1
|
Rodríguez-Barrera R, Rivas-González M, García-Sánchez J, Mojica-Torres D, Ibarra A. Neurogenesis after Spinal Cord Injury: State of the Art. Cells 2021; 10:cells10061499. [PMID: 34203611 PMCID: PMC8232196 DOI: 10.3390/cells10061499] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 05/24/2021] [Accepted: 06/08/2021] [Indexed: 01/06/2023] Open
Abstract
Neurogenesis in the adult state is the process of new neuron formation. This relatively infrequent phenomenon comprises four stages: cell proliferation, cell migration, differentiation, and the integration of these cells into an existing circuit. Recent reports suggest that neurogenesis can be found in different regions of the Central Nervous System (CNS), including the spinal cord (SC). This process can be observed in physiological settings; however, it is more evident in pathological conditions. After spinal cord injury (SCI), the activation of microglial cells and certain cytokines have shown to exert different modulatory effects depending on the presence of inflammation and on the specific region of the injury site. In these conditions, microglial cells and cytokines are considered to play an important role in the regulation of neurogenesis after SCI. The purpose of this article is to present an overview on neural progenitor cells and neurogenic and non-neurogenic zones as well as the cellular and molecular regulation of neurogenesis. Additionally, we will briefly describe the recent advances in the knowledge of neurogenesis after SCI.
Collapse
|
2
|
Liu S, Chen Z. Employing Endogenous NSCs to Promote Recovery of Spinal Cord Injury. Stem Cells Int 2019; 2019:1958631. [PMID: 31191666 PMCID: PMC6525819 DOI: 10.1155/2019/1958631] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 04/07/2019] [Indexed: 12/15/2022] Open
Abstract
Endogenous neural stem cells (NSCs) exist in the central canal of mammalian spinal cords. Under normal conditions, these NSCs remain quiescent and express FoxJ1. After spinal cord injury (SCI), the endogenous NSCs of a heterogeneous nature are activated and proliferate and migrate towards the lesion site and mainly differentiate into astrocytes to repair the injured tissue. In vitro, spinal cord NSCs are multipotent and can differentiate into neurons, astrocytes, and oligodendrocytes. The altered microenvironments after SCI play key roles on the fate determination of activated NSCs, especially on the neuronal specification potential. Studies show that the activated spinal cord NSCs can generate interneurons when transplanted into the adult hippocampus. In addition, the spinal cord NSCs exhibit low immunogenicity in a transplantation context, thus implicating a promising therapeutic potential on SCI recovery. Here, we summarize the characteristics of spinal cord NSCs, especially their properties after injury. With a better understanding of endogenous NSCs under normal and SCI conditions, we may be able to employ endogenous NSCs for SCI repair in the future.
Collapse
Affiliation(s)
- Sumei Liu
- Cell Therapy Center, Beijing Institute of Geriatrics, Xuanwu Hospital, Capital Medical University, Beijing 100053, China
- Key Laboratory of Neurodegenerative Diseases, Ministry of Education, Beijing 100053, China
| | - Zhiguo Chen
- Cell Therapy Center, Beijing Institute of Geriatrics, Xuanwu Hospital, Capital Medical University, Beijing 100053, China
- Key Laboratory of Neurodegenerative Diseases, Ministry of Education, Beijing 100053, China
- Center of Neural Injury and Repair, Beijing Institute for Brain Disorders, Beijing 100069, China
- Center of Parkinson's Disease, Beijing Institute for Brain Disorders, Beijing 100069, China
| |
Collapse
|
3
|
Yang J, Cheng X, Qi J, Xie B, Zhao X, Zheng K, Zhang Z, Qiu M. EGF Enhances Oligodendrogenesis from Glial Progenitor Cells. Front Mol Neurosci 2017; 10:106. [PMID: 28442994 PMCID: PMC5387051 DOI: 10.3389/fnmol.2017.00106] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 03/28/2017] [Indexed: 12/24/2022] Open
Abstract
Emerging evidence indicates that epidermal growth factor (EGF) signaling plays a positive role in myelin development and repair, but little is known about its biological effects on the early generation and differentiation of oligodendrocyte (OL) lineage cells. In this study, we investigated the role of EGF in early OL development with isolated glial restricted precursor (GRP) cells. It was found that EGF collaborated with Platelet Derived Growth Factor-AA (PDGFaa) to promote the survival and self-renewal of GRP cells, but predisposed GRP cells to develop into O4- early-stage oligodendrocyte precursor cells (OPCs) in the absence of or PDGFaa. In OPCs, EGF synergized with PDGFaa to maintain their O4 negative antigenic phenotype. Upon PDGFaa withdrawal, EGF promoted the terminal differentiation of OPCs by reducing apoptosis and increasing the number of mature OLs. Together, these data revealed that EGF is an important mitogen to enhance oligodendroglial development.
