1
|
Du W, Deng Y, Jiang R, Tong L, Li R, Jiang X. Clemastine Enhances Myelination, Delays Axonal Loss and Promotes Functional Recovery in Spinal Cord Injury. Neurochem Res 2021; 47:503-515. [PMID: 34661796 PMCID: PMC8827101 DOI: 10.1007/s11064-021-03465-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 09/04/2021] [Accepted: 10/08/2021] [Indexed: 11/24/2022]
Abstract
Recent evidence has shown that demyelination occurs along with axonal degeneration in spinal cord injury (SCI) during the secondary injury phase. Oligodendrocyte precursor cells (OPC) are present in the lesions but fail to differentiate into mature oligodendrocytes and form new myelin. Given the limited recovery of neuronal functions after SCI in adults without effective treatment available so far, it remains unknown whether enhancing OPC differentiation and myelination could benefit the recovery of SCI. To show the significance of myelin regeneration after SCI, the injury was treated with clemastine in the rat model. Clemastine is an FDA-approved drug that is potent in promoting oligodendrocyte differentiation and myelination in vivo, for four weeks following SCI. Motor function was assessed using sloping boards and grid walking tests and scored according to the Basso, Beattie, and Bresnahan protocol. The myelin integrity and protein expression were evaluated using transmission electron microscopy and immunofluorescence, respectively. The results indicated that clemastine treatment preserves myelin integrity, decreases loss of axons and improves functional recovery in the rat SCI model. The presented data suggest that myelination-enhancing strategies may serve as a potential therapeutic approach for the functional recovery in SCI.
Collapse
Affiliation(s)
- Weihong Du
- Department of Biochemistry and Molecular Biology, Molecular Medicine and Cancer Research Center, School of Basic Medicine, Chongqing Medical University, Chongqing, 400016, China
| | - Yongbing Deng
- Department of Chongqing Emergency Medical Center, Chongqing University Center Hospital, School of Medicine, Chongqing University, Chongqing, 400014, China
| | - Rong Jiang
- Department of Biochemistry and Molecular Biology, Molecular Medicine and Cancer Research Center, School of Basic Medicine, Chongqing Medical University, Chongqing, 400016, China
| | - Luyao Tong
- Department of Biochemistry and Molecular Biology, Molecular Medicine and Cancer Research Center, School of Basic Medicine, Chongqing Medical University, Chongqing, 400016, China
| | - Ruixue Li
- Department of Histology and Embryology, Chongqing Key Laboratory of Neurobiology, Third Military Medical University, Chongqing, 400038, China
| | - Xue Jiang
- Department of Biochemistry and Molecular Biology, Molecular Medicine and Cancer Research Center, School of Basic Medicine, Chongqing Medical University, Chongqing, 400016, China.
| |
Collapse
|
2
|
Pestana F, Edwards-Faret G, Belgard TG, Martirosyan A, Holt MG. No Longer Underappreciated: The Emerging Concept of Astrocyte Heterogeneity in Neuroscience. Brain Sci 2020; 10:brainsci10030168. [PMID: 32183137 PMCID: PMC7139801 DOI: 10.3390/brainsci10030168] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 03/02/2020] [Accepted: 03/05/2020] [Indexed: 12/18/2022] Open
Abstract
Astrocytes are ubiquitous in the central nervous system (CNS). These cells possess thousands of individual processes, which extend out into the neuropil, interacting with neurons, other glia and blood vessels. Paralleling the wide diversity of their interactions, astrocytes have been reported to play key roles in supporting CNS structure, metabolism, blood-brain-barrier formation and control of vascular blood flow, axon guidance, synapse formation and modulation of synaptic transmission. Traditionally, astrocytes have been studied as a homogenous group of cells. However, recent studies have uncovered a surprising degree of heterogeneity in their development and function, in both the healthy and diseased brain. A better understanding of astrocyte heterogeneity is urgently needed to understand normal brain function, as well as the role of astrocytes in response to injury and disease.
Collapse
Affiliation(s)
- Francisco Pestana
- Laboratory of Glia Biology, VIB-KU Leuven Center for Brain and Disease Research, 3000 Leuven, Belgium;
| | - Gabriela Edwards-Faret
- Laboratory of Neuronal Wiring, VIB-KU Leuven Center for Brain and Disease Research, 3000 Leuven, Belgium;
- Life & Medical Sciences (LIMES) Institute, Faculty of Mathematics and Natural Sciences, University of Bonn, 53115 Bonn, Germany
| | | | - Araks Martirosyan
- Laboratory of Glia Biology, VIB-KU Leuven Center for Brain and Disease Research, 3000 Leuven, Belgium;
- Correspondence: (A.M.); (M.G.H.); Tel.: +32-16-37-31-27 (M.G.H.)
| | - Matthew G. Holt
- Laboratory of Glia Biology, VIB-KU Leuven Center for Brain and Disease Research, 3000 Leuven, Belgium;
- Leuven Brain Institute, KU Leuven, 3000 Leuven, Belgium
- Correspondence: (A.M.); (M.G.H.); Tel.: +32-16-37-31-27 (M.G.H.)
| |
Collapse
|
3
|
Huang L, Wang Y, Zhu M, Wan X, Zhang H, Lei T, Blesch A, Liu S. Anisotropic Alginate Hydrogels Promote Axonal Growth across Chronic Spinal Cord Transections after Scar Removal. ACS Biomater Sci Eng 2020; 6:2274-2286. [PMID: 33455324 DOI: 10.1021/acsbiomaterials.9b01802] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
We have previously reported that cell-seeded alginate hydrogels (AHs) with anisotropic capillaries can restore the continuity of the spinal cord and support axonal regeneration in a rat model of acute partial spinal cord transection. Whether similar effects can be found after transplantation into sites of complete chronic spinal cord transections without additional growth-promoting stimuli has not been investigated. We therefore implanted AHs into the cavity of a chronic thoracic transection following scar resection (SR) 4 weeks postinjury and examined electrophysiological and functional recovery as well as regeneration of descending and ascending projections within and beyond the AH scaffold up to 3 months after engraftment. Our results indicate that both electrophysiological conductivity and locomotor function are significantly improved after AH engraftment. SR transiently impairs locomotor function immediately after surgery but does not affect long-term outcomes. Histological analysis shows numerous host cells migrating into the scaffold channels and a reduction of fibroglial scaring around the lesion by AH grafts. In contrast to corticospinal axons, raphaespinal and propriospinal descending axons and ascending sensory axons regenerate throughout the scaffolds and extend into the distal host parenchyma. These results further support the pro-regenerative properties of AHs and their therapeutic potential for chronic SCI in combination with other strategies to improve functional outcomes after spinal cord injury.
Collapse
Affiliation(s)
- Lulu Huang
- Department of Oncology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Jiefang Avenue 1095, Wuhan, Hubei 430030, P.R. China
| | - Yu Wang
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Jiefang Avenue 1095, Wuhan, Hubei 430030, P.R. China
| | - Mingxin Zhu
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Jiefang Avenue 1095, Wuhan, Hubei 430030, P.R. China
| | - Xueyan Wan
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Jiefang Avenue 1095, Wuhan, Hubei 430030, P.R. China
| | - Huaqiu Zhang
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Jiefang Avenue 1095, Wuhan, Hubei 430030, P.R. China
| | - Ting Lei
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Jiefang Avenue 1095, Wuhan, Hubei 430030, P.R. China
| | - Armin Blesch
- Department of Neurosciences, Center for Neural Repair, University of California, San Diego, Biomedical Research Facility 2, Room 2131, 9500 Gilman Drive, La Jolla, California 92093-0626, United States
| | - Shengwen Liu
- Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Jiefang Avenue 1095, Wuhan, Hubei 430030, P.R. China
| |
Collapse
|
4
|
Hassannejad Z, Yousefifard M, Azizi Y, Zadegan SA, Sajadi K, Sharif-Alhoseini M, Shakouri-Motlagh A, Mokhatab M, Rezvan M, Shokraneh F, Hosseini M, Vaccaro AR, Harrop JS, Rahimi-Movaghar V. Axonal degeneration and demyelination following traumatic spinal cord injury: A systematic review and meta-analysis. J Chem Neuroanat 2019; 97:9-22. [PMID: 30726717 DOI: 10.1016/j.jchemneu.2019.01.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Revised: 12/22/2018] [Accepted: 01/22/2019] [Indexed: 12/17/2022]
Abstract
The pathophysiology of spinal cord injury (SCI) related processes of axonal degeneration and demyelination are poorly understood. The present systematic review and meta-analysis were performed such to establish quantitative results of animal studies regarding the role of injury severity, SCI models and level of injury on the pathophysiology of axon and myelin sheath degeneration. 39 related articles were included in the analysis. The compiled data showed that the total number of axons, number of myelinated axons, myelin sheath thickness, axonal conduction velocity, and internode length steadily decreased as time elapsed from the injury (Pfor trend<0.0001). The rate of axonal retrograde degeneration was affected by SCI model and severity of the injury. Axonal degeneration was higher in injuries of the thoracic region. The SCI model and the site of the injury also affected axonal retrograde degeneration. The number of myelinated axons in the caudal region of the injury was significantly higher than the lesion site and the rostral region. The findings of the present meta-analysis show that the pathophysiology of axons and myelin sheath differ in various phases of SCI and are affected by multiple factors related to the injury.
Collapse
Affiliation(s)
- Zahra Hassannejad
- Pediatric Urology and Regenerative Medicine Research Center, Children's Hospital Medical Center, Tehran University of Medical Sciences, Tehran, Iran; Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Mahmoud Yousefifard
- Physiology Research Center, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran
| | - Yaser Azizi
- Physiology Research Center, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran
| | - Shayan Abdollah Zadegan
- Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Kiavash Sajadi
- Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Mahdi Sharif-Alhoseini
- Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Aida Shakouri-Motlagh
- Department of Chemical and Biomolecular Engineering, University of Melbourne, Victoria 3010, Australia
| | - Mona Mokhatab
- Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Motahareh Rezvan
- Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Farhad Shokraneh
- Cochrane Schizophrenia Group, Institute of Mental Health, University of Nottingham, Nottingham, UK
| | - Mostafa Hosseini
- Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Alexander R Vaccaro
- Department of Orthopedics and Neurosurgery, Rothman Institute, Thomas Jefferson University Philadelphia, USA
| | - James S Harrop
- Department of Neurosurgery, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Vafa Rahimi-Movaghar
- Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran; Department of Neurosurgery, Thomas Jefferson University, Philadelphia, Pennsylvania, USA; Brain and Spinal Injuries Research Center (BASIR), Neuroscience Institute, Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran.
| |
Collapse
|
5
|
Oligodendrogliogenesis and Axon Remyelination after Traumatic Spinal Cord Injuries in Animal Studies: A Systematic Review. Neuroscience 2019; 402:37-50. [PMID: 30685542 DOI: 10.1016/j.neuroscience.2019.01.019] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 01/12/2019] [Accepted: 01/14/2019] [Indexed: 12/20/2022]
Abstract
Extensive oligodendrocyte death after acute traumatic spinal cord injuries (TSCI) leads to axon demyelination and subsequently may leave axons vulnerable to degeneration. Despite the present evidence showing spontaneous remyelination after TSCI the cellular origin of new myelin and the time course of the axon ensheathment/remyelination remained controversial issue. In this systematic review the trend of oligodendrocyte death after injury as well as the extent and the cellular origin of oligodendrogliogenesis were comprehensively evaluated. The study design was based on Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA)-guided systematic review. PubMed and EMBASE were searched with no temporal or linguistic restrictions. Also, hand-search was performed in the bibliographies of relevant articles. Non-interventional animal studies discussing different types of myelinating cells including oligodendrocytes, Schwann cells and oligodendrocyte progenitor cells (OPCs) were evaluated. The extent of oligodendrocyte death, oligodendrocyte differentiation and remyelination were the pathophysiological outcome measures. We found 12,359 studies, 34 of which met the inclusion criteria. The cumulative evidence shows extensive oligodendrocytes cell death during the first week post-injury (pi). OPCs and peripheral invading Schwann cells are the dominant cells contributing in myelin formation. The maximum OPC proliferation was observed at around 2 weeks pi and oligodendrogliogenesis continues at later stages until the number of oligodendrocytes return to normal tissue by one month pi. Taken together, the evidence in animals reveals the potential role for endogenous myelinating cells in the axon ensheathment/remyelination after TSCI and this can be the target of pharmacotherapy to induce oligodendrocyte differentiation and myelin formation post-injury.
