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Zheng G, Zheng F, Luo Z, Ma H, Zheng D, Xiang G, Xu C, Zhou Y, Wu Y, Tian N, Wu Y, Zhang T, Ni W, Wang S, Xu H, Zhang X. CO-Releasing Molecule (CORM)-3 Ameliorates Spinal Cord-Blood Barrier Disruption Following Injury to the Spinal Cord. Front Pharmacol 2020; 11:761. [PMID: 32581781 PMCID: PMC7287126 DOI: 10.3389/fphar.2020.00761] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 05/07/2020] [Indexed: 01/01/2023] Open
Abstract
Spinal cord injury (SCI) is a clinical tough neurological problem without efficient cure currently. Blood-spinal cord barrier (BSCB) interruption is not only a crucial pathological feature for SCI process but is a possible target for future SCI treatments; however, few treatments have been developed to intervene BSCB. In the present study, we intravenously injected CO-releasing molecule3 (CORM-3), a classical exogenous CO donor, to the rats experiencing SCI and assessed its protection on BSCB integrity in rats. Our results demonstrated that the exogenous increasing of CO by CORM-3 blocked the tight junction (TJ) protein degeneration and neutrophils infiltration, subsequently suppressed the BSCB damage and improved the motor recovery after SCI. And we certified that the CO-induced down-regulation of MMP-9 expression and activity in neutrophil might be associated with the NF-κB signaling. Taken together, our study indicates that CO-releasing molecule (CORM)-3 ameliorates BSCB after spinal cord injury.
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Affiliation(s)
- Gang Zheng
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China.,Zhejiang Provincial Key Laboratory of Orthpaedics, Wenzhou, China
| | - Fanghong Zheng
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China.,Zhejiang Provincial Key Laboratory of Orthpaedics, Wenzhou, China.,The Second School of Medicine, Wenzhou Medical University, Wenzhou, China
| | - Zucheng Luo
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China.,Zhejiang Provincial Key Laboratory of Orthpaedics, Wenzhou, China
| | - Haiwei Ma
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China.,Zhejiang Provincial Key Laboratory of Orthpaedics, Wenzhou, China
| | - Dongdong Zheng
- Department of Neurosurgery, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China
| | - Guangheng Xiang
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China.,Zhejiang Provincial Key Laboratory of Orthpaedics, Wenzhou, China
| | - Cong Xu
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China.,Zhejiang Provincial Key Laboratory of Orthpaedics, Wenzhou, China
| | - Yifei Zhou
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China.,Zhejiang Provincial Key Laboratory of Orthpaedics, Wenzhou, China.,The Second School of Medicine, Wenzhou Medical University, Wenzhou, China
| | - Yaosen Wu
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China.,Zhejiang Provincial Key Laboratory of Orthpaedics, Wenzhou, China.,The Second School of Medicine, Wenzhou Medical University, Wenzhou, China
| | - Naifeng Tian
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China.,Zhejiang Provincial Key Laboratory of Orthpaedics, Wenzhou, China.,The Second School of Medicine, Wenzhou Medical University, Wenzhou, China
| | - Yan Wu
- Department of Orthopaedics, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Wenzhou, China
| | - Tan Zhang
- Department of Orthopaedics, Shaoxing People's Hospital, Shaoxing, Wenzhou, China
| | - Wenfei Ni
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China.,Zhejiang Provincial Key Laboratory of Orthpaedics, Wenzhou, China
| | - Sheng Wang
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China.,Zhejiang Provincial Key Laboratory of Orthpaedics, Wenzhou, China.,The Second School of Medicine, Wenzhou Medical University, Wenzhou, China
| | - Huazi Xu
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China.,Zhejiang Provincial Key Laboratory of Orthpaedics, Wenzhou, China.,The Second School of Medicine, Wenzhou Medical University, Wenzhou, China
| | - Xiaolei Zhang
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China.,Zhejiang Provincial Key Laboratory of Orthpaedics, Wenzhou, China.,The Second School of Medicine, Wenzhou Medical University, Wenzhou, China.,Department of Orthopaedics, Chinese Orthopaedic Regenerative Medicine Society, Hangzhou, China
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Sweeney MD, Zhao Z, Montagne A, Nelson AR, Zlokovic BV. Blood-Brain Barrier: From Physiology to Disease and Back. Physiol Rev 2019; 99:21-78. [PMID: 30280653 PMCID: PMC6335099 DOI: 10.1152/physrev.00050.2017] [Citation(s) in RCA: 1187] [Impact Index Per Article: 237.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 04/17/2018] [Accepted: 04/17/2018] [Indexed: 12/12/2022] Open
Abstract
The blood-brain barrier (BBB) prevents neurotoxic plasma components, blood cells, and pathogens from entering the brain. At the same time, the BBB regulates transport of molecules into and out of the central nervous system (CNS), which maintains tightly controlled chemical composition of the neuronal milieu that is required for proper neuronal functioning. In this review, we first examine molecular and cellular mechanisms underlying the establishment of the BBB. Then, we focus on BBB transport physiology, endothelial and pericyte transporters, and perivascular and paravascular transport. Next, we discuss rare human monogenic neurological disorders with the primary genetic defect in BBB-associated cells demonstrating the link between BBB breakdown and neurodegeneration. Then, we review the effects of genes underlying inheritance and/or increased susceptibility for Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease, and amyotrophic lateral sclerosis (ALS) on BBB in relation to other pathologies and neurological deficits. We next examine how BBB dysfunction relates to neurological deficits and other pathologies in the majority of sporadic AD, PD, and ALS cases, multiple sclerosis, other neurodegenerative disorders, and acute CNS disorders such as stroke, traumatic brain injury, spinal cord injury, and epilepsy. Lastly, we discuss BBB-based therapeutic opportunities. We conclude with lessons learned and future directions, with emphasis on technological advances to investigate the BBB functions in the living human brain, and at the molecular and cellular level, and address key unanswered questions.