Collapse
Affiliation(s)
- Junlin Yang
- The Institute of Developmental and Regenerative Biology, Zhejiang Key Laboratory of Organ Development and Regeneration, College of Life and Environment Sciences, Hangzhou Normal UniversityHangzhou, China
| | - Xuejun Cheng
- The Institute of Developmental and Regenerative Biology, Zhejiang Key Laboratory of Organ Development and Regeneration, College of Life and Environment Sciences, Hangzhou Normal UniversityHangzhou, China
| | - Jiajun Qi
- The Institute of Developmental and Regenerative Biology, Zhejiang Key Laboratory of Organ Development and Regeneration, College of Life and Environment Sciences, Hangzhou Normal UniversityHangzhou, China
| | - Binghua Xie
- The Institute of Developmental and Regenerative Biology, Zhejiang Key Laboratory of Organ Development and Regeneration, College of Life and Environment Sciences, Hangzhou Normal UniversityHangzhou, China
| | - Xiaofeng Zhao
- The Institute of Developmental and Regenerative Biology, Zhejiang Key Laboratory of Organ Development and Regeneration, College of Life and Environment Sciences, Hangzhou Normal UniversityHangzhou, China
| | - Kang Zheng
- The Institute of Developmental and Regenerative Biology, Zhejiang Key Laboratory of Organ Development and Regeneration, College of Life and Environment Sciences, Hangzhou Normal UniversityHangzhou, China
| | - Zunyi Zhang
- The Institute of Developmental and Regenerative Biology, Zhejiang Key Laboratory of Organ Development and Regeneration, College of Life and Environment Sciences, Hangzhou Normal UniversityHangzhou, China
| | - Mengsheng Qiu
- The Institute of Developmental and Regenerative Biology, Zhejiang Key Laboratory of Organ Development and Regeneration, College of Life and Environment Sciences, Hangzhou Normal UniversityHangzhou, China.,Department of Anatomical Sciences and Neurobiology, University of LouisvilleLouisville, KY, USA
| |
Collapse
|
4
|
Honsa P, Valny M, Kriska J, Matuskova H, Harantova L, Kirdajova D, Valihrach L, Androvic P, Kubista M, Anderova M. Generation of reactive astrocytes from NG2 cells is regulated by sonic hedgehog. Glia 2016; 64:1518-31. [DOI: 10.1002/glia.23019] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 05/10/2016] [Accepted: 05/26/2016] [Indexed: 11/10/2022]
Affiliation(s)
- Pavel Honsa
- Department of Cellular Neurophysiology; Institute of Experimental Medicine, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Martin Valny
- Department of Cellular Neurophysiology; Institute of Experimental Medicine, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Jan Kriska
- Department of Cellular Neurophysiology; Institute of Experimental Medicine, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Hana Matuskova
- Department of Cellular Neurophysiology; Institute of Experimental Medicine, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Lenka Harantova
- Department of Cellular Neurophysiology; Institute of Experimental Medicine, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Denisa Kirdajova
- Department of Cellular Neurophysiology; Institute of Experimental Medicine, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Lukas Valihrach
- Laboratory of Gene Expression; Institute of Biotechnology, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Peter Androvic
- Laboratory of Gene Expression; Institute of Biotechnology, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Mikael Kubista
- Laboratory of Gene Expression; Institute of Biotechnology, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| | - Miroslava Anderova
- Department of Cellular Neurophysiology; Institute of Experimental Medicine, Academy of Sciences of the Czech Republic; Prague 142 20 Czech Republic
| |
Collapse
|
5
|
Abstract
Three theories of regeneration dominate neuroscience today, all purporting to explain why the adult central nervous system (CNS) cannot regenerate. One theory proposes that Nogo, a molecule expressed by myelin, prevents axonal growth. The second theory emphasizes the role of glial scars. The third theory proposes that chondroitin sulfate proteoglycans (CSPGs) prevent axon growth. Blockade of Nogo, CSPG, and their receptors indeed can stop axon growth in vitro and improve functional recovery in animal spinal cord injury (SCI) models. These therapies also increase sprouting of surviving axons and plasticity. However, many investigators have reported regenerating spinal tracts without eliminating Nogo, glial scar, or CSPG. For example, many motor and sensory axons grow spontaneously in contused spinal cords, crossing gliotic tissue and white matter surrounding the injury site. Sensory axons grow long distances in injured dorsal columns after peripheral nerve lesions. Cell transplants and treatments that increase cAMP and neurotrophins stimulate motor and sensory axons to cross glial scars and to grow long distances in white matter. Genetic studies deleting all members of the Nogo family and even the Nogo receptor do not always improve regeneration in mice. A recent study reported that suppressing the phosphatase and tensin homolog (PTEN) gene promotes prolific corticospinal tract regeneration. These findings cannot be explained by the current theories proposing that Nogo and glial scars prevent regeneration. Spinal axons clearly can and will grow through glial scars and Nogo-expressing tissue under some circumstances. The observation that deleting PTEN allows corticospinal tract regeneration indicates that the PTEN/AKT/mTOR pathway regulates axonal growth. Finally, many other factors stimulate spinal axonal growth, including conditioning lesions, cAMP, glycogen synthetase kinase inhibition, and neurotrophins. To explain these disparate regenerative phenomena, I propose that the spinal cord has evolved regenerative mechanisms that are normally suppressed by multiple extrinsic and intrinsic factors but can be activated by injury, mediated by the PTEN/AKT/mTOR, cAMP, and GSK3b pathways, to stimulate neural growth and proliferation.
