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Wei W, Huang Y, Li D, Gou HF, Wang W. Improved therapeutic potential of MSCs by genetic modification. Gene Ther 2018; 25:538-547. [PMID: 30254305 DOI: 10.1038/s41434-018-0041-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 07/30/2018] [Accepted: 09/06/2018] [Indexed: 02/05/2023]
Abstract
Mesenchymal stem cells (MSCs), well-studied adult stem cells in various tissues, possess multi-lineage differentiation potential and anti-inflammatory properties. MSCs have been approved to regenerate lineage-specific cells to replace injured cells in tissues. MSCs are approved to treat inflammatory diseases. With the discovery of genes important for the repair of damaged tissues, MSCs genetically modified by such genes hold improved therapeutic potential. In this review, we summarised the uses of genetically modified MSCs to treat different diseases, including bone diseases, cardiovascular diseases, autoimmune diseases, central nervous system disorders, and cancer. To better understand the exact role of genetically modified MSCs, key mechanisms determining, which genes are selected to be used for modifying MSCs and improvements in post-genetic modification are discussed. Therapeutic benefits enhanced by genetic modifications are to be documented by further clinical studies.
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Affiliation(s)
- Wei Wei
- Department of Emergency, West China Hospital, Sichuan University and Collaborative Innovation Center for Biotherapy, Chengdu, China
| | - Yong Huang
- Department of Emergency, West China Hospital, Sichuan University and Collaborative Innovation Center for Biotherapy, Chengdu, China.,Department of Medical Oncology, Cancer Center, West China Hospital, West China Medical School, Sichuan University and Collaborative Innovation Center for Biotherapy, Chengdu, China
| | - Dan Li
- Department of Emergency, West China Hospital, Sichuan University and Collaborative Innovation Center for Biotherapy, Chengdu, China.,Department of Medical Oncology, Cancer Center, West China Hospital, West China Medical School, Sichuan University and Collaborative Innovation Center for Biotherapy, Chengdu, China
| | - Hong-Feng Gou
- Department of Medical Oncology, Cancer Center, West China Hospital, West China Medical School, Sichuan University and Collaborative Innovation Center for Biotherapy, Chengdu, China
| | - Wei Wang
- Department of Emergency, West China Hospital, Sichuan University and Collaborative Innovation Center for Biotherapy, Chengdu, China. .,Department of Medical Oncology, Cancer Center, West China Hospital, West China Medical School, Sichuan University and Collaborative Innovation Center for Biotherapy, Chengdu, China.
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2
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Patil N, Truong V, Holmberg MH, Lavoie NS, McCoy MR, Dutton JR, Holmberg EG, Parr AM. Safety and Efficacy of Rose Bengal Derivatives for Glial Scar Ablation in Chronic Spinal Cord Injury. J Neurotrauma 2018; 35:1745-1754. [PMID: 29373946 PMCID: PMC6033306 DOI: 10.1089/neu.2017.5398] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
There are no effective therapies available currently to ameliorate loss of function for patients with spinal cord injuries (SCIs). In addition, proposed treatments that demonstrated functional recovery in animal models of acute SCI have failed almost invariably when applied to chronic injury models. Glial scar formation in chronic injury is a likely contributor to limitation on regeneration. We have removed existing scar tissue in chronically contused rat spinal cord using a rose Bengal-based photo ablation approach. In this study, we compared two chemically modified rose bengal derivatives to unmodified rose bengal, both confirming and expanding on our previously published report. Rats were treated with unmodified rose bengal (RB1) or rose bengal modified with hydrocarbon (RB2) or polyethylene glycol (RB3), to determine the effects on scar components and spared tissue post-treatment. Our results showed that RB1 was more efficacious than RB2, while still maintaining minimal collateral effects on spared tissue. RB3 was not taken up by the cells, likely because of its size, and therefore had no effect. Treatment with RB1 also resulted in an increase in serotonin eight days post-treatment in chronically injured spinal cords. Thus, we suggest that unmodified rose Bengal is a potent candidate agent for the development of a therapeutic strategy for scar ablation in chronic SCI.