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Affiliation(s)
- Melanie D Sweeney
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , Los Angeles, California ; and Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California , Los Angeles, California
| | - Zhen Zhao
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , Los Angeles, California ; and Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California , Los Angeles, California
| | - Axel Montagne
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , Los Angeles, California ; and Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California , Los Angeles, California
| | - Amy R Nelson
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , Los Angeles, California ; and Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California , Los Angeles, California
| | - Berislav V Zlokovic
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , Los Angeles, California ; and Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California , Los Angeles, California
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Kumar H, Ropper AE, Lee SH, Han I. Propitious Therapeutic Modulators to Prevent Blood-Spinal Cord Barrier Disruption in Spinal Cord Injury. Mol Neurobiol 2016; 54:3578-3590. [PMID: 27194298 DOI: 10.1007/s12035-016-9910-6] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Accepted: 05/03/2016] [Indexed: 01/09/2023]
Abstract
The blood-spinal cord barrier (BSCB) is a specialized protective barrier that regulates the movement of molecules between blood vessels and the spinal cord parenchyma. Analogous to the blood-brain barrier (BBB), the BSCB plays a crucial role in maintaining the homeostasis and internal environmental stability of the central nervous system (CNS). After spinal cord injury (SCI), BSCB disruption leads to inflammatory cell invasion such as neutrophils and macrophages, contributing to permanent neurological disability. In this review, we focus on the major proteins mediating the BSCB disruption or BSCB repair after SCI. This review is composed of three parts. Section 1. SCI and the BSCB of the review describes critical events involved in the pathophysiology of SCI and their correlation with BSCB integrity/disruption. Section 2. Major proteins involved in BSCB disruption in SCI focuses on the actions of matrix metalloproteinases (MMPs), tumor necrosis factor alpha (TNF-α), heme oxygenase-1 (HO-1), angiopoietins (Angs), bradykinin, nitric oxide (NO), and endothelins (ETs) in BSCB disruption and repair. Section 3. Therapeutic approaches discusses the major therapeutic compounds utilized to date for the prevention of BSCB disruption in animal model of SCI through modulation of several proteins.
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Affiliation(s)
- Hemant Kumar
- Department of Neurosurgery, CHA University, CHA Bundang Medical Center, Seongnam-si, Gyeonggi-do, 13496, Republic of Korea
| | - Alexander E Ropper
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX, USA
| | - Soo-Hong Lee
- Department of Biomedical Science, CHA University, Seongnam-si, Gyeonggi-do, 13488, Republic of Korea.
| | - Inbo Han
- Department of Neurosurgery, CHA University, CHA Bundang Medical Center, Seongnam-si, Gyeonggi-do, 13496, Republic of Korea.
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Najafi E, Stoodley MA, Bilston LE, Hemley SJ. Inwardly rectifying potassium channel 4.1 expression in post-traumatic syringomyelia. Neuroscience 2016; 317:23-35. [PMID: 26768400 DOI: 10.1016/j.neuroscience.2016.01.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2015] [Revised: 12/23/2015] [Accepted: 01/02/2016] [Indexed: 10/22/2022]
Abstract
Post-traumatic syringomyelia (PTS) is a serious neurological disorder characterized by fluid filled cavities that develop in the spinal cord. PTS is thought to be caused by an imbalance between fluid inflow and outflow in the spinal cord, but the underlying mechanisms are unknown. The ion channel Kir4.1 plays an important role in the uptake of K(+) ions from the extracellular space and release of K(+) ions into the microvasculature, generating an osmotic gradient that drives water movement. Changes in Kir4.1 expression may contribute to disturbances in K(+) homeostasis and subsequently fluid imbalance. Here we investigated whether changes in Kir4.1 protein expression occur in PTS. Western blotting and immunohistochemistry were used to evaluate Kir4.1 and glial fibrillary acidic protein (GFAP) expression in a rodent model of PTS at 3 days, 1, 6 or 12 weeks post-surgery. In Western blotting experiments, Kir4.1 expression increased 1 week post-surgery at the level of the cavity. Immunohistochemical analysis examined changes in the spinal parenchyma directly in contact with the syrinx cavity. In these experiments, there was a significant decrease in Kir4.1 expression in PTS animals compared to controls at 3 days and 6 weeks post-surgery, while an up-regulation of GFAP in PTS animals was observed at 1 and 12 weeks. This suggests that while overall Kir4.1 expression is unchanged at these time-points, there are many astrocytes surrounding the syrinx cavity that are not expressing Kir4.1. The results demonstrate a disturbance in the removal of K(+) ions in tissue surrounding a post-traumatic syrinx cavity. It is possible this contributes to water accumulation in the injured spinal cord leading to syrinx formation or exacerbation of the underlying pathology.