Collapse
|
6
|
Chen L, Cheng J, Yang X, Jin X, Qi Z, Jin YQ. Bone marrow-derived cells response in proximal regions of nerves after peripheral nerve injury. Cell Biol Int 2017; 41:863-870. [PMID: 28544161 DOI: 10.1002/cbin.10796] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Accepted: 05/21/2017] [Indexed: 12/11/2022]
Affiliation(s)
- Lulu Chen
- Department No.16 of Plastic Surgery Hospital; Chinese Academy of Medical Sciences & Peking Union Medical College; Beijing China
| | - Jia Cheng
- Department of Burn and Plastic Surgery; Wuxi 3rd People's Hospital; Wuxi Jiangsu China
| | - Xiaonan Yang
- Department No.16 of Plastic Surgery Hospital; Chinese Academy of Medical Sciences & Peking Union Medical College; Beijing China
| | - Xiaolei Jin
- Department No.16 of Plastic Surgery Hospital; Chinese Academy of Medical Sciences & Peking Union Medical College; Beijing China
| | - Zuoliang Qi
- Department No.16 of Plastic Surgery Hospital; Chinese Academy of Medical Sciences & Peking Union Medical College; Beijing China
| | - Yu-Qing Jin
- Department of Plastic and Reconstructive Surgery; Shanghai 1st People's Hospital; Shanghai Jiao Tong University School of Medicine; Shanghai China
| |
Collapse
|
7
|
Canavero S, Ren X, Kim CY, Rosati E. Neurologic foundations of spinal cord fusion (GEMINI). Surgery 2016; 160:11-19. [PMID: 27180142 DOI: 10.1016/j.surg.2016.01.027] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 01/08/2016] [Accepted: 01/21/2016] [Indexed: 12/17/2022]
Abstract
Cephalosomatic anastomosis has been carried out in both monkeys and mice with preservation of brain function. Nonetheless the spinal cord was not reconstructed, leaving the animals unable to move voluntarily. Here we review the details of the GEMINI spinal cord fusion protocol, which aims at restoring electrophysiologic conduction across an acutely transected spinal cord. The existence of the cortico-truncoreticulo-propriospinal pathway, a little-known anatomic entity, is described, and its importance concerning spinal cord fusion emphasized. The use of fusogens and electrical stimulation as adjuvants for nerve fusion is addressed. The possibility of achieving cephalosomatic anastomosis in humans has become reality in principle.
Collapse
Affiliation(s)
| | - XiaoPing Ren
- Hand and Microsurgical Center, the Second Affiliated Hospital of Harbin Medical University; State-Province Key Laboratories of Biomedicine-Pharmaceutics, Harbin Medical University, Harbin, China; Department of Molecular Pharmacology and Therapeutics, Stritch School of Medicine, Loyola University Chicago, Chicago, IL
| | - C-Yoon Kim
- Department of Bioengineering, College of Life Science, CHA University, Seoul, Korea; Department of Laboratory Animal Medicine, College of Veterinary Medicine, Seoul National University, Seoul, Korea
| | | |
Collapse
|
8
|
Chu T, Zhou H, Li F, Wang T, Lu L, Feng S. Astrocyte transplantation for spinal cord injury: current status and perspective. Brain Res Bull 2014; 107:18-30. [PMID: 24878447 DOI: 10.1016/j.brainresbull.2014.05.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2014] [Revised: 05/17/2014] [Accepted: 05/19/2014] [Indexed: 02/07/2023]
Abstract
Spinal cord injury (SCI) often causes incurable neurological dysfunction because axonal regeneration in adult spinal cord is rare. Astrocytes are gradually recognized as being necessary for the regeneration after SCI as they promote axonal growth under both physiological and pathophysiological conditions. Heterogeneous populations of astrocytes have been explored for structural and functional restoration. The results range from the early variable and modest effects of immature astrocyte transplantation to the later significant, but controversial, outcomes of glial-restricted precursor (GRP)-derived astrocyte (GDA) transplantation. However, the traditional neuron-centric view and the concerns about the inhibitory roles of astrocytes after SCI, along with the sporadic studies and the lack of a comprehensive review, have led to some confusion over the usefulness of astrocytes in SCI. It is the purpose of the review to discuss the current status of astrocyte transplantation for SCI based on a dialectical view of the context-dependent manner of astrocyte behavior and the time-associated characteristics of glial scarring. Critical issues are then analyzed to reveal the potential direction of future research.
Collapse
Affiliation(s)
- Tianci Chu
- Department of Orthopaedics, Tianjin Medical University General Hospital, Anshan Road No. 154, Heping District, Tianjin 300052, PR China.
| | - Hengxing Zhou
- Department of Orthopaedics, Tianjin Medical University General Hospital, Anshan Road No. 154, Heping District, Tianjin 300052, PR China.
| | - Fuyuan Li
- Department of Orthopaedics, Tianjin Medical University General Hospital, Anshan Road No. 154, Heping District, Tianjin 300052, PR China.
| | - Tianyi Wang
- Department of Orthopaedics, Tianjin Medical University General Hospital, Anshan Road No. 154, Heping District, Tianjin 300052, PR China.
| | - Lu Lu
- Department of Orthopaedics, Tianjin Medical University General Hospital, Anshan Road No. 154, Heping District, Tianjin 300052, PR China.
| | - Shiqing Feng
- Department of Orthopaedics, Tianjin Medical University General Hospital, Anshan Road No. 154, Heping District, Tianjin 300052, PR China.
| |
Collapse
|
9
|
Öztürk G, Cengiz N, Erdoğan E, Him A, Oğuz EK, Yenidünya E, Ayşit N. Two distinct types of dying back axonal degenerationin vitro. Neuropathol Appl Neurobiol 2013; 39:362-76. [DOI: 10.1111/j.1365-2990.2012.01295.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
|
10
|
Grous LC, Vernengo J, Jin Y, Himes BT, Shumsky JS, Fischer I, Lowman A. Implications of poly(N-isopropylacrylamide)-g-poly(ethylene glycol) with codissolved brain-derived neurotrophic factor injectable scaffold on motor function recovery rate following cervical dorsolateral funiculotomy in the rat. J Neurosurg Spine 2013; 18:641-52. [PMID: 23581453 DOI: 10.3171/2013.3.spine12874] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT In a follow-up study to their prior work, the authors evaluated a novel delivery system for a previously established treatment for spinal cord injury (SCI), based on a poly(N-isopropylacrylamide) (PNIPAAm), lightly cross-linked with a polyethylene glycol (PEG) injectable scaffold. The primary aim of this work was to assess the recovery of both spontaneous and skilled forelimb function following a cervical dorsolateral funiculotomy in the rat. This injury ablates the rubrospinal tract (RST) but spares the dorsal and ventral corticospinal tract and can severely impair reaching and grasping abilities. METHODS Animals received an implant of either PNIPAAm-g-PEG or PNIPAAm-g-PEG + brain-derived neurotrophic factor (BDNF). The single-pellet reach-to-grasp task and the staircase-reaching task were used to assess skilled motor function associated with reaching and grasping abilities, and the cylinder task was used to assess spontaneous motor function, both before and after injury. RESULTS Because BDNF can stimulate regenerating RST axons, the authors showed that animals receiving an implant of PNIPAAm-g-PEG with codissolved BDNF had an increased recovery rate of fine motor function when compared with a control group (PNIPAAm-g-PEG only) on both a staircase-reaching task at 4 and 8 weeks post-SCI and on a single-pellet reach-to-grasp task at 5 weeks post-SCI. In addition, spontaneous motor function, as measured in the cylinder test, recovered to preinjury values in animals receiving PNIPAAm-g-PEG + BDNF. Fluorescence immunochemistry indicated the presence of both regenerating axons and BDA-labeled fibers growing up to or within the host-graft interface in animals receiving PNIPAAm-g-PEG + BDNF. CONCLUSIONS Based on their results, the authors suggest that BDNF delivered by the scaffold promoted the growth of RST axons into the lesion, which may have contributed in part to the increased recovery rate.
Collapse
Affiliation(s)
- Lauren Conova Grous
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104, USA.
| | | | | | | | | | | | | |
Collapse
|
11
|
Cengiz N, Oztürk G, Erdoğan E, Him A, Oğuz EK. Consequences of neurite transection in vitro. J Neurotrauma 2012; 29:2465-74. [PMID: 20121423 DOI: 10.1089/neu.2009.0947] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In order to quantify degenerative and regenerative changes and analyze the contribution of multiple factors to the outcome after neurite transection, we cultured adult mouse dorsal root ganglion neurons, and with a precise laser beam, we transected the nerve fibers they extended. Cell preparations were continuously visualized for 24 h with time-lapse microscopy. More distal cuts caused a more elongated field of degeneration, while thicker neurites degenerated faster than thinner ones. Transected neurites degenerated more if the uncut neurites of the same neuron simultaneously degenerated. If any of these uncut processes regenerated, the transected neurites underwent less degeneration. Regeneration of neurites was limited to distal cuts. Unipolar neurons had shorter regeneration than multipolar ones. Branching slowed the regenerative process, while simultaneous degeneration of uncut neurites increased it. Proximal lesions, small neuronal size, and extensive and rapid neurite degeneration were predictive of death of an injured neuron, which typically displayed necrotic rather than apoptotic form. In conclusion, this in vitro model proved useful in unmasking many new aspects and correlates of mechanically-induced neurite injury.