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Affiliation(s)
- Nandadevi Patil
- Department of Neurosurgery, Stem Cell Institute, University of Minnesota, Minneapolis, Minnesota
| | - Vincent Truong
- Department of Neurosurgery, Stem Cell Institute, University of Minnesota, Minneapolis, Minnesota
| | - Mackenzie H. Holmberg
- Department of Chemistry, University of Alaska Anchorage, Anchorage, Alaska
- University of Washington School of Medicine, Seattle, Washington
| | - Nicolas S. Lavoie
- Department of Neurosurgery, Stem Cell Institute, University of Minnesota, Minneapolis, Minnesota
| | - Mark R. McCoy
- Department of Chemistry, University of Alaska Anchorage, Anchorage, Alaska
| | - James R. Dutton
- Department of Genetics, Cell Biology and Development, Stem Cell Institute, University of Minnesota, Minneapolis, Minnesota
| | - Eric G. Holmberg
- Department of Chemistry, University of Alaska Anchorage, Anchorage, Alaska
| | - Ann M. Parr
- Department of Neurosurgery, Stem Cell Institute, University of Minnesota, Minneapolis, Minnesota
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Jung SY, Seo TB, Kim DY. Treadmill exercise facilitates recovery of locomotor function through axonal regeneration following spinal cord injury in rats. J Exerc Rehabil 2016; 12:284-92. [PMID: 27656624 PMCID: PMC5031384 DOI: 10.12965/jer.1632698.349] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 07/31/2016] [Indexed: 11/29/2022] Open
Abstract
Spinal cord injury (SCI) disrupts both axonal pathways and segmental spinal cord circuity, resulting in permanent neurological deficits. Physical exercise is known to increase the expression of neurotrophins for improving the injured spinal cord. In the present study, we investigated the effects of treadmill exercise on locomotor function in relation with brain-derived neurotrophic factor (BDNF) expression after SCI. The rats were divided into five groups: control group, sham operation group, sham operation and exercise group, SCI group, and SCI and exercise group. The laminectomy was performed at the T9–T10 level. The exposed dorsal surface of the spinal cord received contusion injury (10 g × 25 mm) using the impactor. Treadmill exercise was performed 6 days per a week for 6 weeks. In order to evaluate the locomotor function of animals, Basso-Beattie-Bresnahan (BBB) locomotor scale was conducted once a week for 6 weeks. We examined BDNF expression and axonal sprouting in the injury site of the spinal cord using Western blot analysis and immunofluorescence staining. SCI induced loss of locomotor function with decreased BDNF expression in the injury site. Treadmill exercise increased the score of BBB locomotor scale and reduced cavity formation in the injury site. BDNF expression and axonal sprouting within the trabecula were further facilitated by treadmill exercise in SCI-exposed rats. The present study provides the evidence that treadmill exercise may facilitate recovery of locomotor function through axonal regeneration via BDNF expression following SCI.
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Affiliation(s)
- Sun-Young Jung
- Department of Physical Therapy, Hosan University, Gyeongsan, Korea
| | - Tae-Beom Seo
- Division of Sports Science and Engineering, Korea Institute of Sports Science, Seoul, Korea
| | - Dae-Young Kim
- Department of Sports Health Care, College of Humanities & Social Sciences, Inje University, Gimhae, Korea
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Zeng X, Ma YH, Chen YF, Qiu XC, Wu JL, Ling EA, Zeng YS. Autocrine fibronectin from differentiating mesenchymal stem cells induces the neurite elongation in vitro and promotes nerve fiber regeneration in transected spinal cord injury. J Biomed Mater Res A 2016; 104:1902-11. [PMID: 26991461 PMCID: PMC5101622 DOI: 10.1002/jbm.a.35720] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2015] [Revised: 03/02/2016] [Accepted: 03/11/2016] [Indexed: 01/08/2023]
Abstract
Extracellular matrix (ECM) expression is temporally and spatially regulated during the development of stem cells. We reported previously that fibronectin (FN) secreted by bone marrow mesenchymal stem cells (MSCs) was deposited on the surface of gelatin sponge (GS) soon after culture. In this study, we aimed to assess the function of accumulated FN on neuronal differentiating MSCs as induced by Schwann cells (SCs) in three dimensional transwell co‐culture system. The expression pattern and amount of FN of differentiating MSCs was examined by immunofluorescence, Western blot and immunoelectron microscopy. The results showed that FN accumulated inside GS scaffold, although its mRNA expression in MSCs was progressively decreased during neural induction. MSC‐derived neuron‐like cells showed spindle‐shaped cell body and long extending processes on FN‐decorated scaffold surface. However, after blocking of FN function by application of monoclonal antibodies, neuron‐like cells showed flattened cell body with short and thick neurites, together with decreased expression of integrin β1. In vivo transplantation study revealed that autocrine FN significantly facilitated endogenous nerve fiber regeneration in spinal cord transection model. Taken together, the present results showed that FN secreted by MSCs in the early stage accumulated on the GS scaffold and promoted the neurite elongation of neuronal differentiating MSCs as well as nerve fiber regeneration after spinal cord injury. This suggests that autocrine FN has a dynamic influence on MSCs in a three dimensional culture system and its potential application for treatment of traumatic spinal cord injury. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1902–1911, 2016.