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Affiliation(s)
- E Najafi
- Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW, Australia.
| | - M A Stoodley
- Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW, Australia.
| | - L E Bilston
- Neuroscience Research Australia, Sydney, NSW, Australia; Prince of Wales Clinical School, University of New South Wales, Randwick, NSW, Australia.
| | - S J Hemley
- Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW, Australia.
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5
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Cahill LS, Laliberté CL, Liu XJ, Bishop J, Nieman BJ, Mogil JS, Sorge RE, Jones CD, Salter MW, Henkelman RM. Quantifying blood-spinal cord barrier permeability after peripheral nerve injury in the living mouse. Mol Pain 2014; 10:60. [PMID: 25216623 PMCID: PMC4190293 DOI: 10.1186/1744-8069-10-60] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2014] [Accepted: 09/10/2014] [Indexed: 11/16/2022] Open
Abstract
Background Genetic polymorphisms, gender and age all influence the risk of developing chronic neuropathic pain following peripheral nerve injury (PNI). It is known that there are significant inter-strain differences in pain hypersensitivity in strains of mice after PNI. In response to PNI, one of the earliest events is thought to be the disruption of the blood-spinal cord barrier (BSCB). The study of BSCB integrity after PNI may lead to a better understanding of the mechanisms that contribute to chronic pain. Results Here we used in vivo dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) to establish a timecourse for BSCB permeability following PNI, produced by performing a spared nerve injury (SNI). From this longitudinal study, we found that the SNI group had a significant increase in BSCB permeability over time throughout the entire spinal cord. The BSCB opening had a delayed onset and the increase in permeability was transient, returning to control levels just over one day after the surgery. We also examined inter-strain differences in BSCB permeability using five mouse strains (B10, C57BL/6J, CD-1, A/J and BALB/c) that spanned the range of pain hypersensitivity. We found a significant increase in BSCB permeability in the SNI group that was dependent on strain but that did not correlate with the reported strain differences in PNI-induced tactile hypersensitivity. These results were consistent with a previous experiment using Evans Blue dye to independently assess the status of the BSCB permeability. Conclusions DCE-MRI provides a sensitive and non-invasive method to follow BSCB permeability in the same group of mice over time. Examining differences between mouse strains, we demonstrated that there is an important genetically-based control of the PNI-induced increase in BSCB permeability and that the critical genetic determinants of BSCB opening after PNI are distinct from those that determine genetic variability in PNI-induced pain hypersensitivity. Electronic supplementary material The online version of this article (doi:10.1186/1744-8069-10-60) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Lindsay S Cahill
- Mouse Imaging Centre, Hospital for Sick Children, 25 Orde Street, Toronto, Ontario, Canada.
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Byrnes KR, Fricke ST, Faden AI. Neuropathological differences between rats and mice after spinal cord injury. J Magn Reson Imaging 2011; 32:836-46. [PMID: 20882614 DOI: 10.1002/jmri.22323] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
PURPOSE To investigate the utility of noninvasive magnetic resonance imaging (MRI) protocols to demonstrate pathological differences between rats and mice after spinal cord injury (SCI). Rats and mice are commonly used to model SCI; however, histology and immunohistochemistry have shown differences in neuropathology between the two species, including cavity formation and scar/inflammatory responses. MATERIALS AND METHODS Moderate contusion SCI was performed on adult male rats and mice. At 28 days postinjury, animals underwent T1-weighted (T1W), with or without gadolinium contrast, or T2-weighted (T2W) magnetic resonance imaging (MRI), to be compared with histology at the same timepoint. RESULTS In both species, all MRI methods demonstrated changes in spinal cord anatomy. Immunohistochemistry indicated that T2W accurately reflected areas of inflammation and glial scar formation in rats and mice. Quantitation of lesion volume by histology and functional performance correlated best with T2W measurements in both species. Gadolinium contrast accurately reflected the blood-spinal cord-barrier permeability in both species, which appeared greater in rats than in mice. CONCLUSION These data demonstrate that MRI, with either a T1W or T2W protocol, can effectively distinguish pathological differences between rats and mice.
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Affiliation(s)
- Kimberly R Byrnes
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC, USA
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Assessment of gadolinium leakage into traumatic spinal cord lesion using magnet resonance imaging. Spine (Phila Pa 1976) 2010; 35:E1604-9. [PMID: 21116216 DOI: 10.1097/brs.0b013e3181ed2c90] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Exploratory study in patients with acute spinal cord trauma using magnetic resonance imaging (MRI). OBJECTIVE The aim of this study was to assess the leakage of Gd-DTPA into traumatic lesions of the human spinal cord using MRI. SUMMARY OF BACKGROUND DATA While MRI of acute spinal cord trauma is a routine type of clinical investigation, the time course of Gd-DTPA enhancement in traumatic spinal cord injury is not known. METHODS In early stage after spinal cord injury (<24 hours) and at follow-up on day 4, 7, 14, 21, 28, and 84, the accumulation of Gd-DTPA within 30 minutes after bolus injection was investigated in sagittal and axial T2-weighted images and T1-weighted images. RESULTS In 4 men aged between 23 and 55 years with severe paraparesis, the traumatic spinal cord lesion had a maximum of spatial extent after 7 days. Gd-enhancement was first detected on day 4 in T1-weighted images, was most pronounced between day 7 and 28 but absent on day 84. The Gd-enhancement progressively increased in intensity after intravenous injection between 5 and 10 minutes when a maximum was reached, which remained stable for up to 30 minutes. CONCLUSION We used MRI to study the dynamics of post-traumatic Gd-DTPA leakage into the injured spinal cord. This appears as a promising approach for monitoring the local secondary lesion changes.