Collapse
Affiliation(s)
- Wise Young
- W. M. Keck Center for Collaborative Neuroscience, Rutgers, State University of New Jersey, Piscataway, NJ, USA
| |
Collapse
|
6
|
Neural stem cells in the adult spinal cord. Exp Neurol 2014; 260:44-9. [DOI: 10.1016/j.expneurol.2013.01.026] [Citation(s) in RCA: 120] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 01/18/2013] [Accepted: 01/23/2013] [Indexed: 11/20/2022]
|
7
|
Franz S, Ciatipis M, Pfeifer K, Kierdorf B, Sandner B, Bogdahn U, Blesch A, Winner B, Weidner N. Thoracic rat spinal cord contusion injury induces remote spinal gliogenesis but not neurogenesis or gliogenesis in the brain. PLoS One 2014; 9:e102896. [PMID: 25050623 PMCID: PMC4106835 DOI: 10.1371/journal.pone.0102896] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 06/24/2014] [Indexed: 12/16/2022] Open
Abstract
After spinal cord injury, transected axons fail to regenerate, yet significant, spontaneous functional improvement can be observed over time. Distinct central nervous system regions retain the capacity to generate new neurons and glia from an endogenous pool of progenitor cells and to compensate neural cell loss following certain lesions. The aim of the present study was to investigate whether endogenous cell replacement (neurogenesis or gliogenesis) in the brain (subventricular zone, SVZ; corpus callosum, CC; hippocampus, HC; and motor cortex, MC) or cervical spinal cord might represent a structural correlate for spontaneous locomotor recovery after a thoracic spinal cord injury. Adult Fischer 344 rats received severe contusion injuries (200 kDyn) of the mid-thoracic spinal cord using an Infinite Horizon Impactor. Uninjured rats served as controls. From 4 to 14 days post-injury, both groups received injections of bromodeoxyuridine (BrdU) to label dividing cells. Over the course of six weeks post-injury, spontaneous recovery of locomotor function occurred. Survival of newly generated cells was unaltered in the SVZ, HC, CC, and the MC. Neurogenesis, as determined by identification and quantification of doublecortin immunoreactive neuroblasts or BrdU/neuronal nuclear antigen double positive newly generated neurons, was not present in non-neurogenic regions (MC, CC, and cervical spinal cord) and unaltered in neurogenic regions (dentate gyrus and SVZ) of the brain. The lack of neuronal replacement in the brain and spinal cord after spinal cord injury precludes any relevance for spontaneous recovery of locomotor function. Gliogenesis was increased in the cervical spinal cord remote from the injury site, however, is unlikely to contribute to functional improvement.
Collapse
Affiliation(s)
- Steffen Franz
- Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany
| | - Mareva Ciatipis
- Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany
| | - Kathrin Pfeifer
- Department of Neurology, University of Regensburg, Regensburg, Germany
| | - Birthe Kierdorf
- Department of Neurology, University of Regensburg, Regensburg, Germany
| | - Beatrice Sandner
- Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany
| | - Ulrich Bogdahn
- Department of Neurology, University of Regensburg, Regensburg, Germany
| | - Armin Blesch
- Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany
| | - Beate Winner
- IZKF Junior Group III and BMBF Research Group Neuroscience, Interdisciplinary Center for Clinical Research, Nikolaus-Fiebiger Center for Molecular Medicine, Friedrich-Alexander University-Erlangen-Nürnberg, Erlangen, Germany
| | - Norbert Weidner
- Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany
| |
Collapse
|
8
|
Solga AC, Gianino SM, Gutmann DH. NG2-cells are not the cell of origin for murine neurofibromatosis-1 (Nf1) optic glioma. Oncogene 2013; 33:289-99. [PMID: 23318450 DOI: 10.1038/onc.2012.580] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Revised: 10/26/2012] [Accepted: 10/26/2012] [Indexed: 01/19/2023]
Abstract
Low-grade glial neoplasms (astrocytomas) represent one of the most common brain tumors in the pediatric population. These tumors frequently form in the optic pathway (optic pathway gliomas, OPGs), especially in children with the neurofibromatosis type 1 (NF1)-inherited tumor predisposition syndrome. To model these tumors in mice, we have previously developed several Nf1 genetically-engineered mouse strains that form optic gliomas. However, there are three distinct macroglial cell populations in the optic nerve (astrocytes, NG2+ (nerve/glial antigen 2) cells and oligodendrocytes). The presence of NG2+ cells in the optic nerve raises the intriguing possibility that these cells could be the tumor-initiating cells, as has been suggested for adult glioma. In this report, we used a combination of complementary in vitro and novel genetically-engineered mouse strains in vivo to determine whether NG2+ cells could give rise to Nf1 optic glioma. First, we show that Nf1 inactivation results in a cell-autonomous increase in glial fibrillary acidic protein+ (GFAP+), but not in NG2+, cell proliferation in vitro. Second, similar to the GFAP-Cre transgenic strain that drives Nf1 optic gliomagenesis, NG2-expressing cells also give rise to all three macroglial lineages in vivo. Third, in contrast to the GFAP-Cre strain, Nf1 gene inactivation in NG2+ cells is not sufficient for optic gliomagenesis in vivo. Collectively, these data demonstrate that NG2+ cells are not the cell of origin for mouse optic glioma, and support a model in which gliomagenesis requires Nf1 loss in specific neuroglial progenitors during embryogenesis.
Collapse
Affiliation(s)
- A C Solga
- Department of Neurology, Washington University School of Medicine, St Louis, MO, USA
| | - S M Gianino
- Department of Neurology, Washington University School of Medicine, St Louis, MO, USA
| | - D H Gutmann
- Department of Neurology, Washington University School of Medicine, St Louis, MO, USA
| |
Collapse
|
9
|
Endogenous proliferation after spinal cord injury in animal models. Stem Cells Int 2012; 2012:387513. [PMID: 23316243 PMCID: PMC3539424 DOI: 10.1155/2012/387513] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Revised: 10/06/2012] [Accepted: 10/29/2012] [Indexed: 12/12/2022] Open
Abstract
Spinal cord injury (SCI) results in motor and sensory deficits, the severity of which depends on the level and extent of the injury. Animal models for SCI research include transection, contusion, and compression mouse models. In this paper we will discuss the endogenous stem cell response to SCI in animal models. All SCI animal models experience a similar peak of cell proliferation three days after injury; however, each specific type of injury promotes a specific and distinct stem cell response. For example, the transection model results in a strong and localized initial increase of proliferation, while in contusion and compression models, the initial level of proliferation is lower but encompasses the entire rostrocaudal extent of the spinal cord. All injury types result in an increased ependymal proliferation, but only in contusion and compression models is there a significant level of proliferation in the lateral regions of the spinal cord. Finally, the fate of newly generated cells varies from a mainly oligodendrocyte fate in contusion and compression to a mostly astrocyte fate in the transection model. Here we will discuss the potential of endogenous stem/progenitor cell manipulation as a therapeutic tool to treat SCI.