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Affiliation(s)
- Xiang Zeng
- Key Laboratory for Stem Cells and Tissue Engineering, Sun Yat-sen University, Ministry of Education, Guangzhou, 510080, China
| | - Yuan-Huan Ma
- Key Laboratory for Stem Cells and Tissue Engineering, Sun Yat-sen University, Ministry of Education, Guangzhou, 510080, China
- Department of Histology and Embryology, Guangdong Medical University, Zhanjiang, 524023, China
| | - Yuan-Feng Chen
- Department of Histology and Embryology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China
| | - Xue-Cheng Qiu
- Key Laboratory for Stem Cells and Tissue Engineering, Sun Yat-sen University, Ministry of Education, Guangzhou, 510080, China
| | - Jin-Lang Wu
- Department of Electron Microscope, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China
| | - Eng-Ang Ling
- Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117597, Singapore
| | - Yuan-Shan Zeng
- Key Laboratory for Stem Cells and Tissue Engineering, Sun Yat-sen University, Ministry of Education, Guangzhou, 510080, China
- Department of Histology and Embryology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China
- Institute of Spinal Cord Injury, Sun Yat-sen University, Guangzhou, 510120, China
- Co-innovation Center of Neuroregeneration, Jiangsu, 226019, China
- Guangdong Provincial Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China
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Vilariño-Feltrer G, Martínez-Ramos C, Monleón-de-la-Fuente A, Vallés-Lluch A, Moratal D, Barcia Albacar JA, Monleón Pradas M. Schwann-cell cylinders grown inside hyaluronic-acid tubular scaffolds with gradient porosity. Acta Biomater 2016; 30:199-211. [PMID: 26518102 DOI: 10.1016/j.actbio.2015.10.040] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 10/21/2015] [Accepted: 10/26/2015] [Indexed: 11/19/2022]
Abstract
Cell transplantation therapies in the nervous system are frequently hampered by glial scarring and cell drain from the damaged site, among others. To improve this situation, new biomaterials may be of help. Here, novel single-channel tubular conduits based on hyaluronic acid (HA) with and without poly-l-lactide acid fibers in their lumen were fabricated. Rat Schwann cells were seeded within the conduits and cultured for 10days. The conduits possessed a three-layered porous structure that impeded the leakage of the cells seeded in their interior and made them impervious to cell invasion from the exterior, while allowing free transport of nutrients and other molecules needed for cell survival. The channel's surface acted as a template for the formation of a cylindrical sheath-like tapestry of Schwann cells continuously spanning the whole length of the lumen. Schwann-cell tubes having a diameter of around 0.5mm and variable lengths can thus be generated. This structure is not found in nature and represents a truly engineered tissue, the outcome of the specific cell-material interactions. The conduits might be useful to sustain and protect cells for transplantation, and the biohybrids here described, together with neuronal precursors, might be of help in building bridges across significant distances in the central and peripheral nervous system. STATEMENT OF SIGNIFICANCE The paper entitled "Schwann-cell cylinders grown inside hyaluronic-acid tubular scaffolds with gradient porosity" reports on the development of a novel tubular scaffold and on how this scaffold acts on Schwann cells seeded in its interior as a template to produce macroscopic hollow continuous cylinders of tightly joined Schwann cells. This cellular structure is not found in nature and represents a truly engineered novel tissue, which obtains as a consequence of the specific cell-material interactions within the scaffold.
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Affiliation(s)
- G Vilariño-Feltrer
- Center for Biomaterials and Tissue Engineering, Universitat Politècnica de València, Cno. de Vera s/n, 46022 Valencia, Spain
| | - C Martínez-Ramos
- Center for Biomaterials and Tissue Engineering, Universitat Politècnica de València, Cno. de Vera s/n, 46022 Valencia, Spain
| | - A Monleón-de-la-Fuente
- Center for Biomaterials and Tissue Engineering, Universitat Politècnica de València, Cno. de Vera s/n, 46022 Valencia, Spain
| | - A Vallés-Lluch
- Center for Biomaterials and Tissue Engineering, Universitat Politècnica de València, Cno. de Vera s/n, 46022 Valencia, Spain
| | - D Moratal
- Center for Biomaterials and Tissue Engineering, Universitat Politècnica de València, Cno. de Vera s/n, 46022 Valencia, Spain
| | - J A Barcia Albacar
- Servicio de Neurocirugía, Hospital Clínico San Carlos, Instituto de Investigación Sanitaria San Carlos (IdISSC), C/ Profesor Martín Lagos, S/N, Madrid 28040, Spain
| | - M Monleón Pradas
- Center for Biomaterials and Tissue Engineering, Universitat Politècnica de València, Cno. de Vera s/n, 46022 Valencia, Spain.
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Integration of donor mesenchymal stem cell-derived neuron-like cells into host neural network after rat spinal cord transection. Biomaterials 2015; 53:184-201. [DOI: 10.1016/j.biomaterials.2015.02.073] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 02/08/2015] [Accepted: 02/15/2015] [Indexed: 12/27/2022]
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Qiu XC, Jin H, Zhang RY, Ding Y, Zeng X, Lai BQ, Ling EA, Wu JL, Zeng YS. Donor mesenchymal stem cell-derived neural-like cells transdifferentiate into myelin-forming cells and promote axon regeneration in rat spinal cord transection. Stem Cell Res Ther 2015; 6:105. [PMID: 26012641 PMCID: PMC4482203 DOI: 10.1186/s13287-015-0100-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 05/18/2015] [Indexed: 12/21/2022] Open
Abstract
Introduction Severe spinal cord injury often causes temporary or permanent damages in strength, sensation, or autonomic functions below the site of the injury. So far, there is still no effective treatment for spinal cord injury. Mesenchymal stem cells (MSCs) have been used to repair injured spinal cord as an effective strategy. However, the low neural differentiation frequency of MSCs has limited its application. The present study attempted to explore whether the grafted MSC-derived neural-like cells in a gelatin sponge (GS) scaffold could maintain neural features or transdifferentiate into myelin-forming cells in the transected spinal cord. Methods We constructed an engineered tissue by co-seeding of MSCs with genetically enhanced expression of neurotrophin-3 (NT-3) and its high-affinity receptor tropomyosin receptor kinase C (TrkC) separately into a three-dimensional GS scaffold to promote the MSCs differentiating into neural-like cells and transplanted it into the gap of a completely transected rat spinal cord. The rats received extensive post-operation care, including cyclosporin A administrated once daily for 2 months. Results MSCs modified genetically could differentiate into neural-like cells in the MN + MT (NT-3-MSCs + TrKC-MSCs) group 14 days after culture in the GS scaffold. However, after the MSC-derived neural-like cells were transplanted into the injury site of spinal cord, some of them appeared to lose the neural phenotypes and instead transdifferentiated into myelin-forming cells at 8 weeks. In the latter, the MSC-derived myelin-forming cells established myelin sheaths associated with the host regenerating axons. And the injured host neurons were rescued, and axon regeneration was induced by grafted MSCs modified genetically. In addition, the cortical motor evoked potential and hindlimb locomotion were significantly ameliorated in the rat spinal cord transected in the MN + MT group compared with the GS and MSC groups. Conclusion Grafted MSC-derived neural-like cells in the GS scaffold can transdifferentiate into myelin-forming cells in the completely transected rat spinal cord. Electronic supplementary material The online version of this article (doi:10.1186/s13287-015-0100-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Xue-Cheng Qiu
- Key Laboratory for Stem Cells and Tissue Engineering (Sun Yat-sen University), Ministry of Education, Guangzhou, 510080, China.