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Sundberg LM, Herrera JJ, Narayana PA. In vivo longitudinal MRI and behavioral studies in experimental spinal cord injury. J Neurotrauma 2010; 27:1753-67. [PMID: 20649481 DOI: 10.1089/neu.2010.1369] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Comprehensive in vivo longitudinal studies that include multi-modal magnetic resonance imaging (MRI) and a battery of behavioral assays to assess functional outcome were performed at multiple time points up to 56 days post-traumatic spinal cord injury (SCI) in rodents. The MRI studies included high-resolution structural imaging for lesion volumetry, and diffusion tensor imaging (DTI) for probing the white matter integrity. The behavioral assays included open-field locomotion, grid walking, inclined plane, computerized activity box performance, and von Frey filament tests. Additionally, end-point histology was assessed for correlation with both the MRI and behavioral data. The temporal patterns of the lesions were documented on structural MRI. DTI studies showed significant changes in white matter that is proximal to the injury epicenter and persisted to day 56. White matter in regions up to 1 cm away from the injury epicenter that appeared normal on conventional MRI also exhibited changes that were indicative of tissue damage, suggesting that DTI is a more sensitive measure of the evolving injury. Correlations between DTI and histology after SCI could not be firmly established, suggesting that injury causes complex pathological changes in multiple tissue components that affect the DTI measures. Histological evidence confirmed a significant decrease in myelin and oligodendrocyte presence 56 days post-SCI. Multiple assays to evaluate aspects of functional recovery correlated with histology and DTI measures, suggesting that damage to specific white matter tracts can be assessed and tracked longitudinally after SCI.
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Affiliation(s)
- Laura M Sundberg
- Department of Diagnostic and Interventional Imaging, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
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Patel CB, Cohen DM, Ahobila-Vajjula P, Sundberg LM, Chacko T, Narayana PA. Effect of VEGF treatment on the blood-spinal cord barrier permeability in experimental spinal cord injury: dynamic contrast-enhanced magnetic resonance imaging. J Neurotrauma 2010; 26:1005-16. [PMID: 19226205 DOI: 10.1089/neu.2008.0860] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Compromised blood-spinal cord barrier (BSCB) is a factor in the outcome following traumatic spinal cord injury (SCI). Vascular endothelial growth factor (VEGF) is a potent stimulator of angiogenesis and vascular permeability. The role of VEGF in SCI is controversial. Relatively little is known about the spatial and temporal changes in the BSCB permeability following administration of VEGF in experimental SCI. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) studies were performed to noninvasively follow spatial and temporal changes in the BSCB permeability following acute administration of VEGF in experimental SCI over a post-injury period of 56 days. The DCE-MRI data was analyzed using a two-compartment pharmacokinetic model. Animals were assessed for open field locomotion using the Basso-Beattie-Bresnahan score. These studies demonstrate that the BSCB permeability was greater at all time points in the VEGF-treated animals compared to saline controls, most significantly in the epicenter region of injury. Although a significant temporal reduction in the BSCB permeability was observed in the VEGF-treated animals, BSCB permeability remained elevated even during the chronic phase. VEGF treatment resulted in earlier improvement in locomotor ability during the chronic phase of SCI. This study suggests a beneficial role of acutely administered VEGF in hastening neurobehavioral recovery after SCI.
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Affiliation(s)
- Chirag B Patel
- Department of Diagnostic and Interventional Imaging, University of Texas Medical School at Houston, Houston, Texas 77030, USA
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Cohen DM, Patel CB, Ahobila-Vajjula P, Sundberg LM, Chacko T, Liu SJ, Narayana PA. Blood-spinal cord barrier permeability in experimental spinal cord injury: dynamic contrast-enhanced MRI. NMR IN BIOMEDICINE 2009; 22:332-41. [PMID: 19023867 PMCID: PMC2741317 DOI: 10.1002/nbm.1343] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
After a primary traumatic injury, spinal cord tissue undergoes a series of pathobiological changes, including compromised blood-spinal cord barrier (BSCB) integrity. These vascular changes occur over both time and space. In an experimental model of spinal cord injury (SCI), longitudinal dynamic contrast-enhanced MRI (DCE-MRI) studies were performed up to 56 days after SCI to quantify spatial and temporal changes in the BSCB permeability in tissue that did not show any visible enhancement on the post-contrast MRI (non-enhancing tissue). DCE-MRI data were analyzed using a two-compartment pharmacokinetic model. These studies demonstrate gradual restoration of BSCB with post-SCI time. However, on the basis of DCE-MRI, and confirmed by immunohistochemistry, the BSCB remained compromised even at 56 days after SCI. In addition, open-field locomotion was evaluated using the 21-point Basso-Beattie-Bresnahan scale. A significant correlation between decreased BSCB permeability and improved locomotor recovery was observed.