Collapse
Affiliation(s)
- Nurettin Cengiz
- Department of Histology and Embryology, Yüzüncü Yil University Medical School, Van, Turkey
| | | | | | | | | |
Collapse
|
12
|
Chew DJ, Fawcett JW, Andrews MR. The challenges of long-distance axon regeneration in the injured CNS. PROGRESS IN BRAIN RESEARCH 2012. [PMID: 23186719 DOI: 10.1016/b978-0-444-59544-7.00013-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Injury to the central nervous system (CNS) that results in long-tract axonal damage typically leads to permanent functional deficits in areas innervated at, and below, the level of the lesion. The initial ischemia, inflammation, and neurodegeneration are followed by a progressive generation of scar tissue, dieback of transected axons, and demyelination, creating an area inhibitory to regrowth and recovery. Two ways to combat this inhibition is to therapeutically target the extrinsic and intrinsic properties of the axon-scar environment. Scar tissue within and surrounding the lesion site can be broken down using an enzyme known as chondroitinase. Negative regulators of adult neuronal growth, such as Nogo, can be neutralized with antibodies. Both therapies greatly improve functional recovery in animal models. Alternatively, modifying the intrinsic growth properties of CNS neurons through gene therapy or pharmacotherapy has also shown promising axonal regeneration after injury. Despite these promising therapies, the main challenge of long-distance axon regeneration still remains; achieving a level of functional and organized connectivity below the level of the lesion that mimics the intact CNS.
Collapse
Affiliation(s)
- Daniel J Chew
- Centre for Brain Repair, University of Cambridge, Forvie Site, Robinson Way, Cambridge, UK
| | | | | |
Collapse
|
13
|
Transforming growth factor α transforms astrocytes to a growth-supportive phenotype after spinal cord injury. J Neurosci 2011; 31:15173-87. [PMID: 22016551 DOI: 10.1523/jneurosci.3441-11.2011] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Astrocytes are both detrimental and beneficial for repair and recovery after spinal cord injury (SCI). These dynamic cells are primary contributors to the growth-inhibitory glial scar, yet they are also neuroprotective and can form growth-supportive bridges on which axons traverse. We have shown that intrathecal administration of transforming growth factor α (TGFα) to the contused mouse spinal cord can enhance astrocyte infiltration and axonal growth within the injury site, but the mechanisms of these effects are not well understood. The present studies demonstrate that the epidermal growth factor receptor (EGFR) is upregulated primarily by astrocytes and glial progenitors early after SCI. TGFα directly activates the EGFR on these cells in vitro, inducing their proliferation, migration, and transformation to a phenotype that supports robust neurite outgrowth. Overexpression of TGFα in vivo by intraparenchymal adeno-associated virus injection adjacent to the injury site enhances cell proliferation, alters astrocyte distribution, and facilitates increased axonal penetration at the rostral lesion border. To determine whether endogenous EGFR activation is required after injury, SCI was also performed on Velvet (C57BL/6J-Egfr(Vel)/J) mice, a mutant strain with defective EGFR activity. The affected mice exhibited malformed glial borders, larger lesions, and impaired recovery of function, indicating that intrinsic EGFR activation is necessary for neuroprotection and normal glial scar formation after SCI. By further stimulating precursor proliferation and modifying glial activation to promote a growth-permissive environment, controlled stimulation of EGFR at the lesion border may be considered in the context of future strategies to enhance endogenous cellular repair after injury.
Collapse
|
14
|
Rosas OR, Figueroa JD, Torrado AI, Rivera M, Santiago JM, Konig-Toro F, Miranda JD. Expression and activation of ephexin is altered after spinal cord injury. Dev Neurobiol 2011; 71:595-607. [PMID: 20949525 DOI: 10.1002/dneu.20848] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Failure of axon regeneration after traumatic spinal cord injury (SCI) is attributable in part to the presence of inhibitory molecular interactions. Recent evidence demonstrates that activation of Eph signaling pathways leads to modulation of growth cone dynamics and repulsion through the activation of ephexin, a novel guanine nucleotide exchange factor (GEF). However, little is known about the expression and modulation of Eph molecular targets in the injured spinal cord. In this study, we determined the expression profile of ephexin after a moderate spinal cord contusion at thoracic level (T10) in young adult rats. Western-blot studies showed increased protein expression in injured rats at 4 and 7 days postinjury (DPI) when compared with control animals. The protein levels returned to normal at 14 DPI and remained steady until 28 DPI. However, immunoprecipitation studies of the phosphorylated ephexin demonstrated that this protein is activated by day 2 until 14 DPI. Expression of ephexin was noticeable in neurons, axons, microglia/macrophages, and reactive astrocytes, and co-localized with EphA3, A4, and A7. These results demonstrate the presence of ephexin in the adult spinal cord and its activation after SCI. Therefore, we show, for the first time, the spatiotemporal pattern of ephexin expression and activation after contusive SCI. Collectively, our data support our previous findings on the putative nonpermissive roles of Eph receptors after SCI and the possible involvement of ephexin in the intracellular cascade of events.
Collapse
Affiliation(s)
- Odrick R Rosas
- Department of Physiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico 00936
| | | | | | | | | | | | | |
Collapse
|
15
|
Krisa L, Frederick KL, Canver JC, Stackhouse SK, Shumsky JS, Murray M. Amphetamine-enhanced motor training after cervical contusion injury. J Neurotrauma 2011; 29:971-89. [PMID: 21651384 DOI: 10.1089/neu.2011.1767] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Individually, motor training, pharmacological interventions, and housing animals in an enriched environment (EE) following spinal cord injury (SCI) result in limited functional improvement but, when combined, may enhance motor function. Here, we tested amphetamine (AMPH)-enhanced skilled motor training following a unilateral C3-C4 contusion injury on the qualitative components of reaching and on skilled forelimb function, as assessed using single-pellet and staircase reaching tasks. Kinematic analysis evaluated the quality of the reach, and unskilled locomotor function was also tested. Animals receiving AMPH and skilled forelimb training performed better than operated control animals on qualitative reaching, but not on skilled reaching. Those that received the combination treatment and were housed in EE cages showed significantly less improvement in qualitative reaching and grasping. Kinematic analysis revealed a decrease in digit abduction during skilled reaching among all groups, with no differences among groups. Kinematics provided no evidence that improved function was related to improved quality of reach. There was no evidence of neuroprotection in the cervical spinal cord. The absence of evidence for kinematic improvement or neuroprotection suggested that AMPH-enhanced motor training is due primarily to supraspinal effects, an enhancement of attention during skilled motor training, or plasticity in supraspinal circuitry involved with motor control.
Collapse
Affiliation(s)
- Laura Krisa
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129, USA
| | | | | | | | | | | |
Collapse
|
16
|
Morris R, Tosolini AP, Goldstein JD, Whishaw IQ. Impaired arpeggio movement in skilled reaching by rubrospinal tract lesions in the rat: a behavioral/anatomical fractionation. J Neurotrauma 2011; 28:2439-51. [PMID: 21612320 DOI: 10.1089/neu.2010.1708] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Spinal cord injury damaging the rubrospinal tract (RST) interferes with skilled forelimb movement, but identification of the precise role of the RST in this behavior is impeded by the difficulty of surgically isolating the RST from other pathways running within the lateral funiculus (LF). The present study used a skilled reaching task and a behavioral/anatomical dissection method to identify the contribution of the RST to skilled forelimb movement. Rats were trained on the skilled reaching task and subjected to lesions of the LF. Based on histological evaluation, the animals were assigned to large, medium, or small LF lesion size groups. End point and arm/hand/digit movements were subsequently identified for each group. Success was impaired in all groups, but the impairment was not related to lesion size. Frame-by-frame qualitative analysis of the video recordings revealed that large LF lesions abolished the elements of digits close, digits open, arpeggio, grasp, supination 2, and release. Medium LF lesions interfered with a subset of the movement elements that were shown to be affected by the large LF lesions, namely arpeggio and grasp. Only the arpeggio movement was compromised after small LF lesions. The results show that not only does the LF contribute to skilled reaching, but because the RST was likely to have been damaged in all lesion groups, the RST is more involved in hand rotation than in digit use. The results are discussed in relation to the fiber tracts that are likely to be damaged in the different LF lesion groups.
Collapse
Affiliation(s)
- Renée Morris
- Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales, Sydney, New South Wales, Australia.
| | | | | | | |
Collapse
|
17
|
Conta Steencken AC, Smirnov I, Stelzner DJ. Cell survival or cell death: differential vulnerability of long descending and thoracic propriospinal neurons to low thoracic axotomy in the adult rat. Neuroscience 2011; 194:359-71. [PMID: 21645590 DOI: 10.1016/j.neuroscience.2011.05.052] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 05/12/2011] [Accepted: 05/20/2011] [Indexed: 12/21/2022]
Abstract
Previous studies show that most short thoracic propriospinal (TPS; T5-T7) and long descending propriospinal tract (LDPT; C4-C6) neurons are lost following low-thoracic spinal cord contusion injury (cSCI), as assessed by retrograde labeling with fluorogold (FG). Gene microarray and terminal deoxynucleotidyl transferase dUTP nick end (TUNEL)/caspase-3 immunolabeling indicate that post-axotomy cell death may be responsible for the observed decrease in number of labeled TPS neurons post cSCI. Yet, no indications of post-axotomy cell death are evident within LDPT neurons following the same injury. The present experiments were devised to understand this difference. We assessed the number and size of LDPT and TPS neurons at different time points, retrogradely labeling these neurons with FG prior to delivering a moderate low-thoracic cSCI or after they were axotomized by a complete low-thoracic spinal transection. Counts of FG-filled TPS and LDPT cells indicate a large loss of both neuronal populations 2 weeks post cSCI. Propriospinal neurons in other animals were retrogradely labeled with dextran tetramethyl rhodamine prior to cSCI and tissue was processed for detection of TUNEL- or caspase-3-positive profiles at chronic times post injury. Our overall findings confirm that cell death post injury is the major factor responsible for the loss of TPS neurons during the acute period post cSCI, and that little post-axotomy cell death occurs in LDPT neurons during the first 2 months after the same injury. After chronic axotomy retrograde transport is impaired in LDPT neurons, but can be reinitiated by re-axotomy. Our results also indicate that FG is metabolized/lost from retrogradely labeled neurons at increasing survival times, and that this process appears to be accelerated by injury.