| | - Hui Jin
- Key Laboratory for Stem Cells and Tissue Engineering (Sun Yat-sen University), Ministry of Education, Guangzhou, 510080, China.
| | - Rong-Yi Zhang
- Department of Histology and Embryology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China.
| | - Ying Ding
- Department of Histology and Embryology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China.
| | - Xiang Zeng
- Key Laboratory for Stem Cells and Tissue Engineering (Sun Yat-sen University), Ministry of Education, Guangzhou, 510080, China.
| | - Bi-Qin Lai
- Department of Histology and Embryology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China.
| | - Eng-Ang Ling
- Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117597, Singapore.
| | - Jin-Lang Wu
- Department of Electron Microscope, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China.
| | - Yuan-Shan Zeng
- Key Laboratory for Stem Cells and Tissue Engineering (Sun Yat-sen University), Ministry of Education, Guangzhou, 510080, China. .,Department of Histology and Embryology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China. .,Institute of Spinal Cord Injury, Sun Yat-sen University, Guangzhou, 510120, China. .,Co-innovation Center of Neuroregeneration, Nantong University, Nantong, 226001, China.
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Zhang SX, Huang F, Gates M, Holmberg EG. Role of endogenous Schwann cells in tissue repair after spinal cord injury. Neural Regen Res 2014; 8:177-85. [PMID: 25206489 PMCID: PMC4107512 DOI: 10.3969/j.issn.1673-5374.2013.02.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 12/25/2012] [Indexed: 01/09/2023] Open
Abstract
Schwann cells are glial cells of peripheral nervous system, responsible for axonal myelination and ensheathing, as well as tissue repair following a peripheral nervous system injury. They are one of several cell types that are widely studied and most commonly used for cell transplantation to treat spinal cord injury, due to their intrinsic characteristics including the ability to secrete a variety of neurotrophic factors. This mini review summarizes the recent findings of endogenous Schwann cells after spinal cord injury and discusses their role in tissue repair and axonal regeneration. After spinal cord injury, numerous endogenous Schwann cells migrate into the lesion site from the nerve roots, involving in the construction of newly formed repaired tissue and axonal myelination. These invading Schwann cells also can move a long distance away from the injury site both rostrally and caudally. In addition, Schwann cells can be induced to migrate by minimal insults (such as scar ablation) within the spinal cord and integrate with astrocytes under certain circumstances. More importantly, the host Schwann cells can be induced to migrate into spinal cord by transplantation of different cell types, such as exogenous Schwann cells, olfactory ensheathing cells, and bone marrow-derived stromal stem cells. Migration of endogenous Schwann cells following spinal cord injury is a common natural phenomenon found both in animal and human, and the myelination by Schwann cells has been examined effective in signal conduction electrophysiologically. Therefore, if the inherent properties of endogenous Schwann cells could be developed and utilized, it would offer a new avenue for the restoration of injured spinal cord.
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Affiliation(s)
- Shu-Xin Zhang
- Spinal Cord Society Research Center, Fort Collins, CO 80526, USA
| | - Fengfa Huang
- Spinal Cord Society Research Center, Fort Collins, CO 80526, USA
| | - Mary Gates
- Spinal Cord Society Research Center, Fort Collins, CO 80526, USA
| | - Eric G Holmberg
- Spinal Cord Society Research Center, Fort Collins, CO 80526, USA ; Department of Chemistry University of Alaska, Anchorage, AK 99508, USA
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Immunological demyelination triggers macrophage/microglial cells activation without inducing astrogliosis. Clin Dev Immunol 2013; 2013:812456. [PMID: 24319469 PMCID: PMC3844255 DOI: 10.1155/2013/812456] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 09/16/2013] [Accepted: 09/24/2013] [Indexed: 12/18/2022]
Abstract
The glial scar formed by reactive astrocytes and axon growth inhibitors associated with myelin play important roles in the failure of axonal regeneration following central nervous system (CNS) injury. Our laboratory has previously demonstrated that immunological demyelination of the CNS facilitates regeneration of severed axons following spinal cord injury. In the present study, we evaluate whether immunological demyelination is accompanied with astrogliosis. We compared the astrogliosis and macrophage/microglial cell responses 7 days after either immunological demyelination or a stab injury to the dorsal funiculus. Both lesions induced a strong activated macrophage/microglial cells response which was significantly higher within regions of immunological demyelination. However, immunological demyelination regions were not accompanied by astrogliosis compared to stab injury that induced astrogliosis which extended several millimeters above and below the lesions, evidenced by astroglial hypertrophy, formation of a glial scar, and upregulation of intermediate filaments glial fibrillary acidic protein (GFAP). Moreover, a stab or a hemisection lesion directly within immunological demyelination regions did not induced astrogliosis within the immunological demyelination region. These results suggest that immunological demyelination creates a unique environment in which astrocytes do not form a glial scar and provides a unique model to understand the putative interaction between astrocytes and activated macrophage/microglial cells.