Collapse
|
10
|
Lee HJ, Wu J, Chung J, Wrathall JR. SOX2 expression is upregulated in adult spinal cord after contusion injury in both oligodendrocyte lineage and ependymal cells. J Neurosci Res 2012; 91:196-210. [PMID: 23169458 DOI: 10.1002/jnr.23151] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Revised: 08/13/2012] [Accepted: 09/07/2012] [Indexed: 01/28/2023]
Abstract
The upregulation of genes normally associated with development may occur in the adult after spinal cord injury (SCI). To test this, we performed real-time RT-PCR array analysis of mouse spinal cord mRNAs comparing embryonic day (E)14.5 spinal cord with intact adult and adult cord 1 week after a clinically relevant standardized contusion SCI. We found significantly increased expression of a large number of neural development- and stem cell-associated genes after SCI. These included Sox2 (sex determining region Y-box 2), a transcription factor that regulates self-renewal and potency of embryonic neural stem cells and is one of only a few key factors needed to induce pluripotency. In adult spinal cord of Sox2-EGFP mice, Sox2-EGFP was found mainly in the ependymal cells of the central canal. After SCI, both mRNA and protein levels of Sox2 were significantly increased at and near the injury site. By 1 day, Sox2 was upregulated in NG2(+) oligodendrocyte progenitor cells (OPC) in the spared white matter. By 3 days, Sox2-EGFP ependymal cells had increased proliferation and begun to form multiple layers and clusters of cells in the central lesion zone of the cord. Expression of Sox2 by NG2(+) cells had declined by 1 week, but increased numbers of other Sox2-expressing cells persisted for at least 4 weeks after SCI in both mouse and rat models. Thus, SCI upregulates many genes associated with development and neural stem cells, including the key transcription factor Sox2, which is expressed in a pool of cells that persists for weeks after SCI.
Collapse
Affiliation(s)
- Hyun Joon Lee
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC 20057, USA
| | | | | | | |
Collapse
|
11
|
Ju P, Zhang S, Yeap Y, Feng Z. Induction of neuronal phenotypes from NG2+ glial progenitors by inhibiting epidermal growth factor receptor in mouse spinal cord injury. Glia 2012; 60:1801-14. [DOI: 10.1002/glia.22398] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2011] [Accepted: 07/05/2012] [Indexed: 12/20/2022]
|
12
|
Caillava C, Baron-Van Evercooren A. Differential requirement of cyclin-dependent kinase 2 for oligodendrocyte progenitor cell proliferation and differentiation. Cell Div 2012; 7:14. [PMID: 22583398 PMCID: PMC3441353 DOI: 10.1186/1747-1028-7-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Accepted: 04/18/2012] [Indexed: 12/12/2022] Open
Abstract
Cyclin-dependent kinases (Cdks) and their cyclin regulatory subunits control cell growth and division. Cdk2-cyclin E complexes, phosphorylating the retinoblastoma protein, drive cells through the G1/S transition into the S phase of the cell cycle. Despite its fundamental role, Cdk2 was found to be indispensable only in specific cell types due to molecular redundancies in its function. Converging studies highlight involvement of Cdk2 and associated cell cycle regulatory proteins in oligodendrocyte progenitor cell proliferation and differentiation. Giving the contribution of this immature cell type to brain plasticity and repair in the adult, this review will explore the requirement of Cdk2 for oligodendrogenesis, oligodendrocyte progenitor cells proliferation and differentiation during physiological and pathological conditions.
Collapse
Affiliation(s)
- Céline Caillava
- Université Pierre et Marie Curie-Paris 6, Centre de Recherche de l'Institut du Cerveau et de la Moelle Epinière, UMR-S975, Paris, France.
| | | |
Collapse
|
13
|
Stem Cells and Spinal Cord Injury Repair. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 760:53-73. [DOI: 10.1007/978-1-4614-4090-1_4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
|
14
|
Whittaker MT, Zai LJ, Lee HJ, Pajoohesh-Ganji A, Wu J, Sharp A, Wyse R, Wrathall JR. GGF2 (Nrg1-β3) treatment enhances NG2+ cell response and improves functional recovery after spinal cord injury. Glia 2011; 60:281-94. [PMID: 22042562 DOI: 10.1002/glia.21262] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 10/06/2011] [Indexed: 12/13/2022]
Abstract
The adult spinal cord contains a pool of endogenous glial precursor cells, which spontaneously respond to spinal cord injury (SCI) with increased proliferation. These include oligodendrocyte precursor cells that express the NG2 proteoglycan and can differentiate into mature oligodendrocytes. Thus, a potential approach for SCI treatment is to enhance the proliferation and differentiation of these cells to yield more functional mature glia and improve remyelination of surviving axons. We previously reported that soluble glial growth factor 2 (GGF2)- and basic fibroblast growth factor 2 (FGF2)-stimulated growth of NG2(+) cells purified from injured spinal cord in primary culture. This study examines the effects of systemic administration of GGF2 and/or FGF2 after standardized contusive SCI in vivo in both rat and mouse models. In Sprague-Dawley rats, 1 week of GGF2 administration, beginning 24 h after injury, enhanced NG2(+) cell proliferation, oligodendrogenesis, chronic white matter at the injury epicenter, and recovery of hind limb function. In 2',3'-cyclic-nucleotide 3'-phosphodiesterase-enhanced green fluorescent protein mice, GGF2 treatment resulted in increased oligodendrogenesis and improved functional recovery, as well as elevated expression of the stem cell transcription factor Sox2 by oligodendrocyte lineage cells. Although oligodendrocyte number was increased chronically after SCI in GGF2-treated mice, no evidence of increased white matter was detected. However, GGF2 treatment significantly increased levels of P0 protein-containing peripheral myelin, produced by Schwann cells that infiltrate the injured spinal cord. Our results suggest that GGF2 may have therapeutic potential for SCI by enhancing endogenous recovery processes in a clinically relevant time frame.