Collapse
Affiliation(s)
- A C Conta Steencken
- Department of Cell and Developmental Biology, College of Graduate Studies, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | | | | |
Collapse
|
18
|
Rehermann MI, Santiñaque FF, López-Carro B, Russo RE, Trujillo-Cenóz O. Cell proliferation and cytoarchitectural remodeling during spinal cord reconnection in the fresh-water turtle Trachemys dorbignyi. Cell Tissue Res 2011; 344:415-33. [PMID: 21574060 DOI: 10.1007/s00441-011-1173-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Accepted: 04/11/2011] [Indexed: 01/22/2023]
Abstract
In fresh-water turtles, the bridge connecting the proximal and caudal stumps of transected spinal cords consists of regenerating axons running through a glial cellular matrix. To understand the process leading to the generation of the scaffold bridging the lesion, we analyzed the mitotic activity triggered by spinal injury in animals maintained alive for 20-30 days after spinal cord transection. Flow cytometry and bromodeoxyuridine (BrdU)-labeling experiments revealed a significant increment of cycling cells around the lesion epicenter. BrdU-tagged cells maintained a close association with regenerating axons. Most dividing cells expressed the brain lipid-binding protein (BLBP). Cells with BrdU-positive nuclei expressed glial fibrillary acidic protein. As spinal cord regeneration involves dynamic cell rearrangements, we explored the ultra-structure of the bridge and found cells with the aspect of immature oligodendrocytes forming an embryonic-like microenvironment. These cells supported and ensheathed regenerating axons that were recognized by immunocytological and electron-microscopical procedures. Since functional recovery depends on proper impulse transmission, we examined the anatomical axon-glia relationships near the lesion epicenter. Computer-assisted three-dimensional models revealed helical axon-glial junctions in which the intercellular space appeared to be reduced (5-7 nm). Serial-sectioning analysis revealed that fibril-containing processes provided myelinating axon sheaths. Thus, disruption of the ependymal layer elicits mitotic activity predominantly in radial glia expressing BLBP on the lateral aspects of the ependyma. These cycling cells seem to migrate and contribute to the bridge providing the main support and sheaths for regenerating axons.
Collapse
Affiliation(s)
- María Inés Rehermann
- Departamento de Neurofisiología Celular y Molecular, Avenida Italia 3318, Montevideo, Uruguay
| | | | | | | | | |
Collapse
|
19
|
Filous AR, Miller JH, Coulson-Thomas YM, Horn KP, Alilain WJ, Silver J. Immature astrocytes promote CNS axonal regeneration when combined with chondroitinase ABC. Dev Neurobiol 2011; 70:826-41. [PMID: 20629049 DOI: 10.1002/dneu.20820] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Regeneration of injured adult CNS axons is inhibited by formation of a glial scar. Immature astrocytes are able to support robust neurite outgrowth and reduce scarring, therefore, we tested whether these cells would have this effect if transplanted into brain injuries. Utilizing an in vitro spot gradient model that recreates the strongly inhibitory proteoglycan environment of the glial scar we found that, alone, immature, but not mature, astrocytes had a limited ability to form bridges across the most inhibitory outer rim. In turn, the astrocyte bridges could promote adult sensory axon re-growth across the gradient. The use of selective enzyme inhibitors revealed that MMP-2 enables immature astrocytes to cross the proteoglycan rim. The bridge-building process and axon regeneration across the immature glial bridges were greatly enhanced by chondroitinase ABC pretreatment of the spots. We used microlesions in the cingulum of the adult rat brains to test the ability of matrix modification and immature astrocytes to form a bridge for axon regeneration in vivo. Injured axons were visualized via p75 immunolabeling and the extent to which these axons regenerated was quantified. Immature astrocytes coinjected with chondroitinase ABC-induced axonal regeneration beyond the distal edge of the lesion. However, when used alone, neither treatment was capable of promoting axonal regeneration. Our findings indicate that when faced with a minimal lesion, neurons of the basal forebrain can regenerate in the presence of a proper bridge across the lesion and when levels of chondroitin sulfate proteoglycans (CSPGs) in the glial scar are reduced.
Collapse
Affiliation(s)
- Angela R Filous
- Department of Neurosciences, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA.
| | | | | | | | | | | |
Collapse
|
20
|
Martinez M, Rossignol S. Changes in CNS structures after spinal cord lesions implications for BMI. PROGRESS IN BRAIN RESEARCH 2011; 194:191-202. [PMID: 21867804 DOI: 10.1016/b978-0-444-53815-4.00007-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
It is well established that a spinal circuitry can generate locomotor movements of the hindlimbs in absence of descending supraspinal inputs. This is based, among others, on the observation that after a complete spinalization, cats can walk with the hindlimbs on a treadmill. Does this spinal pattern generator (CPG) also participate in the recovery of locomotion after a partial spinal cord lesion (SCI)? After such SCI, functional reorganization can occur spontaneously along the whole neuraxis, namely the spinal cord circuitry below the lesion (CPG) and in supraspinal structures still partially connected to the spinal cord. This review focuses mainly on the capacity of the spinal and supraspinal structures to reorganize spontaneously after incomplete SCI in animals (rats and cats). BMI approaches to foster recovery of functions after various types of SCI should take into account these changes at the various levels of the CNS.
Collapse
Affiliation(s)
- M Martinez
- Department of Physiology, Groupe de Recherche sur le Système Nerveux Central, Faculty of Medicine, Université de Montréal, SensoriMotor Rehabilitation Research Team of the Canadian Institute for Health Research, Montréal, Québec, Canada
| | | |
Collapse
|
21
|
Chen J, Joon Lee H, Jakovcevski I, Shah R, Bhagat N, Loers G, Liu HY, Meiners S, Taschenberger G, Kügler S, Irintchev A, Schachner M. The extracellular matrix glycoprotein tenascin-C is beneficial for spinal cord regeneration. Mol Ther 2010; 18:1769-77. [PMID: 20606643 DOI: 10.1038/mt.2010.133] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Tenascin-C (TNC), a major component of the extracellular matrix, is strongly upregulated after injuries of the central nervous system (CNS) but its role in tissue repair is not understood. Both regeneration promoting and inhibiting roles of TNC have been proposed considering its abilities to both support and restrict neurite outgrowth in vitro. Here, we show that spontaneous recovery of locomotor functions after spinal cord injury is impaired in adult TNC-deficient (TNC(-/-)) mice in comparison to wild-type (TNC(+/+)) mice. The impaired recovery was associated with attenuated excitability of the plantar Hoffmann reflex (H-reflex), reduced glutamatergic input, reduced sprouting of monaminergic axons in the lumbar spinal cord and enhanced post-traumatic degeneration of corticospinal axons. The degeneration of corticospinal axons in TNC(-/-) mice was normalized to TNC(+/+) levels by application of the alternatively spliced TNC fibronectin type III homologous domain D (fnD). Finally, overexpression of TNC-fnD via adeno-associated virus in wild-type mice improved locomotor recovery, increased monaminergic axons sprouting, and reduced lesion scar volume after spinal cord injury. The functional efficacy of the viral-mediated TNC indicates a potentially useful approach for treatment of spinal cord injury.
Collapse
Affiliation(s)
- Jian Chen
- W.M. Keck Center for Collaborative Neuroscience, Department of Cell Biology and Neuroscience, Rutgers the State University of New Jersey, Piscataway, New Jersey, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Tillakaratne NJK, Guu JJ, de Leon RD, Bigbee AJ, London NJ, Zhong H, Ziegler MD, Joynes RL, Roy RR, Edgerton VR. Functional recovery of stepping in rats after a complete neonatal spinal cord transection is not due to regrowth across the lesion site. Neuroscience 2010; 166:23-33. [PMID: 20006680 PMCID: PMC2820384 DOI: 10.1016/j.neuroscience.2009.12.010] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Accepted: 12/03/2009] [Indexed: 01/15/2023]
Abstract
Rats receiving a complete spinal cord transection (ST) at a neonatal stage spontaneously can recover significant stepping ability, whereas minimal recovery is attained in rats transected as adults. In addition, neonatally spinal cord transected rats trained to step more readily improve their locomotor ability. We hypothesized that recovery of stepping in rats receiving a complete spinal cord transection at postnatal day 5 (P5) is attributable to changes in the lumbosacral neural circuitry and not to regeneration of axons across the lesion. As expected, stepping performance measured by several kinematics parameters was significantly better in ST (at P5) trained (treadmill stepping for 8 weeks) than age-matched non-trained spinal rats. Anterograde tracing with biotinylated dextran amine showed an absence of labeling of corticospinal or rubrospinal tract axons below the transection. Retrograde tracing with Fast Blue from the spinal cord below the transection showed no labeled neurons in the somatosensory motor cortex of the hindlimb area, red nucleus, spinal vestibular nucleus, and medullary reticular nucleus. Retrograde labeling transsynaptically via injection of pseudorabies virus (Bartha) into the soleus and tibialis anterior muscles showed no labeling in the same brain nuclei. Furthermore, re-transection of the spinal cord at or rostral to the original transection did not affect stepping ability. Combined, these results clearly indicate that there was no regeneration across the lesion after a complete spinal cord transection in neonatal rats and suggest that this is an important model to understand the higher level of locomotor recovery in rats attributable to lumbosacral mechanisms after receiving a complete ST at a neonatal compared to an adult stage.
Collapse
Affiliation(s)
- N J K Tillakaratne
- Department of Physiological Science, University of California, Los Angeles, Los Angeles, CA 90095, USA.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Rehermann MI, Marichal N, Russo RE, Trujillo-Cenóz O. Neural reconnection in the transected spinal cord of the freshwater turtle Trachemys dorbignyi. J Comp Neurol 2009; 515:197-214. [PMID: 19418545 PMCID: PMC2697850 DOI: 10.1002/cne.22061] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
This paper provides the first evidence that freshwater turtles are able to reconnect their completely transected spinal cords, leading to some degree of recovery of the motor functions lost after injury. Videographic analysis showed that some turtles (5 of 11) surviving more than 20 days after injury were able to initiate stepping locomotion. However, the stepping movements were slower than those of normal animals, and swimming patterns were not restored. Even though just 45% of the injured turtles recovered their stepping patterns, all showed axonal sprouting beyond the lesion site. Immunocytochemical and electron microscope images revealed the occurrence of regrowing axons crossing the severed region. A major contingent of the axons reconnecting the cord originated from sensory neurons lying in dorsal ganglia adjacent to the lesion site. The axons bridging the damaged region traveled on a cellular scaffold consisting of brain lipid-binding protein (BLBP)- and glial fibrillary acidic protein (GFAP)-positive cells and processes. Serotonergic varicose nerve fibers and endings were found at early stages of the healing process at the epicenter of the lesion. Interestingly, the glial scar commonly found in the damaged central nervous system of mammals was absent. In contrast, GFAP- and BLBP-positive processes were found running parallel to the main axis of the cord accompanying the crossing axons.
Collapse
Affiliation(s)
- María Inés Rehermann
- Departamento de Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, CP11600, Montevideo, Uruguay
| | | | | | | |
Collapse
|
24
|
Wang L, Hu B, Wong WM, Lu P, Wu W, Xu XM. Glial and axonal responses in areas of Wallerian degeneration of the corticospinal and dorsal ascending tracts after spinal cord dorsal funiculotomy. Neuropathology 2009; 29:230-41. [DOI: 10.1111/j.1440-1789.2008.00969.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
|
25
|
Brazda N, Müller HW. Pharmacological modification of the extracellular matrix to promote regeneration of the injured brain and spinal cord. PROGRESS IN BRAIN RESEARCH 2009; 175:269-81. [PMID: 19660662 DOI: 10.1016/s0079-6123(09)17518-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
This chapter focuses on the role of the fibrous lesion scar as a major impediment for axonal regeneration in the injured central nervous system (CNS). We describe the appearance and complementary distribution of the glial and fibrous scar components in spinal cord lesions focusing on the morphology as well as on axon growth inhibitory molecular components accumulating in the collagenous and basement membrane-rich fibrous scar. We further report on the differential responses to fibrous scar of distinct fiber tracts in the injured spinal cord including the rubrospinal and corticospinal tracts as well as serotonergic, dopaminergic, and calcitonin gene-related peptide (CGRP) systems. Finally, we discuss therapeutic strategies to suppress fibrous scarring in traumatic CNS injury with particular emphasis on a unique pharmacological treatment using iron chelators and cyclic adenosine monophosphate (cAMP) to inhibit collagen biosynthesis. The latter treatment has been shown to promote long-distance axon growth, retrograde protection of injured neurons, and significant functional improvement.