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Feng S, Zhuang M, Wu R. Secretion of nerve growth factor, brain-derived neurotrophic factor, and glial cell-line derived neurotrophic factor in co-culture of four cell types in cerebrospinal fluid-containing medium. Neural Regen Res 2012; 7:2907-14. [PMID: 25317143 PMCID: PMC4190949 DOI: 10.3969/j.issn.1673-5374.2012.36.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 08/22/2012] [Indexed: 02/05/2023] Open
Abstract
The present study co-cultured human embryonic olfactory ensheathing cells, human Schwann cells, human amniotic epithelial cells and human vascular endothelial cells in complete culture medium-containing cerebrospinal fluid. Enzyme linked immunosorbent assay was used to detect nerve growth factor, brain-derived neurotrophic factor, and glial cell line-derived neurotrophic factor secretion in the supernatant of co-cultured cells. Results showed that the number of all cell types reached a peak at 7-10 days, and the expression of nerve growth factor, brain-derived neurotrophic factor, and glial cell line-derived neurotrophic factor peaked at 9 days. Levels of secreted nerve growth factor were four-fold higher than brain-derived neurotrophic factor, which was three-fold higher than glial cell line-derived neurotrophic factor. Increasing concentrations of cerebrospinal fluid (10%, 20% and 30%) in the growth medium caused a decrease of neurotrophic factor secretion. Results indicated co-culture of human embryonic olfactory ensheathing cells, human Schwann cells, human amniotic epithelial cells and human vascular endothelial cells improved the expression of nerve growth factor, brain-derived neurotrophic factor, and glial cell line-derived neurotrophic factor. The reduction of cerebrospinal fluid extravasation at the transplant site after spinal cord injury is beneficial for the survival and secretion of neurotrophic factors from transplanted cells.
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Affiliation(s)
- Sanjiang Feng
- Department of Neurosurgery, First Affiliated Hospital of Shantou University Medical College, Shantou 515041, Guangdong Province, China
| | - Minghua Zhuang
- Department of Neurosurgery, First Affiliated Hospital of Shantou University Medical College, Shantou 515041, Guangdong Province, China
- Corresponding author: Minghua Zhuang, Professor, Chief physician, Department of Neurosurgery, First Affiliated Hospital of Shantou University Medical College, Shantou 515041, Guangdong Province, China . (N20110403001/WJ)
| | - Rui Wu
- Department of Hematology, Second Affiliated Hospital of Shantou University Medical College, Shantou 515041, Guangdong Province, China
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Tail nerve electrical stimulation combined with scar ablation and neural transplantation promotes locomotor recovery in rats with chronically contused spinal cord. Brain Res 2012; 1456:22-35. [DOI: 10.1016/j.brainres.2012.03.054] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Revised: 03/20/2012] [Accepted: 03/21/2012] [Indexed: 01/28/2023]
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12
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Cograft of neural stem cells and schwann cells overexpressing TrkC and neurotrophin-3 respectively after rat spinal cord transection. Biomaterials 2011; 32:7454-68. [DOI: 10.1016/j.biomaterials.2011.06.036] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Accepted: 06/14/2011] [Indexed: 01/20/2023]
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13
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Zhang SX, Huang F, Gates M, Holmberg EG. Scar ablation combined with LP/OEC transplantation promotes anatomical recovery and P0-positive myelination in chronically contused spinal cord of rats. Brain Res 2011; 1399:1-14. [DOI: 10.1016/j.brainres.2011.05.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Revised: 04/30/2011] [Accepted: 05/02/2011] [Indexed: 01/27/2023]
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14
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Tetzlaff W, Okon EB, Karimi-Abdolrezaee S, Hill CE, Sparling JS, Plemel JR, Plunet WT, Tsai EC, Baptiste D, Smithson LJ, Kawaja MD, Fehlings MG, Kwon BK. A systematic review of cellular transplantation therapies for spinal cord injury. J Neurotrauma 2010; 28:1611-82. [PMID: 20146557 DOI: 10.1089/neu.2009.1177] [Citation(s) in RCA: 427] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Cell transplantation therapies have become a major focus in pre-clinical research as a promising strategy for the treatment of spinal cord injury (SCI). In this article, we systematically review the available pre-clinical literature on the most commonly used cell types in order to assess the body of evidence that may support their translation to human SCI patients. These cell types include Schwann cells, olfactory ensheathing glial cells, embryonic and adult neural stem/progenitor cells, fate-restricted neural/glial precursor cells, and bone-marrow stromal cells. Studies were included for review only if they described the transplantation of the cell substrate into an in-vivo model of traumatic SCI, induced either bluntly or sharply. Using these inclusion criteria, 162 studies were identified and reviewed in detail, emphasizing their behavioral effects (although not limiting the scope of the discussion to behavioral effects alone). Significant differences between cells of the same "type" exist based on the species and age of donor, as well as culture conditions and mode of delivery. Many of these studies used cell transplantations in combination with other strategies. The systematic review makes it very apparent that cells derived from rodent sources have been the most extensively studied, while only 19 studies reported the transplantation of human cells, nine of which utilized bone-marrow stromal cells. Similarly, the vast majority of studies have been conducted in rodent models of injury, and few studies have investigated cell transplantation in larger mammals or primates. With respect to the timing of intervention, nearly all of the studies reviewed were conducted with transplantations occurring subacutely and acutely, while chronic treatments were rare and often failed to yield functional benefits.