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Scholtes F, Phan-Ba R, Theunissen E, Adriaensens P, Brook G, Franzen R, Bouhy D, Gelan J, Martin D, Schoenen J. Rapid, postmortem 9.4 T MRI of spinal cord injury: correlation with histology and survival times. J Neurosci Methods 2008; 174:157-67. [PMID: 18708093 DOI: 10.1016/j.jneumeth.2008.06.038] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Revised: 06/16/2008] [Accepted: 06/17/2008] [Indexed: 10/21/2022]
Abstract
High field magnetic resonance imaging (MRI) has been increasingly used to assess experimental spinal cord injury (SCI). In the present investigation, after partial spinal cord injury and excision of the whole spine, pathological changes of the spinal cord were studied in spinal cord-spine blocks, from the acute to the chronic state (24 h to 5 months). Using proton density (PD) weighted imaging parameters at a magnetic field strength of 9.4 tesla (T), acquisition times ranging from <1 to 10 h per specimen were used. High in-plane pixel resolution (68 and 38 microm, respectively) was obtained, as well as high signal-to-noise ratio (SNR), which is important for optimal contrast settings. The quality of the resulting MR images was demonstrated by comparison with histology. The cord and the lesion were shown in their anatomical surroundings, detecting cord swelling in the acute phase (24 h to 1 week) and cord atrophy at the chronic stage. Haemorrhage was detected as hypo-intense signal. Oedema, necrosis and scarring were hyper-intense but could not be distinguished. Histology confirmed that the anatomical delimitation of the lesion extent by MRI was precise, both with high and moderate resolution. The present investigation thus demonstrates the precision of spinal cord MRI at different survival delays after compressive partial SCI and establishes efficient imaging parameters for postmortem PD MRI.
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Affiliation(s)
- Felix Scholtes
- Centre for Cellular and Molecular Neurobiology (CNCM), Department of Neuroanatomy, University of Liège, Sart Tilman B36, 4000 Liège, Belgium.
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Mihai G, Nout YS, Tovar CA, Miller BA, Schmalbrock P, Bresnahan JC, Beattie MS. Longitudinal comparison of two severities of unilateral cervical spinal cord injury using magnetic resonance imaging in rats. J Neurotrauma 2008; 25:1-18. [PMID: 18355154 DOI: 10.1089/neu.2007.0338] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Magnetic resonance imaging (MRI) should be a powerful tool for characterization of spinal cord pathology in animal models. We evaluated the utility of medium-field MRI for the longitudinal assessment of progression of spinal cord injury (SCI) in a rat model. Thirteen adult rats were subjected to a 6.25 or 25 g-cm unilateral cervical SCI, and underwent MRI and behavioral tests during a 3-week study period. MRI was also performed post-mortem. Quantification of cord swelling, hypointense and hyperintense signal, and lesion length were the most valuable parameters to determine and were highly correlated to behavioral and histopathological measures. Immediately after injury, MRI showed loss of gray matter-white matter differentiation, presence of scattered hyperintense signal and local hypointense signal, and cord swelling in both groups. At 7 days after injury, the spinal cord in the 25 g-cm group was significantly larger than that of the 6.25 g-cm group (p = 0.02). Contrast enhancement of the lesion was seen at 24 h in the 6.25 g-cm group, and at 24 h and 7 days in the 25 g-cm group. The volume of hypointense signal, representing hemorrhage, throughout the lesion region was significantly larger in the 25 g-cm compared to the 6.25 g-cm group at both 14 and 21 days after SCI (p, </= 0.04). The appearance of the scattered hyperintense signal, initially representing edema, at later time points changed to a rim of hyperintense signal surrounding the lesion cavity. Significant correlations were found between cord swelling at 7 days after SCI, and lesion length and gray and white matter sparing as determined by histopathology. Other parameters that were highly correlated with histopathology were quantity of hyperintense and hypointense signal, and in vivo lesion length. Hypointense signal and in vivo lesion length were highly correlated to behavior. Significant correlation was also found between parameters determined by MRI: swelling, hypointense signal, hyperintense signal, and lesion length. MRI is a valuable imaging modality to assess the temporal evolution of SCI and to distinguish different severities of cervical SCI in rats. In future, MRI could be applied as a screening tool to either administer goal-directed therapies, or enable even group distribution, prior to therapeutic intervention for example through quantification and matching of swelling and edema.
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Affiliation(s)
- Georgeta Mihai
- Department of Radiology, The Ohio State University, Columbus, Ohio, USA
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Abstract
Longitudinal magnetic resonance imaging (MRI) was performed in normal and spinal cord (SC)-injured rodents. A fast technique based on polar B-spline snake was developed to extract the SC contour from the MR images in order to estimate the cord atrophy. Based on pooled data from all of the imaging studies, the extracted contours correlated well with manually defined contours. Results from the injured group showed cord atrophy shortly after the contusion injury. The maximum amount of atrophy (9.7% +/- 3.5% decrease in the cross-sectional area (CSA)) occurred mainly at the epicenter around 14 days postinjury. The caudal and rostral segments in the injured group did not exhibit significant atrophy compared to the normal controls. The MRI-based atrophy measurements obtained in injured cords are consistent with previous histological findings.