Collapse
Affiliation(s)
- Nicole Brazda
- Department of Neurology, Heinrich Heine University of Düsseldorf, Düsseldorf, Germany
| | | |
Collapse
|
26
|
Task-dependent compensation after pyramidal tract and dorsolateral spinal lesions in rats. Exp Neurol 2008; 216:193-206. [PMID: 19118552 DOI: 10.1016/j.expneurol.2008.11.028] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Revised: 11/26/2008] [Accepted: 11/26/2008] [Indexed: 11/20/2022]
Abstract
The purpose of this research was to investigate whether pathways in the dorsal part of the lateral spinal funiculus (DLF) can compensate for loss of corticospinal input (CST) to the spinal cord. The CST is known to control skilled limb movements in rats. The DLF contains several different pathways, including the rubrospinal tract (RST) which is also thought to influence limb movements. After lesions of either the corticospinal or the rubrospinal system, it is unclear how much of the remaining forelimb function is due to the presence of the alternate pathway. To begin to address this issue, the present study investigates the compensatory role of pathways in the DLF, including the rubrospinal tract, after bilateral lesions of the pyramidal tract (PT). We initially performed bilateral PT lesions in rats, which effectively removed the CST input to the spinal cord. We tested these rats during overground locomotion, skilled locomotion and skilled forelimb usage. After a 6 week recovery period, we then performed bilateral DLF lesions and compared the behavioural abilities of these rats to those of animals which underwent simultaneous PT and DLF lesions. If DLF pathways do compensate for PT lesions, then animals with PT lesions would rely more on DLF pathways than animals without PT lesions. Thus we hypothesized that animals with DLF lesions which were performed 6 weeks after PT lesions would exhibit more deficits on several behavioural tasks compared to animals which received PT and DLF lesions simultaneously. Our hypothesis was supported only for skilled pellet retrieval. Hence some DLF pathways, including the RST, were able to compensate for loss of CST input during skilled reaching but not during overground or skilled locomotion in PT-lesioned rats. These differential responses suggest that behavioural tasks vary in their reliance on specific pathways after injury, and, furthermore, that compensation for loss of specific connections can arise from numerous sources.
Collapse
|
27
|
Stackhouse SK, Murray M, Shumsky JS. Effect of cervical dorsolateral funiculotomy on reach-to-grasp function in the rat. J Neurotrauma 2008; 25:1039-47. [PMID: 18721108 DOI: 10.1089/neu.2007.0419] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Cervical spinal cord injury (SCI) can severely impair reaching and grasping ability, and several descending systems, including the rubrospinal tract and corticospinal tract, have been implicated in the control of reach-to-grasp movements. The primary aim of this study was to characterize further the forelimb deficits associated with a cervical dorsolateral funiculotomy, which ablates the rubrospinal tract but spares the dorsal and ventral corticospinal tract in the rat. Adult female rats that preferred to use their right forelimb to reach for single pellets received a lesion to the right cervical dorsolateral funiculus between the C3-4 dorsal roots. Gross forelimb motor function was assessed by measuring spontaneous forelimb usage during exploration in a cylinder, and fine motor function was assessed using staircase and single pellet reaching tests. Single pellet reaching was further evaluated by qualitative and quantitative kinematic scoring of the movement components. Histological analysis included the quantification of spared white matter. Cervical dorsolateral funiculotomy produced marked deficits in reaching performance on both the single pellet and staircase reaching tests, with transient deficits in gross forelimb usage in the cylinder. Quantitative kinematics also revealed a reduction in digit abduction during the reach, which persisted throughout the 8-week post-SCI period. Tests of reach-to-grasp function, therefore, were more sensitive than a test of gross forelimb usage after cervical dorsolateral funiculotomy and did not show recovery over the 8-week survival period. We suggest that the staircase test is a useful screening tool for intervention studies because of its ease of implementation, and that the single pellet test is valuable for examining reaching accuracy and detailed kinematics.
Collapse
Affiliation(s)
- Scott K Stackhouse
- Department of Physical Therapy, Arcadia University, Glenside, Pennsylvania 19038, USA.
| | | | | |
Collapse
|
28
|
Another barrier to regeneration in the CNS: activated macrophages induce extensive retraction of dystrophic axons through direct physical interactions. J Neurosci 2008; 28:9330-41. [PMID: 18799667 DOI: 10.1523/jneurosci.2488-08.2008] [Citation(s) in RCA: 259] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Injured axons of the adult CNS undergo lengthy retraction from the initial site of axotomy after spinal cord injury. Macrophage infiltration correlates spatiotemporally with this deleterious phenomenon, but the direct involvement of these inflammatory cells has not been demonstrated. In the present study, we examined the role of macrophages in axonal retraction within the dorsal columns after spinal cord injury in vivo and found that retraction occurred between days 2 and 28 after lesion and that the ends of injured axons were associated with ED-1+ cells. Clodronate liposome-mediated depletion of infiltrating macrophages resulted in a significant reduction in axonal retraction; however, we saw no evidence of regeneration. We used time-lapse imaging of adult dorsal root ganglion neurons in an in vitro model of the glial scar to examine macrophage-axon interactions and observed that adhesive contacts and considerable physical interplay between macrophages and dystrophic axons led to extensive axonal retraction. The induction of retraction was dependent on both the growth state of the axon and the activation state of the macrophage. Only dystrophic adult axons were susceptible to macrophage "attack." Unlike intrinsically active cell line macrophages, both primary macrophages and microglia required activation to induce axonal retraction. Contact with astrocytes had no deleterious effect on adult dystrophic axons, suggesting that the induction of extensive retraction was specific to phagocytic cells. Our data are the first to indicate a direct role of activated macrophages in axonal retraction by physical cell-cell interactions with injured axons.
Collapse
|
29
|
Cao Y, Shumsky JS, Sabol MA, Kushner RA, Strittmatter S, Hamers FPT, Lee DHS, Rabacchi SA, Murray M. Nogo-66 receptor antagonist peptide (NEP1-40) administration promotes functional recovery and axonal growth after lateral funiculus injury in the adult rat. Neurorehabil Neural Repair 2007; 22:262-78. [PMID: 18056009 DOI: 10.1177/1545968307308550] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE The myelin protein Nogo inhibits axon regeneration by binding to its receptor (NgR) on axons. Intrathecal delivery of an NgR antagonist (NEP1-40) promotes growth of injured corticospinal axons and recovery of motor function following a dorsal hemisection. The authors used a similar design to examine recovery and repair after a lesion that interrupts the rubrospinal tract (RST). METHODS Rats received a lateral funiculotomy at C4 and NEP1-40 or vehicle was delivered to the cervical spinal cord for 4 weeks. Outcome measures included motor and sensory tests and immunohistochemistry. RESULTS Gait analysis showed recovery in the NEP1-40-treated group compared to operated controls, and a test of forelimb usage also showed a beneficial effect. The density of labeled RST axons increased ipsilaterally in the NEP1-40 group in the lateral funiculus rostral to the lesion and contralaterally in both gray and white matter. Thus, rubrospinal axons exhibited diminished dieback and/or growth up to the lesion site. This was accompanied by greater density of 5HT and calcitonin gene-related peptide axons adjacent to and into the lesion/matrix site in the NEP1-40 group. CONCLUSIONS NgR blockade after RST injury is associated with axonal growth and/or diminished dieback of severed RST axons up to but not into or beyond the lesion/matrix site, and growth of serotonergic and dorsal root axons adjacent to and into the lesion/matrix site. NgR blockade also supported partial recovery of function. The authors' results indicate that severed rubrospinal axons respond to NEP1-40 treatment but less robustly than corticospinal, raphe-spinal, or dorsal root axons.
Collapse
Affiliation(s)
- Y Cao
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Seif GI, Nomura H, Tator CH. Retrograde axonal degeneration "dieback" in the corticospinal tract after transection injury of the rat spinal cord: a confocal microscopy study. J Neurotrauma 2007; 24:1513-28. [PMID: 17892412 DOI: 10.1089/neu.2007.0323] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Axonal dieback is a process in which axons in spinal tracts retract away from the initial site of injury. The purpose of this project is to study the dynamics of dieback in corticospinal tract (CST) axons after various time intervals post-injury, to find the optimal spatial-temporal window for regenerative treatment. Rats received transection injuries at the T8 spinal level and were sacrificed at different time periods (1, 2, 4, 8, and 16 weeks). Three weeks prior to sacrifice, DiI crystals were implanted in the sensorimotor cortex and produced excellent CST labeling, and clear delineation of the terminal bulbs of transected axons. With DiI and confocal microscopy, we visualized axons along the entire length of the CST, and quantified the temporal and spatial features of dieback in axons of the CST based on the location of the terminal bulbs. We found that the majority of axons stopped dieing back 4 weeks after injury by which time they were approximately 2.5 mm from the site of injury. However, at 8 and 16 weeks after injury, some terminal bulbs were more than 10 and 19 mm, respectively, from the site of injury.
Collapse
Affiliation(s)
- Gamal I Seif
- Institute of Medical Science, University of Toronto, Toronto, Canada
| | | | | |
Collapse
|
31
|
Soares S, Barnat M, Salim C, von Boxberg Y, Ravaille-Veron M, Nothias F. Extensive structural remodeling of the injured spinal cord revealed by phosphorylated MAP1B in sprouting axons and degenerating neurons. Eur J Neurosci 2007; 26:1446-61. [PMID: 17880387 DOI: 10.1111/j.1460-9568.2007.05794.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Spinal cord injury (SCI) results in loss of sensory and motor function because injured axons do not regenerate and neurons that die are not replaced. Nevertheless, there is evidence for spontaneous reorganization of spared pathways (i.e. sprouting) that could be exploited to improve functional recovery. The extent of morphological remodeling after spinal cord injury is, however, not understood. We have previously shown that a phosphorylated form of microtubule-associated protein-1B, MAP1B-P, is expressed by growing axons, but is detected in intact adult SC in fibers exhibiting a somatotopic distribution of myelinated sensory fibers. We now demonstrate that after adult SCI, MAP1B-P is up-regulated in other classes of axons. We used immunohistochemistry to show changing levels and distributions of MAP1B-P after a right thoracic hemisection of adult rat spinal cord. MAP1B-P labeling suggests rearrangements of the axonal circuitry that go well beyond previous descriptions. MAP1B-P-positive fibers are present in ectopic locations in gray matter in both dorsal and ventral horns and around the central canal. Double staining reveals that primary sensory and descending serotonergic and corticospinal axons are MAP1B-P positive. In white matter, high MAP1B-P expression is found on terminal enlargements near the injury, reflecting retraction of transected axons. MAP1B-P also accumulates in pre-apoptotic neuronal somata axotomized by the lesion, indicating association of MAP1B-P not only with axon extension and retraction, but also with neuronal degeneration. Finally, we provide evidence that MAP1B phosphorylation is correlated with activation of JNK MAP-kinase, providing a step towards unraveling the mechanisms of regulation of this plasticity-related cytoskeletal protein.