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Affiliation(s)
- Wolfram Tetzlaff
- University of British Columbia, ICORD, Vancouver, British Columbia, Canada.
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Zhang YQ, Zeng X, He LM, Ding Y, Li Y, Zeng YS. NT-3 gene modified Schwann cells promote TrkC gene modified mesenchymal stem cells to differentiate into neuron-like cells in vitro. Anat Sci Int 2009; 85:61-7. [DOI: 10.1007/s12565-009-0056-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2009] [Accepted: 07/03/2009] [Indexed: 01/01/2023]
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16
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Abstract
We investigated the influence of the bifunctional guidance molecule netrin-1 on axonal growth in the injured adult spinal cord. In the adult, netrin-1 is expressed on mature oligodendrocytes, cells of the central canal, and the meninges. Netrin-1 protein in white matter is selectively enriched adjacent to paranodal loops of myelin in nodes of Ranvier. The repulsion-mediating netrin-1 uncoordinated-5 (UNC5) receptors are expressed by neurons of the corticospinal and rubrospinal projections, and by intrinsic neurons of the spinal cord, both before and after spinal cord injury. Neutralization of netrin-1 in myelin prepared from adult rat spinal cord using UNC5 receptor bodies increases neurite outgrowth from UNC5-expressing spinal motor neurons in vitro. Furthermore, axon regeneration is inhibited in a netrin-1-enriched zone, devoid of other myelin-associated inhibitors, within spinal cord lesion sites in vivo. We conclude that netrin-1 is a novel oligodendrocyte-associated inhibitor that can contribute to axonal growth failure after adult spinal cord injury.
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17
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Biernaskie J, Sparling JS, Liu J, Shannon CP, Plemel JR, Xie Y, Miller FD, Tetzlaff W. Skin-derived precursors generate myelinating Schwann cells that promote remyelination and functional recovery after contusion spinal cord injury. J Neurosci 2007; 27:9545-59. [PMID: 17804616 PMCID: PMC6672973 DOI: 10.1523/jneurosci.1930-07.2007] [Citation(s) in RCA: 238] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Transplantation of exogenous cells is one approach to spinal cord repair that could potentially enhance the growth and myelination of endogenous axons. Here, we asked whether skin-derived precursors (SKPs), a neural crest-like precursor that can be isolated and expanded from mammalian skin, could be used to repair the injured rat spinal cord. To ask this question, we isolated and expanded genetically tagged murine SKPs and either transplanted them directly into the contused rat spinal cord or differentiated them into Schwann cells (SCs), and performed similar transplantations with the isolated, expanded SKP-derived SCs. Neuroanatomical analysis of these transplants 12 weeks after transplantation revealed that both cell types survived well within the injured spinal cord, reduced the size of the contusion cavity, myelinated endogenous host axons, and recruited endogenous SCs into the injured cord. However, SKP-derived SCs also provided a bridge across the lesion site, increased the size of the spared tissue rim, myelinated spared axons within the tissue rim, reduced reactive gliosis, and provided an environment that was highly conducive to axonal growth. Importantly, SKP-derived SCs provided enhanced locomotor recovery relative to both SKPs and forebrain subventricular zone neurospheres, and had no impact on mechanical or heat sensitivity thresholds. Thus, SKP-derived SCs provide an accessible, potentially autologous source of cells for transplantation into and treatment of the injured spinal cord.
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Affiliation(s)
- Jeff Biernaskie
- Developmental and Stem Cell Biology Group, Hospital for Sick Children, and
| | - Joseph S. Sparling
- International Collaboration on Repair Discoveries, and
- Departments of Zoology and
| | - Jie Liu
- International Collaboration on Repair Discoveries, and
- Departments of Zoology and
| | - Casey P. Shannon
- International Collaboration on Repair Discoveries, and
- Departments of Zoology and
| | - Jason R. Plemel
- International Collaboration on Repair Discoveries, and
- Departments of Zoology and
| | - Yuanyun Xie
- International Collaboration on Repair Discoveries, and
- Departments of Zoology and
| | - Freda D. Miller
- Developmental and Stem Cell Biology Group, Hospital for Sick Children, and
- Departments of Molecular and Medical Genetics and
- Physiology, University of Toronto, Toronto, Ontario, Canada M5G 1L7, and
| | - Wolfram Tetzlaff
- International Collaboration on Repair Discoveries, and
- Departments of Zoology and
- Surgery, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
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18
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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.