Collapse
Affiliation(s)
- Matthew T Whittaker
- Department of Neuroscience, Georgetown University, Washington, District of Columbia 20057, USA
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Abstract
Oligodendrocytes (OLs) are particularly susceptible to the toxicity of the acute lesion environment after spinal cord injury (SCI). They undergo both necrosis and apoptosis acutely, with apoptosis continuing at chronic time points. Loss of OLs causes demyelination and impairs axon function and survival. In parallel, a rapid and protracted OL progenitor cell proliferative response occurs, especially at the lesion borders. Proliferating and migrating OL progenitor cells differentiate into myelinating OLs, which remyelinate demyelinated axons starting at 2 weeks post-injury. The progression of OL lineage cells into mature OLs in the adult after injury recapitulates development to some degree, owing to the plethora of factors within the injury milieu. Although robust, this endogenous oligogenic response is insufficient against OL loss and demyelination. First, in this review we analyze the major spatial-temporal mechanisms of OL loss, replacement, and myelination, with the purpose of highlighting potential areas of intervention after SCI. We then discuss studies on OL protection and replacement. Growth factors have been used both to boost the endogenous progenitor response, and in conjunction with progenitor transplantation to facilitate survival and OL fate. Considerable progress has been made with embryonic stem cell-derived cells and adult neural progenitor cells. For therapies targeting oligogenesis to be successful, endogenous responses and the effects of the acute and chronic lesion environment on OL lineage cells must be understood in detail, and in relation, the optimal therapeutic window for such strategies must also be determined.
Collapse
Affiliation(s)
- Akshata Almad
- Neuroscience Graduate Studies Program, Ohio State University, Columbus, Ohio 43210 USA
- Center for Brain and Spinal Cord Repair, Ohio State University, Columbus, Ohio 43210 USA
| | - F. Rezan Sahinkaya
- Neuroscience Graduate Studies Program, Ohio State University, Columbus, Ohio 43210 USA
- Center for Brain and Spinal Cord Repair, Ohio State University, Columbus, Ohio 43210 USA
| | - Dana M. McTigue
- Center for Brain and Spinal Cord Repair, Ohio State University, Columbus, Ohio 43210 USA
- Department of Neuroscience, Ohio State University, 788 Biomedical Research Tower, 460 W. 12th Ave, Columbus, Ohio 43210 USA
| |
Collapse
|
16
|
Wu J, Leung PY, Sharp A, Lee HJ, Wrathall JR. Increased expression of the close homolog of the adhesion molecule L1 in different cell types over time after rat spinal cord contusion. J Neurosci Res 2011; 89:628-38. [PMID: 21337374 DOI: 10.1002/jnr.22598] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 12/08/2010] [Accepted: 12/18/2010] [Indexed: 11/10/2022]
Abstract
The close homolog of the adhesion molecule L1 (CHL1) is important during CNS development, but a study with CHL1 knockout mice showed greater functional recovery after spinal cord injury (SCI) in its absence. We investigated CHL1 expression from 1 to 28 days after clinically relevant contusive SCI in Sprague-Dawley rats. Western blot analysis showed that CHL1 expression was significantly up-regulated at day 1 and further increased over 4 weeks after SCI. Immunohistochemistry of tissue sections showed that CHL1 in the intact spinal cord was expressed at low levels. By 1 day and through 4 weeks after SCI, CHL1 became highly expressed in NG2(+) cells. Hypertrophic GFAP(+) astrocytes also expressed CHL1 by 1 week after injury. The increase in CHL1 protein paralleled that of NG2 in the first week and GFAP between 1 and 4 weeks after injury. At 4 weeks, NG2(+) /CHL1(+) cells and GFAP(+) /CHL1(+) astrocytes were concentrated at the boundary between residual spinal cord tissue and the central lesion. NF200(+) spinal cord axons approached but did not penetrate this boundary. In contrast, CHL1(+) cells in the central lesion at 1 week and later colabeled with p75 and NG2 and were chronically associated with many NF200(+) axons, presumably axons that had sprouted in association with CHL1(+) Schwann cells infiltrating the cord after contusion. Thus, our study demonstrates up-regulation of CHL1 in multiple cell types and locations in a rat model of contusion injury and suggests that this molecule may be involved both in inhibition of axonal regeneration and in recovery processes after SCI.