Collapse
Affiliation(s)
- Sylvia Soares
- Université Pierre et Marie Curie-Paris6, UMR7101 NSI, Paris, F-75005 France
| | | | | | | | | | | |
Collapse
|
32
|
Blesch A, Tuszynski MH. Transient growth factor delivery sustains regenerated axons after spinal cord injury. J Neurosci 2007; 27:10535-45. [PMID: 17898225 PMCID: PMC6673161 DOI: 10.1523/jneurosci.1903-07.2007] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2007] [Revised: 08/09/2007] [Accepted: 08/16/2007] [Indexed: 01/09/2023] Open
Abstract
Growth factors influence the topography of axonal projections during nervous system development and facilitate axonal sprouting and regeneration after injury in the adult. However, in the absence of target reinnervation and reestablishment of synaptic activity, we hypothesized that continuing delivery of neurotrophins would be required to sustain regenerating axons for prolonged times points after neurotrophin-induced axon growth after spinal cord injury (SCI) in the adult. Using tetracycline-inducible expression of brain-derived neurotrophic factor by genetically modified fibroblasts, we were able to extensively and significantly turn growth factor expression "on" or "off" in vitro and in vivo within sites of SCI. Notably, we find that transient growth factor delivery is sufficient to sustain regenerated axons for prolonged time periods within spinal cord lesion sites. Immunohistochemical analysis demonstrated an absence of neuronal targets or synapses within transient growth factor expressing grafts but the persistent presence of Schwann cells. Thus, the adult CNS appears capable of sustaining axons that have extended after transient growth factor delivery, an effect potentially attributable to the persistence of Schwann cells in lesion/graft sites.
Collapse
Affiliation(s)
- Armin Blesch
- Department of Neurosciences, University of California, San Diego, La Jolla, California 92093, USA.
| | | |
Collapse
|
33
|
Freund P, Wannier T, Schmidlin E, Bloch J, Mir A, Schwab ME, Rouiller EM. Anti-Nogo-A antibody treatment enhances sprouting of corticospinal axons rostral to a unilateral cervical spinal cord lesion in adult macaque monkey. J Comp Neurol 2007; 502:644-59. [PMID: 17394135 DOI: 10.1002/cne.21321] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
After injury, regrowth of axons in mammalian adult central nervous system is highly limited. However, in monkeys subjected to unilateral cervical lesion (C7-C8 level), neutralization of an important neurite outgrowth inhibitor, Nogo-A, stimulated axonal sprouting caudal to the lesion, accompanied by enhanced functional recovery of manual dexterity, compared with lesioned monkeys treated with a control antibody (Freund et al. [2006] Nat. Med. 12:790-792). The present study aimed at comparing the same two groups of monkeys for axonal sprouting rostral to the cervical lesion. The corticospinal tract was labeled by injecting the anterograde tracer biotinylated dextran amine into the contralesional motor cortex. The corticospinal axons were interrupted at the level of the lesion, accompanied by retrograde axonal degeneration (axon dieback), reflected by the presence of terminal retraction bulbs. The number of terminal retraction bulbs was lower in anti-Nogo-A antibody treated monkeys, and, when present, they were found closer to the lesion than in control-antibody treated monkeys. Compared with control antibody treated monkeys, the anti-Nogo-A antibody treated monkeys exhibited an increased cumulated axon arbor length and a higher number of axon arbors going in the medial direction from the white to the gray matter. Higher in the cervical cord (at C5 level), the anti-Nogo-A treatment enhanced the number of corticospinal fibers crossing the midline, suggesting axonal sprouting. Thus, the anti-Nogo-A antibody treatment enhanced axonal sprouting rostral to the cervical lesion; some of these fibers grew around the lesion and into the caudal spinal segments. These processes paralleled the observed improved functional recovery.
Collapse
Affiliation(s)
- Patrick Freund
- Unit of Physiology and Program in Neurosciences, Department of Medicine, Faculty of Sciences, University of Fribourg, CH-1700 Fribourg, Switzerland
| | | | | | | | | | | | | |
Collapse
|
34
|
Dinh P, Bhatia N, Rasouli A, Suryadevara S, Cahill K, Gupta R. Transplantation of preconditioned Schwann cells following hemisection spinal cord injury. Spine (Phila Pa 1976) 2007; 32:943-9. [PMID: 17450067 DOI: 10.1097/01.brs.0000261408.61303.77] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Chronically compressed sciatic nerve segments were transplanted to hemisected spinal cord injured rats. Histologic evaluation and behavior functional outcomes were tested after 6 weeks following surgery. OBJECTIVE To evaluate the outcome of preconditioned peripheral nerves as a permissive environment in axonal regeneration of the injured spinal cord. SUMMARY OF BACKGROUND DATA Schwann cells have been used to facilitate a permissive environment for the injured spinal cord to regenerate. Previous experiments have shown compressive mechanical stress to be important in stimulating the regenerative behavior of Schwann cells. Transplantation of highly permissive Schwann cell-enriched peripheral nerve grafts may enhance regeneration in spinal cord injury. METHODS Adult Sprague-Dawley rats (n = 24) were used to create a hemisection injury of the spinal cord. At 1-week postinjury creation, the spinal cords were reexposed for all animals. Peripheral nerve grafts were obtained from rat sciatic nerve, either untreated or subjected to mechanical compression for 2 weeks with nonconstrictive tubing. Transplantation of grafts was performed after a resection of the glial scar. Functional outcome was measured using the Basso, Beattie, Bresnahan Locomotor Rating Score and footprint analysis. Tract tracing of descending and ascending spinal cord tracts was performed at 6 weeks after surgery for histologic evaluation of axonal regeneration. RESULTS Preconditioned transplants had significantly higher Basso, Beattie, Bresnahan Scores versus hemisection alone in the late postoperative period (P < 0.05). They also had significantly less foot exorotation and base of support when compared to nonconditioned transplants. Histologic analysis showed increased regeneration at lesional sites for preconditioned transplants versus control group (P < 0.05). CONCLUSIONS Functional recovery after hemisection injury improved significantly in the late postoperative period with transplantation of preconditioned peripheral nerve. Preconditioned grafts also exhibit sustained axonal regeneration at and past the lesional site in histologic analysis. Further investigation with later time points is warranted.
Collapse
Affiliation(s)
- Paul Dinh
- University of California, Irvine, CA, USA
| | | | | | | | | | | |
Collapse
|
35
|
Muir GD, Webb AA, Kanagal S, Taylor L. Dorsolateral cervical spinal injury differentially affects forelimb and hindlimb action in rats. Eur J Neurosci 2007; 25:1501-10. [PMID: 17425576 DOI: 10.1111/j.1460-9568.2007.05411.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In experimental spinal injury studies, damage to the dorsal half of the spinal cord is common but the behavioural effects of damage to specific pathways in the dorsal cord have been less well investigated. We performed bilateral transection of the dorsolateral spinal funiculus (DLF) on 12 Long-Evans rats at the third cervical spinal segment. We quantified overground locomotion by measuring ground reaction forces, step timing and step distances as animals moved unrestrained. We also assessed skilled locomotion by measuring footslip errors made while the animals crossed horizontal ladders, and examined paw usage in a cylinder exploration task and during a skilled reaching task. Ground reaction forces revealed that rats with bilateral DLF lesions moved with a symmetrical gait, characterized mainly by altered forces exerted by the hindlimbs, delayed onset of hindlimb stance, and understepping of the hindlimbs relative to the forelimbs. These alterations in overground locomotion were subtle but were nevertheless consistent between animals and persisted throughout the 6-week recovery period. During ladder crossing, rats with DLF lesions made more footslip errors with the hindlimbs after surgery than before. Spontaneous forelimb usage during exploration was not affected by DLF axotomy but lesioned animals were less successful during skilled reaching. This is the first study which describes preferentially altered hindlimb use during overground locomotion after cervical DLF transections. We discuss these findings in relation to previous work and to the possible contributions of different ascending and descending pathways in the DLF to locomotion and skilled movements in rats.
Collapse
Affiliation(s)
- Gillian D Muir
- Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK, Canada S7N 5B4.
| | | | | | | |
Collapse
|
36
|
Chen J, Wu J, Apostolova I, Skup M, Irintchev A, Kügler S, Schachner M. Adeno-associated virus-mediated L1 expression promotes functional recovery after spinal cord injury. Brain 2007; 130:954-69. [PMID: 17438016 DOI: 10.1093/brain/awm049] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Paucity of permissive molecules and abundance of inhibitory molecules in the injured spinal cord of adult mammals prevent axons from successful regeneration and, thus, contribute to the failure of functional recovery. Using an adeno-associated viral (AAV) vector, we expressed the regeneration-promoting cell adhesion molecule L1 in both neurons and glia in the lesioned spinal cord of adult mice. Exogenous L1, detectable already 1 week after thoracic spinal cord compression and immediate vector injection, was expressed at high levels up to 5 weeks, the longest time-period studied. Dissemination of L1-transduced cells throughout the spinal cord was wide, spanning over more than 10 mm rostral and 10 mm caudal to the lesion scar. L1 was not detectable in the fibronectin-positive lesion core. L1 overexpression led to improved stepping abilities and muscle coordination during ground locomotion over a 5-week observation period. Superior functional improvement was associated with enhanced reinnervation of the lumbar spinal cord by 5-HT axons. Corticospinal tract axons did not regrow beyond the lesion scar but extended distally into closer proximity to the injury site in AAV-L1-treated compared with control mice. The expression of the neurite outgrowth-inhibitory chondroitin sulphate proteoglycan NG2 was decreased in AAV-L1-treated spinal cords, along with reduction of the reactive astroglial marker GFAP. In vitro experiments confirmed that L1 inhibits astrocyte proliferation, migration, process extension and GFAP expression. Analyses of intracellular signalling indicated that exogenous L1 activates diverse cascades in neurons and glia. Thus, AAV-mediated L1 overexpression appears to be a potent means to favourably modify the local environment in the injured spinal cord and promote regeneration. Our study demonstrates a clinically feasible approach of promising potential.