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Affiliation(s)
- Paul Dinh
- University of California, Irvine, CA, USA
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19
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Oudega M. Schwann cell and olfactory ensheathing cell implantation for repair of the contused spinal cord. Acta Physiol (Oxf) 2007; 189:181-9. [PMID: 17250568 DOI: 10.1111/j.1748-1716.2006.01658.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A contusion injury to the spinal cord results in impaired neurological functions due to neuronal death, and axonal damage and demyelination. In time, a fluid-filled cyst forms at the site of the initial impact. There are no effective endogenous repair mechanisms and, consequently, injury-induced functional deficits are permanent. One aspect of spinal cord repair is that severed descending and ascending axons need to regenerate beyond the site of injury towards the denervated spinal regions where they can become part of axonal circuits involved in motor and sensory function. Implantation of cells into the injured cord has been studied extensively as a means to promote axonal regeneration in the injured spinal cord. Depending on the overall damage, different cell types may be appropriate in different types of injury. To accomplish axonal regeneration in the contused spinal cord, the strengths and limitations of two glial cell types in particular will be discussed; Schwann cells and olfactory ensheathing cells. It is known that with these implants, axonal regeneration is frustrated by the presence of a glial scar surrounding the contused area. I will review current approaches aimed at overcoming this axonal growth inhibitory scar. Future studies need to focus on identifying interventions that, in combination with cellular implants, will elicit substantial axonal growth beyond the contusion injury, which may then be the basis for biologically significant functional recovery.
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Affiliation(s)
- M Oudega
- International Center for Spinal Cord Injury, Kennedy Krieger Institute and the Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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20
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Rasouli A, Bhatia N, Suryadevara S, Cahill K, Gupta R. Transplantation of preconditioned schwann cells in peripheral nerve grafts after contusion in the adult spinal cord. Improvement of recovery in a rat model. J Bone Joint Surg Am 2006; 88:2400-10. [PMID: 17079397 DOI: 10.2106/jbjs.e.01424] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND Recovery after injury to the peripheral nervous system is based on the pro-regenerative relationship between axons and the extracellular matrix, a relationship established by Schwann cells. As mechanical conditioning of Schwann cells has been shown to stimulate their regenerative behavior, we sought to determine whether transplantation of these cells to the central nervous system (i.e., the spinal cord), with its limited regenerative capacity after injury, would improve axonal regeneration and functional recovery. METHODS A moderate contusion injury of the spinal cord was created with a force-directed impactor in forty-eight adult Sprague-Dawley rats, and, at one week postinjury, the spinal cords were reexposed in all animals. In twenty-four of these animals, peripheral nerve grafts with Schwann cells that had been obtained from the sciatic nerves of donor animals, and had been either untreated or subjected to mechanical conditioning, were transplanted to the contused area of the cords following resection of the glial scar. Another group of animals was treated with glial scar excision only, and a fourth group had the contusion injury but neither glial excision nor transplantation. Scores according to the Basso, Beattie, Bresnahan (BBB) Locomotor Rating Scale were assigned preoperatively and weekly thereafter. Tract tracing of descending and ascending spinal cord tracts was performed at six weeks postoperatively for quantitative histological evaluation of axonal regeneration. RESULTS While the recovery following glial scar excision without peripheral nerve transplantation was significantly worse than the recovery in the other groups, both transplantation groups had significantly higher BBB scores than the controls (no transplantation) in the early postoperative period (p < 0.05). Moreover, histological analysis showed markedly increased axonal regeneration at the lesional sites in the animals treated with the mechanically conditioned grafts than in the other groups (p < 0.05). CONCLUSIONS Functional recovery after spinal cord contusion improved following glial scar excision with transplantation of Schwann cells in peripheral nerve grafts to the contusion areas. Although recovery did not differ significantly between the transplantation groups, only the preconditioned grafts led to axonal regeneration at and past the lesional site. These grafts may further enhance functional recovery as the descending tracts eventually reach their target end-organs.
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Affiliation(s)
- Alexandre Rasouli
- University of California, Irvine, 2226 Gillespie Neuroscience Research Facility, Irvine, CA 92697, USA
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21
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Nomura H, Katayama Y, Shoichet MS, Tator CH. COMPLETE SPINAL CORD TRANSECTION TREATEDBY IMPLANTATION OF A REINFORCED SYNTHETIC HYDROGEL CHANNEL RESULTS IN SYRINGOMYELIA AND CAUDAL MIGRATION OF THE ROSTRAL STUMP. Neurosurgery 2006. [DOI: 10.1227/01.neu.0000243297.69189.f8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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22
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Nomura H, Katayama Y, Shoichet MS, Tator CH. Complete Spinal Cord Transection Treatedby Implantation of a Reinforced Synthetic Hydrogel Channel Results in Syringomyelia and Caudal Migration of the Rostral Stump. Neurosurgery 2006; 59:183-92; discussion 183-92. [PMID: 16823315 DOI: 10.1227/01.neu.0000219859.35349.ef] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
OBJECTIVE Previously, we reported that synthetic poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) (PHEMA-MMA) channels promoted regeneration of a small number of axons from brainstem motor nuclei yet provided limited functional recovery after complete spinal cord transection at T8 in rats. However, we found that these modulus channels partially collapsed over time. Therefore, we synthesized coil-reinforced PHEMA or PHEMA-MMA channels with greater elastic moduli and introduced a new spinal fixation technique to prevent collapse. We also assessed axonal regeneration within the new channels containing a cocktail of autologous peripheral nerve grafts, fibrin matrix, and acidic fibroblast growth factor. METHODS After spinal cord transection, rats were divided into six groups: Groups 1 and 2 had either a PHEMA or PHEMA-MMA reinforced channel implanted between the stumps of the transected spinal cord with the cocktail; Groups 3 and 4 had either an unfilled reinforced PHEMA or PHEMA-MMA channel similarly implanted; Group 5 had an spinal cord transection without channel implanted, and Group 6 underwent the identical procedure to Group 1, but rats were sacrificed by 8 weeks for early histological assessment. Groups 1 to 5 were sacrificed at 18 weeks. RESULTS There was no channel collapse at any time. However, there was no improvement in axonal regeneration or functional recovery among Groups 1 to 4 because of the unexpected development of syringomyelia and caudal migration of the rostral stump. Functional recovery was better in Groups 1 to 4 compared with Group 5 (P < 0.05). CONCLUSION The use of channels to enhance regeneration of axons is promising; however, improvement of the design of the channels is required.