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Affiliation(s)
- Xiang Deng
- Department of Diagnostic and Interventional Imaging, University of Texas Medical School at Houston, Houston, Texas, USA
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Furlan JC, Fehlings MG, Massicotte EM, Aarabi B, Vaccaro AR, Bono CM, Madrazo I, Villanueva C, Grauer JN, Mikulis D. A quantitative and reproducible method to assess cord compression and canal stenosis after cervical spine trauma: a study of interrater and intrarater reliability. Spine (Phila Pa 1976) 2007; 32:2083-91. [PMID: 17762809 DOI: 10.1097/brs.0b013e318145a91c] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Reliability study. OBJECTIVE To assess the intrarater and interrater reliability of a recently described technique to measure of maximum canal compromise (MCC) and maximum spinal cord compression (MSCC) using digitized and magnified images in the setting of traumatic cervical spinal cord injury (SCI). SUMMARY OF BACKGROUND DATA The extent of MCC and MSCC is of clinical and prognostic value in the setting of traumatic cervical SCI. However, concerns remain regarding the accuracy of measurements based on hard copy images. We hypothesized that the interrater and intrarater reliability of these assessments would be enhanced using magnified digitized images and software-based measurement tools. METHODS Midsagittal MRI and CT images of cervical spine were selected from 5 individuals with acute traumatic cervical SCI. Measurements of MCC using CT scan and T1-weighted MRI and measurements of MSCC based on T2-weighted MR images were independently estimated by 13 raters on 10 occasions. RESULTS The intrarater reliability for CT-MCC, T1-weighted MRI-MCC and T2-weighted MRI-MSCC was high in the 10 rounds in each patient. In addition, the mean intrarater interclass correlation coefficient was 0.72 +/- 0.05 for the CT-MCC, 0.70 +/- 0.07 for the T1-weighted MRI-MCC, and 0.68 +/- 0.11 for the T2-weighted MRI-MSCC. The mean interrater interclass correlation coefficients were 0.43 +/- 0.02 for the CT-MCC, 0.61 +/- 0.03 for the T1-weighted MRI-MCC, and 0.55 +/- 0.05 for the evaluation of T2-weighted MRI-MSCC. CONCLUSION Our study has demonstrated that the intrarater reliability for the instrument to assess MCC and MSCC in the setting of traumatic SCI was high. The interrater ICCs at a moderate level of reliability combined with our results using analysis of variance with post hoc tests indicate that the measurements of MCC and MSCC are reproducible, which supports the use of these radiologic parameters in the clinical and research settings.
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Affiliation(s)
- Julio C Furlan
- Spinal Program, Krembil Neuroscience Centre, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada
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Fehlings MG, Furlan JC, Massicotte EM, Arnold P, Aarabi B, Harrop J, Anderson DG, Bono CM, Dvorak M, Fisher C, France J, Hedlund R, Madrazo I, Nockels R, Rampersaud R, Rechtine G, Vaccaro AR. Interobserver and intraobserver reliability of maximum canal compromise and spinal cord compression for evaluation of acute traumatic cervical spinal cord injury. Spine (Phila Pa 1976) 2006; 31:1719-25. [PMID: 16816769 DOI: 10.1097/01.brs.0000224164.43912.e6] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Prospective, blinded validation study of an objective, quantitative measure to assess maximum canal compromise (MCC) and maximum spinal cord compression (MSCC) in individuals with acute cervical spinal cord injury (SCI). OBJECTIVE To examine the intraobserver and interobserver reliability of MCC and MSCC in individuals with acute traumatic cervical SCI. SUMMARY OF BACKGROUND DATA To date, few quantitative reliable radiologic methods for assessing the extent of spinal cord compression in the setting of acute SCI have been reported. MCC and MSCC, as assessed on mid-sagittal CT and T2-weighted MR images, respectively, appear to have potential clinical and prognostic value. To date, the validation of these assessment tools has been limited to a small number of observers at a single institution. However, to date no study has focused on the reliability of these radiologic parameters among a large cohort of spine surgeons from North America and abroad. This type of validation is critical to allow the broader use of these outcome measures in research studies and in clinical practice. METHODS Mid-sagittal MRI and CT images of cervical spine were selected from 10 individuals with acute traumatic cervical SCI. A total of 28 spine surgeons independently estimated CT MCC, T1-weighted MRI MCC, and T2-weighted MRI MSCC on two occasions using a calibrated ruler. In the first round of measurements, the observers estimated the radiologic parameters using only written instructions. The second measurement set was obtained after an interactive teaching session on the methodology. The order of the images was altered for the second set of measurements. RESULTS Analysis using parametric and nonparametric statistics indicated high intraobserver reliability for CT MCC, T1-weighted MRI MCC, and T2-weighted MSCC with interclass correlation coefficients (ICCs) of 0.92, 0.95, and 0.97, respectively. The interobserver reliability for all three radiologic parameters was considered moderate with ICCs ranging from 0.35 to 0.56. CONCLUSION Our results indicate that the intraobserver reliability for the MCC and MSCC was high. Although the interobserver reliability for all three radiologic parameters in the present study was below 0.75, the observed differences were small and largely accounted for by the limitations in the precision of the calibrated ruler. For cases with minimal cord compression, the measurement of canal stenosis (MCC) proved more accurate. In contrast, in cases with severe cord compression, the assessment of MSCC was more accurate. It is anticipated that the use of digital imaging technologies will further enhance the precision of these outcome measures.
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Affiliation(s)
- Michael G Fehlings
- Department of Surgery, Division of Neurosurgery, University of Toronto, Toronto, Canada.