Collapse
Affiliation(s)
- Junfang Wu
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC, USA.
| | | | | | | | | |
Collapse
|
17
|
Yang Y, Lewis R, Miller RH. Interactions between oligodendrocyte precursors control the onset of CNS myelination. Dev Biol 2010; 350:127-38. [PMID: 21144846 DOI: 10.1016/j.ydbio.2010.11.028] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 10/29/2010] [Accepted: 11/24/2010] [Indexed: 01/13/2023]
Abstract
The formation of CNS myelin is dependent on the differentiation of oligodendrocyte precursor cells (OPCs) and oligodendrocyte maturation. How the initiation of myelination is regulated is unclear, but it is likely to depend on the development of competence by oligodendrocytes and receptivity by target axons. Here we identify an additional level of control of oligodendrocyte maturation mediated by interactions between the different cellular components of the oligodendrocyte lineage. During development oligodendrocyte precursors mature through a series of stages defined by labeling with monoclonal antibodies A2B5 and O4. Newly differentiated oligodendrocytes begin to express galactocerebroside recognized by O1 antibodies and subsequently mature to myelin basic protein (MBP)-positive cells prior to formation of compact myelin. Using an in vitro brain slice culture system that supports robust myelination, the consequences of ablating cells at different stages of the oligodendrocyte lineage on myelination have been assayed. Elimination of all OPC lineage cells through A2B5+, O4+, and O1+ complement-mediated cell lysis resulted in a delay in development of MBP cells and myelination. Selective elimination of early OPCs (A2B5+) also unexpectedly resulted in delayed MBP expression compared to controls suggesting that early OPCs contribute to the timing of myelination onset. By contrast, elimination of differentiated (O1+) immature oligodendrocytes permanently inhibited the appearance of MBP+ cells suggesting that oligodendrocytes are critical to facilitate the maturation of OPCs. These data illuminate that the presence of intra-lineage feed-forward and feedback cues are important for timely myelination by oligodendrocytes.
Collapse
Affiliation(s)
- Yan Yang
- Department of Neurology, Case Western Reserve University, School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106, USA
| | | | | |
Collapse
|
18
|
Almad A, McTigue DM. Chronic expression of PPAR-delta by oligodendrocyte lineage cells in the injured rat spinal cord. J Comp Neurol 2010; 518:785-99. [PMID: 20058304 DOI: 10.1002/cne.22242] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The transcription factor peroxisome proliferator-activated receptor (PPAR)-delta promotes oligodendrocyte differentiation and myelin formation in vitro and is prevalent throughout the brain and spinal cord. Its expression after injury, however, has not been examined. Thus, we used a spinal contusion model to examine the spatiotemporal expression of PPAR-delta in naïve and injured spinal cords from adult rats. As previously reported, PPAR-delta was expressed by neurons and oligodendrocytes in uninjured spinal cords; PPAR-delta was also detected in NG2 cells (potential oligodendrocyte progenitors) within the white matter and gray matter. After spinal cord injury (SCI), PPAR-delta mRNA and protein were present early and increased over time. Overall PPAR-delta+ cell numbers declined at 1 day post injury (dpi), likely reflecting neuron loss, and then rose through 14 dpi. A large proportion of NG2 cells expressed PPAR-delta after SCI, especially along lesion borders. PPAR-delta+ NG2 cell numbers were significantly higher than naive by 7 dpi and remained elevated through at least 28 dpi. PPAR-delta+ oligodendrocyte numbers declined at 1 dpi and then increased over time such that >20% of oligodendrocytes expressed PPAR-delta after SCI compared with approximately 10% in uninjured tissue. The most prominent increase in PPAR-delta+ oligodendrocytes was along lesion borders where at least a portion of newly generated oligodendrocytes (bromodeoxyuridine+) were PPAR-delta+. Consistent with its role in cellular differentiation, the early rise in PPAR-delta+ NG2 cells followed by an increase in new PPAR-delta+ oligodendrocytes suggests that this transcription factor may be involved in the robust oligodendrogenesis detected previously along SCI lesion borders.
Collapse
Affiliation(s)
- Akshata Almad
- The Neuroscience Graduate Studies Program, The Ohio State University, Columbus, Ohio 43210, USA
| | | |
Collapse
|
19
|
Wu J, Yoo S, Wilcock D, Lytle JM, Leung PY, Colton CA, Wrathall JR. Interaction of NG2(+) glial progenitors and microglia/macrophages from the injured spinal cord. Glia 2010; 58:410-22. [PMID: 19780197 DOI: 10.1002/glia.20932] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Spinal cord contusion produces a central lesion surrounded by a peripheral rim of residual white matter. Despite stimulation of NG2(+) progenitor cell proliferation, the lesion remains devoid of normal glia chronically after spinal cord injury (SCI). To investigate potential cell-cell interactions of the predominant cells in the lesion at 3 days after injury, we used magnetic activated cell sorting to purify NG2(+) progenitors and OX42(+) microglia/macrophages from contused rat spinal cord. Purified NG2(+) cells from the injured cord grew into spherical masses when cultured in defined medium with FGF2 plus GGF2. The purified OX42(+) cells did not form spheroids and significantly reduced sphere growth by NG2(+) cells in co-cultures. Conditioned medium from these OX42(+) cells, unlike that from normal peritoneal macrophages or astrocytes also inhibited growth of NG2(+) cells, suggesting inhibition by secreted factors. Expression analysis of freshly purified OX42(+) cells for a panel of six genes for secreted factors showed expression of several that could contribute to inhibition of NG2(+) cells. Further, the pattern of expression of four of these, TNFalpha, TSP1, TIMP1, MMP9, in sequential coronal tissue segments from a 2 cm length of cord centered on the injury epicenter correlated with the expression of Iba1, a marker gene for OX42(+) cells, strongly suggesting a potential regional influence by activated microglia/macrophages on NG2(+) cells in vivo after SCI. Thus, the nonreplacement of lost glial cells in the central lesion zone may involve, at least in part, inhibitory factors produced by microglia/macrophages that are concentrated within the lesion.