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Affiliation(s)
- Hiroshi Nomura
- Toronto Western Research Institute, Toronto Western Hospital,Toronto, Canada
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23
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Seledtsov VI, Rabinovich SS, Parlyuk OV, Kafanova MY, Astrakov SV, Seledtsova GV, Samarin DM, Poveschenko OV. Cell transplantation therapy in re-animating severely head-injured patients. Biomed Pharmacother 2005; 59:415-20. [PMID: 16084057 DOI: 10.1016/j.biopha.2005.01.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2005] [Accepted: 01/31/2005] [Indexed: 12/16/2022] Open
Abstract
The results of controlled, retrospective clinical investigation of applying cell transplantation (CT) therapy in 38 severely head-injured patients are presented. The patients initially were in state of coma (Glasgow coma scale score 3--7), owing to their traumatic brain injuries. Cells prepared from fetal nervous and hematopoietic tissues were grafted subarachnoidally via lumbar puncture. The control group consisted of 38 patients and was clinically comparable with the trial one. From the results obtained it appears that CT treatment promoted both wakening consciousness of the patients and their following neurological rehabilitation. A death-rate in the trial and control group was 5% (two cases) and 45% (17 cases), respectively. According to a Glasgow scale, favorable (good+satisfactory) outcomes of a disease were noted in 33 (87%) cell-grafted and only in 15 (39%) control patients. Statistical analysis revealed that CT treatment generally improved the outcomes by 2.5-fold. No serious complications of CT therapy were noted. The results point out a possible rationality of applying CT therapy in severely head-injured patients as early as within acute period of a disease.
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Affiliation(s)
- Victor I Seledtsov
- Immunohematologic Department, Institute of Clinical Immunology, Russian Academy of Medical Sciences, 14 Yadrintsevskaya Street, 630099 Novosibirsk, Russia.
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24
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Abstract
The complex nature of spinal cord injury appears to demand a multifactorial repair strategy. One of the components that will likely be included is an implant that will fill the area of lost nervous tissue and provide a growth substrate for injured axons. Here we will discuss the role of Schwann cells (SCs) in cell-based, surgical repair strategies of the injured adult spinal cord. We will review key studies that showed that intraspinal SC grafts limit injury-induced tissue loss and promote axonal regeneration and myelination, and that this response can be improved by adding neurotrophic factors or anti-inflammatory agents. These results will be compared with several other approaches to the repair of the spinal cord. A general concern with repair strategies is the limited functional recovery, which is in large part due to the failure of axons to grow across the scar tissue at the distal graft-spinal cord interface. Consequently, new synaptic connections with spinal neurons involved in motor function are not formed. We will highlight repair approaches that did result in growth across the scar and discuss the necessity for more studies involving larger, clinically relevant types of injuries, addressing this specific issue. Finally, this review will reflect on the prospect of SCs for repair strategies in the clinic.
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Affiliation(s)
- M Oudega
- The Miami Project to Cure Paralysis, School of Medicine, University of Miami, Miami, FL 33136, USA.
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25
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Ramer LM, Ramer MS, Steeves JD. Setting the stage for functional repair of spinal cord injuries: a cast of thousands. Spinal Cord 2005; 43:134-61. [PMID: 15672094 DOI: 10.1038/sj.sc.3101715] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Here we review mechanisms and molecules that necessitate protection and oppose axonal growth in the injured spinal cord, representing not only a cast of villains but also a company of therapeutic targets, many of which have yet to be fully exploited. We next discuss recent progress in the fields of bridging, overcoming conduction block and rehabilitation after spinal cord injury (SCI), where several treatments in each category have entered the spotlight, and some are being tested clinically. Finally, studies that combine treatments targeting different aspects of SCI are reviewed. Although experiments applying some treatments in combination have been completed, auditions for each part in the much-sought combination therapy are ongoing, and performers must demonstrate robust anatomical regeneration and/or significant return of function in animal models before being considered for a lead role.
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Affiliation(s)
- L M Ramer
- ICORD (International Collaboration on Repair Discoveries), The University of British Columbia, Vancouver, BC, Canada
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