimulated by external factors, including neuronal activity, behavioral experience and injury. We explore the mechanisms regulating these dynamics and speculate that myelin remodeling could be driven by an asymmetry in myelin turnover or reactivation of pathways involved in myelin formation. Finally, we outline how myelin remodeling could have profound impacts on neural function, serving as an integral component of behavioral adaptation.
Collapse
Affiliation(s)
- Lindsay A Osso
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Ethan G Hughes
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA.
| |
Collapse
|
4
|
Ibañez S, Sengupta N, Luebke JI, Wimmer K, Weaver CM. Myelin dystrophy impairs signal transmission and working memory in a multiscale model of the aging prefrontal cortex. eLife 2024; 12:RP90964. [PMID: 39028036 PMCID: PMC11259433 DOI: 10.7554/elife.90964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2024] Open
Abstract
Normal aging leads to myelin alterations in the rhesus monkey dorsolateral prefrontal cortex (dlPFC), which are positively correlated with degree of cognitive impairment. It is hypothesized that remyelination with shorter and thinner myelin sheaths partially compensates for myelin degradation, but computational modeling has not yet explored these two phenomena together systematically. Here, we used a two-pronged modeling approach to determine how age-related myelin changes affect a core cognitive function: spatial working memory. First, we built a multicompartment pyramidal neuron model fit to monkey dlPFC empirical data, with an axon including myelinated segments having paranodes, juxtaparanodes, internodes, and tight junctions. This model was used to quantify conduction velocity (CV) changes and action potential (AP) failures after demyelination and subsequent remyelination. Next, we incorporated the single neuron results into a spiking neural network model of working memory. While complete remyelination nearly recovered axonal transmission and network function to unperturbed levels, our models predict that biologically plausible levels of myelin dystrophy, if uncompensated by other factors, can account for substantial working memory impairment with aging. The present computational study unites empirical data from ultrastructure up to behavior during normal aging, and has broader implications for many demyelinating conditions, such as multiple sclerosis or schizophrenia.
Collapse
Affiliation(s)
- Sara Ibañez
- Department of Anatomy & Neurobiology, Boston University Chobanian & Avedisian School of MedicineBostonUnited States
- Centre de Recerca Matemàtica, Edifici C, Campus BellaterraBellaterraSpain
- Departament de Matemàtiques, Universitat Autònoma de Barcelona, Edifici CBellaterraSpain
| | - Nilapratim Sengupta
- Department of Anatomy & Neurobiology, Boston University Chobanian & Avedisian School of MedicineBostonUnited States
- Department of Mathematics, Franklin and Marshall CollegeLancasterUnited States
| | - Jennifer I Luebke
- Department of Anatomy & Neurobiology, Boston University Chobanian & Avedisian School of MedicineBostonUnited States
| | - Klaus Wimmer
- Centre de Recerca Matemàtica, Edifici C, Campus BellaterraBellaterraSpain
- Departament de Matemàtiques, Universitat Autònoma de Barcelona, Edifici CBellaterraSpain
| | - Christina M Weaver
- Department of Mathematics, Franklin and Marshall CollegeLancasterUnited States
| |
Collapse
|
5
|
Huang WQ, Sheng H, Wang H, Qi Y, Wang F, Hua Y. Volume electron microscopy reveals age-related ultrastructural differences of globular bush cell axons in mouse central auditory system. Neurobiol Aging 2024; 136:111-124. [PMID: 38342072 DOI: 10.1016/j.neurobiolaging.2024.01.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 01/30/2024] [Accepted: 01/31/2024] [Indexed: 02/13/2024]
Abstract
In mammals, thick axonal calibers wrapped with heavy myelin sheaths are prevalent in the auditory nervous system. These features are crucial for fast traveling of nerve impulses with minimal attenuation required for sound signal transmission. In particular, the long-range projections from the cochlear nucleus - the axons of globular bush cells (GBCs) - to the medial nucleus of the trapezoid body (MNTB) are tonotopically organized. However, it remains controversial in gerbils and mice whether structural and functional adaptations are present among the GBC axons targeting different MNTB frequency regions. By means of high-throughput volume electron microscopy, we compared the GBC axons in full-tonotopy-ranged MNTB slices from the C57BL/6 mice at different ages. Our quantification reveals distinct caliber diameter and myelin profile of the GBC axons with endings at lateral and medial MNTB, arguing for modulation of functionally heterogeneous axon subgroups. In addition, we reported axon-specific differences in axon caliber, node of Ranvier, and myelin sheath among juvenile, adult, and old mice, indicating the age-related changes of GBC axon morphology over time. These findings provide structural insight into the maturation and degeneration of GBC axons with frequency tuning across the lifespan of mice.
Collapse
Affiliation(s)
- Wen-Qing Huang
- Department of Otolaryngology-Head and Neck Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China; Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Department of Central Laboratory, Shanghai Children's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
| | - Haibin Sheng
- Department of Otolaryngology-Head and Neck Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Haoyu Wang
- Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yumeng Qi
- Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Fangfang Wang
- Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
| | - Yunfeng Hua
- Department of Otolaryngology-Head and Neck Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China; Shanghai Institute of Precision Medicine, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| |
Collapse
|
6
|
Kent SA, Miron VE. Microglia regulation of central nervous system myelin health and regeneration. Nat Rev Immunol 2024; 24:49-63. [PMID: 37452201 DOI: 10.1038/s41577-023-00907-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2023] [Indexed: 07/18/2023]
Abstract
Microglia are resident macrophages of the central nervous system that have key functions in its development, homeostasis and response to damage and infection. Although microglia have been increasingly implicated in contributing to the pathology that underpins neurological dysfunction and disease, they also have crucial roles in neurological homeostasis and regeneration. This includes regulation of the maintenance and regeneration of myelin, the membrane that surrounds neuronal axons, which is required for axonal health and function. Myelin is damaged with normal ageing and in several neurodegenerative diseases, such as multiple sclerosis and Alzheimer disease. Given the lack of approved therapies targeting myelin maintenance or regeneration, it is imperative to understand the mechanisms by which microglia support and restore myelin health to identify potential therapeutic approaches. However, the mechanisms by which microglia regulate myelin loss or integrity are still being uncovered. In this Review, we discuss recent work that reveals the changes in white matter with ageing and neurodegenerative disease, how this relates to microglia dynamics during myelin damage and regeneration, and factors that influence the regenerative functions of microglia.
Collapse
Affiliation(s)
- Sarah A Kent
- UK Dementia Research Institute at The University of Edinburgh, Edinburgh, UK
- Centre for Discovery Brain Sciences, Chancellor's Building, The University of Edinburgh, Edinburgh, UK
| | - Veronique E Miron
- UK Dementia Research Institute at The University of Edinburgh, Edinburgh, UK.
- Centre for Discovery Brain Sciences, Chancellor's Building, The University of Edinburgh, Edinburgh, UK.
- Barlo Multiple Sclerosis Centre, St Michael's Hospital, Toronto, Ontario, Canada.
- Keenan Research Centre for Biomedical Science, St Michael's Hospital, Toronto, Ontario, Canada.
- Department of Immunology, The University of Toronto, Toronto, Ontario, Canada.
| |
Collapse
|
7
|
Ibañez S, Sengupta N, Luebke JI, Wimmer K, Weaver CM. Myelin dystrophy in the aging prefrontal cortex leads to impaired signal transmission and working memory decline: a multiscale computational study. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.30.555476. [PMID: 37693412 PMCID: PMC10491254 DOI: 10.1101/2023.08.30.555476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Normal aging leads to myelin alternations in the rhesus monkey dorsolateral prefrontal cortex (dlPFC), which are often correlated with cognitive impairment. It is hypothesized that remyelination with shorter and thinner myelin sheaths partially compensates for myelin degradation, but computational modeling has not yet explored these two phenomena together systematically. Here, we used a two-pronged modeling approach to determine how age-related myelin changes affect a core cognitive function: spatial working memory. First we built a multicompartment pyramidal neuron model fit to monkey dlPFC data, with axon including myelinated segments having paranodes, juxtaparanodes, internodes, and tight junctions, to quantify conduction velocity (CV) changes and action potential (AP) failures after demyelination and subsequent remyelination in a population of neurons. Lasso regression identified distinctive parameter sets likely to modulate an axon's susceptibility to CV changes following demyelination versus remyelination. Next we incorporated the single neuron results into a spiking neural network model of working memory. While complete remyelination nearly recovered axonal transmission and network function to unperturbed levels, our models predict that biologically plausible levels of myelin dystrophy, if uncompensated by other factors, can account for substantial working memory impairment with aging. The present computational study unites empirical data from electron microscopy up to behavior on aging, and has broader implications for many demyelinating conditions, such as multiple sclerosis or schizophrenia.
Collapse
Affiliation(s)
- Sara Ibañez
- Department of Anatomy & Neurobiology, Boston University Chobanian & Avedisian School of Medicine, Boston, MA USA 02118
- Centre de Recerca Matemàtica, Edifici C, Campus Bellaterra, 08193 Bellaterra, Spain
| | - Nilapratim Sengupta
- Department of Anatomy & Neurobiology, Boston University Chobanian & Avedisian School of Medicine, Boston, MA USA 02118
- Department of Mathematics, Franklin and Marshall College, Lancaster, PA, USA 17604
| | - Jennifer I Luebke
- Department of Anatomy & Neurobiology, Boston University Chobanian & Avedisian School of Medicine, Boston, MA USA 02118
| | - Klaus Wimmer
- Centre de Recerca Matemàtica, Edifici C, Campus Bellaterra, 08193 Bellaterra, Spain
| | - Christina M Weaver
- Department of Mathematics, Franklin and Marshall College, Lancaster, PA, USA 17604
| |
Collapse
|
8
|
Molina-Gonzalez I, Miron VE, Antel JP. Chronic oligodendrocyte injury in central nervous system pathologies. Commun Biol 2022; 5:1274. [PMID: 36402839 PMCID: PMC9675815 DOI: 10.1038/s42003-022-04248-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 11/10/2022] [Indexed: 11/21/2022] Open
Abstract
Myelin, the membrane surrounding neuronal axons, is critical for central nervous system (CNS) function. Injury to myelin-forming oligodendrocytes (OL) in chronic neurological diseases (e.g. multiple sclerosis) ranges from sublethal to lethal, leading to OL dysfunction and myelin pathology, and consequent deleterious impacts on axonal health that drive clinical impairments. This is regulated by intrinsic factors such as heterogeneity and age, and extrinsic cellular and molecular interactions. Here, we discuss the responses of OLs to injury, and perspectives for therapeutic targeting. We put forward that targeting mature OL health in neurological disease is a promising therapeutic strategy to support CNS function.