Collapse
Affiliation(s)
- Jian Chen
- W. M. Keck Center for Collaborative Neuroscience, Department of Cell Biology and Neuroscience, Rutgers the State University of New Jersey, Piscataway, NJ 08854, USA
| | | | | | | | | | | | | |
Collapse
|
37
|
Woolfe F, Waxman SG, Hains BC. In SilicoModeling of Axonal Reconnection within A Discrete Fiber Tract after Spinal Cord Injury. J Neurotrauma 2007; 24:421-32. [PMID: 17376004 DOI: 10.1089/neu.2006.0131] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Following spinal cord injury (SCI), descending axons that carry motor commands from the brain to the spinal cord are injured or transected, producing chronic motor dysfunction and paralysis. Reconnection of these axons is a major prerequisite for restoration of function after SCI. Thus far, only modest gains in motor function have been achieved experimentally or in the clinic after SCI, identifying the practical limitations of current treatment approaches. In this paper, we use an ordinary differential equation (ODE) to simulate the relative and synergistic contributions of several experimentally-established biological factors related to inhibition or promotion of axonal repair and restoration of function after SCI. The factors were mathematically modeled by the ODE. The results of our simulation show that in a model system, many factors influenced the achievability of axonal reconnection. Certain factors more strongly affected axonal reconnection in isolation, and some factors interacted in a synergistic fashion to produce further improvements in axonal reconnection. Our data suggest that mathematical modeling may be useful in evaluating the complex interactions of discrete therapeutic factors not possible in experimental preparations, and highlight the benefit of a combinatorial therapeutic approach focused on promoting axonal sprouting, attraction of cut ends, and removal of growth inhibition for achieving axonal reconnection. Predictions of this simulation may be of utility in guiding future experiments aimed at restoring function after SCI.
Collapse
Affiliation(s)
- Franco Woolfe
- Department of Applied Mathematics, Yale University, New Haven, Connecticut 06516, USA
| | | | | |
Collapse
|
38
|
Vaidla E, Talvik I, Kulla A, Sibul H, Maasalu K, Metsvaht T, Piirsoo A, Talvik T. Neonatal spinal muscular atrophy type 1 with bone fractures and heart defect. J Child Neurol 2007; 22:67-70. [PMID: 17608308 DOI: 10.1177/0883073807299954] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The authors present the case of an infant girl with severe generalized weakness, multiple bone fractures, and heart defect. She needed mechanical ventilation from birth. Radiographs showed mid-diaphyseal fractures of both humeri and of the right femur as well as generalized osteopenia. Electroneuromyography showed spontaneous fibrillations at rest with no active movements. Motor response to a stimulus could not be registered. A systolic heart murmur was detected, and echocardiography showed a large atrial septal defect and an additional membrane in the left atrium. DNA analysis confirmed the diagnosis of spinal muscular atrophy on the third day of life. Histology of the muscle showed both hypertrophic and atrophic fibers. Degenerating swollen neurons were found in the ventral horns of the spinal cord and also in the mesencephalic red nucleus, which has not been described before. Humeral bone showed only partly formed cortical bone. The spectrum of spinal muscular atrophy is very diverse, and atypical clinical findings do not always rule out 5q spinal muscular atrophy. The SMN1 gene should still be investigated.
Collapse
Affiliation(s)
- Eve Vaidla
- Department of Pediatrics, Tartu University, 6 Lunini Street, Tartu 51014, Estonia
| | | | | | | | | | | | | | | |
Collapse
|
39
|
Houle JD, Tom VJ, Mayes D, Wagoner G, Phillips N, Silver J. Combining an autologous peripheral nervous system "bridge" and matrix modification by chondroitinase allows robust, functional regeneration beyond a hemisection lesion of the adult rat spinal cord. J Neurosci 2006; 26:7405-15. [PMID: 16837588 PMCID: PMC6674179 DOI: 10.1523/jneurosci.1166-06.2006] [Citation(s) in RCA: 261] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Chondroitinase-ABC (ChABC) was applied to a cervical level 5 (C5) dorsal quadrant aspiration cavity of the adult rat spinal cord to degrade the local accumulation of inhibitory chondroitin sulfate proteoglycans. The intent was to enhance the extension of regenerated axons from the distal end of a peripheral nerve (PN) graft back into the C5 spinal cord, having bypassed a hemisection lesion at C3. ChABC-treated rats showed (1) gradual improvement in the range of forelimb swing during locomotion, with some animals progressing to the point of raising their forelimb above the nose, (2) an enhanced ability to use the forelimb in a cylinder test, and (3) improvements in balance and weight bearing on a horizontal rope. Transection of the PN graft, which cuts through regenerated axons, greatly diminished these functional improvements. Axonal regrowth from the PN graft correlated well with the behavioral assessments. Thus, many more axons extended for much longer distances into the cord after ChABC treatment and bridge insertion compared with the control groups, in which axons regenerated into the PN graft but growth back into the spinal cord was extremely limited. These results demonstrate, for the first time, that modulation of extracellular matrix components after spinal cord injury promotes significant axonal regeneration beyond the distal end of a PN bridge back into the spinal cord and that regenerating axons can mediate the return of useful function of the affected limb.
Collapse
Affiliation(s)
- John D Houle
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129, USA.
| | | | | | | | | | | |
Collapse
|
40
|
Deumens R, Koopmans GC, Joosten EAJ. Regeneration of descending axon tracts after spinal cord injury. Prog Neurobiol 2005; 77:57-89. [PMID: 16271433 DOI: 10.1016/j.pneurobio.2005.10.004] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2005] [Revised: 08/23/2005] [Accepted: 10/05/2005] [Indexed: 02/03/2023]
Abstract
Axons within the adult mammalian central nervous system do not regenerate spontaneously after injury. Upon injury, the balance between growth promoting and growth inhibitory factors in the central nervous system dramatically changes resulting in the absence of regeneration. Axonal responses to injury vary considerably. In central nervous system regeneration studies, the spinal cord has received a lot of attention because of its relatively easy accessibility and its clinical relevance. The present review discusses the axon-tract-specific requirements for regeneration in the rat. This knowledge is very important for the development and optimalization of therapies to repair the injured spinal cord.
Collapse
Affiliation(s)
- Ronald Deumens
- Department of Psychiatry and Neuropsychology, Division Neuroscience, European Graduate School of Neuroscience EURON, University of Maastricht, Maastricht, The Netherlands.
| | | | | |
Collapse
|
41
|
Kerschensteiner M, Schwab ME, Lichtman JW, Misgeld T. In vivo imaging of axonal degeneration and regeneration in the injured spinal cord. Nat Med 2005; 11:572-7. [PMID: 15821747 DOI: 10.1038/nm1229] [Citation(s) in RCA: 406] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2004] [Accepted: 01/02/2005] [Indexed: 11/09/2022]
Abstract
The poor response of central axons to transection underlies the bleak prognosis following spinal cord injury. Here, we monitor individual fluorescent axons in the spinal cords of living transgenic mice over several days after spinal injury. We find that within 30 min after trauma, axons die back hundreds of micrometers. This acute form of axonal degeneration is similar in mechanism to the more delayed Wallerian degeneration of the disconnected distal axon, but acute degeneration affects the proximal and distal axon ends equally. In vivo imaging further shows that many axons attempt regeneration within 6-24 h after lesion. This growth response, although robust, seems to fail as a result of the inability of axons to navigate in the proper direction. These results suggest that time-lapse imaging of spinal cord injury may provide a powerful analytical tool for assessing the pathogenesis of spinal cord injury and for evaluating therapies that enhance regeneration.
Collapse
Affiliation(s)
- Martin Kerschensteiner
- Department of Molecular and Cellular Biology, Harvard University, 7 Divinity Avenue, Cambridge, Massachusetts 02138, USA
| | | | | | | |
Collapse
|
42
|
Tom VJ, Steinmetz MP, Miller JH, Doller CM, Silver J. Studies on the development and behavior of the dystrophic growth cone, the hallmark of regeneration failure, in an in vitro model of the glial scar and after spinal cord injury. J Neurosci 2005; 24:6531-9. [PMID: 15269264 PMCID: PMC6729861 DOI: 10.1523/jneurosci.0994-04.2004] [Citation(s) in RCA: 216] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We have developed a novel in vitro model of the glial scar that mimics the gradient of proteoglycan found in vivo after spinal cord injury. In this model, regenerated axons from adult sensory neurons that extended deeply into the gradient developed bulbous, vacuolated endings that looked remarkably similar to dystrophic endings formed in vivo. We demonstrate that despite their highly abnormal appearance and stalled forward progress, dystrophic endings are extremely dynamic both in vitro and in vivo after spinal cord injury. Time-lapse movies demonstrated that dystrophic endings continually send out membrane veils and endocytose large membrane vesicles at the leading edge, which were then retrogradely transported to the rear of the "growth cone." This direction of movement is contrary to membrane dynamics that occur during normal neurite outgrowth. As further evidence of this motility, dystrophic endings endocytosed large amounts of dextran both in vitro and in vivo. We now have an in vitro model of the glial scar that may serve as a potent tool for developing and screening potential treatments to help promote regeneration past the lesion in vivo.
Collapse
Affiliation(s)
- Veronica J Tom
- Department of Neurosciences, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | | | | | | | | |
Collapse
|
43
|
Webb AA, Muir GD. Course of motor recovery following ventrolateral spinal cord injury in the rat. Behav Brain Res 2004; 155:55-65. [PMID: 15325779 DOI: 10.1016/j.bbr.2004.04.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2003] [Revised: 04/02/2004] [Accepted: 04/02/2004] [Indexed: 11/18/2022]
Abstract
The purpose of this study was to determine the importance of the pathways running in the ventrolateral spinal funiculus for overground locomotion in adult, freely behaving rats. Left-sided ventrolateral cervical spinal cord injury was performed in adult female Long-Evans rats. The behavioural abilities of these animals were analyzed at 2 days, and weekly for up to 5.5 weeks following spinal cord injury. Behavioural testing consisted of Von Frey filament testing, ladder walking, a paw usage task, and the assessment of ground reaction forces during unrestrained trotting. Animals with injury to the left ventrolateral cervical spinal cord did not develop enhanced sensitivity to pedal mechanical stimulation. At 2 days following injury, animals had impaired skilled locomotion as indicated by increased number of footslips during ladder walking. At 2 days, these animals also used both limbs together more often for support while rearing, while using the forelimb ipsilateral to the injury less than did uninjured animals. Ground reaction force determination revealed that animals tend to bear less weight on the forelimb and hindlimb ipsilateral to the spinal cord injury 2 days after injury. All animals recovered normal or near normal sensorimotor abilities although subtle asymmetries in ground reaction forces were detectable at 5.5 weeks following spinal cord injury. These results suggest that axons in the ventrolateral spinal funiculi contribute to limb movements during exploration and locomotion but their roles can be served by other pathways after ventrolateral spinal injury.