Collapse
Affiliation(s)
- Junfang Wu
- Department of Neuroscience, Georgetown University Medical Center, Washington, District of Columbia, USA
| | | | | | | | | | | | | |
Collapse
|
20
|
Johnson PJ, Parker SR, Sakiyama-Elbert SE. Fibrin-based tissue engineering scaffolds enhance neural fiber sprouting and delay the accumulation of reactive astrocytes at the lesion in a subacute model of spinal cord injury. J Biomed Mater Res A 2010; 92:152-63. [PMID: 19165795 DOI: 10.1002/jbm.a.32343] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The purpose of this study was to evaluate the effects of fibrin scaffolds on subacute rat spinal cord injury (SCI). Long-Evans rats were anesthetized and underwent a dorsal hemisection injury; two weeks later, the injury site was re-exposed, scar tissue was removed, and a fibrin scaffold was implanted into the wound site. An effective method for fibrin scaffold implantation following subacute SCI was investigated based on the presence of fibrin within the lesion site and morphological analysis 1 week after implantation. Prepolymerized fibrin scaffolds were found to be present within the lesion site 1 week after treatment and were used for the remainder of the study. Fibrin scaffolds were then implanted for 2 and 4 weeks, after which spinal cords were harvested and evaluated using markers for neurons, astrocytes, and chondroitin sulfate proteoglycans. Compared with untreated control, the fibrin-treated group had significantly higher levels of neural fiber staining in the lesion site at 2 and 4 weeks after treatment, and the accumulation of glial fibrillary acidic protein (GFAP) positive reactive astrocytes surrounding the lesion was delayed. These results show that fibrin is conducive to regeneration and cellular migration and illustrate the advantage of using fibrin as a scaffold for drug delivery and cell-based therapies for SCI.
Collapse
Affiliation(s)
- Philip J Johnson
- Department of Biomedical Engineering, Washington University, St Louis, MO 63130, USA
| | | | | |
Collapse
|
21
|
Adult NG2+ cells are permissive to neurite outgrowth and stabilize sensory axons during macrophage-induced axonal dieback after spinal cord injury. J Neurosci 2010; 30:255-65. [PMID: 20053907 DOI: 10.1523/jneurosci.3705-09.2010] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We previously demonstrated that activated ED1+ macrophages induce extensive axonal dieback of dystrophic sensory axons in vivo and in vitro. Interestingly, after spinal cord injury, the regenerating front of axons is typically found in areas rich in ED1+ cells, but devoid of reactive astrocyte processes. These observations suggested that another cell type must be present in these areas to counteract deleterious effects of macrophages. Cells expressing the purportedly inhibitory chondroitin sulfate proteoglycan NG2 proliferate in the lesion and intermingle with macrophages, but their influence on regeneration is highly controversial. Our in vivo analysis of dorsal column crush lesions confirms the close association between NG2+ cells and injured axons. We hypothesized that NG2+ cells were growth promoting and thereby served to increase axonal stability following spinal cord injury. We observed that the interactions between dystrophic adult sensory neurons and primary NG2+ cells derived from the adult spinal cord can indeed stabilize the dystrophic growth cone during macrophage attack. NG2+ cells expressed high levels of laminin and fibronectin, which promote neurite outgrowth on the surface of these cells. Our data also demonstrate that NG2+ cells, but not astrocytes, use matrix metalloproteases to extend across a region of inhibitory proteoglycan, and provide a permissive bridge for adult sensory axons. These data support the hypothesis that NG2+ cells are not inhibitory to regenerating sensory axons and, in fact, they may provide a favorable substrate that can stabilize the regenerating front of dystrophic axons in the inhibitory environment of the glial scar.
Collapse
|
22
|
Lytle JM, Chittajallu R, Wrathall JR, Gallo V. NG2 cell response in the CNP-EGFP mouse after contusive spinal cord injury. Glia 2009; 57:270-85. [PMID: 18756526 DOI: 10.1002/glia.20755] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
NG2(+) cells in the adult CNS are a heterogeneous population. The extent to which the subpopulation of NG2(+) cells that function as oligodendrocyte progenitor cells (OPCs) respond to spinal cord injury (SCI) and recapitulate their normal developmental progression remains unclear. We used the CNP-EGFP mouse, in which oligodendrocyte lineage cells express EGFP, to study NG2(+) cells in the normal and injured spinal cord. In white matter of uninjured mice, bipolar EGFP(+)NG2(+) cells and multipolar EGFP(neg)NG2(+) cells were identified. After SCI, EGFP(+)NG2(+) cell proliferation in residual white matter peaked at 3 days post injury (DPI) rostral to the epicenter, while EGFP(neg)NG2(+) cell proliferation peaked at 7 DPI at the epicenter. The expression of transcription factors, Olig2, Sox10, and Sox17, and the basic electrophysiological membrane parameters and potassium current phenotype of the EGFP(+)NG2(+) population after injury were consistent with those of proliferative OPCs during development. EGFP(neg)NG2(+) cells did not express transcription factors involved in oligodendrogenesis. EGFP(+)CC1(+) oligodendrocytes at 6 weeks included cells that incorporated BrdU during the peak of EGFP(+)NG2(+) cell proliferation. EGFP(neg)CC1(+) oligodendrocytes were never observed. Treatment with glial growth factor 2 and fibroblast growth factor 2 enhanced oligodendrogenesis and increased the number of EGFP(neg)NG2(+) cells. Therefore, based on EGFP and transcription factor expression, spatiotemporal proliferation patterns, and response to growth factors, two populations of NG2(+) cells can be identified that react to SCI. The EGFP(+)NG2(+) cells undergo cellular and physiological changes in response to SCI that are similar to those that occur in early postnatal NG2(+) cells during developmental oligodendrogenesis.