Collapse
Affiliation(s)
- Irene Molina-Gonzalez
- grid.4305.20000 0004 1936 7988United Kingdom Dementia Research Institute at The University of Edinburgh, Edinburgh, Scotland UK ,grid.4305.20000 0004 1936 7988Centre for Discovery Brain Sciences, Chancellor’s Building, The University of Edinburgh, Edinburgh, Scotland UK ,grid.4305.20000 0004 1936 7988Medical Research Council Centre for Reproductive Health, The Queen’s Medical Research Institute, The University of Edinburgh, Edinburgh, Scotland UK
| | - Veronique E. Miron
- grid.4305.20000 0004 1936 7988United Kingdom Dementia Research Institute at The University of Edinburgh, Edinburgh, Scotland UK ,grid.4305.20000 0004 1936 7988Centre for Discovery Brain Sciences, Chancellor’s Building, The University of Edinburgh, Edinburgh, Scotland UK ,grid.4305.20000 0004 1936 7988Medical Research Council Centre for Reproductive Health, The Queen’s Medical Research Institute, The University of Edinburgh, Edinburgh, Scotland UK ,grid.415502.7Barlo Multiple Sclerosis Centre and Keenan Research Centre for Biomedical Science, Toronto, Canada ,grid.17063.330000 0001 2157 2938Department of Immunology, University of Toronto, Toronto, Canada
| | - Jack P. Antel
- grid.14709.3b0000 0004 1936 8649Neuroimmunology Unit, Montreal Neurological Institute, McGill University, Montreal, QC Canada
| |
Collapse
|
9
|
Moore S, Meschkat M, Ruhwedel T, Trevisiol A, Tzvetanova ID, Battefeld A, Kusch K, Kole MHP, Strenzke N, Möbius W, de Hoz L, Nave KA. A role of oligodendrocytes in information processing. Nat Commun 2020; 11:5497. [PMID: 33127910 PMCID: PMC7599337 DOI: 10.1038/s41467-020-19152-7] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 09/30/2020] [Indexed: 12/12/2022] Open
Abstract
Myelinating oligodendrocytes enable fast propagation of action potentials along the ensheathed axons. In addition, oligodendrocytes play diverse non-canonical roles including axonal metabolic support and activity-dependent myelination. An open question remains whether myelination also contributes to information processing in addition to speeding up conduction velocity. Here, we analyze the role of myelin in auditory information processing using paradigms that are also good predictors of speech understanding in humans. We compare mice with different degrees of dysmyelination using acute multiunit recordings in the auditory cortex, in combination with behavioral readouts. We find complex alterations of neuronal responses that reflect fatigue and temporal acuity deficits. We observe partially discriminable but similar deficits in well myelinated mice in which glial cells cannot fully support axons metabolically. We suggest a model in which myelination contributes to sustained stimulus perception in temporally complex paradigms, with a role of metabolically active oligodendrocytes in cortical information processing.
Collapse
Affiliation(s)
- Sharlen Moore
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
- International Max Planck Research School for Neurosciences, Göttingen, Germany
- Göttingen Graduate Center for Neurosciences, Biophysics and Molecular Biosciences, Georg-August-Universität Göttingen, Göttingen, Germany
- Department of Psychological and Brain Sciences, Krieger School of Arts and Sciences, Johns Hopkins University, Baltimore, USA
| | - Martin Meschkat
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
- Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany
| | - Torben Ruhwedel
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Andrea Trevisiol
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
- Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Canada
| | - Iva D Tzvetanova
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
- Section of Pharmacology, School of Medicine, European University Cyprus, Nicosia, Cyprus
| | - Arne Battefeld
- Department of Axonal Signaling, Netherlands Institute for Neurosciences, Royal Netherlands Academy of Arts and Science, Amsterdam, The Netherlands
- Institut des Maladies Neurodégénératives, Université de Bordeaux, Bordeaux, France
| | - Kathrin Kusch
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Maarten H P Kole
- Department of Axonal Signaling, Netherlands Institute for Neurosciences, Royal Netherlands Academy of Arts and Science, Amsterdam, The Netherlands
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, University of Utrecht, Utrecht, The Netherlands
| | - Nicola Strenzke
- Institute for Auditory Neuroscience, University Medical Center, Göttingen, Germany
| | - Wiebke Möbius
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
- Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany
| | - Livia de Hoz
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.
- Charité Medical University, Neuroscience Research Center, Berlin, Germany.
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
- Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany
| |
Collapse
|
10
|
Wolfe T, Hoffman K, Hogan MK, Salazar B, Tang X, Chaboub L, Quini CC, Lu ZL, Horner PJ. Quantification of Myelinated Nerve Fraction and Degeneration in Spinal Cord Neuropil by SHIFT MRI. J Magn Reson Imaging 2020; 53:1162-1174. [PMID: 33098256 DOI: 10.1002/jmri.27397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 09/29/2020] [Accepted: 09/30/2020] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND Neurodegeneration is a complex cellular process linked to prompt changes in myelin integrity and gradual neuron loss. Current imaging techniques offer estimations of myelin volumes in lesions/remyelinated areas but are limited to detect subtle injury. PURPOSE To investigate whether measurements detected by a signal hierarchically isolated as a function of time-to-echo (SHIFT) MRI technique can determine changes in myelin integrity and fiber axolemma. STUDY TYPE Prospective animal model. ANIMAL MODEL Surgically demyelinated spinal cord (SC) injury model in rodents (n = 6). FIELD STRENGTH/SEQUENCE Gradient-echo spin-echo at 3T. ASSESSMENT Multicompartment T2 relaxations were computed by SHIFT MRI in 75-microns-resolution images of the SC injury penumbra region 2 weeks post-trauma. G-ratio and axolemma delamination were assessed by transmission electron microscopy (TEM) in intact and injured samples. SC myelinated nerve fraction was computed by SHIFT MRI prospectively and assessed histologically. STATISTICAL TESTS Relations between SHIFT-isolated T2 -components and TEM measurements were studied using linear regression and t-tests. Pearson's correlation and significance were computed to determine the SHIFT's sensitivity to detect myelinated fibers ratio in gray matter. Regularized least-squares-based ranking analysis was employed to determine SHIFT MRI's ability to discern intact and injured myelinated nerves. RESULTS Biexponential signals isolated by SHIFT MRI for intact vs. lesion penumbra exhibited changes in T2 , shifting from intermediate components (25 ± 2 msec) to long (43 ± 11 msec) in white matter, and similarly in gray matter regions-of-interest (31 ± 2 to 46 ± 16 msec). These changes correlated highly with TEM g-ratio and axon delamination measurements (P < 0.05). Changes in short T2 components were observed but not statistically significant (8.5 ± 0.5 to 7 ± 3 msec, P = 0.445, and 4.0 ± 0.9 to 7 ± 3 msec, P = 0.075, respectively). SHIFT MRI's ability to detect myelinated fibers within gray matter was confirmed (P < 0.001). DATA CONCLUSION Changes detected by SHIFT MRI are associated with abnormal intermembrane spaces formed upon mild injury, directly correlated with early neuro integrity loss. Level of Evidence 1 Technical Efficacy Stage 2.
Collapse
Affiliation(s)
- Tatiana Wolfe
- Center for Neuroregneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston Methodist Hospital, Houston, Texas, USA
| | - Kristopher Hoffman
- Center for Neuroregneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston Methodist Hospital, Houston, Texas, USA
| | - Matthew K Hogan
- Center for Neuroregneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston Methodist Hospital, Houston, Texas, USA
| | - Betsy Salazar
- Center for Neuroregneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston Methodist Hospital, Houston, Texas, USA
| | - Xiufeng Tang
- Center for Neuroregneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston Methodist Hospital, Houston, Texas, USA
| | - Lesley Chaboub
- Center for Neuroregneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston Methodist Hospital, Houston, Texas, USA
| | - Caio C Quini
- Department of Biological Physics, Universidade Estadual Paulista UNESP, Botucatu, Sao Paulo, Brazil
| | - Zhong-Lin Lu
- Division of Arts and Sciences, NYU Shanghai, Shanghai, China, NYU-ECNU Institute of Cognitive Neuroscience at NYU Shanghai, Shanghai, China, Center for Neural Science and Department of Psychology, New York University, New York, USA
| | - Philip J Horner
- Center for Neuroregneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston Methodist Hospital, Houston, Texas, USA
| |
Collapse
|
11
|
Braham Chaouche A, Silvestre D, Trognon A, Arleo A, Allard R. Age-related decline in motion contrast sensitivity due to lower absorption rate of cones and calculation efficiency. Sci Rep 2020; 10:16521. [PMID: 33020552 PMCID: PMC7536415 DOI: 10.1038/s41598-020-73322-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 09/14/2020] [Indexed: 11/09/2022] Open
Abstract
Motion perception is affected by healthy aging, which impairs the ability of older adults to perform some daily activities such as driving. The current study investigated the underlying causes of age-related motion contrast sensitivity losses by using an equivalent noise paradigm to decompose motion contrast sensitivity into calculation efficiency, the temporal modulation transfer function (i.e., temporal blur) and 3 sources of internal noise: stochastic absorption of photons by photoreceptors (i.e., photon noise), neural noise occurring at the retinal level (i.e., early noise) and at the cortical level (i.e., late noise). These sources of internal noise can be disentangled because there impacts on motion contrast sensitivity vary differently as a function of luminance intensity. The impact of healthy aging on these factors was evaluated by measuring motion contrast sensitivity of young and older healthy adults at different luminance intensities, temporal frequencies and with/without external noise. The older adults were found to have higher photon noise, which suggests a lower photon absorption rate of cones. When roughly equating the amount of photons being absorbed by the photoreceptors, older adults had lower calculation efficiencies, but no significant aging effect was found on temporal modulation transfer function, early noise and late noise.