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Li YQ, Chen P, Jain V, Reilly RM, Wong CS. Early Radiation-Induced Endothelial Cell Loss and Blood–Spinal Cord Barrier Breakdown in the Rat Spinal Cord. Radiat Res 2004; 161:143-52. [PMID: 14731076 DOI: 10.1667/rr3117] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Using a rat spinal cord model, this study was designed to characterize radiation-induced vascular endothelial cell loss and its relationship to early blood-brain barrier disruption in the central nervous system. Adult rats were given a single dose of 0, 2, 8, 19.5, 22, 30 or 50 Gy to the cervical spinal cord. At various times up to 2 weeks after irradiation, the spinal cord was processed for histological and immunohistochemical analysis. Radiation-induced apoptosis was assessed by morphology and TdT-mediated dUTP nick end labeling combined with immunohistochemical markers for endothelial and glial cells. Image analysis was performed to determine endothelial cell and microvessel density using immunohistochemistry with endothelial markers, namely endothelial barrier antigen, glucose transporter isoform 1, laminin and zonula occludens 1. Blood-spinal cord barrier permeability was assessed using immunohistochemistry for albumin and (99m)Tc-diethylenetriamine pentaacetic acid as a vascular tracer. Endothelial cell proliferation was assessed using in vivo BrdU labeling. During the first 24 h after irradiation, apoptotic endothelial cells were observed in the rat spinal cord. The decrease in endothelial cell density at 24 h after irradiation was associated with an increase in albumin immunostaining around microvessels. The decrease in the number of endothelial cells persisted for 7 days and recovery of endothelial density was apparent by day 14. A similar pattern of blood-spinal cord barrier disruption and recovery of permeability was observed over the 2 weeks, and an increase in BrdU-labeled endothelial cells was seen at day 3. These results are consistent with an association between endothelial cell death and acute blood-spinal cord barrier disruption in the rat spinal cord after irradiation.
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Affiliation(s)
- Yu-Qing Li
- Department of Radiation Oncology, Sunnybrook and Women's College Health Sciences Center, University of Toronto, Toronto, Ontario M4N 3M5, Canada
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Chadi G, Andrade MS, Leme RJ, Gomide VC. Experimental models of partial lesion of rat spinal cord to investigate neurodegeneration, glial activation, and behavior impairments. Int J Neurosci 2002; 111:137-65. [PMID: 11912671 DOI: 10.3109/00207450108994227] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The article demonstrates two experimental models of spinal cord partial injury in rats: a contuse model promoted by the NYU impactor system and a partial hemitransection model achieved by a stereotaxic-positioned adjustable wire knife. By means of a defined impact weight (10 g) and a digital optical potentiometer linked to a computer, the impactor transferred and registered a moderate or a severe contusion to the rat spinal cord at a low thoracic level after dropping the weight from distances of 25 mm and 50 mm, respectively, to the dorsal surface of the exposed dura spinal cord. Impact curve was calculated and the parameters of the trauma, like impact velocity, cord compression distance and cord compression rates were obtained in order to demonstrate trauma severity. To promote partial hemitransection, rats were positioned in a spinal cord unit of a stereotaxic apparatus and lesion was made with the adjustable wire knife spatially oriented. By means of a computerized infrared motion sensor-home cage activity monitor and a noncomputerized evaluation of motor behavior using the inclined plane and the motor score of Tarlov tests, behavior was analyzed in an acute period postlesion. Rats were sacrificed and spinal cords were processed for routine staining to show neurons and for GFAP and OX42 immunohistochemistry to demonstrate glial cells. The tissue labelings were quantified using computer assisted stereology by means of an optical disector and microdensitometric image analysis by means of quantification of gray values of discriminated profiles. While partial hemitransection model favored a more accurate control of the lesion location, the contuse model allowed us to perform different degrees of lesion severity. A close correlation between behavioral impairment and severity of trauma was seen in the rats submitted to spinal cord contusion. The stereologic lesion index showed a correlation between severity of trauma and tissue damage by 7 days and demonstrated a time-dependent secondary degeneration after moderate but not after severe spinal cord contusion from 7 to 30 days after injury. Long-lasting activations of astrocytes and microglia seen by persisted increases in the specific mean gray values of immunoreactivities were also found in all levels of the white and gray matters of the partial hemitransected spinal cord until 3 months postinjury which can be related to wound/repair events and paracrine trophic support to spinal cord remaining neurons. The results showed that controlled partial lesions may provide an important toll to study trophism and plasticity in the spinal cord.
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Affiliation(s)
- G Chadi
- Laboratory of Neuroregeneration, Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
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Bilgen M, Abbe R, Narayana PA. Dynamic contrast-enhanced MRI of experimental spinal cord injury: in vivo serial studies. Magn Reson Med 2001; 45:614-22. [PMID: 11283989 DOI: 10.1002/mrm.1083] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The progression of experimental spinal cord injury (SCI) was followed with in vivo dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and neurobehavioral studies on postinjury days 0, 2, 4, 7, 10, 14, 17, 21, 28, 35, and 42. Gadopentate dimeglumine (Gd) was administered IV and postcontrast, T(1)-weighted, axial images were acquired repetitively for up to 60 min. Images were analyzed to determine the spatial and temporal evolution of the intensity enhancement. A statistical decision mechanism was developed to objectively detect the enhancement. Strong and rapid enhancement was observed at the epicenter of injury, indicating a significant compromise in blood spinal cord barrier. The enhanced regions in each slice were combined to estimate the area and volume of the lesion. On the day of injury, around 85% of the total cord area at the epicenter showed enhancement within the first 15 min of Gd administration. At the same time, the enhanced volumes attained nearly 40% of the total cord volume and extended axially over 8 mm along the cord. These quantities decreased steadily with time, with a concomitant improvement in the motor functions. The volume of enhancement correlated highly with the neurobehavioral tests (r = -0.87). DCE-MRIs revealed small hyperintense regions distributed inside white matter about two weeks postinjury. Based on histology, these enhancements appear to represent new vessels with "leaky endothelium." Magn Reson Med 45:614-622, 2001.