Collapse
Affiliation(s)
- Judith M Lytle
- Department of Neuroscience, Georgetown University, Washington, District of Columbia, USA
| | | | | | | |
Collapse
|
23
|
Spinal cord injury reveals multilineage differentiation of ependymal cells. PLoS Biol 2008; 6:e182. [PMID: 18651793 PMCID: PMC2475541 DOI: 10.1371/journal.pbio.0060182] [Citation(s) in RCA: 465] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2007] [Accepted: 06/16/2008] [Indexed: 12/21/2022] Open
Abstract
Spinal cord injury often results in permanent functional impairment. Neural stem cells present in the adult spinal cord can be expanded in vitro and improve recovery when transplanted to the injured spinal cord, demonstrating the presence of cells that can promote regeneration but that normally fail to do so efficiently. Using genetic fate mapping, we show that close to all in vitro neural stem cell potential in the adult spinal cord resides within the population of ependymal cells lining the central canal. These cells are recruited by spinal cord injury and produce not only scar-forming glial cells, but also, to a lesser degree, oligodendrocytes. Modulating the fate of ependymal progeny after spinal cord injury may offer an alternative to cell transplantation for cell replacement therapies in spinal cord injury.
Collapse
|
24
|
Tripathi RB, McTigue DM. Chronically increased ciliary neurotrophic factor and fibroblast growth factor-2 expression after spinal contusion in rats. J Comp Neurol 2008; 510:129-44. [PMID: 18615534 PMCID: PMC5518483 DOI: 10.1002/cne.21787] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Demyelination and oligodendrocyte loss following spinal cord injury (SCI) are well documented. Recently, we showed oligodendrocyte progenitor cell (OPC) accumulation and robust oligodendrocyte genesis occurring along SCI lesion borders. We have since begun investigating potential mechanisms for this endogenous repair response. Here, we examined ciliary neurotrophic factor (CNTF) and fibroblast growth factor-2 (FGF-2) expression, because both factors alter progenitor proliferation and differentiation and are increased in several CNS disorders. We hypothesized that CNTF and FGF-2 would increase after SCI, especially in regions of enhanced oligogenesis. First, CNTF protein was quantified using Western blots, which revealed that CNTF protein continually rose through 28 days post injury (dpi). Next, by using immunohistochemistry, we examined the spatiotemporal expression of CNTF in cross-sections spanning the injury site. CNTF immunoreactivity was observed on astrocytes and oligodendrocytes in naïve and contused spinal cords. Significantly increased CNTF was detected in spared white and gray matter between 5 and 28 dpi compared with uninjured controls. By 28 dpi, CNTF expression was significantly higher along lesion borders compared with outlying spared tissue; a similar distribution of phosphorylated STAT3, a transcription factor up-regulated by CNTF and to a lesser extent FGF-2, was also detected. Because CNTF can potentiate FGF-2 expression, we examined the distribution of FGF-2+ cells. Significantly more FGF-2+ cells were noted along lesion borders at 7 and 28 dpi. Thus, both CNTF and FGF-2 are present in regions of elevated OPC proliferation and oligodendrocyte generation after SCI and therefore may play a role in injury-induced gliogenesis.
Collapse
Affiliation(s)
- Richa B. Tripathi
- Neuroscience Graduate Studies Program and Department of Neuroscience, Center for Brain and Spinal Cord Repair, College of Medicine, The Ohio State University, Columbus, Ohio 43210
| | - Dana M. McTigue
- Neuroscience Graduate Studies Program and Department of Neuroscience, Center for Brain and Spinal Cord Repair, College of Medicine, The Ohio State University, Columbus, Ohio 43210
| |
Collapse
|
25
|
Plastic responses to spinal cord injury. Behav Brain Res 2008; 192:114-23. [DOI: 10.1016/j.bbr.2008.02.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2007] [Revised: 02/12/2008] [Accepted: 02/13/2008] [Indexed: 12/26/2022]
|
26
|
Abstract
Spinal cord injury typically results in permanent disability. Many studies have indicated that transplantation of several different types of stem cells promotes functional recovery in animal models of spinal cord injury. A conceptually different approach to utilize stem cells for regenerative therapies may be recruitment of endogenous neural stem cells resident in the adult spinal cord. We discuss the possibilities, risks, and mechanisms for stem cells in spinal cord repair.
Collapse
Affiliation(s)
- Fanie Barnabé-Heider
- Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institute, SE-171 77 Stockholm, Sweden
| | | |
Collapse
|
27
|
McTigue DM, Tripathi RB. The life, death, and replacement of oligodendrocytes in the adult CNS. J Neurochem 2008; 107:1-19. [PMID: 18643793 DOI: 10.1111/j.1471-4159.2008.05570.x] [Citation(s) in RCA: 329] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Oligodendrocytes (OLs) are mature glial cells that myelinate axons in the brain and spinal cord. As such, they are integral to functional and efficient neuronal signaling. The embryonic lineage and postnatal development of OLs have been well-studied and many features of the process have been described, including the origin, migration, proliferation, and differentiation of precursor cells. Less clear is the extent to which OLs and damaged/dysfunctional myelin are replaced following injury to the adult CNS. OLs and their precursors are very vulnerable to conditions common to CNS injury and disease sites, such as inflammation, oxidative stress, and elevated glutamate levels leading to excitotoxicity. Thus, these cells become dysfunctional or die in multiple pathologies, including Alzheimer's disease, spinal cord injury, Parkinson's disease, ischemia, and hypoxia. However, studies of certain conditions to date have detected spontaneous OL replacement. This review will summarize current information on adult OL progenitors, mechanisms that contribute to OL death, the consequences of their loss and the pathological conditions in which spontaneous oligodendrogenesis from endogenous precursors has been observed in the adult CNS.
Collapse
Affiliation(s)
- Dana M McTigue
- Department of Neuroscience and Center for Brain and Spinal Cord Repair, The Ohio State University, Columbus, Ohio, USA.
| | | |
Collapse
|