Collapse
Affiliation(s)
- Asma Braham Chaouche
- INSERM, CNRS, Insititut de la Vision, Sorbonne Université, 17 Rue Moreau, 75012, Paris, France
| | - Daphné Silvestre
- INSERM, CNRS, Insititut de la Vision, Sorbonne Université, 17 Rue Moreau, 75012, Paris, France
| | - Arthur Trognon
- INSERM, CNRS, Insititut de la Vision, Sorbonne Université, 17 Rue Moreau, 75012, Paris, France
| | - Angelo Arleo
- INSERM, CNRS, Insititut de la Vision, Sorbonne Université, 17 Rue Moreau, 75012, Paris, France
| | - Rémy Allard
- INSERM, CNRS, Insititut de la Vision, Sorbonne Université, 17 Rue Moreau, 75012, Paris, France. .,Laboratoire Psychophysique de la Vision, École d'optométrie, Université de Montréal, Montréal, QC, Canada.
| |
Collapse
|
12
|
Pu R, Wu Z, Yu W, He H, Zhou Z, Wang Z, Zhong J. The association of myelination in the internal capsule with iron deposition in the basal ganglia in macaques: a magnetic resonance imaging study. Quant Imaging Med Surg 2020; 10:1526-1539. [PMID: 32676370 DOI: 10.21037/qims-19-1014] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Background Iron plays a vital role in myelin synthesis and maintenance. A tight association between iron concentration and myelin content has been demonstrated in local brain regions; however, whether such a relationship exists between distant brain regions that are anatomically connected is largely unknown. Methods We conducted an in vivo measurement of iron and myelin content in the brains of 8 young (mean age: 7.7 years) and 8 old (mean age: 24.7 years) macaques by integrating two MRI-based techniques: quantitative susceptibility mapping (QSM) and myelin water fraction (MWF) imaging. We examined the relationship between iron deposition in components of the basal ganglia (BG), and the myelin content of the BG-connecting fiber tract internal capsule (IC) and four more white matter (WM) structures, including the optic tract, and the genu, body, and splenium of the corpus callosum, which are anatomically separate from the BG. Results Spearman's correlation analysis revealed a moderate to high (r=0.528-0.808, P<0.05) positive correlation between the magnetic susceptibility of the BG and the MWF of anatomically connected IC structures during myelin production and maintenance, but little significant correlation was found between the susceptibility of the BG and the MWF of WM structures not anatomically connected to the BG. Conclusions These results advance the understanding of the relationship between iron and myelin, and suggest that future studies should consider the impact that iron concentration in the BG has on the myelination of WM structures that are anatomically connected to the BG.
Collapse
Affiliation(s)
- Run Pu
- 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, China
| | - Zhe Wu
- 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, China.,Techna Institute, University Health Network, Toronto, ON, Canada
| | - Wenwen Yu
- Institute of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, State Key Laboratory of Neuroscience, CAS Key Laboratory of Primate Neurobiology, Chinese Academy of Sciences, Shanghai, China.,Shanghai Center for Brain Science and Brain-inspired Intelligence Technology, Shanghai, 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, China
| | - Zuofu Zhou
- Department of Radiology, Fujian Provincial Maternity and Children's Hospital of Fujian Medical University, Fuzhou, China
| | - Zheng Wang
- Institute of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, State Key Laboratory of Neuroscience, CAS Key Laboratory of Primate Neurobiology, Chinese Academy of Sciences, Shanghai, China.,Shanghai Center for Brain Science and Brain-inspired Intelligence Technology, Shanghai, China.,University of Chinese Academy of Sciences, 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, China.,Department of Imaging Sciences, University of Rochester, NY, USA
| |
Collapse
|
13
|
Linking the impact of aging on visual short-term memory capacity with changes in the structural connectivity of posterior thalamus to occipital cortices. Neuroimage 2019; 208:116440. [PMID: 31841682 DOI: 10.1016/j.neuroimage.2019.116440] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Revised: 11/25/2019] [Accepted: 12/03/2019] [Indexed: 12/31/2022] Open
Abstract
Aging impacts both visual short-term memory (vSTM) capacity and thalamo-cortical connectivity. According to the Neural Theory of Visual Attention, vSTM depends on the structural connectivity between posterior thalamus and visual occipital cortices (PT-OC). We tested whether aging modifies the association between vSTM capacity and PT-OC structural connectivity. To do so, 66 individuals aged 20-77 years were assessed by diffusion-weighted imaging used for probabilistic tractography and performed a psychophysical whole-report task of briefly presented letter arrays, from which vSTM capacity estimates were derived. We found reduced vSTM capacity, and aberrant PT-OC connection probability in aging. Critically, age modified the relationship between vSTM capacity and PT-OC connection probability: in younger adults, vSTM capacity was negatively correlated with PT-OC connection probability while in older adults, this association was positive. Furthermore, age modified the microstructure of PT-OC tracts suggesting that the inversion of the association between PT-OC connection probability and vSTM capacity with aging might reflect age-related changes in white-matter properties. Accordingly, our results demonstrate that age-related differences in vSTM capacity links with the microstructure and connectivity of PT-OC tracts.
Collapse
|
14
|
Abdelkarim D, Zhao Y, Turner MP, Sivakolundu DK, Lu H, Rypma B. A neural-vascular complex of age-related changes in the human brain: Anatomy, physiology, and implications for neurocognitive aging. Neurosci Biobehav Rev 2019; 107:927-944. [DOI: 10.1016/j.neubiorev.2019.09.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 08/02/2019] [Accepted: 09/02/2019] [Indexed: 01/09/2023]
|
15
|
Chapman TW, Hill RA. Myelin plasticity in adulthood and aging. Neurosci Lett 2019; 715:134645. [PMID: 31765728 DOI: 10.1016/j.neulet.2019.134645] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 11/06/2019] [Accepted: 11/21/2019] [Indexed: 12/31/2022]
Abstract
The central nervous system maintains the potential for molecular and cellular plasticity throughout life. This flexibility underlies fundamental features of neural circuitry including the brain's ability to sense, store, and properly adapt to everchanging external stimuli on time scales from seconds to years. Evidence for most forms of plasticity are centered around changes in neuronal structure and synaptic strength, however recent data suggests that myelinating oligodendrocytes exhibit certain forms of plasticity in the adult. This plasticity ranges from the generation of entirely new myelinating cells to more subtle changes in myelin sheath length, thickness, and distribution along axons. The extent to which these changes dynamically modify axonal function and neural circuitry and whether they are directly related to mechanisms of learning and memory remains an open question. Here we describe different forms of myelin plasticity, highlight some recent evidence for changes in myelination throughout life, and discuss how defects in these forms of plasticity could be associated with cognitive decline in aging.
Collapse
Affiliation(s)
- Timothy W Chapman
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
| | - Robert A Hill
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA.
| |
Collapse
|
16
|
McKavanagh R, Torso M, Jenkinson M, Kolasinski J, Stagg CJ, Esiri MM, McNab JA, Johansen‐Berg H, Miller KL, Chance SA. Relating diffusion tensor imaging measurements to microstructural quantities in the cerebral cortex in multiple sclerosis. Hum Brain Mapp 2019; 40:4417-4431. [PMID: 31355989 PMCID: PMC6772025 DOI: 10.1002/hbm.24711] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 05/20/2019] [Accepted: 05/31/2019] [Indexed: 12/13/2022] Open
Abstract
To investigate whether the observed anisotropic diffusion in cerebral cortex may reflect its columnar cytoarchitecture and myeloarchitecture, as a potential biomarker for disease-related changes, we compared postmortem diffusion magnetic resonance imaging scans of nine multiple sclerosis brains with histology measures from the same regions. Histology measurements assessed the cortical minicolumnar structure based on cell bodies and associated axon bundles in dorsolateral prefrontal cortex (Area 9), Heschl's gyrus (Area 41), and primary visual cortex (V1). Diffusivity measures included mean diffusivity, fractional anisotropy of the cortex, and three specific measures that may relate to the radial minicolumn structure: the angle of the principal diffusion direction in the cortex, the component that was perpendicular to the radial direction, and the component that was parallel to the radial direction. The cellular minicolumn microcircuit features were correlated with diffusion angle in Areas 9 and 41, and the axon bundle features were correlated with angle in Area 9 and to the parallel component in V1 cortex. This may reflect the effect of minicolumn microcircuit organisation on diffusion in the cortex, due to the number of coherently arranged membranes and myelinated structures. Several of the cortical diffusion measures showed group differences between MS brains and control brains. Differences between brain regions were also found in histology and diffusivity measurements consistent with established regional variation in cytoarchitecture and myeloarchitecture. Therefore, these novel measures may provide a surrogate of cortical organisation as a potential biomarker, which is particularly relevant for detecting regional changes in neurological disorders.
Collapse
Affiliation(s)
- Rebecca McKavanagh
- Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
| | - Mario Torso
- Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
| | - Mark Jenkinson
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
| | - James Kolasinski
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
| | - Charlotte J. Stagg
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
| | - Margaret M. Esiri
- Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
| | - Jennifer A. McNab
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
| | - Heidi Johansen‐Berg
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
| | - Karla L. Miller
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
| | - Steven A. Chance
- Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUnited Kingdom
| |
Collapse
|
17
|
Karolis VR, Callaghan MF, Tseng CEJ, Hope T, Weiskopf N, Rees G, Cappelletti M. Spatial gradients of healthy aging: a study of myelin-sensitive maps. Neurobiol Aging 2019; 79:83-92. [PMID: 31029019 DOI: 10.1016/j.neurobiolaging.2019.03.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 02/06/2019] [Accepted: 03/05/2019] [Indexed: 10/27/2022]
Abstract
Protracted development of a brain network may entail greater susceptibility to aging decline, supported by evidence of an earlier onset of age-related changes in late-maturing anterior areas, that is, an anterior-to-posterior gradient of brain aging. Here we analyzed the spatiotemporal features of age-related differences in myelin content across the human brain indexed by magnetization transfer (MT) concentration in a cross-sectional cohort of healthy adults. We described age-related spatial gradients in MT, which may reflect the reversal of patterns observed in development. We confirmed an anterior-to-posterior gradient of age-related MT decrease and also showed a lateral-to-ventral gradient inversely mirroring the sequence of connectivity development and myelination. MT concentration in the lateral white matter regions continued to increase up to the age of 45 years and decreased moderately following a peak. In contrast, ventral white matter regions reflected life-long stable MT concentration levels, followed by a rapid decrease at a later age. We discussed our findings in relation with existing theories of brain aging, including the lack of support for the proposal that areas which mature later decline at an accelerated rate.