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Affiliation(s)
- M Bilgen
- Department of Radiology, University of Texas at Houston Medical School, Houston, Texas 77030, USA.
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Abstract
Magnetization transfer (MT) imaging techniques were implemented to study a clip compression model of spinal cord injury (SCI) in the rat. The purpose of this study was to determine if the magnetization transfer ratio (MTR) could be used to classify the stage and severity of SCI. Two clip compression injuries were studied: mild SCI and severe SCI. MTRs were determined for gray matter (GM) and white matter (WM) regions and the GM-WM contrast was determined on days 1 and 7 following surgery. Despite differences in pathologic features of mild and severe SCI, the GM-WM contrast did not allow discrimination between the two degrees of severity of SCI. WM MTR allowed differentiation of mild and severe SCI on day 1. These preliminary results suggest that WM MTR may provide an indication of the severity of injury in SCI. Magn Reson Med 45:159-163, 2001.
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Affiliation(s)
- P J Gareau
- Imaging Research Laboratories, The John P. Robarts Research Institute, London, Ontario, Canada
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Abstract
AbstractTraumatic spinal cord injury results in the disruption of neural and vascular structures (primary injury) and is characterized by an evolution of secondary pathogenic events that collectively define the extent of functional recovery. This article reviews the vascular responses to spinal cord injury, focusing on both early and delayed events, including intraparenchymal hemorrhage, inflammation, disruption of the blood-spinal cord barrier, and angiogenesis. These vascular-related events not only influence the evolution of secondary tissue damage but also define an environment that fosters neural plasticity in the chronically injured spinal cord.
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Bilgen M, Abbe R, Liu SJ, Narayana PA. Spatial and temporal evolution of hemorrhage in the hyperacute phase of experimental spinal cord injury: in vivo magnetic resonance imaging. Magn Reson Med 2000; 43:594-600. [PMID: 10748436 DOI: 10.1002/(sici)1522-2594(200004)43:4<594::aid-mrm15>3.0.co;2-1] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
To follow the spatial and temporal evolution of hemorrhage, in vivo MRI studies of experimental spinal cord injury (SCI) were performed on 17 rats in the very acute phase (hyperacute), starting as early as 9 min and continued up to 400 min posttrauma. Axial MR images were processed slice by slice over a 21 mm length around the epicenter of the injury. The data were analyzed statistically and fitted to an empirically derived function to characterize the spatial and temporal evolution of hemorrhage. The results indicated that 1) the initial hemorrhage in the very early phase of the injury area covered 12.5% of the total cord area and subsequently increased with a time constant of 700 min, 2) a major portion of the hemorrhage was concentrated spatially within the 4 mm distance from the epicenter, 3) the volume of hemorrhage normalized to its initial value increased linearly at a rate of approximately 0.0015 min(-1), and 4) edema was observed at the gray- and white-matter junction as early as 12 min postinjury. In general, edema appeared to be focal and scattered in this phase of the injury, which made its quantification unreliable on MRI.
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Affiliation(s)
- M Bilgen
- Department of Radiology, University of Texas at Houston Medical School, Houston, Texas 77030, USA
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Metz GA, Curt A, van de Meent H, Klusman I, Schwab ME, Dietz V. Validation of the weight-drop contusion model in rats: a comparative study of human spinal cord injury. J Neurotrauma 2000; 17:1-17. [PMID: 10674754 DOI: 10.1089/neu.2000.17.1] [Citation(s) in RCA: 235] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Animal models are widely used for studying the pathophysiology as well as treatment strategies for injuries of the central nervous system. However, it is still unclear in how far the rat model of spinal cord injury (SCI) is valid for human SCI. Therefore, comparisons were made among functional, electrophysiological, and morphological outcome parameters following SCI in rats and humans. Contusion of the mid-thoracic spinal cord in 27 adult rats was induced by a weight-drop, leading to severe deficits in open field locomotion at a chronic stage. The data of 85 human patients with chronic SCI were collected and compared with the rat data. In electrophysiological recordings, prolonged latencies and reduced amplitudes in both motor evoked potentials (MEP) and somatosensory evoked potentials (SSEP) were closely correlated to the impairment of locomotor capacity of lower limbs in rats and humans. The morphological parameters assessed by high-resolution magnetic resonance imaging (MRI) in both species indicated that the lesion length and spinal cord atrophy were significantly related to the electrophysiological and functional outcome parameters. In rats, histological analysis was performed and showed, in addition to the MRI, a close relationship between spared white matter and locomotor capacity. Our results suggest an analogous relationship in rats and humans with respect to functional, electrophysiological, and morphological outcomes. Thus, the techniques for evaluating the extent and severity of SCI in humans and rats are of comparable value. This indicates that the rat can serve as an adequate animal model for research on functional and morphological changes after SCI and the effects of new treatment strategies.
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Affiliation(s)
- G A Metz
- Brain Research Institute, University and Swiss Federal Institute of Technology, Zurich, Switzerland
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