Collapse
Affiliation(s)
- Aubrey A Webb
- Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Sask., Canada S7N 5B4.
| | | |
Collapse
|
44
|
Gallo G. Myosin II activity is required for severing-induced axon retraction in vitro. Exp Neurol 2004; 189:112-21. [PMID: 15296841 DOI: 10.1016/j.expneurol.2004.05.019] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2003] [Revised: 04/28/2004] [Accepted: 05/14/2004] [Indexed: 11/23/2022]
Abstract
Understanding the mechanistic basis of the response of neurons to injury is directly relevant to the development of effective therapeutic approaches aimed at the amelioration of nervous system damage. Axons retract in response to severing. We investigated the mechanism of axon retraction in response to severing in vitro, testing the hypothesis that actomyosin contractility drives severing-induced axon retraction. Axon retraction commenced within 5 min following severing and correlated with actin filament accumulation at the site of severing. Depolymerization of actin filaments prevented retraction, demonstrating that actin filaments are required for severing-induced axon retraction. Direct inhibition of myosin II, using blebbistatin, minimized axon retraction in response to severing. Blocking RhoA-kinase (ROCK), a modulator of myosin II activity, inhibited axon retraction. Similarly, inhibiting myosin light chain kinase (MLCK) with a cell-permeable pseudo-substrate peptide also inhibited axon retraction. These data demonstrate that myosin II activity is required for severing-induced axon retraction in vitro, and suggest myosin II as a target for therapeutic interventions aimed at minimizing retraction following severing in vivo.
Collapse
Affiliation(s)
- Gianluca Gallo
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA.
| |
Collapse
|
45
|
Kwon BK, Liu J, Oschipok L, Teh J, Liu ZW, Tetzlaff W. Rubrospinal neurons fail to respond to brain-derived neurotrophic factor applied to the spinal cord injury site 2 months after cervical axotomy. Exp Neurol 2004; 189:45-57. [PMID: 15296835 DOI: 10.1016/j.expneurol.2004.05.034] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2004] [Revised: 05/05/2004] [Accepted: 05/13/2004] [Indexed: 01/07/2023]
Abstract
Numerous experimental therapies to promote axonal regeneration have shown promise in animal models of acute spinal cord injury, but their effectiveness is often found to diminish with a delay in administration. We evaluated whether brain-derived neurotrophic factor (BDNF) application to the spinal cord injury site 2 months after cervical axotomy could promote a regenerative response in chronically axotomized rubrospinal neurons. BDNF was applied to the spinal cord in three different concentrations 2 months after cervical axotomy of the rubrospinal tract. The red nucleus was examined for reversal of neuronal atrophy, GAP43 and Talpha1 tubulin mRNA expression, and trkB receptor immunoreactivity. A peripheral nerve transplant paradigm was used to measure axonal regeneration into peripheral nerve transplants. Rubrospinal axons were anterogradely traced and trkB receptor immunohistochemistry performed on the injured spinal cord. We found that BDNF treatment did not reverse rubrospinal neuronal atrophy, nor promote GAP-43 and Talpha1 tubulin mRNA expression, nor promote axonal regeneration into peripheral nerve transplants. TrkB receptor immunohistochemistry demonstrated immunoreactivity on the neuronal cell bodies, but not on anterogradely labeled rubrospinal axons at the injury site. These findings suggest that the poor response of rubrospinal neurons to BDNF applied to the spinal cord injury site 2 months after cervical axotomy is not related to the dose of BDNF administered, but rather to the loss of trkB receptors on the injured axons over time. Such obstacles to axonal regeneration will be important to identify in the development of therapeutic strategies for chronically injured individuals.
Collapse
Affiliation(s)
- Brian K Kwon
- International Collaboration on Repair Discoveries (ICORD), University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z4.
| | | | | | | | | | | |
Collapse
|
46
|
Fraidakis MJ, Spenger C, Olson L. Partial recovery after treatment of chronic paraplegia in rat. Exp Neurol 2004; 188:33-42. [PMID: 15191800 DOI: 10.1016/j.expneurol.2004.01.032] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2003] [Accepted: 01/30/2004] [Indexed: 11/15/2022]
Abstract
While acute spinal cord injury has been the object of intensive research, chronic spinal cord injury has received less attention although most clinical cases of spinal cord injury become chronic. We attempted to surgically "repair" chronic and acute spinal cord injury in a complete transection rat model using a multiple peripheral nerve grafting protocol. The lesion extent was assessed by magnetic resonance imaging (MRI) before the repair procedure. Rats were treated immediately after injury or at 2, 4, or 8 months postinjury. Standard behavioral methods were used to evaluate functional recovery. Two novel tests, the Bipedal Test and the Head-scratch test, were also employed to evaluate hindpaw positioning, interlimb coordination, and stepping rhythmicity, and to indicate rostrocaudal pathway regeneration. MRI helped guide the treatment procedure that was applied to animals with chronic injury. Treated animals demonstrated significant motor recovery. Axonal regeneration resultant to treatment was demonstrated histologically. The results suggest that not only acute but also chronic total paraplegia can be reversed to a moderate degree in rats with regard to hindlimb motor function.
Collapse
Affiliation(s)
- Matthew J Fraidakis
- Department of Neuroscience, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | | | | |
Collapse
|
47
|
Affiliation(s)
- Jerry Silver
- Department of Neurosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, USA.
| | | |
Collapse
|
48
|
Dolbeare D, Houle JD. Restriction of axonal retraction and promotion of axonal regeneration by chronically injured neurons after intraspinal treatment with glial cell line-derived neurotrophic factor (GDNF). J Neurotrauma 2004; 20:1251-61. [PMID: 14651811 DOI: 10.1089/089771503770802916] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The response of supraspinal neurons to acute or delayed treatment with GDNF following a spinal cord injury was examined. A cervical level 3 hemisection lesion cavity was created by tissue aspiration in adult, female rats. In one experiment gel foam saturated with GDNF was placed into the lesion cavity immediately after injury to determine if the extent of axonal retraction was affected by neurotrophic factor treatment. One week prior to sacrifice animals received a microinjection of biotinylated dextran amine (BDA) into the red nucleus and reticular formation to label descending spinal pathways by anterograde transport mechanisms. Animals were sacrificed 1 or 4 weeks after injury and treatment with GDNF. The terminal end of injured BDA-labeled rubrospinal and reticulospinal tract axons was identified and the distance from the lesion was measured. In comparison to PBS-treated animals, GDNF-treatment resulted in a significant decrease in the extent of axonal retraction of both rubrospinal and reticulospinal tract axons at 1 week after spinal cord injury for both tracts. At 4 weeks after injury the mean distance from the lesion was less than 240 microm following GDNF-treatment for both tracts, compared to over 480 microm following PBS-treatment. In the second experiment injured supraspinal neurons were labeled by retrograde transport of True Blue that had been placed into the lesion cavity. One month later scar tissue was removed from the cavity by aspiration to enlarge the cavity by approximately 500 microm in a rostral direction. GDNF-saturated gel foam was placed into the cavity for 60 min prior to apposition of an autologous peripheral nerve (PN) graft to the rostral cavity wall. One month later Nuclear Yellow was applied to the distal end of the PN graft and animals were sacrificed after 2 days. The number of supraspinal neurons containing both True Blue and Nuclear Yellow was counted as a measure of axonal regeneration by chronically injured neurons. There was a seven-fold increase in the number of regenerating neurons after GDNF-treatment, with the majority (65%) of dual-labeled neurons located within the reticular formation. These results indicate that GDNF has neuroprotective effects when provided acutely after injury and promotes axonal regeneration when provided in a chronic injury situation.
Collapse
Affiliation(s)
- Dirk Dolbeare
- Department of Anatomy and Neurobiology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA
| | | |
Collapse
|
49
|
Shumsky JS, Tobias CA, Tumolo M, Long WD, Giszter SF, Murray M. Delayed transplantation of fibroblasts genetically modified to secrete BDNF and NT-3 into a spinal cord injury site is associated with limited recovery of function. Exp Neurol 2004; 184:114-30. [PMID: 14637085 DOI: 10.1016/s0014-4886(03)00398-4] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Delivery of neurotrophic factors in acute models of spinal cord injury in adult rats can rescue axotomized neurons, promote axonal growth, and partially restore function. The extent to which repair and recovery of function can be achieved after chronic injury has received less attention. In the companion paper we show that transplanting fibroblasts genetically modified to produce neurotrophic factors into chronic (6-week) hemisection injuries results in sprouting, partial neuroprotection, but only limited regeneration. Here we describe functional consequences of this treatment using a series of behavioral tests. Adult rats received a complete unilateral C3/C4 hemisection and recovery from the injury was assessed over 5 weeks. At 6 weeks postoperative, the experimental group received grafts of a combination of fibroblasts modified to secrete BDNF or NT-3. The operated control groups received grafts of either gelfoam or gelfoam with fibroblasts expressing GFP into the lesion site. Behavioral recovery in the three groups was assessed over the next 10 weeks. Severe deficits with no recovery in any of the groups were observed in several tests (BBB, limb preference, narrow beam, horizontal rope test) that measure primarily motor function. Recovery was observed in the grid test, a measure of sensorimotor function, and the von Frey test, a measure of response to mechanical stimulation, but there were no differences between the operated control or experimental groups. Both groups also showed recovery from heat-induced hyperalgesia, with the experimental group exhibiting greater recovery than the operated control groups. In this test, delivery of neurotrophic factors from transplanted fibroblasts does not worsen responses to nociceptive stimuli and in fact appears to reduce hypersensitivity. Our data also demonstrate that additional damage to the spinal cord upon placement of a graft further compromises behavioral recovery for locomotor and postural function. Additional therapeutic interventions will be necessary to provide greater levels of recovery after chronic injuries.
Collapse
Affiliation(s)
- J S Shumsky
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, PA 19129, USA.
| | | | | | | | | | | |
Collapse
|
50
|
Abstract
Advances in medical and rehabilitative care now allow the 10-12,000 individuals who suffer spinal cord injuries each year in the United States to lead productive lives of nearly normal life expectancy, so that the numbers of those with chronic injuries will approximate 300,000 at the end of the next decade. This signals an urgent need for new treatments that will improve repair and recovery after longstanding injuries. In the present report we consider the characteristics of the chronically injured spinal cord that make it an even more challenging setting in which to elicit regeneration than the acutely injured spinal cord and review the treatments that have been designed to enhance axon growth. When applied in the first 2 weeks after experimental spinal cord injury, transplants, usually in combination with supplementary neurotrophic factors, and possibly modifications of the inhibitory central nervous system environment, have produced limited long-distance axon regeneration and behavioral recovery. When applied to injuries older than 4 weeks, the same treatments have almost invariably failed to overcome the obstacles posed by the neurons' diminished capacity for regeneration and by the increasing hostility to growth of the terrain at and beyond the injury site. Novel treatments that have stimulated regeneration after acute injuries have not yet been applied to chronic injuries. A therapeutic strategy that combines rehabilitation training and pharmacological modulation of neurotransmitters appears to be a particularly promising approach to increasing recovery after longstanding injury. Identifying patients with no hope of useful recovery in the early days after injury will allow these treatments to be administered as early as possible.
Collapse
Affiliation(s)
- John D Houle
- Department of Anatomy and Neurobiology, University of Arkansas for Medical Science, Little Rock, AR 72205, USA.
| | | |
Collapse
|