Collapse
Affiliation(s)
- Vyacheslav R Karolis
- FMRIB centre, John Radcliffe Hospital, University of Oxford, Oxford, UK; Institute of Psychiatry, Psychology, and Neuroscience, King's College London, London, UK.
| | - Martina F Callaghan
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, London, UK
| | - Chieh-En Jane Tseng
- Institute of Psychiatry, Psychology, and Neuroscience, King's College London, London, UK; Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, USA
| | - Thomas Hope
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, London, UK
| | - Nikolaus Weiskopf
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, London, UK; Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Geraint Rees
- UCL Institute of Cognitive Neuroscience, London, UK
| | - Marinella Cappelletti
- UCL Institute of Cognitive Neuroscience, London, UK; Psychology Department, Goldsmiths University of London, London, UK
| |
Collapse
|
18
|
Melloni EMT, Poletti S, Vai B, Bollettini I, Colombo C, Benedetti F. Effects of illness duration on cognitive performances in bipolar depression are mediated by white matter microstructure. J Affect Disord 2019; 249:175-182. [PMID: 30772745 DOI: 10.1016/j.jad.2019.02.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 01/31/2019] [Accepted: 02/05/2019] [Indexed: 01/01/2023]
Abstract
BACKGROUND Cognitive deficits are a core feature of bipolar disorder (BD), and persist during the euthymic phase. White matter (WM) microstructural abnormalities are widely considered a structural marker of BD. Features of illness chronicity, such as illness duration and number of mood episodes, have been associated with worsening of both clinical profile and brain structural alterations. This study examined the role of WM integrity as a possible mediator between illness duration and cognitive performances in a sample of BD patients. METHODS We assessed 88 inpatients affected by a depressive episode in course of type I BD for verbal memory, visual memory, working memory, visuospatial constructional abilities, psychomotor coordination, executive functions, processing speed, and verbal fluency. White matter integrity was evaluated through FA measurements derived using the Enhancing Neuro Imaging Genetics Through Meta-Analysis (ENIGMA)-DTI protocol. RESULTS The effect of illness duration on processing speed, verbal memory, and visual memory was mediated by the FA values of bilateral anterior corona radiata, bilateral corona radiata, genu of corpus callosum, and fornix, adjusting for age, sex, education and lithium treatment (p < 0.05). LIMITATIONS Potential interaction factors were not examined in this study. CONCLUSIONS This is the first study to show the role of WM integrity as a mediator of the negative effect of illness duration on cognitive performances. Our data provide new insight into the neuroprogressive hypothesis of BD.
Collapse
Affiliation(s)
| | - Sara Poletti
- University Vita-Salute San Raffaele, Milano, Italy
| | - Benedetta Vai
- Psychiatry & Clinical Psychobiology, Division of Neuroscience, Scientific Institute Ospedale San Raffaele, Milano, Italy
| | - Irene Bollettini
- Psychiatry & Clinical Psychobiology, Division of Neuroscience, Scientific Institute Ospedale San Raffaele, Milano, Italy
| | | | | |
Collapse
|
19
|
Affiliation(s)
- Jutta Billino
- Abteilung Allgemeine Psychologie, Justus-Liebig-Universität Gießen, Gießen, Germany
| | - Karin S. Pilz
- Faculty of Behavioural and Social Sciences, University of Groningen, Groningen, The Netherlands
| |
Collapse
|
20
|
Seixas AI, Azevedo MM, Paes de Faria J, Fernandes D, Mendes Pinto I, Relvas JB. Evolvability of the actin cytoskeleton in oligodendrocytes during central nervous system development and aging. Cell Mol Life Sci 2019; 76:1-11. [PMID: 30302529 PMCID: PMC11105620 DOI: 10.1007/s00018-018-2915-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 08/24/2018] [Accepted: 09/04/2018] [Indexed: 01/23/2023]
Abstract
The organization of actin filaments into a wide range of subcellular structures is a defining feature of cell shape and dynamics, important for tissue development and homeostasis. Nervous system function requires morphological and functional plasticity of neurons and glial cells, which is largely determined by the dynamic reorganization of the actin cytoskeleton in response to intrinsic and extracellular signals. Oligodendrocytes are specialized glia that extend multiple actin-based protrusions to form the multilayered myelin membrane that spirally wraps around axons, increasing conduction speed and promoting long-term axonal integrity. Myelination is a remarkable biological paradigm in development, and maintenance of myelin is essential for a healthy adult nervous system. In this review, we discuss how structure and dynamics of the actin cytoskeleton is a defining feature of myelinating oligodendrocytes' biology and function. We also review "old and new" concepts to reflect on the potential role of the cytoskeleton in balancing life and death of myelin membranes and oligodendrocytes in the aging central nervous system.
Collapse
Affiliation(s)
- Ana Isabel Seixas
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal.
- IBMC - Instituto de Biologia Molecular e Celular, Porto, Portugal.
| | - Maria Manuela Azevedo
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal
- IBMC - Instituto de Biologia Molecular e Celular, Porto, Portugal
| | - Joana Paes de Faria
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal
- IBMC - Instituto de Biologia Molecular e Celular, Porto, Portugal
| | - Diogo Fernandes
- Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
- International Iberian Nanotechnology Laboratory - INL, Braga, Portugal
| | - Inês Mendes Pinto
- International Iberian Nanotechnology Laboratory - INL, Braga, Portugal
| | - João Bettencourt Relvas
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135, Porto, Portugal
- IBMC - Instituto de Biologia Molecular e Celular, Porto, Portugal
- The Discoveries Centre for Regeneration and Precision Medicine, Porto Campus, Porto, Portugal
| |
Collapse
|
21
|
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.
Collapse
|
22
|
Moore TL, Bowley B, Shultz P, Calderazzo S, Shobin E, Killiany RJ, Rosene DL, Moss MB. Chronic curcumin treatment improves spatial working memory but not recognition memory in middle-aged rhesus monkeys. GeroScience 2017; 39:571-584. [PMID: 29047012 PMCID: PMC5745216 DOI: 10.1007/s11357-017-9998-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 10/02/2017] [Indexed: 12/15/2022] Open
Abstract
Studies of both humans and non-human primates have demonstrated that aging is typically characterized by a decline in cognition that can occur as early as the fifth decade of life. Age-related changes in working memory are particularly evident and mediated, in part, by the prefrontal cortex, an area known to evidence age-related changes in myelin that is attributed to inflammation. In recent years, several nutraceuticals, including curcumin, by virtue of their anti-inflammatory and antioxidant effects, have received considerable attention as potential treatments for age-related cognitive decline and inflammation. Accordingly, we assessed for the first time in a non-human primate model of normal aging the efficacy of dietary intervention using the natural phenol curcumin to ameliorate the effects of aging on spatial working and recognition memory. Results revealed that monkeys receiving daily administration of curcumin over 14-18 months demonstrated a greater improvement in performance on repeated administration of a task of spatial working memory compared to monkeys that received a control substance.
Collapse
Affiliation(s)
- Tara L Moore
- Department of Anatomy & Neurobiology, Boston University School of Medicine, 72 E. Concord Street, L-1004, Boston, MA, 02118, USA.
- Department of Neurology, Boston University School of Medicine, 725 Albany Street, Boston, MA, 02118, USA.
| | - Bethany Bowley
- Department of Anatomy & Neurobiology, Boston University School of Medicine, 72 E. Concord Street, L-1004, Boston, MA, 02118, USA
| | - Penny Shultz
- Department of Anatomy & Neurobiology, Boston University School of Medicine, 72 E. Concord Street, L-1004, Boston, MA, 02118, USA
| | - Samantha Calderazzo
- Department of Anatomy & Neurobiology, Boston University School of Medicine, 72 E. Concord Street, L-1004, Boston, MA, 02118, USA
| | - Eli Shobin
- Department of Anatomy & Neurobiology, Boston University School of Medicine, 72 E. Concord Street, L-1004, Boston, MA, 02118, USA
- Graduate Program in Neuroscience, Boston University School of Medicine, 72 E. Concord Street, Boston, MA, 02118, USA
| | - Ronald J Killiany
- Department of Anatomy & Neurobiology, Boston University School of Medicine, 72 E. Concord Street, L-1004, Boston, MA, 02118, USA
- Department of Neurology, Boston University School of Medicine, 725 Albany Street, Boston, MA, 02118, USA
| | - Douglas L Rosene
- Department of Anatomy & Neurobiology, Boston University School of Medicine, 72 E. Concord Street, L-1004, Boston, MA, 02118, USA
- Yerkes National Primate Research Center, Emory University, 201 Dowman Drive, Atlanta, GA, 30322, USA
| | - Mark B Moss
- Department of Anatomy & Neurobiology, Boston University School of Medicine, 72 E. Concord Street, L-1004, Boston, MA, 02118, USA
- Department of Neurology, Boston University School of Medicine, 725 Albany Street, Boston, MA, 02118, USA
- Yerkes National Primate Research Center, Emory University, 201 Dowman Drive, Atlanta, GA, 30322, USA
| |
Collapse
|
23
|
Rowley CD, Sehmbi M, Bazin PL, Tardif CL, Minuzzi L, Frey BN, Bock NA. Age-related mapping of intracortical myelin from late adolescence to middle adulthood using T 1 -weighted MRI. Hum Brain Mapp 2017; 38:3691-3703. [PMID: 28462512 DOI: 10.1002/hbm.23624] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 04/10/2017] [Accepted: 04/12/2017] [Indexed: 12/11/2022] Open
Abstract
Magnetic resonance imaging (MRI) studies in humans have reported that the T1 -weighted signal in the cerebral cortex follows an inverted "U" trajectory over the lifespan. Here, we investigated the T1 -weighted signal trajectory from late adolescence to middle adulthood in humans to characterize the age range when mental illnesses tend to present, and efficacy of treatments are evaluated. We compared linear to quadratic predictors of age on signal in 67 healthy individuals, 17-45 years old. We investigated ¼, ½, and ¾ depths in the cortex representing intracortical myelin (ICM), in the superficial white matter (SWM), and in a reference deep white matter tract. We found that the quadratic fit was superior in all regions of the cortex, while signal in the SWM and deep white matter showed no global dependence on age over this range. The signal trajectory in any region followed a similar shape regardless of cortical depth. The quadratic fit was analyzed in 70 cortical regions to obtain the age of maximum signal intensity. We found that visual, cingulate, and left ventromedial prefrontal cortices peak first around 34 years old, whereas motor and premotor areas peak latest at ∼38 years. Our analysis suggests that ICM trajectories over this range can be modeled well in small cohorts of subjects using quadratic functions, which are amenable to statistical analysis, thus suitable for investigating regional changes in ICM with disease. This study highlights a novel approach to map ICM trajectories using an age range that coincides with the onset of many mental illnesses. Hum Brain Mapp 38:3691-3703, 2017. © 2017 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Christopher D Rowley
- McMaster Integrative Neuroscience Discovery and Study Program, McMaster University, Hamilton, Ontario, L8S 4K1, Canada
| | - Manpreet Sehmbi
- McMaster Integrative Neuroscience Discovery and Study Program, McMaster University, Hamilton, Ontario, L8S 4K1, Canada
| | - Pierre-Louis Bazin
- Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, 04103, Germany
| | - Christine L Tardif
- Brain Imaging Centre, Douglas Mental Health Institute; Department of Psychiatry, McGill University, Montreal, Quebec, H4H 1R3, Canada
| | - Luciano Minuzzi
- McMaster Integrative Neuroscience Discovery and Study Program, McMaster University, Hamilton, Ontario, L8S 4K1, Canada.,Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, L8S 4K1, Canada.,Mood Disorders Program and Women's Health Concerns Clinic, St. Joseph's Healthcare, Hamilton, Ontario, L8K 3K7, Canada
| | - Benicio N Frey
- McMaster Integrative Neuroscience Discovery and Study Program, McMaster University, Hamilton, Ontario, L8S 4K1, Canada.,Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, L8S 4K1, Canada.,Mood Disorders Program and Women's Health Concerns Clinic, St. Joseph's Healthcare, Hamilton, Ontario, L8K 3K7, Canada
| | - Nicholas A Bock
- McMaster Integrative Neuroscience Discovery and Study Program, McMaster University, Hamilton, Ontario, L8S 4K1, Canada.,Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, Ontario, L8S 4K1, Canada
| |
Collapse
|
24
|
Hsu A, Luebke JI, Medalla M. Comparative ultrastructural features of excitatory synapses in the visual and frontal cortices of the adult mouse and monkey. J Comp Neurol 2017; 525:2175-2191. [PMID: 28256708 DOI: 10.1002/cne.24196] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 01/18/2017] [Accepted: 02/10/2017] [Indexed: 01/20/2023]
Abstract
The excitatory glutamatergic synapse is the principal site of communication between cortical pyramidal neurons and their targets, a key locus of action of many drugs, and highly vulnerable to dysfunction and loss in neurodegenerative disease. A detailed knowledge of the structure of these synapses in distinct cortical areas and across species is a prerequisite for understanding the anatomical underpinnings of cortical specialization and, potentially, selective vulnerability in neurological disorders. We used serial electron microscopy to assess the ultrastructural features of excitatory (asymmetric) synapses in the layers 2-3 (L2-3) neuropil of visual (V1) and frontal (FC) cortices of the adult mouse and compared findings to those in the rhesus monkey (V1 and lateral prefrontal cortex [LPFC]). Analyses of multiple ultrastructural variables revealed four organizational features. First, the density of asymmetric synapses does not differ between frontal and visual cortices in either species, but is significantly higher in mouse than in monkey. Second, the structural properties of asymmetric synapses in mouse V1 and FC are nearly identical, by stark contrast to the significant differences seen between monkey V1 and LPFC. Third, while the structural features of postsynaptic entities in mouse and monkey V1 do not differ, the size of presynaptic boutons are significantly larger in monkey V1. Fourth, both presynaptic and postsynaptic entities are significantly smaller in the mouse FC than in the monkey LPFC. The diversity of synaptic ultrastructural features demonstrated here have broad implications for the nature and efficacy of glutamatergic signaling in distinct cortical areas within and across species.
Collapse
Affiliation(s)
- Alexander Hsu
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, Massachusetts
| | - Jennifer I Luebke
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, Massachusetts
| | - Maria Medalla
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, Massachusetts
| |
Collapse
|
25
|
Venkatesh H, Monje M. Neuronal Activity in Ontogeny and Oncology. Trends Cancer 2017; 3:89-112. [PMID: 28718448 DOI: 10.1016/j.trecan.2016.12.008] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 12/29/2016] [Accepted: 12/30/2016] [Indexed: 01/06/2023]
Abstract
The nervous system plays a central role in regulating the stem cell niche in many organs, and thereby pivotally modulates development, homeostasis, and plasticity. A similarly powerful role for neural regulation of the cancer microenvironment is emerging. Neurons promote the growth of cancers of the brain, skin, prostate, pancreas, and stomach. Parallel mechanisms shared in development and cancer suggest that neural modulation of the tumor microenvironment may prove a universal theme, although the mechanistic details of such modulation remain to be discovered for many malignancies. We review here what is known about the influences of active neurons on stem cell and cancer microenvironments across a broad range of tissues, and we discuss emerging principles of neural regulation of development and cancer.
Collapse
Affiliation(s)
- Humsa Venkatesh
- Department of Neurology, Stanford University School of Medicine, Stanford, CA, USA; Cancer Biology Graduate Program, Stanford University School of Medicine, Stanford, CA, USA
| | - Michelle Monje
- Department of Neurology, Stanford University School of Medicine, Stanford, CA, USA; Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, USA; Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Stanford, CA, USA.
| |
Collapse
|
26
|
Stereological quantification of age-related changes in myelinated fibers of rat white matter. Neuroreport 2017; 28:42-49. [PMID: 27902556 DOI: 10.1097/wnr.0000000000000706] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We investigated changes in myelin sheaths in the myelinated fibers of subcortical white matter in young (6-8 months old), middle-aged (18 months old), and elderly (27-28 months old) female Long-Evans rats using transmission electron microscopy and unbiased stereological techniques. We observed three age-related changes in myelin sheaths in the white matter of elderly rats: local splitting of the major dense line, myelin ballooning, and the formation of abundant myelin sheaths. Stereological analysis showed that the total length of myelinated fibers in white matter was 115±12 km (mean±SD) in young rats, 135±21 km in middle-aged rats, and 62±11 km in elderly rats. Myelinated fibers with diameters less than 1.0 μm and myelin sheath thicknesses less than 0.1 μm were significantly shorter in middle-aged and elderly rats compared with young rats. Age-related changes in myelin sheaths were evident in aged white matter. The loss of myelinated fibers with both small diameters and thin myelin sheaths is a potentially important change in aged white matter. Our results suggest that the myelin sheath changes in aged white matter may have important implications for age-related cognitive impairments.
Collapse
|
27
|
Lawrenz M, Brassen S, Finsterbusch J. Microscopic diffusion anisotropy in the human brain: Age-related changes. Neuroimage 2016; 141:313-325. [DOI: 10.1016/j.neuroimage.2016.07.031] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 06/18/2016] [Accepted: 07/13/2016] [Indexed: 11/16/2022] Open
|
28
|
Zhu F, Gatti DL, Yang KH. Nodal versus Total Axonal Strain and the Role of Cholesterol in Traumatic Brain Injury. J Neurotrauma 2015; 33:859-70. [PMID: 26393780 DOI: 10.1089/neu.2015.4007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Traumatic brain injury (TBI) is a health threat that affects every year millions of people involved in motor vehicle and sporting accidents, and thousands of soldiers in battlefields. Diffuse axonal injury (DAI) is one of the most frequent types of TBI leading to death. In DAI, the initial traumatic event is followed by a cascade of biochemical changes that take time to develop in full, so that symptoms may not become apparent until days or weeks after the original injury. Hence, DAI is a dynamic process, and the opportunity exists to prevent its progression provided the initial trauma can be predicted at the molecular level. Here, we present preliminary evidence from micro-finite element (FE) simulations that the mechanical response of central nervous system myelinated fibers is dependent on the axonal diameter, the ratio between axon diameter and fiber diameter (g-ratio), the microtubules density, and the cholesterol concentration in the axolemma and myelin. A key outcome of the simulations is that there is a significant difference between the overall level of strain in a given axonal segment and the level of local strain in the Ranvier nodes contained in that segment, with the nodal strain being much larger than the total strain. We suggest that the acquisition of this geometric and biochemical information by means of already available high resolution magnetic resonance imaging techniques, and its incorporation in current FE models of the brain will enhance the models capacity to predict the site and magnitude of primary axonal damage upon TBI.
Collapse
Affiliation(s)
- Feng Zhu
- 1 Department of Biomedical Engineering, Wayne State University , Detroit, Michigan
| | - Domenico L Gatti
- 2 Department of Biochemistry and Molecular Biology, Wayne State University , Detroit, Michigan.,3 CardioVascular Research Institute, Wayne State University , Detroit, Michigan
| | - King H Yang
- 1 Department of Biomedical Engineering, Wayne State University , Detroit, Michigan
| |
Collapse
|
29
|
Siu CR, Balsor JL, Jones DG, Murphy KM. Classic and Golli Myelin Basic Protein have distinct developmental trajectories in human visual cortex. Front Neurosci 2015; 9:138. [PMID: 25964736 PMCID: PMC4408849 DOI: 10.3389/fnins.2015.00138] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 04/02/2015] [Indexed: 01/03/2023] Open
Abstract
Traditionally, myelin is viewed as insulation around axons, however, more recent studies have shown it also plays an important role in plasticity, axonal metabolism, and neuroimmune signaling. Myelin is a complex multi-protein structure composed of hundreds of proteins, with Myelin Basic Protein (MBP) being the most studied. MBP has two families: Classic-MBP that is necessary for activity driven compaction of myelin around axons, and Golli-MBP that is found in neurons, oligodendrocytes, and T-cells. Furthermore, Golli-MBP has been called a “molecular link” between the nervous and immune systems. In visual cortex specifically, myelin proteins interact with immune processes to affect experience-dependent plasticity. We studied myelin in human visual cortex using Western blotting to quantify Classic- and Golli-MBP expression in post-mortem tissue samples ranging in age from 20 days to 80 years. We found that Classic- and Golli-MBP have different patterns of change across the lifespan. Classic-MBP gradually increases to 42 years and then declines into aging. Golli-MBP has early developmental changes that are coincident with milestones in visual system sensitive period, and gradually increases into aging. There are three stages in the balance between Classic- and Golli-MBP expression, with Golli-MBP dominating early, then shifting to Classic-MBP, and back to Golli-MBP in aging. Also Golli-MBP has a wave of high inter-individual variability during childhood. These results about cortical MBP expression are timely because they compliment recent advances in MRI techniques that produce high resolution maps of cortical myelin in normal and diseased brain. In addition, the unique pattern of Golli-MBP expression across the lifespan suggests that it supports high levels of neuroimmune interaction in cortical development and in aging.
Collapse
Affiliation(s)
- Caitlin R Siu
- McMaster Integrative Neuroscience Discovery and Study Program, McMaster University Hamilton, ON, Canada
| | - Justin L Balsor
- McMaster Integrative Neuroscience Discovery and Study Program, McMaster University Hamilton, ON, Canada
| | | | - Kathryn M Murphy
- McMaster Integrative Neuroscience Discovery and Study Program, McMaster University Hamilton, ON, Canada ; Psychology, Neuroscience and Behaviour, McMaster University Hamilton, ON, Canada
| |
Collapse
|
30
|
Diversity of glutamatergic synaptic strength in lateral prefrontal versus primary visual cortices in the rhesus monkey. J Neurosci 2015; 35:112-27. [PMID: 25568107 DOI: 10.1523/jneurosci.3426-14.2015] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Understanding commonalities and differences in glutamatergic synaptic signaling is essential for understanding cortical functional diversity, especially in the highly complex primate brain. Previously, we have shown that spontaneous EPSCs differed markedly in layer 3 pyramidal neurons of two specialized cortical areas in the rhesus monkey, the high-order lateral prefrontal cortex (LPFC) and the primary visual cortex (V1). Here, we used patch-clamp recordings and confocal and electron microscopy to determine whether these distinct synaptic responses are due to differences in firing rates of presynaptic neurons and/or in the features of presynaptic or postsynaptic entities. As with spontaneous EPSCs, TTX-insensitive (action potential-independent) miniature EPSCs exhibited significantly higher frequency, greater amplitude, and slower kinetics in LPFC compared with V1 neurons. Consistent with these physiological differences, LPFC neurons possessed higher densities of spines, and the mean width of large spines was greater compared with those on V1 neurons. Axospinous synapses in layers 2-3 of LPFC had larger postsynaptic density surface areas and a higher proportion of large perforated synapses compared with V1. Axonal boutons in LPFC were also larger in volume and contained ∼ 1.6× more vesicles than did those in V1. Further, LPFC had a higher density of AMPA GluR2 receptor labeling than V1. The properties of spines and synaptic currents of individual layer 3 pyramidal neurons measured here were significantly correlated, consistent with the idea that significantly more frequent and larger synaptic currents are likely due to more numerous, larger, and more powerful synapses in LPFC compared with V1.
Collapse
|
31
|
Rizzo V, Richman J, Puthanveettil SV. Dissecting mechanisms of brain aging by studying the intrinsic excitability of neurons. Front Aging Neurosci 2015; 6:337. [PMID: 25610394 PMCID: PMC4285138 DOI: 10.3389/fnagi.2014.00337] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 11/29/2014] [Indexed: 01/30/2023] Open
Abstract
Several studies using vertebrate and invertebrate animal models have shown aging associated changes in brain function. Importantly, changes in soma size, loss or regression of dendrites and dendritic spines and alterations in the expression of neurotransmitter receptors in specific neurons were described. Despite this understanding, how aging impacts intrinsic properties of individual neurons or circuits that govern a defined behavior is yet to be determined. Here we discuss current understanding of specific electrophysiological changes in individual neurons and circuits during aging.
Collapse
Affiliation(s)
- Valerio Rizzo
- Department of Neuroscience, The Scripps Research Institute Jupiter, FL, USA
| | - Jeffrey Richman
- Department of Neuroscience, The Scripps Research Institute Jupiter, FL, USA
| | | |
Collapse
|
32
|
Yuan N, Liang Z, Yang Y, Li G, Zhou Y. Changes of spatial and temporal frequency tuning properties of neurons in the middle temporal area of aged rhesus monkeys. Eur J Neurosci 2014; 40:2652-61. [PMID: 24888415 DOI: 10.1111/ejn.12634] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Revised: 04/11/2014] [Accepted: 04/25/2014] [Indexed: 11/30/2022]
Abstract
Aged humans exhibit severe deficits in visual motion perception and contrast sensitivity under various levels of spatial and temporal modulation. Previous studies indicated that many of these deficits are probably mediated by the neural degradation of the central visual system. To clarify the neuronal response mechanisms underlying the visual degradation during aging, we examined the spatial and temporal frequency tuning properties of neurons from anesthetised and paralysed aged monkeys at the middle temporal area (area MT), which is downstream of the primary visual cortex in the visual processing pathway and thought to be critical for motion perception. We found that the preferred spatial and temporal frequencies, spatial resolution and high temporal frequency cutoff of area MT neurons were reduced in aged monkeys, and were accompanied by the broadened tuning width of spatial frequency, elevated spontaneous activity, and decreased signal-to-noise ratio. These results showed that, for neurons in area MT, aging significantly changed both the spatial and temporal frequency response tuning properties. Such evidence provides new insight into the changes occurring at the electrophysiological level that may be related to the aging-related visual deficits, especially in processing spatial and temporal information.
Collapse
Affiliation(s)
- Nini Yuan
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, China
| | | | | | | | | |
Collapse
|
33
|
Xie F, Liang P, Fu H, Zhang JC, Chen J. Effects of normal aging on myelin sheath ultrastructures in the somatic sensorimotor system of rats. Mol Med Rep 2014; 10:459-66. [PMID: 24818843 DOI: 10.3892/mmr.2014.2228] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2013] [Accepted: 04/01/2014] [Indexed: 11/06/2022] Open
Abstract
Previous studies have presented qualitative and quantitative data regarding the morphological changes that occur peripherally in myelin sheaths and nerve fibers of rats during their lifespan. However, studies on ultrastructural features of myelinated fibers (MFs) in the central nervous system (CNS) remain limited. In the present study, morphological analyses of the somatic sensorimotor MFs in rats at time‑points between postnatal day 14 and postnatal month (PNM) 26 were conducted using electron microscopy. Significant alterations in the myelin sheath were observed in the sensorimotor system of aging and aged rats, which became aggravated with age. The ultrastructural pattern of myelin lamellae also exhibited age dependence. The transformation of the myelin intraperiod line from complete to incomplete fusion occurred after PNM 5, leading to an expansion of periodicity in myelin lamellae. These pathological changes in the myelin structure occurred very early and showed a significant correlation with age, indicating that myelin was the part of the CNS with the highest susceptibility to the influence of aging, and may be the main target of aging effects. In addition to the myelin breakdown, continued myelin production and remyelination were observed in the aging sensorimotor system, suggesting the presence of endogenous mechanisms of myelin repair.
Collapse
Affiliation(s)
- Fang Xie
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, The Fourth Military Medical University, Xi'an, Shaanxi 710038, P.R. China
| | - Ping Liang
- School of Pharmacy, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Han Fu
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, The Fourth Military Medical University, Xi'an, Shaanxi 710038, P.R. China
| | - Jiu-Cong Zhang
- Department of Gastroenterology, Lanzhou General Hospital of Lanzhou Military Command, Lanzhou, Gansu 730050, P.R. China
| | - Jun Chen
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, The Fourth Military Medical University, Xi'an, Shaanxi 710038, P.R. China
| |
Collapse
|
34
|
Lu W, Yang S, Chen L, Qiu X, Huang CX, Wu H, Li C, Yang JQ, Zhang L, Chao FL, Tang Y. Stereological investigation of the age-related changes of the myelinated fibers in the hippocampus of male rats. Anat Rec (Hoboken) 2014; 297:1490-7. [PMID: 24782353 DOI: 10.1002/ar.22936] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2014] [Accepted: 03/18/2014] [Indexed: 11/08/2022]
Abstract
The decline of hippocampus-dependent learning and memory during normal aging is not associated with neuron death and synapse loss. Until now, age-related changes in the myelinated fibers of the hippocampus have not been investigated. Therefore, in this study, the myelinated fibers in the hippocampi of young (6 months), middle-aged (18 months), and old-aged (28 months) male Sprague-Dawley rats were studied with transmission electron microscope and stereological methods, following spatial learning tests in a Morris water maze. The results showed that hippocampus-dependent spatial learning was impaired in old-aged rats but that the total volume, length, and mean diameter of the myelinated fibers in the hippocampus, as well as the hippocampal volume, remained constant during the normal aging process. Our results suggest that the age-related decline in hippocampus-dependent spatial learning is not attributable to myelinated fiber changes in the hippocampus and that other, undetermined factors are responsible.
Collapse
Affiliation(s)
- Wei Lu
- Department of Histology and Embryology, Chongqing Medical University, Chongqing, People's Republic of China; Department of Pediatrics, Navy General Hospital, Beijing, People's Republic of China
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
35
|
Intracortical myelin links with performance variability across the human lifespan: results from T1- and T2-weighted MRI myelin mapping and diffusion tensor imaging. J Neurosci 2014; 33:18618-30. [PMID: 24259583 DOI: 10.1523/jneurosci.2811-13.2013] [Citation(s) in RCA: 201] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Cerebral myelin maturation and aging-related degradation constitute fundamental features of human brain integrity and functioning. Although mostly studied in the white matter, the cerebral cortex contains significant amounts of myelinated axons. However, how intracortical myelin content evolves during development, decays in aging, and links with cognition remain poorly understood. Several studies have shown the potential of mapping myelin in the cortex by use of T1-weighted (T1w) and T2-weighted (T2w) magnetic resonance imaging signal intensity, which show inverse sensitivity to myelin. Here, we characterized cortical myelin in 339 participants 8-83 years of age using a recently introduced T1w/T2w ratio myelin mapping technique and mean diffusivity (MD) from diffusion tensor imaging. To test for cognitive correlates, we used intraindividual variability (IIV) in performance during a speeded task, a measure recently associated with white matter integrity. The results showed that intracortical myelin maturation was ongoing until the late 30s, followed by 20 relative stable years before declining from the late 50s. For MD, U-shaped paths showing similar patterns were observed, but with fewer maturational effects in some regions. IIV was correlated with both T1w/T2w ratio and MD, mainly indicating that the higher degree of intracortical myelin is associated with greater performance stability. The relations were more prominent with advancing age, suggesting that aging-related cortical demyelination contributes to increased IIV. The T1w/T2w ratio myelin-mapping technique thus seems sensitive to intracortical myelin content in normal development and aging, relates to cognitive functioning, and might constitute an important future tool in mapping normal and clinical brain changes.
Collapse
|
36
|
Luebke JI, Medalla M, Amatrudo JM, Weaver CM, Crimins JL, Hunt B, Hof PR, Peters A. Age-related changes to layer 3 pyramidal cells in the rhesus monkey visual cortex. Cereb Cortex 2013; 25:1454-68. [PMID: 24323499 DOI: 10.1093/cercor/bht336] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The effects of normal aging on morphologic and electrophysiologic properties of layer 3 pyramidal neurons in rhesus monkey primary visual cortex (V1) were assessed with whole-cell, patch-clamp recordings in in vitro slices. In another cohort of monkeys, the ultrastructure of synapses in the layers 2-3 neuropil of V1 was assessed using electron microscopy. Distal apical dendritic branching complexity was reduced in aged neurons, as was the total spine density, due to specific loss of mushroom spines from the apical tree and of thin spines from the basal tree. There was also an age-related decrease in the numerical density of symmetric and asymmetric synapses. In contrast to these structural changes, intrinsic membrane, action potential (AP), and excitatory and inhibitory synaptic current properties were the same in aged and young neurons. Computational modeling using morphologic reconstructions predicts that reduced dendritic complexity leads to lower attenuation of voltage outward from the soma (e.g., backpropagating APs) in aged neurons. Importantly, none of the variables that changed with age differed in neurons from cognitively impaired versus unimpaired aged monkeys. In summary, there are age-related alterations to the structural properties of V1 neurons, but these are not associated with significant electrophysiologic changes or with cognitive decline.
Collapse
Affiliation(s)
- Jennifer I Luebke
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118, USA Computational Neurobiology and Imaging Center, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA and
| | - Maria Medalla
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118, USA
| | | | - Christina M Weaver
- Computational Neurobiology and Imaging Center, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA and Department of Mathematics, Franklin and Marshall College, Lancaster, PA 17604, USA
| | | | - Brendan Hunt
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118, USA
| | - Patrick R Hof
- Fishberg Department of Neuroscience and Friedman Brain Institute Computational Neurobiology and Imaging Center, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA and
| | - Alan Peters
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118, USA
| |
Collapse
|
37
|
Bieniek MM, Frei LS, Rousselet GA. Early ERPs to faces: aging, luminance, and individual differences. Front Psychol 2013; 4:268. [PMID: 23717297 PMCID: PMC3653118 DOI: 10.3389/fpsyg.2013.00268] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 04/25/2013] [Indexed: 11/13/2022] Open
Abstract
Recently, Rousselet et al. reported a 1 ms/year delay in visual processing speed in a sample of healthy aged 62 subjects (Frontiers in Psychology 2010, 1:19). Here, we replicate this finding in an independent sample of 59 subjects and investigate the contribution of optical factors (pupil size and luminance) to the age-related slowdown and to individual differences in visual processing speed. We conducted two experiments. In experiment 1 we recorded EEG from subjects aged 18–79. Subjects viewed images of faces and phase scrambled noise textures under nine luminance conditions, ranging from 0.59 to 60.8 cd/m2. We manipulated luminance using neutral density filters. In experiment 2, 10 young subjects (age < 35) viewed similar stimuli through pinholes ranging from 1 to 5 mm. In both experiments, subjects were tested twice. We found a 1 ms/year slowdown in visual processing that was independent of luminance. Aging effects became visible around 125 ms post-stimulus and did not affect the onsets of the face-texture ERP differences. Furthermore, luminance modulated the entire ERP time-course from 60 to 500 ms. Luminance effects peaked in the N170 time window and were independent of age. Importantly, senile miosis and individual differences in pupil size did not account for aging differences and inter-subject variability in processing speed. The pinhole manipulation also failed to match the ERPs of old subjects to those of young subjects. Overall, our results strongly suggest that early ERPs to faces (<200 ms) are delayed by aging and that these delays are of cortical, rather than optical origin. Our results also demonstrate that even late ERPs to faces are modulated by low-level factors.
Collapse
Affiliation(s)
- Magdalena M Bieniek
- Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow Glasgow, UK
| | | | | |
Collapse
|
38
|
Labadie C, Lee JH, Rooney WD, Jarchow S, Aubert-Frécon M, Springer CS, Möller HE. Myelin water mapping by spatially regularized longitudinal relaxographic imaging at high magnetic fields. Magn Reson Med 2013; 71:375-87. [PMID: 23468414 DOI: 10.1002/mrm.24670] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2012] [Revised: 01/09/2013] [Accepted: 01/10/2013] [Indexed: 11/07/2022]
Affiliation(s)
- Christian Labadie
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; Laboratoire de Spectrométrie Ionique et Moléculaire, Université Claude-Bernard, Lyon, France; Faculty of Physics and Earth Sciences, University of Leipzig, Leipzig, Germany
| | | | | | | | | | | | | |
Collapse
|
39
|
Yang S, Li C, Qiu X, Zhang L, Lu W, Chen L, Zhao Y, Shi X, Huang C, Cheng G, Tang Y. Effects of an enriched environment on myelin sheaths in the white matter of rats during normal aging: A stereological study. Neuroscience 2013; 234:13-21. [DOI: 10.1016/j.neuroscience.2013.01.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 12/25/2012] [Accepted: 01/03/2013] [Indexed: 11/25/2022]
|
40
|
Bartzokis G, Lu PH, Heydari P, Couvrette A, Lee GJ, Kalashyan G, Freeman F, Grinstead JW, Villablanca P, Finn JP, Mintz J, Alger JR, Altshuler LL. Multimodal magnetic resonance imaging assessment of white matter aging trajectories over the lifespan of healthy individuals. Biol Psychiatry 2012; 72:1026-34. [PMID: 23017471 DOI: 10.1016/j.biopsych.2012.07.010] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2012] [Revised: 06/08/2012] [Accepted: 07/01/2012] [Indexed: 01/23/2023]
Abstract
BACKGROUND Postmortem and volumetric imaging data suggest that brain myelination is a dynamic lifelong process that, in vulnerable late-myelinating regions, peaks in middle age. We examined whether known regional differences in axon size and age at myelination influence the timing and rates of development and degeneration/repair trajectories of white matter (WM) microstructure biomarkers. METHODS Healthy subjects (n = 171) 14-93 years of age were examined with transverse relaxation rate (R(2)) and four diffusion tensor imaging measures (fractional anisotropy [FA] and radial, axial, and mean diffusivity [RD, AxD, MD, respectively]) of frontal lobe, genu, and splenium of the corpus callosum WM (FWM, GWM, and SWM, respectively). RESULTS Only R(2) reflected known levels of myelin content with high values in late-myelinating FWM and GWM regions and low ones in early-myelinating SWM. In FWM and GWM, all metrics except FA had significant quadratic components that peaked at different ages (R(2) < RD < MD < AxD), with FWM peaking later than GWM. Factor analysis revealed that, although they defined different factors, R(2) and RD were the metrics most closely associated with each other and differed from AxD, which entered into a third factor. CONCLUSIONS The R(2) and RD trajectories were most dynamic in late-myelinating regions and reflect age-related differences in myelination, whereas AxD reflects axonal size and extra-axonal space. The FA and MD had limited specificity. The data suggest that the healthy adult brain undergoes continual change driven by development and repair processes devoted to creating and maintaining synchronous function among neural networks on which optimal cognition and behavior depend.
Collapse
Affiliation(s)
- George Bartzokis
- Department of Psychiatry, The David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Peters A, Kemper T. A review of the structural alterations in the cerebral hemispheres of the aging rhesus monkey. Neurobiol Aging 2012; 33:2357-72. [PMID: 22192242 PMCID: PMC3337968 DOI: 10.1016/j.neurobiolaging.2011.11.015] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 11/02/2011] [Accepted: 11/10/2011] [Indexed: 02/07/2023]
Abstract
Like humans, rhesus monkeys show cognitive decline and this review considers what structural age-related changes underlie this decline. Some structural measures do not alter significantly with age. These include brain weight, overall cortical thickness; numbers of cortical neurons; and numbers of astrocytes and microglial cells. Other structural measures change with age, but the change does not correlate with cognitive decline. These changes include nerve fiber loss from some fiber tracts, degeneration, and regeneration of myelin sheaths, and increase in the frequency of oligodendrocytes. Among the structural measures that increase in frequency with age and also correlate with cognitive decline are the increased frequency of degenerating myelin sheaths and a loss of nerve fibers from some fiber tracts; and the loss of synapses and dendritic spines from upper layers of prefrontal cortex. Consequently, the existing data suggest that cognitive decline correlates with changes in myelinated nerve fibers and with disconnections between and within cortical areas, as reflected by the age-related loss of synapses and of dendritic spines from some cortical areas.
Collapse
Affiliation(s)
- Alan Peters
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118, USA.
| | | |
Collapse
|
42
|
Yang S, Lu W, Zhou DS, Tang Y. Enriched environment and white matter in aging brain. Anat Rec (Hoboken) 2012; 295:1406-14. [PMID: 22777883 DOI: 10.1002/ar.22526] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2012] [Accepted: 06/04/2012] [Indexed: 12/23/2022]
Abstract
Normal aging is commonly associated with decreased cognitive functions, which could be conspicuously alleviated by enriched environment (EE) with physical, social, and sensory stimuli, suggesting that aging brain still has intriguing plasticity. Multiple researches have been carried out to explore the structural and the molecular changes in aging brain, which would be considered for evidences that EE regulated brain plasticity. Because there is no significant neuron loss in aging cerebral cortex and the white matter is crucial for cognitive functions, this review focused on the age-related white matter changes and the effects of EE on aged white matter. Data from our stereology laboratory revealed that age-related spatial memory declines had more to do with white matter alterations, which were due to marked demyelination and loss of oligodendrocytes in the white matter. We also demonstrated that EE recovered spatial memory impairment and increased white matter volume by promoting marked remyelination in aged brain. This review approached the issue that EE might contribute to normal aging and be beneficial for those suffering from demyelinated diseases.
Collapse
Affiliation(s)
- Shu Yang
- Department of Histology and Embryology, Capital Medical University, Beijing 100069, People's Republic of China
| | | | | | | |
Collapse
|
43
|
Fibroblast growth factor receptor signaling in oligodendrocytes regulates myelin sheath thickness. J Neurosci 2012; 32:6631-41. [PMID: 22573685 DOI: 10.1523/jneurosci.6005-11.2012] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Formation of the CNS white matter is developmentally tightly regulated, but the molecules and mechanisms of myelination control in the postnatal CNS are poorly understood. Here, we show that myelin growth is controlled by fibroblast growth factor (FGF) signaling, originally identified as a proliferative signal for oligodendrocyte precursor cells (OPCs) in vitro. We created two lines of mice lacking both FGF receptor 1 (Fgfr1) and Fgfr2 in oligodendrocyte-lineage cells but found that in these mice OPC proliferation and differentiation were unaffected. In addition, axonal ensheathment and the initiation of myelination were on time. However, the rapid growth of CNS myelin, normally occurring in the second postnatal week, was strongly inhibited. Throughout adulthood, the myelin sheath remained disproportionately thin relative to the axon caliber. In adult mice, mutant oligodendrocytes were normal in number, whereas the transcription of major myelin genes was reduced. This FGF receptor-mediated stimulation of mature oligodendrocytes could also be modeled in vitro, demonstrating that enhanced expansion of oligodendroglial processes requires signaling by extracellular signal regulated kinase-1 and -2 (Erk1/2), downstream mediators of mitogen-activated protein kinase (MAPK). In vivo, Erk1/2-MAPK activity was reduced in the hypomyelinated CNS of Fgfr1/Fgfr2 mutant mice. These studies reveal a previously unrecognized function of FGF receptor signaling in oligodendrocytes that contributes to the regulation of myelin sheath thickness and that uncouples the initiation of ensheathment from the later phase of continued myelin growth.
Collapse
|
44
|
Abstract
To understand how normal variations in white matter relate to cognition, magnetization transfer imaging ratios (MTR) of a hypothesized neural network were associated with a test of visual selective attention (VST). Healthy adults (N = 16) without abnormal signal on brain scans viewed a version of DeSchepper and Treisman's test of VST (1996) with two levels of processing (novel shape matching with and without distractors, contingency feedback). A hypothesized neural network and component regions was significantly associated with accuracy and response times when distractors were present, with betas predicting 55% of variance in accuracy, and 59% of response times. MTR for anterior and posterior cingulate, prefrontal region, and thalami comprised a model predicting 55% of accuracy when distractors were present, and the anterior cingulate accounted for the majority of this effect. Prefrontal MTR predicted longer response times which was associated with increased accuracy. Distal neural areas involved in complex, processing-driven tasks (error processing, response selection, and variable response competition and processing load) may be dependent on white matter fibers to connect distal brain regions/nuclei of a macronetwork, including prefrontal executive functions.
Collapse
|
45
|
Shepherd MN, Pomicter AD, Velazco CS, Henderson SC, Dupree JL. Paranodal reorganization results in the depletion of transverse bands in the aged central nervous system. Neurobiol Aging 2012; 33:203.e13-24. [PMID: 20888080 PMCID: PMC3282488 DOI: 10.1016/j.neurobiolaging.2010.08.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Revised: 07/26/2010] [Accepted: 08/05/2010] [Indexed: 11/16/2022]
Abstract
Paranodal axo-glial junctional complexes anchor the myelin sheath to the axon and breakdown of these complexes presumably facilitates demyelination. Myelin deterioration is also prominent in the aging central nervous system (CNS); however, the stability of the paranodal complexes in the aged CNS has not been examined. Here, we show that transverse bands, prominent components of paranodal junctions, are significantly reduced in the aged CNS; however, the number of paired clusters of both myelin and axonal paranodal proteins is not altered. Ultrastructural analyses also reveal that thicker myelin sheaths display a "piling" of paranodal loops, the cytoplasm-containing sacs that demarcate the paranode. Loops involved in piling are observed throughout the paranode and are not limited to loops positioned in either the nodal- or juxtanodal-most regions. Here, we propose that as myelination continues, previously anchored loops lose their transverse bands and recede away from the axolemma. Newly juxtaposed loops then lose their transverse bands, move laterally to fill in the gap left by the receded loops and finally reform their transverse bands. This paranodal reorganization results in conservation of paranodal length, which may be important in maintaining ion channel spacing and axonal function. Furthermore, we propose that transverse band reformation is less efficient in the aged CNS, resulting in the significant reduction of these junctional components. Although demyelination was not observed, we propose that loss of transverse bands facilitates myelin degeneration and may predispose the aged CNS to a poorer prognosis following a secondary insult.
Collapse
Affiliation(s)
- Mark N. Shepherd
- Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, VA, USA 23298
- MD Biosciences, 2575 University Avenue W. Suite 100 St Paul, MN, USA 55114 (present address)
| | - Anthony D. Pomicter
- Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, VA, USA 23298
| | - Cristine S. Velazco
- Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, VA, USA 23298
| | - Scott C. Henderson
- Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, VA, USA 23298
| | - Jeffrey L. Dupree
- Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, VA, USA 23298
| |
Collapse
|
46
|
Lu PH, Thompson PM, Leow A, Lee GJ, Lee A, Yanovsky I, Parikshak N, Khoo T, Wu S, Geschwind D, Bartzokis G. Apolipoprotein E genotype is associated with temporal and hippocampal atrophy rates in healthy elderly adults: a tensor-based morphometry study. J Alzheimers Dis 2011; 23:433-42. [PMID: 21098974 DOI: 10.3233/jad-2010-101398] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Apolipoprotein E (ApoE) ε4 genotype is a strong risk factor for developing Alzheimer's disease (AD). Conversely, the presence of the ε2 allele has been shown to mitigate cognitive decline. Tensor-based morphometry (TBM), a novel computational approach for visualizing longitudinal progression of brain atrophy, was used to determine whether cognitively intact elderly participants with the ε4 allele demonstrate greater volume reduction than those with the ε2 allele. Healthy "younger elderly" volunteers, aged 55-75, were recruited from the community and hospital staff. They were evaluated with a baseline and follow-up MRI scan (mean scan interval = 4.72 years, s.d. = 0.55) and completed ApoE genotyping. Twenty-seven participants were included in the study of which 16 had the ε4 allele (all heterozygous ε3ε4 genotype) and 11 had the ε2ε3 genotype. The two groups did not differ significantly on any demographic characteristics and all subjects were cognitively "normal" at both baseline and follow-up time points. TBM was used to create 3D maps of local brain tissue atrophy rates for individual participants; these spatially detailed 3D maps were compared between the two ApoE groups. Regional analyses were performed and the ε4 group demonstrated significantly greater annual atrophy rates in the temporal lobes (p = 0.048) and hippocampus (p = 0.016); greater volume loss was observed in the right hippocampus than the left. TBM appears to be useful in tracking longitudinal progression of brain atrophy in cognitively asymptomatic adults. Possession of the ε4 allele is associated with greater temporal and hippocampal volume reduction well before the onset of cognitive deficits.
Collapse
Affiliation(s)
- Po H Lu
- Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-7226, USA.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
47
|
Lu PH, Lee GJ, Raven EP, Tingus K, Khoo T, Thompson PM, Bartzokis G. Age-related slowing in cognitive processing speed is associated with myelin integrity in a very healthy elderly sample. J Clin Exp Neuropsychol 2011; 33:1059-68. [PMID: 22133139 DOI: 10.1080/13803395.2011.595397] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Performance on measures of cognitive processing speed (CPS) slows with age, but the biological basis associated with this cognitive phenomenon remains incompletely understood. We assessed the hypothesis that the age-related slowing in CPS is associated with myelin breakdown in late-myelinating regions in a very healthy elderly population. An in vivo magnetic resonance imaging (MRI) biomarker of myelin integrity was obtained from the prefrontal lobe white matter and the genu of the corpus callosum for 152 healthy elderly adults. These regions myelinate later in brain development and are more vulnerable to breakdown due to the effects of normal aging. To evaluate regional specificity, we also assessed the splenium of the corpus callosum as a comparison region, which myelinates early in development and primarily contains axons involved in visual processing. The measure of myelin integrity was significantly correlated with CPS in highly vulnerable late-myelinating regions but not in the splenium. These results have implications for the neurobiology of the cognitive changes associated with brain aging.
Collapse
Affiliation(s)
- Po H Lu
- Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
| | | | | | | | | | | | | |
Collapse
|
48
|
Abstract
The effects of age on nerve fibers and neuroglial cells in the fornix were examined in 25 rhesus monkeys between 4 and 33 years of age. There is no age-related change in the cross-sectional area of the fornix, but there is a significant loss of myelinated nerve fibers. The loss of myelinated nerve fibers is accompanied by a significant increase in the numbers of nerve fibers that show degeneration of their axons and alterations in myelin sheaths. Aging also brings about an increase in the frequency of profiles of paranodes, indicating that some of the nerve fibers are being remyelinated. Aging also affects neuroglial cells. Each type shows inclusions in their perikarya, and in the case of astrocytes and microglial cells some of these inclusions are phagocytosed myelin. Numbers of astrocytes and microglial cells do not appear to increase with age, but there is a 20% increase in oligodendrocytes. When correlations with cognitive impairments displayed by individual monkeys are examined, the decreased packing density of nerve fibers and the increasing frequency of nerve fibers with degenerating axons and of nerve fibers with altered myelin sheaths all correlate with increasing cognitive impairment. It is suggested that these correlations result from some disconnection of the hippocampus from the thalamus, septal nuclei, and medial frontal cortex and from reductions in the conduction velocity brought about by the shorter internodal lengths of remyelinated nerve fibers in the fornix.
Collapse
Affiliation(s)
- Alan Peters
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
| | | | | |
Collapse
|
49
|
The sexual difference of aging-associated functional degradation in visual cortical cells of rats. Neurosci Lett 2010; 486:179-83. [PMID: 20868727 DOI: 10.1016/j.neulet.2010.09.047] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Revised: 07/21/2010] [Accepted: 09/16/2010] [Indexed: 11/21/2022]
Abstract
Function of visual cortical cells declines during normal aging. Whether there are sex-related differences in this functional degradation is still unknown. In the present study we compared the properties of adaptation, onset latency, and signal-to-noise ratio of visual cortical cells between age-matched sexes in order to investigate any sex related difference. Our results show that visual cortical cell function did not differ between young male and young female rats. However, compared with female rats in the same age, the signal-to-noise ratio, but not adaptation or onset latency, was significantly impaired in mid-aged and aged male rats. These results indicate that the functional degradation of visual cortical cells to some extent is associated with sex and therefore, could contribute for the differential degree of cognitive decline that occurs in males and females during senescence.
Collapse
|
50
|
Bowley MP, Cabral H, Rosene DL, Peters A. Age changes in myelinated nerve fibers of the cingulate bundle and corpus callosum in the rhesus monkey. J Comp Neurol 2010; 518:3046-64. [PMID: 20533359 DOI: 10.1002/cne.22379] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Aging is accompanied by deficits in cognitive function, which may be related to the vulnerability of myelinated nerve fibers to the normal process of aging. Loss of nerve fibers, together with age-related alterations in myelin sheath structure, may result in the inefficient and poorly coordinated conduction of neuronal signals. Until now, the ultrastructural analysis of cerebral white matter fiber tracts associated with frontal lobe areas critical in cognitive processing has been limited. In this study we analyzed the morphology and area number density of myelinated nerve fibers in the cingulate bundle and genu of the corpus callosum in behaviorally assessed young, middle aged, and old rhesus monkeys (Macaca mulatta). In both structures, normal aging results in a 20% decrease in the number of myelinated nerve fibers per unit area, while remaining nerve fibers exhibit an increasing frequency of degenerative changes in their myelin sheaths throughout middle and old age. Concomitantly, myelination continues in older monkeys, suggesting ongoing, albeit inadequate, reparative processes. Despite similar patterns of degeneration in both fiber tracts, only the age-related changes in the cingulate bundle correlate with declining cognitive function, underscoring its role as a critical corticocortical pathway linking the medial prefrontal, cingulate, and parahippocampal cortices in processes of working memory, recognition memory, and other higher cognitive faculties. These results further demonstrate the important role myelinated nerve fiber degeneration plays in the pathogenesis of age-related cognitive decline.
Collapse
Affiliation(s)
- Michael P Bowley
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
| | | | | | | |
Collapse
|